Metabolic effects of poisoning

Biochemical and metabolic abnormalities commonly arise in any critically ill patient and in poisoning as a result of an effect of the poison on a particular metabolic pathway or due to poison-induced organ dysfunction. The management of biochemical abnormalities is an essential part of the supportive care of severely poisoned patients, and may be of diagnostic or prognostic value. Acid–base abnormalities are common in severely poisoned patients, particularly metabolic acidosis, which may be a major clinical effect of the overdose. Respiratory acidosis and alkalosis can also arise, commonly due to central stimulation or depression of ventilation. Abnormalities of the plasma potassium concentration are also common, due to the effect of drugs on the intra/extracellular redistribution of potassium. Plasma sodium abnormalities are less common, with hyponatraemia due to a drug-induced inappropriate antidiuretic syndrome being seen more often than hypernatraemia in salt poisoning. Hypoglycaemia should always raise the possibility that a drug is responsible.