POSITIONS

Supine Position

The supine position is the most commonly used position for surgical procedures. Because it is probably also the most commonly used position for natural sleep, it might be considered to be risk free. However, as shown in the ASA Closed Claims Database, ulnar neuropathies are the most common perioperative nerve injury, and most are associated with surgical procedures done in this position.^[1]

Positioning of the upper extremities in a supine patient has been addressed. Pressure on the ulnar groove and the spiral groove of the humerus where the radial nerve passes must be avoided, but is there an ideal position for the arms? The ASA Practice Advisory recommended that arm abduction should be limited to 90 degrees and that the forearm and hand be supinated or kept in neutral position (not pronated) when an armboard is used (see Table 28-3 ).^[2] Supination of the forearm was also recommended by Coppieters and colleagues^[9] after their studies involving the brachial plexus tension test and by Prielipp and coworkers,^[10] who used a computerized pressure sensing mat to determine positions that resulted in the least pressure over the ulnar groove.^{[9] [10]} Although the ASA Practice Advisory consensus was that padding at the elbow "may decrease" the risk of upper extremity neuropathy, it was pointed out that there were no data to prove this.^[2] In 27% of the 190 patients with ulnar nerve injuries in the ASA Closed Claims Database, elbow padding was specifically mentioned.^[1] Inappropriate use of padding (too tight) may increase the risk of perioperative neuropathy.

It is necessary in some cases to tuck one or both arms by a patient's side to improve surgical access. In obese patients, it can be quite difficult to tuck the patient's upper extremity by his or her abdomen and hips without risking excessive pressure on the hand or forearm. This practice has led to compartment syndromes in the hand and forearm that required surgical release in some patients. Difficulties can be compounded if an intravenous line infiltrates in an arm that is tucked beside the body. Neuromuscular blockade monitoring is also hampered when there is no access to an upper extremity.