Introduction
Perioperative peripheral nerve injury is a significant source of morbidity for patients, and the second most frequent cause of professional liability for anesthesiologists, accounting for 16% of claims in the American Society of Anesthesiologists (ASA) closed claims project database. The incidence of postoperative peripheral nerve dysfunction is estimated at 0.1% to 0.15%, or 1 in 1000 to 1500 anesthetics. A more recent study of more than 380,000 anesthetics observed an incidence of 0.03% for postoperative nerve injuries.
The etiology of perioperative nerve damage is largely unknown. Injuries to the nerves of the brachial plexus or sciatic nerve may be secondary to stretching and/or compression with malpositioning of the patient. In contrast, ulnar nerve injury may occur despite protective padding and careful positioning. Direct trauma from needles or instruments and chemical toxicity of injected local anesthetics or vasoconstrictors may be implicated in nerve damage after regional anesthetic techniques. However, there are very few prospective studies on the genesis or prevention of perioperative neuropathy. None of these is randomized and blinded. The relationship between conventional perioperative care and development of postoperative neuropathy is poorly understood.
Because of the absence of randomized controlled trials and a paucity of epidemiologic studies, the evidence on which practice patterns for prevention of perioperative peripheral neuropathy are based is largely consensus opinion. Using expert consensus, the ASA Task Force on Prevention of Perioperative Peripheral Neuropathies formed guidelines regarding perioperative positioning of the patient, use of protective padding, and avoidance of contact with hard surfaces or supports to reduce perioperative neuropathies. These guidelines were revised in 2011 ( Box 29-1 ). However, even with close adherence to these recommendations, many peripheral neuropathies, especially those involving the ulnar nerve, may not be preventable.
Preoperative History and Physical Assessment
When judged appropriate, it is helpful to ascertain that patients can comfortably tolerate the anticipated operative position.
Specific Positioning Strategies for the Upper Extremities
Arm abduction in supine patients should be limited to 90 degrees.
Patients who are positioned prone may comfortably tolerate arm abduction greater than 90 degrees.
Supine Patient with Arm on an Arm Board
The upper extremity should be positioned to decrease pressure on the postcondylar groove of the humerus (ulnar groove).
Either supination or the neutral forearm positions facilitates this action.
Supine Patient with Arms Tucked at Side
The forearm should be in a neutral position.
Flexion of the elbow may increase the risk of ulnar neuropathy, but there is no consensus on an acceptable degree of flexion during the perioperative period.
Prolonged pressure on the radial nerve in the spiral groove of the humerus should be avoided.
Extension of the elbow beyond the range that is comfortable during the preoperative assessment may stretch the median nerve.
Periodic perioperative assessments may ensure maintenance of the desired position.
Specific Positioning Strategies for the Lower Extremities
Stretching of the Hamstring Muscle Group
Positions that stretch the hamstring muscle group beyond the range that is comfortable during the preoperative assessment may stretch the sciatic nerve.
Limiting Hip Flexion
Because the sciatic nerve or its branches cross both the hip and the knee joints, extension and flexion of these joints, respectively, should be considered when determining the degree of hip flexion.
Neither extension nor flexion of the hip increases the risk of femoral neuropathy.
Prolonged pressure on the peroneal nerve at the fibular head should be avoided.
Protective Padding
Padded Arm Boards
Padded arm boards may decrease the risk of upper extremity neuropathy.
Chest Rolls
The use of chest rolls in the laterally positioned patient may decrease the risk of upper extremity neuropathy.
Padding at the Elbow
Padding at the elbow may decrease the risk of upper extremity neuropathy.
Padding to Protect the Peroneal (Fibular) Nerve
The use of specific padding to prevent pressure of a hard surface against the peroneal nerve at the fibular head may decrease the risk of peroneal neuropathy.
Complications from the Use of Padding
The inappropriate use of padding (e.g., padding too tight) may increase the risk of perioperative neuropathy.
Equipment
The use of properly functioning automated blood pressure cuffs on the arm (i.e., placed above the antecubital fossa) does not change the risk of upper extremity neuropathy.
The use of shoulder braces in a steep head-down position may increase the risk of perioperative neuropathies.
Postoperative Assessment
A simple postoperative assessment of extremity nerve function may lead to early recognition of peripheral neuropathies.
Documentation
Documentation of specific perioperative positioning actions may be useful for continuous improvement processes and may result in improvements by: (1) helping practitioners focus attention on relevant aspects of patient positioning and (2) providing information on positioning strategies that eventually leads to improvements in patient care.
Therapies/Options Available to Reduce Peripheral Neuropathy
Understanding the etiology and pathogenesis of neuropathy is essential for formulating ways of preventing or minimizing its occurrence. A lack of understanding regarding the development of postoperative peripheral nerve dysfunction is the major impediment in developing preventive steps.
Based on current knowledge of the pathogenesis of perioperative neuropathy, several recommendations have been made to prevent its occurrence. These include a preoperative screening to detect any subclinical neuropathy, preoperative history and physical examination directed at defining the comfortable range of stretching and movement at different joints, meticulous attention to avoiding intraoperative compression of superficial nerves, padding of the extremities and points at which nerves may get compressed, measures aimed at reducing stretching of the nerves, periodic intraoperative checking for optimal positioning of the extremities, and performing regional blocks with a nerve stimulator while the patient is awake. However, there is no definitive scientific evidence that these maneuvers are effective in preventing perioperative neuropathy.
Evidence
When studying the evidence for causation and prevention of peripheral neuropathy, one must consider the different criteria used to diagnose neuropathy in each of the studies. Although transient sensory neurologic dysfunction lasting less than 2 weeks is not uncommon after anesthesia and surgery, permanent disabling nerve injuries are infrequent.
Upper Extremity Neuropathies
Postoperative neuropathies involving brachial plexus nerves and ulnar nerve are observed more commonly as compared with lower extremity neuropathies. As a result, they have been studied to a larger extent.
Ulnar Neuropathy
The ulnar nerve is the most common site of postoperative peripheral nerve damage, accounting for 28% of claims for anesthesia-related nerve injuries in the ASA closed claims database. The incidence of ulnar nerve dysfunction is estimated to be between 0.26% and 0.5% in prospective studies of postsurgical patients ( Table 29-1 ). Ulnar neuropathy has been documented not only in surgical patients but also in medical inpatients and outpatients, irrespective of whether general anesthesia, regional anesthesia, or sedation-monitored anesthesia care was administered.
| Author, Year | Anesthesia Technique | Study Design | Incidence of Neuropathy | Comment |
|---|---|---|---|---|
| Dhuner, 1950 | GA/spinal | Retrospective review of 30,000 cases | Ulnar neuropathy in 8 patients | Transient paresis lasting a few weeks in 7 cases |
| Alvine, 1987 | GA for orthopedic, cardiac, urology, general surgical procedures | Prospective study in 6538 patients | Ulnar neuropathy in 0.26% patients | Subclinical ulnar neuropathy may become symptomatic secondary to perioperative maneuvers and manipulations |
| Warner, 1994 | GA, sedation, regional | Retrospective review of 1,129,692 cases | Ulnar neuropathy in 1 per 2729 patients (0.04%) | No correlation with anesthetic technique or patient position; males, extremes of body habitus, prolonged hospital stay had higher incidence |
| Warner, 1999 | GA, sedation, regional | Prospective study in 1502 patients | Ulnar neuropathy in 7 per 1502 patients (1 in 215 patients) (0.5%) | More frequent in men 50-75 yr of age; signs and symptoms develop 2-7 days after surgery |
| Warner, 2000 | Medical inpatients | Prospective study in 986 patients | Ulnar neuropathy in 2 of 986 patients (0.2% incidence) | Prolonged bed rest in supine position and elbow flexion may be causative |
| Lee, 2002 | GA | Prospective study in 203 orthopedic patients | Six cases (3% incidence) of ulnar neuropathy | Higher incidence in tilted patients in the lowermost adducted arm |
| Navarro-Vicente, 2012 | Open and laparoscopic colorectal surgeries | Prospective study in 2304 patients | Upper extremity neuropathy in 5 patients (0.2% incidence) | Adoption of tucked position and vacuum bags instead of shoulder braces has eliminated neuropathies thus far |
Male gender, extremes of body habitus, and prolonged hospitalization are important risk factors for perioperative ulnar neuropathy. The male predisposition may be explained by gender-related anatomic variations in the cubital tunnel at the elbow that render the ulnar nerve more sensitive to injury. Men have a 50% larger tubercle of the ulna, thicker retinaculum, and a shallow cubital tunnel, whereas women have 2 to 9 times more fat content in the cubital tunnel. It is speculated that these anatomic differences may predispose the ulnar nerve to ischemia, by either direct compression or a reduction in blood flow by compression of the ulnar collateral artery and vein. Patients with perioperative neuropathy have a high incidence of contralateral nerve conduction dysfunction, suggesting that a subclinical neuropathy may become symptomatic as a result of manipulations during the perioperative period.
The risk of ulnar nerve injury may be increased by flexion of the elbow and pronation of the forearm (see Table 29-1 ). The ASA task force concluded that flexion of the elbow may increase the risk of ulnar neuropathy, but there is no consensus on an acceptable degree of flexion during the perioperative period. This opinion is supported by anatomic evidence of a reduction in the cross-sectional contour of the cubital tunnel and a sevenfold increase in pressure within the tunnel, to a range that can compromise the intraneural circulation. Pronation of the forearm increases the pressure over the ulnar groove. Supination of the forearm produces the least amount of pressure, whereas a neutral position results in an intermediate value. Supination also “lifts” the cubital tunnel and ulnar nerve away from a contact surface. Almost half of the men who experience pressure on their nerve sufficient to impair the electrophysiologic function do not perceive symptoms. A higher incidence of ulnar neuropathy is also found in tilted patients in the lowermost adducted arm, which is speculated to occur because internal rotation of the shoulder rotates the ulnar nerve toward compressive forces at the elbow.
The ASA Task Force on Prevention of Perioperative Peripheral Neuropathies (see Box 29-1 ) made the following recommendations to prevent ulnar nerve injury: (1) position arms to decrease pressure on the ulnar groove, (2) use a neutral forearm position when arms are tucked at the sides, (3) use supination or a neutral forearm position when the arms are abducted on armboards, and (4) use padded armboards and padding at the elbow. The task force advised that flexion of the elbow may increase the risk of ulnar neuropathy, but the acceptable degree of elbow flexion remains unclear. Periodic checking and documentation were also recommended. Properly functioning blood pressure cuffs on the upper arms do not affect the risk of upper extremity neuropathy.
Despite the theoretical value of these precautions in positioning the arms, there is no evidence that these practices decrease the risk of postoperative ulnar neuropathy. To the contrary, the evidence suggests that ulnar nerve damage may occur despite padding and placement of the patient’s arms in supination.
Brachial Plexus Injury
Injury to the brachial plexus is the second most common nerve injury, responsible for 20% of claims for anesthesia-related nerve injuries in the ASA closed claims analysis. The perioperative incidence of brachial plexus neuropathy is estimated at 0.2% to 0.6%. Injury to the brachial plexus is most commonly reported after procedures involving a median sternotomy, especially with dissection of the internal mammary artery ; Trendelenburg position, especially with shoulder braces for support ; and after surgery in the prone position.
Most brachial plexus nerve injuries are caused by stretching and traction on the plexus. The anatomic features that make the brachial plexus most susceptible to injury include the following: (1) the nerve roots of the brachial plexus run a long, mobile, and superficial course between two firm points of fixation—the intervertebral foramina above and the axillary fascia below, (2) its close anatomic relationships with a number of freely movable bony prominences, and (3) the plexus runs its course through the limited space between the first rib and the clavicle. The first two features make the brachial plexus more susceptible to stretch-induced injury, whereas the third one (along with fracture and/or displacement of the first rib) is generally implicated in a direct or compression injury after cardiac surgery.
Arm Position.
Brachial plexus neuropathy has been reported after arm abduction equal to or greater than 90 degrees. Positions that induce stretching of the brachial plexus include extension and lateral flexion of the head to one side, allowing the arm to sag off the operating table, or use of a shoulder roll or gall bladder rest to “bump” the patient to one side. Contralateral cervical lateral flexion, lateral rotation of the shoulder, fixation of the shoulder girdle in a neutral position, and wrist extension also stretch the brachial plexus. Simultaneous application of these positions has a cumulative effect. Ninety-six percent of ASA members felt that limiting the arm abduction to 90 degrees in supine patients may reduce the risk of brachial plexus injury. Navarro-Vicente et al report elimination of brachial plexus injuries during laparoscopic surgeries when they adopted the practice of tucking arms by the side and using vacuum bags (bean bags) instead of shoulder braces. The ASA Task Force on Prevention of Perioperative Peripheral Neuropathies concluded that arm abduction should be limited to 90 degrees in supine patients (see Box 29-1 ).
Shoulder Braces.
The use of shoulder braces to stop patients from sliding down when placed in a steep Trendelenburg position has been associated with development of postoperative brachial plexus damage. Shoulder braces can compress the brachial plexus against the numerous bony and rigid structures within the shoulder complex. The danger is even greater when the arm is abducted, which causes the brace to act as a fulcrum and stretch the plexus. Fixation of the shoulder (caused by use of shoulder braces even in the recommended position over the acromioclavicular joints) loads the nerves of the upper extremity and reduces the range of elbow extension in the brachial plexus tension test. The ASA Task Force on Prevention of Perioperative Peripheral Neuropathies concurred that shoulder braces in a steep head-down position may increase the risk of brachial plexus neuropathies (see Box 29-1 ).
Prone Position.
Placement of a patient into the prone position can also be accompanied by a stretch injury to the brachial plexus. Once a prone position is established, the arms may be positioned either alongside the torso or extended above the head. In the presence of symptoms suggestive of thoracic outlet syndrome (i.e., paresthesia, numbness, or pain on raising hands above the head), arms should be restrained by the side of the body to avoid stretching of the brachial plexus. Closure of retroclavicular space in the prone position can occur as a result of dorsal and caudal displacement of the clavicle by the chest roll, causing compression of the brachial plexus between the thorax and clavicle. The ASA Task Force on Prevention of Perioperative Peripheral Neuropathies concluded that patients who are positioned prone may comfortably tolerate arm abduction greater than 90 degrees (see Box 29-1 ).
Lateral Decubitus Position.
Compression of the brachial plexus between the thorax and the head of the humerus of the downside extremity can also occur in the lateral decubitus position. This can possibly be reduced by placing a roll under the chest wall just caudad to the axilla, with the aim of elevating the rib cage off the table and freeing the dependent shoulder. The ASA Task Force on Prevention of Perioperative Peripheral Neuropathies recommended use of chest rolls in laterally positioned patients to reduce the risk of upper extremity neuropathies (see Box 29-1 ).
Other Upper Extremity Neuropathies
Radial Nerve Injury
The radial nerve is susceptible to compression injury as it passes dorsolaterally around the middle and lower thirds of the humerus in the musculospiral groove. The nerve can be compressed approximately 5 cm above the lateral epicondyle of the humerus between an external object, such as the vertical bar of an anesthesia screen, an improperly positioned tourniquet, or the distal edge of a blood pressure cuff, and the underlying bone. The ASA Task Force on Prevention of Perioperative Peripheral Neuropathies recommended that prolonged pressure on the radial nerve in the spiral groove of the humerus should be avoided (see Box 29-1 ).
Median Nerve Dysfunction
Isolated median nerve damage in the perioperative setting is relatively uncommon, and the mechanism is poorly understood. Needle trauma during venipuncture or intravenous cannulation in the antecubital fossa is possible. Median nerve dysfunction is predominantly seen in muscular men, in the 20- to 40-year-old age group, who are unable to fully extend their elbows because of their large biceps and relatively inflexible tendons. The ASA Task Force on Prevention of Perioperative Peripheral Neuropathies concluded that extension of the elbow beyond a comfortable range may stretch the median nerve (see Box 29-1 ).
Long Thoracic Nerve Damage
Long thoracic nerve dysfunction is an infrequent neuropathy. The absence of any apparent mechanism of injury in most of these cases has led to the postulation that a coincidental infectious neuropathy may be responsible for the postoperative long thoracic nerve dysfunction.
Lower Extremity Neuropathy
Postoperative nerve lesions in the lower extremity occur infrequently and are poorly studied ( Table 29-2 ). In the analysis of closed claims for nerve damage, Cheney et al reported 23 cases of sciatic nerve injuries, of which 10 were associated with the use of the lithotomy position and two with the frog-leg position for surgery. Warner et al prospectively studied 991 patients undergoing surgery in a lithotomy position and observed a 1.5% incidence of lower extremity neuropathies. Of the 15 patients who developed neuropathies, the obturator nerve was involved in five patients, the lateral femoral cutaneous nerve in four patients, the sciatic nerve in three patients, and the peroneal nerve in three patients, which indicates that multiple nerves are affected with similar frequency. All the neuropathies were purely sensory.
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