[Sympatho-adrenal activity in acute cold stress. The mechanism of sudden death following water immersion].

In addition to currently known mechanisms of sudden death following water immersion, predominantly vagal cardio-depressive reflexes are discussed. The pronounced circulatory centralization in diving animals as well as following exposure to cold water indicates additional sympathetic activity. In cold water baths of 15 degrees C, our own measurements indicate an increase in plasma catecholamine levels by more than 300%. This may lead to cardiac arrhythmias by the following mechanism: Cold water essentially induces sinus bradycardia. Brady- and tachyarrhythmias may supervene as secondary complications. Sinusbradycardia may be enhanced by sympathetic hypertonus. Furthermore, ectopic dysrhythmias are liable to be induced by the strictly sympathetic innervation of the ventricle. Myocardial ischemia following a rise in peripheral blood pressure constitutes another arrhythmogenic factor. Some of these reactions are enhanced by alcohol intoxication.