Abstract
The daily sodium requirement in very low birth weight infants is unknown. For this reason, sodium balance was studied in 16 consecutive neonates weighing <1200 grams at birth. Group I, 12 infants <30 weeks gestational age (955 ± 35 gms.); Group II, 4 infants >30 weeks gestational age (997 ± 78 gms.). Weight, sodium and fluid intake, and serum sodium were measured daily. 24 hour urinary sodium losses and creatinine clearances were determined on days 3 and 8.
Group I had greater mean urinary sodium losses on day 3 (17.1 vs. 2.9 mEq/kg/24hr., p <0.001) and were in negative sodium balance (-9.2 vs. + 1.0, p <0.02) compared to Group II. This was associated with a greater incidence of hyponatremia, and an increased weight loss through day 4 (12% vs. 3%). By day 8, Group I showed a significant rise in sodium balance compared to day 3 (+1.2 mEq/kg/24hr., p <0.001) and no longer differed from Group II.
There was no significant difference in mean creatinine clearance on day 3 between the groups (8.8 vs. 6.9 ml/min/1.73m2) and both groups showed a rise by day 8. Fractional sodium excretion was inversely correlated with creatinine clearance.
Thus, in the first days of life the group of infants <30 weeks gestational age was in negative sodium balance despite a mean sodium intake of 7.9 mEq/kg/d. This data suggests a very high daily sodium requirement in these immature infants.
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Engelke, S., Shah, B., Vasan, U. et al. SODIUM BALANCE IN VERY LOW BIRTH WEIGHT INFANTS. Pediatr Res 11, 549 (1977). https://doi.org/10.1203/00006450-197704000-01077
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DOI: https://doi.org/10.1203/00006450-197704000-01077