MOTION SICKNESS INDUCED PREDISPOSITION TO HYPOTHERMIA IS EFFECTED BY ANTI-MOTION SICKNESS DRUGS

• Published in: Aviation, space, and environmental medicine space, and environmental medicine, 2008-03, Vol.79 (3), p.210-211
• Main Authors: Nobel, G, Eiken, O, Tribukait, A, Kolegard, R, Mekjavic, I B
• Format: Article
• Language: English
• ISSN: 0095-6562

Introduction: Previous studies have shown that motion sickness (MS) potentiates the cooling rate of the body core during immersion, both in luke-warm (28 deg C) -, and cold water (15 deg C). The aim of the present study was to investigate whether this MS-induced predisposition to hypothermia would be affected by administering two anti-MS drugs; the histamine-receptor blocker dimenhydrinate and the muscarine-receptor blocker scopolamine. Methods: The study was approved by the Human Ethics Committee at the Karolinska Institute. Nine healthy male subjects participated in 5 experimental conditions. After baseline recording and administration of either of the two drugs, or their respective placebo substances, each subject was immersed in 15 deg C water for a maximum of 90 minutes. The experimental conditions were: 1. Control: no MS provocation, no medication. 2. Control MS: MS provocation, no medication. 3. Placebo MS: placebo dimenhydrinate and placebo scopolamine, MS provocation. 4. Dim MS: dimenhydrinate and placebo scopolamine, MS provocation. 5. Scop MS: scopolamine and placebo dimenhydrinate, MS provocation. MS provocation was induced by the use of a rotating chair. Throughout the experiments rectal temperature, mean skin temperature, the difference in temperature between forearm and the 3rd finger of the right hand, oxygen uptake, heart rate and blood pressure were recorded. Results: Dimenhydrinate and Scopolamine were similarly efficacious in ameliorating nausea. During immersion the core temperature cooling rate (A rectal temperature) was 28 % greater in the Control MS trial than in the Control trial (p < 0.05). The MS-induced predisposition to hypothermia was prevented by dimenhydrinate (p < 0.01), but not by Scopolamine, nor by the placebo substances. Discussion: This different effect might suggest that the MS-induced predisposition to hypothermia is mediated via histaminergic rather than cholinergic mechanisms. Furthermore, although the two drugs had different effects on the core temperature cooling rate they were equally efficacious in ameliorating nausea.