Whole Body Oxygen Consumption in Awake, Sleeping, and Anesthetized Dogs

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Abstract
To study the metabolic effects of anesthesia, whole-body O2 consumption (.ovrhdot.VO2) was compared on 242 occasions in 6 dogs under standard conditions while awake, sleeping or anesthetized. The dogs were trained to lie unrestrained in the lateral position for the measurement of .ovrhdot.VO2 (STPD [standard temperature and pressure, dry]) in the unanesthetized state. Arterial blood gas tensions, pHa, heart rate and blood pressure also were determined. The maximum .ovrhdot.VO2 of the alert resting and the minimumum of the drowsy resting state averaged (.+-. SE) 5.57 .+-. 0.48 and 3.97 .+-. 041 ml/kg per min, respectively. .ovrhdot.VO2 was lowest and least fluctuating during natural sleep (2.46 .+-. 0.2 ml/kg per min). During deep anesthesia with methohexital, thiopental and etomidate, .ovrhdot.VO2 averaged (.+-. SE) 4.68 .+-. 0.26, 4.26 .+-. 0.28, and 4.77 .+-. 0.35 ml/kg per min during spontaneous ventilation (open-circuit flow-through technique) and 3.54 .+-. 0.27 ml/kg per min during controlled ventilation (open-circuit collection technique) with 2% halothane. Apparently, anesthesia reduces .ovrhdot.VO2 relative to the resting values of the alert state but increases it relative to that of natural sleep. Anesthetics should not be considered general metabolic depressants without qualification.