Oxygenation in Anemic Newborn Lambs with High or Low Oxygen Affinity Red Cells

Abstract

SummaryExperiments to determine the effect of the oxygen-hemoglobin dissociation curve on oxygen delivery during neonatal anemia, were carried out on 15 sedated and ventilated lambs less than 48 hr of age. Eight of the animals were exchange transfused with adult blood. The Pao of the exchange transfused group was 32.1 mm Hg (low Oz affinity) compared to 19.4 mm Hg for the controls (high 0 2 affinity). The animals were made anemic by isovolumic exchange transfusions with plasma. At different levels of hemoglobin defined as mild (8 mg/100 ml), moderate (6 mg/100 ml), and severe (4 mg/100 ml) anemia, tissue oxygenation, hemodynamic status, and blood gases were compared. Mixed venous POz was significantly lower in the high affinity group throughout the study. Cardiac output was significantly greater in the low affinity group during severe anemia. Oxygen consumption remained stable in the low affinity group, but decreased significantly in the high a f f i t y group when the anemia was severe. The data indicate that during severe anemia, blood with a high Po0 is more capable of adequately oxygenating tissues than that with a low PSO. SpeculationEarly preterm newborn infants may not adequately oxygenate their tissues during anemia because of their high oxygen a f f i t y red cells.An important adaptive mechanism during adult anemia is the shift to the right of the oxygen hemoglobin dissociation curve (15). Early preterm newborn infants have red cells with a relatively high oxygen affinity (3) and besides the numerous neonatal complications of prematurity these infants can also have a fall in hemoglobin level. It is apparent that a study was required to determine whether there could be obvious physiologic disadvantages of being anemic during a period of life when red cells have a high affinity for oxygen.In order to answer this question, studies were planned using the newborn lamb, within the first 48 hr of life, as an experimental model. The newborn lamb is born with a Pm which is similar to that of an early preterm newborn infant (18-19 mm Hg) (1) while the Pm of the adult sheep blood is considerably higher (3Ck38 mm Hg) (10). This study was designed to compare at different degrees of anemia, tissue oxygenation, hemodynamic status as well as blood gases in newborn lambs with either high or low oxygen affinity red cells. MATERIALS AND METHODSFifteen newborn lambs less than 48 hr old were included in the study. Eight lambs containing high oxygen affinity red cells were considered as the high 0 2 affiity group and seven lambs who underwent a two volume exchange transfusion (160 ml/kg) using freshly drawn maternal blood made up the low oxygen affiity group. The animals were prepared in conformance with the guiding principles in the care and use of animals as recommended by the Declaration of Helsinki. They were first sedated enough to be kept asleep with repeated subcutaneous injections of Diazepam (0.3 mg/kg every 20-30 min). To eliminate sensibility to pain during catheter position, lidocaine hydrochloride (2%) was used...

Anemia Blunts the Thermogenic Response to Environmental Cold Stress in Newborn Piglets

“…5 g/dl, has been shown to decrease basal oxygen consumption in newborn lambs (5). Similar decreases in oxygen consumption have been demonstrated in adult dogs when the hematocrit was less than 10% (6)(7)(8).…”

Blood Flow and Oxygen Delivery to the Organs of the Neonatal Lamb as a Function of Hematocrit

“…The finding of a decreasing whole body oxygen consumption as hematocrit is decreased is in keeping with our understanding of the relationship between the high metabolic needs of the newborn and its ability to meet these needs under extreme circumstances. Various experimental protocols have been employed to assess the interrelationship between neonatal age and size, hemoglobin type and concentration, and metabolic demand and their impact on whole body oxygen consumption (22). Because each of these factors is rapidly changing in the newborn, it is impossible to derive a single hematocrit or hemoglobin concentration at which oxygen consumption decreases.…”

The Effect of High or Low Oxygen Affinity Red Cells on Tissue Oxygenation and Myocardial Function in Hypoxic Newborn Lambs with or without Hypercapnia

“…In situations of compromised oxygen availability, such as occur in severe red cell mass deficits or poor arterial blood perfusion, a lowered hemoglobin oxygen affinity is of benefit (9,23,26). The changes in oxygen hemoglobin affinity that have been described at moderate altitude remain controversial.…”

“…A Swan-ganz balloon catheter 5F was also placed in cardiac output and myocardial contraction during h~~r c a~n i a . the pulmonary artery as described previously ( 13,26). Stat ham P23Dc transducers provided pressure curves which were registered Abbreviations on a Grass model 7 paper recorder, giving heart rate, systolic, diastolic, and mean pressure values of both systemic and pulmoHbOz, hemoglobin oxygen saturation nary circulations.…”

“…The first series of 12 experiments were carried venous oxygen tension (PVon) in presence of high Oz affinity red out to compare the high and low oxygen affinity groups (six cells occurs in normoxemic newborn lambs and that severe anemic animals in each group, 1A and 1B) when being ventilated with a hypoxia is better tolerated in lambs with low affmity blood gas mixture of 10% On and 90% Nz. Then another series of similar compared to high affinity blood (13,26). A shift of the ODC to experiments were carried out with 14 animals (seven animal in the right is believed to be advantageous at normoxia (13), anemia each group, 2A and 2B) using a gas mixture of 10% 02, 10% Con, (26), and mild hypoxia (1,12,14,18); however, it may be mala-and 80% N2.…”