Effects of enflurane and isoflurane on splanchnic oxygenation in humans

Abstract

Study Objectives: To determine the effects of enflurane and isoflurane on hepatic venous oxygen saturation (ShvO 2) and splanchnic oxygen (O 2) extraction. To measure hemodynamic parameters and ShvO 2, mixed venous, and arterial lactate concentrations during enflurane and isoflurane anesthesia. Design: Randomized, prospective study. Setting: University hospital. Patients: 20 ASA physical status I, II, and III adults, who underwent major abdominal surgery requiring mechanical ventilation a few hours postoperatively. Interventions: After placement of catheters in the pulmonary artery, radial artery, peripheral and right hepatic vein, one hour postoperatively either enflurane or isoflumne was applied at different minimum alveolar concentration (MAC) of 0.5, 1.0, and 1.5 in a randomized order. Measurements and Main Results: Before and 10 minutes after administration of each desired end-expiratory anesthetic concentration, the following parameters were determined: hemodynamic parameters, arterial (SaO 2), mixed venous (SvO 2), and hepatic venous oxygen saturations, systemic and splanchnic O 2 extraction, arterial, mixed venous, and hepatic venous lactate concentrations. Cardiac output (CO) and mean arterial pressure (MAP) decreased in a dose dependent manner. SaO 2, SvO 2, and systemic O 2 extraction remained unchanged with enflurane and isoflurane anesthesia. In the enflurane group, but not in the isoflurane group, ShvO 2 decreased with increasing inhalational concentrations. This decrease in ShvO 2 reflected an increase in splanchnic O 2 extraction with enflurane; in contrast to isoflurane. Conclusions: Enflurane causes a decrease in ShvO 2, which indicates an impairment of splanchnic perfusion corresponding to the reduction in CO and MAP in a dose-dependent manner. Isoflurane maintains splanchnic perfusion in contrast to enflurane.