Acknowledgments:
The author wishes to recognize the work of previous authors Drs. Lauren Fisher and Michael Gordon for their contributions to Green’s Operative Hand Surgery and to this manuscript.
There are several techniques for providing anesthesia for hand surgery. This chapter provides an overview, illustrating both the risks and benefits of each. General anesthesia will be briefly discussed and regional techniques will be addressed, as well as the unique role that regional anesthesia plays in both operative anesthesia and postoperative analgesia for hand surgery.
General Anesthesia
General anesthesia has long been the technique of choice for surgical procedures, using either traditional endotracheal intubation or the newer laryngeal mask airway. Considered fast and reliable, it is the standard of care at many institutions. Unfortunately, it also has its share of complications, because the systemic administration of medication can cause derangements of other organ systems, including the brain, the heart, the lungs, the airways, and the gastric, endocrine, and renal systems. General anesthesia often calls for airway manipulation, which causes additional associated complications ranging from minor sore throat and hoarseness to more feared, serious complications, including laryngospasm, aspiration, or failed airway. These serious complications are relatively rare; more prevalent are the minor complications of nausea and vomiting, grogginess, or pain requiring further treatment.
General Anesthesia
General anesthesia has long been the technique of choice for surgical procedures, using either traditional endotracheal intubation or the newer laryngeal mask airway. Considered fast and reliable, it is the standard of care at many institutions. Unfortunately, it also has its share of complications, because the systemic administration of medication can cause derangements of other organ systems, including the brain, the heart, the lungs, the airways, and the gastric, endocrine, and renal systems. General anesthesia often calls for airway manipulation, which causes additional associated complications ranging from minor sore throat and hoarseness to more feared, serious complications, including laryngospasm, aspiration, or failed airway. These serious complications are relatively rare; more prevalent are the minor complications of nausea and vomiting, grogginess, or pain requiring further treatment.
Regional Anesthesia
Regional anesthesia is the anesthetic of choice at our institution and is especially suited to upper extremity surgery, as most patients are ambulatory. For inpatients, regional anesthesia is associated with less time spent in the recovery room, improved pain control, lower opiate consumption, and less nausea and vomiting. Regional blockade can be used alone as an intraoperative anesthetic or as a supplement to general anesthesia.
Contraindications
Absolute Contraindications
The two absolute contraindications to regional anesthesia are (1) patient refusal and (2) infection at the site of needle insertion. Often patients refuse regional anesthesia because they have been inadequately educated preoperatively or are misinformed about it. However, many common fears regarding regional anesthesia can be dispelled with a forthright discussion. For instance, patient surveys reveal concerns regarding discomfort during needle placement or awareness of the surgical procedure. These concerns are easily allayed with adequate premedication and sedation. In fact, a regional technique would be advantageous to the patient wishing to minimize sedation and remain awake.
Relative Contraindications
Need for Assessing Postoperative Nerve Status or Compartment Syndrome.
Because a successful block hinders motor and sensory conduction, nerve testing in the immediate postoperative period is not possible. Therefore, if an immediate postoperative assessment of nerve function is required, a regional block should not be used.
Fear of masking postoperative compartment syndrome is another relative contraindication to regional anesthesia. Compartment syndrome is diagnosed from both the subjective history and objective findings, especially compartment pressure measurements. Pain in the postoperative period is estimated to precede changes in neurovascular status by 7.3 hours but can be masked by the use of nerve blockade provided for analgesia. Even more confusing, there are also reported cases of compartment syndrome being masked by intravenous (IV) morphine administration during patient-controlled analgesia. Concern for the development of compartment syndrome should be conveyed prior to the start of the case and a plan for postoperative pain control determined at that time. Appropriate vigilance is needed and measurement of compartment pressures mandatory if suspicion for increased compartment pressures exists.
Aggravating a Preexisting Nerve Injury.
Another concern is the possibility that regional nerve blockade will incite further nerve injury (double-crush phenomenon) in patients with preexisting nerve injury or paresthesias. While this is an understandable concern, experience has shown that regional nerve blockade remains an appropriate option for patients undergoing uncomplicated procedures such as ulnar nerve transposition and the vast majority of elective upper extremity operations.
At our institution, most surgeons and anesthesiologists, in consultation with the patient, opt for the use of regional nerve blockade, even in cases of existing nerve injury or dysfunction. The demonstrated safety of newer techniques (described in the following) and benefit of pain control outweigh the unlikely risk of nerve injury. It is important to discuss the advantages and disadvantages with the patient, allowing him or her to participate in decision making, especially when nerve dysfunction preexists. For patients who appear to fear further nerve injury, we often opt to use general anesthesia with local anesthesia at the surgical site in order to avoid adding a perceived risk and uncertainty to the fears of an already anxious patient.
Anticoagulation Therapy.
A relative concern among regional anesthesiologists is performing regional blockade in patients who are taking anticoagulants. More and more patients presenting for surgery are already taking anticoagulants for treatment of underlying coronary artery disease, atrial fibrillation, or cerebrovascular disease or for prevention or treatment of deep venous thrombosis. An injury or even the stress of surgery itself, along with a prothrombotic tissue insult, places anticoagulated patients at risk for development of postoperative deep and superficial venous thrombosis and leads many practitioners to prescribe antithrombotic measures to prevent its occurrence.
Regional neuraxial (spinal or epidural) anesthesia does not contribute to venous thrombosis in patients not receiving anticoagulation therapy and, in fact, has been shown to reduce the rate of blood clots following lower extremity and abdominal surgery, though this advantage has been minimized in recent years with the advent of aggressive and risk-appropriate thromboprophylaxis. Postulated mechanisms include sympathetic blockade leading to improved blood flow and decreased sympathetic stimulation, as well as a direct antithrombotic effect of the local anesthetic solution. However, neuraxial regional anesthesia is contraindicated in the fully anticoagulated patient, given the risk of epidural hematoma and subsequent devastating neural injury. Performance of deep plexus blocks in this setting, though, remains practitioner-dependent. Although few case reports exist of retroperitoneal hematoma following deep lumbar plexus blockade in anticoagulated patients, the relative safety of this technique was confirmed in a large study of 670 patients who underwent continuous lumbar plexus blockade while anticoagulated with warfarin.
In the anticoagulated patient, a perivascular brachial plexus nerve block has the potential to cause excessive bleeding. Yet, several case reports document the safety of peripheral nerve block in the anticoagulated patient, particularly when it is placed under ultrasound guidance. Despite these reassuring findings, the most recent published regional anesthesia guidelines advocate applying the same recommendations for neuraxial anesthesia to patients undergoing deep plexus or perivascular nerve blocks. Patients who have incomplete reversal of their anticoagulation or who possess mild derangements of their coagulation panel for unclear reasons must be approached on a case-by-case basis, and the risks and benefits must be discussed thoroughly with the patient.
Bilateral Procedures.
Although there may be instances in which regional anesthesia could be used for bilateral procedures, there are many risks, and it should be avoided if possible. The risk of drug toxicity is higher because the dose must be nearly doubled. Using a lower amount to avoid toxicity raises the probability of block failure. The type of block also influences the risk. Interscalene nerve block commonly results in phrenic nerve paralysis, so bilateral interscalene nerve block is contraindicated because of the risk of respiratory failure. Even supraclavicular blockade has an estimated associated risk of diaphragmatic paralysis of around 50% ; this risk, compounding the associated risk of pneumothorax, makes supraclavicular blockade an unreasonable technique for bilateral regional blockade. A safer alternative may be combining techniques of proximal and distal blockade or performing the blocks using low-volume, short-acting local anesthetics in sequence (i.e., performing the block on the second limb only upon completion of the first limb).
Relative Indications
Microvascular Surgery Patients
Regional anesthesia with the use of long-acting blocks or continuous/prolonged infusion for digital reimplantation and free flaps is discussed in a later chapter. Continuous sympathetic blockade causes vasodilation and improves blood flow to the digit at risk and reduces neurogenically mediated vasospasm. Improved pain control at the graft site via an effective nerve block also reduces pain-induced sympathetic-mediated vasospasm. While peripheral nerve blockade has been shown to be a safe and effective anesthetic option, it is still unclear whether continuous nerve blockade indeed results in improved graft survival.
Patients with scleroderma undergoing digital sympathectomy and vascular reconstruction also benefit from prolonged anesthetic blockade.
Finally, patients with complex regional pain syndrome who undergo corrective surgery are also likely to benefit from effective prolonged regional anesthesia.
Pediatric Patients
Anesthesia for pediatric patients depends greatly on the age and maturity of the child and the experience of the anesthesiologist. Many techniques combine general anesthesia for the surgical procedure itself with regional anesthesia for postoperative pain control. Many practitioners are comfortable placing blocks in anesthetized children, especially under ultrasound guidance, though the dose of anesthetic agent and the anatomy must be carefully considered. Regional anesthetic technique has been demonstrated to be an effective form of postoperative pain control in children with very low rates of complications and it has opioid-sparing effects. A long-term study looking at the use of continuous peripheral nerve catheters in pediatric patients shows this to be a safe and effective way to provide prolonged analgesia for this population of patients.
Pregnant Patients
While elective procedures are generally not performed during pregnancy, circumstances that require surgery may present. When possible, a local or regional technique should be used to minimize the effects on maternal physiology as well as reduce the possible pharmacologic exposure of the developing fetus. Ideally, surgical procedures should be deferred to the second trimester to minimize exposure of the fetus to teratogens during the critical period of organogenesis (15 to 56 days) and also limit the risks of preterm labor more prevalent in the third trimester.
An anesthetic plan must provide safe anesthesia for both the mother and the fetus. When surgery is unavoidable in a previable fetus, the American College of Obstetricians recommends monitoring the fetal heart rate by Doppler ultrasound before and after surgery. With regard to a viable fetus, fetal heart rate and contraction monitoring should occur before, during, and after the procedure. The patient should have given consent for emergency cesarean section, and obstetric staff should be on standby in the event of fetal distress.
The pregnant patient has an increased cardiac output, increased minute ventilation, increased risk for gastric aspiration, and increased upper airway edema, which can increase the risk of failed intubation. Fetal safety generally relates to avoidance of teratogenicity, avoidance of fetal asphyxia, and avoidance of preterm labor. While randomized controlled trials examining teratogenicity are not ethically or clinically feasible, local anesthetics, volatile agents, induction agents, muscle relaxants, and opioids are not considered teratogenic when used in clinical concentrations when normal maternal physiology is maintained. Nitrous oxide is probably best avoided given its effects on DNA synthesis and its teratogenic effects in animals.
Patients With Rheumatoid Arthritis
Patients with rheumatoid arthritis are especially suitable candidates for regional anesthesia for upper limb surgery as it decreases the need for airway manipulation and blunts the stress response to surgery. Patients with deformity associated with advanced rheumatoid arthritis require careful positioning on the operating room table to avoid injury to other areas of the body.
This patient population often carries a high potential for airway complications owing to cervical spine immobility, paradoxic atlantoaxial instability, temporomandibular joint ankylosis, and cricoarytenoid arthritis, all of which make endotracheal intubation difficult. Additionally, many rheumatoid patients are maintained on antirheumatic drugs and systemic corticosteroids, which have the potential for causing immunosuppression and a decreased neuroendocrine stress response. Patients consuming at least 20 mg of prednisone a day for more than 3 weeks are considered at significant risk for hypothalamic-pituitary-adrenal suppression. These patients may be considered for stress dose steroid coverage depending on the invasiveness and stress of the procedure, and steroid treatment should be provided in the event of refractory hypotension.
Advantages and Disadvantages ( Box 1.1 )
A common concern regarding regional anesthesia is the question of whether the block will work. Success depends on the experience and confidence of the practitioner performing the block. At our orthopedic hospital, more than 6300 upper extremity blocks are performed annually, and we are able to achieve a surgical level of anesthesia in 94% to 98% of patients.
In spite of the advantages of regional anesthesia, several factors may prevent its use. Each of these problems can be overcome with appropriate planning.
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Time constraints
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Anesthesiologist’s lack of familiarity with the procedure
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Patient’s fear of anesthesia failure
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Concern about complications
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Patient’s desire to be completely unaware during the procedure
While regional blockade can effectively anesthetize the upper extremity and surgical site, this does not ensure patient comfort. Patients asked to lie motionless on a hard operating room bed might be apt to move to relieve discomfort in the back or knees, therefore disturbing the operative field. We place pillows to support the head and under the knees to reduce low-back strain. Even with adequate motor and sensory blockade, some patients will experience vibration or proprioception, and even vague sensations of pressure in the operative limb. Adequate anxiolysis and sedation will minimize the sensation. Access to the airway should be maintained during surgery in case the block is inadequate or other problems ensue. If the patient’s position, such as lying prone, precludes this access intraoperatively, preoperative securing of the airway may be needed.
Duration of the neural blockade is variable, anywhere from 45 minutes to 24 hours after a single injection. The duration can be extended using a peripheral nerve catheter for continuous local anesthetic administration. Catheters have been successfully inserted along various levels of the brachial plexus depending on the desired location of blockade, from above the clavicle, such as interscalene and supraclavicular locations, to below the clavicle, such as infraclavicular and axillary locations. Catheters can be maintained to provide continuous-flow or patient-controlled analgesia for hospitalized patients, and many centers have started home catheter programs for their outpatient population.
Prolonged regional anesthetic blockade provides improved pain relief during immediate postoperative physical therapy, and does not necessarily preclude active participation. In a study comparing continuous patient-controlled perineural infusion with 0.2% ropivacaine with patient-controlled IV narcotic infusion following arthroscopic rotator cuff repair, regional anesthesia techniques resulted in decreased use of supplementary analgesics and had a comparable incidence of motor weakness as did IV patient-controlled analgesia.
The advantages of regional nerve block have been well demonstrated in the ambulatory surgery population. These advantages include lower pain scores, decreased nausea and vomiting, and shorter stays in the postanesthesia care unit. While these effects are considerable in the immediate postoperative period, studies are ongoing to demonstrate a long-term outcome difference between the different types of anesthetics. Evidence supports the finding that in patients undergoing repair of displaced distal radius fracture, regional anesthesia offers decreased pain and improved functional outcomes at 3 and 6 months.
Equipment and Pharmacologic Requirements
Medications commonly used in regional anesthesia are listed in Table 1.1 .
| Generic Name (Trade Name) | CONCENTRATION (g/dL) | Maximum Dose (mg/kg) * | Approximate Duration | |
|---|---|---|---|---|
| Infiltration | Nerve Block | |||
| Procaine (Novocain) | 0.75 | 1.5-3 | 10-14 | 45-90 min, short-acting |
| Chloroprocaine (Nesacaine) | 0.75 | 1.5-3 | 12-15 | |
| Lidocaine (Xylocaine) | 0.5 | 1-2 | 8-11 | 1.5-3 hr, medium-duration |
| Mepivacaine (Carbocaine) | 0.5 | 1-2 | 8-11 | |
| Tetracaine (Pontocaine) | 0.05 | 0.15-0.2 | 2 | |
| Bupivacaine (Marcaine) | 0.25 | 0.25-0.5 | 2.5-3.5 | 3-10 hr, long-acting |
| Ropivacaine (Naropin) | 0.25 | 0.25-0.5 | 2.5-3.5 | |
Regional anesthesia may be administered in a designated block room or preoperative area, in addition to in the operating room. It is crucial to have available appropriate monitoring and resuscitation equipment, including airway management supplies and resuscitative medication, should an acute complication arise. High-flow oxygen, airway management equipment, and suction capability are crucial for emergency airway management in the event of seizure or high or total spinal block. Medications including inotropes, anticholinergics, and vasopressors should be immediately available to treat symptomatic arrhythmias, bradycardias, and hypotensive episodes. Other available medications should include benzodiazepines or propofol to treat seizures and an intralipid to treat bupivacaine-induced cardiovascular collapse ( Box 1.2 ).
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Avoid intravascular injection.
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Use epinephrine to slow systemic absorption.
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Use benzodiazepine as a premedication.
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Use ultrasound guidance to fractionate the dose.
Local Anesthetic Additives
In recent years, the use of additives in local anesthetics to increase efficacy and onset of block, as well as overall block duration, has been readily investigated. Historically, sodium bicarbonate has been used to increase onset of sensory and motor blockade in epidural anesthesia through alkalinization of the molecule, thereby facilitating its passage across lipid membranes. When used perineurally, this advantage appears to be more unpredictable for certain types of blocks and may not be clinically significant. Epinephrine, on the other hand, remains one of the most popular adjuncts for prolonging the effect of short- and intermediate-acting local anesthetics by decreasing systemic uptake of the local anesthetic through vasoconstriction. It is also an excellent marker for detection of intravascular injection. The advantage of epinephrine as an adjunctive in long-acting local anesthetic peripheral nerve blocks is not as apparent, especially when juxtaposed with concerns of neurotoxicity in at-risk patients.
Dexamethasone is another additive that has gained popularity in recent years because of its ability to significantly prolong peripheral nerve blockade. Through its proposed ability to inhibit nociceptive C-fibers, dexamethasone has been used with both short- and long-acting local anesthetics in upper extremity surgeries with some success, though recent randomized trials and meta-analyses suggest that this effect can be achieved just as well via IV administration, which has a well-characterized safety profile. While investigations into concerns for neurotoxicity with dexamethasone have not yielded conclusive results, we recommend that care be taken when using this adjunct in patients with preexisting nerve injuries.
Alpha-2 selective adrenergic agonists such as clonidine and dexmedetomidine have an analgesic benefit when added to local anesthetics for peripheral blocks. By inhibiting current channels that facilitate neurons to return to normal resting potential from a hyperpolarized state, clonidine and dexmedetomidine selectively disable C-fiber neurons from generating subsequent action potentials, resulting in analgesia. The disadvantages of using these additives include dose-dependent systemic effects of sedation, bradycardia, and hypotension.
Opioid agonists such as tramadol and buprenorphine are also used as additives to local anesthetics. Tramadol, which acts as a weak mu-opioid agonist while stimulating serotonin release and inhibiting reuptake of norepinephrine, prolongs blockade when given perineurally but does not reliably have a clear advantage over IV or intramuscular administration. Buprenorphine, on the other hand, has a fairly consistent record of prolonging block duration and reducing postoperative analgesia when given perineurally, an effect not related to systemic absorption of the drug. The mechanism of action of buprenorphine is an ability to inhibit voltage-gated sodium channels in a fashion similar to local anesthetics. Further studies are needed to elucidate any potential neurotoxic effects of this adjunct.
Finally, additives such as ketamine, midazolam, and magnesium, while showing some promise, do not have an adequately characterized safety profile to be recommended as routine additives to local anesthetics at this time.
Historical Techniques
Regional nerve blockade is essentially the deposition of local anesthetic near a nerve. Historically, nerve blocks were blind techniques, performed on the basis of known anatomic relationships to superficial landmarks. Practitioners noted that patients would report paresthesias as the needle advanced, leading to development of the paresthesia technique. This technique required a cooperative and conscious patient capable of providing verbal feedback, as the anesthetic practitioner would intentionally attempt to elicit a paresthesia as a means of nerve localization. Others began experimenting with the use of a nerve stimulator, applying a low-current electrical impulse through the needle near a nerve to stimulate muscle contraction. Studies were unable to demonstrate outcome differences. Though it was hoped that nerve localization using nerve stimulation would decrease actual needle-to-nerve contact, reducing nerve injury, a randomized prospective trial comparing the two techniques was unable to determine a difference in postoperative neurologic symptoms. An advantage of the development of the nerve stimulator was decreased reliance on patient feedback and, therefore, the ability to perform the technique on sedated or even anesthetized patients.
Ultrasound was next used to improve needle placement by means of a portable device in the operating room or holding area. Ultrasound allows visualization of anatomic structures, blood vessels, and nerves, as well as of the advancement of a needle and the distribution of local anesthetic. With satisfactory visualization of target structures, this technique does not require patient feedback and can be used safely after the patient has been given sedation or even general anesthesia. However, when target structures are deep, needle visualization can be difficult; in such cases, it is a standard of safety to engage patient feedback whenever possible. Several studies have demonstrated improved onset and decreased dosing requirements compared with traditional techniques. A recent metaanalysis of 16 randomized controlled trials showed that ultrasound decreased the incidence of complete hemidiaphragmatic paresis and vascular punctures and was more likely to result in a successful brachial plexus block when compared with the nerve stimulation technique. Despite these benefits, ultrasound-guided blocks do not appear to decrease the incidence of neurologic injury. Certainly, this is an area in need of further study and review as we attempt to maximize results while minimizing risks of complications for our patients.
Continuous Peripheral Nerve Catheters
The use of continuous peripheral nerve catheters has gained favor both in the inpatient setting and the outpatient setting. As mentioned before, the advantages include time-extended, opioid-sparing, and site-specific analgesia with only minimal side effects. Disadvantages include increased anesthesia performance time, dislodgement or malplacement of the catheter leading to ineffective analgesia, and infection. Rarely, brachial plexus peripheral nerve catheters have led to epidural and even intrathecal blockade. The incidence of brachial plexus catheter failure on postoperative day 1 is between 19% and 26%. The rate of dislodgement is low (<5%) but is directly correlated with the length of time the catheter has been in place and the extent of upper extremity movement. Though there appears to be a modest clinical benefit to the use of nerve-stimulating catheters over nonstimulating catheters to confirm tip placement, this advantage has been largely minimized by ultrasound guidance. In contrast to epidural catheters, the choice of end-orifice versus multiple-orifice catheters in continuous peripheral nerve blocks does not affect analgesic quality.
Once the patient is at home, peripheral nerve infusion pumps for ambulatory surgery patients are safe and effective for extending the duration of nerve blocks from hours to days. In a study of ambulatory patients comparing general anesthesia with single-shot interscalene nerve blocks with continuous interscalene blocks for 48 hours, during which time the patients went home, the catheter group had lower pain scores both at 48 hours and at 1 week. Rare complications include respiratory compromise in proximal brachial plexus catheters (interscalene and supraclavicular blocks) due to ipsilateral diaphragmatic paralysis, technical problems involving the infusion pump leading to dosing inconsistency, infection due to the indwelling catheter, and catheter coiling leading to block failure or catheter retention. Evidence supports the use of these catheters in children as well as adults.
Minimum Effective Volume
In recent years, efforts to determine the minimum effective volume (MEV) of local anesthetic required to produce an adequate operative and postoperative anesthetic have been made in order to reduce the dose-dependent side effects and the risk of neurotoxicity and systemic absorption without sacrificing time to onset of block and overall duration of effective analgesia. These efforts have been helped enormously by the use of ultrasound. For the upper extremity, low local anesthetic volumes have been established for interscalene blocks and axillary blocks using ultrasound guidance. Although the absolute effect of type and concentration of local anesthetic on minimal volume is not yet elucidated, the MEV to elicit an interscalene blockade that is 90% to 95% successful ranges as low as less than 1 mL. Reducing the anesthetic volume in interscalene blocks has the potential advantage of reducing the incidence of hemidiaphragmatic paresis. For axillary blocks, the 90% to 95% MEV averages 1 to 2 mL per nerve. On the contrary, the 90% to 95% MEV for supraclavicular and infraclavicular blocks averages above 30 mL. We postulate that this discrepancy in the latter blocks may be related to increased variations in injection techniques and anatomy.
Elderly patients generally require lower local anesthetic volumes, an effect likely related to a decrease in the cross-sectional area of the brachial plexus as we age. Similarly, diabetic patients are more likely to have a successful supraclavicular block than their nondiabetic counterparts for a given local anesthetic dose. The authors postulate that this is due either to an increased sensitivity of diabetic nerve fibers to local anesthetic, inadvertent intraneural penetration due to decreased ability to elicit paresthesias, or a preexisting neuropathy leading to decreased sensation to surgical stimulation. Surprisingly, although associated with a higher performance difficulty, an increased body mass index does not necessitate an increased local anesthetic volume.
In general, in the absence of additives, decreasing the dose of local anesthetic either by volume or concentration in the peripheral block results in a reduction of block duration and decreases the time until the patient first requires an analgesic. Despite the advantage of decreasing dose-dependent complications and reducing neurotoxicity, our goal in establishing the MEV should always be juxtaposed with the surgical procedure, the patient’s particular risk factors, and the expected postoperative pain. In the end, it is also important to remember that the MEV for any given block is heavily influenced by the practitioner and his or her ability to deposit local anesthetic optimally.
Specific Blocks
The goal of regional anesthesia for upper extremity surgery is to provide anesthesia in the localized area of surgery, taking into account other potential painful stimuli, including positioning and the application of a tourniquet. There are many different approaches to nerve blockade, all involving nerves encompassed in the brachial plexus and providing sensory and motor innervation to the upper extremity. The brachial plexus is formed by the ventral rami of C5-T1, occasionally with small contributions by C4 and T2 ( Figure 1.1 ).
There are multiple approaches to blockade of the brachial plexus, beginning proximally with the interscalene approach and continuing distally with the supraclavicular, infraclavicular, axillary, and midhumeral approaches at the terminal branches. The uniting concept is the existence of a sheath encompassing the neurovascular bundle extending from the deep cervical fascia to slightly beyond the borders of the axilla.
Interscalene Block
The interscalene block is the most proximal approach, performed as the brachial plexus courses in the groove between the anterior and middle scalene muscles, traditionally at the level of the cricoid cartilage ( Figure 1.2 ). This block is well suited for procedures of the shoulder, the lateral two thirds of the clavicle, and the proximal humerus. Advantages of this block include rapid and reliable blockade of the shoulder region, as well as relative ease of landmark palpation. Disadvantages of this block traditionally include incomplete coverage of the inferior trunk of the plexus; hence, insufficient anesthesia of the ulnar distribution makes it an unreliable block for forearm or hand procedures. The interscalene block commonly causes transient ipsilateral diaphragmatic paralysis and ipsilateral Horner syndrome because of the proximity of the phrenic nerve and the cervical sympathetic ganglion, respectively. Rare but serious complications include permanent phrenic nerve palsy and cervical epidural and total spinal blockade.
Supraclavicular Block
A supraclavicular approach to the brachial plexus provides profound anesthesia for the entire arm, making it an appropriate block for most upper extremity procedures. Past approaches have used surface landmarks, generally lateral to the lateral border of the sternocleidomastoid muscle and superior to the clavicle, considering the first rib as the safety margin for the cupola of the lung. Proximity to the brachial plexus was determined using either paresthesia or nerve stimulator techniques. Concern regarding the risk for pneumothorax with traditional techniques (estimated at 1% to 4%) led to the development of an ultrasound-guided technique for supraclavicular brachial plexus blockade ( Figure 1.3 ). Ultrasound guidance allows the practitioner to visualize the first rib and the border of the pleura, thereby being able to watch the approach of the needle to help ensure an appropriate distance from these vulnerable structures. Advantages include a compact formation of the plexus at this level and resultant dense blockade of the entire upper extremity. Disadvantages include the remote risk of pneumothorax, suprascapular nerve palsy, and potential for slower block onset.
