Chapter 60 Brain Death
1 What is brain death?
Brain death is a universally accepted medical and legal standard for determining death. A determination of brain death is equivalent to cardiopulmonary death. Brain death is a complete and irreversible loss of brain and brainstem function when other body organ systems may persist. The advent of modern critical care intervention, primarily mechanical ventilation, necessitated a new definition of death because it was now possible to maintain vital functions for extended periods of time. The advent of organ transplantation in the 1950s brought into focus the need for a clear and precise definition of death of the brain in the face of preserved cardiopulmonary function to identify under what circumstances organ removal could occur.
2 When should the diagnosis of brain death be considered?
Active debate continues regarding minimum time of observation before determining brain death. The diagnosis is rarely if ever considered before the first 6 to 24 hours after injury. A variety of toxic and metabolic derangements associated with the onset of critical illness make brain and brainstem function difficult to assess in the hyperacute setting. Patients being considered for brain death uniformly have endotracheal tubes in place and are receiving mechanical ventilation. Sedatives, narcotics, and paralytics used for intubation must be allowed several half-lives of elimination. Pharmacokinetics are often prolonged in patients with multiorgan dysfunction who make up many of these patients.
3 What are the current guidelines for determination of brain death?
Mollaret and Goulon first reported 23 cases of irreversible coma in 1959. This was followed by early standards produced at Harvard Medical School in 1968. The Uniform Determination of Death Act (UDDA) has been adopted as law in most U.S. states. It defines as dead an individual who has sustained either:
Irreversible cessation of circulatory and respiratory functions, or
Irreversible cessation of all functions of the entire brain, including the brainstem. A determination of death must be made with accepted medical standards.
The American Academy of Neurology (AAN) practice parameter for determining brain death in adults set forth “accepted medical standards” left open by the UDDA in 1995. In adults, there are no published reports of recovery of neurologic function after a diagnosis of brain death using the criteria presented in the 1995 AAN practice parameter. Brain death should be a diagnostic entity and never used as a prognostic statement about poor chances of recovery.
4 Who can perform a brain death examination?
In most U.S. states, any physician is allowed to determine brain death. Neurologists, neurosurgeons, and intensive care specialists may have specialized expertise. Brain death statutes vary by states within the United States, and certain hospital guidelines may require examiners to have specific expertise. Given the complexity of the examination, the examiner should have extensive experience with the brain death examination and full understanding of accepted standards.
5 What prerequisites must be met before performing a brain death examination?
These are defined in Box 60-1.
Box 60-1 Prerequisites to be Met Before Performing a Brain Death Examination
Coma, irreversible and cause known. (Glasgow Coma Scale score must be 3)
CNS depressant drug effect absent (if indicated, perform toxicology screen; if barbiturates given, serum level should be <10 mcg/mL)
No evidence of residual paralytics (verify by electrical nerve stimulation if paralytics used)
Absence of severe acid–base, electrolyte, endocrine abnormality
Normothermia or mild hypothermia (core temperature >36° C)
Systolic blood pressure ≥100 mm Hg (pressor agents are okay to use)
6 What findings should be present on brain death examination?
These are defined in Box 60-2.
Box 60-2 Findings that Should be Present on Brain Death Examination
Pupils nonreactive to bright light, corneal reflex absent bilaterally
Oculocephalic reflex absent (test only if C-spine cleared)
Oculovestibular reflex absent (cold-water caloric testing)
No facial movement to noxious stimuli at supraorbital ridge or temporomandibular joints
Cough reflex absent to deep tracheal suctioning
Absence of motor response to noxious stimuli in all four limbs (spinally mediated reflexes are permissible; see question 6)
7 Can a patient make movements and still meet criteria for brain death?
Yes. Spinally mediated reflexes and automatisms can be present in the setting of brain death. These movements are often misinterpreted by laypersons as signs of purposeful brain function. Careful neurologic examination can differentiate between reflexive movements and purposeful motor movements.
8 What are the common spinally generated movements?
These are nonpurposeful movements released by lack of descending inhibition of primitive spinal motor reflex pathways.
Deep-tendon reflexes: For example, Achilles, patellar, and biceps are by definition monosynaptic spinally mediated reflexes and hence often preserved despite brain death.
Abdominal reflexes: Deviation of the umbilicus toward a light stroking of the skin. Often preserved in brain-dead patients, it may be absent in normal or obese patients.
Triple flexion response or limb posturing: Stereotyped, nonpurposeful flexion or extension and internal rotation in response to noxious stimulus. (A movement may be purposeful if the limb reliably moves away from, rather than toward, an applied noxious stimulus.)
Lazarus sign: Considered a variant of opisthotonus. It consists of extensor posturing of the trunk, which may look like chest expansion, simulating a breath. It may be accompanied by raising and crossing of the arms in front of the chest or neck. This sign most often occurs in the setting of apnea testing or disconnection from the ventilator. Hence it may be upsetting for family members or health care providers to witness this reflex.
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