Comparison of METHODS Assessing Spontaneous Baroreflex Sensitivity during Sevoflurane Anesthesia: Sequence versus Transfer Function Analysis

Background: The arterial baroreflex is a key mechanism involved in blood pressure (BP) homeostasis and serves as a pressure buffer system against increase and decrease in BP. In contrast to awake patients, little has been known about correlations among methods assessing spontaneous baroreflex sensitivity (SBRS) during general anesthesia. The aim of present study was to compare SBRS obtained from sequence method and transfer function analysis (TFA), and examined their relationship to vagal cardiac function in patients during sevoflurane general anesthesia. Methods: 20 patients were anesthetized with 1 MAC sevoflurane with 50% and mechanically ventilated at 0.25 Hz. 5 min beat-to-beat BP and electrocardiogram were recorded to assess sequence BRS and TFA BRS from spontaneous RR interval and systolic BP fluctuation. We derived 4 proposed indices (Sequence BRS, low frequency (LF) BRS, high frequency (HF) BRS, and average BRS). Results: The indices were correlated with each other significantly and the Bland-Altman method demonstrated that sequence BRS was in close agreement with each other except LF BRS. The indices were also correlated highly with HF heart rate variability representing vagal cardiac function. Conclusions: SBRS was related to vagal cardic function. Because of the correlations and agreements between these two methods, it may employ them except for LF BRS during sevoflurane general anesthesia.