Increased Skin-to-Muscle Distances Affects the Dose of Adrenaline Administered Intramuscularly From EpiPen With Certain Cold Weather Clothing Combinations

IntroductionIn extreme cold weather (ECW) environments it may be beneficial to activate an auto-injector through clothing rather than against skin to minimize casualty exposure. It has been shown that popular adrenaline auto-injectors may not deliver an adequate intramuscular dose to individuals with increased subcutaneous fat, even when activated against skin. This experiment sought to build on research into auto-injector use in the ECW environment by assessing drug delivery through winter clothing combinations with varying simulated skin-to-muscle distances (STMD).MethodologyInvestigators based at the British Antarctic Survey Medical Unit (BASMU) in Plymouth, UK, tested two brands of auto-injector, EpiPen and Emerade, through commonly worn clothing sourced from the British Antarctic Survey. The experiment involved activating the auto-injector through clothing layers and different depths of silicone representing subcutaneous tissue. The volume administered through these layers was collected and its mass was measured. This mass was taken as a representation of the drug volume delivered through the various clothing layers, subcutaneous tissue, and muscle.ResultsThe EpiPen administered adrenaline through all clothing combinations tested at STMD 5 mm; however, thicker clothing combinations at STMD 10 mm prevented effective drug delivery. The Emerade auto-injectors delivered adrenaline at an acceptable dose through the thicker combinations at STMD of 10 mm and 15 mm.ConclusionsThese results suggest that adrenaline auto-injectors can successfully activate through polar clothing but that the depth of injection may be reduced. This may be more consequential in individuals with a greater STMD and should be considered when treating patients in cold environments.