338 - Implications of an Elevated Nucleated Red Blood Cell Count in Neonates with Moderate to Severe Hypoxic-Ischemic Encephalopathy

Friday, April 22, 2022

6:15 PM – 8:45 PM US MT

Poster Number: 338
Publication Number: 338.122

Timothy M. Bahr, Intermountain Healthcare, Salt Lake City, UT, United States; Robin K. Ohls, University of Utah, Salt Lake City, UT, United States; Mariana Baserga, University of Utah, Park City, UT, United States; Shelley M. Lawrence, University of Utah School of Medicine, Salt Lake City, UT, United States; Sarah L. Winter, University of Utah, Salt Lake City, UT, United States; Robert D. Christensen, University of Utah School of Medicine, Salt Lake City, UT, United States

Presenting Author(s)

Timothy M. Bahr, MD

Assistant Professor of Pediatrics
Intermountain Health/University of Utah
Salt Lake City, Utah, United States

Background: A high nucleated red blood cell (NRBC) count in a neonate immediately after birth is sometimes interpreted as an indicator of significant in utero hypoxia. However, questions remain regarding how to interpret a NRBC count (normal vs. elevated) during the hours and days following birth. This uncertainty is particularly applicable to neonates with hypoxic-ischemic encephalopathy (HIE) receiving therapeutic hypothermia (TH). We conducted the present multihospital retrospective cohort analysis in an attempt to provide some of these answers and to augment the growing body of literature on the significance and usefulness of NRBC counts in neonates with HIE receiving TH.

Objective: To investigate associations between nucleated red blood cell (NRBC) counts of neonates with hypoxic-ischemic encephalopathy (HIE), acute perinatal sentinel events, and neurodevelopmental outcomes. We also examined the mechanism causing elevated counts.

Design/Methods: We retrospectively analyzed neonates with HIE treated with therapeutic hypothermia (TH) who had at least three NRBC counts during their NICU course and received neurodevelopmental evaluation at 24±6 months.

Results: Ninety-five (63%) of 152 neonates meeting criteria had normal NRBC counts after birth, defined as ≤95th percentile upper reference interval; while 57 (37%) had elevated counts. Neonates with a documented sentinel event during labor resulting in emergent delivery (e.g. acute abruption) (n=79) almost invariably had a normal NRBC count (odds ratio 257; 95% CI, 33 - 1988). Of the 152 infants evaluated, 134 (88%) survived to discharge. When the first NRBC count was normal, the odds of surviving were three-fold greater (OR 3.0; 95% CI, 1.1 - 8.3) than when it was elevated. Normal counts were moderately predictive of infants without neurodevelopmental impairment at two-year evaluation (p < 0.001). The NRBC half-life was longer in those with elevated versus normal NRBC counts, 60 versus 39 hours (p < 0.01).Conclusion(s): In neonates with HIE, a normal NRBC count after birth was highly associated with having had an acute intrapartum event necessitating emergent delivery. Normal counts were modestly predictive of better prognosis. We speculate that elevated NRBC counts resulted from hypoxia that occurred earlier or chronically. Impaired clearance of NRBC from the blood is one mechanistic explanation for the high counts.