A COMPARISON OF BAROREFLEX SENSITIVITY DURING ISOFLURANE AND DESFLURANE ANESTHESIA IN HUMANS

Background: Desflurane anesthesia has been associated with heart rate (HR) and sympathetic nerve activity (SNA) responses that differ from those during isoflurane anesthesia. Whether these differences might be due to better preservation by desflurane of the baroreceptor reflex control of HR or SNA in humans was examined. Methods: Baroreflex sensitivity was assessed in IS volunteers anesthetized with either desflurane or isoflurane, Measurements of HR, blood pressure (BP), and efferent SNA (percutaneous recordings from the peroneal nerve) were made, and baroreflex sensitivity was evaluated at conscious baseline and during 0.5, 1.0, and 1.5 MAC anesthesia. Baroreflex responses were triggered by bolus intravenous injections of nitroprusside (100 mu g) and phenylephrine (150 mu g). The linear portions of the baroreflex curves relating HR to mean arterial pressure and relating SNA to diastolic pressure were determined to obtain cardiac and sympathetic baroslopes, respectively. Results: Cardiac (HR) baroslopes were equally diminished at increasing MAC of both anesthetics, Sympathetic baroslopes were preserved at 0.5 MAC isoflurane but diminished at 0.5 MAC desflurane. Higher MAC produced equal depression of sympathetic baroslopes with both anesthetics. Conclusions: Increasing MAC of desflurane and isoflurane anesthesia results in similar and progressive decreases in BP but dissimilar SNA and HR responses. These differences are not explained by disparate effects of these anesthetics on the baroreceptor reflex control of SNA or HR.