Sevoflurane anesthesia maintains reflex tachycardia on position change from supine recumbent to head-up tilt.

This study evaluated the effects of inhalational anesthetics on hemodynamic changes in response to head-up tilt in humans. Twenty-four patients were randomly divided into three groups that received either halothane, isoflurane, or sevoflurane. Changes in heart rate, blood pressure, and plasma norepinephrine concentrations were determined before and during head-up tilt position in the awake and anesthetized state. Head-up tilt caused a significant increase in the heart rate, concomitantly with a decrease or no significant changes in systolic blood pressure in the awake state. However, under 2 minimum alveolar concentrations (MAC) of halothane and isoflurane anesthesia, the heart rate did not significantly change during head-up tilt in spite of significant decreases in systolic blood pressure. In contrast, under 2 MAC of sevoflurane anesthesia, the heart rate significantly increased during head-up tilt. Plasma norepinephrine did not significantly alter during head-up tilt in the awake as well as the anesthetized state. These results suggest that sevoflurane maintains an increase in heart rate in response to head-up tilt, whereas halothane and isoflurane attenuate the response.