From the Guidelines
Evaluating brain death in patients with spinal cord injury requires careful assessment to distinguish between neurological deficits due to the spinal injury and those indicating true brain death, with prerequisites including known irreversible cause of coma, normothermia, normal blood pressure, absence of confounding medications, and correction of metabolic disturbances, as recommended by the most recent guidelines 1. To determine brain death in a patient with a spinal cord injury, the following criteria should be evaluated:
- Known irreversible cause of coma
- Normothermia (>36°C)
- Normal blood pressure (systolic >100 mmHg)
- Absence of confounding medications (particularly neuromuscular blockers)
- Correction of metabolic disturbances The clinical examination should demonstrate:
- Coma with absence of cerebral responses
- Brainstem areflexia (including absent pupillary, corneal, oculocephalic, oculovestibular, and gag reflexes)
- Apnea When testing for apnea, preoxygenate with 100% oxygen for 10 minutes, disconnect the ventilator while providing oxygen via tracheal cannula at 6 L/min, and observe for respiratory movements while PaCO2 rises above 60 mmHg (confirmed by arterial blood gas) 2, 3. Spinal cord injury complicates this evaluation because it may cause loss of motor responses below the level of injury and can produce spinal reflexes that mimic voluntary movements. Therefore, ancillary testing is particularly important in these cases, with options including cerebral angiography, electroencephalography, transcranial Doppler, or nuclear medicine perfusion studies, as recommended by recent guidelines 1. Two separate examinations, typically 6-24 hours apart, by different physicians experienced in neurological assessment are recommended to confirm brain death in this challenging clinical scenario 2, 3.
From the Research
Criteria for Evaluating Brain Death
The criteria for evaluating brain death in a patient with a spinal cord injury (SCI) involve a combination of clinical examination and ancillary tests. The American Academy of Neurology (AAN) recommends the following clinical criteria to confirm brain death:
- Coma
- Absence of brainstem reflexes
- Apnea 4
Ancillary Tests
Ancillary tests are needed when neurologic examination or apnea test cannot be performed. The AAN recommended ancillary tests include:
- Electroencephalogram (EEG) to confirm electrical activity loss
- Catheter cerebral angiogram to confirm loss of cerebral blood flow
- Transcranial Doppler
- Nuclear scintigraphy 4
Spinal Cord Injuries and Brain Death
In patients with spinal cord injuries, decerebrate-like spinal reflexes may emerge after brain death, which can be confused with brain stem reflexes and delay the diagnosis of brain death. However, these movements can be attributed to spinal cord reflexes and should not delay the diagnosis or necessitate confirmatory testing 5
Neurophysiologic Testing
Neurophysiologic testing, such as EEG and evoked potentials, can support the clinical diagnosis of brain death, especially in cases where the clinical examination findings are equivocal or cannot be performed 6
Confounding Factors
Confounding factors, such as therapeutic hypothermia, high-dose metabolic suppression, and movements associated with complex spinal reflexes, can delay the initiation or completion of brain death protocols. Neurodiagnostic studies, such as 4-vessel cerebral angiography, can rapidly document absence of blood flow to the brain and decrease intervals between onset of terminal brain stem herniation and formal declaration of death by neurological criteria 7
International Guidelines
There is variability in brain death determination worldwide, but international multidisciplinary collaboration has been created to harmonize the criteria and improve public trust in the process and diagnosis. Minimum criteria have been published, and guidance has been provided for professionals to revise or develop guidelines on brain death worldwide 8