Vasopressin Therapy Among Postoperative Variables Associated with Hyponatremia and Sodium Variability in Infants Following Congenital Heart Disease Surgery

Background: The increased hospital morbidity and mortality associated with hyponatremia is well recognized in the critically ill pediatric population. Neonates and infants exposed to vasopressin following cardiopulmonary bypass (CPB) may be at increased risk for hyponatremia. We aimed to determine the associated effect and potential risk factors leading to hyponatremia and sodium variability in the immediate postoperative period in neonates and infants up to 90 days of age exposed to vasopressin following surgery for congenital heart disease. Methods: This was a retrospective review of 75 consecutive patients at a single tertiary cardiac intensive care unit (CICU) from 2018 to 2020. Using mixed-effects linear regression, we compared sodium trends and variability between the groups who did and did not receive vasopressin. Results: While sodium levels fell in both groups, beyond the first postoperative day, the group exposed to vasopressin had a significantly increased fall in sodium relative to the control (p < 0.001). Vasopressin exposure was associated with increased within-day sodium variability on postoperative days one and two (p < 0.05). Total incidents of moderate to severe hyponatremia (sodium < 130 mmol/L) were higher in the vasopressin group but did not reach statistical significance. Age, volume of modified ultrafiltration, and total diuretic dose were not risk factors for either effect in this study. Conclusions: While all patients in this study appeared to be at risk of postoperative hyponatremia, cumulative vasopressin dose appeared to increase the risk for absolute hyponatremia as well as greater sodium variability within the early postoperative period.