Cerebral Oximetry in Management of Post Cardiac Arrest

Resuscitation from a cardiac arrest is a common reason for admission to an intensive care unit (ICU). Because the brain is highly vulnerable to oxygen deprivation, severe brain damage often occurs during a cardiac arrest. Even when the heart has been restarted, there may continue to be reduced blood flow and oxygen delivery to the brain for many hours. ICU professionals generally do not use any tools to detect low oxygen delivery to the brain. Most patients admitted to the ICU are initially in a coma and many will never awaken. Even if they regain consciousness, there may be long-term cognitive and functional disabilities. There are currently no specific treatments available to ICU professionals that are proven to limit brain damage and improve outcomes. Cerebral oximetry is a non-invasive, painless, safe, and easy-to-use tool that detects reduced oxygen delivery to the brain using a sensor over the forehead. Previous research shows that reduced brain oxygen levels \[(regional oxygen saturation (RSO2)\] are predictive of a lower chance of awakening and having a good neurological recovery. This study will assess treatment guided by cerebral oximetry during the initial 48 hours following cardiac arrest. Patients that are in a coma after their circulation has been restarted will be randomly allocated to either usual care based on international guidelines or a protocol aimed at maintaining RSO2 above 60% on both sides of the brain. Cerebral oximetry will be recorded in all patients, but doctors will only be aware of it in one group. If RSO2 drops below 60% for more than 5 minutes, doctors will try to increase it. Actions taken to increase RSO2 may include raising the blood pressure by giving more intravenous fluid or using life-support drugs ("vasoconstrictors" like norepinephrine), stimulating the heart to pump more strongly with medications ("inotropes" like dobutamine, milrinone, or epinephrine), adjusting ventilator settings (to increase the amount of oxygen dissolved in blood or raise carbon dioxide levels, which increases blood flow to the brain), lowering the head of the bed (to increase blood flow to the brain), or giving a blood transfusion (only if the patient has anemia). When RSO2 has been corrected to at least 60% for more than 2 hours, doctors may reverse previous interventions. If they are unable to achieve the goal of 60%, they may lower the target. Efforts to maintain RSO2 in the target range will continue for 48 hours. Investigators will assess how well the protocol works and whether it helps avoid critically low brain oxygen levels. Investigators will also measure various "biomarkers" in the blood that are released when the brain is damaged to see if they are lower when cerebral oximetry is used to guide treatment.