Optimizing Cerebral Oxygenation And Metabolism In Cardiac Arrest

Lin, Steve (Rescu, Li Ka Shing Knowledge Institute, St. Michael's Hospital)
Mentor: Dorian, Paul
Network Affiliation: Cardiac Arrhythmia Network of Canada
 
1. The health problem/issue
Each year in Canada and the United States, more than 340,000 people collapse when their heart suddenly stops beating. This is a condition called cardiac arrest and more than 90% of these people will not survive. Survival from a cardiac arrest depends on the continueddelivery of oxygen to a person’s organs. The brain is especially vulnerable to low oxygen levels and brain injury is the final cause of death and disability for many cardiac arrest patients. Oxygen is delivered in a cardiac arrest during cardiopulmonary resuscitation(CPR). The goal of CPR is to move blood around the body and thus to deliver oxygen to vital organs, particularly the brain. However, there is no standard method to measure how much blood and oxygen is going to the brain. This problem is particularly difficult to solve in real patients. Unlike in animal experiments where probes can be inserted into veins, arteries, and even brain tissue, invasive probes in patients during CPR are difficult, time-consuming, and impractical. A recent technology, near infrared spectroscopy (NIRS), is noninvasive and can measure the amount of oxygen going to the brain. Our investigator team has developed the next generation of NIRS, which can measure not only the amount of oxygen going to the brain, but also how well the brain is using the oxygen. This new generation of NIRS can help direct how we resuscitate patients, with the focus on decreasing brain injury after cardiac arrest.
 
2. The objectives
The objective of this project is to see how the new generation NIRS called hyperspectral NIRS (hNIRS) can perform against the existing multispectral NIRS (mNIRS). We will specifically test both hNIRS and mNIRS in pig cardiac arrest models. We will experiment
giving adrenaline and using different techniques to give breaths during CPR, and see whether hNIRS can measure the amount of oxygen going to the brain and how well the brain is using the oxygen. After these pig experiments, we will test to see if hNIRS can be used in patients. The first set of patients will be those who are receiving new heart valves because during the procedure, their blood pressure is artificially lowered to a point that mimics cardiac arrest. hNIRS will then be tested in out-of-hospital cardiac arrest
patients where paramedics can apply hNIRS to see whether this technology can be used outside of “controlled” environments. This will be the first Canadian study to use any NIRS technology outside of the hospital and laboratory.
 
3. The approach
The first phase of this project is to test hNIRS against mNIRS in 28 pigs to see whether it can detect both brain oxygen levels and brain cell metabolism. We will also test how oxygen levels and cell metabolism change under different conditions of medication use
(e.g. adrenaline) and various techniques to give breaths during CPR. The second phase of this project is to test hNIRS and mNIRS in 10 patients who require aortic valve replacements. During this procedure, patients temporarily have their blood pressures lowered, which allows us to test hNIRS against mNIRS during very low blood pressures in a controlled setting. Next, we will test whether Canadian paramedics can use hNIRS in the out-of-hospital setting in cardiac arrest patients. hNIRS and mNIRS devices will be placedon specialized ambulance units. In 30 adult patients who suffer a cardiac arrest, noninvasive sensors will be placed onto their foreheads while being resuscitated. This will test whether the hNIRS monitor can accurately measure the brain oxygen levels and brain cell metabolism during real-life CPR.
 
4. The unique factors
Questions about how to treat cardiac arrest are hard to answer. Current mNIRS can measure the amount of oxygen going to the brain during CPR but it cannot measure how well the brain is using the oxygen. We have developed the next generation, hNIRS, which can do both. We will first test hNIRS against current mNIRS in the laboratory in pig cardiac arrest models to validate this novel technology. We will then test hNIRS in two clinical patient settings, one in a controlled in-hospital setting and another in an uncontrolled out-of-hospital setting, to see whether it is possible and practical to use in cardiac arrest patients. This will be the first Canadian study to use any NIRS technology outside of the hospital and laboratory.
 
5. How the proposed project is relevant to the objectives of the initiative
The majority of cardiac arrests outside of the hospital are caused by underlying heart disease and heart attacks. Despite decades of research, survival from cardiac arrest remains poor and those patients who do survive, suffer from significant brain injuries. As we continue to find ways to improve resuscitation in cardiac arrest patients, there is a need to measure the effects of medical treatments on the brain in a non-invasive manner. hNIRS can be the needed technology to monitor the amount of oxygen going to the brain as well as how well the brain is using the oxygen during cardiac arrest resuscitation. Our study will test how hNIRS compared to current mNIRS devices under different conditions in the animal lab and in the community. This research can impact on the future development of CPR guidelines and the care of all cardiac arrest patients.
 
6. The impact
This study will have a major impact on the quality of care for people who suffer a cardiac arrest and it is very much in alignment with the Heart and Stroke Foundation of Canada’s mission statement. There is still much to learn about current cardiac arrest treatments because we cannot easily measure the effects that these treatments have on the brain. Brain injury after cardiac arrest is the leading cause of death and disability for these patients. If hNIRS is found to be possible to use for cardiac arrest patients, including those outside of the hospital, it may finally be possible to measure and monitor the amount of oxygen going to the brain, as well as how well the brain is using the oxygen in a non-invasive, easy and practical way. This has the potential to tailor our resuscitation to specific patients and to direct which treatments should be used to give the best chance of survival and good brain function to cardiac arrest patients.
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