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Time to start of cardiopulmonary resuscitation and the effect of target temperature management at 33°C and 36°C
Intensive Care Medicine Experimental volume 3, Article number: A844 (2015)
The optimal target temperature for comatose patients resuscitated from out of hospital cardiac arrest is unknown. It has been hypothesized that patients with long no-flow times, for example those without bystander CPR would have the most to gain from temperature management at lower temperatures . The generalizability of the TTM-trial  has been questioned because of a high fraction of patients receiving bystander cardiopulmonary resuscitation (CPR) (73%) and a median start of basic life support (for patients with bystander CPR) of 1 minute (Interquartile range 1-2 minutes).
The aim of this study was to explore any potential interaction between temperature and no-flow time to investigate whether patients who had longer periods of cerebral ischemia had a better response to the lower target temperature of 33°C in the TTM-trial .
We analysed data from an international clinical trial randomizing cardiac arrest patients to targeted temperature management at 33°C and 36°C for an interaction between no-flow time and intervention group, with neurological function at 180 days after cardiac arrest as the primary outcome. A cerebral performance category (CPC) score of 1 or 2 was considered a good outcome. The interaction term was included in a multivariate logistic model adjusting for design variables in the TTM-trial.
The interaction between no-flow time and temperature group was not significant. Adjusted predictions showed no difference in the probability of a good neurological outcome for any value of no-flow time (Fig 1). In the group of patients with more than eight minutes of no-flow time the difference in the average predicted probability of a poor outcome was -0.018 (95% CI -0.17 - 0.13, p = 0.81) i.e. a non-significant decrease of 1.8% in the probability of a poor neurological outcome for patients treated at 36°C.
The neutral effect of the two temperature levels was consistent for all no-flow times.
The hypothesis that the efficacy of target temperature at 33°C vs. 36°C is influenced by no-flow time could not be supported.
Supported by independent research grants from the Swedish Heart-Lung Foundation, Arbetsmarknadens Försäkringsaktiebolag Insurance Foundation, Swedish Research Council, Region Skåne (Sweden), Skåne University Hospital, TrygFonden (Denmark), and European Clinical Research Infrastructures Network.
Testori C, et al: The beneficial effect of mild therapeutic hypothermia depends on the time of complete circulatory standstill in patients with cardiac arrest. Resuscitation. 2012, 83 (5): 596-601. 10.1016/j.resuscitation.2011.11.019.
Nielsen N, et al: Targeted Temperature Management at 33°C versus 36°C after Cardiac Arrest. New England Journal of Medicine. 2013
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Dankiewicz, J., Cronberg, T., Erlinge, D. et al. Time to start of cardiopulmonary resuscitation and the effect of target temperature management at 33°C and 36°C. ICMx 3, A844 (2015). https://doi.org/10.1186/2197-425X-3-S1-A844
- Cardiac Arrest
- Cardiopulmonary Resuscitation
- Cerebral Performance Category
- Basic Life Support
- Target Temperature Management