Effect of acute hyperglycemia on baroreflex sensitivity in healthy young adults.

Background: Autonomic dysfunction, impaired baroreflex sensitivity (BRS), and deranged circulatory homeostasis have been observed in chronic hyperglycemia and found to be associated with increased cardiovascular morbidity and mortality. However, the acute effects of hyperglycemia in healthy subjects have been rarely studied. The present study explores the effect of acute hyperglycemia on conventional and unconventional parameters of BRS in healthy young adults.

Methods: For the estimation of BRS beat-to-beat blood pressure (BP) and electrocardiogram were recorded in forty-two young, healthy subjects during fasting and at 1hr of the oral glucose load. Analysis of BRS was carried out by sequence and spectral method. Number of UP-, DOWN- and ALL-sequences between ramps of BP and RR-interval were calculated as an unconventional measure of BRS along with the other conventional parameters.

Results: We observed significant alteration of unconventional parameters of autonomic functions [the number of sequences of UP- (p = 0.0039) and ALL-sequences (p = 0.0233) of systolic BP and RR interval; and, UP- (p = 0.0380), DOWN- (p = 0.0417) and ALL-sequences (p = 0.0313) of mean BP and RR- interval] during acute hyperglycemia as compared to the fasting state. However, no significant changes were observed in any of the conventional parameters of BRS during acute hyperglycemia as compared to the fasting state.

Conclusions: Present study concludes that the unconventional parameters of BRS - the number of sequences between the ramp of BP and RR-interval - change significantly during acute hyperglycemia. However, the conventional parameters do not show significant changes during acute hyperglycemia. We may hypothesize that the relatively constant BRS is maintained at the expense of increased oscillations in the ramp of BP and RR-interval.