Changes in oxygen consumption induced by fentanyl and thiopentone during balanced anaesthesia

Changes in whole body oxygen consumption due to bolus infusions of fentanyl and thiopentone given during "balanced anaesthesia" have been examined in 17 patients. It has been shown that fentanyl causes an average decrease in oxygen consumption of 4.9, 8.4, and 5.2 per cent at 5, 10 and 15 minutes after its infusion. Thiopentone causes an average decrease of 7.0, 8.8, and 1.9 per cent at 5, 10 and 15 minutes after infusion. It is believed that the effects of fentanyl and thiopentone on oxygen consumption are caused mainly by decreases in cerebral and myocardial oxygen consumption.