Physiological considerations important for the management of vasospasm.

The physiological mechanisms of known importance in the control of cerebral blood flow (CBF) and smooth muscle contraction and relaxation are reviewed. The pathophysiology of vasospasm following subarachnoid hemorrhage (SAH) is correlated with an alteration of these mechanisms. It is emphasized that smooth muscle relaxation is an energy-dependent process and that vasodilators require a functional smooth muscle membrane that may be severely impaired in ischemia or subarachnoid hemorrhage. The temporal profile of ischemia from spasm is correlated with the pathophysiology of altered metabolism of smooth muscle. The relevance of this complication to the timing of aneurysm surgery in 337 cases operated by one surgeon is considered along with various drug regimens suggested for its management.