ObjectiveTo review the scientific basis for sedation of critically ill neurologic patients by summarizing the distinct neurophysiologic disturbances present in this population and presenting the central nervous system effects of sedative agents to permit optimal drug therapy.Data SourcesReview of the English language clinical and scientific literature using MEDline data search.Study SelectionLiterature references were selected through a key word search of sedative therapy, drugs used for sedation, and specific neurologic disorders and processes to provide an in-depth overview of sedative drug mechanisms of action, effects on neurophysiology and intracranial dynamics, pharmacokinetics, and toxicity profile. Special emphasis was placed on neurologic side effects.Data ExtractionClinical and scientific literature was reviewed and data relevant to neurophysiologic effects of sedative drug therapy were summarized. Recommendations for institution of sedative therapy and of particular agents were made as a result of analysis of all pooled data.Data SynthesisCritically ill patients with neurologic pathology present as a unique subset of individuals cared for in an acute care setting. Because monitoring of neurologic patients requires frequent assessment of the neurologic examination, the goal of sedative therapy should be to enhance, or to minimally perturb elicitation of the examination. Neurophysiologic disturbances introduce distinct risks for sedation and require their identification and understanding before the initiation of any sedative therapy. Sedative drugs, in particular, act to disturb central nervous system function and their effects may result in diagnostic confusion and further neurologic deterioration. The pharmacokinetic and neurophysiologic actions of the common classes of sedative agents, such as benzodiazepines, opioids, barbiturates, and neuroleptics, as well as ketamine, propofol, and clonidine are discussed. Recommendations are presented based on the specific type of sedation required and the underlying neurologic disturbance. Several specific examples, including head trauma, neuromuscular disease, and alcohol withdrawal, are provided.ConclusionsPreservation of the neurologic examination is paramount in documenting clinical improvement or deterioration in the critically ill neurologic patient. Pharmacologic sedation in this unique population of acute care patients requires careful consideration of the underlying neurophysiologic disturbances and potential adverse effects introduced by sedative drugs.(Crit Care Med 1995; 23:2038-2053)