SAN ANTONIO – Overweight and obese children in need of epinephrine for anaphylaxis should be injected in the calf or in the lower thigh, rather than upper half of the thigh, to ensure intramuscular administration, according to findings from an ultrasound study of 93 children.
Ultrasound measurement demonstrated that the distance from skin surface to muscle depth was greater than auto-injector needle length at one quarter of the distance down the thigh in 82% of obese children vs. 25% of nonobese children. At three-quarters of the way down the thigh, this was the case in only 17% of obese children and 2% of nonobese children, Dr. Peter Arkwright reported at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.
At a point midway down the calf, the skin surface to muscle depth was less than the length of the auto-injector needle in all of the children, said Dr. Arkwright of the University of Manchester (England).
Intramuscular injection, rather than subcutaneous injection, is imperative for effective delivery of epinephrine, he said, noting that this study was undertaken because of growing concerns that increasing obesity among children could make existing auto-injectors inadequate for providing intramuscular delivery in a significant proportion of patients.
Children included in the study were patients from regional pediatric allergy clinics. All were measured for height, weight, and body mass index, and all underwent ultrasound measurement at set distances down the thigh and leg. Higher weight, BMI, and waist circumference – but not age or gender – were associated with skin surface to muscle depth greater than auto-injector needle length, he noted.
"Based on our study, injecting epinephrine into the lower rather than upper thigh would be advised in overweight or obese children," he said, adding that caregivers of children at risk of anaphylaxis should be advised about the importance of administering epinephrine into the muscle in the most effective way.
For overweight and obese children, this involves injecting into the lower half of the thigh, and for very obese children it involves injecting at the middle of the calf, he said.
Dr. Arkwright reported having no disclosures.