Effect of sodium deficiency on growth of surgical infants: a retrospective observational study

Sodium is thought to be critical to growth. Infants who have an ileostomy may suffer from growth faltering, as sodium losses from stomas may be excessive. Urinary sodium measurements may indicate which patients could benefit from sodium supplementation; however, there is no consensus on what level of urinary sodium should be the cutoff for intervention. Our aim was to determine whether there is a relationship between urinary sodium and growth in infants undergoing ileostomy, colostomy and cystostomy. Following audit approval, a retrospective observational study of patient notes and chemical pathology data was carried out. All infants < 1 year of age that had an ileostomy, colostomy, or cystostomy procedure between February 1997 and January 2014 were included. Patients' weights, urinary and serum sodium and potassium levels and clinical variables were recorded until discharge. Weights were converted to Z-scores for analysis. Forty patients were identified whose notes were available for review and who had at least three urinary sodium measurements. During their hospital stay, 11 (28 %) maintained weight within normal limits (Z-scores -2 to +2, 15 (38 %) were moderately malnourished (-3 to -2) and 14 (35 %) severely malnourished (<-3). Thirty patients had at least one urinary sodium < 10 mmol/litre, six patients had their lowest recorded urinary sodium between 10 and 30 mmol/litre and only four patients had all their urinary sodium measurements > 30 mmol litre. Electrolyte data were not normally distributed so that correlations between electrolytes and growth were tested using the non-parametric Spearman rank correlation coefficient. Urinary sodium levels positively correlated with growth (r = 0.3071, p < 0.0001), as did serum sodium levels (r = 0.2620, p = 0.0059) whereas there was no relationship between urine or serum potassium and growth. Poor growth is frequent in this group of patients and appears to be linked with sodium levels. Further work is necessary to draw up guidelines for appropriate sodium supplementation.