IMPORTANCE: Point-of-care, non-invasive brain monitoring in critically ill patients following cardiac arrest could provide earlier detection of neurological injury and, when combined with earlier treatments, limit brain injury. Point-of-care monitoring could also enable better neuro-prognostication. OBJECTIVES: The study assessed the time to detection of brain injury using optical brain pulse monitoring (OBPM) compared to routine brain monitoring. The association of OBPM signals with more severe forms of brain injury was also assessed. DESIGN: Retrospective analysis of patients enrolled in an observational study. SETTING: Critical care unit of a tertiary academic hospital. PARTICIPANTS: Adult patients requiring mechanical ventilation in a critical care unit following a cardiac arrest. MAIN OUTCOMES AND MEASURES: OBPM uses red and infrared light to capture brain pulse waveforms whose morphology reflects the relative arteriole and venous pressure levels driving microvascular blood flow in the brain. The OBPM sensors were placed bilaterally on the anterior temporal region of the scalp, over the middle cerebral artery territories. Time to brain injury detection was defined as the period from cardiac arrest to the first detection of brain injury by OBPM or routine monitoring. RESULTS: Twelve patients were enrolled, three required veno-arterial extra-corporeal membrane oxygenator support. In-hospital mortality was 83% and eight patients developed global hypoxic-ischemic brain injury. The median time to detection of brain injury was 57 hours earlier using OBPM compared to routine monitoring (P < 0.01). In brain injured patients OBPM brain pulse morphologies changed over time and were often different between hemispheres, high amplitude respiratory waves were also present. Known poor prognostic brain pulse waveform morphologies were present in some patients with severe brain injury. CONCLUSIONS AND RELEVANCE: OBPM detected brain injury earlier compared to routine brain monitoring. Earlier detection of neurological injury could improve patient outcomes through earlier treatment and better neuro-prognostication.

BD is the founder and Chief Scientific Officer of Cyban Pty Ltd the company that developed the monitor used in this study. EJT JH SP and SWC are employees of Cyban Pty Ltd. St Vincents Hospital Department of Critical Care Medicine and The Alfred Hospital Department of Critical Care Medicine received financial support from Cyban Pty Ltd to conduct this study. PS declares no competing interests.

ACTRN12620000828921

https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=379639&isReview=true

BioMedTech Horizons Program, MTP Connect. Australian Federal Government

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethics Approval Statement: Ethical approval for the Transcutaneous Pulse Oximetry (T-POT) study was granted by the Human Research Ethics Committee (HREC) of St Vincents Hospital Melbourne Australia (HREC 160/20; Project ID 63147) on December 14, 2021. The trial is registered under ACTRN12620000828921. As participants lacked the capacity to provide informed consent at the time of eligibility, consent was obtained from their medical treatment decision maker. This study was conducted in accordance with the Declaration of Helsinki and followed all relevant institutional guidelines and regulations.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All data produced in the present work are contained in the manuscript