What are the steps for brain stem testing in a patient with suspected brain death?

Brain Stem Testing for Brain Death Determination

Brain death determination requires a systematic clinical examination of brainstem reflexes performed twice by different attending physicians, separated by an observation period, with apnea testing completed during each examination. 1, 2

Prerequisites Before Testing

Before initiating brainstem testing, you must establish and document the following:

• Identify an irreversible, known cause of coma (e.g., traumatic brain injury, intracranial hemorrhage, anoxic injury) 1, 2
• Normalize core temperature to >35°C to avoid hypothermia confounding the examination 1, 2
• Correct hypotension and ensure adequate blood pressure for the patient's age 1, 2
• Correct metabolic disturbances including severe electrolyte abnormalities, acid-base disorders, and endocrine dysfunction 2
• Discontinue or ensure clearance of sedatives, analgesics, neuromuscular blockers, and anticonvulsants for an appropriate duration based on elimination half-lives, with medication levels in low to mid-therapeutic range if present 1, 2

Clinical Examination Components

1. Coma Assessment

• Document complete loss of consciousness, vocalization, and volitional activity 1
• Confirm absence of eye opening or eye movement to noxious stimuli applied to multiple sites 1
• Verify that noxious stimuli produce no motor response other than spinally mediated reflexes (requires expertise to differentiate) 1

2. Brainstem Reflex Testing

Pupillary reflex:

• Pupils must be midposition or fully dilated (4-9 mm) and non-reactive to bright light in both eyes 1
• Use a magnifying glass if uncertainty exists about pupillary response 1

Corneal reflex:

• Touch the cornea with tissue paper, cotton swab, or squirts of water 1
• No eyelid movement should occur; avoid corneal damage during testing 1

Facial movement and grimacing:

• Apply deep pressure to the temporomandibular joint condyles and supraorbital ridge 1
• No grimacing or facial muscle movement should be observed 1

Gag and cough reflexes:

• Test pharyngeal reflex by stimulating the posterior pharynx with a tongue blade or suction device 1
• Test tracheal reflex by inserting a suction catheter to the carina and performing 1-2 suctioning passes 1
• No gag, cough, sucking, or rooting reflex should be present 1

Oculovestibular reflex (caloric testing):

• Confirm patency of external auditory canals bilaterally 1
• Elevate the head to 30 degrees 1
• Irrigate each ear separately with 10-50 mL of ice water, waiting several minutes between sides 1
• No eye movement should occur during 1 minute of observation after each irrigation 1

3. Apnea Testing Procedure

This is a critical component that must be performed with each neurologic examination unless medically contraindicated. 1, 2

Pre-test preparation:

• Pre-oxygenate with 100% oxygen for 5-10 minutes 2
• Obtain baseline arterial blood gas to document starting PaCO₂ 1, 2
• Ensure hemodynamic stability and oxygen saturation >85% before starting 1

Testing procedure:

• Disconnect the patient from the ventilator while providing oxygen via tracheal catheter or T-piece 1, 2
• Continuously monitor heart rate, blood pressure, and oxygen saturation throughout 1
• Observe for any spontaneous respiratory effort 1, 2
• Allow PaCO₂ to rise to ≥60 mm Hg AND ≥20 mm Hg above baseline 1, 2
• Obtain arterial blood gas to confirm PaCO₂ levels 1, 2

Test interpretation:

• If no respiratory effort occurs when PaCO₂ reaches ≥60 mm Hg and ≥20 mm Hg above baseline, the apnea test is consistent with brain death 1, 2
• If oxygen saturation falls below 85% or hemodynamic instability occurs, abort the test and consider ancillary testing 1

Important caveat: Contraindications to apnea testing include high cervical spine injury, high oxygen requirements, or conditions that invalidate the test; in these cases, ancillary studies must be used 1, 2

Observation Period and Repeat Examination

• For neonates (37 weeks to 30 days): 24-hour observation period between examinations 1
• For infants and children (>30 days to 18 years): 12-hour observation period between examinations 1
• The second examination confirms brain death based on unchanged and irreversible condition 1

Ancillary Testing (When Needed)

Ancillary studies are NOT required for brain death determination but may be used when: 1, 2

• Components of the clinical examination cannot be completed safely 1, 2
• Uncertainty exists about examination results 1, 2
• Medication effects may be present 1, 2
• Apnea testing cannot be performed or completed 1, 2

Accepted ancillary tests include: 1, 2

• Electroencephalogram (EEG) demonstrating electrocerebral silence 1, 2
• Cerebral blood flow studies (four-vessel angiography or radionuclide studies) showing absent cerebral blood flow 1, 2

Documentation Requirements

Document comprehensively: 2

• All prerequisites met and confounding factors addressed 2
• Detailed findings of both neurological examinations 2
• Complete apnea testing results with specific PaCO₂ values 2
• When ancillary tests are used, document specific findings consistent with brain death 2

Common Pitfalls to Avoid

• Do not proceed with testing if any confounding factors remain uncorrected (hypothermia, hypotension, sedating medications) 2
• Spinal reflexes can persist after brain death; do not mistake these for retained brain function 1
• Ensure adequate PaCO₂ rise during apnea testing; inadequate hypercarbic stimulus invalidates the test 1
• Do not use CPAP mode during apnea testing as it may trigger false spontaneous breaths 1