Safety and Efficacy of Perioperative Volume Replacement with Volulyte 6% in Moderate-to-high Cardiovascular Risk Patients Having Major Abdominal Surgery

Inclusion Criteria: * Are at least 45 years old; * Scheduled for elective open or laparoscopic gastrointestinal surgery expected to last ≥2 hours; * Having general anesthesia; * Expected to require at least overnight hospitalization; * Subject to at least one of the following risk factors: 1. Age ≥65 years; 2. History of peripheral arterial disease; 3. History of coronary artery disease; 4. History of stroke or transient ischemic attack; 5. Diabetes requiring medication; 6. Current smoking or 15-pack-year history of smoking tobacco; 7. Body mass index ≥30 kg/m2; 8. Preoperative high-sensitivity troponin T ≥14 ng/L or troponin I equivalent, defined as ≥15 ng/L (Abbott assay), 19 ng/L (Siemens assay), or 25% of the 99% percentile for other assays - all within 6 months; 9. B-type natriuretic protein (BNP) ≥80 ng/L or N-terminal B-type natriuretic protein (NT-ProBNP) ≥200 ng/L within six months. Exclusion Criteria: * Participate in conflicting studies; * Are designated American Society of Anesthesiologists physical status 4; * Are pregnant and/or breastfeeding; * Have hypoproteinemia (serum albumin \<30 g/L) or were given preoperative intravenous colloids, including albumin; * Have recent intracranial or cerebral hemorrhage; * Have preoperative acute kidney injury or chronic renal insufficiency (Serum Creatine ≥140 µmol/L for men, Serum Creatine≥120 µmol/L for women and/or oliguria/anuria) or renal replacement therapy; * Have severe hepatic impairment (Alanine Transaminase (ALT) and/or Aspartate Aminotransferase (AST) more than two times the upper limit of normal); * Are in congestive heart failure or have pulmonary edema; * Are critically ill or septic; * Have electrolyte disorders such as hypernatremia, hyperchloremia, hyperkalemia, or severe alkalosis; * Are fluid overloaded or dehydrated; * Have clinically meaningful coagulation or bleeding disorders; * Had a solid organ transplant; * Have a current serious burn injury; * Have a mental illness that precludes adequate consent or cooperation with the proposed trial; * Have known hypersensitivity or contraindication to Volulyte 6% or any sodium acetate Ringer solution component.