The use of protective ventilation (to maintain normoxia and normocapnia), optimise haemodynamics, diagnose/treat seizures, therapeutic hypotermia etc is recommended for ICU management of patients who have had cardiac arrest and remain in coma after return of spontaneous circulation according to the latest International Guidelines. These actions essentially aim to limit secondary brain injury but despite all therapeutic effort, the cerebral oxygenation may remain inadequate and there is no validated method to avoid such a state in real time.

The use of protective ventilation (to maintain normoxia and normocapnia), optimize hemodynamics, diagnose/treat seizures, therapeutic hypothermia etc is recommended for ICU management of patients who have had cardiac arrest and remain in a coma after the return of spontaneous circulation according to the latest International Guidelines. These actions essentially aim to limit secondary brain injury but despite all therapeutic effort, the cerebral oxygenation may remain inadequate and there is no validated method to avoid such a state in real time.

The objective of this study is to assess the relationship between jugular venous oximetry and neurological outcome of comatose patients after cardiac arrest, evaluated as per the Cerebral Performance Category scale (CPC). Further, the aim is to clarify relations between biomarkers protein S100B, neuron-specific enolase (NSE) and parameters of jugular oximetry for prognostication. An anticipated total of sixty patients will be enrolled in this non-randomised, single-group, double-blind study.

In the course of the study, the authors have decided to stop using BIS monitoring for sedation management. Reason for this decision was very limited reliability of this technique in unparalyzed patients on ICU (muscle artifacts). New aim of sedation was Richmond Agitation Sedation Scale (RASS) -4 or -5, with avoiding shivering and clinically manifested seizures.

Inclusion Criteria:

• age 18 or older
• successful cardiopulmonary resuscitation
• persistent coma defined as: no eye opening to voice and inability to follow commands

Exclusion Criteria:

• pre-existing "do not resuscitate" status
• severe coexisting systemic disease with a limited life expectancy
• pregnancy
• patients who will die within 72 h of the initial cardiac arrest

Consecutive out-of-hospital, post-cardiac arrest patients who remain comatose after successful resuscitation, admitted on ICU University Hospital Ostrava will be enrolled into the study.

Individual participant data will not be made available. The results of the study will be published in an impact factor journal.