Colloid osmotic pressure in newborn infants: variations with birth weight, gestational age, total serum solids, and mean arterial pressure.

Colloid osmotic pressure (COP) of blood was measured directly at birth with the Wescor membrane colloid osmometer (model 4100) in 91 appropriately grown, 11 large, and nine small for gestational age "well" newborn infants. COP correlated directly with birth weight (r = .726, P less than .00001) and gestational age (r = .753, P less than .00001). COP values for small for gestational age (SGA) and large for gestational age (LGA) infants were found to fall within the 95% prediction interval with regard to birth weight and gestational age for appropriate for gestational age (AGA) infants. Simultaneous measurements of COP, total serum solids, and central arterial mean blood pressure were made. The results showed that COP correlated directly with total serum solids (r = .89, P less than .0001) and mean arterial blood pressure (r = .660, P less than .001). Among the factors evaluated, total serum solids was the best predictor of COP.