PEDIATRICS Vol. 75 No. 6 June 1985, pp. 1054-1060
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Circulatory Changes in Newborn Lambs with Experimental Polycythemia: Comparison Between Fetal and Adult Type Blood

Jean-Claude Fouron MD1, Harry Bard MD1, Lise Riopel MSc1, Xavier de Muylder MD1, Marie-Reine Van Ameringen PhD1, and François Urfer MD1

1 The Cardiology and Neonatology Sections, Departments of Pediatrics and Pediatric Research, Sainte-Justine Hospital and University of Montreal, Montreal

Hemodynamic effects of increased hematocrit were compared in two groups of newborn lambs. In the first group (fetal type blood), exchange transfusions were carried out using packed red blood cells obtained from newborn lambs within one to two hours after birth. In the second group (adult type blood), the same procedure was carried out using adult sheep blood. In both groups, hematocrit values ranging between 70% and 80% were reached. The increase in hematocrit caused a decrease in cardiac output due to an increase in peripheral resistance. Pulmonary resistance increased more than systemic resistance. However, the increase in pulmonary resistance was significantly greater in the polycythemic newborn lambs with adult blood. A right-to-left shunt through a patent ductus or a foramen ovale was noted in six of the eight lambs included in this group. On the other hand, none of the seven polycythemic newborn lambs with fetal blood developed signs of right-to-left shunting. It is concluded that during neonatal polycythemia, the level of hematocrit is not the sole factor responsible for the hemodynamic changes observed. Other unknown influences related either to the red cells or the plasma must impinge upon the pulmonary circulation to alter vascular resistance.

Key Words: newborn • polycythemia • pulmonary hypertension • persistent fetal circulation

Submitted on February 27, 1984
Accepted on July 3, 1984