EFFECTS OF BLOOD DONATION ON CEREBRAL BLOOD-FLOW VELOCITY

Eighteen healthy male blood donors, nine with hematocrit (Hct) of 0.40 to 0.45 (normal Hct) and nine with Hct of 0.49 to 0.52 (upper‐limit Hct), were monitored by continuous‐wave internal carotid Doppler sonography and hematologic tests for 28 days after blood donation, to ascertain whether and to what extent a single standard donation may modify the velocity of cerebral blood flow. The two groups had similar mean predonation values of internal carotid flow velocity (ICFV): blood donation was followed in both groups by a slight, transient decrease of ICFV at the end of phlebotomy, due to donation‐induced hypovolemia, and then by an increase of ICFV lasting 7 to 10 days. Analysis of individual profiles revealed that only four of nine upper‐limit and six of nine normal Hct donors displayed a positive trend (increase) in the ICFV within the first week after donation, and that it was due mainly to a rise in systolic flow velocity. Mean Hct and arterial oxygen content showed a negative trend (decrease) within the first week that was opposite to the ICFV trend. Other laboratory variables, including serum proteins and plasma fibrinogen concentration, and the iron status indicators did not change, except for serum ferritin, which also decreased within the first week after phlebotomy. It can be concluded that blood donation may result in a short‐term increase of blood flow velocity that is independent of Hct predonation levels in approximately one‐half of the donors. 1990 AABB