How does the length of cardiopulmonary resuscitation affect brain damage in patients surviving cardiac arrest? A systematic review

Background: Brain injury can occur after cardiac arrest due to the effects of ischaemia and reperfusion. In serious cases this can lead to permanent disability. This risk must be considered when making decisions about terminating resuscitation. There are very specific rules for termination of resuscitation in the prehospital setting however a similar rule for resuscitation in hospital does not exist. The aim of this review was to explore the effects of duration of cardiopulmonary resuscitation on neurological outcome in survivors of both in-hospital and out-of-hospital cardiac arrest achieving return of spontaneous circulation in hospital. Methods: A systematic review was conducted. Five databases were searched in addition to hand searching the journals Resuscitation and Circulation and reference lists, quality of the selected studies was assessed and a narrative summary of the data presented. Studies reporting relevant outcomes were included if the participants were adults achieving return of spontaneous circulation in the hospital setting. Studies looking at additional interventions such as extracorporeal resuscitation and therapeutic hypothermia were not included. Case studies were excluded. The study period was from January 2010 to March 2016. Results: Seven cohort studies were included for review. Quality scores ranged from eight to 11 out of 12. Five of the studies found a significant association between shorter duration of resuscitation and favourable neurological outcome. Conclusions: There is generally a better neurological outcome with a shorter duration of CPR in survivors of cardiac arrest however a cut-off beyond which resuscitation is likely to lead to unfavourable outcome could not be determined and is unlikely to exist. The findings of this review could be considered by clinicians making decisions about terminating resuscitation. This review has highlighted many gaps in the knowledge where future research is needed; a validated and reliable measure of neurological outcome following cardiac arrest, more focused research on the effects of duration on neurological outcome and further research into the factors leading to brain damage in cardiac arrest.