Neurologic complications of critical illness: part I. Altered states of consciousness and metabolic encephalopathies.

OBJECTIVE To review the metabolic encephalopathies and neuromuscular abnormalities commonly found in the critically ill patient in a two-part presentation. DATA SOURCES A review of articles reported from 1980 to 2002 and identified through a MEDLINE search on metabolic encephalopathy, polyneuropathy and myopathy in critical illness. SUMMARY OF REVIEW An alteration in the conscious state can be caused by space occupying lesions or infections of the central nervous system. However, in the critically ill patient a metabolic encephalopathy is often the cause of an acute confusional state or a reduced state of consciousness. There is no specific treatment for the metabolic encephalopathies as they commonly resolve when the underlying disorders (e.g. sepsis, renal failure, hepatic failure, electrolyte disturbance) are corrected. Management may also require judicious pharmacological and/or physical restraint in the case of the acute confusional states and ensuring an adequate airway, ventilation and circulation in the case of a reduced state of consciousness, while the underlying disorder is corrected and the encephalopathy resolves. CONCLUSIONS In the critically ill patient a metabolic encephalopathy is commonly the cause of confusion, disorientation, agitation, drowsiness or coma. Sedative agents and tranquilisers may be required as well as management of the airway, ventilation and circulation while the underlying disorder is corrected to allow the encephalopathy to resolve.