Supernormal Oxygen Delivery for Elderly Surgical Patients

Elderly patients with poor cardiopulmonary reserve tend to suffer higher risk and develop more complications following major surgery. Quite a few researches have shown the benefits of goal-directed therapy (GDT) using fluid loading or inotropic agents or both to improve outcome during major surgery. However there is concern that inotropic therapy for a supernormal oxygen delivery (DO2I) may lead to an increased incidence of myocardial ischemia. Even though the meta-analysis has stated that DO2I strategy could possibly reduce the incidence of cardiac complication than stroke volume optimization strategy, there are very few evidence available in the literature regarding the effect on myocardial ischemia in surgical patients, especially in non-cardiac surgical patients. This study is undertaken to test the hypothesis that an intraoperative DO2I optimization result in a decreased myocardial ischemia in the elderly high-risk surgical patients.

Elderly patients with poor cardiopulmonary reserve tend to suffer higher risk and develop more complications following major surgery \[1\]. Quite a few researches have shown the benefits of goal-directed therapy(GDT) using fluid loading or inotropic agents or both to improve outcome during major surgery \[2-7\]. The maintenance of adequate tissue perfusion and global oxygen delivery (DO2I) is essential to maintain adequate tissue perfusion and oxygenation in relation to increased metabolic demand during high risk surgery. However, there is concern that inotropic therapy for a supernormal oxygen delivery may lead to an increased incidence of myocardial ischemia \[8\]. Even though the meta-analysis has stated that DO2I optimization could possibly reduce the incidence of cardiac complication than stroke volume optimization strategy \[9\],there are very few evidence available in the literature regarding the effect on myocardial ischemia in surgical patients, especially in non-cardiac surgical patients. This study is undertaken to test the hypothesis that an intraoperative DO2I optimization result in a decreased myocardial ischemia in the elderly high-risk surgical patients. The investigators will conduct a prospective, randomized, controlled, double-blinded trial in seventy patients who scheduled for proximal femur surgery under General anesthesia following nerve block. Both the patients will be allocated to one of two equal groups to receive either intraoperative fluid regimen guided by SV strategy or DO2I strategy. In the control(SV) group, the patients will receive an intravenous infusion of 250 ml Ringer's lactate solution in 5 min as a fluid challenge for stroke volume maximization. In the experimental(DO2I) group, fluid and dobutamine will be given to reach a stroke volume maximization and supernormal oxygen delivery. The primary outcome is preoperative and 24h postoperative serum concentration of troponin T. Secondary outcomes include the incidence of tachycardia, arrhythmia, myocardial infarction, pneumonedema and acute heart failure, blood pressure, pulmonary infection, fluid volume, blood transfusion volume, renal function, PONV, Length of postoperative hospital stay and mortality. Data will be collected and recorded by the clinical teams who are blind to study arm allocation.