Hemodynamic Responses to Cold Water Ingestion During Head-Up Tilt

Purpose We examined whether drinking a small volume of cold water during orthostatic stress attenuates the fall in systolic blood pressure (SBP). Methods In a randomized crossover study, 19 healthy young adults underwent 15 min of 60 degree head-up tilt under three conditions on separate days: no water, 200 mL of body-temperature water (37 degrees Celsius), and 200 mL of cold water (4 degrees Celsius). Drinking began 5 min after tilting and lasted 1 min. Hemodynamics and tympanic temperature were analyzed using covariate-adjusted linear mixed models with within- and between-condition comparisons. Results During drinking, SBP increased from pre-drinking values by 9.54 mmHg (95% confidence interval [CI] 5.58 to 13.50) with body-temperature water and 14.70 mmHg (10.74 to 18.66) with cold water. After cold water ingestion, SBP remained higher by 5.95 mmHg (95% CI 1.99 to 9.91) over the first 4 min and 4.84 mmHg (0.88 to 8.80) over the subsequent 5 min. No clear post-drinking increases occurred with body-temperature water. SBP was higher with cold water than with both other conditions during the first 4 min after drinking, and higher than with body-temperature water during the subsequent 5 min. After cold water ingestion, stroke volume was higher and heart rate lower than before drinking, and tympanic temperature declined between the two post-drinking periods. Conclusion Drinking 200 mL of cold water after blood pressure had fallen attenuated the reduction in SBP during continued orthostatic stress in healthy young adults.