Regulation of erythropoiesis in the newborn: a complex system

Erythropoietin concentration in developing harbor seals (Phoca vitulina)

Tissue hypoxia elicits the production of erythropoietin (Epo), a hormone that stimulates red blood cell production. In young diving mammals, oxygen is stored primarily in the blood, and blood oxygen stores increase significantly during the first weeks of life. In an effort to establish the role of Epo during this period of blood development, this study measured Epo concentration in plasma of 134 harbor seal (Phoca vitulina) pups and adults. Concurrent measurements of hematocrit (Hct), hemoglobin concentration [Hb], and red blood cell (RBC) counts allowed the evaluation of the effect of Epo on blood oxygen store capacity. Erythropoietin and most blood parameters varied with age. At birth, neonatal [Hb], Hct, and RBC were elevated, possibly due to the rapid expansion of plasma volume associated with growth rates of 0.5 kg/day. In contrast, Epo concentration increased from 6.64 +/- 0.83 mU/ml in newborns to 9.53 +/- 0.86 mU/ml in early nursing pups. Erythropoietin concentration remained elevated above newborn and adult concentration (5.71 +/- 0.79 mU/ml) through weaning, suggesting that Epo was responding to tissue hypoxia brought on by early anemia. Since similar changes in erythropoietin have been documented in terrestrial mammals, it appears that Epo plays a similar role in the blood development of harbor seals.

Use of erythropoietin in premature neonates: controversies and the future

OBJECTIVE

To review and evaluate current research on the use of recombinant human erythropoietin (rhEPO) for the treatment of anemia of prematurity (AOP).

DATA SOURCES

A MEDLINE search (1985-September 1994) was used to identify and retrieve pertinent data about erythropoietin's use in premature neonates. Bibliographies in the relevant literature and International Pharmacy Abstracts were reviewed as well.

STUDY SELECTION

The authors extrapolated data from trials and other literature in which the entire paper or abstract was published. Because of the paucity of data on the use of rhEPO in neonates, all available literature was reviewed and cited, regardless of study methodology.

DATA SYNTHESIS

Most data support that rhEPO is efficacious in treating AOP. Until recently, the published investigations have included only small numbers of patients. Larger, multicenter, placebo-controlled trials suggest that infants weighing less than 1500 g benefit from rhEPO therapy. Questions remain concerning the rhEPO dose and nutrient requirements for optimal efficacy.

CONCLUSIONS

Published clinical trials that have examined the efficacy of rhEPO in the treatment of AOP vary considerably with regard to methodology, rhEPO dose, nutrient doses, and outcome measurement. At present, many questions remain to be answered including ascertaining rhEPO's long-term benefit versus cost/risk as well as its potential contribution to improving the care of the premature neonate.