Metabolic encephalopathies.

Metabolic encephalopathies are common among patients in the critical care unit. Septic, hypoxic-ischaemic, hepatic and uraemic encephalopathies are most frequently seen. They produce global neurological dysfunctions ranging from lethargy or mild confusion to coma. Metabolic encephalopathies must be distinguished from other conditions such as structural brain lesions, infections of the central nervous system or drug reactions. Neurological manifestations are often present in the early stages of systemic illness and may be the first symptom. The severity of encephalopathy generally correlates with that of the systemic illness. Appropriate investigations often include drug and metabolic screens, cultures of blood and cerebrospinal fluids and neuro-imaging studies. Electroencephalogram is useful to grade the severity of encephalopathy. With some exceptions such as hypoxic-ischaemic encephalopathy, most metabolic encephalopathies are reversible unless secondary complications such as brain herniation occurred. Treatment is generally that of the underlying systemic illness and supportive measures.