Nucleated red blood cells (NRBCs) are immature red cells that under normal conditions are not present in the peripheral circulation. Several studies have suggested an association between elevated NRBC and poor outcome in critically ill adults and neonates. We sought to determine if elevations in NRBC value following cardiac surgery and following clinical events during the hospital stay can be used as a biomarker to monitor for mortality risk in neonates post-cardiac surgery.

We constructed a retrospective study of 264 neonates who underwent cardiac surgery at Children’s Hospital, New Orleans between 2011 and 2020. Variables included mortality and NRBC value were recorded following cardiac surgery and following peri-operative clinical events. The study was approved by LSU Health IRB. Sensitivity, specificity, receiver operating characteristic (ROC) curves with area under the curve (AUC) and logistic regression analysis were performed.

Thirty-six patients (13.6%) died, of which 32 had an NRBC value ≥10/100 white blood cell (WBC) during hospitalisation. Multi-variable analysis found extracorporeal membrane oxygenation use (OR 10, 95% CI 2.9–33, p=<0.001), NRBC ≥10/100 WBC (OR 16.1, CI 4.1–62.5, p ≤ 0.001) and peak NRBC in the 14-day period post-cardiac surgery (continuous variable, OR 1.05, 95% CI 1.0–1.09, p = 0.03), to be independently associated with mortality. Using a cut-off NRBC value of 10/100 WBC, there was an 88.9% sensitivity and a 90.8% specificity, with ROC curve showing an AUC of 0.9 and 0.914 for peak NRBC value in 14 days post-surgery and entire hospitalisation, respectively.

NRBC ≥10/100 WBC post-cardiac surgery is strongly associated with mortality. Additionally, NRBC trend appears to show promise as an accurate biomarker for mortality.