Increased Skin-to-Muscle Distances Affects the Dose of Adrenaline Administered Intramuscularly From EpiPen With...

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.