ETHANOL INGESTION PROLONGS ORTHOSTATIC INTOLERANCE IN HYPERTHERMIC HUMANS

Background: Both ethanol ingestion and hyperthermia contribute to orth ostatic intolerance (OI). Hypothesis: Since ethanol has been cited as a major risk factor for hyperthermia-related deaths, we hypothesized t hat ethanol exacerbates OI induced by hyperthermia. Methods: There wer e seven subjects (four males, three females) rendered hyperthermic (es ophageal temperature = 39 degrees C) in a 40 degrees C water bath on t wo separate days: Condition 1) Control (juice ingestion); and Conditio n 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 degrees head-up tilts prior to and following immersion. BPs, heart rate and e sophageal temperatures were monitored throughout the experiments. Resu lts: For first and second post-immersion tilts, mean arterial BP (MAP) during tilting increased by 5.9 +/- 3.6 (SE) and 9.8 +/- 2.6 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 Lilts. In the control condition, only one subject experienced orthostatic intoleranc e following the first post-heating tilt and no intolerance was experie nced following 30 min post-healing. However, during the ethanol condit ion, 4 subjects experienced orthostatic intolerance following the firs t till with episodes of intolerance lasting as long as 80 min (8 supin e/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 de aths.