BACKGROUND: It is reported that ketamine increases central sympathetic activity as well as catecholamine reuptake inhibition. However, little has been known about baroreflex control of heart rate in ketamine anesthetized humans. Thus, the aim of this study was to analyze the effect of ketamine on spontaneous baroreflex sensitivity (BRS) during ketamine induction of anesthesia.

METHODS: Beat-by-beat arterial blood pressure and electrocardiogram at 5 min before and 10 min after ketamine administration (2 mg/kg) were recorded in twenty healthy living liver transplant donors. Spontaneous BRS was assessed by sequence method and transfer function analysis method.

RESULTS: Spontaneous BRS assessed by sequence method, BRSsequence, decreased from 13.7 ± 6.3 to 7.8 ± 4.5 ms/mmHg (P < 0.001). Spontaneous BRS assessed by low frequency transfer function method decreased from 10.9 ± 5.4 to 7.0 ± 4.1 ms/mmHg and by high frequency transfer function method from 14.8 ± 9.2 to 8.7 ± 8.8 ms/mmHg, respectively (P < 0.05).

CONCLUSIONS: The spontaneous BRS was decreased during ketamine induction of general anesthesia. These results suggest that anesthesia induction with ketamine impairs baroreflex control of heart rate, which may provoke hemodynamic instability.