Skin and subcutaneous thickness at injecting sites in children with diabetes: ultrasound findings and recommendations for giving injection.

BACKGROUND Children who inject insulin need clear guidelines as to the length of needle best for them. We studied the distance from surface to muscle in children in order to make needle choices which are evidence-based. METHODS One hundred one children with type 1 diabetes were divided into three groups according to age: 2-6, 7-13, and 14-17 yr. The thickness of skin and subcutaneous (SC) tissue was measured by ultrasound in all injection sites. RESULTS Skin thickness varied from 1.58 mm in the arm of the youngest children to 2.29 mm in the buttocks of the adolescents. Values decreased progressively based on age (2-6 < 7-13 < 14-17) and on body site (arm < thigh < abdomen < buttocks). Skin + SC thickness varied in a similar fashion. The skin surface to muscle distances were <4 mm in nearly 10% of children, especially in the 2-6 yr group. In this group, the rate of intramuscular (IM) injections using the 4-mm pen needle when a pinch-up is not used would be 20.2%. This rate of IM injections doubles when using the 5-mm needle, and when injections are given under similar conditions it triples using the 6-mm needle. CONCLUSIONS It seems medically appropriate for all children to use short needles where possible to minimize inadvertent IM injections which may increase glycemic variability. Currently, the safest needle for all children appears to be the 4-mm pen needle. However, when used in children aged 2-6 yr, it should be used with a pinched skin fold.