Further studies on the cerebral blood flow estimated with thorium-B-labelled erythrocytes.

Since our first preliminary report (Nylin and Blomer, 1955) we have continued our studies on the cerebral blood flow with radioactive-labelled erythrocytes. The experimental conditions have been the same as before, with the exception that one of us (H. B.) has used a special technique for blood sampling. Blood is drawn simultaneously from both jugular bulbs. In a rotating disc two rows of test tubes are inserted and the disc placed within an exicator, which is evacuated to a fixed pressure. With this arrangement it is possible to fill two test tubes simultaneously at constant time intervals. A somewhat similar apparatus has been constructed by one of us (G. N.), but as it has not been used in observations described in this report, it will be described and published later. The same method as in our first report has been applied for labelling the erythrocytes with thorium B as well as for measuring the activity. Mathematical calculations of the cerebral blood flow have been carried out in the same way as in our first report, but some other relationships have also been computed. Thus, the cardiac output from the dilution curves from the jugular bulbs after intravenous injection of thorium-B-labelled erythrocytes has been estimated. The material is rather heterogeneous. Cases with different clinical diagnoses such as hypertension, cerebral hxmorrhage, and cerebral thrombosis are included as well as normal subjects. It has still not been possible to investigate thoroughly the influence of different clinical conditions on the cerebral blood flow. It is, however, our intention to do this in future studies. The material has been divided into two groups. In Group I (11 cases) injections of thoriumB-labelled erythrocytes in the internal carotid artery have been performed. Simultaneous sampling of blood from both jugular bulbs has been immediately carried out. In Group II (18 cases), after injection of labelled erythrocytes in an arm vein, simultaneous sampling has been effected from both jugular bulbs and one brachial artery.