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 arterial pressure and heart rate 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 was induced by mask with sevoflurane in oxygen. Each chicken was endotracheally intubated, then controlled ventilation was started and the end-tidal CO2 partial pressure was maintained at 30 to 40 mm Hg. Body temperature was maintained at 39.5 degrees to 41.0 degrees C. The inspired and end-tidal sevoflurane concentration were monitored with a multigas monitor. Minimum anesthetic concentration was determined as the minimal end-tidal sevoflurane concentration which prevented gross purposeful movement in response to clamping 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 concentration were determined.

RESULTS

The minimum anesthetic concentration for sevoflurane was 2.21% + 0.32% (mean +/- SD). Mean arterial pressure and heart rate at minimum anesthetic concentration were 84 +/- 13 mm Hg and 150 +/- 58 beats/min, respectively. There was a dose-dependent decrease in arterial pressure. The heart rate did not change significantly over the range 1 to 2 x minimum anesthetic concentration. 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 concentration reported in mammals. When the concentration of sevoflurane is increased during controlled ventilation in chickens, decrease in arterial pressure should be expected.