EDECMO 18 – Remote Ischemic Conditioning – with Graham Nichol

What this episode covers

Remote Ischemic Conditioning to Reduce Ischemia-Reperfusion Injury after Cardiac Arrest In this episode Zack and Joe talk with a true pioneer in resuscitation and the science of cardiac arrest management. Graham Nichol, from the University of Washington, joined us at Sharp Memorial Hospital for an amazing discussion about "Remote Ischemic Conditioning" and its role in prevention of ischemia-reperfusion injury resulting from cardiac arrest. Is this VooDoo or a real phenomenon? Listen to this episode to find out... Some Definitions: * "Ischemia-Reperfusion" injury: prolonged ischemia to the brain and heart often occur after circulatory arrest. Immediate CPR minimizes this phenomenon but many of our patients who arrest in the pre-hospital setting don't receive immediate bystander CPR, resulting in prolonged ischemia. CPR reintroduces blood flow and oxygen to the previously ischemic tissues. This hyperoxic 'reperfusion' is known to be a main contributor to infarct size in both the heart and brain causing poor neurologic outcomes after arrest. Minimizing this reperfusion injury is major focus of resuscitative science right now. * "Ischemic Conditioning": purposeful application of ischemia and reperfusion, off and on, to the tissues. * "Pre-conditioning" = applying this therapy BEFORE circulatory arrest * "Peri-conditioning" = applying this therapy either DURING circulatory arrest * "Post-conditioning" = applying this therapy AFTER circulatory arrest * "Targeted" vs. "Remote" Ischemic Conditioning: "Targeted" ischemic conditioning: application of conditioning directly to the specific target organ (ie the heart or the brain). This can be done in one of two ways: * systemic ischemic conditioning. * In a pig model of cardiac arrest, Demetris Yannapoulos and Keith Lurie applied brief periods of ischemic post-conditioning via "Stutter CPR" (3-4 cycles of 20 seconds of CPR with 20 second pauses) after prolonged "no flow" arrest - upwards of 20 minutes without CPR - and found normal LV function and elimination of ischemic insult to the brain using this technique. They discussed this controversial topic with Weingart on the emcrit podcast Episode 69 . * Local conditioning: applying ischemic conditioning directly to the target organ * Many studies have shown effectiveness of local ischemic conditioning during PCI for acute MI. After restoration of vessel patency, reperfusion was interrupted by cycles of 1 min of coronary balloon reocclusion. Here is a good summary: * Staat Post-Conditioning the Human Heart 2005 "Remote" ischemic conditioning: application of ischemic conditioning to a REMOTE area of the body (ie the limb) to reduce the degree of injury to the heart and brain that results from cardiac arrest (ischemia) followed by reperfusion (chest compressions, ROSC, or ECMO) by applying the 'remote' ischemia-reperfusion by using a blood pressure cuff on a limb. How it Works: *courtesy of the Lancet Vol 374; Oct 2009 Several theories exist to explain the benefit of ischemic conditioning. I'll break it down in two ways: 1.) Simple explanation: "good humors" are released from the ischemic limb and protect against cell death/apoptosis in the heart and brain. 2.) Complex hypothesis: 1.) RIC induces a cascade of intracellular kinases and modifies mitochondrial function within the cell by opening ATP-sensitive potassium channels and closing the mitoch...

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