Cerebral blood flow velocities after subarachnoid haemorrhage in relation to the amount of blood clots in the initial computed tomography.

In 72 patients with acute subarachnoid haemorrhage (SAH) the relationship between the amount of subarachnoid blood clots detected by initial cranial computed tomography (CCT) up to 48 hours after bleeding and the later development of vasospasm, established by blood flow velocity measurement with transcranial Doppler ultrasound (TCD) was investigated. The serial Doppler examinations started within the first 72 hours after SAH and were carried out every second day up to three weeks. Each Doppler recording was accompanied by a neurological examination. Patients classified as Hunt and Hess grade V were excluded from the study. All patients with remarkable brain oedema in CCT or with intracranial pressure above 25 mmHg were also excluded. Because of the well known age-dependence of vasospasm after SAH, two age groups were formed. A statistically significant correlation (p > 0.05) between blood flow velocities and blood load after SAH was not found. The mean age of the investigated 72 individuals was 48.9 years (14 up to 76 years). 47 patients were younger than 56 years. Linear regression analysis indicated a correlation with a quite low significance level (r = 0.350, p < 0.025) between TCD blood flow velocities and blood load in CCT in these younger subjects. No significant correlation (p > 0.05) between these two variables could be established in the 25 patients older than 55 years. In a second step an intra-individual comparison of side-to-side differences in TCD and CCT was made. There were no significant differences in blood flow velocities between subjects with or without side-to-side differences in cisternal blood load. It is concluded that the amount of blood visible on initial CCT after SAH is not a powerful predictor of cerebral blood flow velocities measured by TCD.