Inadequacy of current pediatric epinephrine autoinjector needle length for use in infants and toddlers.

Background: Epinephrine injection represents the standard of care for anaphylaxis treatment. It is most effective if delivered intramuscularly, whereas inadvertent intraosseous injection may be harmful. The needle length in current pediatric epinephrine autoinjectors (EAIs) is 12.7 mm; however, the ideal needle length for infants and toddlers weighing less than 15 kg is unknown.

Objective: To determine the skin-to-bone distance (STBD) and skin-to-muscle distance (STMD) at baseline and after simulated EAI application in infants and toddlers (weighing 7.5-15 kg).

Methods: Study participants recruited from 2 North American allergy clinics underwent baseline and compression (10-lb pressure) ultrasonography of the anterolateral thigh with a modified ultrasound transducer mimicking the footprint and maximum pressure application of an EAI device. Ultrasound images, with clinical data masked, were analyzed offline for STBD and STMD in short-axis approach.

Results: Of 53 infants (mean age, 18.9 months; 54.7% male; 81.1% white; mean weight, 11.0 kg), 51 had adequate images for short-axis STBD measurements. In these infants, the mean (SD) baseline STBD was 22.4 (3.8 mm), and the mean (SD) STMD was 7.9 (1.7) mm. With 10-lb compression, the mean (SD) STBD was 13.3 (2.1) mm, and the mean (SD) STMD was 6.3 (1.2) mm. An EAI with a needle length of 12.7 mm applying 10-lb pressure could strike the bone in 43.1% of infants and toddlers in this cohort.

Conclusion: Our data suggest that the optimal EAI needle length for infants and toddlers weighing 7.5 to 15 kg should be shorter than the needle length in currently available pediatric EAIs to avoid accidental intraosseous injections.