Identification of cause of sudden death during hot waterbathing

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Fourteen thousands Japanese victims die during their bathing annually. It is an exceptionally high incidence limited to Japan, considering the world statistics of sudden death. In order to study the actual cause of the sudden death, 1) pre-hospital situations of those accidents in bath on the scene were studied by questionnaire to captains of emergency personnel of the Tokyo fire department and 2) hot bath bathing (40 and 44 degree C) was challenged in Japanese healthy young male subjects (age 20-23) while hemodynamics (body temperature, HR, BP, heart rate variability), hematological and endocrinological biochemical markers (CBC, adhesion molecules, endothelial functions, cathecolamines, h-ANP, endothelin-1, beta endorphine) and also neuropsychological function test (Paced Auditory Serial Addition Test: PASAT). In the first study, 1775 accidents during bathing were analyzed. Among them, cardiopulmonary arrest at the scene was 46% (CPA victims), while 16% of victims were those who could not get out of hot water-filled tub (rescued victims). The recued victims were candidates of CPA if they were not found and rescued from tub. Most of rescued victims had various grade of consiousness disturbances while involvement of alcohol, hyotension and cardiac symptoms such as chest pain were rarely associated. In the second study, body temperature rose up to 40.1 degree C (44 degree water) and 38.1 degree C (40 degree C water). Associated with the high body temperature, HR increased, heart rate variability decreased, BP slightly decreased or increased, orthostatic hypotensin was induced. PASAT indicated significant decrease in the rate of correct answer following the 44 degree C hot water immersion associated with the significant increase of plasma beta-endorphin, while not following the 40 degree C hot water immersion. Other hematological and endocrinological biochemical markers were compatible with the response to stress by hot water immersion. It was concluded that