Brain death: Clinical sciences

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Introduction 0:00–0:34

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.

Unstable Patient 0:34–1:08

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.

Focused H&P 1:08–4:55

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.

Suspect brain death 4:55–6:20

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.
Finally, the body temperature should be at least 36 degrees Celsius, the systolic blood pressure should be 100 millimeters of mercury or greater, and the mean arterial pressure 75 millimeters of mercury or greater.
In other words, be sure to rewarm your patient and raise the blood pressure because hypothermia and hypotension can blunt neurologic function!
If your patient meets these prerequisites, your next step is to evaluate for spontaneous respiratory effort using apnea testing.

Apnea test 6:20–7:23

This test assesses spontaneous breathing in the setting of hypercarbia and acidosis, which would normally trigger the respiratory center in the brainstem and tell the body to breathe.
Before starting the test, make sure your patient is adequately oxygenated to minimize the risk of hypoxia and potential organ injury.
You can check this by obtaining an arterial blood gas. This way, you can be sure that pH values and partial pressures of oxygen and carbon dioxide are within normal limits.
Next, disconnect the ventilator, while still providing oxygenation down the endotracheal tube. During this step, closely look for any signs of breathing.
Keep in mind that you should abort the test if the patient becomes hypoxic or hemodynamically unstable because you will be risking further organ damage if there’s no brain death!
If spontaneous respirations are present, there’s no brain death so abort the apnea test immediately and reconnect the ventilator!

Consider alternative diagnosis 7:23–7:40

In this case, consider alternative diagnoses, such as coma or non-convulsive status epilepticus. However, if there is no evidence of spontaneous respirations, the carbon dioxide will begin to build up in the body, so repeat blood gas and assess for hypercarbia and acidosis.

Brain death 7:40–10:07

Hypercarbia and acidosis are consistent with apnea, meaning the test is positive, so you can declare brain death. Now, here’s a clinical pearl to keep in mind!
There are situations where you cannot complete a clinical brain death evaluation, and must obtain ancillary tests to confirm brain death.
Examples of such situations include facial or ear trauma precluding brainstem reflex testing, the presence of motor movements that are not clearly spinally-mediated, severe metabolic derangements that you can't correct, or intolerance of apnea testing because of hypoxia or hypotension.
In these situations, obtain ancillary testing to assess for the presence of blood flow and perfusion in the brain using 4-vessel catheter angiography, radionuclide perfusion imaging, or transcranial Doppler ultrasonography.
Once you confirm brain death, declare a time of death, inform your patient’s family or power of attorney, and provide counseling and support.
You should notify the appropriate organ donation organization or team. However, you should not be involved in the organ transplant evaluation or decision-making since you have been caring for this patient.
This is considered a conflict of interest for you that can directly benefit another patient. If organ donation is not elected, you should allow loved ones some time with the deceased and later withdraw mechanical and pharmacologic support.
Now, here’s one last clinical pearl to keep in mind! A brain death evaluation in children differs in a few ways from a brain death evaluation in adults.
First, in children younger than two years old, the observation should be at least 48 hours. Next, you should maintain the blood pressure at or above the fifth percentile for age.
In addition to the other brainstem reflexes, in children younger than six months of age, you should also check sucking and rooting reflexes.
Finally, the clinical exam, including the apnea test, must be performed by two different examiners. Alright, as a quick recap… Brain death is defined as the irreversible loss of all brain function due to catastrophic injury, resulting in permanent loss of consciousness, brainstem reflexes, and spontaneous respirations.

Review 10:07–10:45

The clinical exam will demonstrate no response to stimuli, absent brainstem reflexes, and no spontaneous respirations. If you cannot perform a part of the clinical exam, consider ancillary testing.
Once you declare brain death, provide family counseling and support, contact the appropriate organ donation organization, and if organ donation is not elected,