Neurological aspects of electrolyte disorders.

Electrolyte disorders are common in clinical practice and can occur as a consequence of primary neurological disease or as a complication of general medical disorders or critical illness. They may affect fluid shifts, cause disordered transmembrane potential or disrupt neurotransmission. Disorders of sodium, potassium, calcium, phosphate and magnesium metabolism are associated with a range of neurological complications that cause neuromuscular and central neurological disturbance. It is important to distinguish between acute and chronic hyponatraemia because prevention of long-term complications depends on appropriate management. Acute hyponatraemia can rarely cause cerebral oedema, seizures or encephalopathy. Potassium metabolism disorders are associated with cardiac and neuromuscular abnormalities. Calcium derangement can give neurological manifestations that range from mild and non-specific symptoms to encephalopathy. Phosphate and magnesium disturbances are particularly associated with neuromuscular weakness and are important causes of respiratory impairment and failure to wean from ventilatory support in critically ill patients.