Disorders of Consciousness, Coma, and Determination of Death by Neurologic Criteria
Assessing the unresponsive patient
Distinguish coma, vegetative state (unresponsive wakefulness), minimally conscious state, locked-in syndrome, catatonia, and pharmacologic paralysis. The locked-in patient is awake with vertical eye movement despite quadriplegia. Use the Glasgow Coma Scale and know the FOUR score, which adds brainstem reflexes and respiration. Examine pupils, corneal, oculocephalic, gag, and cough reflexes and motor responses to pain, including spinal reflexes.
Determination of death by neurologic criteria
Establish a known, irreversible cause and exclude all confounders: sedation, neuromuscular blockade, hypothermia below 36 C, hypotension, and severe metabolic derangement. Then demonstrate unresponsiveness, absent pupillary, corneal, oculocephalic, gag and cough reflexes, and absent motor response to pain in the face, limbs, and torso (spinal reflexes may persist). Perform the apnea test after preoxygenation: disconnect from the ventilator and confirm no respiratory effort with a PaCO2 rise to at least 60 mmHg (or a 20 mmHg increase from baseline). If the test cannot be completed safely, use an ancillary study such as cerebral angiography, radionuclide perfusion, or EEG.
Trap: performing an apnea test in a patient with a high baseline PaCO2 without requiring the 20 mmHg rise, relying on EEG in a sedated patient, or treating spinal reflexes such as the Lazarus sign as evidence of life.
Rule of thumb: if any confounder cannot be excluded, the diagnosis of brain death cannot be made; there is no partial or probable brain death.