Chapter 61. Perioperative Management with Peripheral Nerve Block Anesthesia

Regional anesthesia offers multiple clinical advantages that contribute to both an improved patient outcome and lower overall health care costs.1–4 Peripheral nerve blocks provide excellent anesthesia, postoperative pain relief, reduced complications of wound healing compared with infiltration anesthesia, fewer side effects than general anesthesia, and facilitate early physical activity.5–8 Peripheral nerve blocks are frequently used in elderly patients to limit excessive sedation while providing excellent pain control.9 Nerve blocks are associated with reduced use of opioids for postoperative pain, fewer postoperative complications, and earlier discharges.6,10–12 Single-injection regional blocks and continuous peripheral catheters play a valuable role in a multimodal approach to pain management in the critically ill patient, providing excellent patient comfort while reducing the physiologic stress response.13

However, compared with neuraxial and general anesthesia, success with peripheral nerve blocks is undoubtedly more anesthesiologist-dependent.14–16 Technical skills and determination are required for the successful implementation of peripheral nerve blocks. Factors such as accurate identification of surface landmarks and an adequate number of supervised, successful attempts at each block are necessary for safe, effective peripheral nerve block implementation.14,16–18 A dedicated team of well-trained anesthesiologists is a prerequisite to ensure consistent peripheral nerve block service in any institution.19,20 Intraoperative management, once the block has been placed, requires diligent observation and judicious use of supplemental drugs for anxiolysis and sedation. Postoperative management, including patient and nursing education, discussion of the block duration, expected sensory and motor deficits, and a plan for pain management as the block diminishes, is the final element required for success with nerve blocks (Figure 61–1).

Even before the anesthesiologist meets the patient, planning for anesthetic management begins with a review of the operative schedule. Attention to the procedure, what portion of the patient's body is involved, the patient's name and age, and the surgeon's preference direct the anesthesiologist toward the choice of general, regional, or combined techniques. Knowing the surgeon's abilities plays a role in selecting both the block technique and the local anesthetic to be used if regional techniques are to be implemented. Advance planning includes placing equipment and supplies necessary for the chosen technique in the block area or the operating room (OR) prior to the patient's arrival, increasing the efficiency of the anesthetic experience.

Medical Record Review

The patient's chart should be reviewed for relevant history, physical examination findings, and laboratory studies that may influence the anesthetic plan. The chart review should be conducted with as much care as is taken with surgery involving general anesthesia. Laboratory tests, the electrocardiogram (ECG), tests of cardiovascular risk, radiographic reports, and any additional consultations should be reviewed.

Routine laboratory studies are not indicated for the low-risk patient undergoing low-risk procedures. Selective laboratory tests, such as hematocrit, coagulation profile, and blood urea nitrogen (BUN)/creatinine, should be checked in select, high-risk patients, when significant blood loss is expected, or in patients known to have been on anticoagulant therapy.21,22 Prolongation of the elements of the coagulation profile (prothrombin time, partial thromboplastin time, international normalized ration [INR]) can be a contraindication to neuraxial blocks, but specific peripheral nerve blocks may still be performed safely. Guidelines for the application of regional anesthetic techniques in the anticoagulated patient can be found in Chapter 70 (Regional Anesthesia in Patients on Anticoagulants). In general, blocks associated with a higher risk of bleeding because of proximity to major vessels or those that traverse major muscle layers may be performed 4 h after the last dose of subcutaneous heparin, 12 h after the last dose of low-molecular-weight heparin (LMWH), 7 days after clopidogrel (Plavix), and 4 weeks after the discontinuation of GIIa/IIIb inhibitors.23 Nonsteroidal antiinflammatory drugs (NSAIDs) and aspirin are not contraindications to block placement.

An ECG may be obtained and evaluated for high-risk patients or for those known to have cardiovascular disease.24,25 The ECG should be reviewed for changes suggestive of myocardial ischemia, infarction, new dysrhythmias, or conduction defects that may require additional evaluation prior to surgery.

Chest radiographs are usually not warranted for an asymptomatic patient without risk factors who is younger than 75 years of age.26 If a chest radiograph has been completed in a high-risk patient, it should be reviewed in the same manner as would be done prior to general anesthesia. The anesthesiologist must be cognizant of the fact that the co-administration of general anesthesia may be necessary.

The medication profile is important for alerting the anesthesiologist to the presence of drug allergies, the presence and treatment of disease, anticoagulation therapy, pain therapy, and chronic treatment states. Herbal and vitamin therapy should be reviewed, as some of these over-the-counter medications can affect the patient's response to medication as well as platelet function.27 Tobacco, illicit drug, and alcohol use should be included in the evaluation. For instance, the history of cocaine abuse may preclude the use of epinephrine in the solution of local anesthetics or dictate the use of direct-acting vasoconstrictors (eg, phenylephrine) in case of neuraxial anesthesia–induced hypotension.

Patient Selection

Any patient scheduled for surgery on an extremity should be considered a candidate for peripheral nerve block anesthesia.28–30 Regional anesthesia, alone or in combination with general anesthesia, is feasible and desirable in most surgical patients for almost any operative site. Factors such as the primary indication for surgery, the presence of coexisting diseases, potential contraindications, and the patient's psychological state should all be considered.31

Regional anesthesia can be particularly challenging in high-risk surgical patients undergoing orthopedic, thoracic, abdominal, or vascular surgery. Diabetics and the elderly benefit from the selective anesthesia provided by peripheral nerve blocks. The isolated vasodilation provided by sympathetic blockade in the operative extremity in the patient with severe peripheral vascular disease is of benefit to both the surgeon and the patient.32,33 Patients with asthma in whom airway instrumentation is best avoided are also excellent candidates for peripheral nerve block anesthesia.34

Obese patients, those with sleep apnea, confusion or delirium, and the elderly need special consideration. Regional anesthesia can be used with success in most of these patients; however, the risk/benefit ratio must be evaluated. Obesity provides a challenge to all forms of anesthesia, including intravenous access, identification of surface landmarks, airway obstruction with sedation, more rapid oxygen desaturation secondary to a reduced functional residual capacity, and difficult intubations.35,36 In an analysis of more than 9000 blocks, Nielsen and colleagues found that patients with a body mass index (BMI) of greater than or equal to 30 kg/m2 were 1.62 times more likely to have a failed block. Because other variables such as increased risk with general anesthesia, difficulty in alleviating postoperative pain, and unanticipated admissions, obese patients should not be automatically excluded from regional anesthesia procedures.37 Overall satisfaction with regional techniques has been similar to that for patients with a normal BMI.

Careful evaluation of the patient's overall health, the ability to handle surgery with minimal sedation (to avoid airway obstruction from heavy sedation), and benefits of regional techniques over general techniques can help the anesthesiologist to determine the best form of anesthesia.

Confused, demented, and disoriented or uncooperative patients present a particular challenge when regional anesthesia is considered. Although regional anesthesia can be performed in a comfortably sedated patient, these patients may require continued deep sedation throughout the operative period. Factors such as the patient's size, airway function, emergent vs nonemergent case (ie, full stomach), combativeness vs confusion should be considered when choosing the anesthetic technique. General and regional techniques have been compared in two large randomized trials in patients with preoperative mental status changes. In both groups, regional techniques were performed safely without significant differences in morbidity or cognitive function intraoperatively and postoperatively.39–41

As the population ages, the number of elderly patients presenting for anesthesia and surgery has increased exponentially. Regional anesthesia is frequently used in these patients because minimal sedation can be used for the procedure, and the patients receive excellent postoperative pain control. Factors specific to the elderly patient, such as coexisting disease, mental status changes, and type and duration of surgery, should be evaluated prior to instituting peripheral nerve blocks.9 Aging affects the pharmacokinetics and pharmacodynamics of local anesthetics. Changes in systemic absorption, distribution, and clearance of local anesthetics cause an increased sensitivity, decreased dose requirements, and a change in the onset and duration of action.42,43 Epinephrine can prolong the duration of the block, but it creates a greater risk of ischemic neurotoxicity in peripheral nerves of the elderly.44

Perhaps the only absolute contraindications to regional anesthesia are patient refusal, an active infection at the site of puncture, severe systemic coagulopathy, and a true allergy to local anesthetics (Figures 61–2 and 61–3).

Patient education by an informed anesthesiologist will nearly always assure a reluctant patient to consent to a block procedure. However, a patient adamantly opposed to regional blocks for whatever reason should never be coerced.45,46 True allergies to local anesthetics are extremely rare and have been found to be toxic responses or non–drug-related responses in the majority of the cases.47

Postoperative neuropathy may be difficult to assess in the presence of a peripheral nerve block performed with a long-acting local anesthetic. If the neurologic examination must be done immediately postoperatively, then a shorter-acting local anesthetic can be administered, thereby allowing the patient the choice of anesthetic techniques.42 Because of their lower potential for cardiovascular toxicity, shorter-acting, less toxic local anesthetics are also preferred in hemodynamically frail patients. In some patients or clinical scenarios when the level of anxiety is high concerning the neurologic outcome, general anesthesia may indeed be the most practical option instead of labor-intensive perioperative management and interaction with the rest of the medical team. Ultimately, the use of regional anesthesia in patients with preexisting neurologic disease is a matter of judgment and experience. For more in-depth discussion on this topic, the reader is referred to Chapter 59 (Regional Anesthesia in Patients with Neurologic Disease).

Patient Interview/Education

Patient education is vital to successful regional anesthesia. Among the general public and particularly the elderly, there is a common lack of awareness regarding the potential uses and benefits of regional anesthesia. Patients are commonly offered the choice between two overly simplistic descriptions of anesthesia options: “a needle in the neck” or “go to sleep.” Neither of these descriptions accurately describes the nature of the anesthetic care. Many patients, therefore, have a tendency to choose general anesthesia due to the lack of understanding of what regional anesthesia comprises and the anxiety over needle insertion during block performance. Another common misconception is that nerve blocks are associated with an increased risk of nerve injury. In fact, the data from the closed-claims studies suggest that the majority of reported neurologic complications are actually associated with general anesthesia due to problems with patient positioning.48

During the preoperative visit, the anesthesiologist should help the patient to understand the basics of the anesthetic management and to establish realistic expectations. The anesthesiologist must be personally convinced that the proposed technique is the best choice, or it will be difficult to provide assurance to the patient. Patients should be educated about the principal benefits of regional anesthesia—avoidance of general anesthesia and airway management, improved pain control, and reduced incidence of nausea and vomiting—all of which are evident immediately in the postoperative period.7,49

The patient should be informed about the duration of the blockade, the need for analgesic therapy as the block is wearing off, and the care of the insensate extremity. Informing patients about what to expect and helping them understand that incremental sedation or analgesia (“light sleep”) will be given before and during the procedure encourages most patients to consent to regional blockade. The amount of information given varies with each patient. It should be tailored to the patient's desire and the type of the nerve block procedure planned followed by obtaining the informed consent.50 A review of the patient's prior record of pain management, including chronic states and treatment, may alert the anesthesiologist to unrealistic expectations that the patient may have that should be addressed before premedication is administered. This will also alert the anesthesiologist that larger doses of sedatives or narcotics may be required for the patient's comfort.

Anesthesia Consent

A consent for anesthesia should be obtained before sedation is administered. This should include the proposed method of anesthesia, the benefits, risks, and complications of regional anesthesia specifically related to the patient. The consent should include the possibility of general anesthesia in the event that the regional technique is incomplete or ineffective, changes in the surgical plan surgical exposure, and patient comfort considerations. Many institutions have adopted specific anesthesia consent forms separate from those for surgery, although this practice varies depending on the institution. Regardless of the individual institution's consent practices, once the consent is signed, it is advisable to write a brief, specific note in the patient's chart that describes the discussion the anesthesiologist had with the patient. The note simply states whether any specific patient concerns were discussed. Here is an example of such note:

“An interscalene block for anesthesia was discussed with the patient. The risks, benefits, alternatives, and complications were discussed. Questions were answered. The patient expressed understanding of the proposed anesthetic plan, and the consent was signed.”

Such note is far more valuable as a medicolegal document that a proper consulting procedure took place than any preformated, institutional consent signed by the patient.

Surgical Considerations

An insightful and educated surgeon is often the greatest advocate of regional anesthesia. Patients undergoing various orthopedic, vascular, hand, and podiatric surgical procedures can be anesthetized using regional anesthesia techniques. Surgeons will quickly adopt and demand regional anesthesia to facilitate patient care when it is implemented in an efficient, consistent manner. Some surgeons, however, may have reservations about utilizing regional techniques until they are shown that OR efficiency can be increased, patient satisfaction enhanced, postoperative pain issues reduced or alleviated, and that favorable outcomes are associated with expertly performed regional anesthesia procedures.51,52 Surgeons who have accepted the value of regional techniques often introduce the techniques to their patients during the preoperative visit. However, an adequate number of the faculty in the anesthesia department must be trained in regional techniques in order to provide a continuous service and maintain the confidence of the surgical team and the patients.14,53

Preoperatively, a discussion with the surgeon about the proposed procedure is essential. The discussion must include considerations regarding the site, nature, extent, and duration of the planned surgical procedure. Issues such as patient positioning, field avoidance, and the use of a tourniquet should be discussed to make sure that the intended technique will be adequate and appropriate for the planned surgery and for the particular patient.

In general, procedures involving the upper body, head, and neck create more anxiety in many patients secondary to the claustrophobic effect of drapes and proximity of the surgical site to the patient's head. Adequate sedation without compromising airway protection will usually alleviate the problem if the anesthesiologist is prepared. When the surgical team has to surround the head, effectively blocking access by the anesthesiologist, in some instances it may be safer to secure the airway prior to proceeding with surgery.54,55

Anesthesiologist

The anesthesiologist's confidence and ability to establish a rapport with the patient are the most important factors for convincing a patient to accept the proposed anesthetic technique. Presenting the patient with a wide range of anesthetic options for the particular procedure is confusing for the patient. Instead, a better approach is to present the patient with the regional anesthetic plan that best meets his needs based on his physical and emotional status, coincides with the surgeon's plan, and is within the realm of the anesthesiologists expertise. As the number and complexity of regional anesthesia techniques keep increasing, it is becoming clear that regional anesthesia is a training-intensive and a distinct subspecialty of anesthesiology. Thorough training during residency is necessary to obtain consistent results and avoid complications.53,56 A well-structured regional anesthesia fellowship is by far the best path toward success in academic endeavor in this area.57,58

Physical Examination

Physical examination with assessment of the block site is essential to determining whether the block can be performed safely. For example, performing an interscalene block in a patient with severe chronic obstructive pulmonary disease could result in the need for mechanical ventilation due to hemidiaphragmatic paresis on the ipsilateral side.59 On the other hand, unhealthy patients requiring urgent or emergent surgery for lower extremity fractures clearly benefit from peripheral nerve blocks because general anesthesia in these circumstances would be poorly tolerated.60 Once the decision has been made to proceed with the regional technique, certain anatomic landmarks can be used to enhance the success of the block despite the physical habitus of the patient. The following paragraphs briefly describe physical examination clues to improve the success rate of some of the peripheral nerve blocks.

Interscalene Brachial Plexus Block

Evaluation of the neck is the key examination for the interscalene block. The proportions of the shoulder girdle, size of the neck, and prominence of the muscles vary greatly among patients. The three bony landmarks that should be observed are the sternal notch, the clavicle, and the mastoid process. Even in the obese or stocky patient with a short neck, these landmarks can be evaluated. In addition, locating the clavicular head of the sternocleidomastoid muscle and the external jugular vein are important in estimating the site for needle insertion. Even though the external jugular vein has a highly variable course, the interscalene groove is almost always immediately in front of or behind the external jugular vein.61 In patients with difficult anatomy, the clavicle and external jugular vein often prove to be the most reliable landmarks.62 In the patient with difficult anatomy (ie, short, thick neck), a single-shot interscalene block may be a better choice than attempting a continuous catheter technique. If it is difficult to locate the interscalene groove, transcutaneous stimulation can be used by employing a higher stimulus intensity and scanning the skin surface of the neck (Figure 61–4). Once the twitches are obtained, the current is decreased to the minimum at which the twitch is still observed. For this purpose, a nerve stimulator with higher current output is used (models made for monitoring the neuromuscular junction blockade). Commercial models made specifically for surface localization have also become available in recent years. This techniques provides a better idea of where the stimulating needle should be inserted. Where equipment and expertise is available, ultrasound-guided interscalene block may be a better choice.

Infraclavicular Brachial Plexus Block

Evaluation of the upper chest, clavicle, and shoulder area is important in performing the infraclavicular block. The primary landmarks are the coracoid process and the medial clavicular head. The most difficult process to identify, especially in an obese patient or a patient with a muscular chest, is the coracoid process.63,64 To find the coracoid process, follow the clavicle from the medial to the distal end. Toward the distal end, a groove or depression is felt just below the clavicle, the deltopectoral triangle or groove. Drop the fingers of the palpating hand into the groove, then abduct the shoulder (raise the arm in a forward position). As the arm is lowered, the coracoid process will be felt by the fingers of the palpating hand. Once the coracoid process is located, many of the techniques described to stimulate the brachial plexus using the infraclavicular approach can be initiated.65,66 If the patient has too much tissue in the upper chest area, another approach to the brachial plexus (eg, low interscalene approach) might be a better option.

In obese patients or those who have large chest muscles or breasts, it may be easier to perform this block in the semisitting position to “unload” the soft tissues using gravity and provide better access to the infraclavicular area. Of note, percutaneous stimulation as electroprelocation is often not useful in infraclavicular block due to the deep location of the brachial plexus at this point.

Axillary Brachial Plexus Block

The key physical examination finding is the location of the axillary artery. To find the axillary artery, the patient should be placed supine with the head facing away from the side to be blocked. On the side to be blocked, the shoulder should be abducted with the elbow flexed at a 90-degree angle. If the shoulder is excessively abducted, palpation of the axillary artery may be more difficult. Even in an obese patient, the axillary artery can be palpated if the shoulder and forearm are properly adjusted.14,67 When palpation of the axillary artery proves difficult, the use of a Doppler probe or ultrasound is useful. Similar to the interscalene block, transcutaneous stimulation can be used to approximate the position of the individual elements of the brachial plexus (Figure 61–5).

Blocks Involving the Spine: Spinal, Epidural, Plexus Blocks

It is not uncommon to see trainees who are evaluating patients before planned regional anesthesia perform extensive airway and other systemic examinations but pay no attention to the characteristics of the anatomy where the entire anesthetic will be administered (eg, spine). Evaluation of the spine preoperatively will allow the anesthesiologist to decide whether neuraxial anesthesia or a lumbar plexus block will prove easier to perform. In addition, such an examination will help the clinician to decide whether the patient should be placed in a supine or lateral position for a neuraxial block, or whether a different method of anesthesia is more appropriate. In the elderly patient, the evidence of severe kyphoscoliosis or arthritic changes in joints may direct the clinician to using the lateral paramedian approach for the block. In the obese patient, the midline approach may be the best for a successful block. Other examination findings of importance for regional anesthesia involving the spine include evidence of localized infection, scoliosis, and congenital defects or scars that may affect either the placement or the choice of technique.68,69

Blocks Involving the Lower Extremities

Physical examination of the groin and lower extremity should occur prior to implementation of nerve blocks of the femoral or sciatic nerves or their branches. It is pointless to obtain a patient's consent for a block procedure and discuss the anesthetic plan with the surgical team without examining the site of needle insertion because a local pathology can prevent the performance of the planned technique. The presence of infection, neuropathy, severe peripheral vascular disease, or trauma will guide the anesthesiologist to the best procedure for the patient. In a patient with vascular disease, the anesthesiologist should evaluate the lower extremity for scars that may indicate vascular grafts involving the femoral artery, a relative contraindication to femoral blockade. The area around the ankle should be evaluated for presence of disease, infection, excessive lipidema, or edema that may present a contraindication or make an ankle block impossible. Obesity can make palpating landmarks such as the femoral artery for a femoral nerve block or the quadriceps muscles for a lateral popliteal sciatic nerve block more challenging. Physical examination of the areas to be blocked allow alteration in the anesthetic plan (ie, a change from a lateral or subgluteus posterior approach to sciatic) or a change in equipment (ie, longer stimulating needle) to be made prior to instituting the block.70,71 Similar to the procedure for an axillary block, a Doppler probe can be used to facilitate localization of the femoral artery when palpation proves difficult. Retraction of the lower abdomen in morbidly obese patients can substantially facilitate the performance of the femoral block (Figure 61–6).

The goals of the anesthetic plan are to ensure that the patient is properly evaluated, (ie, the choice of the anesthetic technique is the best for the patient based on the surgical procedure), the patient's physical and mental status has been assessed, and that the patient will remain hemodynamically stable when her inherent protective reflexes are blunted or abolished. Additional considerations with regional anesthesia include providing adequate premedication, placing the block efficiently so as not to compromise valuable OR time, providing complete anesthesia for the surgical site, planning for an inadequate or incomplete block, and patient comfort during long procedures.72

Laterality Issues

Wrong-side anesthetic procedures have been reported in patients receiving peripheral nerve blocks, especially when the patient changes position for the block.73 Wrong-sided blocks probably occur more frequently than reported. Despite multiple checks, laterality errors can occur, particularly in institutions where large numbers of nerve blocks are performed. Risk factors that may contribute to these errors include delay between obtaining the patient's consent and the block performance, different anesthesiologists performing the block and managing the patient intraoperatively (resident “block rotations”), time pressure to administer the block without delaying surgery, and covering the patient's involved extremity with blankets to maintain warmth, effectively obscuring the marked site of surgery.

A rigid laterality protocol prior to the block placement should substantially reduce the risk of wrong-sided blocks. In our institution the following procedure is followed:

1. The surgical staff is required to mark the surgical site immediately prior to taking the patient to the OR using a wide marker and marking the site as “YES.”

2. Once the patient is in the OR, the surgical and anesthesia staff confirm the laterality with the OR nurse immediately on arrival in the OR.

3. Both of the patient's extremities are uncovered and examined for laterality prior to the block procedure.

4. A “time-out” for confirmation between two caregivers is required before block performance as well as before the surgical incision.

Fortunately, long-term sequalae after laterality errors typically do not occur, but there is an increased risk of performing surgery on the wrong side when the wrong limb is anesthetized. Careful attention to the surgical consent, the marked extremity, and following procedures to double-check the surgical site are important in preventing laterality errors in patients receiving peripheral nerve block anesthesia.

Premedication of Patients for Neural Blockade

Premedication is one of the essential elements for successful neural blockade, whether it is for neuraxial blocks or peripheral nerve blocks. Anxiety causes feelings of uneasiness, tension, and nervousness and has been associated with a higher degree of intraoperative movement and sedation requirements. Utilizing anxiolytic premedication does not delay hospital discharge and is associated with a greater degree of patient satisfaction.74,75 A patient's previous experience with regional anesthesia is a significant factor in acceptance of a regional technique for future surgery. Fear of needle puncture has been cited as a major cause for patient dissatisfaction or refusal of regional anesthesia.76,77 If a paresthesia technique is utilized for placement of a peripheral nerve block, less sedation is used as patient cooperation is necessary, but it should not be eliminated. When a nerve stimulator is employed for placement, a greater amount of sedation can be used for patient comfort.

Premedication with an anxiolytic should be administered preoperatively just as it is given prior to general anesthetics.78–80 In addition to the benefits mentioned, premedication prevents patients from having an unpleasant recollection of the anesthetic experience. Inadequately premedicated patients move during the block placement, making it difficult to interpret responses to nerve stimulation and possibly dislodge the needle from its intended position.

All peripheral nerve blocks can be divided into two major groups: blocks associated with minor patient discomfort (superficial blocks) and blocks associated with more patient discomfort (deep blocks). A sedation protocol should be chosen according to the regional anesthesia technique planned and according to individual patient characteristics. For instance, an interscalene brachial plexus block can be administered to a minimally sedated, fully alert patient. On the other hand, an infraclavicular, sciatic, or lumbar plexus block necessitates, for most patients, a greater degree of sedation and analgesia to ensure the patient's comfort and acceptance. Regardless of the sedation technique chosen, the goal of sedation is to provide maximum patient comfort while maintaining meaningful patient contact throughout the procedure.

The pharmacology of drugs commonly used for premedication in regional anesthesia is discussed in greater detail in Chapter 11 (Sedation–Analgesia During Local and Regional Anesthesia). The discussion here will be limited only to salient features of immediate relevance to the practice of regional anesthesia.

Midazolam is one of the most common anxiolytics used for premedication. Midazolam is effective given orally, intranasaly, sublingually, intramuscularly, intravenously, and as a continuous infusion.81 It has been used in combination with a variety of medications, such as narcotics, propofol, and dexmedetomidine, for intraoperative and postoperative pain management. Benzodiazepines bind specific receptors in the central nervous system, enhancing the inhibitory effect of various neurotransmitters. For example, benzodiazepines facilitate GABA-receptor binding, leading to an increase in the membrane conductance of chloride ions. The subsequent change in membrane polarization inhibits normal neuronal function. The advantages of midazolam compared with other drugs in this class include flexibility in administration methods, lack of pain on administration either intravenously or intramuscularly, and its favorable onset and duration of action. It has been suggested that midazolam may also have a favorable effect on postoperative nausea and vomiting.80

A narcotic analgesic is introduced only at the time of needle placement. For example, alfentanil provides intense analgesia of short duration, making it an excellent choice for administration just prior to block placement. Alfentanil is a less potent (1/5 to 1/10) analog of fentanyl. It penetrates the brain rapidly with an onset time to peak effect of 1 to 2 min. Recovery from alfentanil is more rapid than from fentanyl or sufentanil.82 Prolongation of drug effect after large or repeated doses is less likely because of its increased protein binding, lower lipid solubility, and smaller volume of distribution. Unlike fentanyl, there are no secondary increases in alfentanil plasma concentrations after large or repeated doses.83 When alfentanil is used for block placement, evaluation of the block can be conducted with return of full patient cooperation within minutes.84 Fentanyl and sufentanil have also been used effectively as part of the block sedation regimen. Fentanyl, in titrated doses of 25 to 100 mcg, provides satisfactory analgesia for block placement with minimal untoward side effects (eg, hemodynamic instability or severe respiratory depression), but plasma levels can increase with large or repeated doses.85

When multiple nerve blocks are necessary, low-dose sufentanil has been suggested to be an effective alternative to alfentanil, providing satisfactory pain relief without alterations in consciousness.79 Regardless of the narcotic chosen, timing of the administration of the narcotic depends on its onset and peak effect, which should coincide with needle insertion through deeper tissues. The dose and type of premedication used depend on the procedure, the patient, and the anesthesiologist's knowledge of the pharmacodynamics of the drugs chosen. Commonly used regimens for sedation during various regional anesthesia procedures are listed in Table 61–1.

Performance of Neural Blockade: Block Area vs Blocks in the OR

Peripheral nerve blocks are often thought to result in decreased OR efficiency. In contrast to this popular belief, when actual OR times are compared in that manner, several studies have demonstrated that OR times are actually reduced with the utilization of regional anesthesia.86 In a study by Williams and coworkers comparing general anesthesia with peripheral nerve blockade or to a combination of both, regional anesthesia was associated with the lowest anesthesia-controlled time, the lowest turnover time, and the lowest incidence of unplanned hospital admission.87

Whether a designated block room is needed depends on the skill and experience of the anesthesiologist as well as the local anesthesiology practice and layout of the holding area and ORs. Studies evaluating OR efficiency with peripheral nerve block anesthesia performed in an induction room vs in the OR have demonstrated conflicting results.86,88 Advantages of an induction room include reduction in OR time (arrival to beginning of surgery), less stressful environment for resident education and training, and the ability to change the anesthetic plan or redo an inadequate block without delaying surgery. Disadvantages of a designated block or induction room include the need for qualified personnel to monitor the patient once the block is placed, additional expenses related to the physical space and equipment, and lack of utilization of the space (first case of the day, outside regular OR hours, next patient not ready for a variety of reasons)89,90 Patient anxiety levels are unchanged whether the block is placed in the OR or in a dedicated induction area.91 In teaching institutions where peripheral nerve blocks are routinely administered in the OR, anesthesia induction time improves with the skill level of the anesthesiologist.92

Regardless of where the actual procedure is performed, adequate space, equipment, and monitoring are imperative to ensure time-efficient care of the patient. If a block room is used, the physical size should allow enough space for proper monitoring, emergency access, and resuscitation of the patient. All supplies, drugs, and other equipment for the block procedure should be readily available in the room and prepared at the bedside. Proper lighting, administration of oxygen, and emergency airway management equipment with suction must be available whenever a nerve block is performed.

Intraoperative Management

Almost any anesthesiologist with skill and determination can become proficient in neuraxial and peripheral nerve blocks, but the intraoperative treatment of the patient can be the most challenging aspect of the practice of regional anesthesia. Sedation appropriately adjusted for patient comfort is always beneficial and improves the quality of the anesthesia achieved with peripheral nerve blocks. Most surgeons prefer patients to be lightly asleep during surgery so that they can better concentrate on the technical aspects of the operation. Similarly, the majority of patients also prefer not to be aware of activities in the OR. The choice and amount of sedation depends on the patients' desire for sedation, their tolerance, and any medical problems that may affect the ability to tolerate deeper levels of sedation.

Intraoperative Sedation

Many choices are available for intraoperative sedation once the block has been placed. For an in-depth discussion on these medications see Chapter 11 (Sedation–Analgesia During Local and Regional Anesthesia). Here we will briefly discuss advantages and disadvantages to many of the medications often used in conjunction with regional anesthesia. The anesthesiologist should be comfortable with the mechanism of action, onset and duration, side effects, and hemodynamic effects of the medications used. It is prudent to remember that not all patients require significant additional sedation beyond that used for initial block placement.

Propofol, a diisoprophenol, is commonly used for induction, sedation, and maintenance of anesthesia. Because of its water insolubility, it is prepared in an emulsion that can cause pain on injection especially through small veins. Advantages of propofol include rapid onset, elimination, and low incidence of side effects. It has an antiemetic quality, making it a desirable medication for ambulatory surgery. Disadvantages in addition to the incidence of pain on injection include significant cardiovascular depression, especially in the elderly or debilitated patient. Propofol can either be given as repeated bolus doses every 5–15 min or, more commonly, as a continuous infusion. The usual dose for sedation during regional anesthesia is between 10 and 50 mcg/kg/min.

Dexmedetomidine, an α2-receptor agonist, has been used in critical care settings to effectively provide sedation with less hemodynamic instability than with propofol. It is gaining popularity as an effective agent for intraoperative sedation. Dexmedetomidine is approximately eight times more selective toward the α2-adrenoreceptors than clonidine. It decreases anesthetic requirements by up to 90% as well as inducing analgesia.93 At therapeutic doses, dexmedetomidine is not associated with respiratory depression, despite the profound levels of sedation that occur. It has the advantage of reducing postoperative narcotic requirements because of its analgesic properties. Compared with propofol, it has a slower onset and offset of sedation. Intraoperative mean arterial pressure is not reduced to the degree seen with propofol. Heart rate is decreased because of its sympatholytic and vagal-mimetic effects.94 The average infusion rate for intraoperative sedation is 0.5–0.8 mcg/kg/h. It is important for the clinician to note that errors with dexmedetomidine infusion have occurred because the drug was infused in micrograms per kilogram per minute instead of micrograms per kilogram per hour.95

Clonidine, an α2-adrenoreceptor agonist, has been advocated as another effective agent for intraoperative sedation. In a study on patients undergoing prolonged dental surgery, it was infused at a rate of 2 mcg/kg. It did not induce significant bradycardia, hypotension, or other severe side effects in healthy volunteers and provided an analgesic effect similar to that for dexmedetomidine.96

Low-dose midazolam infusions (0.03–1 mg/kg/h), combinations of ketamine and midazolam, and propofol and ketamine have been used effectively for intraoperative sedation after block placement. Ketamine has potent analgesic effects, provides hemodynamic stability (sympathomimetic action), and has minimal effect on the ventilatory drive, making it an excellent choice for debilitated patients or as a supplement for incomplete regional anesthesia. Analgesia can persist up to 40 min after ketamine administration has been terminated. Its association with postanesthetic confusion, disorientation, bad dreams, or hallucinations has limited its use in ambulatory surgery. Premedicating the patient with midazolam, limiting the dose, and allowing the patient to recover quietly will circumvent some of the untoward effects of ketamine.97,98

The use of narcotics during the intraoperative treatment of patients receiving regional anesthesia should be limited unless the patient has a chronic condition causing discomfort unrelated to the blocked surgical site. Narcotics should be used for analgesia and patient confort, not for anesthesia. They should not used to “rescue” an incomplete or failed block. Patient complaints should be investigated to determine if the discomfort is from positioning, prior chronic conditions, or in the surgical area not completely covered by the block. Because anesthesia of the skin is often the last to occur, local infiltration by the surgeon, when possible, and deeper levels of sedation at the beginning of the procedure are often all that is required for the procedure to proceed while the block is “setting up.” Providing adequate padding for extremities; support for the upper back, shoulders, and head; prewarming the OR table; and providing continued warmth with forced air heating, heated blankets, and warmed intravenous infusions will decrease the discomfort caused by the cold OR and firm OR table. Deeper levels of sedation or opioids may be required for patients with chronic pain conditions. Using a short-acting sedative (eg, propofol) is a better choice than continued narcotic boluses that will compromise the patient's ability to protect the airway. If the block is inadequate or these measures are ineffective, it is safer to induce a light general anesthesia and control the airway rather than resorting to oversedation and intravenous narcotics. However, patients who chronically use oral opioids to treat their osteoarthritic or other pain needs may require and benefit from the judicious intraoperative use of opioids for their comfort.

Finally, some patients can be well sedated by the administration of low concentrations of nitrous oxide, similarly to the practice widely used in dental offices. Others, however, may be very intolerant of the effects of nitrous oxide. Nitrous oxide has analgesic and sedative properties and can be easily discontinued if the patient is not tolerating it.

Intraoperative Monitoring

Intraoperative monitoring is essential to the safety of regional anesthesia. Before any local or regional anesthetic is administered, equipment and medications should be available to support full resuscitation. The same equipment used for general anesthesia should be checked and be immediately available in the event that the anesthetic is converted to general. If the block is placed in the OR, blood pressure, electrocardiography, pulse oximetry, and end-tidal carbon dioxide monitoring should be instituted before the block is placed. A face mask (6 L of oxygen) or nasal cannula (up to 5 L of oxygen) should be applied once sedation is begun and continued throughout the case. It is of utmost importance that a properly functioning bag–mask device capable of delivering positive–pressure ventilation be immediately available in the area where regional anesthesia is practiced. The CO2-sampling line can be connected to the face mask or to the nasal prongs to provide continuous end-tidal CO2 measurement. Temperature monitoring should follow ASA standards.99 For longer cases in which large areas of the patient's body are exposed, the patient's temperature should be monitored continuously.

Monitoring the patient under light or deep sedation requires vigilance on the part of the anesthesiologist. The potential problem of hypoventilation induced by sedatives is ever present. End-tidal CO2 monitoring and pulse oximetry help guide the depth of sedation that is safe for the patient. In one study of plastic surgery patients, 39% of the patients developed oxygen saturations below 89%, despite appropriately administered sedation.100

Intraoperative Patient Care

In addition to hemodynamic monitoring, other needs of the patient need to be addressed whether the patient is under light or deep sedation. Noxious stimuli and uncomfortable positioning may make a pleasant experience potentially intolerable.

Significant noise levels are often present in the OR due to discussion among the staff, handling of instruments, or the use of various pneumatic instruments. In a study on noise levels during various orthopedic surgical procedures, noise levels up to 118 decibels (dB)—a level that is potentially damaging to the hearing—were recorded when pneumatic drills and saws were used. Suction tips were found to yield levels up to 96 dB.101 In another study on the effect of noise on the bispectral index, noise levels over 100 dB resulted in an appreciable increase in the bispectral index, despite propofol sedation.102 Shielding the patient's ears from the unwanted noise should be done routinely to help reduce the patient's anxiety.

Warming the OR table with forced air prior to positioning the patient on the table, then covering the patient with a warm blanket helps to relax the patient and provide comfort prior to sedation for the block injection (Figure 61–7). Preventing hypothermia during the operation will help prevent uncomfortable postoperative shivering and delays in discharge from the recovery room. Making the OR table as comfortable as possible with additional padding and positioning will make longer procedures more tolerable, especially for the arthritic patient or the patient with chronic axial pain.

Transition of Patients from the OR to Postoperative Care

After surgery, most patients are fully alert and able to meaningfully discuss the findings with the surgeon in the OR while a wound dressing is being applied. On arrival in the recovery room, most ambulatory surgery patients are fast-tracked to the postanesthesia care unit and prepared for discharge. Inpatients are often more comfortable, especially in the early recovery period, due to the lasting effects of the local anesthetics chosen for the regional technique.

Transfer of Care to the Nursing Staff

To prevent unnecessary concerns by anyone involved in treating the patient, it is important, on completion of the surgical procedure, to discuss with the surgeons, patient, and nursing staff the expected duration of the motor and sensory blockade. A proper multimodal pain management protocol should be developed and thoroughly discussed with the nursing staff and the patients and their families. An understanding of the need to provide pain relief for surgical areas not covered by the nerve block and to avoid severe pain when the block wears off is important for a satisfactory postoperative recovery. To avoid unnecessary consultations, it is important for the staff and patient to understand that the block may last longer in some patients than in others because of the variability in the duration of action of local anesthetics.

Outpatient Acute Pain Management

Standard verbal and written instructions regarding pain management at home and protection of the anesthetized extremity are commonly provided for outpatients to ensure continued safe and satisfactory recovery.52 Additional instructions are necessary for patients with continuous peripheral nerve block analgesia. Both verbal and written instructions about the infusion pump, its safety mechanisms, signs and symptoms of local anesthetic toxicity, and contact information should any questions arise should be given to the patient before discharge. Most centers utilizing continuous peripheral nerve block infusions at home have developed protocols for patient follow-up and evaluation, patient and nursing education, and emergency contact information. When home health nurses can be involved, extensive patient education and home evaluation can be conducted. The home health nurses can be trained to evaluate the patient for adjustments in drug delivery and assess catheter sites, dressings, and infusion devices. They can be trained to remove the peripheral nerve catheters, saving the need for the patient to return to the hospital for care. Telephone follow-up within the first 24 h is a necessary part of patient care when continuous catheters are utilized. Depending on the length of time the catheter is left in place, continued regular follow-up by telephone or a postoperative visit should be instituted until the catheter is removed.103

It is beyond the scope of this chapter to discuss various local anesthetic protocols for continuous outpatient nerve blocks (the reader is directed to Chapter 10 [Local Anesthetic Solutions for Continuous Nerve Blocks] for more information on this subject). In general, a continuous infusion of dilute ropivacaine (0.2%) at a continuous rate of 5–10 mL/h has been suggested by some authors as it provides excellent sensorimotor dissociation with better preservation of motor function than bupivacaine.104 Other administration protocols include PCA (bolus technique) or a low background continuous infusion combined with a smaller boluses of PCA. It has been suggested that PCA techniques reduce the local anesthetic consumption by 64 to 73%.105

Inpatient Acute Pain Management

The same education is important for the patient who is to be admitted after a surgical procedure with regional anesthesia. Because longer-acting local anesthetics can be used for the patient who is to be admitted, it is important for the nursing and surgical staff to understand that the duration of the sensory and motor block will be prolonged. Again, educating the staff and the patient will prevent unnecessary consultations for neurologic defects. Even surgical staff comfortable with regional techniques need to be educated about the duration and effect of the peripheral nerve blocks. For example, when a patient has a total knee replacement, often a continuous femoral nerve catheter is placed for postoperative pain control. The femoral nerve block will cover a large portion of the area causing pain, but the sciatic distribution is not blocked. Pain control for the sciatic distribution is usually best accomplished by prescribing intravenous PCA or oral analgesia. This multimodal approach to pain management is especially important for the inpatient as the surgical procedures are usually more involved. Educating the staff about the benefits and limitations of the block as well as the need for additional pain medication will prevent misconceptions about patient pain complaints.106,107

Other factors related to the block also require staff education for the safety of the patient. If the block is going to affect lower extremity motor function, the patient will not be able to get out of bed by himself or bear weight on the blocked lower extremity. This should be explained to the patient and the caregivers. If an upper extremity block has been performed, then measures to protect the blocked upper extremity (eg, sling for interscalene blocked extremity) need to be instituted. The patient and family need to be reminded that the full function of the extremity will return when the block wears off.

Regional anesthesia is an exciting, expanding subspecialty of anesthesiology. For the safe and efficient practice of regional anesthesia, dedication, experience, and perseverance are all necessary. It is a subspecialty as diverse as any other in anesthesia, requiring the same degree of advanced training from the resident to the fellowship level and beyond. Placing the block is only one aspect of the regional anesthesia practice. Appropriate patient selection and education, staff education, intraoperative management, and postoperative patient care are all important factors that must be included in the development of a successful regional anesthesia program.