Non-Invasive Bedside Estimation of Nutrition Accretion and Extracellular Water Volume in Preterm Neonates during the First Three Weeks of Life

Abstract

Background: Evaluation of nutrients accretion and body water accumulation is critical but difficult in preterm neonates. There are minimal early postnatal anthropometry data available for this population. The newer sophisticated methods are too complex for routine use. Objective: To perform regional anthropometry and estimate extracellular water volume (ECW) in preterm infants during the first three weeks of life via Harpenden caliper application. Methods: Mid arm circumference ( MAC), arm fat area (AFA), arm muscle area (AMA), arm area (AA), arm water area (AWA) and extracellular water volume (ECW) were estimated in stable appropriate for gestational age preterm infants born consecutively during a designated study period with a Harpenden's caliper on days of life 10 and 21 under three weight groups: 500-1200 g, 1201 to 1800 g and 1801 to 2500 g. Students t and Kruskal - Wallis ranked tests and univariate regressions were performed for statistical analysis. Results: A total of 66 data were collected from 42 patients. All anthropometric variables increased transversely on days of life 10 and 21 among all weight groups, whereas, AWA/AA decreased. ECW decreased transversely between groups 1 and 3 on DOL 10 and 21. Highly significant and strong correlations were detected between body weight (BW) and AMA (0.88), BW and AFA (0.78), AFA and tricuspid skin fold thickness at 60 seconds of application (TSKF60 , 0.85), AMA and MAC (0.86) and AWA and tricuspid skin fold compressibility (∆TSKF, 0.56), yielding regression equations for dependent variables. Extrapolation of AFA and AMA regression lines predicted that fat and muscle tissues are not deposited in human fetus before 400 and 228.4 g of weight respectively. No side effects of the procedure were noted. Conclusion: The study presents the regression equations to calculate arm fat, lean body mass and water areas during early postnatal life in the extremely low birth weight and other preterm neonates via a simple bedside procedure, and documents their normative anthropometry reference data for ECW volume and caloric and lean body mass accretion. The extrapolated data reveal that fat and muscle tissues are not deposited in the human fetus before 400 g and 228.4 g of body weight.