Arteriovenous differences of oxygen and transcranial Doppler sonography in the management of aneurysmatic subarachnoid hemorrhage

Abstract After subarachnoid hemorrhage (SAH) the detection of hemodynamically significant vasospasm is frequently difficult, especially in comatose patients. Most clinicians use transcranial Doppler sonography (TCD) to detect increasing mean blood flow velocities in the basal arteries as markers of cerebral vasospasm, without accounting for the effects of sedation and variations in blood pressure or pCO2 . This study was conducted to test the hypothesis that the arteriovenous difference of oxygen (avDO2 ; in terms of % volume) could also be useful for the evaluation of vasospasm. A total of 22 SAH patients (M : F = 1 : 1.75, age 58 ± 10 years, median Hunt and Hess grade 4) were prospectively enrolled. All patients were sedated with continuous doses of midazolam/fentanyl and/or propofol. TCD studies and avDO2 measurements were conducted at the same time or in close succession. The blood flow velocity of the middle cerebral artery was recorded. A cranial CT scan was conducted if the avDO2 increased by at least 0.8%. Overall, 82 measurements were recorded in 22 patients between days 1 and 13 after SAH. TCD mean flow velocities increased as expected. In contrast, avDO2 decreased until post-hemorrhage day 4 before it increased again. Overall, after SAH, avDO2 was significantly lower than in normal individuals. Cerebral infarction occurred primarily in patients with a maximal change of avDO2 of more than 1%. TCD velocities alone are poor indicators of the severity of vasospasm. In contrast, daily avDO2 seems to be a more robust parameter. However, collection of additional metabolic information is warranted.