HEMODYNAMIC AND ORGAN BLOOD-FLOW RESPONSES TO HALOTHANE AND SEVOFLURANE ANESTHESIA DURING SPONTANEOUS VENTILATION

This study compared systemic hemodynamic and organ blood flow response s to equipotent concentrations of halothane and sevoflurane during spo ntaneous ventilation in the rat. The MAC values for halothane and sevo flurane were determined. Cardiac output and organ blood flows were mea sured using radiolabeled microspheres. Measurements were obtained in a wake rats (control values) and at 1.0 MAC halothane or sevoflurane. Th e MAC values (mean +/- SEM) for halothane and sevoflurane were 1.10% /- 0.05% and 2.40% +/- 0.05%, respectively. The PaCO2 increased to a s imilar extent in both groups compared with control values. During halo thane anesthesia, heart rate decreased by 12% (P < 0.01), cardiac inde x by 26% (P < 0.01), and mean arterial blood pressure by 18% (P < 0.01 ) compared with control values. Stroke volume index and systemic vascu lar resistance did not change. During sevoflurane anesthesia, hemodyna mic variables remained unchanged compared with control values. Coronar y blood flow decreased by 21% (P < 0.01) and renal blood flow by 18% ( P < 0.01) at 1.0 MAC halothane, whereas both remained unchanged at 1.0 MAC sevoflurane. Cerebral blood flow increased to a greater extent wi th halothane (63%; P < 0.01) than with sevoflurane (35%; P < 0.05). Du ring halothane anesthesia, hepatic arterial blood flow increased by 48 % (P < 0.01), whereas portal tributary blood flow decreased by 28% (P < 0.01). During sevoflurane anesthesia, hepatic arterial blood flow in creased by 70% (P < 0.01) without a concomitant reduction in portal tr ibutary blood flow. Total liver blood flow decreased only with halotha ne (16%; P < 0.05). In conclusion, for comparable increases in PaCO2, systemic hemodynamic and organ blood flow responses to halothane are s ignificantly greater than the responses to sevoflurane at an equipoten t concentration of 1.0 MAC in the spontaneously ventilating rat.