Melissa Walton-Shirley


November 17, 2013

When I told a friend that I was leaving on Friday for the American Heart Association 2013 Scientific Sessions , he said, "Dallas should be interesting. It's the 50th anniversary of the assassination of John F Kennedy." Never-before-seen footage plays here daily, revealing more shocking details of that terrible chapter in US history. One clip in particular struck me as very odd: an unconscious and ashen Lee Harvey Oswald lay dying on a swiftly moving gurney. Jack Ruby's freshly planted bullet had induced massive hemorrhage; Oswald's head lolled back and forth, swaying with the shifting gait of the medics. When he was loaded into the back of the ambulance, not a single hand was on him. There was no CPR, no IV, and no attempt at mouth-to-mouth breathing. Although he was "the most despised suspect of that era," that wasn't why. On November 22, 1963, there was simply no such thing as routine out-of-hospital resuscitation effort.

When my editors at suggested that I sit in on session 5 of the Resuscitation Science symposium on Saturday, I didn't know what to expect. It's old news that we've dropped that dreadful mouth–to-mouth maneuver, of course, the one that I encouragingly refer to as "nothing more than a kiss" to reluctant students. We now compress the chest to the beat of that famous Bee Gees song "Stayin' Alive" until help arrives, but what else should we know?

Over the course of the program, it became obvious that outcomes not only depend upon what we "do" to the pulseless victim, but also who they "are." A patient's baseline characteristics play a more important role in determining who can get to the hospital or walk out of it alive and neurologically intact.

Dr Shaker Eid (Johns Hopkins University, Baltimore, MD) pointed out that in 2012, 359 000 US citizens experienced "EMS-assessed" out-of-hospital cardiac arrest. The CARES registry revealed that 26% of V-fib and pulseless V-tach victims in the field survive to hospital admission but only 9.6% survive to discharge. Controversy swirls around device use, the focus of this session. As the moderator Dr Susan May pointed out, "There is a difference between efficacy and efficiency."

We heard from hopeful scientists, like Brian Mahoney (University of Minnesota, Minneapolis), who continues to insist despite past negative and neutral trials on the utilization of devices, like the King airway, the impedance threshold device (ITD), and the LUCAS 2. He is a firm believer in the ITD, which the February 2010 World Journal of Cardiology describes as "a small (35-mL), single-use, disposable plastic valve that can be attached to a tracheal tube, a face mask, a laryngeal mask, or other protective airway device and uses a silicon diaphragm to selectively impede inspiratory airflow when the intrathoracic pressure is less than 0 atm to create and maintain a vacuum within the chest that further improves venous return into the heart."

Dr Mahoney noted, "Mechanical CPR and high-quality CPR are the basics of good outcomes, but high-quality CPR is really hard to do, and it's dangerous to do it in a moving ambulance." Dr Mahoney was a principal investigator in the ResQ trial. The ITD is commercially available, but the other device, which he referred to as "the toilet plunger," isn't. In Kentucky, we trained the public for three months every five years such that our manual CPR peaked in 2010–2011, and we saw a 49% increase in survival. Conversely, Dr Mahoney confessed that in the ROC PRIMED data, his pet device, the ITD, did not work. However, upon reanalysis, only one-third of patients received the recommended rate, one-quarter had the recommended depth, and one-quarter had the recommended rate and depth of CPR. "If all three were right, the survival doubled. So we use it, we believe in it," he insisted.

From CPR to Supersoldiers?

There's much more to CPR than mere mortals have guessed.

Dr Victor Convertino (US Army Institute of Surgical Research, Houston, TX) had to "swap out" his laptop due to governmental regulation before he could begin his presentation. He was careful to add that the opinions expressed were his and "not that of the State Department." He then launched into an explanation of the future of resuscitation; seeds that will not likely blossom until many years beyond our generation, derived from new technology from the prehospital battlefield setting.

"Resuscitation should be guided by compensatory reserve. How can we use mechanisms that already exist? How can we improve or optimize those mechanisms?" Dr Convertino rhetorically asked, adding that current standard vital signs can be misleading. "We ran trials on LBNP (lower body negative pressure—a good model for hemorrhage simulation) and have now taken 150 humans to the point of decompensation," he said, as he began to describe findings in subjects in whom a 50% loss of blood volume was replicated. Under protest, he had to switch from human subjects to baboons, but the data were similar.

"It became apparent that we should be measuring the features of the arterial waveform under the conditions of hemorrhage," Convertino pointed out. "With 1 L of blood (equiv), the changes in the feature of the arterial waveform are distinct. He described how one patient with a very low tolerance for shock demonstrated an average systolic BP of 116 until they crashed during the protocol at only 450 mL of blood loss. "This is the person who gives blood and faints," he said. ("Not someone you'd want to have on the front lines," I thought.) Then there are some individuals with a higher tolerance for blood loss. "Though the BP was lower, at 104 systolic, and the loss was three times that of the one above, the patient remained compensated. It is that top individual that we need to be able to recognize first—they will go into shock first," he pointed out. (And kept off the front lines, I thought.)

It is from this information that a new paradigm for understanding the reserve for compensation for hemorrhagic shock was developed, and it is also likely where we will find the "what we are" that makes some tolerate cardiogenic shock better than others from both the standpoints of recovery of systolic ejection fraction and neurologic function.

Robotics engineers at the University of Colorado took Dr Convertino's information and learned signals and expertise in the "feature extraction of waveforms." They input 30 heartbeats and built an algorithm so we can have a "gas gauge," such that you are either "full" or you are "empty," and called it a "compensatory reserve index." When only 30% reserve is left, the handheld gauge turns red. He then revealed, "This other subject took only 13 minutes to hit 'red,' but vital signs were normal with only 30% of compensatory reserve left. It took 22 to 23 minutes for a 'total crash' of the other subject with BP 69/45." If we can increase or analyze compensatory reserve, "we then improve survivability and buy time."

After his presentation, Dr Convertino showed me his device, called a "Cipher Sensor." He already uses it when he runs a 5K and ducks into a tent for a break. It directs him as to whether he's reaching a "decompensation point" and to either "immediately hydrate" or "continue to run." He believes if it becomes commercially available, it could have much broader application.

This wealth of information set me to thinking that perhaps we should look at how a patient's baseline medications affect their ability to survive arrest. To assess a "compensatory reserve index" prior to discharge might direct us to reset heart rate, blood pressure, and volume status individually, depending on what we find. Apparently, this technology is invaluable on the front lines of combat, for triage teams, and in MASH tents, but perhaps it could be useful to build an elite force of supersoldiers who might hold on to consciousness and life more easily until they could be reached. "The army would find that cost-prohibitive," responded Dr Convertino. But more broadly, it might help us develop an elite force of regular folks who are better equipped to survive the unthinkable.

We've come a long way since the scoop-and-run-only era of Kennedy and Oswald, but disappointingly, time has stood still for the past eight years with no improvement in out-of-hospital cardiac-arrest survival. Perhaps with the steadfast insistence of forward thinkers like Convertino, Mahoney, and Eid, we can propel more of those unfortunate 300 000 victims of out-of-hospital cardiac arrest in the US toward a healthier future, or at the least some chance for any future at all.


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