| INTRODUCTION
Brain death is defined as “Irreversible cessation of all functions
of the entire brain including the brain stem”. In adults, the
chief causes of brain death are traumatic brain injury and subarachnoid
haemorrhage.4 The declaration of brain death requires not only a series
of careful neurological tests but also the establishment of the cause
of coma, the ascertainment of irreversibility, the resolution of any
misleading clinical neurological signs, the recognition of confounding
factors, the interpretation of the .ndings on neuroimaging and the performance
of any confi.rmatory laboratory tests that are deemed necessary.
1 Diagnostic criteria for clinical diagnosis of brain death.
2 Prerequisites
1. Absence of clinical brain function when the proximate cause is known
and demonstrably irreversible.
2. Clinical or neuroimaging evidence of an acute CNS catastrophe that
is compatible with the clinical diagnosis of brain death.
3. Exclusion of complicating medical conditions that may confound clinical
assessment [i.e. no severe electrolyte, acid base or endocrine disturbance.]
4. No drug intoxication or poisoning.
5. Core temperature greater or equal to 32 degrees Celsius
The central considerations in the diagnosis of brain death are
1. Absence of cerebral functions.
2. Absence of brain stem functions including spontaneous respiration.
3. Irreversibility of the state.
Absence of cerebral function is judged by presence of unconsciousness
and total lack of spontaneous unconscianess movements and of motor and
vocal responses to all visual, auditory and cutaneous stimulation. Absence
of brain stem
function is judged by absence of pupillary responses to light and pupils
at mid position with respect to dilatation
(4-6 mm), absence of spontaneous eye movements, absence of corneal re.exes,
absence of caloric responses, absence of gag reflex and coughing in
response to tracheal suctioning, sucking and rooting re.exes, decerebrate
responses to noxious stimuli and absence of respiratory movements. Lack
of respiratory drive at a PaC02 that is 60 mm Hg or 20 mm Hg above normal
baseline values is also necessary.
Conditions interfering with the clinical diagnosis of brain death.
1. Facial trauma
2. Toxic levels of any sedative drugs, aminoglycosides, tricyclic antidepressants,
anticholinergics, antiepileptics,
chemotherapeutic agents or neuromuscular blocking agents.When these
factors are operating, some con.rmatory tests are recommended.
3. Clinical reflexes that can be seen in a case with brain death.2 a.
Babinski re.ex b. Deep tendon re.exes, super.cial abdominal reflexes,
triple .exion response. c. Spontaneous movements of limbs other than
pathologic .exion or extension response. d. Respiratory like movements
(shoulder elevation and adduction, back arching and intercostal expansion
without signi.cant tidal volumes). e. Sweating, blushing, tachycardia
f. Normal blood pressure without pharmacologic
support or sudden increases in blood pressure. |
| Confirmatory
Laboratory Tests
Brain death is a clinical diagnosis. A repeat clinical evaluation
at another time, usually six hours later is recommended, but this interval
is arbitrary. A confirmatory test is not mandatory but is desirable
in patients in whom specific components of clinical testing cannot be
reliably performed for one reason or the other.
1. Conventional cerebral Angiography.
2. Technetium-99m hexamethylpropyleneamineoxime brain scan.
3. Electroencephalography
4. Transcranial Doppler Ultrasonography.
5. Somatosensory evoke potentials.
After the clinical criteria of brain death have been met, the physician
should inform the next of kin who can be approached about organ donation.
The family should be told in unequivocal terms that the patient is dead.
Mechanical ventilation, fluids and blood pressure medication are administered.
only to procure organs in the event that permission for donation is
given. Management of a brain dead patient in preparation for donation
is complicated and advice from a neurologist specialized in neurological
critical care or from an anaesthesiologist should be strongly considered.
Major immediate threats to organs are
1. Pulmonary oedema, requiring pulmonary artery catheter placement and
treatment with positive end-expiratory pressure ventilation.
2. Hypotension, requiring adequate fluid resuscitation and vasopressors
3. Polyuria from diabetes insipidus, requiring desmopressin.
When mechanical ventilation and supports are continued because of ethical
or legal objections to their discontinuation, what usually follows is
an invariant heart rate from a differentiated sinoatrial node, structural
myocardial lesions leading to a marked reduction in the ejection fraction,
decreased coronary perfusion the need for increasing use of inotropic
drugs to maintain blood pressure and a fragile state that leads to cardiac
arrest within days or weeks.
REFERENCES
1. Eelco FM Wijdicks. The diagnosis of Brain Death. The New Engl J Med
2001; 344 : 1215-21.
2. The quality standards sub-committee of the American Academy of Neurology.
Practice parameters for determining
brain death in adults. Neurology 1995; 45 : 1012-14.
3. Uniform Determnation of Death, uniform laws Annotated (ULA) 589 West
1993 and West supp 1997.
4. WIjdicks EFM Determing brain death in adults. Neurology
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