Key Points:
The incidence of AKI while undergoing ECMO in pediatric patients is high and independently increases mortality.
Laboratory markers consistent with intravascular hemolysis increase the hazard of a composite outcome of AKI or RRT while undergoing ECMO.
Further research into appropriate monitoring or treatment of ECMO-associated hemolysis may lead to important interventions to prevent AKI.
Background: AKI is common in patients requiring extracorporeal membrane oxygenation (ECMO), with a variety of proposed mechanisms. We sought to describe the effect of laboratory evidence of ECMO-associated intravascular hemolysis on AKI and RRT.
Methods: This retrospective cohort study included patients treated with ECMO at a single center over 10 years. The primary outcome was a composite of time to RRT or AKI (by creatinine-based Kidney Disease Improving Global Outcomes criteria) after ECMO start. Serum creatinine closest to ECMO start time was considered the pre-ECMO baseline and used to determine abnormal kidney function at ECMO start. The patient's subsequent creatinine values were used to identify AKI on ECMO. Multivariable cause-specific Cox proportional hazards models were used to assess the effect of separate markers of intravascular hemolysis on the time to the composite outcome after controlling for confounders.
Results: Five hundred and one children were evaluated with a median age 1.2 years, 56% male. Four separate multivariable models, each with a different marker of hemolysis (plasma-free hemoglobin, lactate dehydrogenase (LDH), minimum platelet count, and minimum daily hemoglobin), were used to examine the effect on the composite outcome of AKI/RRT. An elevated plasma-free hemoglobin, the most specific of these hemolysis markers, demonstrated an almost three-fold higher adjusted hazard for the composite outcome (hazard ratio [HR], 2.9; P value < 0.01; 95% confidence interval [CI], 1.4 to 5.6). Elevated LDH was associated with an adjusted HR of 3.1 (P value < 0.01; 95% CI, 1.7 to 5.5). Effect estimates were also pronounced in a composite outcome of only more severe AKI, stage 2+ AKI/RRT: HR 6.6 (P value < 0.01; 95% CI, 3.3 to 13.2) for plasma-free hemoglobin and 2.8 (P value < 0.01; 95% CI, 1.5 to 5.6) for LDH.
Conclusions: Laboratory findings consistent with intravascular hemolysis on ECMO were independently associated with a higher hazard of a composite outcome of AKI/RRT in children undergoing ECMO.