The ACEP Clinical Policies Committee regularly reviews guidelines published by other organizations and professional societies. Periodically, new guidelines are identified on topics with relevance to the clinical practice of emergency medicine. This article highlights recommendations for interventions to improve neurological outcomes in post–cardiac arrest patients, which were developed by the American Academy of Neurology (AAN).
Roughly 300,000 people suffer from out-of-hospital cardiac arrest (OHCA) each year in the United States, but only about 6 to 9 percent of patients survive to hospital discharge.1 Neurological injury remains a major determinate of morbidity and mortality in survivors. Targeted temperature management (TTM), which may include the avoidance of hyperthermia and therapeutic hypothermia, has been shown to improve neurological outcomes in post-arrest patients when initiated in the emergency department after return of spontaneous circulation (ROSC). In 2017, the AAN published a set of recommendations for management strategies to reduce neurological injury after cardiac arrest.2
The guidelines were developed from a systematic review and meta-analysis conducted by the AAN on literature from 1966 through August 2016. Below are highlights of their recommendations, focusing on aspects pertinent to emergency physicians.
Takeaway 1: Patients with atraumatic OHCA who are initially unresponsive after ROSC are likely to have lower mortality and better chances of favorable neurological outcomes if TTM is initiated.
This recommendation is supported by five Class I studies and multiple lower-quality studies demonstrating improved overall mortality and functional neurological outcomes in patients receiving some form of TTM. The benefits are greater for patients with an initial rhythm of ventricular tachycardia or ventricular fibrillation (VT/VF) compared to those with pulseless electrical activity (PEA)/asystole.
- Initial rhythm VT/VF: 16 percent more favorable neurological outcomes (95% CI; 4–27%) and 14 percent less mortality (95% CI; 3–26%) at six months.3
- Initial rhythm PEA/asystole: 6 percent more favorable neurological outcomes (95% CI; 3–9% percent) and 12 percent less mortality (95% CI; 8–16%) at hospital discharge.2
The number of post-OHCA patients needed to be treated (NNT) with cooling to benefit one patient with a positive neurologic outcome at six months is seven after VT/VF arrest and 17 after PEA/asystolic arrest.
Takeaway 2: At this time, no single temperature has been shown to be superior. Pick a temperature between 32°C and 36°C and stick with it.
While this is an ongoing area of research and a point of some debate among experts, the best evidence available has failed to show just how cold is “cold enough” for ideal TTM. In particular, one Class I study compared protocols based around 32°C versus 34°C, while another compared 33°C versus 36°C.4,5 Neither found a significant difference in major outcomes. For now, different hospitals will use different protocols, so emergency physicians should just be aware of the protocol at their center.