Fluid Overload Is Associated With Higher Mortality and Morbidity in Pediatric Patients Undergoing Cardiac Surgery*

Objectives: Fluid overload after pediatric cardiac surgery is common and has been shown to increase both mortality and morbidity. This study explores the risk factors of early postoperative fluid overload and its relationship with adverse outcomes. Design: Secondary analysis of the prospectively collected data of children undergoing open-heart surgery between 2004 and 2008. Setting: Tertiary national cardiac center. Patients: One thousand five hundred twenty consecutive pediatric patients (< 18 years old) were included in the analyses. Interventions: None. Measurements and Main Results: In the first 72 hours of the postoperative period, the daily fluid balance was calculated as milliliter per kilogram and the daily fluid overload was calculated as fluid balance (L)/weight (kg) x 100. The primary endpoint was in-hospital mortality; the secondary outcomes were low cardiac output syndrome and prolonged mechanical ventilation. One thousand three hundred and sixty-seven patients (89.9%) had a cumulative fluid overload below 5%; 120 patients (7.8%), between 5% and 10%; and 33 patients (2.1%), above 10%. After multivariable analysis, higher fluid overload on the day of the surgery was independently associated with mortality (adjusted odds ratio, 1.14; 95% CI, 1.008-1.303; p = 0.041) and low cardiac output syndrome (adjusted odds ratio, 1.21; 95% CI, 1.12-1.30; p = 0.001). Higher maximum serum creatinine levels (adjusted odds ratio, 1.01; 95% CI, 1.003-1.021; p = 0.009), maximum vasoactive-inotropic scores (adjusted odds ratio, 1.01; 95% CI, 1.005-1.029; p = 0.042), and higher blood loss on the day of the surgery (adjusted odds ratio, 1.01; 95% CI, 1.004-1.025; p = 0.015) were associated with a higher risk of fluid overload that was greater than 5%. Conclusions: Fluid overload in the early postoperative period was associated with higher mortality and morbidity. Risk factors for fluid overload include underlying kidney dysfunction, hemodynamic instability, and higher blood loss on the day of the surgery.