A study of indicators of heart and circulation injury in adult patients undergoing major abdominal surgery.

The OPtimisation of Perioperative Cardiovascular Management to Improve Surgical outcomE II trial (Optimise II) is large multi-centre randomised trial, which seeks to establish whether targeted fluid optimisation with minimally invasive cardiac output monitoring and a low dose inotrope infusion can improve outcomes in patients having elective gastrointestinal surgery. In the intervention group of OPTIMISE II, a haemodynamic protocol will start at the induction of surgery and continue until 4 hours after surgery. Cardiac output and stroke volume will be measured by cardiac output monitor, Edwards Lifesciences Flotrac(TM) or Clearsight (TM). In addition to the maintenance fluid and blood products, patients will receive 250ml fluid challenges with a recommended solution as required in order to achieve a maximal value of stroke volume. The absence of fluid responsiveness will be defined as the absence of a sustained rise in stroke volume of at least 10% for 20 minutes or more. In addition, patients will receive a low dose inotrope infusion at a fixed rate which will be commenced after fluid replacement has been initiated. The choice of inotrope will be made at the discretion of the local investigator, according to local preference and availability. The options are dobutamine at a dose/rate of 2.5 µg/kg/min and dopexamine at an equipotent dose/rate of 0.5 µg/kg/min. In this sub-study, we will collect biomarkers in order to identify any differences in cardiac injury (Troponin) and endothelial injury between the two comparator groups in Optimise II, cardiac output-guided haemodynamic therapy with an inotrope versus "usual care" without the use of cardiac output monitoring. The biomarkers will be collected over 48hrs from the beginning of surgery until day 2 post surgery.