Metabolic responses of resting man immersed in 25.5 degrees C and 33 degrees C water

This study was undertaken to determine the hormonal responses to disabling hypothermia as a result of cold water immersion. Thermally unprotected male divers trained by the U.S. Navy were subjected to total body immersion in water at 25.5 degrees C and 33 degrees C. Plasma epinephrine, norepinephrine, growth hormone, and cortisol were measured. Other variables monitored included oxygen consumption, carbon dioxide production, minute ventilation, and rectal temperature. Immersion without cold stress caused suppression of plasma epinephrine without affecting plasma norepinephrine. Cold stress combined with immersion caused a significant increase in plasma norepinephrine in the absence of other indicators of a generalized stress reaction. The degree of chilling seen in this study will produce disabling hypothermia within 1-2 h and may be shown initially only by an increase in plasma norepinephrine.