Bedside ultrasound imaging to measure muscle cross-sectional area in preterm and term infants: a feasibility study

BACKGROUND/OBJECTIVE: Lean body mass is linked to improved outcomes, but infant muscle-specific tools are limited. Bedside ultrasound measurements of muscle cross-sectional area (CSA) may overcome these limitations. STUDY DESIGN: A prospective cohort of 60 infants at two neonatal intensive care units (NICUs) underwent serial ultrasound biceps CSA, rectus femoris CSA, and anthropometric measurements. Intraclass correlation coefficients (ICC) assessed measurement reliability. Spline mixed models examined associations between muscle CSA and birth gestational age, growth, postmenstrual age (PMA), and nutrition. RESULTS: Intra- and inter-rater ICCs ranged from 0.92 to 0.99 and from 0.77 to 0.91. No safety events occurred. Biceps CSA correlated with birth gestational age, PMA, weight, length, head circumference, and mid-upper arm circumference (p ≤ 0.01). Rectus femoris CSA correlated with birth gestational age, weight, length, head circumference, and mid-thigh circumference (p < 0.05). CONCLUSION: Bedside ultrasound is feasible, safe, and reliable for muscle CSA measurement in NICU infants.