Oxygen Extraction and Delivery in Elderly During Major Surgery

Background Intra- and postoperative fluid therapy aims to achieve or maintain pre-specified thresholds of oxygen delivery/blood flow which can be accomplished by use of fluids with or without inotropic drugs. The used thresholds of oxygen delivery were suggested over 40 years ago, in considerably younger patients compared to the current patients. Update of the characteristics of perioperative oxygen delivery and consumption is reasonable in modern clinical settings. Primary outcome: relative changes of oxygen consumption induced by anaesthesia Secondary outcomes: relative changes of oxygen consumption and delivery during surgery and postoperatively, oxygen extraction ratio (measured and estimated), potential markers of oxygen debt frequency of in-hospital postoperative complications, mortality (30 Days) Population: Men and women ≥65 years undergoing major/complex surgical procedures, when intra-operative cardiovascular monitoring is justified according to clinical decision. Intervention: no study related intervention, general anaesthesia and surgery according to clinical routine Blinding: no blinding Study size: Pilot study 1: feasibility assessment of study protocol of intra-operative measurements (n= max 10) Pilot study 2: feasibility assessment of study protocol of postoperative measurements (n= max 10) Main study: 60 subjects (20+´40) Planned analysis of oxygen consumption after 20 monitored subjects Study duration: Duration of haemodynamic monitoring 24-36 hours Duration of observation of clinical outcomes: 7-10 days, mortality at 30 days postop. Investigational events: monitoring of oxygen consumption and delivery monitoring of postoperative clinical outcomes monitoring of markers of tissue injury Assessments, Procedures and Schedule of Investigational Events: Subjects are identified by the operation planning list and assessed for eligibility. The study information will be given verbal during the first hospital visit. Subjects who give written informed consent will be included in the study. Measurements: oxygen consumption by indirect calorimetry via face mask (in awake state) and via expiratory extension tube of anaesthesia machine (unconscious state) cardiac output monitoring via arterial line (LiDCO) blood samples: arterial and venous blood gase samples, Troponin-T urine samples: N-gal Clinical outcomes: Data collection from medical records on postoperative complications using the POMS (postoperative morbidity survey) screening survey at days 3,7 and 10. Postoperative mortality at day 30.