Syndecan-1 as a Biomarker for Fluid Overload After High-Risk Pediatric Cardiac Surgery: A Pilot Study

Objective: Fluid overload (FO) after pediatric cardiac surgery with cardiopulmonary bypass (CPB) is common and has been associated with poor outcomes. We aimed to describe the relationship between plasma concentrations of syndecan-1 (SD1), a biomarker of endothelial glycocalyx injury, and FO in a cohort of children undergoing cardiac surgery. Design: Single-center prospective observational pilot study, 2022–2023. Setting: Twenty-six-bed pediatric cardiac ICU (CICU) at a quaternary pediatric referral center. Patients: Children younger than 18 years old undergoing Society of Thoracic Surgeons–European Association for Cardio-Thoracic Surgery congenital heart surgery mortality category 3, 4, and 5 cardiac surgeries with CPB. Interventions: None. Measurements and Main Results: We enrolled 15 patients. Blood samples were collected preoperatively and 4 hours postoperatively, then processed for plasma. SD1 concentrations were measured using enzyme-linked immunosorbent assays and compared with fluid balance on postoperative days (PODs) 1, 2, 3, and peak. SD1 discriminated fluid balance of greater than or equal to 10% on POD-1, POD-2, and POD-3 with an area under the receiver operating characteristic curve (AUROC) of 0.74, 0.84, and 0.88, respectively. SD1 also discriminated peak fluid balance of greater than or equal to 10% occurring on any day over the first seven PODs with an AUROC of 0.94. Patients with greater than or equal to 10% fluid balance on POD-2 ( p = 0.037), POD-3 ( p = 0.020), or peak ( p = 0.021) had significantly elevated delta SD1 when compared with those reaching less than 10%. Fluid balance of greater than or equal to 10% on POD-2 was associated with adverse events including longer duration of mechanical ventilation and CICU stay. Conclusions: Plasma SD1 was associated with FO in pediatric patients undergoing high-risk cardiac surgery with CPB. Further studies exploring the clinical utility of SD1 as a biomarker for FO in the postoperative management of children who undergo cardiac surgery with CPB should be pursued.