Quantitative Measurement of Muscle and Subcutaneous Fat Thickness in Newborn by Real-Time Ultrasonography: A Useful Method for Site and Depth Evaluation in Vaccination

In order to quantify muscle thickness and choose the appropriate site for intramuscular injuction of vaccines in neonates, we used ultrasonography to measure muscle and subcutaneous fat thickness of anterolateral mid-thigh, upper outer quadrant of buttock and middle area of deltoid in fifty full term (group 1) and thirty low birth weight (group 2) infants. A Hitachi EUB40 real-time scanner and a 5 MHz transducer was used in the study. We delineated the normal distribution of muscle and subcutaneous fat thickness in mid-thigh, buttock and deltoid areas of full term and low birth weight infants. There was no significant difference between male and female infants in the two groups. Muscle and subcutaneous fat thickness in the thigh area was 11.8 ± 1.9 mm and 3.8 ± 0.4 mm, respectively, in group 1; 8.6 ± 1.7 mm and 2.7 ± 0.5 mm in group 2. Figures in the buttock area were 10.1 ± 1.5mm and 3.7 ± 0.5mm in group 1, 6.9 ± 1.2mm and 2.7 ± 0.7 mm in group 2; and in the deltoid area were 5.2 ± 0.7 mm and 3.4 ± 1.5 mm in group 1 and 3.8 ± 0.8 mm and 2.3 ± 0.6 mm in group 2. There was significant logarithmic correlation between muscle thickness and body weight (r=0.6, 0.8, 0.6) and muscle thickness and body length (r=0.4, 0.6, 0.6) in thigh, buttock and deltoid areas of the low birth weight infants. In contrase, there was significant logarithmic correlation only between buttock muscle and body weight (r=0.5) in the full term infants. We concluded that the ultrasonic method is a simple technique, easily performed in clinical use for muscle and subcutaneout fat thickness measurement. The mid-thigh muscle was found to be the thickest at the absence of risk to nerve injury. So, the mid-thigh is the preferred site and is recommended for intramuscular vaccination in the neonates. Intramuscular injection of vaccines should be performed with care, especially in low bith weight infants, because of thin muscle layers. The results of this study should be a useful guideline for assessment.