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 is necessary.
Several criteria have to be met to affirm the diagnosis of brain death.
· Absence of hypothermia (temperature <32°C).
· Absence of hypotension (SBP <90 mmHg).
· Absence of a significant metabolic disorder (hypo-glycemia, hypo- or hypernatremia, acidosis or alkalosis, uremia, adrenal insufficiency, hypothyroidism, etc.).
· Absence of toxic substances that can cause depressed brain function. Blood and urine analysis for toxins may be performed.
· Coma with absence of purposeful movements. Spontaneous movements of spinal origin are possible and do not contravene the diagnosis of brain death.
· Absence of brainstem function as evidenced by the absence of all of the following:
o Corneal reflex—no blinking when the corneas are gently touched with a clean sponge.
o Oropharyngeal (gag) reflex and coughing during deep tracheal suctioning.
o Oculocephalic (doll’s eyes) reflex—no movement of the eyes when the patient’s head is turned from side to side.
o Oculovestibular reflex—no movement of the eyes when iced water is injected into each ear.
o Pupillary response to light—dilated pupils if cervical sympathetic pathways are intact.
· Respiratory 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:
· No 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.
· Confirmatory 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.
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