Comparison of Distal Limb Warming With Fluidotherapy and Warm Water Immersion for Mild Hypothermia Rewarming.

OBJECTIVE: The purpose of the study was to determine the effectiveness of Fluidotherapy rewarming through the distal extremities for mildly hypothermic, vigorously shivering subjects. Fluidotherapy is a dry heat modality in which cellulose particles are suspended by warm air circulation. METHODS: Seven subjects (2 female) were cooled on 3 occasions in 8˚C water for 60 minutes, or to a core temperature of 35°C. They were then dried and rewarmed in a seated position by 1) shivering only; 2) Fluidotherapy applied to the distal extremities (46 ± 1°C, mean ± SD); or 3) water immersion of the distal extremities (44 ± 1°C). The order of rewarming followed a balanced design. Esophageal temperature, skin temperature, heart rate, oxygen consumption, and heat flux were measured. RESULTS: The warm water produced the highest rewarming rate, 6.1°C·h(-1), 95% CI: 5.3-6.9, compared with Fluidotherapy, 2.2°C·h(-1), 95% CI: 1.4-3.0, and shivering only, 2.0°C·h(-1), 95% CI: 1.2-2.8. The Fluidotherapy and warm water conditions increased skin temperature and inhibited shivering heat production, thus reducing metabolic heat production (166 ± 42 W and 181 ± 45 W, respectively), compared with shivering only (322 ± 142 W). Warm water provided a significantly higher net heat gain (398.0 ± 52 W) than shivering only (288.4 ± 115 W). CONCLUSIONS: Fluidotherapy was not as effective as warm water for rewarming mildly hypothermic subjects. Although Fluidotherapy is more portable and technically simpler, it provides a lower rate of rewarming that is similar to shivering only. It does help decrease shivering heat production, lowering energy expenditure and cardiac work, and could be considered in a hospital setting, if convenient.

Comparison of heat donation through the head or torso on mild hypothermia rewarming.

OBJECTIVE: The purpose of the study was to compare the effectiveness of head vs torso warming in rewarming mildly hypothermic, vigorously shivering subjects using a similar source of heat donation. METHODS: Six subjects (1 female) were cooled on 3 occasions in 8 ºC water for 60 minutes or to a core temperature of 35 ºC. They were then dried, insulated, and rewarmed by 1) shivering only; 2) charcoal heater applied to the head; or 3) charcoal heater applied to the torso. The order of rewarming methods followed a balanced design. Esophageal temperature, skin temperature, heart rate, oxygen consumption, and heat flux were measured. RESULTS: There were no significant differences in rewarming rate among the 3 conditions. Torso warming increased skin temperature and inhibited shivering heat production, thus providing similar net heat gain (268 ± 66 W) as did shivering only (355 ± 105 W). Head warming did not inhibit average shivering heat production (290 ± 72 W); it thus provided a greater net heat gain during 35 to 60 minutes of rewarming than did shivering only. CONCLUSIONS: Head warming is as effective as torso warming for rewarming mildly hypothermic victims. Head warming may be the preferred method of rewarming in the field management of hypothermic patients if: 1) extreme conditions in which removal of the insulation and exposure of the torso to the cold is contraindicated; 2) excessive movement is contraindicated (eg, potential spinal injury or severe hypothermia that has a risk of ventricular fibrillation); or 3) if emergency personnel are working on the torso.