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

Abstract

SummaryP:," increased so that it is in the range of adult human blood (27 mmHg). In order to compare high and low oxygen affinity blood under conditions of severe respiratory failure, the effects of a high or low PSO were evaluated in two groups of newborn lambs (Pso, 20 mmHg MATERIALS AND METHODS versus 30 mmHg), under conditions of h~poxic hypoxia (Fio2,10%)Twenty-six mixed breed newborn lambs less than 48 h old were and h~~r c a~n i c h~poxia (Fioz, 10% and Fico2, 10%). Data on included in this study. Intramuscular diazepam was used as secardiovascular function, blood gas Parameters, and tissue oxygen-dation (0.2 mg/kg as a loading dose, 0.1 mg/kg repeated at hourly ation were collected under normoxic conditions and during severe intervals). Infiltration of lidocaine 2% provided local anesthesia at h~poxia. During h~poxic h~poxia, a higher arterial oxygen content catheterization site. In an attempt to maintain constant metabolic was noted in the high affinity group throughout the experiment; demands, the animals were curarized with d-tubocurarine (0.2 however, there were no significant differences detected in the mg/kg intravenously), half of this dose being repeated if necessary. remainder of the parameters studied. During hypercapnic hypoxia, They were intubated and mechanically ventilated. Rectal temperthe position of the oxygen dissociation curve did not cause any ature was constantly controlled at 38.5 + 0.2"C. significant differences. When, however, h~perca~nic h~poxia wasPolyethylene catheters were positioned in descending aorta and compared to h~~x i c h~~x i a , there was a significant increase in right atrium. 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 position of the catheters was determined by LV, left ventricle the morphology of the pressure curve. For the right atrium the LVET, left ventricular ejection time catheter was advanced until the appearance of atrial extrasystoles. PEP, pre-ejection periodAt the end of the experiment the position of all catheters were ODC, oxygen dissociation curve confirmed at autopsy. The lambs were divided in four groups, two PVOz, venous oxygen tension of which had their high affmity red blood cells exchanged for low affinity red blood cells (Fig. 1). This was achieved by a two volume exchange transfusion (160 ml/kg) of fresh heparinized Recent studies in our laboratory have shown that a lower mixed adult sheep blood. 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...

Postnatal Changes in Fetal Hemoglobin, Oxygen Affinity and 2,3-Diphosphoglycerate in Previously Transfused Preterm Infants

“…In lambs during severe respiratory failure, lower P5o red cells did not inhibit oxygen delivery [12]. However, under conditions of exercise [13][14][15] or severe anemia [12], the left-shifted P50 does impose a limitation in maintaining tissue oxygen delivery.…”

“…In lambs during severe respiratory failure, lower P5o red cells did not inhibit oxygen delivery [12]. However, under conditions of exercise [13][14][15] or severe anemia [12], the left-shifted P50 does impose a limitation in maintaining tissue oxygen delivery. The leftshifted effect produced by the higher HbF% reported here was small and is unlikely to produce an important impairment in oxygen delivery except under demanding conditions such as severe anemia, sepsis or surgery when the decreased sensitivity of fetal hemoglobin for DPG limits acute shifts in P5o directed at improving oxygen delivery.…”