THE HONG KONG SOCIETY OF CRITICAL CARE MEDICINE POSITION STATEMENT
Dr Tom BUCKLEY, Dr SO Hing Yu, Dr WONG Kwan Keung, Dr YAN Wing Wa, on behalf of the Hong Kong Society of Critical Care Medicine
Brain death is established by the documentation of irreversible coma and irreversible loss of brain stem reflex responses and respiratory center function or by the demonstration of the cessation of intracranial blood flow. Despite philosophical arguments, the concept that brain death is equivalent to death is accepted legally and within the medical community in Hong Kong. Once brain death has occurred, artificial life support is inappropriate and should be withdrawn. It is good medical practice to recognize when brain death has occurred and to act accordingly, sparing relatives from further emotional trauma of futility.
The purposes of this document are:
1. To provide recommendations for qualified medical practitioners (vide infra) in relation to certification of brain death for patients who are 1 year of age or older; and
2. To provide a reference for the Hong Kong community to reassure them that certification of brain death is performed with diligence and in accordance with prevailing medical evidence and opinion.
The diagnostic criteria presented for brain death certification are based on the following documents:
The Statement issued by the Honorary Secretary of the Conference of Medical Royal Colleges and their Faculties in the United Kingdom on 11 October 1976
British Medical Journal 1976; ii:1187-1188.
Criteria for the diagnosis of brain stem death. Review by a working group convened by the Royal College of Physicians and endorsed by the Conference of Medical Royal Colleges and their Faculties in the United Kingdom.
Journal of the Royal College of Physicians of London 1995; 29:381-2
Recommendations concerning Brain Death and Organ Donation, 2nd Edition. ANZICS Working Party on Brain Death and Organ Donation Report,
Australian and New Zealand Intensive Care Society, March, 1998.
They are accepted as being sufficient to distinguish between those patients who retain the functional capacity to have a chance of even partial recovery from those in whom no such possibility exists.
Preconditions and exclusions prior to considering diagnosis of brain death
1. Diagnosis of severe brain injury which is consistent with progression to brain death (the clinical diagnosis is usually confirmed by neuro-imaging)
There should be no doubt that the patient’s condition is due to irremediable structural brain damage. The diagnosis of a disorder which can lead to brain death should have been fully established.
1.1 It may be obvious within hours of a primary intracranial event such as severe head injury, spontaneous intracranial haemorrhage, or after neurosurgery that the condition is irremediable.
1.2 But when a patient has suffered primarily from cardiac arrest, hypoxia, or severe circulatory insufficiency with an indefinite period of cerebral anoxia or is suspected of having cerebral air or fat embolism then it may take longer to establish the diagnosis.
2. Apnoeic patient on a ventilator
The patient is unresponsive and not breathing spontaneously. Muscle relaxants (neuromuscular blocking agents) and other drugs should have been excluded as a cause of such findings (vide infra).
3. Exclusion of potentially reversible causes of coma
3.1 Depressant drugs or poisons
Clinical effects of sedative drugs and/or muscle relaxants must be excluded before confirmation of brain death.
3.1.1 It is recommended that the drug history should be carefully reviewed and adequate intervals allowed for the persistence of drug effects to be excluded. This is of particular importance in patients whose primary cause of coma lies in the toxic effects of drugs followed by anoxic cerebral damage. The period of observation depends on the pharmacokinetics of the sedative drugs used, the doses used, and the liver and renal function of the patient.
3.1.2 Blood and urine screening tests and measurement of serum levels should be used when necessary.
3.1.3 If there is any doubt about the persisting effects of opioid or benzodiazepines, an appropriate drug antagonist should be given.
3.1.4 A peripheral nerve stimulator should always be used to confirm intact neuromuscular conduction if muscle relaxants have been used.
3.2 Primary hypothermia
The body temperature in these patients may be low because of depression of central temperature regulation by drugs or by brain stem damage and it is recommended that it should be greater than 35oC before diagnostic tests are carried out. A low-reading thermometer should be used.
3.3 Metabolic and endocrine disturbances (e.g. severe electrolyte or endocrine disturbances)
Metabolic and endocrine factors contributing to the persistence of coma must be carefully assessed. There should be no profound abnormality of the serum electrolytes, acid base balance, or blood glucose concentrations.
3.4 Arterial hypotension
Clinical tests of brain stem function
All brain stem reflexes must be absent.
The testing of all the following is considered sufficient
1. Both pupils are fixed in diameter and do not respond to changes in the intensity of light.
2. Corneal reflex is absent in both eyes.
3. The vestibulo-ocular reflex is absent.
3.1 This is absent when no eye movement occurs in both eyes during or after the slow injection of at least 20ml of ice-cold water into at least one external auditory meatus, or preferably into each external auditory meatus in turn.
3.2 Clear access to the tympanic membrane should be established by direct inspection. This test may be contraindicated on one or other side by local trauma.
4. No motor responses within the cranial nerve distribution can be elicited by adequate painful stimulation of any somatic area.
5. There is no gag reflex.
6. There is no cough reflex.
7. Apnoea test should be done last. No respiratory movements occur when the patient is disconnected from the mechanical ventilator for long enough to ensure that the arterial carbon dioxide tension rises above the threshold for stimulating respiration.
7.1 The PaCO2 must be greater than 8.0kPa and arterial pH less than 7.30. Blood-gas analysis must be available for this test to be performed. If the test is not available the patient must be moved to a facility where this test is routinely available.
7.2 These patients may be moderately hypothermic (35oC-37oC), flaccid, and with a depressed metabolic rate, so that PaCO2 rises only slowly in apnoea (about 0.27kPa/min). They should be disconnected from the mechanical ventilator when their PaCO2 is close to normal.
7.3 Hypoxaemia during disconnection should be prevented by preoxygenation and administration of oxygen during the test, e.g. by delivering oxygen through a catheter into the trachea.
Other important considerations
1. Period of observation and repetition of tests
Clinical confirmation of the diagnosis of brain death requires that irreversibility of cessation of brain function is established after a period of observation. Two separate examinations should be performed during the observation period by two medical practitioners.
1.1 The first formal examination should only be performed after
1.1.1 All preconditions have been met
1.1.2 A minimum of four hours observation during which the patient has been comatose (Glasgow Coma Score 3), had non-reacting pupils, absent cough and gag reflexes, and no spontaneous breathing efforts.
1.2 The second examination should not be performed until at least two hours after the first examination, so that the total period of observation is a minimum of six hours. The minimum period of observation need to be extended to a total of twelve hours after primary hypoxic brain damage or other non-traumatic brain conditions. (See item 1.2 in the section on Preconditions and exclusions prior to considering diagnosis of brain death.)
2. The following observations are compatible with the diagnosis of brain death
2.1 Movements of limbs in response to a stimulus outside the distribution of cranial nerves.
2.2 Sweating, blushing, tachycardia.
2.3 Normal blood pressure without pharmacological support.
2.4 Absence of diabetes insipidus (normal osmolar control mechanism)
2.5 Deep tendon reflexes.
2.6 Extensor planter reflex.
3. Neither medical practitioner certifying brain death should be the designated officer authorizing removal of tissue, proposing to remove the tissue, or attending a recipient of tissue to be removed.
4. Confirmatory investigations
If the preconditions for clinical diagnosis and confirmation of brain death cannot be satisfied, objective demonstration of absence of intracranial blood flow is required.
4.1 Such situations will include:
4.1.1 No clear cause of coma
4.1.2 Possible metabolic or drug effect
4.1.3 Cranial nerves cannot be adequately tested
4.1.4 Cervical vertebral or cord injury
4.1.5 Cardiovascular instability precluding apnoea test
4.1.6 Severe hypoxaemic respiratory failure precluding apnoea test
4.2 Confirmatory investigations which may be used include:
4.2.1 Three or four vessel radio-contrast angiography, by direct injection or digital subtraction, may be used to demonstrate absent intracranial blood flow
4.2.2 Radionuclide examination which reliably demonstrates absent brain stem and cerebral blood flow can also be used for this purpose.
Blood flow should be absent from both vertebro-basilar and supratentorial circulation.
4.3 The six hour period of observation of coma and of absent brain stem responses, where these can be tested, should also apply and should precede the investigation.
4.4 Written certification of brain death should be made by the two medical practitioners (not including the medical practitioner who performed the investigation) who, having examined the patient and with the knowledge of the circumstances of the aetiology of the coma, are further assisted in making the diagnosis of brain death by evidence of absent intracranial blood flow.
5. Time of death
5.1 The time of death should be recorded as the time when certification of brain death has been completed, that is, following the second clinical examination of brain stem function.
5.2 If a confirmatory investigation is used, then the time of death should be after the confirmatory investigation of absent intracranial blood flow as well as the two sets of clinical examinations of brain stem function (if the tests can be done) have all been completed.
It is recommended that hospitals establish a policy and set of procedures incorporating these guidelines that will govern the confirmation of brain death. These would include:
1. A description of the brain death certification procedure within the hospital including:
1.1 Certification of brain death based upon this document;
1.2 The duties and responsibilities of designated officers;
1.3 The location of all necessary documents;
1.4 The location of contact numbers for police, forensic pathologists and coroner;
1.5 Details of support services available to staff and families.
2. Recommendations for the status of the two medical practitioners certifying brain death and a registry of suitably qualified practitioners accredited to perform brain death certification in the hospital.
2.1 One of the medical practitioners must be a specialist recognized and designated by the appropriate College as having demonstrated skill and knowledge in the performance of brain death certification. This should usually be an intensivist, critical care physician, neurologist or neurosurgeon.
2.2 The other medical practitioner should preferably be of the same qualification as described in 2.1 but should be at least 6 years after registration and possess the skill and knowledge in the performance of brain death certification.
3. A registry of suitably qualified practitioners accredited to perform confirmatory investigations in the hospital. Recommendations of the appropriate College should be followed where applicable.
4. Suitable forms to document brain death.
5. Access to information about brain death and organ donation.
This information should be suitable for doctors, nurses and allied health practitioners as well as lay people and should be available for the relatives of patients who are confirmed brain dead.