This prospective randomized trial aims to compare the effects of two intraoperative hemodynamic management strategies on early postoperative renal function in patients undergoing colorectal surgery. Patients will be randomly assigned to receive either mean arterial pressure-guided or cardiac index-guided intraoperative hemodynamic management.

Colorectal surgery is a major abdominal procedure associated with prolonged operative times, significant fluid shifts, blood loss, and hemodynamic instability. These factors can contribute to impaired renal perfusion and subsequent postoperative renal dysfunction. Although mean arterial pressure is widely used to guide intraoperative hemodynamic management, blood pressure alone may not adequately reflect systemic blood flow or regional tissue perfusion. Cardiac index-guided management may provide a more direct assessment of global circulatory adequacy.

The primary outcome of the study is the change in serum creatinine levels from the preoperative baseline to 72 hours postoperatively. Secondary outcomes include intraoperative hemodynamic variables, fluid and vasopressor requirements, urine output, postoperative renal function parameters, intensive care unit (ICU) and hospital length of stay, and 30-day mortality.

Inclusion Criteria:

• Patients aged 18 to 80 years
• Patients with American Society of Anesthesiologists physical status II-III
• Patients with estimated glomerular filtration rate ≥60 mL/min/1.73 m²
• Patients scheduled for colorectal surgery
• Patients who provide written informed consent

Exclusion Criteria:

• Patients younger than 18 years or older than 80 years
• Patients with estimated glomerular filtration rate <60 mL/min/1.73 m²
• Patients with American Society of Anesthesiologists physical status other than II-III
• Patients who refuse to participate in the study
• Patients who withdraw consent at any stage of the study