Hyponatraemia in neuro-intensive care: cerebral salt wasting syndrome and inappropriate ADH secretion.

Hyponatraemia is a frequent complication in neurologically injured patients ; if is a secondary cerebral injury. Hyponatraemia leads to consciousness p roblems, convulsions, worsening of the neurological status and thus the neu rological evaluation. Hyponatraemia is secondary to free water retention (i nappropriate ADH secretion) or to renal salt loss. The cerebral salt wastin g syndrome (CSWS) has been described with head injury, subarachnoid haemorr hage and after several sorts of brain insults. It is characterised by an in creased natriuresis and diuresis. Diagnosis is based on hyponatraemia, hype rnatriuresis, increased diuresis and hypovolaemia. However, inappropriate A DH secretion and CSWS share several diagnostic criteria. The atrial natriur etic factor and the C-type natriuretic factors play a role in the developme nt of the CSWS. The diagnostic approach and monitoring are based on the ass essment of sodium and water losses. Therapy is based on correction of the c irculating volume and natraemia. Speed of correction is a matter of debate: slow correction presents the risk of further neurological injury whereas r apid correction presents the risk of central pontine myelinosis. (C) 2001 E ditions scientifiques et medicales Elsevier SAS.