PubMed · 5827609
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W T Ulmer. 1965-07-17. [Lung function tests in silicosis].. https://pubmed.ncbi.nlm.nih.gov/5827609/
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Knowledge of cerebral metabolic variables increases the information available for managing the head-injured patient. This article reviews normal cerebral metabolism and describes the derangement of metabolism observed in patients with head trauma. Cerebral metabolism is globally decreased by one third to one half in the severely head-injured patient, usually because of the lower metabolic expenditure associated with coma, but sometimes because of superimposed hypoxia/ischemia, primarily due to secondary insults. Measurement of jugular venous oxygen saturation has become the most useful method for monitoring cerebral metabolism in the ICU. Although jugular venous oxygen saturation does not provide quantitative information about either cerebral blood flow or cerebral metabolism, it reflects the ratio between these two variables. To maintain a sufficient level of available oxygen and energy production at the cellular level, there are two therapeutic strategies: a) hemodynamic and b) metabolic. Treatments can be directed at both increasing oxygen delivery and integrating hemodynamic handling, and at various pharmacologic or physical methods intended to reduce the cerebral metabolic demand. The latter strategy is designed to depress either the basal or activation components of cerebral metabolism. This strategy includes manipulations of brain temperature and the use of central nervous system-depressant, barbiturate, and similar drugs.
Transcranial Doppler ultrasonography (TCD) has served a useful purpose in further defining the pathophysiology of disordered cerebrovascular control after head injury. The evaluation of altered cerebrovascular responses in individual patients may be useful in their clinical management. TCD can be a clinically useful tool in the early diagnosis of a variety of complications that can occur in head-injured patients, such as vasospasm, markedly increased intracranial pressure (ICP), low cerebral perfusion pressure, carotid dissection, and disordered cerebral autoregulation. Although the TCD waveforms alone can alert clinicians to the presence of markedly increased intracranial pressure, these waveforms are not specific for predicting moderate ICP increases. Experienced interpreters can identify TCD waveforms that indicate the arrest of the cerebral circulation. Cerebral circulatory arrest can be a useful confirmatory finding in the diagnosis of brain death in questionable cases, and also can be used to shorten the observation period in those patients in whom organ donation is contemplated or discontinuation of ventilatory support and nursing care may be indicated.