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Adaptive responses during anemia and its correction in lambs
J A Widness1, L S Lowe, E F Bell
1Department of Pediatrics, College of Medicine, The University of Iowa, Iowa City 52242, USA. john-widness@uiowa.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 6, 2000
Summary
This study identified key indicators like cardiac output and blood lactate to manage anemia in newborn lambs. These measures can help determine when red blood cell transfusions are needed for anemic infants.
Area of Science:
- Neonatal physiology
- Hematology
- Critical care medicine
Background:
- Limited data exists for guiding red blood cell (RBC) transfusion decisions in anemic neonates.
- Anemia management in newborns requires better objective measures of physiological compromise.
Purpose of the Study:
- To identify accessible metabolic and cardiovascular markers of hypoxia in anemic newborn infants.
- To establish patterns of adaptive responses to anemia and subsequent RBC transfusion.
Main Methods:
- A conscious newborn lamb model was used to induce progressive, isovolemic anemia via serial phlebotomy.
- Red blood cell (RBC) transfusion restored hemoglobin (Hb) levels, with area-under-the-curve analysis identifying critical Hb thresholds for physiological changes.
- Measurements included cardiac output, plasma erythropoietin (Epo), oxygen extraction ratio, oxygen delivery, venous oxygen saturation, and blood lactate.
Main Results:
- Significant reciprocal changes were observed in cardiac output, plasma Epo, oxygen extraction ratio, oxygen delivery, venous oxygen saturation, and blood lactate during anemia and transfusion.
- Cardiac output and Epo increased at Hb <75 g/l; oxygen delivery and extraction decreased at Hb <60 g/l.
- Venous oxygen saturation decreased and blood lactate increased at Hb <55 g/l, while resting oxygen consumption remained unchanged.
Conclusions:
- Plasma erythropoietin (Epo) and blood lactate concentrations show potential as useful clinical indicators of significant anemia in infants.
- These markers may aid in determining the optimal timing for red blood cell (RBC) transfusions in anemic neonates.