[Isoflurane and total oxygen consumption in spontaneously breathing dogs in basal metabolic conditions]

To study the metabolic effects of isoflurane, whole body oxygen consumption (VO2) was measured on 7 occasions in 7 dogs under standard conditions. The dogs were trained to lie unrestrained in the lateral position for the measurement of VO2 (STPD) in the unanaesthetized state. Blood gas tensions and pH of arterial blood, heart and respiratory rates, blood pressure, rectal temperature and CO2 production (VCO2) also were determined. The maximum VO2 (ml X kg-1 X min-1) of the alert and the minimum of the drowsy resting states averaged (+/- SE) 6.9 +/- 0.5 and 3.6 +/- 0.3 respectively. The calculated mean basal rate was 4.4 +/- 0.1 and VO2 during natural delta-sleep 2.8 +/- 0.3. With isoflurane and spontaneous ventilation VO2 averaged 4.1 +/- 0.2, 4.0 +/- 0.3 and 3.6 +/- 0.3 at 1, 1.5 and 2 Vol-% (inspired) respectively. During anaesthesia with isoflurane VO2 fluctuates between the calculated basal rate and that of natural sleep.