Quantitative Measurement of Cerebral Blood Flow and Cerebral Blood Volume after Cerebral Ischaemia

CBF obtained by the hydrogen clearance technique and cerebral blood volume (CBV) calculated from the [¹⁴C]dextran space were measured in three groups of rats subjected to temporary four-vessel occlusion to produce 15 min of ischaemia, followed by 60 min of reperfusion. In the control animals, mean CBF was 93 ± 6 ml 100 g⁻¹ min⁻¹, which fell to 5.5 ± 0.5 ml 100 g⁻¹ min⁻¹ during ischaemia. There was a marked early postischaemic hyperaemia (262 ± 18 ml 100g⁻¹ min⁻¹), but 1 h after the onset of ischaemia, there was a significant hypoperfusion (51 ± 3 ml 100 g⁻¹ min⁻¹). Mean cortical dextran space was 1.58 ± 0.09 ml 100 g⁻¹ prior to ischaemia. Early in reperfusion there was a significant increase in CBV (1.85 ± 0.24 ml 100 g⁻¹) with a decrease during the period of hypoperfusion (1.33 ± 0.03 ml 100 g⁻¹). Therefore, following a period of temporary ischaemia, there are commensurate changes in CBF and CBV, and alterations in the permeability–surface area product at this time may be due to variations in surface area and not necessarily permeability.