Sam Parnia

Years since first academic appointment: 6 – 15 years

Title: AWARE II (AWAreness during REsuscitation) – A Multi-Centre Observational Study of the Relationship between the Quality of Brain Resuscitation, and Consciousness, Neurological, Functional and Cognitive Outcomes following Cardiac Arrest

INTRODUCTION: Although historically a terminal event, resuscitation after cardiac arrest (CA) is increasingly possible even after prolonged periods of time. However due to ischemia/reperfusion injury and the resultant neurological and neuropsychological deficits, only 3-7% of survivors recover to their pre-CA functional status. Neuropsychological deficits include memory impairment, depression, and post-traumatic stress disorder. By contrast, paradoxically up to 20% of survivors may report a positive long-term psychological effect in conjunction with a reported perception of conscious awareness and/or mental and cognitive activity during CA. We and others have demonstrated that the quality of cerebral oxygenation (rSO2) as measured by cerebral oximetry during CPR is associated with survival and neurological outcomes. In another study of >2000 subjects with CA,  we also found that despite absent clinical signs of consciousness, 39% of survivors reported a perception of awareness without explicit memory recall of CA events, while 10% recalled specific memories and 2% reported full awareness during CPR. As long-term neurological disorders and disorders of consciousness likely relate to the quality of brain resuscitation during CPR, an understanding of the relationship between the quality of brain resuscitation, neurological status and consciousness, is an important step. Our goal is to develop a novel monitoring method aimed at measuring oxygen delivery to the brain and other vital organs during CA. We also aim to further explore the mechanisms of consciousness and awareness during CPR. We hypothesize that by limiting ischemia during resuscitation, higher cerebral oxygenation during CPR is associated with survival as well as favorable neurological and neuropsychological outcomes. We further hypothesize that mental and cognitive activity and awareness during CPR reflects the quality of brain resuscitation.

OBJECTIVES: 1) Determine the relationship between brain oxygenation (using cerebral oximetry) and function (using portable EEG) during CA and survival with favourable neurological outcomes 2) Evaluate the qualitative nature of patients’ experiences and cognitive activity during CA 3) Assess the relationship between quality of brain resuscitation and conscious awareness during CPR.

METHODS: This is a prospective, multi-centre, observational study of adult, in-hospital CA patients. During CPR, continuous cerebral oximetry, EEG, and end tidal CO2 (ETCO2) monitoring is applied. We apply a portable tablet computer to portray audio/visual stimuli to assess levels of consciousness. Data collected is uploaded to an electronic database for storage and analysis independent of survival status. Accuracy of claims of visual and auditory awareness are examined using specific recall tests. Survivors are followed up at 30 days to examine neurological, functional and cognitive outcomes.

IMPACT ON EMERGENCY MEDICINE: Brain resuscitation monitoring will likely aid overall prognostication. Such a system will also enable physicians to quantify ischemia in real-time and implement interventions aimed at augmenting brain resuscitation. Understanding the mechanisms of consciousness and awareness during CA may elucidate the mechanisms underpinning the observed post-resuscitation neuropsychological outcomes.

Three Questions for Audience

  • What is the relationship between cerebral oxygenation during CPR and survival and neurological outcomes following CA?
  • What is the prevalence of consciousness and awareness during CPR?
  • What is the feasibility of measuring brain function during CPR?