Role of Cerebral Oximetry in Reducing Postoperative End Organ Dysfunction/Failure After Complex Non-Cardiac Surgery

Overview

The number of elderly patients requiring general anesthesia for major surgical procedures is increasing dramatically. It is estimated that 20% of these patients will develop major complications after surgery. Monitoring brain oxygen saturation may be helpful in reducing the postoperative complication rates. A decrease in brain oxygen is a sign that all other vital organs such as kidneys, heart, liver, and intestines have reduced blood supply and are starved from oxygen. This happens in 1 out of 5 patients undergoing major complex surgeries. Brain oxygen saturation monitor at this time is not used routinely during surgery, primarily due to the added cost, as well as, insufficient evidence that restoring the brain oxygen saturation to baseline would result in better outcomes. Patients will be randomly assigned to either study or control groups. In the study group, a special algorithm will be used to restore brain oxygen saturation. In the control group, the brain oxygen saturation will be monitored continuously, but the monitor screen will be electronically blinded, and standard clinical care applied. The objective of this study is to see if restoring the brain oxygen saturation to baseline results in less complication rates after surgery. The objective of this study is to reduce the incidence of postoperative morbidity due to end organ dysfunction after major non-cardiac surgery in elderly patients. The primary aim is to determine if restoration of rSO2 to baseline levels results in reduced incidence of major organ morbidity and mortality (MOMM). A secondary aim is to determine a cost-effectiveness of this monitoring modality.

With the increase in life expectancy observed in the last decades, the number of aged patients requiring general anesthesia for major non-cardiac surgery, such as abdominal, pelvic, and thoracic surgeries has increased dramatically. This patient population is at increased risk of postoperative complications due to the presence of multiple comorbidities and reduced physiological reserve. One of the largest prospective studies of over 4000 patients aged 70 years and over undergoing major non-cardiac surgery identified that 68% of these patients had pre-existing comorbidities. Furthermore, the 30-day postoperative mortality was 5% and major postoperative complications were present in 20% of patients. The authors concluded that strategies are needed to reduce complications and mortality in older surgical patients. The primary goal of hemodynamic management during the surgical procedure is to ensure adequate perfusion and oxygen delivery to the vital organs. In the last decade, technological research has expanded the application of near infrared spectroscopy (NIRS) to allow continuous non-invasive monitoring of cerebral oxygen saturation, providing information on the real time status on the balance between brain oxygen supply and demand. Furthermore, NIRS provides extra assurance of the adequacy of global oxygen balance, particularly focusing on the venous side of the circulation. Moreover several studies have demonstrated that changes in cerebral tissue oxygenation may correlate with changes in cerebral blood flow when cerebral metabolic rate of oxygen and arterial blood oxygen content remain constant. With the current standards of monitoring that primarily focus on the left heart, i.e., oxygen supply, and not the imbalance between oxygen supply/demand, the vital organ ischemia may go unnoticed until functional organ damage becomes evident. Regional cerebral oxygen saturation (rSO2) provides a non-invasive alternative of adequacy of systemic oxygen balance that correlates well with a gold standard of mixed venous oxygen saturation. Cerebral desaturations have been reported in more than 20% of cases when monitoring regional cerebral oxygen saturation (rSO2) in elderly patients undergoing non-cardiac abdominal surgery. Low rSO2 values have been associated with postoperative cognitive dysfunction (POCD), perioperative stroke, increased incidence of major organ morbidity, and even 30-day and 1-year mortality after cardiac surgery. Furthermore, low preoperative rSO2 measurements have been associated with higher risk of postoperative delirium in both cardiac and non-cardiac surgical populations. The proposed trial will be the first large prospective randomized controlled clinical trial assessing the effectiveness of rSO2 restoration in reducing postoperative morbidity associated with end organ dysfunction after major non-cardiac surgery.