Desflurane potentiates atracurium in humans: a comparative study with isoflurane

(1) To evaluate the neuromuscular effects of desflurane and its interactions with atracurium and (2) to compare desflurane and isoflurane in these effects.

Sequential entry of informed and consenting patients randomly assigned to receive desflurane (n = 25) or isoflurane (n = 25).

Operating suite of a county-university medical center.

Fifty adults, ASA physical status I, undergoing elective orthopedic surgery.

Following establishment of steady desflurane or isoflurane anesthesia, at 1.25 minimum alveolar concentration (MAC) exhaled for 15 minutes, a randomly predetermined dose of atracurium (0.05, 0.1, or 0.15 mg/kg) was injected intravenously (IV). At the end of surgery, neostigmine 0.04 mg/kg IV was given to reverse the residual block. The neuromuscular effects of desflurane or isoflurane alone, and the dose-response relationship, time course, and reversibility of the neuromuscular effects of atracurium with either anesthetic, were examined in detail and compared using electromyographic quantification of the response of the first dorsal interosseous muscle to train-of-four (TOF) stimulation of the ulnar nerve.

TOF fade and depression of the first response (T1) of the TOF were measured in response to desflurane or isoflurane, atracurium, and neostigmine. Desflurane caused more TOF fade than isoflurane prior to atracurium administration. The TOF ratios were 0.91 +/- 0.02 and 0.98 +/- 0.01, respectively (p < 0.05). For other measured neuromuscular parameters, atracurium-induced depression tended to be greater in the presence of desflurane than in the presence of isoflurane, but none of the measured differences reached the statistical significance level of p < 0.05. The ED50, ED95, and 25-75% recovery index of atracurium were 0.038 mg/kg (95% confidence level; range 0.030 to 0.047 mg/kg), 0.11 mg/kg (0.095 to 0.14 mg/kg), and 31 +/- 4 minutes (means +/- SEM) with desflurane anesthesia, versus 0.043 mg/kg (0.035 to 0.052 mg/kg), 0.13 mg/kg (0.11 to 0.16 mg/kg), and 23 +/- 4 minutes with isoflurane anesthesia (p = 0.1-0.2). Continuation of either anesthetic at 1.25 MAC prevented complete recovery of neuromuscular functions spontaneously or following neostigmine 0.04 mg/kg.

In ASA physical status I adults, 9% desflurane has neuromuscular effects equal to or slightly in excess of those of 1.6% isoflurane.