From the Guidelines
The most commonly injured nerve under general anesthesia is the ulnar nerve (option b). This is due to its susceptibility to compression injury during surgical procedures, particularly when patients are positioned in a way that puts pressure on the cubital tunnel at the elbow. According to 1, older patients are at a higher risk of peripheral nerve injuries, including the ulnar nerve, when supine. Key factors that contribute to ulnar nerve injury include:
- Compression against the medial epicondyle of the humerus when arms are extended on armboards
- Elbow flexion beyond 90 degrees
- Direct pressure on the medial aspect of the elbow To prevent ulnar nerve injuries, it is crucial to:
- Properly pad pressure points
- Maintain the elbow in less than 90 degrees of flexion
- Avoid prolonged pressure on the medial aspect of the elbow As noted in 1, probable sites of nerve injury should be comprehensively padded before the start of surgery and assessed routinely every 30 minutes throughout surgery to minimize the risk of perioperative nerve injuries.
From the Research
Nerve Injury Under General Anesthesia
- The most commonly injured nerve under general anesthesia is the ulnar nerve, as stated in studies 2, 3, 4.
- The ulnar nerve is particularly susceptible to external pressure as it courses through the superficial condylar groove at the elbow, rendering it vulnerable to direct compression and ischemia 2.
- According to a closed claims analysis, the most frequent sites of injury were the ulnar nerve (28%), brachial plexus (20%), lumbosacral nerve root (16%), and spinal cord (13%) 4.
- Ulnar nerve injuries were more likely to have occurred in association with general anesthesia, whereas spinal cord and lumbosacral nerve root injuries were more likely to occur with regional techniques 4.
Prevention and Management
- Supination of the arm position is likely to minimize pressure over the ulnar nerve 2.
- With the forearm in neutral orientation, pressure over the ulnar nerve decreases as the arm is abducted between 30 degrees and 90 degrees 2.
- Recent automated detection technology in neuromonitoring with somatosensory evoked potentials may increase the ability to identify at-risk patients and individualize patient management 3.
- A practical and evidence-based approach to the management of suspected peripheral nerve injury is necessary, including factors which increase the susceptibility of nerves to damage 5.