Injury to the peripheral nerve is a relatively uncommon but potentially serious complication of regional anesthesia. The fear of neurologic injury with nerve blocks may influence some practitioners as well as patients to avoid peripheral nerve blocks. The mechanisms by which nerve blocks may cause neural injury, along with evaluation and management, are discussed in separate chapters. Instead, this chapter discusses other potential causes of nerve injury as a number of possible factors may result in neurologic symptoms in the perioperative period.
To understand how the perioperative period may adversely influence nerves in extremities, even in subtle ways, ulnar nerve injuries reported in the anesthesiology literature over a decade ago are discussed.1,2 Injury to the ulnar nerve may be the most common nerve injury associated with general anesthesia and a significant source of litigation.3 These injuries appear to occur in the absence of obvious trauma to the involved extremity and are often delayed in their clinical presentation. The compression, pressure, and stretch at the level of the elbow all likely play a role in the pathophysiology,4,5 and preexisting neural compromise may also be a consideration.6 The deleterious effects of stretching or pressure on the ulnar nerve in an anesthetized patient can be prevented by simple maneuvers; for example, placing the extended forearm in supination, rather than pronation, was found to protect an unconscious patient against ulnar nerve injury.7
However, when an extremity is itself the site of surgical intervention, many more additional factors may conspire to result in a nerve injury. Initially, the skin is subjected to harsh antimicrobial solutions after clipping or shaving. A pneumatic tourniquet is often placed for these surgeries, with resultant distal ischemia and high pressures on the nerves of the proximal extremity. The surgery itself offers potential for sharp, blunt, or thermal trauma, which could adversely affect nerves, both at the level of small, local cutaneous branches near the incisions and at the level of peripheral nerve trunks. Non-physiologic body position may occur and held for long periods, typically involving the surgical extremity, but sometimes the nonsurgical ones as well. In the postoperative phase, long periods of immobilization in nonphysiologic positions have the potential to cause nerve stretch or compression, as do the immobilizing devices, especially in the presence of unavoidable dependent, posttraumatic edema. Combined with the lack of perception due to general anesthesia or postoperative opioid analgesics, as well as any loss of sensation caused by local anesthetics, there is risk for neural dysfunction or injury or alterations in sensory function (Tables 62–1 and 62–2).
Table 62–1.Potential intraoperative causes of nerve injury. |Favorite Table|Download (.pdf) Table 62–1. Potential intraoperative causes of nerve injury.
Surgical tourniquet (pressure, duration, cuff size/fit)
Positioning of operative extremity
Positioning of extremities
Retraction/stretch/pressure on nerves
Electrocautery thermal injury
Insertion of fixators ...