To explore different types of metabolic acidosis in acute gastroenteritis of infancy, and to correlate it with nutritional status and clinical outcome, we examined prospectively 27 consecutive infants admitted with moderate to severe dehydration and arterial blood pH 7.20. Serum anion gap, creatinine, divalent cations (Ca, Mg), and the anionic contribution of total protein, lactate, and phosphate as well as ketones and urine pH, were determined on admission and compared with age-matched controls. Twenty infants (Group A) presented with normal anion gap (13.1 ± 2.7) associated with hyperchloremia (115.8 ± 4.2 mmol/L, p < 0.01) and diminished bicarbonate (9.7 ± 2.4 mmol/L, p < 0.01), compared with controls. The other seven infants (group B) demonstrated an increased anion gap (26.7 ± 3.2, p < 0.01), associated with significant elevations of lactate (3.4 ± 0.7 mmol/L, p < 0.001), total protein (93.4 ± 12.3 g/L, p < 0.01), as well as phosphate (2.3 ± 0.2 mmol/L, p < 0.01) and creatinine (164.9 ± 45.1 μmol/L, p < 0.001), compared with controls. No significant deviations of blood divalent cations or ketones were noted in both groups. Urine pH was ± 5.5 in all subjects. Analysis of nutritional status and clinical outcome in both groups revealed significant differences. Infants in group B, compared with group A, were significantly more severely malnourished (7 of 7 versus 4 of 20, p < 0.001), were more likely to have prolonged diarrhea ( > 14 days) (5 of 7 versus 3 of 20, p < 0.001), and required longer durations of both intravenous therapy (6.7 ± 2.3 versus 2.2 ± 0.7 days, p < 0.001) and hospitalization (19.4 ± 4.6 versus 5.4 ± 1.6 days, p < 0.001). We conclude that some infants with acute diarrhea may develop severe dehydration and anion-gap acidosis associated with lactic acidemia and renal dysfunction. These high-risk infants more often demonstrate severe malnutrition, persistent course of diarrhea, and prolonged hospital stay. Early identification of such infants, and aggressive therapy, will probably improve outcome.
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