Natural history of nonimmune-mediated thrombocytopenia and acute kidney injury in pediatric open-heart surgery

Objective: Thrombocytopenia and acute kidney injury (AKI) are common following pediatric cardiac surgery with cardiopulmonary bypass (CPB). However, the relationship between postoperative nadir platelet counts and AKI has not been investigated in the pediatric population. Our objective was to investigate this relationship and examine independent predictors of AKI.

Design: After IRB approval, we performed a retrospective review of the institution's medical records and database.

Setting: This study was performed at a single institution over a 5-year period.

Patients: We included patients <21 years of age undergoing cardiac surgery with CPB.

Interventions: Demographics, laboratory, and surgical characteristics were captured, and clinical event rates were recorded.

Measurements: Descriptive statistics were used to evaluate platelet and creatinine distributions. T-tests and chi-squared tests were used to compare characteristics among Acute Kidney Injury Network groups. Multivariable logistic and ordinal logistic regression models were used to determine the association of our predictor of interest, postoperative nadir platelet count and AKI.

Results: Eight hundred and fourteen patients (23% infants and 23% neonates) were included in the analysis. Postoperative platelet counts decreased 48% from baseline reaching a mean nadir value of 150 × 10⁹ ·l^-1 on postoperative day 3. AKI occurred in 37% of patients including 13%, 17%, and 6% with Acute Kidney Injury Network stages 1, 2, and 3, respectively. The magnitude of nadir platelet counts correlated with the severity of AKI. Independent predictors of severity of AKI include nadir platelet counts, CPB time, Aristotle score, patient weight, intra-operative packed red blood cell transfusion, and having a heart transplant procedure.

Conclusions: In pediatric open-heart surgery, thrombocytopenia and AKI occur commonly following CPB. Our findings show a strong association between nadir platelet counts and the severity of AKI.