Risk of Burns During Active External Rewarming for Accidental Hypothermia

Treatment of accidental hypothermia: Impact of insulation placement above or below an active external rewarming device on temperature and burn risk

INTRODUCTION

Prehospital treatment of accidental hypothermia typically involves using active external rewarming, usually either with chemical or electrical heating pads. Active external rewarming is a recommended treatment method, but carries the risk of burn injury, which can occur if tissue temperature exceeds 43 °C. Some device manufacturers discourage direct skin contact; however, there are no recommendations regarding type or amount of insulating material that should be placed between the patient and the device. We aimed to describe the impact of different insulating materials above and below various devices on the temperature at the contact area.

METHODS

Three different active external rewarming devices were suspended above a thermal imaging camera capable of recording the peak and average temperature of a surface area. Nine different scenarios with varying layers of insulation above and below the device, were tested over a 20-min period. The devices included an electric resistive heat pad, an oxygen-activated chemical heating blanket, and a sodium acetate chemical heat pack. Peak surface temperature was recorded every 30 s, and average surface temperature was calculated after each test.

RESULTS

Nine scenarios for three different devices were tested, resulting in 27 experiments. Development of peak surface temperature varied between devices. The electric device reached a highest average temperature of 42.9 °C and a peak temperature of 51.4 °C. The oxygen-reactive chemical heating device reached a highest average temperature of 27.2 °C, with a peak temperature of 57.5 °C. The sodium acetate chemical heat pack reached a highest average temperature of 50.4 °C and a peak temperature of 56.2 °C.

CONCLUSIONS

The devices demonstrated different temperature development characteristics depending on amount and relative placement of insulation, and all had the potential to exceed the threshold of potential thermal injury to the skin. Rescuers need to be aware of both the benefits and risks associated with the rewarming devices they use.

2024 American Heart Association and American Red Cross Guidelines for First Aid

Codeveloped by the American Heart Association and the American Red Cross, these guidelines represent the first comprehensive update of first aid treatment recommendations since 2010. Incorporating the results of structured evidence reviews from the International Liaison Committee on Resuscitation, these guidelines cover first aid treatment for critical and common medical, traumatic, environmental, and toxicological conditions. This update emphasizes the continuous evolution of evidence evaluation and the necessity of adapting educational strategies to local needs and diverse community demographics. Existing guidelines remain relevant unless specifically updated in this publication. Key topics that are new, are substantially revised, or have significant new literature include opioid overdose, bleeding control, open chest wounds, spinal motion restriction, hypothermia, frostbite, presyncope, anaphylaxis, snakebite, oxygen administration, and the use of pulse oximetry in first aid, with the inclusion of pediatric-specific guidance as warranted.

Performance of a Chemical Heat Blanket in Dry, Damp, and Wet Conditions Inside a Mountain Rescue Hypothermia Wrap

INTRODUCTION

Casualties with accidental hypothermia are evacuated using multilayer wraps, typically including a chemical heat blanket (CHB), a vapor barrier, and an insulating outer bag. We investigated CHB performance against dry, damp, and wet fabric, in a multilayer wrap, in response to a case report indicating diminished performance when wet.

METHODS

We wrapped a torso manikin in a base layer, CHB, vapor barrier, casualty bag, and vacuum mattress, recording CHB panel temperatures at intervals of up to 7 h. Experimental conditions were dry, damp, and wet clothing, with 2 blankets tested in each condition. We subsequently used a forward-looking infrared camera to assess whether the panels heated evenly and heat flux sensors to quantify heat transfer across 2 dry, 1 damp, and 1 wet fleece under CHB panels.

RESULTS

Chemical heat blankets maintained heat output for >7 h inside the wraps. Median (IQR) panel steady state temperatures were 52°C (39-56°C) against dry fleece, 41°C (36-45°C) against damp fleece, and 30°C (29-33°C) against wet fleece. Peak panel temperature was 67°C. The heat flux results indicated that CHBs generated similar quantities of heat in dry and damp conditions, as the lower temperatures were compensated by more efficient transfer of heat across the moist clothing layer. Chemical heat blanket heat output was diminished in wet conditions.

CONCLUSIONS

Rescuers should cut off saturated clothing in a protected environment before wrapping casualties, but damp clothing need not be removed. Because of the high peak temperatures recorded on the surfaces of CHBs, they should not be placed directly against skin, and compression straps should not be placed directly over CHBs.

Wilderness Medical Society Clinical Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2019 Update

To provide guidance to clinicians, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the out-of-hospital evaluation and treatment of victims of accidental hypothermia. The guidelines present the main diagnostic and therapeutic modalities and provide recommendations for the management of hypothermic patients. The panel graded the recommendations based on the quality of supporting evidence and a balance between benefits and risks/burdens according to the criteria published by the American College of Chest Physicians. The guidelines also provide suggested general approaches to the evaluation and treatment of accidental hypothermia that incorporate specific recommendations. This is the 2019 update of the Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2014 Update.