Hemodynamic changes and oxygen consumption in burned patients during enflurane or isoflurane anesthesia

The effects of enflurane or isoflurane anesthesia on the systemic circulation and whole-body oxygen (O2) uptake (VO2) of 15 burn patients undergoing wound excision and skin grafting procedures were studied. The possibility that burn wound excision might adversely affect pulmonary circulation was also investigated. The patients were preanesthetically in a hyperdynamic-hypermetabolic state, characterized by a resting cardiac index (CI) of 6.2 +/- 0.9 L.min-1.m-2 (mean +/- SD), a VO2 (calculated using the Fick principle) of 213 +/- 44 mL.min-1.m-2, a normal mean systemic arterial pressure (MAP) (92 +/- 15 mm Hg), and markedly decreased systemic vascular resistance (SVR) (570 +/- 162 dynes.sec.cm-5). Mean pulmonary arterial pressure (MPAP) preanesthetically was slightly increased (21 +/- 3 mm Hg), while pulmonary vascular resistance (PVR) was in the low-normal range (59 +/- 16 dynes.sec.cm-5). No difference among the effects of enflurane and isoflurane on systemic and pulmonary hemodynamics and metabolic rate was detected. Induction of anesthesia was associated with a decrease in VO2, CI, MAP, and MPAP (P less than 0.001), while SVR and PVR did not change. The decrease in CI paralleled the decrease in VO2, thereby maintaining whole-body O2 supply-demand balance. VO2 decreased most likely because of lessened tissue O2 requirements. When anesthesia was discontinued, all metabolic and hemodynamic variables promptly returned to preanesthetic values. No effect of burn wound excision on pulmonary circulation was detected.