The goal of this observational study is to identify further pathophysiologic mechanism of secondary brain injury following cardiac arrest by using serial multiomics profiling of serum and cerebrospinal fluid (CSF) samples. The main question it aims to answer is:

A. The main question it aims to answer is: What are the dynamic molecular changes in serum and CSF that reflect the pathophysiological mechanisms of secondary brain injury after cardiac arrest? B. What are the differences in serum and CSF multiomic signatures between varying severities of cardiac arrest, and how are these differences associated with the underlying pathophysiological mechanisms of secondary brain injury?

Serum and CSF samples that have already been prospectively collected from participants and stored in the BioBank will be used for this analysis.

Inclusion Criteria:

• Age ≥ 18 years old
• Out-of-hospital cardiac arrest (OHCA)
• Patients who have received post-resuscitation care including temperature control due to unconsciousness (Glasgow Coma Score < 8) after sustained ROSC.
• Patients who consented to the placement of lumbar catheter for storing cerebrospinal fluid and blood samples in a human biobank.

Exclusion Criteria:

• Patients diagnosed with a central nervous system-related disease before cardiac arrest
• Patients who have undergone extracorporeal circulatory membrane oxygenation therapy
• Patients who died within 24 hours from post-resuscitation care

Adult patients with an out-of-hospital cardiac arrest who underwent post-resuscitation care

Individual participant data (IPD) will not be shared publicly due to ethical and privacy concerns. However, data sharing may be possible upon reasonable request with prior approval from the ethics committee and the principal investigator