Pharmacodynamic stability of a mixture of propofol and alfentanil.

We studied 40 patients undergoing body surface surgery in a double-blind manner to compare the pharmacodynamic stability of either mixed or separate infusions of propofol and alfentanil. No differences were found between the two groups in respiratory or cardiovascular variables during operation, or in requirements for analgesia after operation. The power of the study to determine a difference of 10 mm Hg in mean arterial pressure with a probability of 0.05 was 0.82 and for a difference of 1 kPa in end-tidal carbon dioxide partial pressure 0.89. We conclude that propofol and alfentanil may be administered by infusion from a single syringe without diminished or delayed effect of the opioid during anaesthesia and the first 4 h after operation.