An Experimental Study on the Changes of Regional Cerebral Blood Flow and the Effect of Calcium Antagonist in Acute Subarachnoid Hemorrhage

ABSTRACT

The present study was performed to elucidate the changes of regional cerebral blood flow(rCBF) and the effect of nifedipine, a calcium antagonist, on rCBF in acute subarachnoid hemorrhage(SAH) in cats. Another Purpose of this study was to document the effective dose and route of administration of nifedipine for maintaining rCBF in acute SAH. Subarachnoid hemorrhage was induced by intrathecal injection of autologous blood in 12 cats and rCBF was measured on the territories of both PCA, MCA, ACA, every 30 minutes for three hours using hydrogen clearance method. Sham operation was done in 5 cats. To study the effectiveness of nifedipine, nifedipine was administered after the induction of SAH in three different methods in 20 catsintravenous injection in the amount of 0.1mg/kg in 7 cats, intravenous injection in the amount of 0.5mg/kg in 7 cats, and intrathecal adminstration of 10(-3)M, 1 ml, in 6 cats. The results were as follows; 1) Cerebral blood flows before the subarachnoid hemorrhage were 40.3+/-4.4ml/min/100g, 41.9+/-9.4ml/min/100g, 39.0+/-5.7ml/min/100g on the territories of right PCA, MCA, ACA and 41.5+/-7.4ml/min/100g, 42.5+/-9.6ml/min/100g, 41.3+/-9.9ml/min/100g on the territories of left PCA, MCA, ACA respectively. There was no significant difference between the territories. 2) After the subarachnoid hemorrhage, the cerebral blood flow was reduced immediately by 23.4-35.8% of control values and remained low for 3 hours in all six territories. 3) The rCBF in the group of intravenous injection of nifedipine in the amount of 0.1mg/kg was not significantly reduced immediately after SAH(p>0.05), but reduced after 3 hours(p0.01), but those in ACA territories were reduced to 60.4% and 61.7% of control values respectively. 6) Blood pressure was elevated from 135.4+/-20.2mmHg to 148.3+/-22.9mmHg at 30 minutes and then dropped to control level in SAH group. Groups of intrathecal administration of 10(-3)M and intravenous injection of 0.1mg/kg showed no significant change but group of intravenous injection of 0.5mg/kg showed significant drop of blood pressure. Intracranial pressure was elevated after SAH but returned to control value in 30 minutes. Intracranial pressure in the intrathecal injection group was markedly elevated and remained high for 3 hours. In conclusion, the rCBF was reduced immediately and remained low for 3 hours after SAH. Intravenous injection of nifedipine in the amount of 0.1ml/kg effective on increasing the reduced cereral blood flow. Intravenous injection of nifedipine in the concentration of 0.5mg/kg was less effective and showed significant hypotension. The effect of intrathecal administration of nifedipine was varied according to the location.