The adaptation of neonatal blood to metabolic acidosis and its effect on cisternal oxygen tension.
In eight newborn lambs, the adaption of blood to acidosis was studied by sequential measurements of P50 in vitro (pH 7.4; 37 degrees C) and P50 in vivo (animal's pH and temperature, 39 degrees C) during the course of HCl-induced metabolic acidosis. The benefit of the change in both P50 on tissue oxygen tension was studied by the change in O2 partial pressure at the level of the cisterna magna. Eight hr of acidosis caused a significant (P less than 0.01) decrease in P50 in vitro which fell from 29.0 to 24.4 torr. Nonetheless, because of pH effect on the hemoglobin affinity, the corresponding P50 in vivo was increased from 32.4 to 36.3 torr. This latter rise in the in vivo O2 affinity contributed to increase (P less than 0.01) the cisternal O2 tension. It is concluded that the hemoglobin of the newborn is capable of adaption to metabolic acidosis by displacing the in vivo O2 dissociation curve to the right favouring a greater unloading of O2 at the tissue level and thus preventing tissue hypoxia during metabolic acidosis.
D000138:Acidosis / Q000097:blood*; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D002946:Cisterna Magna / Q000378:metabolism*; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D012756:Sheep
D010100:Oxygen