Water ingestion significantly reduced the incidence of presyncope during head-up tilt testing compared to no water (4.5% vs 36.4%, P=0.016) and increased tilt tolerance time.
RCT (n=22)
Crossover
Does prophylactic water ingestion improve orthostatic tolerance and prevent presyncope during head-up tilt-table testing in healthy adults?
Drinking 16 oz of water prior to upright posture significantly improves orthostatic tolerance and reduces the incidence of presyncope in healthy adults.
Absolute Event Rate: 4.5% vs 36.4%
p-value: p=0.016
BACKGROUND: Water ingestion raises blood pressure substantially in patients with perturbed autonomic control and more modestly in older subjects. It is unclear whether prophylactic water drinking improves orthostatic tolerance in normal healthy adults. METHODS AND RESULTS: Twenty-two healthy subjects, 18 to 42 years of age, with no history of syncope underwent head-up tilt-table testing at 60 degrees for 45 minutes or until presyncope or syncope occurred. In their initial test, participants were randomized to either 16 oz (473 mL) of water drinking 5 minutes before tilt-table testing or tilt-table testing alone, with the alternative in a second test on a different day. During the first 30 minutes of tilt, 8 of 22 subjects without water experienced presyncope but only 1 of 22 who had ingested water (P=0.016). Water drinking attenuated the heart rate increase associated with tilt (P<0.001) while accentuating the increase in total peripheral resistance (P=0.012). The average time study participants tolerated head-up tilt was 26% longer after water (41.1+/-8.1 versus 32.6+/-14.3 minutes, mean+/-SD), with a pairwise mean difference of 8.5+/-14.0 minutes (95% CI, 2.3 to 14.7 minutes; P=0.011). CONCLUSIONS: Water enhances tolerance of upright posture. The effect of water is mediated by increased peripheral vascular resistance. Water ingestion may constitute a simple and effective prophylaxis against vasovagal reactions in healthy subjects, such as those associated with blood donation.
Lu et al. (Tue,) conducted a rct in Healthy subjects with no history of syncope (n=22). Water ingestion vs. No water ingestion was evaluated on Presyncope during the first 30 minutes of tilt (p=0.016). Water ingestion significantly reduced the incidence of presyncope during head-up tilt testing compared to no water (4.5% vs 36.4%, P=0.016) and increased tilt tolerance time.