CARDIOPULMONARY EFFECTS OF ANESTHESIA INDUCED AND MAINTAINED WITH ISOFLURANE IN CATS

Objective-To determine the cardiopulmonary effects of anesthesia induc ed and maintained with isoflurane (ISO) in cats. Animals-8 healthy cat s between 1 and 5 years old. Procedure-Anesthesia was induced with ISO in oxygen. Two anesthetic depths were maintained in each cat, mean al veolar concentrations (MAC) were 1.3 and 2.0 times MAC, Ventilation wa s either spontaneous or controlled. Each cat received each treatment c ombination according to a latin square design. Cardiopulmonary measure ments were made after 20 minutes of constant conditions with each comb ination of anesthetic depth and ventilatory mode. Results-Cardiac inde x was not different between ISO doses, but 2.0 MAC ISO reduced arteria l blood pressure and total peripheral resistance. Cardiac index and sy stolic arterial blood pressure were reduced by controlled ventilation. The Pa-CO2 and pulmonary artery pressure were highest in association with 2.0 MAC ISO during spontaneous ventilation, Changes in pHa were a ttributable to changes in Pa-CO2. Conclusions-2.0 MAC ISO causes hypot ension and hypercapnia; however, cardiac index is maintained. Hypercap nia may be abolished with controlled ventilation, but at the expense o f reduced cardiac index. 1.3 MAC ISO results in minimal cardiopulmonar y depression, especially when healthy cats are allowed to breathe spon taneously, Clinical Relevance-Hypoventilation associated with untoward physiologic responses to 2.0 MAC may be overcome with controlled vent ilation, but results in marked reduction in cardiovascular performance ; thus, use of 2.0 MAC ISO should be avoided in cats.