Effect of midazolam pretreatment on desflurane MAC(BAR) at an effect-site concentration of remifentanil 1.0 ng/ml

ABSTRACT

BACKGROUND: The goal of this prospective study was to determine the effect of midazolam pretreatment on the desflurane requirement for blunting the sympathetic response after surgical incision (minimum alveolar concentration blockade of adrenergic responses, MAC(BAR)) when desflurane is combined with a target-controlled concentration of remifentanil at 1 ng/ml. METHODS: Sixty-five patients aged 30 to 60 years with American Society of Anesthesiologists physical status of I or II who were undergoing general anesthesia for thyroidectomy were registered for this study. The patients were randomly allocated to receive either 30 microg/kg of midazolam (Group M) or isovolemic saline (Group C) intravenously before anesthetic induction. All patients were anesthetized with propofol, rocuronium, desflurane and remifentanil at a target-controlled effect-site concentration of 3 ng/ml at intubation followed by 1 ng/ml throughout the study. Sympathetic responses to surgical incision were determined 10 minutes after stabilization of end-tidal desflurane and target-controlled remifentanil concentrations. The predetermined end-tidal desflurane concentrations and MAC(BAR) for each group were determined using an up-and-down sequential allocation technique. RESULTS: The MAC(BAR) of desflurane with 1 ng/ml remifentanil concentration was 7.1 and 6.8% without and with midazolam pretreatment, respectively, using Dixon's up-and-down method (P = 0.755). CONCLUSIONS: Midazolam administered intravenously before anesthetic induction does not impact the MAC(BAR) of desflurane with an effect-site concentration of remifentanil 1.0 ng/ml.