Effect of Colchicine on the Risk of Perioperative Acute Kidney Injury: Clinical Protocol of a Substudy of the Colchicine for the Prevention of Perioperative Atrial Fibrillation Randomized Clinical Trial

Background: Inflammation during and after surgery can lead to organ damage including acute kidney injury. Colchicine, an established inexpensive anti-inflammatory medication, may help to protect the organs from pro-inflammatory damage. This protocol describes a kidney substudy of the colchicine for the prevention of perioperative atrial fibrillation (COP-AF) study, which is testing the effect of colchicine versus placebo on the risk of atrial fibrillation and myocardial injury among patients undergoing thoracic surgery. Objective: Our kidney substudy of COP-AF will determine whether colchicine reduces the risk of perioperative acute kidney injury compared with a placebo. We will also examine whether colchicine has a larger absolute benefit in patients with pre-existing chronic kidney disease, the most prominent risk factor for acute kidney injury. Design and Setting: Randomized, superiority clinical trial conducted in 40 centers in 11 countries from 2018 to 2023. Patients: Patients (~3200) aged 55 years and older having major thoracic surgery. Intervention: Patients are randomized 1:1 to receive oral colchicine (0.5 mg tablet) or a matching placebo, given twice daily starting 2 to 4 hours before surgery for a total of 10 days. Patients, health care providers, data collectors, and outcome adjudicators will be blinded to the randomized treatment allocation. Methods: Serum creatinine concentrations will be measured before surgery and on postoperative days 1, 2, and 3 (or until hospital discharge). The primary outcome of the substudy is perioperative acute kidney injury, defined as an increase (from the prerandomization value) in serum creatinine concentration of either ≥26.5 μmol/L (≥0.3 mg/dL) within 48 hours of surgery or ≥50% within 7 days of surgery. The primary analysis (intention-to-treat) will examine the relative risk of acute kidney injury in patients allocated to receive colchicine versus placebo. We will repeat the primary analysis using alternative definitions of acute kidney injury and examine effect modification by pre-existing chronic kidney disease, defined as a prerandomization estimated glomerular filtration rate (eGFR) <60 mL/min per 1.73 m². Limitations: The substudy will be underpowered to detect small effects on more severe forms of acute kidney injury treated with dialysis. Results: Substudy results will be reported in 2024. Conclusions: This substudy will estimate the effect of colchicine on the risk of perioperative acute kidney injury in older adults undergoing major thoracic surgery.