Takeaway 3: There is no clear superiority of invasive cooling (through a central line or peritoneal catheter) versus noninvasive cooling methods (eg, cold saline boluses, cooling vests, etc.) with regard to mortality.
The AAN guideline found two Class III studies addressing this question, but both failed to show a benefit in mortality or neurological outcome for invasive versus noninvasive cooling strategies for TTM. Among this weak evidence, there was some suggestion that invasive cooling through a central line may provide less temperature variability, but it also is associated with more frequent bleeding complications. The bottom line is that more studies need to be done, and for now, emergency physicians should choose a method they have available at their institution and are most comfortable with.
Takeaway 4: There are a lot of interventions other than TTM that have been proposed to decrease OHCA neurological damage, but none cited by the AAN guideline are supported by strong evidence and they have less applicability to emergency physicians.
Some of the treatments reviewed were erythropoietin, corticosteroids, xenon gas, and others. None of these had strong evidence in their favor. Also, most of the therapies mentioned in the AAN guideline (other than TTM) are probably more applicable to the inpatient setting than interventions to be initiated in the emergency department.
Takeaway 5: Initiation of TTM in the out-of-hospital setting by EMS (with cooled saline boluses or other methods) is unlikely to add benefit to hospital-based TTM
Five Class I studies of moderate size failed to demonstrate benefit for out-of-hospital cooling when compared to initiation of cooling upon hospital arrival.
It is critical for emergency physicians to be familiar with their own center’s capabilities for TTM, and emergency physicians should work with other parties at their institution (ie, cardiology, neurology, and critical care) to create protocols and agreements to help facilitate effective TTM after ROSC for OHCA patients. Further research is needed to determine the optimal timing for initiation and the duration of TTM.
- McNally B, Robb R, Mehta M, et al. Out-of-hospital cardiac arrest surveillance—Cardiac Arrest Registry to Enhance Survival (CARES), United States, October 1, 2005–December 31, 2010. MMWR Surveill Summ. 2011;60(8):1-19.
- Geocadin RG, Wijdicks E, Armstrong MJ, et al. Practice guideline summary: reducing brain injury following cardiopulmonary resuscitation: report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology. Neurology. 2017;88(22):2141-2149.
- Hypothermia after Cardiac Arrest Study Group. Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. N Engl J Med. 2002;346(8):549-556.
- Lopez-de-Sa E, Rey JR, Armada E, et al. Hypothermia in comatose survivors from out-of-hospital cardiac arrest: pilot trial comparing 2 levels of target temperature. Circulation. 2012;126(24):2826-2833.
- 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):2197-2206.