TY - JOUR
T1 - Effect of hematocrit on cerebral blood flow with induced polycythemia
AU - Massik, J.
AU - Tang, Y. L.
AU - Hudak, M. L.
AU - Koehler, R. C.
AU - Traystman, R. J.
AU - Jones, M. D.
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 1987
Y1 - 1987
N2 - Cerebral blood flow (CBF) is lowered during polycythemia. Whether this fall is due to an increase in red blood cell concentration (Hct) or to an increase in arterial O2 content (Ca(O2)) is controversial. We examined the independent effects of Hct and Ca(O2) on CBF as Hct was raised from 30 to 55% in anesthetized 1- to 7-day-old sheep. CBF was measured by the radiolabeled microsphere technique before and after isovolemic exchange transfusion with either oxyhemoglobin-containing erythrocytes (in 5 control animals) or with methemoglobin-containing erythrocytes (in 9 experimental animals). Following exchange transfusion in the control animals, Hct rose (30 ± 1 vs. 55 ± 1%, mean ± SE), Ca(O2) increased (15.1 ± 0.8 vs. 26.7 ± 0.9 vol%), and CBF fell (66 ± 9 vs. 35 ± 5 ml·min-1·100 g-1). Because the fall in CBF was proportionate to the rise in Ca(O2), cerebral O2 transport (CBF x Ca(O2)) was unchanged. Following exchange transfusion in the experimental animals, Hct rose (32 ± 1 vs. 55 ± 1%) but Ca(O2) did not change. Nevertheless, CBF still fell (73 ± 4 vs. 48 ± 2 ml·min-1·100 g-1) and, as a result, cerebral O2 transport also fell. The latter cannot be attributed to a fall in cerebral O2 uptake, as cerebral O2 uptake was unaffected during each of these conditions. Comparison of the two groups of animals showed that ~60% of the fall in CBF may be attributed to the increase in red cell concentration alone. It is probable that this effect is due largely to changes in blood viscosity.
AB - Cerebral blood flow (CBF) is lowered during polycythemia. Whether this fall is due to an increase in red blood cell concentration (Hct) or to an increase in arterial O2 content (Ca(O2)) is controversial. We examined the independent effects of Hct and Ca(O2) on CBF as Hct was raised from 30 to 55% in anesthetized 1- to 7-day-old sheep. CBF was measured by the radiolabeled microsphere technique before and after isovolemic exchange transfusion with either oxyhemoglobin-containing erythrocytes (in 5 control animals) or with methemoglobin-containing erythrocytes (in 9 experimental animals). Following exchange transfusion in the control animals, Hct rose (30 ± 1 vs. 55 ± 1%, mean ± SE), Ca(O2) increased (15.1 ± 0.8 vs. 26.7 ± 0.9 vol%), and CBF fell (66 ± 9 vs. 35 ± 5 ml·min-1·100 g-1). Because the fall in CBF was proportionate to the rise in Ca(O2), cerebral O2 transport (CBF x Ca(O2)) was unchanged. Following exchange transfusion in the experimental animals, Hct rose (32 ± 1 vs. 55 ± 1%) but Ca(O2) did not change. Nevertheless, CBF still fell (73 ± 4 vs. 48 ± 2 ml·min-1·100 g-1) and, as a result, cerebral O2 transport also fell. The latter cannot be attributed to a fall in cerebral O2 uptake, as cerebral O2 uptake was unaffected during each of these conditions. Comparison of the two groups of animals showed that ~60% of the fall in CBF may be attributed to the increase in red cell concentration alone. It is probable that this effect is due largely to changes in blood viscosity.
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U2 - 10.1152/jappl.1987.62.3.1090
DO - 10.1152/jappl.1987.62.3.1090
M3 - Article
C2 - 3571067
AN - SCOPUS:0023273790
SN - 8750-7587
VL - 62
SP - 1090
EP - 1096
JO - Journal of applied physiology
JF - Journal of applied physiology
IS - 3
ER -