Section Seven. Intravenous Regional Blocks for the Upper & Lower Extremity

The technique of intravenous regional anesthesia (IVRA) was first introduced by August Bier in 1908.1 Bier block essentially consists of injecting local anesthetic solutions into the venous system of an upper or lower extremity that has been exsanguinated by compression or gravity and that has been isolated by means of a tourniquet from the central circulation. In Dr. Bier's original technique, the local anesthetic procaine in concentrations of 0.25% to 0.5% was injected through an intravenous cannula, which had been placed between two Esmarch bandages utilized as tourniquets to divide the arm into proximal and distal compartments.2–4 After injecting the local anesthetic, Dr. Bier noted two distinct types of anesthesia; an almost immediate onset of “direct” anesthesia between the two tourniquets, and then, after a delay of 5 to 7 min, an “indirect” anesthesia distal to the distally placed tourniquet. By performing dissections of the venous system of the upper extremity in cadavers after injecting methylene blue, Bier was able to determine that the direct anesthesia was the result of local anesthesia bathing bare nerve endings in the tissues, whereas the indirect anesthesia was most probably due to local anesthesia being transported to the substance of the nerves via the vasa nervorum, where a typical conduction block occurs. Dr. Bier's conclusion was that two mechanisms of anesthesia were associated with his technique: peripheral infiltration block and conduction block. The technique, as originally described by Dr. Bier, remains essentially unchanged in modern practice for the past 95 years, except for the introduction of the double-tourniquet preparation used in current clinical practice5–7 (Figure 41–1).

Bier block can be used for brief surgical procedures or manipulations of the upper or lower extremity. However, the technique found its greatest acceptance for use for the upper extremity because tourniquet problems and other safety issues seem to arise more frequently when IVRA is used on the lower extremities. Bier block is also a procedure that has found utility as a treatment adjunct for patients suffering from complex regional pain syndromes (CRPS) (formerly know as reflex sympathetic dystrophy, or sympathetically maintained pain) as an alternative to repeated sympathetic blocks. In this regard, IVRA has been shown to decrease neurogenic inflammation, a phenomenon possibly associated with CRPS, with little impairment of sensory function, at least when mepivacaine is the local anesthetic chosen for the block. Sensibility to cold is significantly decreased 10 and 30 min after the block, even with a reduction in the skin temperature on the blocked side.8 Chemical sympathectomy using IVRA with agents such as guanethidine or bretylium may last up to 5 days, as compared with local anesthetic blocks, which typically provide analgesia lasting only several hours. Quantitative sensory testing before and after such blocks has demonstrated that it is possible to predict which patients will have long-lasting pain alleviation using IVRA guanethidine blocks following traumatic injury or surgery.9

Although IVRA is a safe and effective method of administering local anesthetics for extremity block both for surgery and for pain control, one recent large survey noted that most third-year (CA-3) anesthesia residents had performed fewer than 10 such blocks during the entire course of their training.10

The only relevant anatomy is the location and distribution of the veins of the hand, antecubital fossa, and of the foot and ankle region.

Upper Extremity

IVRA is appropriate for surgeries and manipulations of the extremities requiring anesthesia of up to an hour's duration. It is most suited for peripheral, soft-tissue operations such as ganglionectomies, carpal tunnel release, Dupuytren's contractures, or reduction of fractures. However, the necessity of exsanguinating the extremity using an Esmarch bandage, a potentially painful maneuver, may preclude certain procedures from being undertaken with this technique (see Figures 41–5, 41–6, and 41–10). Likewise, manipulations of the ulnar, median, or radial nerves may cause paresthesias, which may require the use of analgesics or sedatives. A novel use of IVRA is for anesthetizing the hand prior to injecting botulinum toxin A (BTX-A) for the treatment of hyperhidrosis. BTX-A significantly reduces sweat production, as measured by Minor's test and as quantified by corneometer analysis, but the injection is painful unless the hand is anesthetized beforehand; IVRA has been found to be very suitable for this purpose.11 IVRA of the upper extremity has been occasionally utilized for prolonged analgesia/anesthesia, with a mandatory tourniquet deflation period of at least 1 min prior to reestablishing the anesthetized state.12

Lower Extremity

IVRA may be used for brief surgical interventions of the lower extremity in a manner analogous to that described earlier for upper extremity surgery. Surgical procedures that may be completed using this approach include excision of a mass, digital nerve repair, phalangeal fracture/dislocation surgery, and accessory navicular excision. Any foot, ankle, or distal lower extremity orthopedic procedure requiring approximately 45 min or less may be amenable to this modality. Although IVRA has been associated with an increased incidence of compartment syndrome when treating tibial shaft fractures, and has therefore been deemed contraindicated in such cases, a recent study in volunteers showed no significant difference in tissue pressures before and after tourniquet inflation regardless of the volume of saline used (≤1.5 mL/kg) or as a function of time following saline injection during tourniquet inflation. The authors concluded that in the normal atraumatic limb, simulated IVRA using normal saline (NS) does not increase tissue pressure within the anterior compartment of the leg.13

Pediatrics

IVRA has been an acceptable choice in selected pediatric patients for the reduction of fractures of the upper extremity. One large study of 470 children ages 2–19 years found that IVRA was adequate for fracture reduction in 99% (467 total). No complications were noted. The technique was only aborted in three children due to failure to gain peripheral venous access.15 However, the technique of IVRA was found not to be superior to administration of nitrous oxide for the same purpose in a smaller sample of 28 children. Additionally, the nitrous oxide use was more rapidly applicable and dissipated more readily.16

The only absolute contraindication to IVRA is patient refusal. Relative contraindications include:

• Crush injuries of an extremity
• Inability to locate peripheral veins
• Local skin infections
• Cellulitis
• Compound fractures
• Patients with convincing history of allergy to local anesthetics
• Patients with severe vascular injuries to the extremity
• Preexisting vascular arteriovenous shunts and patients in whom a tourniquet is unsuitable (ie, patients with severe peripheral vascular disease)

(Figures 41-1, 41-2, 41-3, 41-4, 41-5, 41-6, 41-7, 41-8, 41-9, 41-10, and 41-11)

1. 1. Local anesthetic agents: Lidocaine HCl, 0.25–0.5% (alternative is prilocaine, 0.5%)

2. 2. One rubber tourniquet (Penrose drain) 12–18 in. in length (30–45 cm) and ⅞ in. wide (2.3 cm) for use prior to placing the intravenous cannula (see Figures 41–7 and 41–11)

3. 3. One 18- or 20-gauge intravenous (IV) extracatheter (catheter-over-needle) (see Figures 41–2 and 41–11)

4. 4. One 500-mL or 1-L bag of IV solution connected to an infusion set (vs a Hep-Lock) to be connected to the IV cannula to maintain its patency until the anesthetic solution is injected in the isolated extremity (may substitute a saline-flushed IV port instead)

5. 5. Standard American Society of Anesthesiologists (ASA) monitors (electrocardiograph, blood pressure, pulse oximeter)

6. 6. Resuscitation equipment (IV catheter, crystalloid solution, and infusion set for the contralateral upper extremity) (for upper extremity IVRA)

7. 7. A functional IV catheter, crystalloid solution, and infusion set for the contralateral upper extremity

8. 8. Two pneumatic tourniquets of appropriate size for the selected extremity (see Figures 41–1, 41–3, 41–4, 41–5, 41–6, 41–9, and 41–10)

9. 9. One Esmarch bandage 60 in. in length (152 cm) and 4 in. wide (10 cm) for exsanguinating the arm (see Figures 41–5, 41–6, and 41–10)

10. 10. Sterile skin preparatory set

11. 11. Fifty-milliliter Luer-Lok syringe (see Figures 41–7 and 41–11)

12. 12. One graduated measuring cup for the mixing of solution, preferably with a 100-mL capacity

13. 13. Adhesive tape; various sizes

The patient lies in the dorsal recumbent position or in any other position as long as the vein selected for placement is readily accessible. The resuscitative equipment is checked, and the pneumatic tourniquets are tested and prepared for use. For surgery on the elbow, the needle will be placed in the forearm or antecubital fossa. For procedures on the hand or forearm, a vein on the dorsum of the hand is best selected (see Figure 41–2).

For lower extremity procedures, a vein in the foot, ankle, or lower leg is chosen (see Figure 41–11). After obtaining intravenous access in a nonoperated extremity (alternatively, a central venous access may be secured), a full complement of ASA monitors is applied and baseline vital signs are assessed. If the patient is in severe pain, small aliquots of IV analgesics may now be administered (ie, fentanyl 1–2 mcg/kg) to facilitate the exsanguination process. Since total patient cooperation is not essential to be successful, small doses of a water-soluble benzodiazepine (ie, midazolam 15–25 mcg/kg) may alternatively be administered for anxiolysis. An important benefit to choosing a benzodiazepine is the suppression of the convulsant response associated with local anesthetic toxicity, a valid concern in the patient undergoing IVRA due to the large volume of agent being directly administered into the vascular system.

Upper Extremity IVRA

The following is the technique of IVRA for upper extremity procedures as previously taught at Cook County Hospital by Alon P. Winnie, MD.

1. 1. A double pneumatic tourniquet is placed on the proximal cuff high on the upper arm (see Figures 41-3, 41-4, 41-5, and 41-6)

2. 2. An indwelling plastic extracatheter is inserted into a peripheral vein as far distally as feasible.

3. 3. The entire arm is elevated, and a rubber Esmarch bandage is wound around the arm spirally from the hand to the distal cuff of the double tourniquet to exsanguinate the arm (see Figures 41–5 and 41–6).

4. 4. The axillary artery is digitally occluded, and while pressure is maintained on it, the proximal pneumatic cuff is inflated to 50–100 mm Hg above the systolic arterial blood pressure, after which time the Esmarch bandage is removed.

5. 5. Following inflation of the proximal cuff and removal of the Esmarch bandage, 30–50 mL of 0.5% lidocaine HCl is injected via the indwelling plastic catheter, the volume depending on the size of the arm being anesthetized (see Figure 41–7).

6. 6. After injection of the local anesthetic, the arm is brought down to the level of the procedure table, the IV cannula in the surgical extremity is withdrawn, and pressure is quickly applied over the site using sterile povidone–iodine (Betadine)-soaked sponges (see Figure 41–8).

7. 7. About 25–30 min after the onset of anesthesia or when a patient complains of tourniquet pain, the distal cuff is inflated and the proximal cuff is deflated, to minimize the development of tourniquet pain.

Lower Extremity IVRA

The only significant difference is that the IVRA technique for the lower extremity requires relatively larger volume of local anesthetic. This is necessary to more completely fill the larger vascular compartment of the lower extremity from the distally placed IV cannula to the proximal tourniquet (100 mL vs 50 mL) (see Figures 41-9, 41-10, and 41-11).

Local Anesthetic Considerations

Lidocaine is the prototypical local anesthetic used for IVRA in the United States. In Europe, however, prilocaine has been the subject of most clinical trials to date. Attempts have been made to maximize the efficacy of lidocaine, while minimizing side effects or toxicity of the agent. Alkalinization of 0.5% lidocaine (using 1.4% sodium bicarbonate) for IVRA was studied in 31 patients. The authors found no clinical advantage to the practice of alkalinization of lidocaine with respect to sensory block, motor block, or the appearance of postoperative pain.22 When lidocaine was compared with alkalinized and nonalkalinized 2-chloroprocaine, both used as 0.5% concentrations and used for hand surgery, alkalinized chloroprocaine behaved similarly to lidocaine, but plain chloroprocaine offered no benefit and produced more minor side effects than seen with lidocaine.23 Lidocaine has been compared with ropivacaine for upper extremity IVRA in two separate studies. Two doses of ropivacaine (1.2 and 1.8 mg/kg) were compared with one dose of lidocaine (3.0 mg/kg) in 15 volunteers. Recovery of sensory and motor block after tourniquet release was slowest with the high-dose ropivacaine group. More patients in the lidocaine group (5 out of 5) experienced light-headedness following tourniquet release, vs only 1 in the high-dose ropivacaine group.24 In the second study, 51 patients were randomized to receive either ropivacaine 0.375% or lidocaine 0.5% in a volume of 0.4 mL/kg up to 25 mL. Postoperative analgesia as measured by first request for analgesics was superior in the ropivacaine group.25

Prilocaine has been compared with lidocaine, as well as with other local anesthetics used for IVRA. Forty milliters of 0.5% prilocaine (100 mg) was compared with the same volume and same concentration of chloroprocaine in 10 volunteers undergoing IVRA, while evaluating onset of sensory and motor block. Motor block onset did not differ between groups, and sensation recovered almost equally well. However, recovery of motor function was shorter in the prilocaine group, and more chloroprocaine patients demonstrated signs of venous irritation or antecubital urticaria for 30–45 min after tourniquet deflation. Heart rate changes were also more notable in the chloroprocaine group.26 The same group of investigators expanded their study to include 60 patients; 30 in each of the two respective groups detailed earlier. Now, the investigators found that complete recovery of sensory block was faster in the prilocaine group (7.1 vs 9.8 min). Otherwise, the incidence of side effects remained higher in the chloroprocaine group.27 Next, these investigators compared 0.5% prilocaine with the same concentration of articaine (a newer amino amide–type local anesthetic that contains thiophene and that is pharmacologically similar to mepivacaine) for upper extremity IVRA. Articaine, a potent local anesthetic with a low degree of toxicity by virtue of its rapid metabolism with esterases, was felt to be a suitable alternative to prilocaine. Ten volunteers participated in this double-blinded, crossover comparison of the two agents. They found no significant difference between the two with respect to onset of anesthesia or motor block, or in recovery of sensory or motor function. However, 80% of the subjects experienced skin rashes after receiving articaine, vs 20% in the prilocaine group.28 When 0.5% prilocaine was compared with the same concentrations of articaine or lidocaine in three groups of 10 patients each for IVRA, it was found that the onset of sensory block was significantly shorter in the articaine group, which also had the lowest peak plasma concentrations of local anesthetic following tourniquet release.29 Plain prilocaine 1% has been compared with the same local anesthetic combined with four different additives for IVRA; bupivacaine 0.25%, clonidine 150 mcg, sufentanil 25 mcg, or tenoxicam 20 mg. The sufentanil-added group demonstrated the most rapid onset of sensory block; postoperative pain scores were improved by adding either clonidine or tenoxicam. Otherwise, there were no significant differences among the five groups with respect to onset and duration of sensory and motor block.30 Unlike the situation noted for lidocaine with the addition of bicarbonate as an adjuvant, the addition of bicarbonate to prilocaine does seem to shorten onset time and prolong the duration of anesthesia.31,32

The use of mepivacaine for IVRA has been studied. Sixteen patients were evaluated using 1.4 mg/kg in 40 mL for IVRA vs saline IVRA blocks performed in the same individuals on the contralateral arm. Arterial occlusion was maintained for 20 min. Reactive hyperemia was attenuated in the mepivacaine-treated arm for the 60-min evaluation period, indicating that mepivacaine is a potent vasoconstrictor of long duration of action. This finding has implications for the use of mepivacaine in individuals with either compromised upper extremity blood flow, or in those suffering from CRPS, wherein it probably should not be considered the local anesthetic of choice.33 The same study group evaluated the effects of mepivacaine IVRA on intracutaneous capsaicin-induced burning pain and on microvascular skin blood flow as measured by Doppler perfusion imaging. The reactive hyperemia was less in the mepivacaine-treated arm 10 min after tourniquet release, and the area of the flare was smaller after capsaicin in the mepivacaine-treated arms. The authors concluded that mepivacaine IVRA had no effect on post-IVRA sensory function of thin afferents, but differentially decreased the spread of capsaicin-induced flare.34

Adjuncts to Local Anesthetics for IVRA

A systematic review of the literature was undertaken to evaluate the use of adjuncts to local anesthetics for IVRA. Twenty-nine studies met the criteria of being randomized, double-blinded, and controlled. Data on 1217 study subjects were reviewed, and the agents studied included opioids (fentanyl, sufentanil, meperidine, morphine), clonidine, muscle relaxants (atracurium, pancuronium, mivacurium), tramadol, nonsteroidal antiinflammatory agents (NSAIDs) (ketorolac, tenoxicam, acetylsalicylate), alkalinization using sodium bicarbonate, and the addition of potassium, and temperature alterations. The authors found solid evidence supporting the use of NSAIDs in general, and ketorolac in particular, for improving postoperative analgesia. Clonidine 1 mcg/kg also appeared to improve postoperative analgesia and prolong tourniquet tolerance. Opioids fared poorly when used for IVRA, with only meperidine in doses of ≥30 mg showing substantial postoperative benefit at the expense of postdeflation nausea, vomiting, and dizziness. Muscle relaxants improved postoperative motor block and were beneficial in fracture reduction in which muscular relaxation is imperative for good results.35

Alpha2-Agonists (Clonidine and Dexmedetomidine)

Clonidine has been added to both prilocaine and lidocaine as an adjunct to IVRA, both for surgery and for the management of CRPS. When 2 mcg/kg was added to prilocaine 0.5% in a randomized, double-blind fashion in 56 patients undergoing upper extremity surgery, there was no difference between groups regarding sensory or motor block onset or duration. The patients who had clonidine added had a significant reduction in arterial blood pressure after tourniquet release (24–48%), while heart rate remained unchanged. The authors concluded that clonidine was of limited benefit as an adjunct to IVRA local anesthetics.36 When a dose of 1 mcg/kg in a total volume of 50 mL of 0.5% lidocaine was used for lower extremity IVRA for patients suffering from CRPS, five of seven subjects obtained complete pain relief after four to six blocks. The remaining two study patients derived partial benefit from the blocks. There were no cases of significant hypotension, bradycardia, hypoxemia, or excessive sedation.37 The addition of clonidine to prilocaine did dramatically suppress tourniquet pain, but it did not alter postoperative pain following tourniquet deflation.38 Dexmedetomidine is approximately eight times more selective toward the α2-adrenoreceptors than is clonidine. As such, it has been used in IVRA to determine if it might advance some of the beneficial findings noted with the latter agent. Thirty patients undergoing hand surgery under IVRA received 0.5% lidocaine alone or lidocaine plus dexmedetomidine 0.5 mcg/kg. The dexmedetomidine group showed a more rapid onset of sensory and motor block, a prolonged sensory and motor block recovery, prolonged tolerance for the tourniquet, and improved quality of analgesia compared with the group that received local anesthetic only.39

Opioids

Since opiate receptors were discovered to exist in the peripheral nervous system40,41 and with the demonstration that opioids may produce effective, long-lasting analgesia when injected in conjunction with local anesthetics for brachial plexus block,42–46 several investigators have attempted to decrease the potential for toxicity from local-anesthetic-only IVRA by adding opioids to reduce the concentration of lidocaine. Although it has not been proven that the addition of fentanyl to lidocaine for IVRA results in improved analgesia while reducing the risks,47,48 the addition of fentanyl in 200-mcg doses to prilocaine 0.5% did result in more complete anesthesia than in patients who had 100 mcg added, or when plain prilocaine was used for IVRA. Postoperative nausea and central nervous system side effects were higher in the fentanyl-added groups vs those who received local anesthetic alone.49 Two other studies, however, found that the addition of opioids to prilocaine did not improve success with the technique.50,51 More research on the effects of the addition of opioids to prilocaine for IVRA may ultimately resolve this apparent discrepancy.

Some investigators have found that adding opioid and muscle relaxants to 0.25% lidocaine provides the same analgesia and muscular relaxation as that provided by 0.5% lidocaine alone, while reducing the likelihood of systemic toxicity. Adjuvants added to lidocaine have included fentanyl 50 mcg plus pancuronium 0.5 mg,52,53 fentanyl plus rocuronium,54 and fentanyl plus d-tubocurarine.55 In each case, the authors reported outstanding operating conditions, and since the lidocaine concentration was able to be reduced to 0.20%, the potential for systemic toxicity was at least halved.

When meperidine 0.25%, 40 mL (100 mg), was used as a solitary agent for IVRA, complete motor block was produced, just as effective as that produced by lidocaine. Motor block onset was as rapid or more rapid than sensory block onset in each of the 15 patients in this study group. However, when compared with plain lidocaine in this study, there was a higher incidence of dizziness, nausea, and pain at the injection site.56

Tramadol

Tramadol has been evaluated for use in IVRA of the upper extremity. Sixty volunteers divided into four groups of 15 patients each received IVRA with 40 mL of tramadol 0.25% (100 mg), 0.9% NS, lidocaine 0.5%, or lidocaine plus tramadol 0.25%. The onset and recovery of sensory and motor block was similar between the tramadol and NS-only groups. However, the addition of tramadol to lidocaine resulted in faster onset of sensory block at the expense of an increase in skin rash development and painful burning sensations at the injection site. The conclusion of the authors was that tramadol alone does not possess local anesthetic effects, but might modify the effect if added to a local anesthetic like lidocaine.57 In another study comparing 0.5% lidocaine with and without 50 mg of tramadol for upper extremity IVRA, the tramadol-added group experienced less tourniquet pain than the local-only group, but, as in the study mentioned earlier, there were several cases of skin urticaria in the tramadol group, but not in the lidocaine-only group.58 Tramadol (100 mg) added to lidocaine for IVRA for upper extremity anesthesia acted similarly to sufentanil (25 mcg) or clonidine (1 mcg/kg) added to the local anesthesia with respect to intraoperative hemodynamic data, time to recovery of sensory block, onset and recovery of motor block, sedation scores, and postoperative pain.59 In summary, tramadol is ineffective as a solo agent for IVRA, but may confer some advantage when added to lidocaine. This advantage, however, may be offset by the significant incidence of dermatologic side effects of tramadol given intravenously in an exsanguinated extremity.

Muscle Relaxants

A small dose of nondepolarizing muscle relaxant may be chosen as an adjunct to the local anesthetic administered for IVRA; however, since d-tubocurarine releases histamine even in judicious doses, it is probably best to avoid this agent altogether. Atracurium has been added to lidocaine in an effort to improve muscular relaxation during IVRA, particularly during the reduction of upper extremity fractures and dislocations. Adding 3 mg of atracurium to lidocaine for IVRA resulted in a decrease in the onset time of analgesia in the hand, but not at the tourniquet site. There was no added benefit to adding this agent, or adding alfentanil to lidocaine in the same study.60 A prior study using 2 mg of atracurium added to 40 mL of 0.5% lidocaine for IVRA for hand surgery in 40 patients randomized to one of two groups found that the addition of the atracurium provided a greater degree of muscular relaxation, easier reduction of fractures, and better operating conditions, as well as less pain after surgery.61

Neostigmine

Neostigmine has been suggested as a co-analgesic when used for epidural and intrathecal analgesia and anesthesia, but evidence of its benefit in the peripheral nervous system is controversial. In two studies, one using neostigmine added to lidocaine, and the other using the adjuvant added to prilocaine, there have been conflicting findings. When neostigmine (1 mg) was added to 0.5% lidocaine for IVRA in a study of 54 volunteers randomized into one of three study groups, it was found that the addition of the adjuvant provided no benefit in terms of analgesia or anesthesia compared with controls.62 When one-half the dose of neostigmine (0.5 mg) was added to prilocaine (3 mg/kg) for IVRA in 30 patients randomized to one of two treatment groups, it was found that the adjuvant group demonstrated shortened sensory and motor block onset times, prolonged sensory and motor block recovery times, improved quality of anesthesia, and prolonged time to first analgesic requirement vs the plain prilocaine group.63 It appears that these conflicting findings with neostigmine added to two distinct local anesthetics for IVRA will need to be confirmed by additional work incorporating larger patient sample sizes to resolve the apparent discrepancy in the two small studies mentioned earlier.

Nonsteroidal Antiinflammatory Agents

Other attempts to improve IVRA with lidocaine have included using NSAIDs like ketorolac64 to suppress tourniquet pain while enhancing postoperative analgesia. Although ketorolac has shown some efficacy, other NSAIDs have not fared as favorably. Ketorolac has been added to lidocaine for IVRA for the treatment of sympathetically mediated pain syndromes. In a retrospective review of 61 patients referred to a university pain center with a diagnosis of reflex sympathetic dystrophy (RSD) who all underwent IVRA with the combination of ketorolac-lidocaine, 26% (16/61) had a complete analgesic response to the block(s). Forty-three percent (26/61) had a partial response, and 31% had no response. The authors stated that the only symptom predicting failure was the presence of allodynia. However, allodynia is the hallmark of RSD, so one must wonder whether the clinicians correctly categorized the patients as being afflicted with RSD, vs an alternative diagnosis.65 When used for upper extremity surgery, ketorolac added to lidocaine for IVRA was shown to be safe and effective, and furthermore, using a forearm tourniquet instead of an upper arm tourniquet in this study demonstrated that the dose of both agents could be reduced by 50%, while also providing for prolonged sensory block and prolonged postoperative analgesia. Twenty milligrams of ketorolac was added to lidocaine 0.5% for the upper arm tourniquet group, and half the dose of both agents (by virtue of halving the volume administered of an equipotent concentration of both drugs) was used in the forearm tourniquet group.66

Another NSAID, tenoxicam, was added to prilocaine in one study of 45 total patients. A 20-mg dose of the NSAID was used in patients undergoing IVRA for reduction of Colles' fractures, with patients divided into three groups. One group received local anesthetic only, one received local plus tenoxicam, and one group had IVRA with local anesthetic only plus IV NSAID. In this last group, the tenoxicam (20 mg) was injected into the contralateral arm, opposite the IVRA procedure arm. The group receiving the NSAID added to the local had superior analgesia and lower pain scores than either of the other two groups of patients.67

Other Specific Agents: Corticosteroids

The antiinflammatory properties of steroids have been evaluated when these agents have been added to local anesthetics for IVRA in patients with rheumatoid arthritis (RA). In a randomized, double-blind, crossover, placebo-controlled study, 20 RA patients received either 50 mg methylprednisolone in mepivacaine 0.25% or mepivacaine plain for upper extremity IVRA. The other extremity received the opposite treatment. One week later, the same medications were injected into the contralateral extremities, respectively. Fifty percent of patients reported subjective improvement at 1 and 6 weeks; objective parameters like grip strength did not change until the 6-week evaluation, at which time a significant increase was noted, as was the reduction in grip diastasis and movement-invoked pain. This report suggests that corticosteroids administered by IVRA may provide sustained analgesia in certain RA sufferers.68 Steroid IVRA has also been used as adjunctive treatment of CRPS type I. Methylprednisolone (40 mg) was added to lidocaine for IVRA in a randomized, double-blinded, placebo-controlled fashion in 22 patients. Treatments were applied once per week, for up to three sessions of blocks. The investigators found no benefit in adding the steroid to the local with regard to improvement in pain severity or shortening the course of the disease.69

Specific IVRA Treatments for CRPS

Adrenergic blocking agents or antagonists, particularly those effective at the alpha receptor, have shown promise in the treatment of CRPS, particularly when these agents are used for IVRA. Other adrenergic adjuvants release and then subsequently prevent the reuptake of norepinephrine at the neurovascular junction. Their use in CRPS is intuitive, since the pathophysiology of the disease is suspected to include the alpha receptor and to be mediated by norepinephrine. However, there is significant controversy regarding this topic, particularly when current research is compared with the findings of studies conducted almost 40 years ago. Guanethidine, reserpine, and bretylium have all been evaluated for IVRA for CRPS. When 15 mg guanethidine was added to 0.5% prilocaine in a group of 57 patients with CRPS of the upper extremity and hand, the guanethidine was found not to be more effective than NS in treating allodynia and burning pain of CRPS, following distal radius fractures.70 These findings corroborated work done in a double-blind, randomized, multicenter study 7 years earlier. Sixty patients with RSD/causalgia received four IVRA blocks at 4-day intervals with either guanethidine or placebo in 0.5% lidocaine. Long-term, there was no difference noted between the placebo group and the guanethidine group, and only 35% of patients overall in all groups had a resolution of their pain problem.71 Bretylium has been used as well in CRPS. In a randomized, controlled trial, 0.5% lidocaine was compared with the same local anesthetic to which bretylium 1.5 mg/kg was added. A decrease in pain of ≥30% was considered significant. The bretylium-local group had pain relief for 20 ± 17.5 days, as opposed to the lidocaine-only group, wherein analgesia persisted for only 2.7 ± 3.7 days. The bretylium was far superior to the local anesthetic alone in treating CRPS in this study.72 IVRA with bretylium was utilized to demonstrate that a reduction in sympathetic tone to exercising forearm muscles would increase blood flow, reduce muscle acidosis, and attenuate reflex responses. IVRA with bretylium increased blood flow as well as oxygen consumption in the exercising forearm, although both venous potassium and hydrogen ion content were elevated during the exercise phase, implying that reflex effects are unaffected by bretylium block.73

Complications due to IV regional anesthesia may be classified either as drug- or equipment- (ie, tourniquet) related. Drug-related complications depend on the agents being administered directly into the vascular system, including local anesthetics and adjuvants. Equipment-related complications include all devices and techniques used to isolate the vascular space from the systemic circulation. Inadvertent deflation of the cuff, cuff failure, a sudden increase in venous pressure within the occluded tissue to a level higher than cuff pressure, and an intact interosseous circulation may all contribute to complications due to IVRA. Lidocaine is the most commonly utilized local anesthetic for IVRA and is therefore the agent about which most complications have been reported. Fortunately, lidocaine does not accumulate to any great extent at sodium channels at therapeutic plasma concentrations, and since it both rapidly binds to and dissociates from the channel, toxic accumulations of the drug at the channel is atypical.74,75 Excessive plasma concentrations of lidocaine, as are associated with IV boluses of large doses with a faulty tourniquet system, result in peripheral vasodilatation and diminished cardiac contractility, usually seen clinically as hypotension. The usual onset of IVRA using lidocaine in 0.5% concentrations is rapid (about 4.5 ± 0.3 min) and the termination of anesthesia once the tourniquet has been deflated is also quite rapid (5.8 ± 0.5 min).76 Usually, there are no signs or symptoms of cardiovascular or central nervous system toxicity if the tourniquet is deflated at least 30 min after the drug is injected into the venous system, although tinnitus has been noted at the 20- and 27-s postdeflation periods following standard inflation times.77 Although about 70% of the administered lidocaine dose remains within the tissues of the isolated limb after tourniquet deflation, the remaining 30% enters the systemic circulation during the ensuing 45 min.75 Much more drug is released from the tissues of the isolated limb into the circulation after tourniquet deflation if the limb is inadvertently exercised, emphasizing the importance of maintaining the previously anesthetized extremity quiescent for some time immediately following tourniquet deflation. The other commonly utilized local anesthetic used for IVRA, prilocaine, is associated with the formation of methemoglobin, which occurs about 4 to 8 h after its administration.74 Fortunately, significant methemoglobinemia has not been reported when prilocaine has been used for IVRA. Prilocaine (0.5%) administered for IVRA has an onset of analgesia of about 11 min (±6.8 min) and termination of analgesia following tourniquet deflation averages 7.2 min (±4.6 min).26 The use of this agent for IVRA appears to be extraordinarily safe. Indeed, in one survey of 45,000 prilocaine IVRA blocks, there were no serious side effects and no deaths from using this drug via this technique.78 In terms of effectiveness, prilocaine seems to be equivalent to lidocaine when used for IVRA.

When opioids are administered in combination with local anesthetics for IVRA in an attempt to prolong analgesia following cuff deflation, occasional side effects typically attributed to opioids administered systemically may be noted following cuff deflation. These include nausea, vomiting, and mild sedation.47,50 When neuromuscular blocking drugs are administered in conjunction with local anesthetics to improve surgical conditions in patients undergoing fracture reduction, there have been no reports of complications from these adjuvants.

Additionally, the tourniquet itself may be a source of complications since it may cause ischemic pain and discomfort. Systemic hypertension may result from prolonged tourniquet inflation that is sustained or prolonged. Equipment misuse or malfunction is an important, and avoidable, source of complications due to this technique. Even an intact, fully functional tourniquet may be associated with leakage of administered drugs from a supposedly isolated extremity into the systemic circulation.80,81 Lower limb IVRA has an almost 100% incidence of local anesthetic leakage from beneath the tourniquet, versus about a 25% incidence for upper extremity block.82 As a corollary to this leakage phenomenon, the use of IVRA for lower extremity analgesia has an associated high incidence of poor-quality block (almost 40% in one prospective study).83 Drug may leak past an apparently fully functioning cuff and gain access to the systemic circulation via the interosseous circulation, which is not affected by the occlusion of muscles, soft-tissues, and the accompanying vascular channels included therein. This factor has been recognized for almost 40 years, yet it does not appear to be significant in the production of complications due to IVRA.84 Tourniquet deflation after IVRA is associated with signs and symptoms of systemic local anesthetic toxicity, ranging from mild CNS-related events such as tinnitus and perioral numbness, to seizures, and finally, to devastating cardiovascular collapse. These correlate with local anesthetic concentrations in arterial blood, and not to venous concentrations.79,85 Another complication due to IVRA is tourniquet pain, which not uncommonly occurs if a double-pneumatic device is not utilized81 (see Figures 41–1 and 41–2). We recommend the use of such a tourniquet for any procedure performed using IVRA that is expected to last longer than 30 min. Even when such guidelines are followed, however, some investigators have reported untoward events occurring following tourniquet deflation after a “safe” time interval. A 47-year-old patient with a history of CRPS type I underwent an IVRA block with a combination of lidocaine and clonidine. The tourniquet was deflated after 60 min and within the ensuing 10 min, he developed partial complex seizures that were persistent.86

Very rare, isolated reports of neurologic complications, including damage to the median, ulnar, and musculocutaneous nerves, are associated with IVRA.87 The cause of such complications appears to be direct pressure of the tourniquet applied to these nerves, which subsequently exhibit histologic changes resembling crush injuries. It is recommended that tourniquet time not exceed 2 h, to reduce the likelihood of capillary and muscle damage secondary to tissue acidosis.87,88 Compartment syndrome may occur rarely following IVRA, especially when IVRA is used for reduction of long bone lower extremity fractures, and may be due both to the large volume of anesthetic injected to effect analgesia as well as to inadequate or incomplete exsanguination of the limb prior to performing the block.89,90 There is also a case report of this complication following inadvertent injection of hypertonic saline solution when local anesthetic was intended to be injected.91 A 33-year-old pregnant patient undergoing IVRA for endoscopic carpal tunnel release experienced a severe episode of phantom limb sensation after the injection of the local anesthetic. The symptoms resolved on dissipation of the IVRA.92 There is one report of the devastating necessity for amputation of the arm in a 28-year-old patient whose radial and ulnar arteries thrombosed following IVRA after a brief tourniquet occlusion time.93 Whether this resulted from unsuspected intraarterial injection of drug, a drug administration error, or perhaps an idiosyncratic drug reaction is purely speculative.

Local Anesthetic Toxicity

Although lidocaine is the most commonly utilized local anesthetic agent for IVRA in the United States, in Europe prilocaine 0.5% is more routinely chosen. Prilocaine, however, is metabolized to orthotoluidine, an oxidizing compound capable of converting hemoglobin to methemoglobin. This is usually only of concern when the dose of prilocaine exceeds 600 mg, which, even for lower extremity IVRA in which volumes as large as 100 mL are utilized, should not be attained (ie, 100 mL × 0.5% prilocaine = 500 mg). Deflation of the tourniquet after surgery is a critical step to minimizing the possibility of toxicity associated with IVRA. First, it is absolutely mandatory that the tourniquet not be deflated unless at least 3034 min has elapsed since the injection of the local anesthetic, even if the duration of surgery or of the manipulation has been very brief. If the surgery is very brief, and the patient needs to recover in a postanesthesia care unit (PACU), it is acceptable to clamp off the distal tourniquet while it is inflated, remove the patient from the operating area (with the tourniquet inflated), and transfer the patient to a monitored care setting. At no time should anyone remove the clamped tourniquet, however, until the 30-min period commencing with the injection of local anesthetic solution has elapsed. At such time, the patient should be continually monitored for at least 15 min following tourniquet unclamping in the PACU. At least one case of cardiac arrest has been reported when the tourniquet was released soon after the injection of local, where the duration of surgery was extremely short.94 Second, it is absolutely essential that the deflation of the tourniquet be accomplished in a “cyclical” fashion as follows: the cuff is deflated (after a minimum of 30 min) and is immediately reinflated. The patient is observed or questioned carefully for the occurrence of symptoms associated with local anesthetic toxicity, such as tinnitus, light-headedness, metallic taste in the mouth, etc. Obviously, signs of stimulation of the CNS may also represent local anesthetic toxicity and must be sought. If there are no such signs or symptoms after about 1 min, the cuff is once again deflated, and once again immediately reinflated for a period of about 1 to 2 min, with the patient being observed and queried for systemic local anesthetic toxicity. If none appear by this time, the tourniquet may be safely deflated and removed from the extremity. The safety of such cycled deflating/reinflating is that with each deflation, only a small fraction of the administered (and unbound) local anesthetic is allowed to enter the systemic circulation, minimizing the possibility of a sudden, sustained increase in the blood level of the local anesthetic.79

IVRA is a valuable adjunct to the armamentarium of clinicians in any specialty dealing with the acutely injured patient. The simplicity of the technique and the relative safety (if strict adherence to the previously listed protocol is maintained) make it an attractive alternative to brachial plexus block (for upper extremity surgery or manipulation) and spinal or epidural block (for lower extremity surgery or manipulation). Simply being able to identify and access a peripheral vein and apply a pneumatic tourniquet make this one of the most “user-friendly” regional block modalities in clinical practice. One of the only potential disadvantages associated with IVRA is the very finite duration of anesthesia/analgesia associated with its use. A relative inability to prolong analgesia long into the postprocedure period detracts from its utility. For those occasions, continuous catheter insertion and maintenance by way of plexus anesthesia surely offers an attractive alternative.

“Almost all cases of hernia, with the possible exception of those in young children, could undoubtedly be subjected to the radical operation under local anesthesia.” This quote by Harvey Cushing reported in the Annals of Surgery in 1900 illustrates that over 100 years ago the attributes of regional anesthesia for lower abdominal and inguinal surgery were appreciated. Ilioinguinal and iliohypogastric blocks are among the most frequently used regional blocks performed for these surgical procedures. Postherniorrhaphy pain is moderate to severe and often poorly controlled with opioids as single modal therapy.1 Ilioinguinal and iliohypogastric blocks have been shown to significantly reduce pain associated with herniorrhaphy, regardless of whether the blocks are used as the primary anesthetic2 or for pain control after general3,4 or spinal5 anesthesia.

Anatomy

Both the iliohypogastric and ilioinguinal nerves emanate from the first lumbar spinal root. Superomedial to the anterior superior iliac spine, the iliohypogastric and ilioinguinal nerves pierce the transversus abdominis to lie between it and the internal oblique muscles. After traveling a short distance inferomedially, their ventral rami pierce the internal oblique to lie between the internal and external oblique muscles before giving off branches, which pierce the external oblique to provide cutaneous sensation. The iliohypogastric nerve supplies the skin over the inguinal region. The ilioinguinal nerve runs anteroinferiorly to the superficial inguinal ring, where it emerges to supply the skin on the superomedial aspect of the thigh (Figure 42–1).

Of note, the ventral rami of the lower intercostal nerves (T11 and T12) also pierce the transversus abdominis muscle to lie between it and the internal oblique. These latter nerves also supply sensation to the inferior abdominal wall, and block of these nerves as well as the iliohypogastric and ilioinguinal nerves is essential to provide anesthesia for procedures involving the lower abdominal wall.

Using the anatomic knowledge previously described, one needs to provide a method of block that allows accurate placement of local anesthetic between the internal oblique and external oblique muscles.

Methods of local anesthetic administration that do not accurately define placement between these muscular layers provide inconsistent anesthesia and analgesia of the abdominal wall and inguinal region. Unfortunately, this may result in the reporting of inadequate analgesia for a procedure that is more a problem of technique than of the block itself.6 Accurate block techniques must define the specific muscular layers of the abdominal wall. The only way to facilitate this is to use loss of resistance techniques that define fascial layers.

Initially, the anterior superior iliac spine is palpated and a mark made 2 cm medial and 2 cm superior from it (Figure 42–2). After skin preparation and infiltration with local anesthetic, a small puncture is made in the skin with a sharp needle to allow subsequent insertion of a blunt needle. The needle is inserted through the skin puncture site perpendicular to the skin. Increased resistance is met as the needle encounters the external oblique muscle. A loss of resistance is appreciated as the needle passes through the muscle to lie between it and the internal oblique. After the initial loss of resistance and negative needle aspiration for blood, 3 mL of local anesthetic is injected.

The needle is then withdrawn to skin and redirected at a 45-degree angle medially to again pierce the external oblique muscle (Figure 42–3). After loss of resistance, 3 mL of local anesthetic is again administered. The needle is then returned to skin and inserted 45 degrees laterally, and the procedure is repeated. Thus, a total of 9 mL of local anesthetic is placed in a fan-like distribution between the external and internal oblique muscles.

After completion of the block, the skin of the lower abdominal wall or inguinal region is tested for anesthesia.

Equipment

Any atraumatic needle blunt enough to appreciate a loss of resistance is used for this block. Examples are 22-gauge Whitacre, Sprotte, 18-gauge Tuohy-type (which can also be used to place catheters), 21-gauge Stimuplex needles, etc.

Indications for ilioinguinal/iliohypogastric blocks include anesthesia for any somatic procedure involving the lower abdominal wall/inguinal region such as inguinal herniorrhaphy2–5 and for analgesia after surgical procedures using a Pfannenstiel incision as for cesarean section7 and abdominal hysterectomy.8 These blocks do not provide visceral anesthesia and thus cannot be used as the sole anesthetic for procedures such as lower intraabdominal surgery. When used for inguinal herniorrhaphy, the sac (containing peritoneum) must be infiltrated with local anesthetic by the surgeon to complete anesthesia for the procedure.

There are no specific contraindications for these blocks apart from the generic contraindications to performance of any regional block such as infection at the procedure site, allergy to local anesthetics, indeterminate neuropathy, and so on.

Unless unusual circumstances occur requiring immediate anesthesia (thus requiring an intermediate-acting agent), a long-acting local anesthetic agent is used to provide the benefits of prolonged postoperative analgesia. We currently use ropivacaine in concentrations of 0.5–1% without adjuvants for ilioinguinal/iliohypogastric blocks (less than 1% concentrations when bilateral block such as Pfannenstiel incisions or bilateral herniorrhaphy are scheduled). For continuous infusions, ropivacaine in concentrations of 0.2–0.5% is used.

Because proper performance of ilioinguinal/iliohypogastric blocks requires multiple small volume injections the possibility of local anesthetic toxicity is remote. Pharmacokinetic studies of 3 mg/kg of 0.5% plain ropivacaine in children revealed peak plasma concentrations of ropivacaine well below the toxic level.9 A similar study in adults receiving 60–70 mL of 0.5% ropivacaine again revealed low peak plasma concentrations.10

Because the block is limited to the lower abdominal wall and inguinal region, any hemodynamic changes would be unusual. As with other blocks, the patient is advised to protect the anesthetized area from trauma.

Proper performance of ilioinguinal/iliohypogastric blocks places the injection medial and superior to the anterior superior iliac spine. Some texts advocate performing the block from a point medial and inferior to the anterior superior iliac spine, which essentially places the injection within or inferior to the inguinal ligament. This may result in lateral femoral cutaneous or femoral block with little or no ilioinguinal/iliohypogastric anesthesia. However, even properly performed ilioinguinal/iliohypogastric blocks can result in transient femoral anesthesia with a reported incidence of 3.7–5%.11,12 The mechanism of femoral anesthesia with these methods is tracking of local anesthetic along the fascia iliaca.13 In the event of femoral anesthesia associated with ilioinguinal/iliohypogastric blocks, the surgeon is notified and the patient is advised to protect the lower extremity until the block recedes.

Perforation of both the small14 and large15 bowels and creation of a pelvic hematoma16 have been reported after ilioinguinal/iliohypogastric blocks. This illustrates the importance of using blunt needles to appreciate the loss of resistance as the needle traverses the layers of the abdominal wall.

Prolonged postoperative analgesia for procedures using a Pfannenstiel incision has been successfully produced using bilateral catheters. Such catheters are an excellent alternative to epidural analgesia by allowing unlimited ambulation without the need for urinary catheterization. Control of visceral pain with NSAIDS or other agents is necessary to complete analgesia.

Method

From a point 2 cm medial and 2 cm cephalad from the anterior superior iliac spine, an 18-gauge Tuohy-type needle is inserted in a slightly medial and caudal orientation to the skin to pierce the external oblique muscle (see Figure 42–2). After loss of resistance, a multilumen catheter is inserted and directed medially for 5 cm and secured to skin. The procedure is repeated on the other side. The catheters are either infused using separate pumps or a single pump with flow-restrictor catheters that allow accurate individual catheter flow are used. Individual catheter flow rates of 4 mL/h (0.2% ropivacaine) have been used.

Regional anesthesia for surgical procedures involving the lower abdomen and inguinal region can be safely and successfully performed using ilioinguinal and iliohypogastric blocks. These techniques accord excellent postoperative analgesia, obviating the need for large-dose opioids and thus facilitating early ambulation and discharge.

Thoracic paravertebral block (TPVB) is the technique of injecting local anesthetic alongside the thoracic vertebra close to where the spinal nerves emerge from the intervertebral foramen.1,2 This produces unilateral, segmental, somatic, and sympathetic nerve blockade,3 which is effective for anesthesia and in treating acute and chronic pain of unilateral origin from the chest and abdomen.1 Hugo Sellheim of Leipzig (1871–1936) is believed to have pioneered TPVB in 1905.1,2 Kappis, in 1919, developed the technique of paravertebral injection, which is comparable to the one in present-day use. Although paravertebral block was fairly popular in the early 1900s, it seemed to have fallen into disfavor during the mid and later part of the century, the reason for which is not known. In 1979 Eason and Wyatt rekindled interest by describing a technique of paravertebral catheter placement.4 Our understanding of the safety and efficacy of TPVB has improved significantly in the last 25 years, and there has been a gradual renewal of interest in this technique. Currently it is used not only for analgesia but also for surgical anesthesia,5–7 and its application has been extended to children.8–10

Anatomy

The thoracic paravertebral space (TPVS) is a wedge-shaped space located on either side of the vertebral column (Figure 43–1). The parietal pleura forms the anterolateral boundary. The base is formed by the vertebral body, intervertebral disc, and the intervertebral foramen with its contents. The transverse process and the superior costotransverse ligament form the posterior boundary. Lying in between the parietal pleura anteriorly and the superior costotransverse ligament posteriorly is a fibroelastic structure, the endothoracic fascia, which is the deep fascia of the thorax (Figure 43–1, 43–2, and 43–3).1,11–15 Medially the endothoracic fascia is attached to the periosteum of the vertebral body. A layer of loose areolar connective tissue, the subserous fascia, lies between the parietal pleura and the endothoracic fascia. Therefore there are two potential fascial compartments in the TPVS: the anterior extrapleural paravertebral compartment and the posterior subendothoracic paravertebral compartment (see Figures 43–1 and 43–2). The TPVS contains adipose tissue within which lie the intercostal (spinal) nerve, the dorsal ramus, intercostal vessels, rami communicantes, and anteriorly the sympathetic chain. The spinal nerves are segmented into small bundles and lie freely in the adipose tissue of the TPVS, which make them accessible to local anesthetic solutions injected into the TPVS.16

The TPVS communicates with the epidural space medially17,18 and with the intercostal space laterally. The TPVS on either side of the thoracic vertebra also communicate with each other through the epidural and prevertebral space.1,12,15 The cranial extension of the TPVS is challenging to define and may significantly vary; however, we have observed direct paravertebral spread of radiopaque contrast medium from the thoracic to the cervical paravertebral space, indicating a direct anatomic continuity. The TPVS also communicates caudally through the medial and lateral arcuate ligaments with the retroperitoneal space behind the fascia transversalis, where the lumbar spinal nerves are located.13,19–21

Mechanism of Block & Distribution of Anesthesia

TPVB produces ipsilateral somatic and sympathetic nerve blockade (Figure 43–4) due to a direct effect of the local anesthetic on the somatic and sympathetic nerves in the TPVS, extension into the intercostal space laterally, and the epidural space medially. The overall contribution of epidural spread to the dermatomal distribution of anesthesia following a TPVB is not well defined. However, some degree of ipsilateral spread of local anesthetic toward the epidural space probably occurs in the majority of patients, resulting in a greater distribution of anesthesia than occurs with paravertebral spread alone.18 The dermatomal distribution of anesthesia following a single injection of a large volume (eg, injection of 15–25 mL of local anesthetic at one level) varies and is often unpredictable.1,3,22 However, the injected solutions routinely spread both cephalad and caudad to the site of injection to some extent (Figure 43–5). Nevertheless, the multiple-injection technique, where small volumes (3–4 mL) of local anesthetic are injected at several contiguous thoracic levels, is preferable over single, large-volume injection. This is particularly important when reliable anesthesia over several ipsilateral thoracic dermatomes is desired, such as when TPVB is used for anesthesia during breast surgery.

Segmental contralateral anesthesia, adjacent to the site of injection, occurs in approximately 10% of patients after single-injection TPVB and may be due to epidural or prevertebral spread. Bilateral symmetrical anesthesia due to extensive epidural spread or unintentional intrathecal injection into a dural sleeve may occur, particularly when the needle is directed medially or when a larger volume of local anesthetic (>25 mL) is used. For this reason, during placement of TPVB, patients should be monitored using the same vigilance and methods as those employed for injection using the large-volume, single-injection epidural technique. The ipsilateral ilioinguinal and iliohypogastric nerves may also occasionally be involved after lower thoracic paravertebral injections. This is either due to epidural spread or extended subendothoracic fascial spread to the retroperitoneal space where the lumbar spinal nerves are located. The effect of gravity on the dermatomal spread of anesthesia after TPVB is unknown, but there may be a tendency for preferential pooling of injected solution toward the dependent levels.3,23,24

Technique

It is preferable to perform TPVB with the patient in the sitting position because the surface anatomy is better visualized and patients are often more comfortable. However, when this is not possible or practical, TPVB can also be performed with the patient in the sitting, lateral, or prone position. The number and level of injections are selected according to the desired spread of local anesthesia. In this example, description of the TPVB for breast surgery is described. Surface landmarks are identified and marked with a skin marker before block placement (Figure 43–6). Skin markings are also made 2.5 cm lateral to the midline at the thoracic levels that are to be blocked. These markings indicate the needle insertion sites and should lie over the transverse process of the vertebra (Figure 43–7).

A standard regional anesthesia tray is prepared, and strict asepsis should be maintained during block placement. A 22-gauge Tuohy- or Quincke-tip spinal needle is used for a single- or multiple-injection TPVB (Figure 43–8). If the needle does not have depth markings on its shaft, a depth guard (see Figure 43–8) is recommended. An epidural set is used if insertion of a catheter into the TPVS is planned. Multiple injections during TPVB are uncomfortable and require a proper premedication (eg, midazolam 2–3 mg plus fentanyl 50–100 mcg) to ensure patient acceptance and comfort during the block placement.

Loss‐of-Resistance Technique

There are several different techniques of TPVB. The classical technique involves eliciting loss of resistance. The skin and underlying tissue is infiltrated with lidocaine 1%, and the block needle is inserted perpendicular to the skin in all planes to contact the transverse process of the vertebra. Note that due to the acute angulation of the thoracic spines in the midthoracic region, the transverse process that is contacted is the one from the lower vertebra (Figures 43–9 and 43–10). The depth at which the transverse process is contacted varies (3–4 cm) and depends on the build of the individual and the level at which the needle is inserted. The depth is deeper at the cervical and lumbar spine level and shallower at the thoracic levels. During needle insertion it is possible to miss the transverse process and inadvertently puncture the pleura. Therefore it is imperative to search and make contact with the transverse process before advancing the needle too deep and risking pleural puncture. To minimize this complication, the block needle should initially be inserted only to a maximum depth of 4 cm at the thoracic and 5 cm at the cervical and lumbar levels. If bone is not contacted it should be assumed that the needle is in between two adjacent transverse processes. The needle should be withdrawn to the subcutaneous tissue and reinserted with a cephalad or caudad direction to the same depth (4 cm) until bone is contacted. If bone is still not encountered, the needle is advanced a further centimeter and the above procedure repeated until the transverse process is identified. The needle is then walked above (these authors' preference) or below the transverse process and gradually advanced until a loss of resistance is elicited as the needle traverses the superior costotransverse ligament into the TPVS (Figures 43–3 and 43–11). This usually occurs within 1 to 1.5 cm from the superior edge of the transverse process (see Figure 43–3). Although a subtle “pop” or “give” may be appreciated as the needle traverses the superior costotransverse ligament, this should not be entirely relied on. Instead, the depth of the needle placement should be guided by the initial bone contact (skin-transverse process plus 1 to 1.5 cm). Unlike localization of the epidural space, in which the loss of resistance is typically unequivocal, loss of resistance elicited during TPVB is very subtle and takes time to appreciate and master. The use of a glass syringe may facilitate recognition of the loss of resistance when this method is used.

Predetermined Distance Technique

TPVB can also be performed by advancing the needle by a fixed predetermined distance (1 cm) once the needle is walked off the transverse process, without eliciting loss of resistance (Figure 43–12).5–7,23 Proponents of this technique have used it very successfully with low risk of pneumothorax. The use of a depth marker is recommended to avoid inadvertent pleural or pulmonary puncture.

Placement of Thoracic Paravertebral Catheter

If a continuous TPVB (CTPVB) is planned, a catheter is inserted through a Tuohy needle into the TPVS.4,22 Unlike epidural catheterization, certain resistance is commonly encountered during insertion of the paravertebral catheter. This can be overcome by manipulating (rotating or angling) the needle or injecting 5–10 mL of saline to create a space before catheter insertion. An unusually seamless passage of catheter should arouse the suspicion of interpleural placement.

Perhaps the safest and simplest method of placing a catheter into the TPVS is to place it under direct vision from within the open chest cavity.8,25 Obviously, this requires an open thorax and is therefore done exclusively in patients undergoing a thoracotomy. This technique involves reflecting the parietal pleura from the posterior wound margin onto the vertebral bodies over several thoracic segments, thereby creating an extrapleural paravertebral pocket (Figure 43–13) into which a percutaneously inserted catheter is placed against the angles of the exposed ribs. The pleura is reapposed to the chest wall, and the thorax is closed. This method can be combined very effectively with a preincisional, single-shot, percutaneous thoracic paravertebral injection to provide perioperative analgesia during thoracic surgery.26

Indications

TPVB is indicated for anesthesia and analgesia for unilateral surgical procedures in the chest and abdomen. Commonly reported indications are listed in Table 43–1. The use of bilateral TPVB has also been reported.

Contraindications

There are very few absolute contraindications for TPVB. These include infection at the site of injection, allergy to local anesthetic drug, empyema, and a neoplastic mass occupying the paravertebral space. Coagulopathy, bleeding disorders, or patients receiving anticoagulant drugs are relative contraindications for TPVB. One must exercise caution in patients with kyphoscoliosis or deformed spines and those who have had previous thoracic surgery. The chest deformity in the former may predispose to inadvertent thecal or pleural puncture, and the altered paravertebral anatomy due to fibrotic obliteration of the paravertebral space or adhesions of the lung to the chest wall in the latter may predispose to pulmonary puncture.

Choice of Local Anesthetic

Since TPVB does not result in motor weakness of the extremities, long-lasting analgesia is nearly always desirable with TPVB. Consequently, long-acting local anesthetic drugs are typically used. These include bupivacaine or levobupivacaine 0.5% and ropivacaine 0.5–0.75%. For single-injection TPVB, 20–25 mL of local anesthetic is injected in aliquots, whereas for multiple-injection TPVB, 4–5 mL of local anesthetic is injected at each level planned. Higher concentrations of local anesthetic (eg, ropivacaine 0.75%) may reduce the onset time and prolong the duration of anesthesia and analgesia. The maximum dose of local anesthetic must be adjusted in the elderly, poorly nourished, and frail patients. The TPVS is well vascularized, leading to relatively rapid absorption of local anesthetic into the systemic circulation. Consequently, peak plasma concentration of the local anesthetic agent is attained quickly. Epinephrine (2.5–5 mcg/mL) containing local anesthetic solutions may be used during the initial injection because it reduces systemic absorption and thereby reduces the potential for toxicity. Epinephrine also helps in increasing the maximum allowable dose of local anesthetic. The duration of anesthesia after TPVB ranges from 3 to 4 h, but analgesia often lasts much longer (8–18 h). If CTPVB is planned, eg, for postoperative analgesia after thoracotomy or continuous pain relief for multiple fractured ribs, then an infusion of bupivacaine or levobupivacaine 0.25% or ropivacaine 0.2% at 0.1 to 0.2 mL/kg/h is started after the initial bolus injection and continued for 3 to 4 days or as indicated. It is our experience that using a higher concentration of local anesthetic (eg, bupivacaine 0.5% instead of 0.25%) for the CTPVB does not result in better quality of analgesia, and it may increase the potential for local anesthetic toxicity.

Practical Management of Thoracic Paravertebral Block

Breast Surgery

Thoracic paravertebral injection of local anesthetic at multiple levels (C7 through T6) in conjunction with intravenous sedation is effective for surgical anesthesia during major breast surgery (Figure 43–14).5,6,27 The C7 spinous process is the most prominent cervical spinous process; the inferior border of the scapula corresponds to T7. Compared with patients who receive only general anesthesia (GA), patients who receive a multiple-injection TPVB for major breast surgery have less postoperative pain, require fewer analgesics, and have less nausea and vomiting after surgery. However, to effectively use the multiple-injection TPVB technique for anesthesia during breast surgery, one must understand the complex innervation of the breast. The anterior and lateral chest wall receives sensory innervation from the anterior and lateral cutaneous branches of the intercostal nerves (T2 through T6), the axilla (T1 to T2), the infraclavicular region from the supraclavicular nerves (C4 to C5), and the pectoral muscles from the lateral (C5 to C6) and medial (C7 to C8) pectoral nerves. There also may be overlapping sensory innervation from the contralateral side of the chest. This complex innervation of the breast from the C4 to T6 spinal segments explains why TPVB may not provide complete anesthesia for dissection over the pectoral muscle or the infraclavicular region. However, this can be overcome with proper sedation during surgery as well as by injections of local anesthetic by the surgeon intraoperatively into the sensitive areas. Injection of a local anesthetic subcutaneously along the inferior border of the clavicle or to perform an ipsilateral superficial cervical plexus block, in order to anaesthetize the supraclavicular nerves (C4 to C5) will minimize discomfort and sedative and analgesic requirements during surgery. A combination of midazolam, or propofol infusion, or IV opioid can be used to provide comfort to the patients intraoperatively. Dexmedetomidine, a highly selective α2-adrenoceptor agonist, with its sedative, analgesic, and minimal or no respiratory depression properties is a useful alternative for sedation during breast surgery under TPVB.

When combined with general anesthesia, a single-injection TPVB with ropivacaine (2 mg/kg diluted to 20 mL with 0.9% saline) with 1:200,000 epinephrine, performed prior to the induction of GA can be used. This provides excellent postoperative analgesia, reduces postoperative analgesic requirement, reduces postoperative vomiting, facilitates the earlier resumption of oral fluid intake, reduces the postoperative decline in respiratory function, and augments the recovery of postoperative respiratory mechanics.

Postthoracotomy Pain Relief

CTPVB is an effective method of providing analgesia after thoracotomy (Figure 43–15). Ideally, TPVB should be established before the thoracotomy incision, via a catheter that is inserted percutaneously, and continued for 4 to 5 days after surgery. However, if an extrapleural paravertebral catheter is being placed under direct vision from within the chest during surgery, then a single-injection TPVB can be performed at the level of the thoracotomy incision before the surgical incision, and a continuous infusion of local anesthetic is commenced after the catheter placement. Either method provides effective perioperative analgesia.

It is important to note that CTPVB is inadequate on its own for complete pain relief after a thoracotomy and must be combined with an opioid [best as intravenous patient-controlled analgesia (IVPCA)] and a NSAID to provide optimal analgesia.26 Analgesia achieved by CTPVB is comparable to epidural analgesia but with less hypotension, urinary retention, and the side effects commonly seen with epidural opioid administration.1,26,28,29 The opioid requirement with such an approach is significantly reduced by the CTPVB, and analgesia is superior to IVPCA alone.1,30

Multiple Fractured Ribs

TPVB is an effective method of providing pain relief in patients with unilateral multiple fractured ribs.1,22,23 A single thoracic paravertebral injection of 25 (SD 5) mL of bupivacaine 0.5% produces pain relief for a mean duration of 9.9 (SD 1.2) h and improves respiratory function and arterial blood gases.1,23 To avoid recurrence of pain and deterioration in respiratory function, a thoracic paravertebral catheter can be inserted midway between the highest and the lowest fractured rib, and a CTPVB can be commenced after administration of the initial bolus injection. CTPVB in combination with a NSAID provides continuous pain relief and produces a sustained improvement in respiratory parameters and arterial oxygenation.22 Since TPVB does not cause urinary retention or affect lower limb motor function, it is useful in patients with multiple fractured ribs who also have concomitant lumbar spinal trauma since it also allows continuous neurologic assessment for signs of spinal cord compression.31

Pharmacokinetic Considerations

Relatively large doses of local anesthetics are commonly used during CTPVB. Therefore there is the potential for local anesthetic toxicity, and patients should be closely monitored during CTPVB and the infusion stopped if signs develop. During a prolonged thoracic paravertebral infusion there is progressive accumulation of local anesthetic in the plasma, and the plasma concentration of the drug may exceed the threshold for central nervous system toxicity (eg, 2–4.5 mcg/mL for bupivacaine). Despite the systemic accumulation, local anesthetic toxicity is rare. This may be the case because, although the total plasma concentration of the local anesthetic increases postoperatively, the free fraction of the drug remains unchanged32 and may be due to the postoperative increase in α1-acid glycoprotein concentration,32 the protein that binds to local anesthetic drugs. There is also a greater increase in the S-bupivacaine enantiomer,33,34 which is associated with lower toxicity, than the R-enantiomer. Due to concerns of systemic accumulation and local anesthetic toxicity with prolonged paravertebral infusion, it is preferable to use a local anesthetic with lower potential for toxicity, such as ropivacaine. One must also exercise caution in the elderly and frail patients as well as in patients with impaired hepatic and renal function.

Complications & How to Avoid Them

Based on published data the incidence of complications after TPVB is relatively low and varies from 2.6 to 5%.1,5,35,36 These include vascular puncture (3.8%), hypotension (4.6%), pleural puncture (1.1%), and pneumothorax (0.5%).35 Unlike with thoracic epidural anesthesia, hypotension is rare in normovolemic patients after TPVB because the sympathetic blockade is unilateral. However TPVB may unmask hypovolemia and result in hypotension. Therefore TPVB should be used with caution in patients who are hypovolemic or hemodynamically labile. Nevertheless, hypotension is rare even after bilateral TPVB, probably owing to the segmental nature of the bilateral sympathetic blockade.

Pleural puncture and pneumothorax are two complications that often dissuade anesthesiologists from performing a TPVB. Inadvertent pleural puncture is uncommon after TPVB and may or may not result in a pneumothorax, which is usually minor and can be managed conservatively. Clues that suggest pleural puncture during a TPVB are a gritty pleural pop sensation, irritating cough, onset of sharp chest or shoulder pain, or sudden hyperventilation. Contrary to common belief, air cannot be aspirated through the needle unless the lung is also inadvertently punctured or air that may have entered the pleural cavity during removal of the stylet is aspirated. Such patients should be closely monitored for the possible development of a pneumothorax. It should be kept in mind that pneumothorax may be delayed in onset and a chest radiograph taken too early to exclude a pneumothorax may not be conclusive. Even a radiologic contrast study using a chest radiograph may be difficult to interpret because the intrapleural contrast disperses rapidly, does not define any specific anatomic plane, and tends to spread to the diaphragmatic angles or horizontal fissure.

Systemic local anesthetic toxicity can occur due to inadvertent intravascular injection or from using an excessive dose of local anesthetic. The local anesthetic solution must be injected in aliquots, and the dosage must be adjusted in the elderly and frail patient. An epinephrine-containing local anesthetic solution is suggested to enable the recognition of intravascular injection and reduce the systemic absorption of the local anesthetic.

Inadvertent epidural, subdural, or intrathecal injection and spinal anesthesia can also occur. Published data suggest that these complications are more frequent when the needle is directed medially but may also occur with a normally positioned needle due to the close proximity of the needle to the dural cuff and intervertebral foramen. Therefore the needle must never be directed medially, and care must be taken to exclude intrathecal injection by routinely performing an aspiration test before injection. Transient ipsilateral Horner syndrome can occasionally develop after TPVB. This is due to cephalad spread of the local anesthetic to the stellate ganglion or to the preganglionic fibers of the first few segments of the thoracic spinal cord. Bilateral Horner syndrome has also been reported and may be due to epidural spread or prevertebral spread to the contralateral stellate ganglion. Sensory changes in the arm and lower extremity may also occur after a TPVB. The former is due to spread of local anesthetic to the lower components of the ipsilateral brachial plexus (C8 and T1), and the latter is due to extended subendothoracic fascial spread to the ipsilateral retroperitoneal space where the lumbar spinal nerves are located (discussed earlier), but epidural spread as a cause cannot be excluded. Motor blockade or bilateral symmetrical anesthesia involving the lower extremity is rare. It generally suggests significant epidural spread and may be more common if large volumes of local anesthetic (>25–30 mL) are injected at a single level. Therefore if a wide segmental spread of anesthesia is desired, it is preferable to perform the multiple-injection technique or inject a smaller volume of local anesthetic at several levels a few dermatomes apart.

Lumbar paravertebral block (LPVB) is technically similar to a TPVB but due to differences in anatomy between the thoracic and lumbar paravertebral spaces the two paravertebral techniques are described separately. LPVB is technically simple to perform and used most commonly in combination with a TPVB, as a thoracolumbar paravertebral block, for surgical anesthesia during inguinal herniorrhaphy.

Anatomy

The lumbar paravertebral space (LPVS) is limited anterolaterally by the psoas major muscle; medially by the vertebral bodies, the intervertebral disks, and the intervertebral foramen with its contents; and posteriorly by the transverse process and the ligaments that are interposed between the adjoining transverse processes. Unlike the TPVS, which contains adipose tissue, the LPVS is occupied primarily by the psoas major muscle. The psoas major muscle is made up of a fleshy anterior part that forms the main bulk of the muscle, and a thin accessory posterior part.37 The main bulk originates from the anterolateral surface of the vertebral bodies and the accessory part originates from the anterior surface of the transverse process.37 The two parts fuse to form the psoas major muscle except near the vertebral bodies where the two parts are separated by a thin fascia within which lie the lumbar spinal nerve roots and the ascending lumbar veins.37 The ventral rami of the lumbar spinal nerve roots extend laterally in this intramuscular plane formed by the two parts of the psoas major muscle and form the lumbar plexus within the substance of the psoas major muscle.37 The psoas muscle is enveloped by a fibrous sheath, “the psoas sheath,” which continues laterally as the fascia covering the quadratus lumborum muscle. During a LPVB the local anesthetic is injected anterior to the transverse process into a triangular space between the two parts of the psoas major muscle containing the lumbar spinal nerve root.

The LPVS communicates medially with the epidural space. A series of tendinous arches extends across the constricted parts of the lumbar vertebral bodies, which are traversed by the lumbar arteries and veins and sympathetic fibers. These tendinous arches may provide a pathway for the spread of local anesthetic from the LPVS to the anterolateral surface of the vertebral body, the prevertebral space, and the contralateral side and may be the pathway through which the ipsilateral lumbar sympathetic chain may occasionally be involved.

Mechanism of Block & Distribution of Anesthesia

A lumbar paravertebral injection produces ipsilateral dermatomal anesthesia (Figure 43–16) by a direct effect of the local anesthetic on the lumbar spinal nerves and by medial extension into the epidural space via the intervertebral foramen. The contribution of epidural spread to the overall distribution of anesthesia after a LPVB is unknown but probably occurs in the majority of patients and depends on the volume of local anesthetic injected at a given level. Ipsilateral sympathetic blockade may also occur due to epidural spread or spread of local anesthetic anteriorly via the tendinous arches to the rami communicantes or the lumbar sympathetic chain.

Technique

Lumbar paravertebral block can be performed with the patient in the sitting, lateral, or prone position. Surface landmarks must be identified and marked with a skin marker before block placement. The spinous process of the vertebra at the levels to be blocked represents the midline, the iliac crest corresponds to the L3-4 interspace, and the tip of the scapula corresponds to the T7 spinous process. Skin markings are also made 2.5 cm lateral to the midline at the levels that are to be blocked (Figure 43–17) or one can draw a line 2.5 cm lateral to the midline and perform the injections along this line. A standard regional anesthesia tray is prepared; strict asepsis should be maintained during block placement. An 8-cm, 22-gauge, Tuohy or Quincke tip spinal needle (see Figure 43–8) is used for LPVB. Similarly to the recommendations for TPVB, the use of needles with depth markings on the shaft of the needle or a guard indicating the depth (see Figure 43–8) is recommended.

Advancing the needle by a fixed predetermined distance (1 cm) beyond the transverse process, without eliciting paresthesia, is the method most commonly used to perform LPVB. The block needle is inserted perpendicular to the skin until the transverse process is contacted. The depth at which the transverse process is contacted is variable (4–6 cm) and depends on the build of the patient. Once the transverse process is identified, the marking on the needle is noted or the depth marker is adjusted so that it is 1 cm beyond the skin–transverse process depth. The needle is then withdrawn to the subcutaneous tissue and reinserted at a 10- to 15-degree superior or inferior angle so that it slides off the superior or inferior edge of the transverse process, similarly to the technique in thoracic paravertebral block (see Figure 43–11). The needle is advanced by a further 1 cm beyond the point at which it made contact with the transverse process or until the depth marker is reached. After negative aspiration for blood or CSF, the local anesthetic is injected. Since spread of local anesthetic after a single large-volume lumbar paravertebral injection is unpredictable, the multiple-injection technique in which 4–5 mL of local anesthetic is injected at each level is more commonly used.

Choice of Local Anesthetic

As for TPVB, long-acting local anesthetic agents such as bupivacaine 0.5%, ropivacaine 0.5–0.75%, or levobupivacaine 0.5% are commonly used for LPVB. During a multiple-injection LPVB, 4–5 mL of the local anesthetic is injected at each level. Anesthesia develops in about 15–30 min and lasts for 3 to 6 h. Analgesia is also long-lasting (12–18 h) and generally outlasts the duration of anesthesia. There are no data on the pharmacokinetics of local anesthetic after LPVB. Nevertheless, the addition of epinephrine (2.5–5 mcg/mL) to the local anesthetic may reduce systemic absorption and reduce the potential for toxicity.

Indications & Contraindications

The indications for LPVB are limited. Published data suggest that it is most commonly used in combination with TPVB (T10 through L2) for surgical anesthesia during inguinal herniorrhaphy. It can also be used for diagnostic purpose during evaluation of groin or genital pain, such as that following nerve entrapment syndrome after inguinal herniorrhaphy. Contraindications for LPVB are similar to TPVB, but one must exercise caution in patients who are anticoagulated or are receiving prophylactic anticoagulants since psoas hematoma with lumbar plexopathy has been reported.

Complications & How to Avoid Them

Published data suggest that complication is rare after LPVB.38,39 Nevertheless, it is possible to inadvertently inject local anesthetic into the intravascular, epidural, or intrathecal spaces during LPVB and may be more common if the needle is directed medially. Therefore the direction of the block needle should be maintained perpendicular to the skin during insertion, and medial angulation should be avoided. Intraperitoneal injection or visceral injury (renal) may also occur, although this can occur only as a result of gross technical error. Motor weakness involving the ipsilateral quadriceps muscle may result if the L2 spinal nerve is blocked (femoral nerve L2 to L4).

Paravertebral block is conceptually a simple technique with few contraindications. Proper training is necessary to acquire stereotactic skills required to ensure a high success rate. Thoracic paravertebral block produces unilateral somatic and sympathetic nerve blockade that is adequate for surgical anesthesia during breast surgery and for analgesia when pain is of unilateral origin from the chest or abdomen. Lumbar paravertebral block is less commonly used in clinical practice. As a thoracolumbar paravertebral block it is effective for surgical anesthesia during inguinal herniorrhaphy. Hemodynamic stability is usually maintained after a paravertebral block due to the unilateral nature of sympathetic blockade. Bladder and lower limb motor function is also preserved, and no additional nursing vigilance is required during the postoperative period. Bilateral paravertebral block has also been reported, but its role in clinical practice is still to be defined.

The intercostal nerves (ICNs) innervate the major parts of the skin and musculature of the chest and abdominal wall. The block of these nerves was first described by Braun in 1907, in the textbook Die Lokalanästesie.1 In the 1940s, clinicians noticed that intercostal nerve blocks (ICNBs) could favorably effect a reduction in pulmonary complications and in narcotic requirements after upper abdominal surgery.1 In 1981, continuous ICNB was introduced to overcome the problems associated with repeated multiple injections.1 Today, ICNB is used in a great variety of acute and chronic pain conditions affecting the thorax and upper abdomen. Less commonly, it is also used for breast and minor chest wall surgery and, in combination with celiac plexus blockade, abdominal operations, usually with light sedation or general anesthesia. As with many other regional techniques, the advantages of ICNBs include superior analgesia, opioid-sparing effect, improved pulmonary mechanics, reduced central nervous system depression, and avoidance of urinary retention. It should be noted, however, that supplemental systemic analgesia is also almost always needed. The disadvantages of the technique include the requirement for technical expertise, risks of pneumothorax, and local anesthetic toxicity with multiple levels of blockade.

ICNB provides excellent analgesia for chest trauma such as rib fractures2,3 and for postsurgical pain after chest and upper abdominal surgery such as thoracotomy, thoracostomy, mastectomy, gastrostomy, and cholecystectomy.4 Respiratory parameters typically improve with relief of pain.2,3 Blockade of the two dermatomes above and the two below the level of surgical incision is required. ICNB does not block visceral abdominal pain, for which a celiac plexus block is required. It is inadequate for renal surgery since a block from T5 to L3 is required. In itself, ICNB alone does not provide adequate intraoperative anesthesia, and supplemental analgesics or sedatives are usually required except for minor body surface surgery. Neurolytic ICNB may be used to manage chronic pain conditions such as postmastectomy pain (T2) and postthoracotomy pain.

1. 1. When pneumothorax would be a disaster. ICNBs may help a patient tethering on the brink of respiratory decompensation, but if an unintended pneumothorax could have serious consequences, an alternative block should be considered unless a chest tube is in place.

2. 2. Coagulation abormalities. This contraindication is not as strong as in central neuraxial blocks but may become absolute if severe.

3. 3. Local infection, lack of expertise and resuscitating equipment, and lack of any short-term plan to wean from the ventilator should also discourage the use of this block.

As thoracic nerves T1 to T12 emerge from their respective intervertebral foramina, they divide into the following rami (Figure 44–1):

1. 1. The paired gray and white anterior rami communicantes, which pass anteriorly to the sympathetic ganglion and chain

2. 2. The posterior cutaneous ramus, supplying skin and muscle in the paravertebral region

3. 3. The ventral ramus (ICN, the main focus of this chapter)

T1 and T2 send nerve fibers to the upper limbs and the upper thorax, T3 through T6 supply the thorax, T7 through T11 supply the lower thorax and abdomen, and T12 innervates the abdominal wall and the skin of the front part of the gluteal region (Figure 44–2). Carrying both sensory and motor fibers, the ICN pierces the posterior intercostal membrane about 3 cm (in adults) distal to the intervertebral foramen to enter the subcostal grove where it, for the most part, continues to run parallel to the rib although branches may often be found anywhere between adjacent ribs. Its course within the thorax is sandwiched between the parietal pleura and innermost intercostal (also called the intercostalis intimus) muscles (inwardly) and the external and internal intercostal muscles (outwardly) (Figures 44–3 and 44–4). Just anterior to the midaxillary line, it gives off the lateral cutaneous branch. As the ICN approaches the midline, it turns anteriorly and pierces the overlying muscles and skin to terminate as the anterior cutaneous. There are notable variations. The first thoracic nerve (T1) has no anterior cutaneous branch, usually has no lateral cutaneous branch, and most of its fibers leave the intercostal space by crossing the neck of the first rib to join those from C8, while a smaller bundle continues on a genuine intercostal course to supply the muscles of the intercostal space. Some fibers of T2 and T3 give rise to the intercostobrachial nerve, which innervates the axilla and the skin of the medial aspect of the upper arm as far distal as the elbow. In addition, the ventral ramus of T12 is similar to the other ICNs but is called a subcostal nerve because it is not positioned between two ribs.

Lateral Cutaneous Branch

From their origins just anterior to the midaxillary line, the lateral cutaneous branches of T2 through T11 pierce the internal and external intercostal muscles obliquely before dividing into the anterior and posterior branches (see Figure 44–4). These branches supply the muscles and skin of the lateral torso. The anterior branches supply of T7 to T11 innervate the skin as far forward as the lateral edge of the rectus abdominis. The posterior branches of T7 to T11 supply the skin overlying the latissimus dorsi. The lateral cutaneous branch of T12 does not divide. Most of the ventral ramus of T12 joins that of L1 to form the iliohypogastric, ilioinguinal, and genitofemoral nerves; the remaining part pierces the transverse abdominal muscle to lie between it and the internal oblique muscle.

Anterior Cutaneous Branch

The anterior cutaneous branches of T2 through T6 pierce the external intercostals and pectoralis major muscles to enter the superficial fascia near the lateral border of the sternum to supply the skin of the anterior part of the thorax near the midline and slightly beyond (see Figure 44–4). Smaller branches (T1 through T6) exist to supply the intercostal muscles and parietal pleura, and these branches may cross to adjoining intercostal spaces. The anterior cutaneous branches of T7 through T12 pierce the posterior rectus sheath to supply motor nerves to the rectus muscle and sensory fibers to the skin of the anterior abdominal wall. Some final branches of T7 through T12 continue anteriorly and, together with L1, innervate the parietal peritoneum of the abdominal wall. Their anterior course continues and becomes superficial near the linea alba to provide cutaneous innervation to the midline of the abdomen and a couple of centimeters beyond.

ICNB blocks the ipsilateral sensory and motor fibers of the ICNs by a direct effect of the local anesthetic. Three milliters of solution injected through a needle spreads easily for some 4–6 cm along that single subcostal groove distally and proximally (see Figure 44–3). If a catheter is inserted at the angle of the rib and directed medially 2–3 cm, the tip of the catheter will lie medial to the medial border of the intercostalis intimus muscle; 20 mL of solution can spread to the paravertebral space to contact 3–5 ICNs.

As with any regional block, some basic safety rules apply. The patient's airway and breathing must first be assessed and monitored. An intravenous line should be established, and resuscitation drugs should be readily available. Sedation and analgesia may be used in selected cases. Supplemental oxygen may be required. During the block, the clinician's hand controlling the needle should be firmly in contact with the patient's body. ICNB may be performed in an anesthetized patient, although spinal anesthesia has been reported in patients when ICNB was performed under general anesthesia,4 and there is a concern that the risk of pneumothorax may be increased in a patient under positive pressure ventilation. After the block, the patient should be monitored for potential complications. In the case of ICNB, they include pneumothorax, local anesthetic toxicity, hematoma, nerve damage, infection, and, rarely, spinal anesthesia.

The ICN can be blocked anywhere proximal to the midaxillary line, where the lateral cutaneous branch originates. In children, the block is commonly carried out at the posterior axillary line or, alternatively, just lateral to the paraspinal muscles, at the angle of the rib. In adults, the most popular site for ICNB is at the angle of the rib (6–8 cm from the spinous processes, Figure 44–5). Blocking the ICN at this location is relatively easy, is unlikely to result in direct injection into the dural sheath, and ensures that the tissues innervated by the lateral cutaneous nerve are blocked. At the angle of the rib, the rib is relatively superficial and easy to palpate, and the subcostal groove is the widest, theoretically reducing the probability of pleural puncture. Within this groove, the nerve is inferior to the posterior intercostal artery, which is inferior to the intercostal vein (Figures 44–6 and 44–3) (Mnemonic: VAN (vein/artery/nerve). They are surrounded mainly by adipose tissue and are sandwiched between the internal intercostal and the innermost intercostal (intercostalis intimus) muscles. The nerve often runs as three or four separate bundles, without an enclosing endoneural sheath, making it easily accessible to blockade. Blockade medial to the angle of the rib is not recommended because the nerve lies deep to the posterior intercostal membrane with very little tissue between it and the parietal pleura, and the overlying sacrospinalis muscle makes rib palpation difficult. Blockade distal to the anterior axillary line is more difficult because the nerve has left the subcostal groove, reentered the intercostal space and lies in the substance of the internal intercostal muscle.

ICNB can be performed with the patient in the prone, sitting, or lateral position (block side up), with due considerations given to age, mental, physical, and ventilatory status, along with any other concomitant blocks contemplated. For the prone position, a pillow should be placed under the patient's upper abdomen, and the arms are allowed to hang off the sides. The sitting patient should lean slightly forward holding a pillow and be supported. The arms should be forward. The position of the arm in either position is to pull the scapulae laterally and facilitate access to the posterior rib angles above T7 (see Figure 44–5).

Under aseptic conditions, the block sites are identified. Rib counting, if required, can be achieved by starting from the twelfth rib, or from the seventh rib, which is the lowest rib covered by the inferior tip of the scapula. The inferior edges of the ribs to be blocked are marked just lateral to the lateral border of the sacrospinalis (paraspinous) muscle group (usually 6–8 cm from the midline at the lower ribs and 4–7 cm from the midline at the upper ribs), corresponding to the angles of the ribs. Next, palpate the inferior borders of the ribs to be blocked and mark them, (see Figure 44–5).

The sites of skin entry are infiltrated with a small volume of lidocaine 1–2%. A site of entry is well-placed when a needle introduced through it at 20 degrees cephalad (sagittal plane; see Figure 44–6) just scrapes underneath the inferior border of the rib and reaches the subcostal groove. The skin is first drawn cephalad with the palpating hand by about 1 cm, and a 4- to 5-cm, 22- to 24-gauge (for single-shot injection), short-beveled needle is introduced through the chosen entry site at a 20-degree cephalad angle with the bevel facing cephalad. The needle is advanced until it contacts the rib (at a depth of less than 1 cm in most patients). A small amount of local anesthetic may be injected to anesthetize the periosteum. With the palpating hand holding the needle firmly and resting securely on the patient's back, the injecting hand gently walks the needle caudally while the skin is allowed to move back over the rib (Figure 44–7). The needle is now advanced 3 mm, still maintaining the 20-degree tilt angle cephalad (even a slight caudad-pointing angle by the needle greatly reduces the chance of success). A subtle “give” or “pop” of the fascia of the internal intercostal muscle may be felt, especially if a short-beveled needle is used. As the average distance from the posterior aspect of the rib to the pleura averages 8 mm, advancement of the needle much beyond 3 mm increases the risk of pneumothorax.5

Paresthesia, although not actively sought, confirms needle placement. Radiologic guidance is advised for neurolytic blocks. At this point, on negative aspiration for blood, 3–5 mL of local anesthetic is injected. For a single ICNB, it is desirable to block at least one ICN cephalad and one caudad because some degree of overlapping innervation from adjacent ICNs is common. To ensure that the tip of the needle remains in the optimal location, unaffected by hand and chest movement, some clinicians prefer to connect an extension tubing between the needle and the syringe and have an assistant perform the aspiration and injection.

When repeated injections at multiple levels are desired, patient comfort, the increased risk of complications and convenience become important issues, and a continuous ICNB should be considered. The technique is the same as for a single-injection block except that a Tuohy 17- or 18-gauge needle (in adults) is used to facilitate the placement of a catheter. The site of entry should be the intercostal space midway between the dermatomes to be blocked. By orientating the bevel of the Tuohy needle medially or laterally, the epidural catheter is directed medially or laterally, respectively. A catheter tip threaded medially by 3 cm would effect a paravertebral block; the local anesthetic injected can spread to the adjacent spaces involving three to five intercostal spaces in total if sufficient volume (eg, 20 mL) is used. In contrast, solution injected via a laterally directed catheter tends to stay mainly in the same intercostal groove. A lesser degree of spread may be possible because the intercostalis intimus muscle is flimsy, and local anesthetic can pass between the separate fascicles of that muscle to reach the subpleural space, from where it can spread between ribs and pleura to reach adjacent ICNs.5 It is usually difficult to thread a catheter much beyond 3 cm. Ability to pass a catheter beyond several centimeters suggests that the catheter may be within the pleura. It is also common for continuous intercostal block catheters to be placed under direct vision by surgeons at the end of a thoracotomy and before wound closure.6

Blockade of T1 through T7 is made more difficult because of the scapulae and the rhomboid muscles. Fortunately, few surgeries require blockade above T7. We prefer to perform a thoracic paravertebral block or an epidural blocks when high thoracic blockade is required.

ICNB, either single-shots or continuous, may actually result in injection of local anesthetic or catheter placement into the interpleural space or pulmonary parenchyma. Great ease of catheter insertion beyond 3 cm may suggest interpleural placement. Although analgesia may be provided with interpleural analgesia, it will not be the case with intraparenchymal injection.

• Needle: Single-shot: 20- to 22-gauge short-beveled 4- to 5-cm needle (adults)
• Catheter placement: 18-to 20- gauge Tuohy needle (adults)
• Syringe and needle for local infiltration
• Syringe with extension tubing
• Sterilizing and resuscitation equipment and drugs, drapes, marking pen, pillow, portable fluoroscope (for neurolytic blocks)

The choice of local anesthetic for single-shot ICNB includes bupivacaine 0.25–0.5%, lidocaine 1–2% with epinephrine 1/200,000–1/400,000, and ropivacaine 0.5–0.75%. Three to 5 mL of local anesthetic is injected at each level during a multiple-injection ICNB. The duration of action is usually 12 ± 6 h. Addition of epinephrine to bupivacaine or ropivacaine does not significantly prolong the duration of block, but may slow the systemic absorption and increase the maximum allowable dose with a single shot by 30%.4 Maximum bupivacaine dose is 2 (for plain solution) to 3 (with epinephrine) mg/kg/injection (total at one time)7 and 7–10 mg/kg/day. Maximum lidocaine dose is up to 5 (for plain solution) and 7 (with epinephrine) mg/kg/single injection7 and 20 mg/kg/day. Volunteers have been found to tolerate 30% more ropivacaine than bupivacaine before neurologic symptoms develop.8 The maximum single injection dose for ropivacaine is 2.5 mg/kg (for plane solution) and 4 mg/kg (with epinephrine),7 and the daily dose should probably be <9–12 mg/kg/24 h. The maximum single injection of epinephrine in stable patients is 4 mcg/kg. Depending on the volume of local anesthetic required, a 1/400,000 instead of 1/200,000 concentration of epinephrine may be chosen. Richly supplied areas favor rapid local anesthetic absorption, and the blood levels of local anesthetics after ICNB are higher than for any other regional anesthetic procedure. As such, it is advisable to leave a safety margin between the doses given and the maximum recommended dosages, especially in young children, the elderly, debilitated patients, and those with underlying cardiac, hepatic, or renal impairment. For continuous infusion, patients can usually tolerate a gradual build-up of the plasma local anesthetic level better than acute rises. An apparently safe regimen is a loading dose of 0.3 mL/kg followed by an infusion of 0.1 mL/kg/h of either bupivacaine 0.25% or lidocaine 1%.5

The foremost concern in a patient without an ipsilateral tube thoracostomy is pneumothorax, the rate of occurrence of which, as detected by chest radiograph and not necessarily accompanied by signs and symptoms, is well below 1%. Tension pneumothorax and the subsequent need for tube thoracostomy is rare. The risks of pneumothorax and lung injury, however, are increased in patients who have had previous chest surgery. If an asymptomatic pneumothorax is detected, the best management is observation, reassurance, and, if necessary, supplemental oxygen.

The peritoneum and abdominal viscera are at risk of penetration when lower ICNs are blocked, and the incidence should not be greatly different from that for pneumothorax.

Absorption of local anesthetic from the intercostal space is rapid. Peak arterial plasma concentration develops in less than 5 to 10 min, and peak venous plasma concentration peaks several minutes later. Because of this, toxicity is always a concern with multiple or continuous intercostal injections. Sometimes the dilemma comes when a frail elderly patient has multiple fractured ribs. The concern over systemic anesthetic toxicity may at times necessitate the use of a different regional technique.

Finally, as the dural sheath can extend up to 8 cm laterally, there is a slight risk of spinal anesthesia after an ICNB.

ICNB is a very satisfying block for both the clinician and patient because it is technically easy to perform and effective in the controlling pain involving the thorax and upper abdomen. It avoids many of the problems associated with central neuraxial blocks. Although there is the risk of pneumothorax and local anesthetic toxicity, these can be reduced with good technique and due consideration given to the maximum allowable drug dose and the patient's clinical condition. The proper use of this technique includes balancing its advantages and disadvantages against those of alternative techniques such as epidural and thoracic paravertebral block.