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Current Pediatric Reviews


ISSN (Print): 1573-3963
ISSN (Online): 1875-6336

Research Article

Nucleated Red Blood Cell Emergence-Time in Newborn Lambs Following a Dose of Darbepoetin Alfa

Author(s): Timothy M. Bahr*, Kurt H. Albertine, Robert D. Christensen, Mar Janna Dahl, Andrew Rebentisch, Elaine Dawson, Emily Major, Hannah Foreman, David Headden, Zoë Vordos, Akbarali Nabi, Luke Pettet, Peter Badrov, Connor Addison and Daniel R. Christensen

Volume 19, Issue 4, 2023

Published on: 22 December, 2022

Page: [425 - 428] Pages: 4

DOI: 10.2174/1573396319666221219153902

Price: $65


Background: Nucleated red blood cells (NRBC) are very uncommon in the blood of children and adults, but small numbers are not rare in neonates on the day of birth. Elevated NRBC counts in neonates can be seen following erythropoietin dosing. Limited studies in human neonates suggest the time-interval between erythropoietin dosing and the first appearance of NRBC in the blood (the “NRBC emergence-time”) is in excess of 24 hours.

Methods: We made serial blood counts (Sysmex veterinary analyzer) on ten newborn lambs; five were dosed with darbepoetin (10 μg/kg), and five were dosed with a vehicle-control to assess the NRBC emergence time under relatively controlled laboratory conditions.

Results: The first appearance of NRBC was at 24 h (2757 ± 3210 NRBC/μL vs. 0/μL in controls). Peak was 48-72 h (16,758 ± 8434/μL vs. 0/μL in controls), followed by fewer at 96 hours (7823 ± 7114/μL vs. 0/μL in controls). Similarly, reticulocytes peaked at 48-72 h (113,094 ± 3210/μL vs. 10,790 ± 5449/μL in controls), with no changes in platelets or leukocytes.

Conclusion: The NRBC emergence time in newborn lambs is similar to reports from newborn humans. By extrapolation, if a neonate has a high NRBC at birth, the erythropoietic stimulus likely occurred within the interval 24 to perhaps 96+ hours prior to birth.

Keywords: Nucleated red blood cells, erythropoietin dosing, platelets or leukocytes, gestational age, newborn lambs, darbepoetin.

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