• Admir Hadzic, MD

        INTRODUCTION

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 ofwell-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).

Figure 61-1. Five elements for success with nerve blocks.

        PREANESTHETIC MANAGEMENT

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 patients 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 Glla/IIIb inhibitors.²³ Nonsteroidal antiinflammatory drugs (NSAIDs) and aspirin are not contraindications to block placement.

Clinical Pearls

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 anes thesia. 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.

Clinical Pearls

        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

Clinical Pearls

        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

Figure 61-2. An example of how a nerve block may be the most suitable anesthetic option even in the presence of severe coagulation abnormality. Shown is an elderly patient who was emergently brought from the intensive care unit for washout of the septic knee (black arrow). He sustained a massive myocardial infarction several days prior and was extubated after a difficult weaning just 24 h prior this surgery. His INR was 2.4 and his left femoral vein was cannulated with a triple-lumen catheter (white arrow). He was profoundly hypotensive in the ICU and treated with multiple vasopressors.

        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 hemo- dynamically 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).

Figure 61-3. Femoral nerve block was stimulated immediately lateral to the pulse of the femoral artery and 15 mL of mepivacaine 1.5% was injected, which was all that was required for the planned surgery. This avoided the need for reintubation as the spinal or epidural anesthesia was contraindicated in the setting of anticoagulation.

Clinical Pearls

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

Clinical Pearls

        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.³⁰ 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.

Clinical Pearls

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.

Clinical Pearls

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

Clinical Pearls

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.

Clinical Pearls

Related posts:

Regional Anesthesia in the Patient with Preexisting Neurologic Disease. The History of Local Anesthesia. Stimulating Catheters. Ultrasound-Assisted Nerve Blocks in Adults. Cutaneous Blocks for the Upper Extremity. Cervical Plexus Block.