Initial Clinical Experience with Remifentanil, a New Opioid Metabolized by Esterases

Comment The observations in this interesting study are the first clinical data on remifentanil when it is administered as the analgesic component of an opioid-nitrous oxide-relaxant anesthetic. Remifentanil produced hemodynamic effects similar to fen-tanyl and other potent μ-agonists. However, remifentanil may possess a larger margin of safety than other opioid analgesics in terms of rapid recovery, even after a high-dose infusion. Although the final infusion rate was varied 80-fold from 0.025 μg/kg/min to 2μg/kg/min and the duration of anesthesia ranged from 1 to 6.8 hr, spontaneous breathing, responsiveness to voice, and extubation occurred within a few minutes in most cases. In a previous study, the pharmacokinetics of remifentanil were not greatly influenced by patient gender, weight, or age.1 Moreover, the circulating esterases responsible for remifentanil metabolism are distinct from the enzymes that metabolize succinyl-choline or acetylcholine; thus, the short duration of remifentanil may apply even in patients with deficient pseudocholinesterase activity. In addition, the pharmacokinetics of remifentanil in patients with impaired hepatic or renal function seem to be unchanged.2,3 Thus, remifentanil may offer appealing advantages as the opioid component of a balanced anesthetic when rapid emergence is desirable.