Neurocrit Care DOI 10.1007/s12028-015-0184-z ORIGINAL ARTICLE Therapeutic Hypothermia After Resuscitation From a Non-Shockable Rhythm Improves Outcomes in a Regionalized System of Cardiac Arrest Care 1 2,3,4 2,3 5 Gene Sung • Nichole Bosson • Amy H. Kaji • Mark Eckstein • 6 3,7 3,7 David Shavelle • William J. French • Joseph L. Thomas • 4 2,3 William Koenig • James T. Niemann Ó Springer Science+Business Media New York 2015 Abstract preexisting coma or death prior to initiation. The decision Objective Therapeutic hypothermia (TH) improves neu- to initiate TH was determined by the treating physician. rologic outcome in patients resuscitated from ventricular Measurements The primary outcome was survival with fibrillation. The purpose of this study was to evaluate TH good neurologic outcome defined by a cerebral perfor- effects on neurologic outcome in patients resuscitated from mance category of 1 or 2. a non-shockable out-of-hospital cardiac arrest rhythm. Main Results Of the 2772 patients treated for cardiac Design and Setting This is a retrospective cohort study of arrest during the study period, there were 1713 patients data reported to a registry in an emergency medical system resuscitated from cardiac arrest with an initial non-shock- in a large metropolitan region. Patients achieving field able rhythm and 1432 patients met inclusion criteria. The return of spontaneous circulation are transported to desig- median age was 69 years [IQR 59–82]; 802 (56 %) male. nated hospitals with TH protocols. TH was induced in 596 (42 %) patients. Survival with good Patients Patients with an initial non-shockable rhythm neurologic outcome was 14 % in the group receiving TH, were identified. Patients were excluded if awake in the compared with 5 % in those not treated with TH (risk Emergency Department or if TH was withheld due to difference = 8 %, 95 % CI 5–12 %). The adjusted OR for a CPC 1 or 2 with TH was 2.9 (95 % CI 1.9–4.4). Conclusion Analyzing the data collected from the reg- & Gene Sung [email protected] istry of the standard practice in a large metropolitan region, TH is associated with improved neurologic outcome in 1 Department of Neurology, Keck School of Medicine of the patients resuscitated from initial non-shockable rhythms in University of Southern California, 1520 San Pablo St, Ste a regionalized system for post-resuscitation care. 3000, Los Angeles, CA 90033, USA 2 Department of Emergency Medicine, Harbor-UCLA Medical Keywords Therapeutic hypothermia Á Cardiac arrest Á Center, Los Angeles Biomedical Research Institute at Harbor-UCLA, Torrance, CA, USA Resuscitation 3 David Geffen School of Medicine at UCLA, Los Angeles, CA, USA Introduction 4 Los Angeles County Emergency Medical Services Agency, Los Angeles, CA, USA 5 Therapeutic hypothermia (TH) is a proven intervention that Department of Emergency Medicine, Keck School of improves neurologic outcomes after successful resuscita- Medicine of the University of Southern California, Los Angeles, CA, USA tion from out-of-hospital cardiac arrest (OHCA) with initial shockable rhythm. [1, 2] The International Liaison 6 Department of Cardiology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA Committee on Resuscitation supports the use of TH in patients after OHCA with an initial rhythm of ventricular 7 Department of Cardiology, Harbor-UCLA Medical Center, Los Angeles Biomedical Research Institute at Harbor-UCLA, fibrillation, and state that, while TH may be beneficial for Torrance, CA, USA other rhythms, further study is required in non-shockable 123 Neurocrit Care rhythms. [3] The proposed mechanism by which TH cardiac etiology with ROSC in the field to a cardiac arrest improves outcomes includes reducing cerebral reperfusion center with an institutionally approved hypothermia pro- injury by decreasing oxygen demand, glutamate release, tocol. Participating hospitals were encouraged to institute and production of free radicals. [1, 3] Cerebral reperfusion TH (target temperature 32–34 °C) within 6 h of ROSC and injury is applicable to all patients suffering cardiac arrest. to maintain it for a minimum of 20 h. The final decision to However, given the lower survival rates and higher initiate or withhold TH was guided by particular institu- potential for comorbidities in patients with non-shockable tional policy and at the discretion of the treating physician, rhythms, the degree to which TH may be beneficial for and TH was not initiated in the field. Six of the 33 cardiac these patients remains unclear. Small observational studies arrest centers have policies that specifically limit TH to that include patients with non-shockable rhythms demon- patients presenting with a shockable rhythm. strated safety and suggest that there may be a survival Per LA County EMS policy, resuscitation on scene to benefit in all rhythms. [4–8] The benefit was not consis- achieve ROSC prior to transport is encouraged. For tently seen when non-shockable rhythms were isolated, patients meeting criteria, termination of resuscitation in the causing some to question benefit in these cases, though field is supported by official policy since 2007. Termina- these results were possibly due to small sample size. [9–12] tion of resuscitation is based on medical futility determined While patients resuscitated after non-shockable cardiac by paramedics in consultation with the base hospital arrest rhythms may benefit from the neuroprotective physician and agreement of immediate family on scene. properties of cooling, hypothermia has known risks Since April 2011, all cardiac arrest centers have reported including dysrhythmias, coagulopathy, and infection. In their in-hospital mortality and neurologic outcome to a addition, it is resource intensive. Finally, there remains the single registry maintained by the LA County EMS Agency. possibility that TH may improve survival in this group of The database was queried from April 2011 through August patients without improving neurologic outcome, resulting 2013, representing all available data at the time of analysis. in more patients surviving severely dependent or moribund. Patients 18 years or older resuscitated from OOHCA with This study reports the results of the largest series of non- an initial non-shockable rhythm transported to a designated shockable rhythm patients in a registry of one of the largest cardiac arrest center were included. Non-shockable rhythm metropolitan regions in the world. It utilizes the regional- refers to the first rhythm noted by prehospital personnel ized care system for OHCA in Los Angeles County and its and includes PEA and asystole, as well as patients analyzed standard practices, with a centralized database of patient by an automated external defibrillator that advised no outcomes, to assess neurologic outcome in patients treated shock. Patients with traumatic cardiac arrest and with TH after successful resuscitation from OHCA with an patients <18 years of age were excluded. Additionally, initial rhythm of pulseless electrical activity (PEA) or patients who would not benefit from TH were excluded asystole compared to those patients not treated with TH. from the analysis in order to mitigate the selection bias toward or against TH given the observational design of the study. This included the following: patients awake and alert Materials and Methods in the emergency department, patients with prior coma, and patients who died prior to consideration for TH. (Fig. 1) Los Angeles County is a large metropolis with a population Finally, patients with termination of resuscitation in the of over 13 million. Emergency medical services (EMS) are field were not transported by protocol and, therefore, were provided by 32 municipal fire departments, one law not eligible for inclusion in the database. enforcement agency, and 25 private ambulance companies Study variables included age, gender, race/ethnicity, with over 3500 licensed paramedics throughout the county. initial cardiac rhythm, arrest location, witness, bystander Patients who call 911 are transported to one of 72 emer- CPR, vasopressor support, induction of hypothermia, rea- gency departments in the county. The LA County EMS son hypothermia was withheld (if applicable), and whether Agency provides oversight of providers operating within the patient received cardiac catheterization with or without the county, establishes protocols and procedures, and des- PCI. The primary outcome of the study was survival to ignates specialty care centers. This is a retrospective study hospital discharge with good neurologic outcome, as of data from a registry maintained by the LA County EMS defined by a cerebral performance category (CPC) score at Agency. The study was reviewed and approved with waiver hospital discharge of 1 or 2. A CPC of 1 corresponds to a of informed consent by the institutional review board. return to normal or mildly impaired cerebral function and The system of regionalized cardiac care in LA County, independence with activities of daily living. A CPC of 2 with 33 designated cardiac arrest receiving centers, has corresponds to moderate cerebral disability but sufficient been described previously. [13] Countywide protocols function to remain independent with activities of daily mandate transport of all OOHCA patients of presumed living. The CPC scores documented by physician 123 Neurocrit Care calculated to evaluate each model. Mean CPC score out- comes among hospitals were compared with ANOVA. Results Of the 2772 patients treated for cardiac arrest during the study