Assessing brain injury after cardiac arrest, towards a quantitative approach

Withdrawal of life-sustaining therapy due to a presumed poor neurological prognosis precedes most deaths in patients who have been resuscitated after an out-of-hospital cardiac arrest and are being treated in an ICU. Guidelines to support these critical decisions recommend a multimodal strategy based on advanced diagnostic methods. This review will discuss clinical experience with the 2015 guidelines and recent developments towards more accurate quantification of posthypoxic brain injury.

Qualitative assessment of clinical findings, neurophysiological signals and radiological images are prone to error due to the individual assessors' experience and competence. Currently, the only quantitative method for assessment of postarrest brain injury in regular clinical use is the measurement of neuron-specific enolase in serum. Since 2015 several promising methods to standardize assessment have been introduced including pupillometry, standardized electroencephalography interpretation and the quantification of somatosensory evoked potentials, computed tomography and MRI-signals. In addition, novel and superior blood biomarkers are on the verge of clinical introduction.

The current guidelines for neuroprognostication include a step-by-step multimodal algorithm but many patients will still be left with an uncertain prognosis 4-5 days after cardiac arrest. Novel quantitative methods are a necessary step to a more nuanced prediction of outcome for this group of patients.