The independent metabolic effects of enflurane anaesthesia and surgery

The metabolic effects of enflurane anaesthesia (1MAC) in air/oxygen were investigated in six healthy unpremedicated women scheduled for total abdominal hysterectomy (TAH). The changes in acid-base status, CO2 production, and circulating concentration of total protein, albumin and a variety of metabolites (glucose, lactate, glycerol and alanine) were measured before and during a 2-h period of anaesthesia alone, during 1 h of anaesthesia plus surgery, and in the recovery period. The subjects were maintained normothermic (36.5 +/- 0.3 degrees C), and with an arterial SaO2 above 95% throughout the period of study. The circulating concentration of all metabolites changed little as a result of anaesthesia alone, but the glucose and lactate levels rose rapidly after the onset of surgery (P less than 0.05). Plasma albumin and total protein concentration decreased during the study, reaching values that were significantly lower than the pre-anaesthetic values (P less than 0.05). CO2 production decreased by 9% during anaesthesia and surgery, but returned towards preoperative values during recovery. This study provides no evidence of any significant effect of enflurane anaesthesia alone on human intermediary metabolism. Most of the changes in circulating metabolite concentrations observed during and after anaesthesia and surgery are likely to be due to the surgical stress.