Which rewarming therapy in hypothermia? A review of the randomised trials

Evaluation of Three Field Rewarming Techniques During Cold Weather Military Training

INTRODUCTION

The purpose of this work was to evaluate the effectiveness of 3 rewarming techniques to determine how warfighters, and perhaps other populations in wilderness environments, should prioritize field rewarming options after a brief accidental immersion in cold water.

METHODS

As part of a cold weather military training exercise, 31 military personnel (mean±SD age: 26±5 y, height: 180±10 cm, weight: 83.2±10.9 kg) completed a 10-min immersion in cold (0°C) water and subsequently rewarmed for 60 min using 3 different field rewarming techniques (sleeping bag, sleeping bag + warm fluids, or exercise). Heart rate, core and skin temperatures, thermal and shivering sensations, and manual dexterity (intravenous setup and insertion) were measured during the training exercise.

RESULTS

Cold water immersion decreased core temperature (pre: 37.4±0.4; post: 36.4±1.0°C; P<0.001) and mean skin temperature (pre: 27.9±1.3; post: 15.6±1.8°C; P<0.001) and impaired manual dexterity (intravenous insertion time, pre: 71±12, post: 166±48 s; P<0.001). Recovery from mild cold stress was similar among all 3 rewarming techniques for all measurements.

CONCLUSIONS

Findings suggesting similar rewarming responses in field settings are beneficial for the warfighter, and perhaps others, in that rewarming options exist and can be implemented with no compromise in recovery from cold stress.

Tympanic thermometry is unsuitable as a screening tool for hypothermia after open water swimming

OBJECTIVE

Mass participation in competitive open water swimming is becoming increasingly popular. The purpose of this study was to determine whether infrared emission detection (IRED) tympanic temperature measurement taken in participants approximately 1 minute following a long-distance open water swimming event is a suitable screening tool for hypothermia.

METHODS

We studied 15 males and 7 females who completed the 20-km Rottnest Channel Swim off the coast of Perth, Western Australia. Following the swim, each athlete was clinically assessed for hypothermia through the observation of gait, cognitive processing, and demeanor. Approximately 1 minute following the swim, participants underwent temperature measurement using one of two IVAC Core Check 2090 IRED tympanic thermometers set to core equivalent mode. Further tympanic readings and an oral temperature reading were taken at 5 minutes post swim in subjects triaged to the medical tent after the initial clinical screen.

RESULTS

At 1 minute post event, the average tympanic temperature measurement was 28.9 degrees C (95% CI, 28.3-29.7), while at 5 minutes postevent it was 31.6 degrees C (95% CI, 31.1-32.2). The average oral temperature at 5 minutes post event was 34.3 degrees C (95% CI, 33.7-34.7). The difference between the screening tympanic and oral temperatures was statistically significant (P = 0.000).

CONCLUSIONS

Infrared emission detection tympanic thermometry is unsuitable as a screening tool for hypothermia following a prolonged open water swim because it substantially overestimates the incidence and severity of hypothermia in participants.

Prehospital treatment of hypothermia

This article considers several issues regarding cold stress, development of hypothermia, and prehospital care of the hypothermic patient. Advice is given on the use of clinical impressions and functional characteristics to determine the level of hypothermia. Response to cold water immersion is characterized as short-term (cold shock response), midterm (loss of performance), and long-term (development of hypothermia). Circum-rescue collapse is the dramatic worsening condition of the patient just before, during, or after rescue from cold stress. After rescue, the treatment priorities are to arrest the fall in core temperature, establish a steady, safe rewarming rate while maintaining the stability of the cardiorespiratory system, and provide sufficient physiological support.

Emergency treatment of hypothermia

This review considers several recent concepts regarding aetiology and treatment of accidental hypothermia. The importance and effectiveness of shivering heat production in the attenuation and reversal of hypothermia is described. Immediately following removal from cold stress, the patient is in danger of a deteriorating condition that may be due to collapse of arterial pressure and/or continued decrease of core temperature. Several controversies are discussed. It is advised that, when possible, patients should be actively but gently warmed as soon as possible (especially if arrival at the emergency department will take greater than 45 min). Extra time should be taken to check for life signs before cardiopulmonary resuscitation is initiated. Chest compressions should proceed at regular normothermic rates and care should be taken to not overventilate the patient. In the emergency department, several factors should be considered before deciding on a treatment regimen. These factors include level of consciousness, cardiovascular stability, core temperature and the direction of change of core temperature. It may be advantageous to transport the more severely hypothermic patient to a more advanced care facility even though transport time may be greater.