The effect of dexmedetomidine on arterial-cardiac baroreflex function assessed by spectral and transfer function analysis.

PURPOSE

The α(2)-adrenergic receptor agonist dexmedetomidine reportedly weakens heart rate (HR) responses to 'rapid' (during a few seconds) reduction in arterial pressure, but does not affect HR responses to 'gradual' (during 60 s) reduction in arterial pressure. As the speed of neurotransmission along the parasympathetic nerve is relatively rapid, alteration of parasympathetic-mediated arterial-cardiac baroreflex function plays a more important role in HR responses to 'rapid' changes in arterial pressure. We therefore hypothesized that dexmedetomidine attenuates parasympathetic-mediated arterial-cardiac baroreflex function.

METHODS

Twelve healthy men received placebo, low-dose (loading, 3 μg/kg/h for 10 min; maintenance, 0.2 μg/kg/h for 60 min) (low-DEX), or moderate-dose (loading, 6 μg/kg/h for 10 min; maintenance, 0.4 μg/kg/h for 60 min) (moderate-DEX) dexmedetomidine infusions in a randomized, double-blind, crossover study. Before and after 70 min of infusion, arterial-cardiac baroreflex function was assessed by spectral and transfer function analysis between arterial pressure variability and HR variability.

RESULTS

The high-frequency power of systolic arterial pressure (SAP) variability increased significantly with low-DEX and moderate-DEX infusions (significant interaction effects, P = 0.005), whereas the high-frequency power of R-wave-R-wave interval (RRI) variability (as an index of cardiac parasympathetic activity) did not change significantly at any dose infusions. Then, transfer function gain in the high-frequency range (as an index of parasympathetic arterial-cardiac baroreflex) decreased significantly with low-DEX and moderate-DEX infusions (significant interaction effects, P = 0.007).

CONCLUSIONS

The present results suggest that dexmedetomidine attenuates parasympathetic-mediated arterial-cardiac baroreflex function, implying weakened HR response to 'rapid' reduction in arterial pressure.