13. Brainstem Death and Organ Donation Flashcards
What is it
Brainstem death (BSD) refers to the irreversible absence of normal brainstem functioning.
In the UK, BSD equates
to human death and this is based on the
concept that without brainstem function,
higher cerebral activity and
conscious perception is deemed impossible.
What are the diagnostic criteria for brainstem death testing?
Before a patient can be certified as BSD,
certain preconditions must be met:
1
> The patient must be in an apnoeic coma
and ventilator dependent.
2
> Irreversible brain damage of known cause must be established.
3
> Reversible causes of reduced consciousness
must be identified and corrected
(e.g. hypoxia, hypercapnia, hypothermia, hypotension,
acid–base abnormalities, metabolic disturbances (e.g. hyponatraemia), endocrine disease (e.g. hypothyroidism), drugs (e.g. sedative agents and
muscle relaxants)).
Only once these preconditions have been met and at least 6 hours have
elapsed since the onset of coma can formal BSD testing begin.
Who can perform BSD testing?
The test requires two doctors who
have been fully registered with the GMC
for at least 5 years,
one of whom should be a consultant.
Neither should be a member of the organ retrieval team.
Each doctor should perform one set of tests,
watched by the other.
The two sets of tests can be done one after the
other and although many choose to wait a few hours in between sets, this is not a legal necessity.
Death is legally declared after the completion of the first set of tests.
Which tests are performed?
Several cranial nerves (CN) pathways integrating within the brainstem are
tested in order to establish loss of brainstem reflexes to the following:
> Pupillary light reflex:
• Pupils must be fixed, dilated
and unresponsive to light.
• Afferent pathway via optic nerve
(CN II) and efferent pathway via
parasympathetic fibres carried
in the oculomotor nerve (CN III).
> Corneal reflex:
• No reaction.
• Afferent pathway via ophthalmic
branch of trigeminal nerve (CN V) and
efferent pathway via facial nerve (CN VII).
> Painful stimulus to the face
(e.g. supra-orbital pressure):
- No response should be elicited.
* Afferent pathway via trigeminal (CN V) and efferent pathway via facial nerve (CN VII).
> Vestibulo-ocular reflex (caloric test):
• 30 mL very cold saline is injected
rapidly into each external auditory
meatus in an attempt to induce nystagmus.
If the reflex pathway is
intact, the eyes move towards
the ipsilateral ear.
In the event of BSD there are no eye movements.
NB: Examine the auditory canal before
performing this test to ensure
it is not blocked with wax.
• Afferent pathway is via vestibulocochlear nerve
(CN VIII) and efferent pathway is via CN III and abducens nerve (CN VI).
> Gag reflex:
• No gag or cough should be elicited
on stimulation of the posterior
pharyngeal wall.
• Tests glossopharyngeal (CN IX)
and vagus nerve (CN X).
> Apnoea test:
Ventilate the patient with 100% O2 for 10 min,
to ensure normocapnia, then disconnect them from the ventilator.
Insufflate O2, using a tracheal catheter
placed down the endotracheal tube,
to keep oxygen saturations ≥90%.
Watch for respiratory effort during this period.
Allow the PaCO2 to increase to 6.65 kPa before terminating the test. CO2 rises at approximately 0.5 kPa per minute during apnoea; levels should be
confirmed with a blood gas.
How will you manage the patient following brainstem testing?
If the patient is not brainstem dead,
medical care should continue as before.
If the patient is brainstem dead, either:
> Preparations should be made to
withdraw life support or
> If the patient is being considered
for organ donation, the transplant team
will co-ordinate ongoing care
until organ harvesting can take place.
At all stages, it is vital that the family be kept informed of events and supported through them.
Organ donation
What are the different types of
organ donation?
Organ donation
There are two categories of organ donation:
1 Donation after brainstem death (DBD)
2 Donation after cardiac death (DCD)
Can you describe the principles
of each process?
While there are obvious differences in these two processes, they do have common themes:
> The patient must be treated in their best interests at all times. Best interests does not just refer to medical best interests but includes all other emotional and welfare issues. The fact that the patient may be a potential organ donor must not colour decisions about their ongoing medical care.
> Check to see if the patient was on the organ donor register, as this will help inform discussions with the family.
> When considering a patient as a potential organ donor, the family must be consulted early and treated with respect and consideration throughout the
process. If they agree to organ donation, they have the right to change their minds at any stage. It is probably best that the opening discussions are lead by the transplant coordinators as they are skilled at navigating
the issues in this potentially delicate subject area.
> There is no upper or lower age limit for the donor.
> There are few absolute contraindications to donation, these are:
• Active invasive cancer within 3 years (excluding non-melanoma skin
cancer and brain tumours)
• Haematological malignancy
• Untreated systemic infection
• Variant Creutzfeldt–Jakob disease
• HIV disease (though not necessarily infection).
Donation after brainstem death (DBD)
Once BSD has been confirmed and consent given by the family, the ongoing care of the decreased donor turns to focus on optimising the condition of the
organs while awaiting their retrieval.
Organ damage follows BSD as part of an organic pathophysiological process.
Rising intracranial pressure renders the brainstem ischaemic and causes bradycardia and hypertension.
As the brainstem infarcts, there is an unregulated surge in autonomic activity and massive catecholamine release,
the so-called ‘sympathetic storm’.
The hypothalamic–pituitary axis (HA) also fails leading to a decline in hormone levels. These events result in:
> Diabetes insipidus
> Disseminated intravascular coagulation
> Cardiac ischaemia and arrhythmias
> Pulmonary oedema
> Metabolic acidosis
> Hypothermia
Immunological effects are also seen and the immunogenicity of the solid organs increases once BSD occurs in processes that are poorly understood.
To preserve the organs in good condition, it is important to maintain optimal:
> Organ perfusion
Ventilation
Hormone replacement with vasopressin, T3, steroids and insulin
Normal electrolyte status
DBD organ retrieval always seems to take place in the early hours of the morning when everything else on the CEPOD list is finished. There is variation in the approach taken by anaesthetists in these cases.
Some give no anaesthetic at all to the donor while others will ventilate with a volatile.
The rationale of the latter group is to depress any spinal reflexes that may occur during surgery, and not as a result of concerns about awareness in the donor.
These cases can often feel a little unnerving on the first couple of occasions, but the organ retrieval team will usually guide the anaesthetist as
to what they need.
Donation after cardiac death
The need for transplantable organs greatly outstrips the supply, and so we have begun to look beyond those who have suffered BSDs.
This has lead to the advent of donation after cardiac death, sometimes referred to as nonheart-
beating organ donation.
DCD should be considered in all patients where it is decided that further treatment is futile and it is in their best interests to withdraw life-sustaining therapy. By the nature of the process, most of these patients will be on the ICU, but this need not always be the case. The decisions around withdrawal
of therapy must be totally separate from any consideration of the patient as
an organ donor in the minds of the medical team.
Once life-sustaining therapy has been withdrawn, the donor’s organs are subject to ‘warm ischaemia’. Warm ischaemia begins when the systolic BP drops below 50 and oxygen saturations fall below 70% and ends when
the retrieval team begins to cool the organs that have been removed. This begins the period of ‘cold ischaemia’, which aims to extend the time of organ
preservation.
It is vital that the warm ischaemic time is minimal; a liver must not have a warm ischaemic time of longer than 30 minutes, while the kidneys are more
robust and can tolerate 2 hours.
In this way, it is possible that a patient may
die ‘too slowly’ following withdrawal of treatment for their organs to be viable for donation.
The organ retrieval team should be gathered and a theatre ready before treatment is withdrawn. The withdrawal process should be managed
exactly as normal and no changes should be made because the patient is a potential donor.
Death is confirmed by a member of the organ retrieval
team when there has been 5 minutes of cardiorespiratory arrest.
This must be demonstrated on the ECG or arterial line trace: a finger on the pulse is not sufficient. Surgery does not start until 10 minutes after death to ensure a
safety margin.
Ten minutes has been chosen because there is no evidence that return of spontaneous circulation has ever happened in any patient who has been in asystole for more than 7 minutes, even with resuscitation
attempts. During this time, the family can be with the patient if they wish.
The family should be counselled before about the possibility that if the warm ischaemic time is prolonged, organ retrieval may not be possible; however,
tissue and corneas may still be taken.
