Abstract: ObjectiveTo examined how autoregulation is affected by vasospasm after subarachnoid hemorrhage (SAH) by using transcranial Doppler. MethodsThe moving correlation coefficient between slow changes of arterial blood pressure and mean or systolic flow velocity (FV), termed Mx and Sx, respectively, was used to characterize cerebral autoregulation. Vasospasm was declared when the mean FV increased to more than 120 cm/s and the Lindegaard ratio was more than 3. This occurred in 15 of 32 SAH patients.On the basis of the bilateral transcranial Doppler recordings of the middle cerebral artery in vasospastic patients, Mx and Sx were calculated for baseline and vasospasm. ResultsMx increased during vasospasm (0.46±0.32) and was significantly higher (P=0.03) than at baseline (0.21±0.24) Sx was also increased (0.22±0.26 vs 0.05±0.21,P=0.03). Mx correlated with mean FV (P=0.577, P=0.006) and the Lindegaard ratio (r=0.672,P<0.01).Mx(P=0.006) and Sx (P=0.044) were higher on the vasospastic side compared with the contralateral side.ConclusionThe increased Mx and Sx during cerebral vasospasm demonstrate impaired cerebral autoregulation. Mx and Sx provide additional information on changes in autoregulation in SAH patients.

Key words: cerebral blood flow, autoregulation, subarachnoid hemorrhage (SAH)