Microcirculatory response to halothane and isoflurane anesthesia.

Abstract

Microcirculatory hemodynamics are often used to monitor tissue and organ survival. This study investigated the effect of halothane and isoflurane anesthesia on peripheral microcirculation using the cremaster muscle during intravital microscopy. Twenty-three Sprague-Dawley rats were studied in four groups. Two groups served as controls and did not undergo flap isolation but did receive halothane (N = 6) or isoflurane (N = 5). After induction with a single dose of intraperitoneal pentobarbital (40 mg per kilogram), rats were ventilated with either 2 minimum alveolar concentration (MAC) halothane or 2 MAC isoflurane. Esophageal temperature, electrocardiography, central venous pressure, mean arterial pressure, and blood gases were measured over 4 hours. In groups receiving surgery with either halothane (N = 6) or isoflurane (N = 6), the cremaster muscle was isolated on the neurovascular pedicle. Microcirculatory responses to both halothane and isoflurane anesthesia were evaluated by measuring red blood cell (RBC) velocity, vascular diameters in arterioles (A1, A2-1, A2-2, and A3) and the main venule (V1), functional capillary perfusion, and leukocytic endothelial interactions in postcapillary venules (rolling, adherent, and transmigrating leukocytes). Hemodynamic variables were compared among all four groups, and microcirculatory variables were compared between the two surgical groups. During isoflurane anesthesia in animals with flaps, significantly higher (p < 0.05) RBC velocities were recorded in arterioles A1 (24.4%), A2-2 (28.2%), and A3 (17.4%). Capillary perfusion was significantly higher in animals with flaps and halothane anesthesia (17.8%; p < 0.05). The number of rolling leukocytes (39.4%) was significantly higher during isoflurane anesthesia in animals with flaps (p < 0.05). Better flow hemodynamics in the peripheral microcirculation were seen during halothane anesthesia, and were confirmed by greater functional capillary perfusion and fewer activated leukocytes. In the isoflurane group, RBC velocity alone cannot serve as an indicator of microcirculatory function.