Sequential Changes in the Autoregulation of Cerebral Blood Flow in Patient with Vasospasm

Abstract

Sequential changes in the autoregulation of cerebral blood flow (CBF) were studied in 12 pa. tients having subarachnoid hemorrhages (SAH) with symptomatic vasospasms. These patients underwent aneurysmal clipping in the acute stage. An autoregulation curve was prepared from %CBF calculated from the arteriovenous oxygen difference and the mean arterial blood pressure. Dopamine was infused to increase blood pressure, while trimethaphan was used to decrease blooc pressure. Autoregulation curves in the patients with vasospasms were classified into four stages. Stage I : Autoregulation of CBF completely disappeared and the relationship between CBF anc blood pressure was linear. This stage was noted about 6 days after the SAH. Stage II : This patterr was noticed 11 days or so after the SAH. The increase in CBF due to the rise of blood pressure steep ly declined at hypertensive levels. Stage III: Constant CBF appeared at hypertensive levels about 11 days after the SAH. Stage IV: Normalization of autoregulation was noted more than 26 days after the SAH. From these results, induced hypertensive and hypervolemic therapy through the use of plasma expander and dopamine was thought to be effective in stage I and stage II. In stage III hypervolemic therapy and a decrease of intracranial pressure were thought to be the most suitable. In stage IV, hypertensive therapy was thought to be contraindicated. The reason for disturbec autoregulation was unknown, but changes in the vascular wall, denervation around the cerebra: vessels and increased intracranial pressure due to ischemia were all suspected as causes.