CHAPTER 71 ANESTHESIA TECHNIQUES
WARREN C. HAMMERT
A variety of anesthetic techniques can be used effectively for upper extremity surgery. Most upper extremity surgical cases can be performed using regional anesthesia, monitored anesthesia care (MAC) and/or local. These anesthetic choices have advantages over general anesthesia, such as decreased incidence of postoperative nausea and vomiting, better pain control, and greater cardiovascular stability, and earlier discharge. General anesthesia for upper extremity surgery is the same as for other anatomical regions and will not be discussed in this chapter.
The choice of anesthesia is dependent on the duration and type of procedure, anatomical location, and surgeon and patient preference. Although the surgeon will not perform all regional blocks, he/she should be familiar with the techniques and advantages/disadvantages of different techniques and the anatomy of peripheral nerves.
A description of the various local anesthetics and their pharmacology is found in Chapter 12.
The perineurium acts as a barrier, preventing high concentrations of anesthetics from reaching the intraneural structures. This protective perineurium makes direct toxicity rare without an intraneural injection. Injection directly into the nerve produces an intense pain response and must be avoided. Care must be taken when injecting around peripheral nerves in patients under general, deep sedation, or with proximal nerve blockade as they will not elicit the pain response and inadvertent intraneural injection could occur.
Central nervous system (CNS) and cardiovascular system toxicity are dose and time dependent; most severe reactions are a result of intravascular injection. The quicker the plasma levels rise, the greater the chance systemic problems will occur. Initial CNS symptoms are tinnitus, metallic taste, light-headedness, and perioral numbness. With higher levels, muscle twitching, tremors, tonic–clonic seizures, loss of consciousness, and respiratory arrest may occur. Benzodiazepines will raise the CNS threshold and can be used to terminate seizure activity. Protection of the airway with intubation and ventilation to ensure oxygenation is paramount in caring for patients with CNS toxicity.1
Cardiovascular toxicity is less common than CNS toxicity, but occurs as a result of decrease in myocardial peripheral smooth muscle conduction. There is prolongation of conduction, increasing the PR and QRS intervals, along with suppression of the sinoatrial and atrioventricular nodes, causing bradycardia, conduction block, and cardiac arrest. Bupivacaine has greater cardiotoxicity than lidocaine. Similar to CNS toxicity, intubation and mechanical ventilation, followed by Advanced Cardiac Life Support (ACLS) protocol for resuscitation, should be instituted.1
Sodium bicarbonate can be added to local anesthetic solutions to increase the rate of onset and decrease the pain at the injection site.1
Antimicrobial preservatives, such as methylparaben and ethylparaben, are often added to multidose vials. Anesthetics with these additives can be used for local infiltration, but should not be used for IV regional (bier block) anesthesia or spinal/epidural anesthesia. Antioxidants such as sodium ethylenediaminetetraacetic acid can be added to prevent oxidation and slow their degradation.1
Epinephrine is commonly added to local anesthetics. It functions by increasing the time of onset, limits the systemic absorption, and thus increasing the maximum dose, and increases the duration of action (Chapter 12). It is commonly used in concentrations of 1:200,000 (range 1:100,000 to 1:400,000).2
Historically, it was taught that epinephrine should not be used in the hand or finger for fear of vasoconstriction and finger necrosis. A critical look at the evidence indicates that case reports are mostly prior to the 1950s and associated with procaine and cocaine injections with epinephrine.3 The current evidence clearly demonstrates that epinephrine can be safely used in the fingers.3-9 If reperfusion is delayed, 0.5% phentolamine mesylate can be used to reverse the effects of epinephrine. It is injected locally, reversibly blocking the alpha-1 receptors, and causing vasodilation.10,11Phentolamine has a short half-life, so repeat injection may be necessary.
Brachial plexus blocks can be used for most procedures in the upper extremity. These can be used as the sole anesthetic agent, or combined with sedation or general anesthesia, depending on the patient, surgeon, and anesthesiologist preference. Chan et al. compared infraclavicular block anesthesia with general anesthesia and demonstrated an increase in time to begin the surgical portion of the case. The block took 5 to 10 minutes to perform and 15 to 25 minutes to reach a level for surgical stimulation.12 The trade-off for this increased time to begin the procedure is decreased recovery time, leading to faster discharge, elimination of anesthetic gases, and thus, less potential for nausea and vomiting, and better early postoperative pain relief. Of course, the onset of pain will occur as the block wears off and this may be in the middle of the night, making it important to instruct the patient on use of postoperative pain medications. The most efficient use of regional anesthesia is a system where the anesthesiologists can perform the block about 30 minutes prior to starting the procedure to allow adequate time for the block to take effect. This can be performed in a designated area, such as a “block area or room,” to allow the most efficient use of the operating room.
Brachial plexus blocks can be performed at four anatomical sites: two above the clavicle (interscalene and supraclavicular), one below (infraclavicular), and one in the arm (axillary). Ultrasound or nerve stimulation is commonly used to assist with localization of the needle, increasing safety and effectiveness of the block.2
The interscalene block allows for anesthesia at a proximal level, away from the lung, making this location good for shoulder surgery with a low incidence of pneumothorax. Anesthesia of the inferior trunk (C7-T1) may be incomplete, necessitating ulnar nerve block for procedures involving the elbow, wrist, and hand.13
Supraclavicular block allows for complete block with rapid onset due to the anatomical position of the trunks of the brachial plexus at this level, but the incidence of pneumothorax ranges between 0.5% and 6%. This technique is less desirable in obese patients as it is more challenging to identify anatomic landmarks and in tall thin patients, who often have a high lung apex. The phrenic, recurrent laryngeal nerves and cervical sympathetic chain are in close proximity, making it likely one or more of these nerves will also be anesthetized with a block at this level.13
Infraclavicular block provides ideal anesthesia for procedures at the elbow and distal as incomplete blocks are less common. The brachial plexus is deeper at this level, making the procedure more challenging for the anesthesiologist and potentially more uncomfortable for the patient. The axillary artery and vein are in close proximity and their relationships to the clavicle make it more difficult to diagnose bleeding/hematoma or provide direct compression in the event of bleeding.13
The axillary block can be completed with a transarterial approach, where the needle is passed through the artery and local anesthetic deposited directly behind the artery and anterior to the artery upon removal of the needle. The brachial plexus is well compartmentalized at this level, so incomplete blocks are more common. The musculocutaneous nerve exits the sheath higher, so a separate injection must be completed, or the upper arm tourniquet will not be well tolerated. Complications are rare and when they occur are usually the result of an intravascular injection.13
Intravenous Regional Anesthesia (Bier Block)
IV regional anesthesia can be used for procedures of short duration (typically 60 minutes or less), due to tourniquet pain. Using a double tourniquet can prolong procedure time to approximately 90 minutes. The technique is relatively straightforward to perform, but tourniquet malfunction can be disastrous, as the entire volume of anesthetic may be released into the CNS. The mechanism of action is felt to be due to retrograde flow of local anesthetic through the vasovenosum to peripheral nerves and diffusion through venous channels to peripheral nerve endings. The tourniquet should remain inflated for 30 minutes to allow for anesthetic binding to the tissues and preventing rapid rise in systemic levels of anesthetic after deflation. The tourniquet should be “cycled down” with release and rapid reinflation to allow slow release of anesthetic into the circulation. Three cycles are sufficient, but the patient should be monitored during deflation for signs of CNS toxicity (tinnitus, metallic taste, and perioral numbness) and treated if present.13
PERIPHERAL NERVE BLOCKS
Peripheral nerve blocks can be used in conjunction with MAC/IV sedation or performed for procedures under straight local anesthesia. For procedures in the forearm, the nerve block is performed at the level of the elbow. The ulnar, median, and radial nerves can be blocked at this level, but the forearm also receives innervation from the medial and lateral brachial and antebrachial cutaneous nerves, so local infiltration in the surgical area is required in addition to the nerve block.
FIGURE 71.1. Ulnar nerve block at the level of the elbow (MED EPI, medial epicpondyle; OLE, olecranon).
Ulnar Nerve. The ulnar nerve passes through the groove between the medial epicondyle of the humerus and the olecranon and can be blocked in this area (Figure 71.1). Injection should be in the subcutaneous tissue and not directly in the groove because this is a tight space and inadvertent injection into the nerve could occur.
Median Nerve. The median nerve at the level of the elbow is located medial (ulnar) and superficial to the brachial artery, which is medial to the biceps tendon (Figure 71.2). Anesthetic is injected subcutaneously medial to the brachial artery. Care should be taken to prevent intra-arterial injection by aspirating prior to injection. If the artery is inadvertently entered, firm pressure should be a help for several minutes.
Radial Nerve. The radial nerve can be blocked at the level of the distal humerus or at the level of the antecubital fossa (Figure 71.3). There is variability in the branching of the radial nerve (i.e., the branches to the extensor carpi radialis longus, extensor carpi radialis brevis, and the sensory branch), making the proximal block more predictable.14 The nerve wraps around the humerus from posterior to lateral approximately 4 cm proximal to the lateral epicondyle. The needle is inserted until the humerus is contacted, then slightly withdrawn, and the anesthetic is injected.
FIGURE 71.2. Median nerve block at the elbow (BR ART, brachial artery).
FIGURE 71.3. Radial nerve block at the elbow. A. One alternative is injection approximately 4 cm proximal to lateral epicondyle along the course of the radial nerve from the posterior to lateral aspect of the humerus in the spiral groove. B. A second alternative is injection lateral to the biceps tendon at the level of antecubital crease.
Alternatively, the nerve can be blocked at the level of the antecubital fossa. The radial nerve is located lateral and deep to the biceps tendon and is blocked by injecting the anesthetic in this area. An incomplete block due to the anatomical variability of the sensory branch may occur.
Ulnar Nerve. The ulnar nerve at the level of the wrist is located deep to the flexor carpi ulnaris (FCU) tendon and ulnar to the ulnar artery (Figure 71.4). The nerve can be blocked from the radial or ulnar aspect of the FCU by injecting deep to the tendon; the ulnar approach avoids the ulnar artery. Care is taken to avoid injecting into the artery by aspirating prior to injection. The dorsal sensory branch of the ulnar nerve typically branches 6 to 8 cm proximal to the ulnar head, so this nerve is blocked along the ulnar subcutaneous border of the wrist or hand.14
Median Nerve. The median nerve is blocked at the wrist by injecting anesthetic just ulnar to the palmaris longus (PL) tendon (Figure 71.5). When the PL is absent, the injection can be given along the axis of the ring finger. The injection is just deep to the antebrachial fascia. The palmar cutaneous branch exits the nerve proximally and runs in the subcutaneous tissue at this level, so subcutaneous injection should also be performed.
FIGURE 71.4. Ulnar nerve block at the wrist (FCR, flexor carpi radialis tendon; PL, palmaris longus tendon; FCU, flexor carpi ulnaris tendon).
Radial Nerve. The sensory branch of the radial nerve (SBRN) exits from the brachioradialis tendon and runs subcutaneously along the radial aspect of the wrist (Figure 71.6). Subcutaneous infiltration at this level will block the SBRN and branches of the lateral antebrachial cutaneous nerve, providing anesthesia to the dorsal radial aspect of the hand.
The common and proper digital nerves can be blocked in the palm and this approach can be used to block multiple digits. The dorsal innervation proximal to the distal interphalangeal (DIP) joint requires a dorsal subcutaneous injection as the dorsal aspect of the digits proximal to the DIP joint is from the SBRN in the thumb, index, middle, and radial half of the ring finger and the dorsal sensory branch of the ulnar nerve in the ulnar half of the ring and small fingers. The individual digits can be blocked from the volar aspect by injecting along the radial and ulnar aspects of the digits until the anesthetic flows in the subcutaneous region across the dorsal aspect of the digit.
FIGURE 71.5. Median nerve block at the wrist (FCR, flexor carpi radialis tendon; PL, palmaris longus tendon; FCU, flexor carpi ulnaris tendon).
FIGURE 71.6. Radial sensory nerve block at the wrist (RSN, radial sensory nerve branches; FCR, flexor carpi radialis tendon; PL, palmaris longus tendon).
Several studies have looked at injection techniques for digital anesthesia.15-20 Accepted techniques include traditional digital block (TDB) technique, injecting from the dorsal aspect between the web space along each side of the digit; transthecal block (TTB), where the injection is from the volar aspect and the injection is within the flexor sheath, and subcutaneous infiltration from the volar aspect. The volar blocks do not anesthetize the dorsal branches from the radial or ulnar dorsal sensory nerves, so either a separate dorsal injection or advancing the needle between the metacarpals from the volar surface to deposit anesthetic in the dorsal subcutaneous tissue must be completed. All of these techniques can provide adequate anesthesia, so it becomes a matter of surgeon preference.
The best current evidence suggests that the single subcutaneous injection provides rapid onset of anesthesia and less pain than the TTB.20,21 The TDB technique requires two injections and has been shown to have slower onset20 and the research subjects preferred the single subcutaneous injection.
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