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Introduction

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The concept that death can be diagnosed by neurologic as well as cardiac criteria has been codified by law in the United States in the Uniform Declaration of Death Act. Neurologic “brain” death is particularly relevant to intensive care unit (ICU) care, where cardiac and ventilatory function can be maintained in the absence of brain function. Brain death is the primary requirement for organ donation, although heart-beating and non–heart-beating donors contribute to the donor organ pool. In adults, the primary causes of brain death are traumatic brain injury and subarachnoid hemorrhage, whereas pediatric donors are typically abuse victims. Brain death was first defined in 1968 by an ad hoc committee at the Harvard Medical School based on clinical criteria, and has subsequently undergone redefinition by a variety of national and international bodies. While the specifics vary, the requirements have in common the requirements that the patient be in an irreversible coma, in which the cause is known, the clinical examination is consistent with brain stem death, confounding factors have been ruled out, and confirmatory tests are consistent with the foregoing.

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Definitions and Terms

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  • ▪  Coma: A state of unconsciousness from which the patient cannot be aroused even with stimulation such as pressure on the supraorbital nerve, temporomandibular angle of the mandible, sternum, or nailbed.
  • ▪  Irreversible coma: Coma wherein reversible causes such as acid-base, electrolyte, endocrine disturbances, hypothermia (core temperature < 32°C), drug intoxication, hypotension, poisoning, and pharmacological neuromuscular blockade have been ruled out as potential causes or contributors.
  • ▪  Cause: Etiology of the coma.
  • ▪  Brain stem examination: A series of tests in which the function and reflexes of the mesencephalon, pons, and medulla oblongata are tested.
  • ▪  Confirmatory tests: Radiologic and laboratory tests used to confirm brain death, including cerebral angiography, electroencephalography, transcranial Doppler ultrasonography, cerebral scintigraphy, as well as serum drug levels.

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Techniques

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  • ▪  Clinical tests
    • —Absence of motor responses to painful stimuli.
    • —Absence of light reflex on pupillary examination (no pupillary constriction to bright light) and pupils fixed in midposition or dilated 4 to 9 mm in diameter (Figure 14-1).
    • —Absence of doll’s eyes, that is, no compensatory eye movement in response to rapid rotation of the head to either side.
    • —Absence of oculovestibular response on cold-caloric examination, wherein the tympanum is irrigated with ice water after the head has been tilted to 30 (to make the auditory canal vertical so that it will fill with cold water)—no eye deviation toward cold stimulus (Figure 14-2).
    • —Absence of corneal reflex, that is, no blinking (Figure 14-3) when the cornea is touched (with a cotton swab or pledget).
    • —Absence of gag reflex (Figure 14-4).
    • —Absence of cough on suctioning or movement of the endotracheal tube.
    • —Apnea test: Absence of spontaneous respiratory effort in response to a Paco2 that is 60 mm Hg or 20 mm Hg greater than patient’s normal baseline value.
    • —The test is typically performed after disconnection from the mechanical ventilator to avoid factitious breath sensing ...

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