Hypotension Prediction Index-guided Hemodynamic Optimization Trial to Reduce Postoperative Acute Kidney Injury (HYT).

MAIN AIM OF THE STUDY To establish whether hemodynamic management guided by the hypotension prediction index (HPI) guided by the administration of intravenous fluids and vasoactive drugs in patients undergoing elective major abdominal surgery reduces the incidence of postoperative moderate-severe acute kidney injury (AKI) in the 30 days after surgery. STUDY DESIGN A low intervention level clinical, blinded, controlled, randomized, multicenter, with daily follow-up of patients until hospital discharge and of postoperative complications and mortality 30 days after surgery will be performed. This is a low-intervention clinical trial comparing standard treatments: * The drugs used in the investigation are licensed. * The drugs are used according to the indications contemplated in the technical data sheet and there are published scientific data on their efficacy and safety. * The complementary diagnostic or follow-up procedures entail a very limited additional risk or burden to the safety of the subjects, which is minimal compared to that of standard clinical practice. STUDY DISEASE Intraoperative hemodynamic monitoring and management in surgical patients undergoing major abdominal surgery. STUDY POPULATION AND TOTAL NUMBER OF PATIENTS The sample of this study consists of patients of both genders, aged over 65 years and/or physical status ASA III or IV, undergoing elective major abdominal surgery (abdominal, urological, gynecological) under general/combined anesthesia (using laparoscopic or open approaches. To detect a 5% absolute reduction (from 10% to 5%) in the primary outcome variable (postoperative AKI up to 30 days) with a sample size ratio of 1%, and an overall type I error rate of 5%, we need 870 patients (435 per arm). Assuming a 10% loss rate, the total amounts to 958 patients, 479 for each group. DURATION OF THE STUDY The total planned duration of the overall study, which includes authorization, recruitment of subjects, and follow-up of subjects until c