Systemic and Cerebral Effects of Isoflurane-induced Hypotension in Dogs

The systemic and cerebral effects of hypotension induced with isoflurane were examined in 12 dogs. Hypotension to a mean arterial pressure of either 50 mmHg or 40 mmHg for 1 h was produced by 2.5 +/- 0.1-2.9 +/- 0.3% end-expired isoflurane anesthesia. Before and during the period of hypotension the following were measured or derived: arterial and pulmonary artery pressures; arterial, mixed venous, and sagittal sinus blood gases; cardiac output and cerebral blood flow; whole body and cerebral oxygen consumption; systemic and cerebral vascular resistance; intracranial pressure, serum lactate, and pyruvate concentrations; and blood glucose. At the end of the period of hypotension, brain biopsy specimens were taken for the determination of ATP, ADP, AMP, phosphocreatine, lactate, and pyruvate concentrations. Isoflurane-induced hypotension produced a significant decrease in systemic vascular resistance (27-43%) associated with a significant decrease in cardiac output (39-42%) and a smaller decrease in whole-body oxygen consumption (14-21%). Isoflurane also produced a significant decrease in cerebral oxygen consumption (40-44%) accompanied by a decrease in cerebral blood flow (60-62%). Following both the 40 and 50 mmHg periods of hypotension, the cerebral energy state was normal, indicating the preservation of normal aerobic metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)