Plasma chloride and alkalaemia in pyloric stenosis.

Fifty infants with infantile hypertrophic pyloric stenosis were studied prospectively to evaluate the reliability of plasma chloride estimation in the assessment of the acid-base status on admission and during correction of alkalaemia. Four cases were subsequently excluded because of a breach of the study protocol, leaving 46 cases in the study. Seventeen (37 per cent) were normoacidaemic on admission; 13 had plasma chloride concentrations of greater than or equal to 106 mmol/l and four had chloride concentrations of 100-105 mmol/l on admission. Twenty-nine (63 per cent) were alkalaemic on admission; six cases had chloride concentrations of 100-105 mmol/l and 23 cases had concentrations of less than 100 mmol/l. Of those 29 cases requiring correction of alkalaemia, normoacidaemia was achieved at a plasma chloride concentration of greater than or equal to 106 mmol/l in 21 cases (72 per cent) and at a concentration of 100-105 mmol/l in eight cases (28 per cent). Plasma chloride is a reliable parameter in the assessment and correction of alkalaemia in infantile hypertrophic pyloric stenosis provided that a concentration of at least 106 mmol/l is the goal.