Effect of haemodilution on the cerebral blood flow and blood-brain barrier in experimental cerebral oedema in cats

The effect was studied of normovolaemic haemodilution with Dextran 60 to a haematocrit of 25.9 ± 3.5% on the cerebral blood flow and on the blood-brain barrier during experimental oedema produced in cats by the modified method of Ishi, Hayner, Kelly & Evans (1959). The cerebral blood flow was measured by the intracarotid ¹³³Xe method. The extent of disturbances of the blood-brain barrier was evaluated on the basis of extravasation of intravenously administered Evans blue. In the control group, comprising cats which had not been subjected to haemodilution, the cerebral blood flow dropped gradually during epidural compression and was 49% of the control value after 6 h of compression. At the same time, disturbances of the blood-brain barrier were observed in the cortex of the compressed hemisphere and in the subcortical nuclei of both hemispheres. Haemodilution increased the cerebral blood flow by 34% of control value. The decrease in cerebral blood flow during epidural compression produced after haemodilution began later and appeared to be smaller than in the control group. After 6 h of compression the cerebral blood flow fell by only 26% of the control value. In this group of animals the blood-brain barrier in the cerebral cortex of the compressed hemisphere was affected in the immediate neighbourhood of the compression site. It was concluded that haemodilution has a beneficial effect in diminishing the effects of oedema on the brain.