Assessment of Global Ischemia

A number of methods have been used to assess global cerebral ischemia after subarachnoid hemorrhage (SAH). During global ischemia, vascular perfusion is reduced and brain cells are hypoxic. This chapter describes two techniques of assessing global ischemia after SAH. The first explains how cerebral vessels can be examined for perfusion status and the second describes how cerebral interstitial fluid can be studied for the signs of cellular hypoxia after SAH. Each technique offers advantages and disadvantages and selection of one over the other depends upon the operator’s choice and availability of instruments.