Neonatal metabolic acidosis: effect of chloride from normal saline flushes

Metabolic Acidosis is a reported complication of total parenteral nutrition (TPN). A large number of infants receiving TPN in an NICU were noted to have metabolic acidosis. We evaluated the effect of lowering the chloride intake on the incidence of metabolic acidosis in low birth weight (LBW) infants on TPN. Standard TPN solutions were adjusted to provide about 2-3 mEq/kg/day chloride instead of 5-7 mEq/kg/day provided previously. Most infants on TPN received approximately another 1-3 mEq/kg/day from intravenous and arterial line flushes with normal saline. Ten infants who had been on the original TPN solutions were compared to 10 infants who were on the revised TPN solutions. Serum pH, bicarbonate, and base deficit were used to measure acidosis. Medical records were reviewed for the number of days the infants had abnormal values. Serum chloride levels were also recorded. While similar in gestational age, birth weight, age during study period, days on TPN, and days on orally supplemented parenteral nutrition, the group with higher chloride intake had significantly more days of metabolic acidosis. They also had significantly higher serum chlorides. It is concluded that a total chloride load in excess of 6 mEq/kg/day in LBW infants receiving TPN is associated with more metabolic acidosis. Also, if saline is used for clearing of intravenous and arterial lines, standard TPN solutions should be formulated with consideration of the total chloride load.