Sodium Chloride and Contrast Nephropathy

This phase II, open, non-inferiority, randomized and controlled clinical trial is aimed to ascertain the incidence of contrast nephropathy in outpatients undergoing CT scan with contrast. Patients will be randomized to receive oral prophylaxis with capsules of sodium chloride and free water ingestion or prophylaxis with sodium chloride 0.9% intravenous solution. In those patients randomly allocated to oral prophylaxis (n=133), patients will receive capsules of sodium chloride and free water ingestion (for each capsule of sodium chloride, patients will take 250 ml of water, assuring a minimum ingestion of 750 ml of water) in the 48 hours prior contrast injection. Patients will take capsules of sodium chloride at a dose of 100 mg/kg during 48 hours previous the injection of contrast (48, 40, 32, 24, 16, and 8 hours), at the moment of contrast injection and 12 hours after the injection of contrast. In those patients randomly allocated to receive sodium chloride 0.9% intravenous solution (n=133), patients will receive at hospital 3 ml/Kg of sodium chloride 0.9%, one hour previous contrast injection and 2 ml/kg during the 4 hours after contrast injection. The total dose (mmol) of sodium chloride will be the same regardless administration via. The contrast will be iodixanol (320 mg of iodine/ml, in 100 ml, at an infusion rate of 2-5 ml/sec). Patients \>65 years, of both sexes, with at least one of the following criteria: diabetes, stable heart failure or chronic kidney disease (estimated glomerular filtration rate between 30 and 60 ml/min), undergoing CT scan with contrast, and who give written informed consent, will be included in the study. Patients with estimated glomerular filtration rate \<30 ml/min, serum potassium \<3.5 mEq/L, infusion of iodine contrast in the previous 15 days, administration of nephrotoxic drugs in the previous 72 hours or expected in the following hours after contrast infusion, decompensated chronic conditions (heart failure, chronic obstructive pulmonary disease, hypertension), allergy to iodine contrast, or the presence of hyperchloremia or hypernatremia, will be excluded from the study. Contrast nephropathy will be defined as the increase of serum creatinine \>0.3 mg/dL from baseline, or the reduction of estimated glomerular filtration rate (MDRD-4) \>25% from baseline, in the first 48 hours after contrast administration.