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.