Intensive Care Evaluation of the Comatose Patient

Abstract

Publisher Summary This chapter describes the intensive care evaluation of a comatose patient. Coma is a frequent and major concern in the intensive care unit. Coma results from a physiologic failure of either both cerebral hemispheres or the reticular activating formation of the brain stem; the latter projects to the cortex and serves to maintain consciousness. There are essentially four general pathophysiological causes of coma—(1) supratentorial mass lesions; (2) infratentorial mass or destructive lesions; (3) metabolic encephalopathy and diffuse cerebral disturbances; and (4) psychogenic coma. The first two produce coma by altering the brain stem reticular formation. Supratentorial mass lesions affect the brain stem in one of the two fashions, uncal or central herniation. In the former, the lateral displacement of the temporal lobe over the tentorial edge compresses the midbrain. Initially, there is a third nerve palsy on the side of the lesion with ptosis and pupillary dilatation preceding ophthalmoplegia. The alteration of consciousness then follows and either contralateral hemiplegia or ipsilateral hemiplegia appears. The chapter presents a detailed bedside examination of a comatose individual with an emphasis on possible etiologies. It also discusses the pathophysiology and prognosis of coma.