Determination of the minimum anesthetic concentration and cardiovascular dose response for sevoflurane in chickens during controlled ventilation

Objective-To determine the minimum anesthetic concentration for sevoflurane and effects of various multiples of minimum anesthetic concentration on ar terial pressure and heart rare during controlled ventilation in chickens. Study Design-Prospective experimental study. Animals-Seven healthy chickens, 6 to 8 months old, weighing 1.6 to 3.4 kg. Methods-A rebreathing, semiclosed anesthetic circuit was used. Anesthesia w as induced by mask with sevoflurane in oxygen. Each chicken was endotrachea lly intubated, then controlled ventilation was started and the end-tidal CO 2 partial pressure was maintained at 30 to 40 mm Hg. Body temperature was m aintained at 39.5 degrees to 41.0 degrees C. The inspired and end-tidal sev oflurane concentration were monitored with a multigas monitor. Minimum anes thetic concentration was determined as the minimal end-tidal sevoflurane co ncentration which prevented gross purposeful movement in response to clampi ng a toe for 1 minute. After the determination, the cardiovascular effects of sevoflurane at 1.0, 1.5, and 2.0 times the minimum anesthetic concentrat ion were determined. Results-The minimum anesthetic concentration for sevoflurane was 2.21% + 0. 32% (mean +/- SD). Mean arterial pressure and heart rate at minimum anesthe tic concentration were 84 +/- 13 mm HE and 150 +/- 58 beats/min, respective ly. There was a dose-dependent decrease in arterial pressure. The heart rat e did not change significantly over the range 1 to 2 x minimum anesthetic c oncentration. No cardiac arrhythmias developed throughout the experiments. Conclusions and Clinical Relevance-The minimum anesthetic concentration for sevoflurane in chickens was within the range of minimum alveolar concentra tion reported in mammals. When the concentration of sevoflurane is increase d during controlled ventilation in chickens, decrease in arterial pressure should be expected. (C)Copyright 2000 by The American College of Veterinary Surgeons.