title: Adaptive responses during anemia and its correction in lambs.
abstract: There is limited information available on which to base decisions regarding red blood cell (RBC) transfusion treatment in anemic newborn infants. Using a conscious newborn lamb model of progressive anemia, we sought to identify accessible metabolic and cardiovascular measures of hypoxia that might provide guidance in the management of anemic infants. We hypothesized that severe phlebotomy-induced isovolemic anemia and its reversal after RBC transfusion result in a defined pattern of adaptive responses. Anemia was produced over 2 days by serial phlebotomy (with plasma replacement) to Hb levels of 30-40 g/l. During the ensuing 2 days, Hb was restored to pretransfusion baseline levels by repeated RBC transfusion. Area-under-the-curve methodology was utilized for defining the Hb level at which individual study variables demonstrated significant change. Significant reciprocal changes (P < 0.05) of equivalent magnitude were observed during the phlebotomy and transfusion phases for cardiac output, plasma erythropoietin (Epo) concentration, oxygen extraction ratio, oxygen delivery, venous oxygen saturation, and blood lactate concentration. No significant change was observed in resting oxygen consumption. Cardiac output and plasma Epo concentration increased at Hb levels <75 g/l, oxygen delivery and oxygen extraction ratio decreased at Hb levels <60 g/l, and venous oxygen saturation decreased and blood lactate concentration increased at Hb levels <55 g/l. We speculate that plasma Epo and blood lactate concentrations may be useful measures of clinically significant anemia in infants and may indicate when an infant might benefit from a RBC transfusion.
authors.affiliation: Department of Pediatrics, College of Medicine, The University of Iowa, Iowa City 52242, USA. john-widness@uiowa.edu
authors.forename: J A
authors.initials: JA
authors.lastname: Widness
authors.forename: L S
authors.initials: LS
authors.lastname: Lowe
authors.forename: E F
authors.initials: EF
authors.lastname: Bell
authors.forename: L F
authors.initials: LF
authors.lastname: Burmeister
authors.forename: D M
authors.initials: DM
authors.lastname: Mock
authors.forename: J A
authors.initials: JA
authors.lastname: Kistard
authors.forename: H
authors.initials: H
authors.lastname: Bard
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000740:Anemia / Q000503:physiopathology* / Q000628:therapy; D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D017707:Erythrocyte Transfusion; D004921:Erythropoietin / Q000097:blood; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D007231:Infant, Newborn; D007773:Lactates / Q000097:blood; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D018962:Phlebotomy; D012756:Sheep; D013318:Stroke Volume; D013997:Time Factors; D014655:Vascular Resistance
chemical_list: D007773:Lactates; D004921:Erythropoietin; D010100:Oxygen