Duration of vecuronium-induced neuromuscular block can be predicted by change of skin temperature over the thenar muscles.

PURPOSE

The purpose of this study was to clarify the relationship between skin temperature over the thenar muscles and the duration of action of vecuronium measured acceleromyographically at the thumb in anesthetized patients.

METHODS

In 15 patients undergoing elective open abdominal surgery under propofol, fentanyl, and nitrous oxide anesthesia, train-of-four (TOF) stimuli were delivered over the ulnar nerve at 2 Hz every 15 s, and the degree of neuromuscular block was measured acceleromyographically at the thumb. Each patient received an intubating dose of vecuronium 0.1 mg x kg(-1), followed by maintenance doses of 0.02 mg x kg(-1) administered repeatedly whenever the first twitch of TOF responses had recovered to 25% of control. The interval between maintenance doses was defined as the clinical duration (DUR25). The median values of skin temperature (ST) over the ipsilateral thenar muscles and esophageal temperature (ET) were recorded during the action of the first and all subsequent maintenance doses. The relationships between change in temperature and change in DUR25 were analyzed.

RESULTS

Whereas ET showed only minor changes (median, -0.3 degrees C), ST fluctuated markedly between +0.9 degrees and -6.3 degrees C (median, -1.4 degrees C). Increase and decrease were also seen in a series of DUR25s, as expected from the changes in ST. The median values of DUR25 produced by the first and last maintenance vecuronium doses were 21.5 and 32.3 min, respectively. A negative linear correlation was found between the change in DUR25 and that in ST, demonstrating that DUR25 increased by 20% of baseline with each 1 degrees C decrease in ST.

CONCLUSION

Our results show that peripheral ST decreases considerably during open abdominal surgery without reduction in core temperature, and the decrease contributes to the potentiation of neuromuscular block in the periphery during propofol, fentanyl, and nitrous oxide anesthesia.