CPR and Therapeutic Hypothermia Forum
Welcome to the CRS forum. The following are questions that we have received through our website. We are always happy to answer any questions you may have about CPR, therapeutic hypothermia, and cardiac arrests. Please note that the responses posted on this page are only opinions from our medical professionals. We do our best to answer these important questions, but we are dealing with a complex field and nothing below can be considered an absolute certainty. Thank you for your questions!
November 9, 2009
Q: We have had several TH patients who were also Code Mi patients. Cardiologists have had questions regarding
TH and these patients, specifically whether spasm is more easily
induced or if medications such as bilvalirudin and thrombolytics
interact with TH. Are there any resources or studies on
this specific patient population? I have had little
luck with a literature search - what do you see in clinical
practice?
A: You ask an excellent question - alas, there are very little data published on the specifics of PCI/cath and cooling. The only data that DO exist suggest that morbidity and mortality of combining therapeutic hypothermia (TH) and cath is not worse than cath itself (so that, in aggregate, TH doesn't make things worse) - but no data are published on specific issues with drug metabolism, coronary flow, etc. I can say that we have performed cath on a number of patients while cooled and things seem about the same with regard to medication use, etc. We definitely need more research in this area.
-Benjamin S Abella, MD
July 27, 2009
Q: I can find references that say that overshooting the target temperature (too cold) is harmful and that rapid rewarming can create instability. Is there literature that addresses potential harm of mild fluctuation in temperature during the treatment period of 24 hours?
One of the selling points used by many of the equipment vendors is the claim that their equipment is superior at maintaining the temperature exactly at 33 degrees a high percentage of the time. Is there evidence to indicate that this is most beneficial or that failure to provide this is potentially harmful? Is time frame from initiation until reaching target temperature a higher priority in achieving the best outcomes or is steady maintenance a higher priority? Have protocols that use only iced IV fluids and conventional cooling blankets with less precise temperature maintenance been associated wtih worse outcomes?
A: As you have pointed out there are references for overshooting the target temperature (including my colleague Raina Merchant's paper from 2006) and for the potential risks of rapid rewarming. There is less available on the clinical relevance of variations from the target temperature during maintenance phase related to different devices. Hoedemaekers and colleagues published a paper in Critical Care looking at the speed of cooling and degree of variation with different devices but this didn't address clinical outcomes/relevance (Hoedemaekers CW, et al. Crit Care. 2007; 11(4): R91). It is highly unlikely that 0.3 degrees C variation versus 0.6 degrees C variation is clinically relevant. There currently is no evidence that such tight control is clinically relevant--that doesn't mean data won't emerge at any point.
A large French study comparing surface cooling to endovascular cooling has been completed and is being prepared for press. I don't know the results but one of the questions they will likely address is the precision of maintenance of target temperature. Joe Ornato in Richmond has discussed improvement in their outcomes after they switched from surface to endovascular cooling and attributes some of the improvement to the speed of cooling but this is not a randomized controlled trial.
As you have pointed out many of these details are "selling points" of different devices and focusing too much on those points is, to some extent, missing the forest for the trees. The important point is cooling and high quality ICU care. The recent publication by Friberg and colleagues (Neilson et al, "Outcome, Timing, and Adverse Events in Therapeutic Hypothermia After Out-of-Hospital Cardiac Arrrest," Acta Anesthesiol Scand 2009; 53: 926-936) doesn't discuss variation from goal temperature but does suggest NO relationship between time to target temperature and outcome (median time from arrest to goal temperature [< 34 degrees C] was 260 minutes, IQR 178-400 minutes). I always try to keep in mind that the two landmark studies (NEJM, 2002; 346) used fairly primitive cooling equipment (Bernard-->ice packs; HACA-->forced cold air blankets that were ineffective enough that 70% of the patients required supplemental ice packs) to achieve the statistically significant improvements in neurologic outcomes (Bernard and HACA) and mortality (HACA) that are the foundation for current therapy.
-David Gaieski, MD
June 18, 2009
Q: In a patient with cardiomyopathy EF 15%, and severe pulmonary hypertension RSVP in 60's, who arrests in hospital, what are your thoughts about post-arrest cooling potentially exacerbating pulmonary HTN and myocardial oxygen demand in a pt vulnerable to re-arresting? -Baltimore, MD
A: The use of hypothermia is definitely not without risks for complex patients such as this - alas, no clear data exist to answer your question, but I suspect one could still cool such a patient but with extreme caution.
What we often do, as a matter of practicality, is to cool more "gently" (only to 34 C) in such patients, under the assumption that this mild degree of cooling, while still supported by clinical data and AHA guidelines, might provoke less untoward hemodynamic effect.
-Benjamin S. Abella, MD
April 21, 2009
Q: Have you used Therapeutic Hypothermia in patients with non-cardiac etiologies for arrest? Specifically, we are looking at whether to cool overdose patients, and also we had a young man attempt suicide by hanging. We used TH in both, but ran into logistic issues when MICU critical care attendings balked at taking care on TH patients, as literature generally supports use only in cardiac arrest.
A: Yes, we use hypothermia on most etiologies of arrest – and this seems to be the practice of many other hospitals that use hypothermia. There are growing data from various case series reports that other arrest rhythms and causes of arrest benefit from hypothermia as well. However, we don’t use hypothermia for non-arrest situations (if your near-hanging or OD patients didn’t actually arrest from their problems, we wouldn’t have cooled them).
-Benjamin S. Abella, MD
February 12, 2009
Q: If an athlete gets hot while playing outside with temp of 102 and he is immersed in a tub filled with ice, is there any danger of V.fib or other risk to the patient?
A: I am not aware of any risk of VF or other serious health risks to the rapid sudden cooling of a healthy person with hyperthermia, unless the patient was overcooled to a core body temperature of less than 30 C, when VF becomes a risk.
-Benjamin S. Abella, MD
February 9, 2009
Q: It seems to me that the primary damage mechanism as described by the article is oxidation by free radicals. Have you considered other methods of limiting the supply of oxygen? I am not a medical professional, but my image of a person being resuscitated involves chest compressions, electric shocks if necessary, and an oxygen mask. What would happen if instead of giving the patient extra oxygen, you gave them a limited supply of oxygen, intentionally keep the o2 level provided to the patent low through using a N2 rich blend of breathing air. You could monitor the oxygen levels in the blood and gradually bring them back up so that you don’t cause cell death. Keeping the oxygen levels low might be less traumatic to the patient than intentionally causing
hypothermia.
A: We have been considering a clinical trial of this, although there are some complex issues to figure out (how to easily manage the O2 “ramp up”, what the comparison group should be in a trial, etc). Stay tuned!
-Benjamin S. Abella, MD
February 2, 2009
Q: I just read the article about you, Benjamin Abella and your research on hypothermia in Popular Science (Carnett, J.B. "Cold Relief" Popular Science 274(2) Pg. 54-59). Very interesting, but I was struck by how hard it was to get someone cold quickly. I just watched a TED talk by Peter Ward on mass extinctions and how breathing hydrogen sulfide can help lower body temperature. I don't know much about animal physiology, but perhaps breathing hydrogen sulfide while being on an "IV slushee" would make a person become colder faster.
A: It turns out that this is a gas of great current interest, it also appears to have cell-protective properties in small quantities. A number of laboratory experiments in simulated cardiac arrest are underway using this fascinating molecule … stay tuned! Not quite ready for human testing, I suspect. It’s a tricky gas, and can be toxic at higher doses.
-Benjamin S. Abella, MD
January 13, 2009
Q: Could a Thermosuit spinoff, a 'Neck Vest' that both braces the neck and supercools it immediately, be used in cases where someone gets the same type of SCI, (Spinal Cord Injury) that crippled actor Chris Reeve, which happens a lot in sports arenas and car wrecks, to use cold temperatures in the area of their SCIs so that they DON'T get paralysed later on?
A: This is indeed an area of active investigation at a number of research centers around the country, especially the Miami Project to Cure Paralysis, a research group at the University of Miami. Many investigators believe that hypothermia, such as via a neck cuff as you describe, may hold great promise to prevent paraplegia or other injury from spinal cord trauma.
-Benjamin S. Abella, MD