ANESTHETIC POTENCY AND CARDIOPULMONARY EFFECTS OF SEVOFLURANE IN GOATS - COMPARISON WITH ISOFLURANE AND HALOTHANE

The anesthetic potency and cardiopulmonary effects of sevoflurane were compared with those of isoflurane and halothane in goats. The (mean /- SD) minimal alveolar concentration (MAC) was 0.96 +/- 0.12% for hal othane, 1.29 +/- 0.11% for isoflurane, and 2.33 +/- 0.15% for sevoflur ane. Cardiopulmonary effects of sevoflurane, halothane and isoflurane were examined at end-tidal concentrations equivalent to 1, 1.5 and 2 M AC during either spontaneous or controlled ventilation (SV or CV). Dur ing SV, there were no significant differences in respiration rate, tid al volume and minute ventilation between anesthetics. Dose-dependent d ecreases in both tidal volume and minute ventilation induced by haloth ane were greater than those by either sevoflurane or isoflurane. Hyper capnia and acidosis induced by sevoflurane were not significantly diff erent from those by either isoflurane or halothane at 1 and 1.5 MAC, b ut were less than those by halothane at 2 MAC. There was no significan t difference in heart rate between anesthetics during SV and CV. Durin g SV, all anesthetics induced dose-dependent decreases in arterial pre ssure, rate pressure product, systemic vascular resistance, left ventr icular minute work index and left ventricular stroke work index. Syste mic vascular resistance with isoflurane at 2 MAC was lower than that w ith sevoflurane. During CV, sevoflurane induced dose-dependent circula tory depression (decreases in arterial pressure, cardiac index, rate p ressure product, systemic vascular resistance, left ventricular minute work index and right ventricular minute work index), similar to isofl urane. Halothane did not significantly alter systemic vascular resista nce from 1 to 2 MAC.