title: Cerebral blood-flow in polycythaemia.
abstract: Cerebral blood-flow (C.B.F.) has been measured in 16 patients with polycythaemia of differing severity. The mean C.B.F. was 37-9 ml/100 g/min, which is significantly below the normal level of 69-1 (S.D. 9-3) ml/100 g/min (P less than 0-001). C.B.F. measurement was repeated after venesection in 15 of the patients. Lowering the haematocrit from a mean of 0-536 to a mean of 0-455 was associated with a 73% increase in mean C.B.F. (P less than 0-001) and a 30% reduction in whole-blood viscosity. Low C.B.F. was found at haematocrit levels between 0-46 and 0-52. Haematocrit levels that are currently acceptable in the management of polycythaemia may therefore be too high.
mesh_terms: D000368:Aged; D001809:Blood Viscosity; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation; D005260:Female; D006400:Hematocrit; D006801:Humans; D002546:Ischemic Attack, Transient / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D011087:Polycythemia Vera / Q000097:blood / Q000150:complications / Q000503:physiopathology*; D012039:Regional Blood Flow
chemical_list: D002245:Carbon Dioxide