Journal of Applied Physiology, Vol 62, Issue 3 1090-1096, Copyright © 1987 by American Physiological Society

ARTICLES

Effect of hematocrit on cerebral blood flow with induced polycythemia

J. Massik, Y. L. Tang, M. L. Hudak, R. C. Koehler, R. J. Traystman and M. D. Jones Jr

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 (Cao2) is controversial. We examined the independent effects of Hct and Cao2 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), Cao2 increased (15.1 +/- 0.8 vs. 26.7 +/- 0.9 vol%), and CBF fell (66 +/- 9 vs. 35 +/- 5 ml X min-1 X 100 g-1). Because the fall in CBF was proportionate to the rise in Cao2, cerebral O2 transport (CBF X Cao2) was unchanged. Following exchange transfusion in the experimental animals, Hct rose (32 +/- 1 vs. 55 +/- 1%) but Cao2 did not change. Nevertheless, CBF still fell (73 +/- 4 vs. 48 +/- 2 ml X min-1 X 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 approximately 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.

This article has been cited by other articles:

				L. J Norcliffe, M Rivera-Ch, V. E Claydon, J. P Moore, F Leon-Velarde, O Appenzeller, and R Hainsworth Cerebrovascular responses to hypoxia and hypocapnia in high-altitude dwellers J. Physiol., July 1, 2005; 566(1): 287 - 294. [Abstract] [Full Text] [PDF]

				K. K. Oguz, X. Golay, F. B. Pizzini, C. A. Freer, N. Winrow, R. Ichord, J. F. Casella, P. C. M. van Zijl, and E. R. Melhem Sickle Cell Disease: Continuous Arterial Spin-labeling Perfusion MR Imaging in Children Radiology, May 1, 2003; 227(2): 567 - 574. [Abstract] [Full Text] [PDF]

				J. L. Spivak Polycythemia vera: myths, mechanisms, and management Blood, December 15, 2002; 100(13): 4272 - 4290. [Full Text] [PDF]

				D. M. Eckmann, S. Bowers, M. Stecker, and A. T. Cheung Hematocrit, Volume Expander, Temperature, and Shear Rate Effects on Blood Viscosity Anesth. Analg., September 1, 2000; 91(3): 539 - 545. [Abstract] [Full Text] [PDF]

				Y. Tomiyama, J. E. Brian Jr, M. M. Todd, and W. Pearce Cerebral Blood Flow During Hemodilution and Hypoxia in Rats : Role of ATP-Sensitive Potassium Channels • Editorial Comment: Role of ATP-Sensitive Potassium Channels Stroke, September 1, 1999; 30(9): 1942 - 1948. [Abstract] [Full Text] [PDF]

				Y. Tomiyama, K. Jansen, J. E. Brian Jr., and M. M. Todd Hemodilution, cerebral O2 delivery, and cerebral blood flow: a study using hyperbaric oxygenation Am J Physiol Heart Circ Physiol, April 1, 1999; 276(4): H1190 - H1196. [Abstract] [Full Text] [PDF]

				G Teyssier, J C Fouron, S E Sonesson, P Bonnin, and A Skoll Circulatory changes induced by isovolumic increase in red cell mass in fetal lambs Arch. Dis. Child. Fetal Neonatal Ed., November 1, 1998; 79(3): 180F - 184. [Abstract] [Full Text]