Rationale: An important proportion of patients with return of spontaneous circulation (ROSC) after cardiac arrest remain comatose as a result of post anoxic encephalopathy (PAE). Specific treatments to promote cerebral recovery are lacking. Early identification of patients without potential of recovery of brain functioning may prevent inappropriate continuation of medical treatment and improve communication between doctors and families. Intensivists currently use a combination of diagnostic measures, including brainstem reflexes, motor response, status myoclonus, SSEP measurements and (increasingly) the EEG. However, together all these measure identify only 20-50% of the patients with severe PAE precluding cerebral recovery. At the moment, there is a high demand for bedside measurements that contribute to the neurological prognostication of comatose patients after cardiac arrest. Non-invasive bedside measurements of the optic nerve sheath diameter (ONSD) using ultrasound hold potential to improve outcome prediction.

Objective: To estimate the value and feasibility of repetitive measurements of the ONSD in comatose patients after cardiac arrest.

Study design: Prospective cohort study

Study population: 160 subsequent comatose adult patients after cardiac arrest, admitted to the ICU of Rijnstate hospital

Intervention: In addition to standard treatments, patients will undergo ultrasonic measurements of the ONSD during the first 3 days after cardiac arrest. Survivors will be followed upon hospital discharge. ONSD measurements will be followed over time and related tot neurological outcome.

Main study parameters/endpoints: The primary outcome measure is neurological outcome, defined using the Cerebral Performance Category (CPC) score at 6 months. CPC 1-2 indicates favourable neurological outcome, and CPC 3-5 indicates unfavourable neurological outcome.

Inclusion Criteria:

• Age ≥ 18 years
• Cardiac arrest
• Admitted to the ICU with Glasgow Coma Scale ≤ 8

Exclusion Criteria:

• Pregnancy
• Traumatic head injury
• Eye surgery in medical history, including cataract surgery
• Pre-existing dependency in daily living (CPC 3 or 4)
• Any known progressive brain illness, such as a brain tumour or neurodegenerative disease

160 subsequent comatose adult patients after cardiac arrest, admitted to the ICU of Rijnstate hospital.