Pathogenesis of Metabolic Acidosis in Preterm Infants

Objective: To determine how the balance between mineral base, and carbonic and organic acids is altered to cause metabolic acidosis in preterm infants. Study Design: Mineral balance and arterial blood measurements of 3 groups of preterm infants given 5 different Total Parenteral Nutrition (TPN) regimens were analyzed. Mineral base was measured as the difference between mineral cations and anions. Organic acid was measured as the difference between mineral base, bicarbonate and protein anion. Results: The degree of metabolic acidosis measured as base excess, was determined by deviation in both mineral base and organic acid from normal. Sodium minus chloride balance determined change in arterial blood mineral base. TPN containing more chloride than sodium caused mineral acidosis with low mineral base, whereas TPN containing more sodium than chloride caused mineral alkalosis with high