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Changes in circulating red cell volume during the first 6 weeks of life in very-low-birth-weight infants
Edward F Bell1, Claude Nahmias2, John C Sinclair3
1Department of Pediatrics, University of Iowa, Iowa City, Iowa.
Insights
Red cell volume (RCV) in very-low-birth-weight infants decreases during the first six weeks of life. This decline occurs even when red blood cell (RBC) losses from blood draws are fully replaced by transfusions.
Area of Science:
- Neonatal Physiology
- Hematology
Background:
- Limited understanding of red cell volume (RCV) changes in very-low-birth-weight (VLBW) infants during early life.
- Anemia of prematurity is a common complication in VLBW infants.
Purpose of the Study:
- To investigate the changes in circulating red cell volume (RCV) in very-low-birth-weight (VLBW) infants during the first six weeks of life.
- To determine if red blood cell (RBC) transfusions compensate for blood loss due to phlebotomy in VLBW infants.
Main Methods:
- RCV was measured in 35 VLBW infants using chromium-51 labeling of RBCs within the first 5 days of life.
- RCV was re-measured at 6 weeks in 12 infants, with detailed recording of RBCs lost via phlebotomy and gained via transfusion.
- Radioactive counting was used to measure blood waste on phlebotomy materials in six infants.
Main Results:
- The mean RCV in the first few days of life was 39.6 ml/kg (range: 20.1-58.7 ml/kg).
- In 11 of 12 infants, absolute RCV decreased between the initial measurement and 6 weeks of age (mean initial RCV: 37.3 ml; mean 6-week RCV: 26.6 ml).
- Mean RBC loss from phlebotomy was 29.2 ml, while mean RBC transfusion volume was 34.5 ml.
Conclusions:
- Circulating red cell volume (RCV) declines in very-low-birth-weight (VLBW) infants during the first six weeks of life.
- This RCV decrease persists despite complete replacement of RBCs lost through diagnostic phlebotomy with transfusions.
- The findings suggest complex factors contribute to the evolving anemia of prematurity beyond simple blood loss and replacement.
Background:
Little is known about the change in circulating red cell volume (RCV) of very-low-birth-weight (VLBW) infants during the first weeks of life.
Methods:
RCV was measured during the first 5 d in 35 VLBW infants using chromium-51 labeling of the infants' red blood cells (RBCs). RCV was measured again at 6 wk of age in 12 infants, and the volumes of RBCs lost by phlebotomy and those gained by transfusion were recorded between the RCV measurements. In six infants, the volume of waste blood on materials contaminated with blood during phlebotomy, which would usually be discarded, was measured by radioactive counting.
Results:
The mean RCV in the first several days of life was 39.6 ml (35.7 ml/kg; range: 20.1-58.7 ml/kg). Of the 12 infants whose RCV was measured twice, all but one had a decrease in absolute RCV. The mean RCV initially and at 6 wk were 37.3 and 26.6 ml, respectively. The mean volume of RBCs lost through phlebotomy was 29.2 ml, and the mean volume of RBCs given by transfusion was 34.5 ml.
Conclusion:
During the first 6 wk of life, when the anemia of prematurity is evolving, the RCV falls despite complete replacement of RBCs lost by diagnostic phlebotomy with transfused RBCs.
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