Inclusion Criteria:  Adults (≥18 years) undergoing elective major surgery and providing informed consent All types of open or lap-assisted abdominal or pelvic surgery with an expected duration of at least 2 hours, and an expected hospital stay of at least 3 days  At increased risk of postoperative complications, as defined by any of the following criteria:  age ≥70 years known or documented history of coronary artery disease known or documented history of heart failure diabetes currently treated with an oral hypoglycemic agent and/or insulin preoperative serum creatinine >200 micromol/L (>2.8 mg/dl) morbid obesity (BMI ≥35 kg/m2) preoperative serum albumin <30 g/L anaerobic threshold (if done) <12 mL/kg/min  or two or more of the following risk factors:  ASA 3 or 4 chronic respiratory disease obesity (BMI 30-35 kg/m2) aortic or peripheral vascular disease preoperative Hb <100 g/L preoperative serum creatinine 150-199 micromol/L (>1.7 mg/dl) anerobic threshold (if done) 12-14 mL/kg/min  Exclusion Criteria:  Urgent or time-critical surgery ASA physical status 5 - such patients are not expected to survive with or without surgery, and their underlying illness is expected to have an overwhelming effect on outcome (irrespective of fluid therapy) Chronic renal failure requiring dialysis Pulmonary or cardiac surgery - different pathophysiology, and thoracic surgery typically have strict fluid restrictions Liver resection - most units have strict fluid/CVP limits in place and won't allow randomisation Minor or intermediate surgery, such as laparoscopic cholecystectomy, transurethral resection of the prostate, inguinal hernia repair, splenectomy, closure of colostomy - each of these are typically "minor" surgery with minimal IV fluid requirements, generally low rates of complications and mostly very good survival.