The effect of vasospasm on cerebral perfusion: a colour duplex study of the extra- and intracranial cerebral arteries.

To assess whether middle cerebral artery (MCA) vasospasm reduces the flow volume in the corresponding extracranial internal carotid artery (ICA) or global cerebral blood flow volume (CBFV) in subarachnoid haemorrhage (SAH) patients, a colour duplex ultrasound study of the intra- and extracranial cerebral arteries was performed. MCA vasospasm was defined as a time-averaged maximum flow velocity (TAMX) exceeding 120 cm/s. ICA flow volumes and CBFV, were compared in each patient at maximum TAMX recorded in one MCA ("maximum-vasospasm") and when TAMX in the same vessel was closest to mean reference values ("no-vasospasm"). Additionally, the CBFV course during the first 3 weeks after SAH was evaluated longitudinally. Data from age- and gender-matched healthy test persons served as control. In 28 patients with MCA vasospasm, 337 measurements were completed. Global CBFV was significantly reduced starting from day 3 after SAH. ICA flow volumes and CBFV were not different when comparing at "maximum-vasospasm" and "no-vasospasm". Compared with the control group, both were lower at either condition. Thus, in SAH patients, vasospasm even severe, in general does not further diminish ICA flow volumes and global CBFV, which are reduced already before the onset of vasospasm.

Volume measurement of cerebral blood flow: assessment of cerebral circulatory arrest.

BACKGROUND: Cerebral blood flow (CBF) volume can be measured at bedside by color duplex flowmetry of the extracranial cerebral arteries. In neurointensive care patients, we prospectively tested the hypothesis that a CBF volume <100 ml/min indicates imminent cerebral circulatory arrest. METHODS: CBF volume was determined as sum of flow volumes in the internal carotid and vertebral arteries of both sides. In 192 neurointensive care patients, 829 measurements were taken. When CBF volume fell short of 100 ml/min, common carotid and external carotid artery flow volumes were also measured, and transcranial color-coded duplex sonography (TCCD) of basal cerebral arteries was performed. Results were compared with actual clinical conditions, outcome, and previously published reference data. RESULTS: All 41 patients with CBF volume <100 ml/min (range, 0-89 ml/min) were officially declared brain dead 2-126 hours after the measurement (median, 23 hours). TCCD revealed signs of cerebral circulatory arrest in all patients with a patent acoustic bone window. External carotid artery flow volumes were normal. The lowest CBF volume rate recorded in a surviving patient was 208 ml/min. CONCLUSIONS: Early confirmation of cerebral circulatory arrest is of decisive importance if the patient is a potential organ donor. CBF volume measurement allows confirming the arrest of cerebral circulation even in patients without a patent acoustic bone window for TCCD. Because the critical lower threshold for survival appears to lie at 200 ml/min, bedside monitoring of CBF volume in neurointensive care patients may indicate a therapeutic window before irreversible circulatory arrest occurs.