Prehospital therapeutic hypothermia: Is it still cool?

ILCOR releases advisory statement on patient temperature management after ROSC


By Brian Behn

The Advanced Life Support Task Force of the International Liaison Committee on Resuscitation (ILCOR) issued an advisory statement in advance of the 2015 ECC and CPR guidelines. The evidence-based task force examined the benefits, potential harms, and outcomes of different methods of therapeutic hypothermia [1].

Targeted temperature management versus therapeutic hypothermia

It is important to understand the difference between targeted temperature management (TTM) and therapeutic hypothermia (TH) when interpreting ILCOR’s advisory statement. TTM is the practice of maintaining a post-cardiac arrest patient's temperature between 32 and 36 degrees Celsius and preventing a fever. A recent study showed no difference in outcomes between cooling to 32 C and maintaining a near normal temperature of 36 C [2].

TH is the practice of actively cooling a post-cardiac arrest patient to 32 C and keeping them at that specific temperature.

ILCOR is a multi-national consortium of agencies, including the American Heart Association, that composes resuscitation guidelines. The task force reviewed available evidence to answer these questions:

1. For patients who remain comatose after return of spontaneous circulation (ROSC), should targeted temperature management be used?

The task force answered yes. TTM should be used to prevent patients that achieve ROSC from becoming febrile. It is unclear if cooling to 32 C offers any benefits beyond those of cooling to 36 C. No recommendation for a specific temperature goal within the range of 32 to 36 C was made.  

2. Does early (prehospital) induction of targeted temperature management affect outcome? 

ILCOR states that further research is needed to answer this question; however, the advisory statement mentions seven different random controlled trials of prehospital TH following out-of-hospital cardiac arrest have failed to show any benefits on neurologic outcomes or mortality.

Memorable TH quotes from the ILCOR ALS advisory task force

Chilled saline for hypothermia induction removed

"We recommend against routine use of prehospital cooling with rapid infusion of large volumes of cold intravenous fluid immediately after ROSC (strong recommendation, moderate-quality evidence)."

What about other methods of cooling?

"Other cooling strategies and cooling during cardiopulmonary resuscitation in the prehospital setting have not been studied adequately, and further research in this area is needed."

Targeted temperature management rather than therapeutic hypothermia

"We suggest targeted temperature management as opposed to no targeted temperature management for adults with OHCA with an initial non-shockable rhythm (weak recommendation, very low-quality evidence) who remain unresponsive after ROSC."

Key takeaways for EMS

There are key takeaways for EMS from the ILCOR ALS task force advisory statement.

  • The 2015 ILCOR guidelines bring the practice of prehospital TH following adult cardiac arrest into question. There is little to no evidence that prehospital TH has any positive effects on long term outcomes such as neurologic recovery following cardiac arrest.
  • Using chilled saline for induction of prehospital TH is potentially harmful to patients and this practice should be abandoned. One well-powered study found patients who received chilled saline were more likely to re-arrest and that induction of TH with chilled saline led to increased rates of pulmonary edema [3].

We are still a few days away from the release of the official 2015 ILCOR/AHA guidelines but this advisory statement seems to suggest there may not be much of a role for prehospital induction of TH and that some methods of induction may be harmful.

About the author

Brian Behn, BA, NR-P, FP-C is a paramedic supervisor and quality assurance / quality improvement officer for Chaffee County EMS in Salida, Colorado.

References

  1. Michael W. Donnino, Lars W. Andersen, Katherine M. Berg, Joshua C. Reynolds, Jerry P. Nolan, Peter T. Morley, Eddy Lang, Michael N. Cocchi, Theodoros Xanthos, Clifton W. Callaway, and Jasmeet Soar. ILCOR Advisory Statement: Temperature Management After Cardiac Arrest: An Advisory Statement by the Advanced Life Support Task Force of the International Liaison Committee on Resuscitation and the American Heart Association Emergency Cardiovascular Care Committee and the Council on Cardiopulmonary, Critical Care, Perioperative and Resuscitation Circulation. 2015;10.1161/CIR.0000000000000313 published online before print October 4 2015, doi:10.1161/CIR.0000000000000313
  2. Nielsen N, Wetterslev J, Cronberg T, et al. Targeted temperature management at 33°C versus 36°C after cardiac arrest. N Engl J Med. 2013;369(23):2197-206.
  3. Kim F, Nichol G, Maynard C, et al. Effect of prehospital induction of mild hypothermia on survival and neurological status among adults with cardiac arrest: a randomized clinical trial. JAMA. 2014;311(1):45-52.

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