Does measuring pre-surgery brain oxygen levels in sick elderly patients coming in for major elective non-cardiac surgery allow us to predict who will have more complications, including death, major organ failure, and post-operative delirium
The Use of Preoperative cerebral tissue saturation (ScO2) to Stratify Cardiovascular Risk in High Risk Elderly Patients admitted for Major Non-Cardiac Surgery
Liverpool Hospital
400 participants
Jan 23, 2017
Observational
Conditions
Summary
There is a biologically plausible mechanism to explain why pre-operative cerebral tissue oxygen saturation (ScO2) can be a surrogate measure of underlying cardiopulmonary function. ScO2, as measured by near-infrared spectroscopy, represents a dynamic balance between oxygen delivery and extraction by cerebral tissue. When not physically active, there is a stable rate of cerebral oxygen extraction. When ScO2 is measured in patients who are resting, breathing room air, and without the influence of medications, the ScO2 value is primarily determined by the effectiveness of oxygen delivery by the cardiopulmonary system. Low pre-operative ScO2 is thus an indication of poor cardiopulmonary reserve. This has been demonstrated in studies correlating pre-operative ScO2 values to existing measures of cardiopulmonary function, including left ventricular ejection fraction, pulmonary artery catheter cardiac output, and with cardiopulmonary exercise testing. Subsequent studies in cardiac surgery patients have found that low pre-operative ScO2 is associated with increased risk of death, delirium, and major adverse events. We performed a pilot study which showed that low pre-operative ScO2 below 68% is similarly observed to increase the risk of mortality or major morbidity in major non-cardiac surgery. To confirm these pilot study results, we intend to perform a prospective, double blinded, multicentre observational study on the predictive role of low pre-operative cerebral tissue saturation and major adverse outcomes in elderly, high risk patients undergoing major elective non-cardiac surgery. Aims The primary outcome of this study is to determine if low resting pre-operative ScO2, measured in room air and with oxygen supplementation, is associated with mortality or major morbidity. The secondary outcome of this study is to determine if low resting pre-operative ScO2 is associated with increased risk of post-operative delirium.
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Interventions
Prospective, multicentre, double blinded, observational study. Participants are elderly patients greater than or equal to 60 years old, American Society of Anesthesiologists (ASA) 3 or 4, elective major non-cardiac surgery anticipated to last for greater than or equal to 2 hours, receiving a general with or without regional anaesthesia. Pre-operative characteristics such as gender, age, body mass index, Charlson score, co-morbidities, medication history, haemoglobin, creatinine, and albumin levels will be collected in the pre-anaesthesia clinic. Cerebral oximetry will be placed on the patient's forehead to collect ScO2 values from both cerebral hemispheres. These are measured using non-invasive electrodes with embedded near-infrared light sensors. Baseline ScO2 is taken at room air, at rest, and supplemented ScO2 is taken after breathing 6L/min oxygen delivered by Hudson mask after 5 minutes. This is performed by a researcher trained in correctly applying the cerebral oximetry sensors on patients' heads. This baseline measurement can occur in the pre-anaesthetic clinic or anaesthetic bay, up to 4 weeks prior to surgery. This is a pragmatic study and there is no change to the intra-operative anaesthesia or surgical management. Intra-operative data collected includes blood loss, doses of anaesthesia medications, opioid use, use of local anaesthetics, vasopressor use and duration of surgery. Patients will be followed up for 30 days after surgery for the following primary and secondary outcomes: 1. Major Adverse Events (MAE) which includes: all cause death, acute myocardial infarction, cardiac arrest, stroke, pulmonary embolism, acute kidney injury, sepsis 2. Number of post-operative days of delirium, measured using the Confusion Assessment Method (CAM) questionnaire. All post-operative data will be collected by blinded researchers, through direct ward follow up of patients, telephone follow up at 30 days if already discharged from hospital, liaison with the patient's relatives, surgical team or local general practitioner, or if deceased, postmortem results from hospital medical records.
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ACTRN12616000873426