Ethanol ingestion prolongs orthostatic intolerance in hyperthermic humans
White MD, Johnston CE, Wu M-P, Bristow GK, Giesbrecht GGAviat Space Environ Med 1998; 69:577-82
Abstract
Background: Both ethanol ingestion and hyperthermia contribute to orthostatic intolerance (OI). Hypothesis: Since ethanol has been cited as a major risk factor for hyperthermia-related deaths, we hypothesized that ethanol exacerbates OI induced by hyperthermia. Methods: There were seven subjects (four males, three females) rendered hyperthermic (esophageal temperature = 39°C) in a 40°C water bath on two separate days: Condition 1) Control (juice ingestion); and Condition 2) Ethanol [ethanol (1 ml · kg-1 body mass) and juice ingestion]. To test for OI, 5-min supine periods were followed by 5-min 63° head-up tilts prior to and following immersion. BPs, heart rate and esophageal temperatures were monitored throughout the experiments. Results: For first and second post-immersion tilts, mean arterial BP (MAP) during tilting increased by 5.9 ± 3.6 (SE) and 9.8 ± 4.3 mm Hg in the control condition, while it decreased by 7.9 ± 5.8 and 0.6 ± 4.3 mm Hg in the ethanol condition. This gave significantly lower MAP (ethanol vs. control) of 63.6 ± 3.1 vs. 71.8 ± 4.5 mm Hg (p < 0.05) for the first and 79.6 ± 2.3 vs. 86.7 ± 4.4 mm Hg (p < 0.05) for the second post-immersion tilts. These values were all significantly less (p < 0.05) than normothermic tilted values of 94.7 ± 4.7 mm Hg in the ethanol and 93.6 ± 2.9 mm Hg in the control condition. Prior to warm water immersion, subjects tolerated all head-up tilts. In the control condition, only one subject experienced orthostatic intolerance following the first post-heating tilt and no intolerance was experienced following 30-min post-heating. However, during the ethanol condition, 4 subjects experienced orthostatic intolerance following the first tilt with episodes of intolerance lasting as long as 80 min (8 supine/tilt cycles). Conclusion: Ethanol ingestion prolonged and increased the magnitude of OI in hyperthermic subjects. This may at least partly explain why ethanol is a major risk factor in hyperthermia-related deaths.
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Table of Contents for Volume 69, Number 6 of the ASEM journal.