On the following day, the patient responds only
to noxious stimuli by posturing in extension. The pupils are 4 mm, fixed, and
nonreactive to light. The family asks whether the patient is brain dead. What
is your response? What are the criteria for brain death?
The patient is not brain dead, but if he
survives, the like-lihood of a persistent vegetative state is very high. If the
patient does not have a living will stating his wishes, the discussion with the
family should first provide information regarding the current status and
prognosis in a way that nonmedical people can comprehend. The discussion should
then center on attempting to elicit the wishes of the patient. If no wishes
were clearly stated, the patient’s values should be explored to reach a
decision regarding pursuit or withdrawal of treatment.
The criteria for brain death are the
irreversible absence of brain function, including cortex and brainstem, and the
absence of hypothermia, or toxic, or metabolic disorder. Precise protocols for
determining brain death vary among institutions. If the cause of the coma is
unknown, a period of observation of at least 24 hours without neurologic change
Several criteria have to be met to affirm the
diagnosis of brain death.
of hypothermia (temperature <32°C).
of hypotension (SBP <90 mmHg).
of a significant metabolic disorder (hypo-glycemia, hypo- or hypernatremia,
acidosis or alkalosis, uremia, adrenal insufficiency, hypothyroidism, etc.).
of toxic substances that can cause depressed brain function. Blood and urine
analysis for toxins may be performed.
with absence of purposeful movements. Spontaneous movements of spinal origin
are possible and do not contravene the diagnosis of brain death.
of brainstem function as evidenced by the absence of all of the following:
reflex—no blinking when the corneas are gently touched with a clean sponge.
(gag) reflex and coughing during deep tracheal suctioning.
(doll’s eyes) reflex—no movement of the eyes when the patient’s head is turned
from side to side.
reflex—no movement of the eyes when iced water is injected into each ear.
response to light—dilated pupils if cervical sympathetic pathways are intact.
reflex—assessed by performing an apnea test. To perform this test, the patient
is ventilated with 100% oxygen for 10 minutes (or more if there is underlying
lung disease). The ventilator is then dis-connected and a catheter providing 6
L/min of oxygen is inserted into the endotracheal tube. ABGs are drawn before
initiating the test and 5 and 10 minutes later. The PaCO2 should
reach 60 mmHg or rise by >20 mmHg if the baseline PaCO2 was
>40 mmHg. This appears to be adequate for spontaneous ventilation to resume
if the medullary respiratory centers are func-tional. The test is interrupted
if the patient develops dysrhythmias, or becomes hypotensive, or hypoxemic. An
ABG should be drawn at that time to determine whether the PaCO2 had
increased sufficiently for the test to be conclusive.
· Confirmatory tests, such as a cerebral
angiogram or a radionuclide scan, demonstrating the absence of blood flow to
the brain, are sufficient to affirm brain death. A transcranial Doppler
ultrasound examination showing small systolic peaks with no diastolic flow has
similar value. The absence of signal on both electroencephalogram (EEG) and
brainstem evoked potentials is also sufficient. Some of these tests are
required by policy in some institu-tions; however, brain death can be affirmed
based purely on clinical criteria.
All evidence should be adequately documented in
the chart, and two concurring physicians should confirm the diagnosis of brain
death. The family can then be approached for solid organ and tissue donation.
In children, these criteria are slightly
different in two respects:
interval between the two determinations is mandated in adults, i.e., patients
over 18 years of age. From term to 2 months old the determinations should be
separated by at least 48 hours, between the ages of 2 months and 1 year by 24
hours, and by 12 hours between the ages of 1 and 18 years.
tests are optional beyond the age of 1 year. Two confirmatory tests are needed
between term and 2 months of age, while only one confirmatory test is required
between 2 months and a year.