Blood Volume Changes during the First Week after Birth in the Beagle and Pig

Abstract

Summary

During the first week of postnatal life, there were significant changes in red cell volume, plasma volume, and venous and circulatory hematocrits in both the beagle and the pig. In beagle pups the mean red cell volume decreased between 2.5 and 8.5 hr after birth, then increased at 16.5 hr, with a further increase on day 1. Between days 2 and 7, red cell volume decreased. There was evidence of a release of red cells into the circulation from red cell reservoirs. In the newborn pig, red cell volume decreased between days 0 and 2, but was not significantly different on day 7 from day 2. In the beagle the mean plasma volume did not change during the first 12 hr following birth; it increased between 12 and 24 hr after birth and remained unchanged through day 7. In the pig, plasma volume decreased between day 0 and day 1, increased on day 2, and was not significantly different on day 7 from day 2. The increase in plasma volume was the result of an increase in plasma protein, which caused a redistribution of fluid among the various fluid compartments. In the beagle, blood volume decreased between 2.5 hr and 8.5 hr, increased at 16.5 hr with a further increase on day 1, then decreased on day 2, with no further change on day 7. The blood volume in the pig decreased progressively between day 0 and day 7. The changes in venous and circulatory hematocrits for both the beagle and pig reflected those of red cell and plasma volumes throughout the first week of life. The BVR_cells did not change significantly, indicating that there was no shift in the distribution of red cells and plasma in the circulation over this 7-day period.