Perelman School of Medicine at the University of Pennsylvania
Center for Resuscitation Science

Pathophysiology & Other

December 14, 2010

Q: I understand that hypothermia causes decreased cardiac output, but how much?

A: Cardiac output decreases 25-40% depending upon exact target temperature and is mostly relatted to bradycardia; this is usually more than balanced (in regard to oxygen delivery) by decreased metabolism (and decreased oxygen consumption) so that the oxygen delivery/consumption profile is improved.

Q: What effect does a temperature of 33 degrees ALONE have of ejection fraction?

A: Mostly related to bradycardia. See previous comment above.

Q: Combined with a stunned myocardium, 1 day post MI, is there any value to this ECHO?

A: Yes, there is a value to the ECHO as it is telling you what the patient's EF and wall motion are @ that time; most of the stunning from arrest is reversible; the injury from MI leading to arrest is dependent upon how quickly reperfused, how much was penumbra vs. necrosis, and effects of TH on myocardial recovery; Data suggest good outcomes can be attained in this exact patient population if IABB, inotropes, and aggressive post-cath care is used in conjunction with TH.

Q: How long after the patient has been rewarmed would we be seeing "real" LV function data on ECHO?

A: The change in EF related to TH itself will go away as the patient is rewarmed and heart rate increases; the myocardial stunning of post-arrest period usually resolves by hour 40 or so; the injury from MI is dependent upon how much necrosis occurred.

- Dave Gaieski, MD

February 2, 2010

Q: Has your facility done any research on the survival of morbidly obese patients who suffer cardiac arrest? Some specific concerns:

  • Are we able to deliver enough joules?
  • How effective is manual CPR for obese patients vs average wt. patients?
  • Are there mechanical devices available to provide compressions for obese patients?
  • Is special airway equipment available for the obese patient?

A: We have not specifically examined outcome differences in morbidly obese patients who suffer cardiac arrest versus patients with normal BMI. This is an important question, however, and one I am interested in examining. I am just finishing up a paper on BMI in severe sepsis and septic shock, which shows no differences in outcomes (but differences in sources of infection) in the morbidly obese versus non-obese.

We have noted challenges in reaching target temperature in therapeutic hypothermia in morbidly obese patients but have not yet systematically studied the topic. We have successfully treated a >150 kg post-arrest patient using therapeutic hypothermia and our post-arrest algorithm. The patient was discharged to home in pre-arrest condition with normal mental status.

The issue of quality of CPR (QCPR) in the morbidly obese is an important issue.

We are currently trialing the Lucas mechanical compression device in our ED and it will fit many obese patients but there is a limit in the AP diameter it can accept and we were unable to use it on one patient who was approximately 300 pounds.

Regarding your other questions, I am attaching an abstract from Dana Edelson, at University of Chicago, and some of my colleagues at CRS, which addresss many of the QCPR issues.

Regarding airway management--the most important issue with intubating the morbidly obese is positioning, not specialized equipment; placing the patient on a ramp of folded towels or a commercially available ramp, which helps achieve proper head positioning, is the most important single intervention that can be performed; if a morbidly obese person is positioned properly and remains unintubatable, an algorithm for rescue airway management should be in place at the institution - we typically use a CMAC as a video-assisted rescue device if the patient is able to be ventilated and a King airway or LMA if the situation is more tenuous.

- David Gaieski, MD

Abstract link: Click here for the abstract

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

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