Abstract 317: Effect of Intra-arrest Induction of Therapeutic Hypothermia on Out-of-Hospital Cardiac Arrest

Introduction: The resuscitation literature has recently suggested that the prehospital initiation of therapeutic hypothermia following successful resuscitation does not alter outcomes among patients who suffer sudden out-of-hospital cardiac arrest (OOHCA). We sought to assess the impact of earlier, intra-arrest induction of therapeutic hypothermia on OOHCA survival. Methodology: Out-of-hospital cardiac arrest data from two consecutive twelve-month periods was analyzed: August 1, 2009 - July 31, 2010 (Phase I), August 1, 2010 - July 31, 2011 (Phase II). In Phase I, paramedics in this urban system transported OOHCA patient to participating Cardiac Arrest Centers where the use of therapeutic hypothermia had been incorporated to the standard post-resuscitation care pathway. In Phase II, paramedics initiated hypothermia during the initial resuscitation effort through the rapid infusion of large-volume, ice-cold saline. Consistent with the Utstein definitions, analyses utilized only those cases which were bystander witnessed and of cardiac etiology. Results: There were 1,487 and 850 bystander witnessed arrests of cardiac etiology in the two phases. Patient and arrest characteristics for the two groups did not differ with respect to age, gender, race, response time, bystander witnessed status, or the frequency of bystander CPR. Return of spontaneous circulation (ROSC), sustained ROSC, survival to hospital admission and survival to hospital discharge did not differ significantly from Phase I to Phase II: 40.82% vs 39.59% (p=.54), 31.10% vs 31.17% (p=0.58), 27.15% vs 24.88% (p=0.27), and 6.62% vs 6.19% (p=0.41). In addition, among those survivors for whom neurologic status is known, the intra-arrest initiation of therapeutic hypothermia did not significantly change the proportion of survivors considered neurologically intact (76.47% vs 70.37%, all p=0.59). Conclusions: The intra-arrest initiation of therapeutic hypothermia did not alter outcomes among OOHCA patients, demonstrating neither harm nor benefit. Whether this is due to a lack of continuation of hypothermia following hospital admission or a true lack of benefit requires further collaborative work between the prehospital and hospital communities.