None listed
Conditions
Brief summary
This study is a prospective, single centre, observational pilot study examining the clinical relevance and outcomes of changes in cerebral vascular autoregulation during general anaesthesia in patients presenting for non-cardiac surgery. Primary outcome is post-operative quality of recovery, and secondary outcomes are patient mortality and major morbidity. This study is a sub-study of a larger, multicenter study on the effect of depth of anaesthesia on patient outcomes (BALANCED study). Recent animal and human studies have investigated indices of cerebrovascular autoregulation (CVAR), including the tissue oxygenation index (TOx), cerebral oximetry index, haemoglobin volume index, and pressure reactivity index. These indices are derived from measuring different surrogates of cerebral blood volume or cerebral blood flow, and calculating a moving correlation coefficient between the surrogate and mean arterial pressure. Specifically, the TOx index measures cerebral tissue oxygenation using non-invasive near infrared spectroscopy (NIRS) as a surrogate of cerebral blood flow and correlation with mean arterial pressure (MAP). Thus, a TOx index can reflect CVAR changes in blood vessel diameter to maintain a constant cerebral blood flow despite changes in systemic arterial blood pressure. The TOx index is thus a novel measure of adequacy of cerebral perfusion. We hypothesise that patients who have impairment in CVAR may be exposed to episodes of cerebral ischaemia resulting in end organ dysfunction. In a number of prospective observational studies recruiting cardiac surgical patients undergoing cardiopulmonary bypass, impaired autoregulation has been associated with cerebral injury, stroke and acute kidney injury. These studies have also defined a threshold level of MAP when autoregulation is lost, as well as a range of MAP when autoregulation is optimised. However, our understanding of this association is incomplete. This study will improve this understanding in a non-cardiac surgical population who are at higher risk of complications after anaesthesia. Elderly patients greater than or equal to 60 years old admitted for major non-cardiac surgery will be monitored using NIRS to derive a real-time TOx index. We will prospectively measure patient outcomes including post-operative quality of recovery, symptoms and signs of major organ dysfunction, and mortality. Statistical analysis will be performed to determine the strength of association between patient outcomes and episodes of cerebral ischaemia as detected by TOx. This study will also provide essential data to help design a future randomised clinical trial. We would plan an interventional arm using the TOx index and the optimal autoregulation MAP value, as goal-directed therapy to minimise the time that patients are exposed to potential cerebral ischaemia.
Interventions
In this observational study, near infrared spectroscopy will be used to measure cerebral tissue oxygenation saturation during major surgery, as a surrogate measure of cerebral blood flow. A moving Pearson correlation index between cerebral saturation and mean arterial pressure is derived to produce the Tissue Oxygenation (TOx) Index, lower limit of cerebrovascular autoregulation (LLA), and the optimal blood pressure of unimpaired autoregulation (ABPopt). TOx, ABPopt, and LLA data is collected no
In this observational study, near infrared spectroscopy will be used to measure cerebral tissue oxygenation saturation during major surgery, as a surrogate measure of cerebral blood flow. A moving Pearson correlation index between cerebral saturation and mean arterial pressure is derived to produce the Tissue Oxygenation (TOx) Index, lower limit of cerebrovascular autoregulation (LLA), and the optimal blood pressure of unimpaired autoregulation (ABPopt). TOx, ABPopt, and LLA data is collected non-invasively during anaesthesia in an elderly population presenting for major non-cardiac surgery. These will be analysed against patient outcomes of post-operative recovery, mortality, and morbidity to assess strength of association, and predictive ability of post-operative risk stratification. The trial duration is expected to be 1 year.
Sponsors
Liverpool Hospital, South West Sydney Local Health District
Eligibility
Sex/Gender
All
Age
60 Years to No maximum
Healthy volunteers
No
Inclusion criteria
Adult patients presenting for non-cardiac surgery, who fulfil the following: * age greater than or equal to 60 years old * American Society of Anesthesiologists (ASA) physical status 3 or 4 * elective major surgery, defined as operations expected to last greater than or equal to 2hours, and post-operative hospital stay of greater than or equal to 2 nights * General anaesthesia with or without major regional anaesthesia * have standard anaesthetic management, which includes the following monitoring: arterial catheter pressure waveform, end-tidal volatile agent concentrations, and non-invasive processed electroencephalography (Bispectral index, BIS)
Exclusion criteria
* Certain non-cardiac surgical operations, due to the surgical site either adjacent or interfering with the near infrared spectroscopy optode placement, or of the recording electrodes of the depth of anaesthesia monitor, will be ineligible for recruitment. These are intracranial and extracranial neurosurgical and head/neck operations * unable to consent * surgery with "wake-up" testing * Patients who are not fluent in English, as they may be unable to complete questionnaires designed for Post-operative Quality of Recovery testing relevant to post-operative recovery * Patients, who at the discretion of the treating anaesthetist, receives a total intravenous general anaesthetic (TIVA) technique instead of an inhalational general anaesthesia * previous enrolment in the BALANCED depth of anaesthesia and patient outcomes study
Outcome results
None listed