Background

Pediatric patients undergoing cardiac surgery are at risk for developing positive cumulative fluid balance (CFB). Our goal was to study postoperative CFB in this population, its explanatory variables, and its effect on clinical outcomes during pediatric intensive care unit (PICU) stay and follow-up.

Methods

Retrospective single center study of 200 consecutive children undergoing congenital heart surgery with cardiopulmonary bypass (CPB). A clinically relevant CFB was defined as ≥ 5% at the end of postoperative day 1 (CFB POD1 ≥ 5%).

Results

A CFB POD1 ≥ 5% was observed in 36% of the patients. Lower weight and longer CPB time were identified as explanatory variables for developing CFB POD1 ≥ 5%. Patients with CFB POD1 ≥ 5% showed more acute kidney injury, higher vasoactive inotropic scores, and prolonged invasive ventilation and PICU length of stay (LOS). A 1% increase in CFB POD1 lengthened PICU LOS by 0.8 days (CI 0.588 – 1.001, p < 0.001). Furthermore, patients with CFB POD1 ≥ 5% had lower cardiac event free survival time (p < 0.001).

Conclusions

This study confirms that even a minor positive CFB ≥ 5% is common in pediatric cardiac patients and associated with adverse PICU outcomes. Lower body weight and prolonged CPB duration increased the risk for positive CFB, warranting close fluid monitoring. Positive CFB was also associated with cardiac events during long-term follow-up and may help identify patients at increased risk for a complicated clinical trajectory, underscoring the importance of timely recognition and structured cardiac follow-up.