Immersion hypothermia: comparative protection of anti-exposure garments in calm versus rough seas.

To evaluate the thermal performance of anti-exposure garments in rough seas, eight garment-ensembles were studied: 7 foam-insulated garments (2 tight-fitting "wet" suits, 3 loose-fitting "wet" garments, 2 "dry" suits) and 1 uninsulated, loose-fitting control. Mean calm and rough water temperatures were 10.7 and 11.1 degrees C, respectively. Rectal temperature, back skin temperature, heart rate, and subjective evaluations of garment protection were measured. Loose-fitting, "wet" garments allowed significantly greater (approximately 50-100%) mean rectal temperature cooling rates and significantly larger declines in skin temperature in rough water than in calm water. Such differences were not found for either the tight-fitting "wet" suits or the "dry" suits. Heart rates were significantly higher in rough seas than in calm seas for all garments. Rectal and skin temperature changes were positively correlated with each other and with subjective evaluation of cold water flushing; they were negatively correlated with warmth and tightness-of-fit. "Dry" garments provided better protection than did "wet" garments in both sea conditions, and tight-fitting "wet" garments provided better protection than did loose-fitting "wet" garments in rough but not in calm seas. Accidental immersion in rough seas may be associated with significantly lower survival times than previously estimated from calm-water studies.

Cardiopulmonary resuscitation and hypothermia.

Current basic life support (BLS) protocols do not address the physiologic effects of accidental hypothermia in prehospital care. The extreme levels of bradycardia, bradypnea, and peripheral vasoconstriction that often accompany profound hypothermia may complicate the accurate diagnosis of cardiopulmonary arrest in the unmonitored patient. Although CPR is indicated in the truly pulseless, apneic victim of hypothermia, chest compressions may convert nonpalpable but adequately perfusing sinus bradycardia to ventricular fibrillation. This dilemma had led to disagreement among clinicians and researchers in hypothermia about prehospital care protocols for the severely hypothermic patient. This article reviews the controversy and recommends the application of a normal BLS protocol to hypothermic patients presenting in apparent cardiopulmonary arrest.

Accidental hypothermia: an experimental study of practical rewarming methods.

Five rewarming techniques, appropriate for first-aid use in the nonhospital setting, were applied to each of nine subjects whose body temperatures had been lowered to 35 degrees C in a stirred tank of 7.5 degrees C water. The rewarming techniques were: a) inhalation of heated, water-saturated oxygen; b) placement of heating pads over areas of high heat transfer; c) combination of methods a) and b); d) hot whirlpool bath; and e) shivering. Inhalation of heated, water-saturated oxygen was significantly better than the shivering control in minimizing temperature "afterdrop" and is, therefore, preferred over the other techniques as it avoids the physiological hazards of the peripheral vasodilation from external rewarming.

Accidental hypothermia: an experimental study of inhalation rewarming.

Inhalation rewarming of hypothermic humans with heated, humidified oxygen was compared to rewarming by immersion in a hot bath. In 10 subjects cooled to approximately 35 degrees C core temperature, there was no significant difference in the amount of temperature "afterdrop" with the two rewarming procedures. Inhalation rewarming provided rapid commencement of increase in tympanic and esophageal temperatures, indicating effective rewarming of critical core regions, especially heart and brain. This method of core rewarming avoids the physiological hazards associated with the peripheral vasodilation which accompanies external rewarming. Moverover the simplicity of application of this method suggests its greater use in both first-aid and hospital treatment of accidental hypothermia.

Epinephrine metabolism in mammalian brain after intravenous and intraventricular administration.

Epinephrine given intravenously or intraventricularly has a half-life in the brain of the rat of 2 to 2.5 hours. After intravenous administration of the drug the principal route of metabolism is O-methylation, whereas after intraventricular administration the principal route is conjugation.