Frequencies and predictors of subcutaneous and intraosseous injection with 4 epinephrine autoinjector devices

Abstract

BackgroundTo prevent anaphylaxis-associated illness, intramuscular epinephrine injection is recommended. Subcutaneous injection may reduce efficacy, and intraosseous injection promotes morbidity. A few studies suggested that commercially available thigh epinephrine autoinjectors (EAIs) may induce subcutaneous/intraosseous injection in some adults. ObjectiveTo estimate the subcutaneous/intraosseous-injection rates of 4 EAIs by comparing their needle lengths with the ultrasound-measured skin-to-muscle depth and skin-to-bone depth of the midthigh of adults with allergic diseases in a cross-sectional study and to determine patient factors that predict subcutaneous EAI injection. MethodsThigh ultrasound was conducted in a convenience-recruited cohort with minimal and maximal compression to estimate the effect of EAI-induced compression. Subcutaneous/intraosseous-injection rates were estimated for Anapen, EpiPen, Jext, and Emerade. Multivariate analyses for subcutaneous-injection risk were conducted with age, sex, abdominal and thigh circumferences, and upper-arm skinfold thickness. ResultsA total of 68 patients were recruited. Compression thinned the subcutaneous tissue and muscle by 1 and 9 mm, respectively, on average. Projected subcutaneous-injection rates with/without compression were high for Anapen (65%-66%), moderate for EpiPen and Jext (29%-38%), and lowest for Emerade (13%-21%). Compression introduced a small intraosseous-injection risk with Emerade (4%). Female sex predicted subcutaneous injection (odds ratio, 1.3-2.0; all P < .001). Depending on the EAI, 29% to 97% of women and 0% to 41% of men would be injected subcutaneously. Older men were at risk of intraosseous Emerade injection. Obesity-related variables predicted subcutaneous injection poorly. ConclusionAnapen was associated with high subcutaneous-injection rates. EpiPen and Jext were projected to provide intramuscular injection in all men without risk of intraosseous injection. Emerade yielded the lowest subcutaneous-injection rates in women. Compression largely affected the muscle. Trial RegistrationClinicalTrials.gov Identifier: NCT02886468