BLUE is a randomized, multicenter, open-label trial. Patients with high risk of hypotension during RRT will be randomized to receive either methylene blue infusion at a dose of 1 mg/kg as a bolus, followed by continuous infusion of 0.1 mg/kg of body weight in a total of 200 mL of saline solution throughout the dialysis session, or to usual care. The usual care group will not receive any intervention. A total of 260 patients are expected to be randomized in a 1:1 ratio.