Chapter 62. Peripheral Nerve Blocks for Outpatient Surgery

The development of ambulatory surgery and that of peripheral nerve blocks (PNBs) occurred over two separate historic timelines. The performance of outpatient or ambulatory surgeries commenced in the mid-1800s, and its utilization rapidly escalated throughout the next century. By 1980, 16.3% of all surgeries were performed on an outpatient basis. By 1984 this number rose to 30% and the Society for Ambulatory Anesthesia (SAMBA) was born. The total outpatient rate approached 50% by 1990, 60% in 1997, and may have hit 70% in 2003.1,2 During the same span of time, techniques for PNBs were also being discovered. The decades from 1884, (when Koller and Brettauer first instilled ocular cocaine in Heidelberg, Germany3) to 1912 and 1914, (when Kappis and Heidenhein described the interscalene block,4) marked the birth of PNBs. Despite the coexistence of both ambulatory anesthesia and PNB techniques for over a century, they were not typically used concurrently.

As ambulatory surgery acquired today's popularity and widespread use, the scope of surgical procedures similarly expanded to become more invasive and pain-inducing. Suddenly, physicians were faced with a dual challenge: provide short-acting anesthesia thus achieving home-readiness within hours of surgery, concurrent with long-acting postoperative analgesia permitting the patient to remain discharged to the home environment. The differences between these dual desires have proven irreconcilable with modern opiate analgesia. This has been recently documented by Apfelbaum and colleagues, who quantified the shortcomings of ambulatory analgesic regimens. They found that 78% of those queried had felt pain of moderate (52%), severe (22%) or extreme (7%) intensity.5

In response to ambulatory anesthesia's dilemma, PNB techniques offer solutions ideal for an outpatient anesthetic: site-specific surgical anesthesia and a decreased dependency on general anesthesia (GA). In so doing, PNBs buffer the response to surgical stress, better maintain functional residual capacity, defend against loss of immunologic function, and avoid or shorten the period of postoperative ileus.6 By providing effective analgesia, PNBs can reduce patient exposure to opioids and their side effects. This allows for a more rapid discharge of satisfied patients to their home environment, resulting in cost savings for the ambulatory surgery center. As a cornerstone of multimodal analgesia, PNBs with long-acting local anesthetic (LA) help reduce patient readmission for pain or other side effects. Extending the effect of LA through continuous peripheral nerve blocks (CPNBs) further lengthens the period of low side-effect postoperative analgesia in the home environment.

Despite the advances in PNBs and CPNBs, these techniques remain underutilized skills in ambulatory anesthesia. As recently as the year 2000, Dexter and Macario7 revealed that ambulatory surgeries utilized regional anesthesia in only 8% of cases. A 1997 survey by Hadzic and coworkers found that although 98% of anesthesiologists used some regional techniques, less than half of respondents placed at least five PNBs per month.8 A 2001 survey by Klein and colleagues concurred that although interscalene, axillary, and ankle blocks were performed more often, major conduction PNBs of the lower extremity were not commonly employed. Further analysis indicated that 85% of anesthesiologists discharged patients with long-acting PNBs of the three aforementioned types, but only 36% were willing to place a long-acting femoral nerve block. Many factors contribute to avoidance of long-lasting PNBs including fear of patient injury or self-care deficits at home, logistical issues related to the time needed for performance and onset of the PNB, as well as unfamiliarity with techniques.9 Concerns regarding unfamiliarity with techniques will persist as long as inadequacies exist in resident education.10–12 But the issues of perceived outcome benefits versus risks, time required for PNB performance, and PNB reliability will likely remain the deciding factors in its use for outpatients. Regardless of the reason, the result remains the same: outpatient PNB remains a vastly underutilized technique. The real history of PNB and ambulatory surgery remains to be written.

Several factors, both negative and positive, aid the anesthesiologist in excluding or selecting an ambulatory patient for a nerve block. The primary absolute negative factor is patient refusal of PNB. Assuming acceptance of the technique however, patient selection depends on benefits outweighing the risks to patient safety during placement of the block and, secondarily, on patient safety after discharge with an insensate extremity. Primary patient exclusion begins with a stated allergy to LA. Another reason to reconsider PNBs involves deep or noncompressible nerve block sites in a sufficiently anticoagulated patient. Although central neuraxial blockade can certainly be used in patients receiving a variety of anticoagulants,13 the rules governing its use are likely too stringent to be applied to all PNB techniques. If a patient can accept the traumatic risk of an elective direct laryngoscopy, they can likely also weather the risk of a femoral nerve block from an experienced operator.

Immunologic concerns warrant exclusion if an infection is present at the nerve block site. Patients with sever pulmonary disease are not often scheduled to have procedures in an ambulatory facility, however, moderate to severe chronic obstructive pulmonary disease (COPD) in a patient warrants cautious consideration prior to selection of paravertebral block (PVB) or brachial plexus blockade. Although PNB techniques offer potential benefits over GA and narcotic analgesia, the consequences of pneumothorax and phrenic nerve paralysis must be weighed cautiously. Another screening consideration surrounds the patient with nerve injury. This is especially true in patients with either a worsening or improving nerve deficit that is under consideration for blockade. Although the literature provides no evidence that administration of PNBs in patients with preexisting neuropathy carries a risk of worsening the neurologic deficit, the complexity of the management and neurologic follow-up of these patients may outweigh the benefits of nerve blocks. Central nervous lesions can also cause anxiety in the consideration of peripheral block. Some advocate steering clear of patients with fluctuating central lesions like multiple sclerosis to avoid perceived liability surrounding the patient's natural disease progression; these opinions are not substantiated in the literature, however. The final consideration of acute risks versus benefits applies not to patient physiology, but to the environment in which the PNB is placed. If it is to occur outside of the operating room, standard American Society of Anesthesiology monitors, suction, oxygen and resuscitative gear and medicines are required. More information on application of regional anesthesia in patients with coexisting disease can be found in Part VIII of this textbook (Regional Anesthesia in Patients with Special Considerations).

After excluding patients in whom the immediate risks outweigh potential benefits of PNBs, concerns still remain regarding patient safety after discharge home with an insensate extremity. However, concerns of rendering the patients immobile in their home environment can be abated by the well-developed social support network that usually surrounds this subset of patients. In sharp contrast to these patients would be the patient with a weak nonoperative leg who has received a lower extremity block. Lower extremity block must also be carefully weighed in the morbidly obese, the frail elderly, and the patient with Parkinson disease because they are at a higher risk of falling. Postoperative surgical issues occasionally intrude on selection of long-duration PNB with the need for functional nerve assessment.

Conversely, PNBs should be actively encouraged for patients about to undergo an invasive or extensive surgery on an extremity, such as open joint reconstruction or replacement, osteotomies, tendon transfers, fracture repair, or manipulation of arthrofibrosis. PNBs should also be sought for patients with chronic pain conditions and opioid tolerance to aid them in management of postoperative pain. Patients with complex regional pain syndrome (CRPS) have demonstrated a pattern of abnormal nerve healing and are prone to redevelopment of CRPS in the operative extremity. Regional anesthesia has been shown to be beneficial in preventing a recurrence when clonidine is used with intravenous regional anesthesia (IVRA) or when the most proximal and sympatholytic PNB is employed.14,15 PNBs can also be of great benefit for patients undergoing surgeries that are particularly emetogenic, such as mastectomy, or for those with histories of postoperative nausea and vomiting (PONV) or opioid intolerance. Long-acting or continuous PNBs can also help patients avoid other side effects of opioids. Respiratory depression can be avoided in the COPD patient, and ileus or constipation can be limited after herniorrhaphy. Regional anesthesia (RA) can help prevent the need for airway manipulation in patients with asthma. PNBs can reduce surgical blood loss,16 assuaging concerns of the anemic or Jehovah's Witness patient. A final (and controversial) benefit also exists in using PNB to help the anesthesiologist sidestep the issue of an anticipated difficult airway.

Interscalene Brachial Plexus Block

Interscalene PNB anesthetizes the brachial plexus, typically at the C6 nerve root. The popularity of this block relates to its utility in providing long-lasting analgesia after painful ambulatory orthopedic shoulder surgery. When Hadzic17 compared interscalene block to GA in 50 patients for outpatient rotator cuff surgery, he found that patients with PNB had more frequent postanesthesia care unit (PACU) bypass (76% vs 16%), suffered less pain, ambulated earlier, met discharge criteria sooner (123 min vs 286 min), had fewer unplanned readmissions (0 vs 16%), and were more satisfied with their care. Brown coworkers18 found similar results and fewer postoperative side effects after interscalene block versus GA (pain 14% vs 45%, PONV 8% vs 43%, urinary retention 0% vs 25%, hospital admissions 17% vs 48%). In a large retrospective review comparing interscalene block with GA, D'Alessio and colleagues19 further demonstrated reductions in nonsurgical intraoperative time (29 ± 9 min vs 49 ± 12 min) and PACU time (72 ± 24 min vs 102 ± 40 min), as well as decreased anesthetic side effects in PACU.

Al-Kaisy's group20 prospectively compared interscalene block with 10 mL 0.125% bupivacaine against placebo for outpatient shoulder arthroscopy done under GA. They found decreased pain and morphine use (2.7 ± 2.6 mg vs 9.5 ± 5.2 mg) during the PACU stay and a faster achievement of discharge criteria (139 ± 34 min vs 193 ± 59 min) with the nerve block. They also noted no difference between patient groups in their 24-h opioid use following PNB resolution at 2 h. In a similar study, Laurila and associates21 compared a low-volume interscalene block with a subacromial bursa block and placebo. They also found the interscalene block to be the most effective for early postoperative pain control.

Singelyn and coworkers22 compared patients undergoing arthroscopic acromioplasty with interscalene PNB, isolated suprascapular nerve block, intraarticular LA, or systemic opioids. They concluded that interscalene PNB was most proficient, that suprascapular block was an alternative option, but that intraarticular LA injection offered no benefit to intravenous (IV) opioids.

Failure to achieve surgical anesthesia with interscalene PNB ranges from 0 to 9.5%,18–20,23 requiring conversion of 16% of cases to GA.18 Although side effects often include shortness of breath, dysphonia, and Horner's syndrome18,24 they rarely thwart discharge planning. More importantly, studies on inpatients have demonstrated a low risk of neurologic injury. In a series of 520 patients having single-injection or continuous interscalene block, Borgeat and colleagues25 found that 14% had paresthesia, dysesthesia, or nonsurgical pain 10 days after surgery. The majority of these symptoms gradually resolved, leaving only one patient symptomatic with a plexus injury 9 months after surgery. The combination of an efficacious PNB, its relatively benign clinical application, and demonstrated benefits compared with GA ensure ongoing use of the interscalene block.

Supraclavicular Brachial Plexus Block

The supraclavicular PNB approaches the brachial plexus trunks between the clavicle and the first rib. Due to the close proximity of the trunks at this level and the close apposition of the surrounding fascia, the supraclavicular block can provide more reliable anesthesia with faster onset distal to the shoulder than the axillary approach. Bedder and associates26 showed that supraclavicular block using 0.5% bupivacaine provided onset of sensory anesthesia in 4.0 ± 1.2 min and peak effect in 17.7 ± 1.8 min. Consequently, supraclavicular block is ideal for rapid-turnover outpatient procedures of the elbow, wrist, and hand. Because the axillary nerve may be spared with this PNB, supraclavicular block is not always reliable for shoulder surgeries.27 With the supraclavicular block, the needle insertion site is near the dome of the lung. Anecdotal reports have associated the “plumb-bob” technique with an unacceptably high risk of pneumothorax, leading many practitioners to avoid this block. Nevertheless, no study supports this concern or warrants prolonged observation of a patient after an uneventful anesthetic and recovery. To the contrary, Franco and Vieira28 demonstrated the safety of supraclavicular PNB in a series of 1001 patients anesthetized by both consultants and residents. Touting a clinical efficacy of 97.2%, no major complications were reported. These data highlight the potential usefulness and safety profile of this as yet underutilized technique.

Infraclavicular Brachial Plexus Block

Infraclavicular PNB is approached at the division and cord level of the brachial plexus. PNB at this level provides anesthesia appropriate for procedures done on the mid to distal upper extremity. As with supraclavicular PNB, this block has a high success rate and a low risk of pneumothorax.29–31

Hadzic and coworkers32 contrasted patients who underwent ambulatory wrist surgery with GA with those who received infraclavicular PNB. As a group, those patients with GA had lower PACU bypass rates (24% vs 76%), higher rates of PONV (32% vs 8%), and more numerous requests for analgesia (48% vs 0%). Fewer patients in the infraclavicular group reported inability to concentrate in the PACU (8% vs 56%), though statistical significance was lost by the time that discharge criteria were met. Although the infraclavicular block performed in the operating room prolonged induction by 5 min, total operative time was similar to GA. Discharge criteria were met more quickly in the PNB group (100 ± 44 min vs 203 ± 91 min), and opioid use was similar in both groups over the first 48 h.

Desroches33 used infraclavicular PNB to achieve surgical anesthesia in 91% of outpatients and required 7 min or less for block execution. The risk of pneumothorax remained low at 0.7%, although published rates of vascular puncture can be as high as 17%.34 The newer techniques with needle redirection laterally should reduce the risk of pneumothorax to practically negligible.

Axillary Brachial Plexus Block

The brachial pulse allows for facile location of the axillary artery and the common sheath that invests the branches of the brachial plexus. This reliable landmark, the low risk of pneumothorax, and the usefulness of this PNB for surgical anesthesia of the mid to distal upper extremity has helped to make the axillary block the most popular PNB in the United States.8,9 Axillary PNB can be successfully executed with a nerve stimulator, paresthesia, or the transarterial technique.

Septa within the fascial sheath35,36 may limit the rate of diffusion of LA to terminal nerves and result in individual nerve sparing. This can in turn lead to nerve sparing as well as delayed anesthetic set-up. In an attempt to overcome this problem, the stimulation and injection of individual nerves has been studied.37 Bouaziz and associates38 attempted to make an additional improvement in outcome by utilizing 0.5% bupivacaine to anesthetize the ulnar and median nerves and 2% lidocaine for the others. This strategy resulted in long-lasting anesthesia of a palmar incision with faster recovery of the remaining arm. Koscielniak-Nielsen and coworkers39 investigated success and patient perceptions using multiple-stimulation in unmedicated outpatients. They found that electrolocation was uncomfortable for 80%, but that 98% would have the same technique in the future. Thirteen percent would request sedation in the future, and 95% were comfortable being discharged with an insensate extremity. Despite this success, although block performance only took an average of 9.8 min, block onset took an additional 23 min using a 1:1 mixture of 0.75% ropivacaine and 2% mepivacaine. Utilization of a preoperative “block room” can eliminate the delay of LA set-up, decrease nonsurgical operating room time, and improve overall efficiency.40,41

Outpatient axillary PNB is not without the risk of block failure or complication. Davis and colleagues42 reviewed 530 such blocks and found a 7% incidence of block failure requiring GA and a 2 % incidence of inadequate postoperative analgesia requiring admission. Complications were rare, with a less than 1% incidence of LA toxicity and no persistent neurologic deficits. Cooper's group43 reviewed the anesthetics of 1149 outpatients and found that 93% of those who responded would have an axillary block in the future. Those who were reluctant to have another block were more likely to have experienced any side effect (ie, bruising or pain in the axilla).

Chan and coworkers44 prospectively compared axillary block with IVRA and GA in 126 individuals having outpatient hand surgery. The RA groups required less opioids and had a decreased incidence of PONV (p < 0.05). But the induction time, overall discharge time, and cost were least in the IVRA group (p < 0.05).

Iliohypogastric–Ilioinguinal Nerve Block

The iliohypogastric (T12, L1) and ilioinguinal (L1) nerves provide sensory innervation to the inferior abdomen and buttocks, the superomedial thigh, and part of the external genitalia. Block of these nerves is easily and efficiently performed 2 cm medial and 2 cm superior to the anterior superior iliac spine. Alternatively, the surgeon can apply LA to the nerves directly during an inguinal hernia repair. In the literature, the iliohypogastric–ilioinguinal nerve block has been used successfully as an adjunct to GA in surgeries such as inguinal herniorrhaphy and varicocelectomy.45 When compared with placebo,46 local wound infiltration,47 subarachnoid block (SAB),48 or GA alone,48 ilioinguinal–iliohypogastric nerve block has been associated with decreases in postoperative pain scores,46–48 postoperative opioid requirements,46,47 PONV,48 cost,48 and discharge times.48 Complications with this nerve block are usually related to the proximity of these nerves to the femoral nerve. Inadvertent femoral nerve block49,50 can result in difficulty with ambulation and may be difficult to differentiate from direct surgical trauma to the nerve. Overall, although data demonstrate its usefulness as an adjunct for hernia surgery, the magnitude of benefit seen may not support its routine use when compared with the simple alternative of surgical wound infiltration and multimodal analgesia.

Lumbar Plexus Block

The lumbar plexus block anesthetizes the femoral, obturator, and lateral femoral cutaneous nerves more reliably than more distal approaches to the femoral nerve.51 Although lumbar plexus block is useful for procedures that range from hip52 to knee53–55 arthroplasty, the expansiveness of this block may be disadvantageous to outpatients unless a short-acting local anesthetic is used (eg, chloroprocaine). Loss of iliopsoas muscle function prevents flexion at the hip and increases the difficulty of ambulating with crutches or even a walker. Furthermore, there exists a risk of epidural spread of LA, ranging between 1.8% to 8.9%.56,57 This may be caused by injecting LA too medially after eliciting the muscular response of a single nerve root. Such a mishap may prevent a patient from walking and delay discharge when long-acting local anesthetics are used.

Knee arthroscopy remains a commonly performed ambulatory surgical procedure for which lumbar plexus PNB may be useful. Two randomized prospective trials compared lumbar plexus PNB with SAB or GA for this procedure. Jankowski and associates58 found that more than twice the number of GA patients (45%) required analgesics in PACU versus those who received lumbar plexus PNB (21%) or SAB (14%). Although pain scores were higher at all points in the GA group, because mean scores were low even in this group they questioned whether lumbar plexus block was really necessary for this procedure. Hadzic and coworkers59 presented compelling support for a lumbar plexus block and sciatic nerve block over GA for knee arthroscopy. By utilizing lumbar plexus and sciatic PNBs they were able to decrease severe PONV from 62% to 12%, odynophagia from 60% to 28% and time to achieve discharge criteria from 205 ± 94 min to 131 ± 62 min. The percent achieving PACU bypass increased with PNBs from 24% to 72%. Although PNBs (placed in the operating room) lengthened the time required for induction by 7 min, there was no overall increase in length of time spent in the operating room.

Femoral Nerve Block & Fascia Iliaca Block

Anesthesia of the proximal lower extremity including the anterior knee and medial calf can be achieved with a femoral nerve block or a fascia iliaca block. Both of these PNBs can be performed on a supine patient with easily identified landmarks. Because anesthesia of the lateral femoral cutaneous and obturator nerves are often desired in addition to femoral block, individual anesthesiologists have attempted to increase LA volumes and to apply distal pressure to achieve these ends.60 The “3-in-1” technique, however, fails to consistently block the lateral femoral cutaneous and especially the obturator nerve.51,61–63

Femoral PNB has been employed for knee arthroscopy with varying success.64,65 More impressive results have been obtained for painful procedures, such as anterior cruciate ligament (ACL) reconstruction. Mulroy and coworkers66 compared femoral PNB to sham block in 55 patients who had already received either epidural or intraarticular analgesia after ACL repair. Overall, the best analgesia was seen in patients with femoral PNB, whereas half of patients in the sham group reported pain VAS ≥5/10. Furthermore, a trend of lower opioid use over 36 h was identified. This was substantiated in a retrospective study by Williams and colleagues,67 who found that outpatients garnered some benefit from femoral PNB for minor knee surgery but large benefit from more invasive procedures. Not only did femoral PNB provide improved analgesia in these individuals, it also reduced unanticipated hospital admissions. Further analysis found that the addition of sciatic PNB for invasive knee surgery augmented those advantages. Of note, without PNBs, invasive knee surgery held a four to six times greater risk of the patient being admitted to the hospital. In a more recent study,68 this group estimated the cost savings afforded by PNBs for ACL repairs. Assuming a PACU bypass rate of 82% and an unplanned admission rate of 4%, their institution would save $98,600 after 250 procedures.

When femoral PNB is used for minor knee surgery, such as knee arthroscopy, it has been shown that providing broader coverage of the lumbar plexus is beneficial. Bonicalzi and Gallino69 increased femoral PNB volume from 10 to 20 mL in an attempt to broaden “3-in-1” coverage, which resulted in better operative conditions and decreased postoperative discomfort. Patel and coworkers65 divided knee arthroscopy patients into those receiving GA, combined femoral and lateral femoral cutaneous PNB, and femoral PNB with sham lateral femoral cutaneous block. Again, operative conditions were improved, and postoperative complaints of pain decreased (from 27% to 3%) with broader nerve block coverage.

Although PNB of the femoral nerve group remains an effective mode of anesthesia for knee surgeries ranging from knee arthroscopy to ACL reconstruction, arguing its use for less invasive surgeries of the knee on grounds of postoperative analgesia alone is difficult. For more invasive lower extremity surgeries, however, the studies do warrant as broad an application of LA to this nerve group as can be reasonably afforded.

Proximal Sciatic Nerve Block

Proximal blockade of the sciatic nerve proves a useful adjunct to PNB of the thigh. Several studies have evaluated the utility of combined PNBs for knee arthroscopy. In one such investigation, Sansone and colleagues70 utilized combined femoral–sciatic nerve block in 601 patients and were required to provide further intraoperative pain relief only 12% of the time and sedation 20% of the time. Out of this group, only 0.7% required conversion to GA. No neurologic deficits were revealed at 1 month's follow-up.

Other studies have demonstrated effective use of a femoral–sciatic nerve block for knee arthroscopy but failed to show a prolonged analgesic benefit from mepivacaine compared with “fast track” GA71 and unilateral72 or bilateral73 SAB. When compared with propofol–remifentanil GA, the femoral–sciatic nerve block group had less intraoperative bradycardia (0% vs 21%) and hypotension (0% vs 36%) as well as lower postoperative pain VAS scores in PACU (0 vs 7 out of 10). However, 12% of patients receiving femoral–sciatic block complained of mild pain during surgery, one patient required fentanyl and one a GA. Addition of a sciatic nerve block to a femoral or lumbar plexus nerve block likely provides better tourniquet anesthesia than femoral or lumbar plexus nerve block alone. This may be useful for the patient who requests little or no intraoperative sedation.

Similar to the data discussed with femoral nerve blocks, the analgesic benefit from combined femoral–sciatic nerve block is more apparent when more invasive procedures are performed with long-acting LA.67 Nakamura and colleagues74 compared recipients of GA (n = 36) to patients who underwent femoral–sciatic nerve block (n = 31) for ACL reconstruction. The combined PNB allowed 90% of patients to avoid hospitalization postoperatively, and as a result saved $2,907 per patient.

Distal Sciatic Nerve Block

Both proximal and distal sciatic nerve blocks have broad application for foot and ankle surgery. Utilization of a more distal PNB preserves the function of the hamstring muscle group. A more distal approach, however, typically necessitates the use of either a calf tourniquet or potent sedation in the presence of a thigh tourniquet. With either sciatic nerve block approach, a femoral or saphenous nerve PNB can provide anesthesia to the spared distal extremity territory of the medial calf or ankle.

Posterior75 or lateral76,77 popliteal fossa PNB interrupts sciatic conduction prior to the division of the tibial and peroneal branches of the nerve. Since this PNB is relatively safe and easy to perform with a high degree of patient satisfaction, it proves a model block for ambulatory surgery of the distal lower extremity.78

Reliability was demonstrated by Singelyn and coworkers,79 who investigated the posterior popliteal fossa sciatic nerve block with 1% mepivacaine or 0.5% bupivacaine in 507 patients having 625 blocks. Femoral nerve anesthesia was provided separately when needed. Surgical anesthesia occurred in 92%, supplemental analgesia was necessary in 5%, and GA in only 3% of cases. Discomfort associated with the block procedure was minimal in 89%, moderate in 9%, and severe in 2%. Of the 466 patients who rated their satisfaction with perioperative analgesia, 95% were completely satisfied, 4% expressed moderate reservations, and 1% expressed major reservations.

Although some in busy ambulatory practices find it challenging to achieve adequate popliteal fossa sciatic nerve block in a timely fashion, Fernandez-Guisasola associates80 have provided promising data comparing two LA solutions for outpatient foot and ankle surgery. They found rapid onset of anesthesia using either 40 mL of 0.5% ropivacaine (6.5 ± 5.1 min) or 1% mepivacaine (6.2 ± 3.7 min). As expected, sensory block following ropivacaine significantly outlasted that from mepivacaine (20.7 ± 6.2 h vs 6.5 ± 1.7 h).

The analgesic duration of a popliteal fossa sciatic nerve block can exceed that for an ankle block or wound infiltration, two alternative anesthetics for foot surgery. McLeod and colleagues81 compared popliteal fossa PNB with ankle block in 40 patients undergoing GA for foot surgery. Bupivacaine (20 mL of 0.5%) was utilized to provide postoperative analgesia. Both techniques proved to be efficacious, though popliteal fossa PNB yielded 1080 min of analgesia versus 690 min with ankle block. The same group77 further studied lateral popliteal fossa PNB versus subcutaneous infiltration of the wound with similar results lateral popliteal fossa provided 1082 min of analgesia versus 373 min with wound infiltration.

A novel use of popliteal fossa sciatic nerve block was described by Vloka and associates82 when they combined this block with a posterior cutaneous nerve block of the thigh for short saphenous vein stripping. This technique provided an acceptable alternative to SAB and was associated with fewer requests for analgesia in PACU (21% vs 64%), faster recovery (67 ± 10 min vs 122 ± 50 min in PACU), and earlier discharge (total time in hospital 222 ± 53 min vs 294 ± 68 min). Thus it appears, in principle as well as in practice, that preserved hamstring muscle function combined with dense postoperative analgesia allow for early mobilization of ambulatory patients and support the use of distal sciatic PNB in this setting.

Paravertebral Block

Dermatomal anesthesia of the thoracolumbar trunk can be achieved by injecting LA into the paravertebral space deep to the transverse processes to bathe the nerve roots after their exit from the intervertebral foramina. Performance of PVBs has provided anesthesia as well as postoperative analgesia for outpatient breast,41,83–87 inguinal hernia,88–91 and ileostomy revision surgery.92

Decreased opioid requirements and subsequent PONV are important benefits of PVBs when used for potentially emetogenic surgery. Klein and coworkers utilized PVB with 0.5% bupivacaine for hernia89 surgery and for mastectomy.41 After mastectomy, the PVBs served to reduce the number of patients requiring postoperative analgesia from 97.8% to 25% compared with those who received GA.87 Because the technique is typically performed as a “blind” technique, without the use of nerve stimulation, a clear endpoint is not always achieved prior to injection of LA. This may be the source of the published variability in rates of successful blocks.41,85,87 This variability, combined with the proximity of the needle tip to the lung, with consequent risk of pneumothorax (0–6.7%),41,83–87 warrants at a minimum operator experience with PVBs prior to routine use of this block in the ambulatory setting.

Although single-injection PNBs have numerous advantages, one limitation is the rapid resolution of the nerve block after an invasive surgery in a patient who may not have sufficient blood levels of opioids present for adequate ongoing analgesia. Wilson and coworkers23 followed patient's home course after interscalene block for shoulder surgery and found that one third experienced extreme VAS pain scores of 4 or 5 out of 5 and that 5.3% of patients contacted their surgical team because of unbearable pain.

In response to these concerns, there have been several case reports and a limited number of trials that reported using CPNB with outpatients. Rawal and associates93 first described an elastomeric balloon pump that allowed self-administration of LA at home. Subsequently, patients having upper94–100 and lower extremity101–103 surgery of varying invasiveness have been discharged home with CPNB. There has been an overall low incidence of reported neurologic side effects with this therapy in the inpatient setting,25 offering limited support to the progressive use of CPNB in the home environment. Despite the lack of extensive patient safety data, initial reports demonstrate that patients are indeed comfortable with home CPNB infusions.97

Rotator cuff repair is a common outpatient procedure often felt to justify placement of an interscalene brachial plexus catheter. Compared with interscalene brachial plexus infusion of saline, opioid requirements have been diminished by 50%97 and analgesia sustained for as long as 4 days.104 Concurrently, other measures of comfort (pain scores, satisfaction, and fragmented sleep) have been consistently favorable.95–97

Similar success has also been reported with axillary100 and infraclavicular99 CPNB after hand surgery. Rawal and coworkers100 noted few technical problems and high outpatient satisfaction with the use of continuous axillary PNB after hand surgery. Similar analgesic success and limited motor block followed resolution of initial surgical anesthesia when both dilute bupivacaine (0.125%) and ropivacaine (0.125–0.2%) were infused through axillary and infraclavicular CPNB catheters.99,100

Perhaps the greatest effect of home CPNB has been for major lower extremity surgery such as ankle fusions, multiligament knee reconstructions, and forefoot procedures that historically have required a hospital stay for IV analgesia. A continuous popliteal fossa PNB has been shown to decrease the rate of hospital admission after foot and ankle surgery and to hasten discharge time while reducing pain and opioid consumption by up to 70%.102,103 Lumbar plexus and sciatic CPNB have also been utilized to enable multiligament knee reconstructions104 as well as to provide analgesia to reduce the length of stay for total knee arthroplasty (at our institution).

Establishment of an efficacious CPNB infusion necessitates an individualized regimen based on patient physiology and surgical procedure. Competing interests that affect this decision include the desire to provide quality analgesia, to avoid undesired motor blockade, to avoid LA toxicity, and to maximize the pump's LA reservoir to prolong the infusion duration. Differing strategies have involved intermittent boluses without basal infusion,93 basal infusion only,94,95,97 or basal infusion with intermittent patient-controlled bolus.96,99 While citing the need for ongoing research, a review by Ilfeld and Enneking105 concluded that a basal infusion (5–10 mL/h) decreased breakthrough pain and increased satisfaction, whereas a patient-controlled bolus (2–5 mL/20–60 min) allowed for a lower infusion rate and longer infusion time of the LA pump.

An area that requires further investigation is the proper treatment of the patient after discharge. Strategies to avoid patient injury, LA toxicity, and insertion site infection are essential. Several studies have advocated.

1. Careful catheter testing for intravascular placement prior to discharge

2. Patient and caretaker education (focusing on safety, pump function and complications)

3. Written instructions on extremity care and warning signs and symptoms of LA toxicity as well as appropriate analgesic expectations

4. Health care provider contact information to answer questions or problems

5. Daily health care provider contact by telephone to monitor side effects, determine efficacy, and follow the integrity of the insertion site, and

6. An individualized decision regarding at-home or in-hospital catheter removal.

Rigorous patient selection, education, and close follow-up have led to few adverse events with CPNB. A recent report from the US Food and Drug Administration,106 however, has drawn attention to problems with continuous wound infusions using disposable pumps in the home. They reported details on 40 adverse event reports, in which 15 patients developed surgical wound infections and 17 patients exhibited tissue necrosis, an extremely rare surgical complication. Although parallels from wound catheters cannot be extrapolated to CPNB, vigilance in this area seems warranted.

A variety of home infusion pumps are available that have improved accuracy, infusion pressure, and bolus capabilities, as well as larger reservoir volumes than previous models. Ilfeld and Enneking105 highlighted the major differences between commercially available models, including greatest infusion accuracy (electronic), patient bolus capability (some elastomeric and electronic), ease of depressing patient bolus button (electronic), programmability (electronic), disposability (elastomeric and some electronic), and price (variable). Audible alarms (electronic—previously noted to be detrimental due to a high false-alarm rate—may, with redesigned electronic pumps prove advantageous since elastomeric pumps cannot indicate an inability to deliver a set infusion rate.

Sedation is an intrinsic part of RA that helps ensure its success and popularity with patients. Patients often approach the operative theater with significant anxiety, which can influence their choice of anesthetic technique. Gajraj and colleagues107 found that fear of the needle (28%) and fear seeing or hearing operative events (10%) were cited by obstetric patients refusing RA. De Andres and associates108 also found anxiety in the awake patient significant in both the patient's preoperative attitude toward RA and as a predictor of use of regional anesthesia in the future. Fanelli and coworkers109 similarly found that a quarter of patients undergoing PNB would refuse PNB in the future due to discomfort during the procedure. Clearly, reassurance about the use of sedation and appropriate premedication is necessary to minimize pain and ensure patients' acceptance of PVBs.

A variety of pharmacologic agents can be used for sedation during block placement. Although any combination of agents can be employed successfully, it is important that the medications and their side effects are concordant with the following goals:

1. Patients should be competent to sign missing consent forms and participate in the marking of their operative extremity prior to block placement and surgery.

2. Pharmaceuticals should provide rapid onset of sedation and analgesia, the persistence of which should not preclude patient discharge.

3. Pharmaceuticals should be appropriately titratable such that the apneic threshold is not too easily breached.

4. They should minimize the risk of PONV.

5. They should be appropriately amnestic to satisfy patient desires.

6. They should not be too costly in comparison with their alternatives.

Pharmacokinetics and cost issues offer some bias for selecting midazolam, fentanyl, or alfentanyl as agents for block placement, although fentanyl is certainly emetogenic, particularly if repeated doses are given throughout the surgery. Keeping the fentanyl dose to a minimum (no more than 100 mcg) or substituting low-dose propofol is a viable strategy that can meet all of the previously mentioned goals. For intraoperative sedation, the ability to titrate, the antiemetic effect, and amnesia (with loss of consciousness) of propofol argue for its use.

Local Anesthetic Drugs

Choice of which of the commonly employed LA drugs to utilize is determined by safety profile, duration of action, and speed of onset. Since PNB for outpatients often occurs outside the auspices of a hospital setting, safety (avoiding toxicity, resuscitability after toxicity) is a primary concern. Choosing commercially available anesthetics based on safety profile provides a rank order of: lidocaine > mepivacaine > ropivacaine > bupivacaine. Because of the decreased margin of cardiac safety and increased difficulty of successful resuscitation, bupivacaine is no longer recommended as the first agent for ambulatory care.110,111

Of the remaining drugs, anticipated duration of action for anesthesia and analgesia when injected around a nerve or plexus and speed of onset is shown in Table 62–1.

The motor-sparing analgesia of ropivacaine makes it an ideal candidate for long-lasting ambulatory PNB as well as for home perineural infusions.

Postoperative Recovery

Depending on the depth and duration of intraoperative sedation, PACU bypass may or may not be feasible for patients who received PNB. Several scoring systems have been proposed to judge a patient's bypass eligibility. Of the reported systems, the White–Song criteria was not designed to accommodate PNB and allows bypass for transient vomiting or retching or IV control of moderate to severe pain if other scores are perfect.112 Accepting a modified Aldrete score of 932 (patients with PNB cannot move a blocked extremity) or a Mayo Modified Discharge Scoring System score of 8 or higher58 can successfully allow for PACU bypass, although neither of these systems address patient pain scores or PONV. Williams113 offers an alternative, similar to the modified Aldrete score, which demands at the outset no need for IV intervention (for pain, nausea, vomiting, pruritus, shivering, or hypotension/orthostasis) and no pain greater than 3 on a 10-point scale.

Multimodal Pain Management

The more methodologies employed to treat postoperative pain, the higher the chances of success and the lower the chances of significant side effects. The concept behind this approach to postoperative analgesia is known as multimodal pain management. With long-acting LA from PNB or CPNB as a basis for analgesia, acetaminophen and nonsteroidal antiinflammatory drugs (NSAIDs) can prove useful and inexpensive adjuncts. Even if surgical concerns about bone healing predominate,114,115 there is no evidence that a single dose of a potent NSAID alters bone healing outcomes. Although a minimal opioid dose may be needed for postoperative pain management after surgeries ranging from cyst removals to mastectomies performed under PNB, they are typically required for more invasive procedures. Avoiding formulations containing acetaminophen will avoid the ceiling restrictions it otherwise places on home opioid use and can maximize the benefits of a simple every 6-h dosing of acetaminophen and ibuprofen. Other strategies such as limb elevation and cryotherapy should be employed routinely. Deep-tissue electrical stimulation via electrodes placed under the dressings by the surgeons have also shown recent promise, though these devices should not be utilized until after PNB resolution.116 Written discharge instructions should be given to the patient, highlighting all of these points.

Discharge Criteria and Patient Instructions

Determining home readiness after ambulatory PNB involves meeting some extra criteria in addition to the standard checklist required of day surgery patients (normal vital signs, absence of moderate to severe pain, PONV, or bleeding). This is especially the case when the patient is to go home with a long-acting PNB. It remains controversial to shift responsibility for care of the insensate extremity to patients in their home environment. Extremity numbness theoretically increases the risk of injury from either a fall at home or from direct injury to the limb lacking protective reflexes. To date, large prospective studies of this issue have been few in number. Davis and colleagues42 succeeded in discharging 526 patients after axillary PNB with no subsequent injury. Our group117 prospectively followed 2382 ambulatory patients who had received ropivacaine PNB to either an upper or lower extremity. One patient in this group did fall while exiting his car, but he did not sustain an injury. Seven patients from this group (0.29%) developed a new paresthesia in the operative limb that could have been anesthesia-related. These studies suggest that proper education of patients prior to discharge with an insensate extremity can help avoid most if not all problems.

It is postulated that the reason for such a safe track record relates to careful screening by anesthesiologists and explicit instructions reinforced by PACU staff. Patients must be educated not to use their insensate extremity, to pad and protect it, to visually inspect it, and to avoid direct skin contact with heat or ice. Patients with a lower extremity PNB must be instructed not to weight bear on an insensate limb, must demonstrate proficiency with the use of crutches or a walker, and must be able to iterate a plan for dealing with obstacles such as stairs. Those who are discharged home with a CPNB pump must live within a certain distance of the medical center (ie, –2 h), must have a caregiver present with them for the entire duration of LA infusion, and must be available for daily postoperative follow-up while the catheter is in use. They must be instructed to call immediately if the catheter site displays signs of infection, if the extremity exhibits signs and symptoms of compartment syndrome, or if the patient demonstrates any signs or symptoms of LA toxicity. Patients and their caregivers must be taught about catheter hygiene and care and catheter removal and be given detailed instructions about pump use, including how to stop the infusion.

The rapid expansion of surgical case variety and complexity has resulted in the inability of GA to provide quality care for all ambulatory patients. This has been evidenced by frequent readmissions for pain and PONV. In contrast, the successes of ambulatory PNBs referenced in this chapter support their emerging role. For upper extremity procedures, the use of PNB has demonstrated improved analgesia, faster patient discharge readiness, and decreased opioid-related side effects compared with that for GA. For surgery involving lower extremity procedures of greater complexity the benefits of dense analgesia from PNB become more apparent. The use of lower extremity PNB appears to be critical to same-day discharge and lower rates of readmission in patients undergoing more invasive same-day surgery on the lower extremity.

The use of multimodal analgesia with long-acting LA provides extended analgesic benefit. The addition of CPNB can significantly expand this benefit at home. However, the slow onset time associated with long-acting LA and the time needed to place continuous catheters can adversely affect ambulatory efficiency. Although effective strategies do exist to diminish this impact, timely administration of RA may still be challenging and represent an impediment to use in some institutions. Developing additional solutions to this obstacle will be important in broadening the use of PNB in the ambulatory population. Another potential impediment results from patient anxiety and apprehension regarding RA. Reassurance about the use of sedation for PNB placement and intraoperative course should alleviate this problem.

Selection of appropriate patients for PNBs and CPNBs and detailed discharge instructions are important for continuing the track record of safety with these techniques. Ongoing positive patient experiences with RA will beget future successes. Whether ambulatory anesthesiologists will be prepared for this success remains to be determined. Improvements in residency training and intensive workshops for current practitioners will likely be necessary to keep up with future demand for outpatient PNBs.