QUANTITATION OF THE ENFLURANE-SPARING EFFECT OF ALFENTANIL DURING GENERAL-SURGERY

The authors quantitated the enflurane-sparing effect of alfentanil dur ing N2O/O-2 anaesthesia in 50 patients undergoing body surface surgery and in 50 patients undergoing upper abdominal surgery. Patients were assigned to one of five treatment regimens (10 patients each group, do uble-blind administration) as follows: placebo bolus followed by place bo infusion (group I); or alfentanil bolus (30 mu g kg(-1)) followed b y infusion of placebo (group II) or alfentanil, at the rate of 10 (gro up III), 20 (group IV), or 40 (group V) mu g kg(-1) h(-1). Anaesthesia was induced with thiopentone and vecuronium, and neuromuscular block was kept at 85-90% by continuous infusion of vecuronium. Increases in spontaneous electromyographic activity of neck muscles (NEMG) and in s ystolic blood pressure (SEP) served as criteria of inadequate anaesthe sia. When such increases occurred, enflurane was given in 0.2% steps ( end-tidal concentration) of 5 min each, until the increases were suppr essed. The relationship between increases in NEMG and increases in SEP was inconsistent: only 10% of the increases occurred simultaneously. With alfentanil, the consumption of enflurane decreased by as much as 70% (P<0.001) during superficial surgery and 50% (P<0.05) during abdom inal surgery.