Critical care monitoring for cerebrovascular disease.

Frequent or continuous monitoring of crucial variables in patients with cerebrovascular disease allows the intensive care team to identify progression of the pathophysiologic mechanisms involved, intervene to halt or reverse this progression, and identify the response to treatment in order to modify the intervention if necessary. Central nervous system physiologic monitoring modalities include: a) the clinically-apparent function, b) physical and mechanical variables, c) circulation or perfusion, d) bioelectrical measures, and e) biochemical measures. The neurologic examination of the critically ill patient is an indispensable monitoring tool in the ICU. Patterns of neurologic signs and the trend of the examination, whether worsening or improving, are the most important factors to follow because there is no single sign or symptom which forecasts impending disaster. Intracranial pressure monitoring is applicable to all subsets of cerebrovascular disease, providing information about cerebral perfusion pressure and risk of secondary cerebral injury. Cerebral blood flow is not easily quantified in the ICU, but transcranial Doppler sonography is a reliable bedside technique that can be used for intermittent or continuous monitoring. Neurophysiologic monitoring with electroencephalography (EEG) and evoked potential (EP) testing can be used as a supplement to the neurologic exam and other diagnostic studies. EEG and EP can provide an early indication of clinically relevant change due to evolving disease or in response to therapy, which is especially helpful when the neurologic examination is limited due to severe coma, therapeutic barbiturate coma, or neuromuscular blockade. Neurometabolic monitoring in cerebrovascular disease with microdialysis is a promising technique that may be able to identify markers of cellular energy state or excitotoxicity in carefully selected areas of the brain.