HISTORY

In 1902, Cushing^[3] first reported cessation of cerebral circulation when intracranial pressure exceeded arterial blood pressure in monkeys. He also described the use of artificial ventilation to prolong cardiac function for 23 hours after cessation of spontaneous respiration in a patient with a brain tumor. In 1959, Bertrand and colleagues^[4] reported the maintenance of respiration by mechanical means for 3 days after death of a patient with otitis media who underwent circulatory collapse. Repeated convulsions had preceded a deep coma. Autopsy revealed extensive brain necrosis of the cerebral and cerebellar cortices, basal ganglia, and brainstem nuclei, which was attributed to cessation of cerebral circulation during artificial ventilation. Also in 1959 appeared the first description of cessation of

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These historical reports support the argument that the concept of brain death is independent of and was established before the start of organ transplantation from brain-dead patients. However, there is still

TABLE 79-1 -- Diagnostic criteria for the clinical diagnosis of brain death

A. Prerequisites. Brain death is the absence of clinical brain function when the proximate cause is known and demonstrably irreversible.

1. Clinical or neuroimaging evidence of an acute central nervous system catastrophe that is compatible with the clinical diagnosis of brain death

2. Exclusion of complicating medical conditions that may confound clinical assessment (no severe electrolyte, acid-base, or endocrine disturbance)

3. No drug intoxication or poisoning

4. Core temperature ≥32°C (90°F)

B. The three cardinal findings in brain death are coma or unresponsiveness, absence of brainstem reflexes, and apnea.

1. Coma or unresponsiveness—no cerebral motor response to pain in all extremities (nail-bed pressure and supraorbital pressure)

2. Absence of brainstem reflexes

a. Pupils

i. No response to bright light

ii. Size: midposition (4 mm) to dilated (9 mm)

b. Ocular movement

i. No oculocephalic reflex (testing only when no fracture or instability of the cervical spine is apparent)

ii. No deviation of eyes to irrigation in each ear with 50 mL of cold water (allow 1 minute after injection and at least 5 minutes between testing on each side)

c. Facial sensation and facial motor response

i. No corneal reflex to touch with a throat swab

ii. No jaw reflex

iii. No grimacing to deep pressure on nail bed, supraorbital ridge, or temporomandibular joint

d. Pharyngeal and tracheal reflexes

i. No response after stimulation of the posterior pharynx with tongue blade

ii. No cough response to bronchial suctioning

3. Apnea-testing performed as follows:

a. Prerequisites

i. Core temperature ≥36.5°C or 97°F

ii. Systolic blood pressure ≥90 mm Hg

iii. Euvolemia. Option: positive fluid balance in the previous 6 hours

iv. Normal PaCO2 . Option: arterial PCO2 ≥40mm Hg

v. Normal PaO2 . Option: preoxygenation to obtain arterial PaO2 ≥200 mm Hg

b. Connect a pulse oximeter and disconnect the ventilator.

c. Deliver 100% O2 , 6 L/min, into the trachea. Option: place a cannula at the level of the carina.

d. Look closely for respiratory movements (abdominal or chest excursions that produce adequate tidal volumes)

e. Measure arterial PaO2 , PCO2 , and pH after approximately 8 minutes, and reconnect the ventilator.

f. If respiratory movements are absent and arterial PCO2 is ≥60 mm Hg (option: 20 mm Hg increase in PCO2 over a baseline normal PCO2 ), the apnea test result is positive (i.e., it supports the diagnosis of brain death).

g. If respiratory movements are observed, the apnea test result is negative (i.e., it does not support the clinical diagnosis of brain death), the test should be repeated.

h. Connect the ventilator if, during testing, the systolic blood pressure becomes ≤90 mm Hg or the pulse oximeter indicates significant oxygen desaturation and cardiac arrhythmias are present; immediately draw an arterial blood sample and analyze arterial blood gas. If PCO2 is ≥60 mm Hg or PCO2 increase is ≥20 mm Hg over baseline normal PCO2 , the apnea test result is positive (it supports the clinical diagnosis of brain death); if PCO2 is <60 mm Hg or PCO2 increase is <20 mm Hg over baseline normal PCO2 , the result is indeterminate, and an additional confirmatory test can be considered.

Adapted from Practice Parameters for Determining Brain Death in Adults: Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 45:1012, 1995.

dispute about whether brain death is or is not directly related to organ transplantation. The heated discussion on brain death started after the first heart implantation by Barnard in 1967. One year later, Harvard Medical School published its criteria for brain death,^[6] followed by numerous other publications and criteria^{[7] [8] [9] [10]} ( Table 79-1 ).