Oxygen affinity of haemoglobin modulates cerebral blood flow in premature infants. A study with the non-invasive xenon-133 method.
Low cerebral blood flow (CBF) is thought to cause ischaemic brain lesions in premature infants, but a normal outcome has also been observed. Low oxygen affinity of haemoglobin and high arterial oxygen content, independently, reduce CBF under normal, physiological conditions. Transfusions lower the amount of fetal haemoglobin [HbF] and therefore the oxygen affinity of premature babies. In 47 premature babies (range of gestational age 25-34 weeks, birthweight 740-1370 g), CBF was measured with the i.v. Xenon 133 method on days 1, 3 and 7. The relative amount of fetal haemoglobin [HbF] was used as a marker of oxygen affinity of haemoglobin and the haematocrit as representing the arterial oxygen content. A significant influence of [HbF] on CBF was found on days 1, 3 and 7 in ultrasonographically normal babies (n = 13). In babies with subependymal and/or intraventricular haemorrhage (n = 15), this correlation was significant only on day 3 and in those with abnormal intraparenchymal echodensities (n = 19) only on day 7. The correlation between haemoglobin concentration and CBF was not significant. Multiple regression analysis showed a significant influence of [HbF] on CBF independent of haematocrit, pCO2 and blood pressure. It appears that, after blood transfusion, normal babies, and to a lesser extent those with haemorrhages are able to lower their CBF according to the actual oxygen affinity of blood. However, low CBF (less than 10 ml/100 g/min) in non-transfused babies was often associated with later development of cystic periventricular leukomalacia.)
Lipp-Zwahlen
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AE
Division of Neonatology, University Children's Hospital, Zürich, Switzerland.
Müller
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A
Tuchschmid
P
P
Duc
G
G
D001784:Blood Gas Analysis; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005319:Fetal Hemoglobin / Q000032:analysis*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D014463:Ultrasonography; D014980:Xenon Radioisotopes
D014980:Xenon Radioisotopes; D005319:Fetal Hemoglobin; D010100:Oxygen