Brain death: Clinical sciences

Brain death is defined as the irreversible loss of all brain functions that results in permanent loss of consciousness, brainstem reflexes, and spontaneous respirations. Important causes of brain death include trauma, stroke, hypoxic-ischemic injury, mass lesions, infections, and toxic or metabolic disorders. As with death by cardiopulmonary criteria, declaring brain death means declaring the death of the patient.

Now, if your patient presents with coma, which could be a sign of brain death, first, perform an ABCDE assessment. You should always consider these patients unstable, so begin acute management immediately! Stabilize the airway, breathing, and circulation. This means that you will need to intubate the patient and place them on mechanical ventilation. Next, obtain IV access, and begin continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry, as well as cardiac telemetry.

Once you stabilize the patient, obtain a focused history and physical examination as well as labs, including a complete metabolic panel, toxicology screen, and alcohol level. Also, don’t forget to order an MRI or CT of the brain.

History will reveal a recent loss of consciousness, often in combination with an event that led to a catastrophic brain injury, such as head trauma and stroke, as well as drowning, choking, or cardiac arrest which can result in hypoxia and anoxia.

Additionally, there might be a recent brain infection or toxin ingestion. Brain death might also occur as a result of renal or hepatic failure, which can lead to severe metabolic derangements and subsequent cerebral edema.

On physical examination, your patient will have an altered mental status, meaning they will be unconscious and unresponsive to visual, auditory, and tactile stimuli. They will not have cerebrally-mediated motor responses, like eye-opening or localizing to painful stimuli, such as nail bed pressure or sternal rub.

Additionally, brainstem reflexes will be absent bilaterally. First, be sure to check for pupillary reflexes. Shine a bright light into each eye and assess for pupillary constriction.

Next, check corneal reflexes. Apply a tactile stimulus, such as a cotton tip, to each cornea and look for eye blinks.

Next up is the oculocephalic reflex. Hold the patient’s eyes open and move the patient’s head quickly from side to side, and up and down. If the eyes stay midline relative to the head position throughout the range of head movement, oculocephalic reflexes are absent.

Next, test the oculovestibular reflexes using the caloric reflex test. Insert cold water into each ear canal and look for any eye movement, including nystagmus. Now, keep in mind that the oculocephalic and oculovestibular reflexes test the same cranial nerves, but the oculovestibular reflex test provides a stronger stimulus. If you can’t assess the oculocephalic reflexes, such as in the case of cervical spine injury, you could still declare brain death if the oculovestibular reflexes are absent bilaterally. However, if you can’t assess the oculovestibular reflexes, for example, if there’s a significant ear trauma, testing the oculocephalic reflexes alone is not sufficient!

Finally, to test the gag and cough reflexes, insert an object such as a cotton tip, tongue blade, or suctioning catheter into the mouth and touch the back wall of the oropharynx. If your patient is intubated, you can also assess the cough reflex using the endotracheal tube suctioning catheter.

Now, here’s a clinical pearl to keep in mind! Even in brain death, spinally-mediated reflexes can be present. Continue with your evaluation. Examples include deep tendon reflexes and the Lazarus sign, which refers to elevation and flexion of the arms that subsequently fall to the chest. Something similar to the position Egyptian mummies have.

Moving on to labs. The complete metabolic panel might be normal, while the toxicology screen should be negative, and the serum alcohol level should be undetectable.

CT scan or MRI of the brain will show cerebral edema, which may have progressed to brain herniation. It might also show diffuse loss of gray-white matter differentiation, intracranial hemorrhage, infarction, or a brain mass.

With these findings, you should suspect brain death, so your next step is to assess other prerequisites for brain death determination. You want to be sure that there are no false declarations, so there is a strict list of criteria that your patient has to meet! First, observe the patient for at least 24 hours to ensure there is no improvement.

Next, assess if any medications were given that could potentially affect consciousness or blunt brainstem reflexes. For example, if the patient previously received barbiturates, make sure that the medication level is not therapeutic or supratherapeutic. If levels are not testable, you should wait at least 5 half-lives of the medication.

Next, there should be no severe metabolic or acid-base derangements. If these are present, correct them if possible. Next, the patient should not be pharmacologically paralyzed.