Unconscious survivors of cardiac arrest who are treated with intravenous therapeutic hypothermia for 24 hours will be assessed after 12 hours for appropriateness to be woken early and extubated whilst continuing to receive therapeutic hypothermia. Sedation will be reduced/stopped at 12 hours to enable a comprehensive neurological assessment utilising a multimodal approach.

Providing the patient is clinically stable with no adverse neurological signs the patient will be extubated. Patients who remain unconscious will be reviewed 6 hourly for neurological recovery and their suitability to be extubated in line with standard practice.

This study is a single centre, prospective, feasibility and safety study. Consecutively enrolling 50 patients. Subjects will include adult patients who have suffered a cardiac arrest with a return of spontaneous circulation (ROSC).

To qualify, patients must be unconscious and intubated because their initial Glasgow Coma Score (GCS) is <8. Intravenous therapeutic hypothermia (TH) will be established in the cathlab and maintained for 24 hours whilst being cared for in the intensive Care Unit (ICU). IVTM will maintain the patient's core temperature at a target temperature between 32-34 degrees Celsius. After the patient has received 12 hours of TH, sedation will be stopped and the patient will have a comprehensive neurological assessment combining electroencephalogram (EEG), Somatic Sensory Evoked Potential (SSEP) and neurological biomarkers, Neuron Specific Enolase (NSE) and S100b. The EEG, SSEP and biomarkers will be reviewed by an expert in neurophysiology at a core lab off-site. These results will be reviewed retrospectively, therefore will not influence the medical management of the patient.

Patients who are clinically stable and not showing any adverse neurological signs will be extubated after 12 hours. Patients who don't meet the early waking criteria will reassessed every 6 hours for extubation. Those patients who are not suitable to be woken early or remain unconscious after 24 hours will be reassessed as per standard practice for unconscious survivors of cardiac arrest.

Inclusion Criteria:

• Post cardiac arrest with ROSC
• Planning to receive MTH as part of post-cardiac arrest care

Exclusion Criteria:

• Cardiac arrest caused by trauma, head injury, massive haemorrhage, drug overdose, cerebrovascular accident, drowning, electric shock or hanging.
• Do Not Attempt to Resuscitate (DNAR) orders
• Known terminal illness (e.g. malignancy in the end stages)
• Known or obvious pregnancy
• Known coagulation disorder (except those induced by medication)
• Known oxygen dependency
• The patient has a height of <1.5 meters (4 feet 11 inches)
• The patient has a known hypersensitivity to Buspirone Hydrochloride or Pethidine
• Patient has a known history of severe hepatic or renal impairment, untreated hypothyroidism, Addison's disease, benign prostatic hypertrophy, or urethral stricture that in the opinion of the treating consultant would be incompatible with Pethidine administration
• The patient has an inferior Vena Cava (IVC) filter in place
• The patient has a known, unresolved history of drug use or alcohol dependency, or lacks the ability to comprehend or follow instructions

Cardiac arrest