Relationships between delayed ischemic dysfunctions and intracranial hemodynamics following subarachnoid hemorrhage

Delayed ischemic dysfunctions (DID) are one of the main complications following subarachnoid hemorrhage. It was the aim of our study to analyse the possible prognostic value of different transcranial Doppler ultrasonography parameters and to elucidate the risk of developing DID with particular reference to the intracranial pressure. The relative change of mean blood flow velocity and of corresponding cerebral circulatory resistance index as well as the intracranial pressure were determined in 44 patients with spontaneous subarachnoid hemorrhage. No relationship was found between the occurrence and extent of DID and the relative change of mean flow velocity during the clinical course. In contrast, there was a significant correlation between the relative change of the cerebral circulatory resistance index and the occurrence of DID. While patients without or with reversible DID showed a decreased resistance index compared to the initial value (without DID: -17% +/- 15%; reversible DID: -3% +/- 14%), patients with irreversible DID had a significant increase of the resistance index (+14% +/- 9%). Accordingly, patients with irreversible DID showed a significant increase of intracranial pressure compared to the patients with reversible DID. We conclude that the evaluation of relative changes of the cerebral circulatory resistance index by bedside monitoring is a useful tool to predict the occurrence of subarachnoid hemorrhage-associated DID and has therapeutic impact.