MINS

The goal of this observational study is to learn whether metabolic inflexibility, which means reduced ability of the body to switch between using fats and sugars for energy, is associated with myocardial injury after non-cardiac surgery (MINS) in adults undergoing major elective abdominal cancer surgery. The main question it aims to answer is: Does pre-operative metabolic inflexibility predict myocardial injury after non-cardiac surgery (MINS) within the first 72 hours after surgery? Participants will continue with their usual surgical care and pre-planned CPET (which can measure metabolic flexibility). As part of the study, participants will: * Have additional blood samples taken before and after surgery * Have an echocardiogram and, where possible, muscle ultrasound * Wear a wrist-worn activity monitor before surgery * Have routine clinical and surgical information collected from their medical records * Receive a follow-up phone call around 90 days after surgery

This prospective cohort study aims to compare the incidence of Myocardial Injury after Noncardiac Surgery (MINS) in patients undergoing percutaneous nephrolithotomy (PNL) for kidney stones in supine versus prone positioning. MINS is defined as an elevated postoperative troponin level (≥0.03 ng/mL) within 48 hours after surgery. Approximately 400 patients will be enrolled, with 200 patients in each positioning group (supine and prone). The primary outcome is the incidence of MINS, assessed through troponin measurements and electrocardiogram (ECG) findings. Secondary outcomes include intraoperative complications, duration of surgery, and postoperative recovery metrics. The study seeks to determine whether surgical positioning impacts MINS risk, potentially guiding safer surgical practices.