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Pacing the Brain

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Dr. Romer Geocadin

Andy suffered a cardiac arrest at work. 911 was called, medics arrived, placed electrocardiograph (EKG) leads to observe his heart rhythm, and initiated CPR. After his heart was restarted, Andy was transported to the hospital, where he lay in a coma for days while doctors monitored him, hoping that he would awaken. Although Andy’s heart had restarted, his brain lay dormant. Imagine a scenario in which the medics, while placing the EKG leads to monitor Andy’s heart activity could also place electroencephalograph (EEG) leads to monitor specific brain activity. Imagine further, if after restarting Andy’s heart and resetting its rhythms, they could also monitor and restart his brain and reset its activity to bring Andy to consciousness.

Anesthesiology faculty member Dr. Romer Geocadin imagines this scenario and is working toward developing such a monitor and potentially a means to “defibrillate or restart the brain.” Approximately 60%–80% of those who survive cardiac arrest are left in a comatose state induced by brain injury that results when the heart temporarily stops pumping blood to the brain. Such patients are filling beds in hospitals and nursing homes across the country. In an effort to reduce these numbers, Geocadin’s team is studying how the brain restarts from the dormancy of a coma with the goal of developing strategies and treatments that will help the brain to reset and provide protection during the process. We know how the heart restarts and ways to help it. The heart is basically composed of a simple electrical circuit; however, the brain, with its complex circuitry, is another matter.

Although research in this area has focused on a region of the brain that handles the upper-level functions of learning and memory, Geocadin’s group maintains that only after discovering how the brain restarts can we worry about these higher functions. They believe that located somewhere in the ascending arousal system (brainstem, upper posterior midbrain, and thalamus) is a “switch” that turns on the brain and activates the cortex, which controls our consciousness. Some individuals in a persistent vegetative state can be aroused but cannot achieve consciousness because the switch never turns on the cortex; those in coma may never be aroused because they have problems with the “switch” as well as with the cortex.

Using simplified EEG studies, Geocadin’s team has studied the brain’s electrical activity in animals and people recovering from cardiac arrest and discovered key characteristic responses of the ascending arousal system and cortex. In preclinical studies, they observed that how the brain recovers within the first 90 minutes after cardiac arrest predicted brain function at 24–72 hours. In humans, data collected from patients’ EEGs within the first 6 hours strongly predicted their status at hospital discharge.

Once they were able to define the disease process, Geocadin’s team began to consider the possibilities of intervention. They have found that the early period of recovery is the best time to institute interventions. Along with other groups, they have made enormous progress with the protective effects of hypothermia (low temperature) therapy. Although the mechanism is unknown, hypothermia works on multiple sites and levels. It has been reported to act on the release and activity of neurotransmitters (the chemicals through which nerve cells communicate), inflammation, nerve cell injury, and cell death. Indeed, it is the first strategy that leads to both improved survival and enhanced functional quality of life after CPR.

Using novel EEG measurement and behavioral testing, Geocadin’s group is now conducting an NIH-sponsored, multicenter trial to study early brain recovery in an attempt to identify which patients will have the best outcomes. They hope to pinpoint the treatment strategy that will lead to optimal function and brain protection after cardiac arrest.

Geocadin’s team hopes to begin another study to specifically define the mechanism by which the brain restarts and how hypothermia impacts it. In preclinical models, they are studying how hypothermia can protect the circuitry of the brain that is most important for arousal and consciousness.

If the heart can be restarted with electrodes, it can be paced. The ultimate goal is to be able to do the same for the brain—to “pace the brain.”

Dr. Geocadin believes that this is a very hopeful time for what used to be a very devastating neurologic injury. Dr. Geocadin’s research collaborators include Nitish Thakor, Matthew Koenig, Xiaofeng Jia, Daniel Hanley, Peter Kaplan, Nathan Crone, Steve Schulman, Nisha Chandra, Hardin Pantle, Tracey Hartmann, the Infinite Biomedical Technology group, and many others. Details about his research can be found at http://www.hopkinsmedicine.org/neurology_neurosurgery/specialty_areas/neurocritical_care/.

 
 
 
 
 
 

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