Hypernatraemia in neurosurgical pathology

Hypernatraemia is defined as an increase in extracellular sodium concentrat ion, associated with plasma hyperosmolality and cellular dehydration. It ca n result from excessive water loss, from an increase in the total sodium co ntent or from both mechanisms. As far as neurosurgical pathology is concern ed, hypernatraemia due to excessive water loss may observed in patients who do not sense thirst or are unable to digest water. Urinary water loss is s een in diabetes insipidus and osmotic diuresis. Extrarenal water losses fro m pulmonary origin may be observed in intubated or tracheotomized patients. Hypernatraemia with sodium and water retention may be encountered in patie nts suffering from Cushing diseases or syndromes, or more frequently in tho se who are given excessive amounts of sodium (hypertonic saline, sodium sal ts). Clinical malifestations of hypernatraemia consist of neurologic sympto ms related to cellular dehydration; their severity is correlated with the r apidity of the onset of the electrolytic disorder. Depending on the pathoph ysiological mechanism, treatment of hypernatraemia involves stopping sodium intake, restoring normovolaemia and administering hypotonic fluids. Treatm ent of diabetes insipidus relies on the administration of the antidiuretic hormone and of drugs that increase its secretion rate or its responsiveness in the kidneys. (C) 2001 Editions scientifiques et medicales Elsevier SAS