The majority of cardiac arrest survivors have some degree of brain injury and impaired consciousness. Some remain in a persistent vegetative state. Determining the survivor's prognosis and deciding whether to treat or withdraw care is complicated and based on many variables (many of which haven't been thoroughly studied).
Factors before cardiac arrest:
- Poor health including diabetes, cancer, infection, kidney disease and stroke
Factors during cardiac arrest:
- Time between collapse and start of CPR/defibrillation
- Quality of CPR/defibrillation
- Whether survivor had neurological function during or immediately after CPR
Factors after cardiac arrest and resuscitation:
- Neurological function: Generally, poor function equals poor prognosis. But it could be complicated by medical instability and treatments. Some patients suffer a stroke after a cardiac arrest.
- Neurophysiologic function: Tests include somatosensory evoked potentials (SSEP) and electroencephalogram (EEG).
- Neuroimaging and monitoring: Cranial CT, MRI, magnetic resonance spectroscopy and positron emission tomography (PET) determine structural brain injury, mostly to exclude hemorrhage or stroke.
- Biochemistry: from blood or cerebrospinal fluid
- Therapeutic hypothermia: Intentionally lowering the patient's body temperature.