181 GLUCOSE DRINK BUT NOT WATER INGESTION REDUCES ORTHOSTATIC TOLERANCE IN YOUNG AFRICAN MEN

Abstract

Background: Studies have demonstrated that ingestion of glucose lowers blood pressure in individuals with autonomic dysfunction. Whether glucose drink affects cardiovascular responses during orthostatic stress in young healthy individuals, particularly in Africans is not known. We therefore test the hypothesis that glucose drink will reduce orthostatic tolerance in normal young African men. Methods: In a randomized controlled cross-over design, eleven men (19.8 ± 0.4 kg/m2; 22.4 ± 0.8yr) ingested nothing, water (250 ml) and 30% glucose drink 10 min before standing on three separate days. We measured supine and standing systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR) and blood glucose levels. Orthostatic tolerance was evaluated as the time to presyncope during motionless standing. Results: During the first 60 min of standing, 81.8%, 90.9% and 18.2% of 11 subjects experienced presyncopal symptoms when ingested nothing, water and 30% glucose drink, respectively. Ingesting water did not affect orthostatic tolerance significantly while ingesting glucose drink significantly reduced orthostatic tolerance. Increased HR induced by standing was significantly enhanced, while the increase in SBP was attenuated when 30% glucose water was ingested. Conversely, increased DBP was not significantly affected by glucose drink. Ingestion of glucose drink led to a significant elevation in blood glucose level during orthostatic stress when compared to when nothing or water was ingested. Conclusion: This study indicates that glucose-enriched drink reduces orthostatic tolerance, and this is associated with enhanced tachycardia and attenuated SBP response. The findings imply that glucose-enriched fluid may not be advisable for persons susceptible to orthostatic intolerance.