Localized hypothermia influences assessment of recovery from vecuronium neuromuscular blockade

The purpose of this study was to determine the extent to which localized hypothermia of a monitored extremity alters the assessment of recovery from vecuronium-induced neuromuscular blockade. Bilateral integrated evoked electromyographic (IEMG) responses were measured in the ulner distribution of 14 anaesthetized patients who had differing upper extremity temperatures as measured at the adductor pollicis to determine whether localized hypothermia alters the clinical assessment of spontaneous recovery from vecuronium-induced neuromuscular blockade. All patients received general anaesthesia with thiopentone, N2O/O2 and opioid; 11/14 patients received isoflurane for blood pressure control. Bilateral adductor pollicis, oesophageal and ambient temperatures, and IEMG evoked response (t1) expressed as percent unparalyzed control were recorded during the anaesthetic. The difference in evoked response between the warmer and the colder upper extremity was calculated at 25%, 50% and 75% spontaneous recovery from neuromuscular blockade in the warm extremity. Differences in temperature between extremities ranged from 0.2-11 degrees C. The difference in IEMG-evoked response between extremities was proportional to the difference in temperature, and there was a direct correlation (r = 0.78) between IEMG response and extremity temperature; IEMG response was absent when extremity temperature was less than 25 degrees C. We concluded that localized hypothermia in the monitored extremity decreases the IEMG-evoked response to vecuronium neuromuscular blockade; the greater the temperature decrease, the less the evoked response.(ABSTRACT TRUNCATED AT 250 WORDS)