Determination of deltoid fat pad thickness. Implications for needle length in adult immunization
G. A. Poland, A. Borrud, R. M. Jacobson, K. McDermott, P. C. Wollan, D. Brakke and J. W. Charboneau
Mayo Vaccine Research Group, Clinical Pharmacology Unit, Rochester, MN 55905, USA.
OBJECTIVE: To measure deltoid fat pad thickness and determine the optimal
needle length for deltoid intramuscular immunization in healthy adults.
DESIGN, SETTING, AND PARTICIPANTS: Prospective study of 220 healthy health
care workers (126 women, 94 men) at the Mayo Medical Center, Rochester,
Minn. MAIN OUTCOME MEASURES: Deltoid fat pad thickness determined by
high-resolution ultrasound scanning, weight, height, and mid-deltoid arm
circumference. RESULTS: We found a highly significant difference between
women and men in deltoid fat pad thickness, with women having a thicker
deltoid fat pad (11.7 vs 8.3 mm; P<.001). Women had a greater deltoid
skin-fold thickness than men (34.7 vs 17.2 mm, P<.001) and an equal body
mass index. According to the ultrasound findings, a standard 16-mm (5/8-in)
needle would not have reached 5 mm into muscle in 17% (16/94) of men and
48.4% (61/126) of women in this study. CONCLUSIONS: Among healthy adults of
the age range we studied, the following needle lengths appear to be
appropriate for true deltoid intramuscular immunization: For men across the
weight ranges we studied (59-118 kg), use of a 25-mm (1-in) needle would
result in at least 5 mm of muscle penetration in all subjects. For women
who weighed less than 60 kg, a 16-mm (5/8-in) needle would be sufficient to
achieve muscle penetration of 5 mm. For women between 60 and 90 kg, a 25-mm
(1-in) needle would be sufficient, and women greater than 90 kg would
require a 38-mm (1.5-in) needle to ensure intramuscular administration.
