Renal blood flow: differences in autoregulation during anesthesia with halothane, methoxyflurane, or alphaprodine in the dog.

Abstract

The hypothesis that general anesthesia impairs the ability of the kidney to regulate its blood flow was examined in 15 dogs during anesthesia with halothane, halothane and N2O, methoxyflurane, alphaprodine, or alphaprodine and N2O. Anesthesia was induced with halothane in 5 experiments and with thiopental in all the remainder. Blood pressure was altered by dextran infusion and by controlled hemorrhage, and changes in renal blood flow were monitored by using chronically implanted Doppler ultrasonic flow probes. Our results show that autoregulation of renal blood flow was maintained during halothane anesthesia, despite a significant decrease in arterial pressure (p = 0.0005); only when the normal lower autoregulatory limit of pressure was reached did renal blood flow decrease. During anesthesia with methoxyflurane or alphaprodine, renal blood flows were reduced during controlled hemorrhage before the normal lower autoregulatory limit of pressure was reached. Autoregulation was, therefore, impaired by these agents. Induction of anesthesia with thiopental did not alter the response of renal blood flow to dextran or hemorrhage during halothane administration. Nitrous oxide did not significantly alter renal blood flow responses during halothane, alphaprodine, or methoxyflurane anesthesia.