Hiponatremia em pacientes com traumatismo cranioencefálico : ausência de alteração sangüínea do peptídeo natriurético cerebral, aldosterona e vasopressina

Abstract

Hiponatremia é comum no paciente neurocirúrgico crítico e está associada a taxas elevadas de morbimortalidade. Dentre as causas de hiponatremia podemos citar a síndrome cerebral perdedora de sal (SCPS) e a síndrome da secreção inapropriada do hormônio antidiurético (SSIHAD). Pacientes com SSIHAD e SCPS possuem manifestações clínicas idênticas, inclusive com as mesmas causas intracerebrais e o diagnóstico diferencial muitas vezes é difícil. A fisiopatologia da SCPS não está clara. Tem sido postulada seqüência de eventos, em que uma substância liberada em resposta a lesão cerebral causaria comprometimento no transporte tubular renal, com resultante diminuição no volume efetivo vascular. _______________________________________________________________________________ ABSTRACT

Objectives. To study any possible relation between hyponatremia following brain injury and the presence of cerebral salt-wasting syndrome (CSWS) or the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), and if vasopressin, brain natriuretic peptide (BNP) and aldosterone have a role in its mechanism. Methods. Patients with brain injury admitted to the intensive care unit were included and had their BNP, aldosterone and vasopressin levels dosed on day 7. Results. Twenty six adult patients were included in the study. Nine (34.6%) had hyponatremia and presented with a negative water balance and higher values of urinary sodium, serum potassium and diuresis than patients with normonatremia. The serum levels of BNP, aldosterone, and vasopressin were normal and no relation was observed between plasma sodium and BNP, aldosterone or vasopressin. Conclusions. The most likely cause of hyponatremia was CSWS and there was no correlation between BNP, aldosterone and vasopressin with serum sodium level.