Internal carotid artery blood flow during cerebral angiography

A total of 13 contrast injections of Isopaque Cerebral (meglumine metrizoate) were made into the precerebral arteries or the aortic arch in 6 patients and the bilateral internal carotid artery blood flow monitored continuously using implanted electromagnetic blood flow probes. The most frequent causes of flow changes were found to be due to sudden changes in arterial blood pressure or ventilation which caused a simultaneous and generally identical flow pattern in the two arteries. In 4 patients a slight increase in flow in the artery receiving contrast medium was observed; the increase ranged from 10 to 20% above control level. In one patient the ICA receiving contrast medium showed an initial drop in blood flow to about 85% within 15 sec while the contralateral side showed an increase in flow to about 110%. This sequence was followed by a 6 minute period of slightly increased blood flow on the injection side while the other side showed a slight decrease. A discrepancy in carotid vasomotor response was seen after the injection of 50 ml of contrast medium into the aortic arch with filling of both carotids in the angiogram. Flow changes thought to reflect "arterial spasm" (increased vascular resistance) were observed during attempts to puncture the common carotid artery. The risks connected with this method are discussed. Repeat flow recordings throughout the 24 hours following angiography did not show flow changes attributable to the angiographic investigation.