Abstract 136: Longer Durations of CPR Decrease the Effect of Post--Cardiac Arrest Mild Therapeutic Hypothermia for Good Neurological Outcome
Introduction: Ischemia/Reperfusion injury is known as the primary mechanism leading to neurological injury in patients after cardiac arrest. Even a low-flow state, generated by resuscitation efforts, may already initiate deleterious cascades leading to cell death.We hypothesized, that a longer duration of normothermic “low-flow”-state enforces reperfusion damage and therefore is associated with less beneficial effects derived from mild therapeutic hypothermia (MTH) initiated after restoration of spontaneous circulation.
Material and Methods: We retrospectively analyzed data collected between 1992 and 2010 from adult patients successfully resuscitated from witnessed out-of-hospital cardiac arrest. The main risk factor was receiving MTH or not. Time from start of resuscitation efforts until restoration of spontaneous circulation (“low-flow”-state) was a priori grouped into quartiles (Quartile 1: 0-11min; Quartile 2: 12-17min; Quartile 3: 18-28min; Quartile 4:>29min). Best neurologic function (CPC 1 or 2) within 6 month served as primary endpoint.
Results: Out of 1.103 patients included in our analysis 613 patient (56%) were treated with MTH and were compared with 490 patients (44%) without MTH treatment. In general MTH was associated with better neurologic outcomes (54% vs. 35%; p <0.001). By comparing the time-quartiles of the “low-flow” states we found a declining benefit derived from MTH (Quartile 1: Odds Ratio 2.89 (95% CI adjusted) ; Quartile 4: Odds Ratio 0.73 (95% CI adjusted)).
Conclusion: Our results may indicate that reperfusion injury already begins during “low-flow” and becomes irreversible during a prolonged period of marginal circulation. This could explain our results showing that MTH is more effective in patients with faster circulatory stabilization. Therefore hypothermia maybe should already be initiated during early stages of “low-flow” or even earlier just before reperfusion to gain maximum benefit.
Author Disclosures: C. Wallmüller: None. P. Stratil: None. F. Sterz: None. H. Herkner: None. A. Schober: None. P. Hubner: None. S. Mathias: None. C. Testori: None.
- © 2014 by American Heart Association, Inc.