Cerebral Autoregulation Monitoring During Cardiac Surgery

Study Overview
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Brief Summary
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Neurological complications from cardiac surgery are an important source of operative mortality, prolonged hospitalization, health care expenditure, and impaired quality of life. New strategies of care are needed to avoid rising complications for the growing number of aged patients undergoing cardiac surgery. This study will evaluate novel methods for reducing brain injury during surgery from inadequate brain blood flow using techniques that could be widely employed.

Detailed Description
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Brain injury during cardiac surgery results primarily from cerebral embolism and/or reduced cerebral blood flow (CBF). The latter is of particular concern for the growing number of surgical patients who are aged and/or who have cerebral vascular disease. Normally, CBF is physiologically autoregulated (or kept constant) within a range of blood pressures allowing for stable cerebral O2 supply commensurate with metabolic demands. Cerebral autoregulation is impaired in patients undergoing cardiac surgery who have cerebral vascular disease and in many others due to other conditions. This could lead to brain injury since current practices of targeting low mean arterial blood pressure empirically (usually 50-70 mmHg) during cardiopulmonary bypass may expose patients with impaired cerebral autoregulation to cerebral hypoperfusion. The hypothesis of this proposal is that targeting mean arterial pressure during cardiopulmonary bypass to a level above an individual's lower autoregulatory threshold reduces the risk for brain injury in patients undergoing cardiac surgery. Monitoring of cerebral autoregulation will be performed in real time using software that continuously compares the relation between arterial blood pressure and CBF velocity of the middle cerebral artery measured with transcranial Doppler and with cerebral oximetry measured with near infrared spectroscopy. The primary end-point of the study will be a comprehensive composite outcome of clinical stroke, cognitive decline, and/or new ischemic brain lesions detected with diffusion weighted magnetic resonance (MR) imaging. Delirium assessed using a validated procedure that includes validated tools is a secondary outcome measure. Autoregulation is mediated by reactivity of cerebral resistance vessels. A secondary aim of this proposal is to evaluate whether near infrared reflectance spectroscopy can be used to trend changes in cerebral blood volume and provide a reliable monitor of vascular reactivity (the hemoglobin volume index). Assessments for extra-cranial and intra-cranial arterial stenosis will be performed using MR angiography to control for this potential confounding variable in the analysis. Finally, an additional aim of the study will be to assess whether preoperative transcranial Doppler examination of major cerebral arteries can identify patients who are prone to the composite neurological end-point. Near infrared oximetry is non-invasive, continuous, requires little care-giver intervention and, thus, could be widely used to individualize patient blood pressure management during surgery. Brain injury from cardiac surgery is an important source of operative mortality, prolonged hospitalization, increased health care expenditure, and impaired quality of life. Developing strategies to reduce the burden of this complication has wide public health implications.

Official Title
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Continuous Cerebral Autoregulation Monitoring to Reduce Brain Injury From Cardiac Surgery

Conditions
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Thoracic Surgery, Cardiopulmonary Bypass

Intervention / Treatment
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* Drug: blood pressure maintenance based on cerebral blood flow autoregulation measurement
* Device: Control group


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Male or female patients undergoing primary or re-operative Coronary Artery Bypass Graft (CABG) and/or valvular surgery or ascending aorta surgery that requires Cardio-pulmonary bypass (CPB) who are at high risk for neurologic complications (stroke or encephalopathy) as determined by a Johns Hopkins risk score of >0.02 Exclusion Criteria: Contraindication to MRI imaging (e.g., permanent pacemaker, cerebral arterial vascular clips) Liver function test before surgery more than twice the upper limit of institutional normal Pre-existing renal dysfunction defined as an estimated glomerular filtration rate of ≤60 mL/min, or current renal dialysis Emergency surgery Inability to attend outpatient visits Visual impairment or inability to speak and read English. The patient will be excluded from further study if an adequate temporal window for Transcranial Doppler (TCD) monitoring can not be identified before surgery.

Ages Eligible for Study
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Minimum Age: 55 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Control<br>Blood pressure targets during cardiopulmonary bypass based on institutional standards of empiric management. | Device: Control group<br>* Institutional standard of care.<br>* Other names: Usual (Control Group);|
| Experimental: Intervention<br>Blood pressure management based on cerebral autoregulation data. | Drug: blood pressure maintenance based on cerebral blood flow autoregulation measurement<br>* Blood pressure lowered or raised<br>* Other names: Autoregulation;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Composite Neurological Outcome of Clinical Stroke or New Ischemic Brain Lesion on Diffusion Weighted MRI or Neurocognitive Dysfunction 4 to 6 Weeks After Surgery. | The composite neurological outcome was composed of clinical stroke, or new ischemic lesions detected on postoperative brain diffusion weighted magnetic resonance imaging(DWI), or cognitive decline from baseline to 4-6 weeks after surgery. | Up to 6 weeks post-operative | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postoperative Delirium | Assessed with Confusion Assessment Method or Confusion Assessment Method-ICU along with adjudication by team of experts | Postoperative days 1-4 | 
| Multiple Inotropic Drugs>24 Hours After Surgery | Use of multiple inotropic drugs greater than 24 hours after the planned surgical procedure until discharge from the hospital. | 7 days after surgery | 
| Mechanical Lung Ventilation>24 Hours After Surgery | Subjects need for mechanical lung ventilation more than 24 hours after planned surgical procedure. | Up to 28 days after surgery. | 
| Insertion of Intra-aortic Balloon Pump | Procedural insertion of intra-aortic balloon pump within 7 days after surgical procedure | 7 days after surgery | 
| Postoperative Atrial Fibrillation | Clinical diagnosis of postoperative atrial fibrillation from date of surgical procedure to discharge from the hospital. | Up to 28 days after surgery. | 
| Sepsis | Clinical diagnosis of sepsis from time of surgical procedure to discharge from the hospital. | Up to 28 days after surgery. | 
| Acute Kidney Injury Within 7 Days After Surgery. | Subject developed acute kidney injury within 7 days after surgical procedure. Based on Kidney disease: Improving Global Outcomes (KDIGO) classification system. | 7 days after surgery | 
| New Renal Replacement Therapy | Subjects requiring new renal replacement therapy prior to discharge from hospital | Up to 28 days after surgery. | 
| Multisystem Organ Failure After Surgery | Subject diagnosis of multisystem organ failure after surgery. | Up to 28 days after surgery. | 
| Mortality | Subject death within 28 days after surgical procedure | 28 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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cardiac surgery; brain injury; cerebral autoregulation