Total Body Oxygen Supply-Demand Balance in Burned Patients Under Enflurane Anesthesia

Abstract

The effects of enflurane anesthesia on the oxygen supply-demand balance have been studied in nine hypermetabolic-hyperdynamic burned patients undergoing debridement and skin-grafting procedures. Mean burn size was 55% of total body surface area. The patients were without cardiac, lung, hepatic, and kidney dysfunction and were not septic. Anesthesia was induced with sodium pentothal and maintained with enflurane and nitrous oxide in oxygen. Ventilation was controlled to maintain PaCO2 within normal limits. Crystalloid solutions and blood were administered to maintain adequate heart filling pressures. Serial measurements of cardiac output, arterial and mixed venous blood gases, and oxygen content were made before, during, and after anesthesia. Following induction of anesthesia and enflurane administration, cardiac output, oxygen delivery, and oxygen consumption decreased in a parallel fashion to approximately 60% of control. These variables did not change significantly throughout the procedure and returned to control values when enflurane was discontinued. Arteriovenous oxygen content difference did not increase and metabolic acidosis did not develop, suggesting that tissue perfusion remained adequate. Under anesthesia, oxygen consumption in burned patients was similar to that observed in normal subjects, indicating that enflurane blunts the hypermetabolic effects of thermal injury. It is concluded that in burned patients enflurane decreases metabolic rate and cardiac output, and maintains an adequate oxygen supply-demand balance.