Pre- and post-operative cerebral blood flow changes in subarachnoid haemorrhage

Assessment of cerebral perfusion on patients with subarachnoid haemorrhage (SAH) in the Neurologic Intensive Care Unit is difficult since nuclear medicine imaging modalities capable of measuring cerebral blood flow (CBF) are not generally available. We performed 101 quantitative (ml 100g-min) bedside CBF measurements on 40 individual patients to correlate SAH grade with CBF and to assess the effect of surgical intervention on CBF. Global CBF (G-CBF) and bihemispheric CBF (B-CBF) asymmetry were correlated with the grade of SAH pre- and post-operatively. Data analysis showed that pre-operative patients with low grade SAH (Hunt and Hess grades 0 to 2) had higher mean G-CBF values [44.2 +/- 71] than those with high grade SAH (Hunt and Hess grades 3 to 4): [mean G-CBF = 34.1 +/- 1.7]. Post-surgery there was a significant improvement in G-CBF; CBF increased [5.3 +/- 1.07] in the group of patients with low grade SAH. Patients with high grade SAH showed no significant improvement in their G-CBF during the first week post-operatively compared to pre-operative values. We conclude that portable units capable of measuring bedside CBF values are useful in monitoring CBF changes in patients with SAH. Patients with low grade SAH have G-CBF within normal limits both pre-operatively and post-operatively, with a statistically significant increase in CBF during two weeks post-operatively. Patients with high grade SAH show no significant increase in CBF one week post-operatively compared to their pre-operative measures.