Prerequisites:
Clinical Criteria
Core temperature >32 C (actual temperature value > 32 varies by institution) with corrected electrolytes
> 36.5 C is preferred
SBP >90
Nl PaCO2 (>40)
Nl PaO2 (preoxygenate >200)
Test:
Check baseline ABG (ensure PaCO2 < 40 mmHg to maximize target PaCO2 rise)
Connect pulse ox, disconnect ventilator, place nasal cannula in ET (at carrina), and place on 100% O2 at 6 LPM
Physician able to declare<unk>  (typically neurology/neurosurgery) will  observe for respiratory movements
Draw ABG at 8 min. Observe for PaCO2 rise >20 mmHg over 8 minutes with no respiratory movement →positive apnea test (supports<unk> 
Positive test = 20 increase over baseline (typically 60) ensure to blow down CO2 to ~40 to enable 20 mmHg rise. Typical rise is 3 mmHg per minute
Considerations
Abort the test (reconnect ventilator) if SBP <90 or significant SpO2 desat (can draw ABG at that time, with same criteria as above)
Must perform 2 exams 6 hours apart in addition to apnea test
Clinical Criteria
Core temperature >32 C (actual temperature value > 32 varies by institution) with corrected electrolytes
> 36.5 C is preferred
SBP >90
Nl PaCO2 (>40)
Nl PaO2 (preoxygenate >200)
Check baseline ABG (ensure PaCO2 < 40 mmHg to maximize target PaCO2 rise)
Connect pulse ox, disconnect ventilator, place nasal cannula in ET (at carrina), and place on 100% O2 at 6 LPM
Physician able to declare<unk>  (typically neurology/neurosurgery) will  observe for respiratory movements
Draw ABG at 8 min. Observe for PaCO2 rise >20 mmHg over 8 minutes with no respiratory movement →positive apnea test (supports<unk> 
Positive test = 20 increase over baseline (typically 60) ensure to blow down CO2 to ~40 to enable 20 mmHg rise. Typical rise is 3 mmHg per minute
Positive test = 20 increase over baseline (typically 60) ensure to blow down CO2 to ~40 to enable 20 mmHg rise. Typical rise is 3 mmHg per minute
Abort the test (reconnect ventilator) if SBP <90 or significant SpO2 desat (can draw ABG at that time, with same criteria as above)
Must perform 2 exams 6 hours apart in addition to apnea test
Brain death
Spinal shock
Hemorrhagic shock
Neurogenic shock
Heat exhaustion
Heat stroke
Stroke 
Tumor lysis syndrome