Evaluation of Hyponatremia in Infants on Vasopressin Therapy

Vasopressin has systemic vasoconstrictive yet pulmonary vasodilatory effects, making it an ideal agent for hypotension management in infants with congenital diaphragmatic hernia (CDH)-associated pulmonary hypertension. The side effects of vasopressin in this population, such as hyponatremia, are understudied. This study aims to characterize the effect of vasopressin on sodium concentrations in infants with and without CDH.

This was a retrospective review of patients who received vasopressin while admitted to a level IV neonatal intensive care unit. The primary outcome was the incidence of hyponatremia (blood sodium <135 mmol/L) during vasopressin therapy. Secondary outcomes included time to hyponatremia, dose and duration of vasopressin, incidence of severe hyponatremia (blood sodium <125 mmol/L), and hypertonic saline use. Both blood serum and blood gas sample sodium concentrations were used to compare CDH vs non-CDH patients.

The average difference between baseline and lowest blood sodium was significant for both CDH and non-CDH patients for all samples (p < 0.001). There was no significant difference in the primary outcome, nor in the secondary outcomes of time to hyponatremia or duration of vasopressin infusion. The average dose of vasopressin was higher in the CDH vs non-CDH group (p = 0.018). The incidences of severe hyponatremia and hypertonic saline use were greater in the CDH vs non-CDH group for patients who had blood serum sodium samples collected (p = 0.049 and p = 0.033, respectively).

This study showed that severe hyponatremia occurred more frequently in CDH vs non-CDH patients. Extreme caution is necessary when managing total body sodium in patients with CDH.