Time to start of cardiopulmonary resuscitation and the effect of target temperature management at 33°C and 36°C.

Introduction: The optimal temperature during targeted temperature management (TTM) 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.

Methods: 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 six months after cardiac arrest as the primary outcome. A cerebral performance category (CPC) score of 1 or 2 was considered a good outcome.

Results: No-flow time (min) was associated with poor neurological outcome (OR 1.13, 95% confidence interval 1.06-1.20, p<0.001). There was no statistically significant interaction between no flow-time and intervention group (p=0.11), which may imply that the non-superior effect of 33°C was consistent for all no-flow times. Bystander CPR was not independently associated with neurological function.

Conclusions: TTM at 33°C compared to 36°C was not associated with an increased probability of a good neurological function for patients with longer no-flow times.