Patients with decompensated heart failure have high rates of mortality and morbidity despite recent improvements in diagnosis and treatment. Some aspects of their presentation such as renal failure, hyponatremia and congestive phenomena have received special attention, as they are associated with worse prognosis. The infusion of hypertonic saline solution has been tested in different conditions of cardiovascular collapse. Current evidence indicates that the infusion of hypertonic solution in heart failure patients can provide clinical and haemodynamic improvement. The investigators are testing the hypothesis that the infusion of hypertonic solution in association with diuretics may prevent the occurrence of renal dysfunction in patients with decompensated heart failure.