11/14/24, 10\:52 AM Organ Donation and Brainstem Death Testing

Organ Donation and Brainstem Death Testing

Table of contents
Key points ⚡
Succinct notes to superpower your revision
Organ donation\: signi
UK law\: operates on an opt-out system; all adults are considered donors by default after death unless excluded (e.g. under
18, lack capacity) or they object.
Types of donors\: includes l i v i n g (related, unrelated, altruistic) and d e c e a s e d donors (after circulatory death or brainstem
death).
Diagnosing death\: two criteria—cardiorespiratory (irreversible cessation of function) and neurological (brainstem death).
Brainstem testing\: requires two experienced doctors, involving absent central motor response, re
oculovestibular, pharyngeal, cough), and apnoea test.
Preconditions for brainstem death\: exclude reversible coma causes (e.g. hypothermia, overdose), normotension,
normothermia, and no electrolyte imbalance.
Ancillary tests\: used if primary testing is unclear, e.g. CT angiography for absent cerebral blood
Family support\: specialist nurse for organ donation (SNOD) assists families, provides information, and ensures respectful
discussions about donation.
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A comprehensive topic overview

Introduction

Organ donation is a large and sensitive topic within medicine, particularly intensive care. The laws and guidance are
continuously changing, so it is important to understand how a suitable donor is selected.
Organ donation represents a fundamental activity in intensive care, and when a potential candidate is identi
should be considered. It is also possible to become a living donor for those who satisfy speci
Organ donation is an entirely separate domain from organ transplantation. Our renal transplantation article discusses the
intricacies of organ transplantation.

Legal framework

Many countries have transitioned from an organ donor opt-in system to an opt-out system. The legislation in the United
Kingdom re
consent.
1
Under this system, you are considered an organ donor when you die unless you are in an excluded group (i.e. under 18
years old or those who lack capacity) or request otherwise. You still have a choice and can register an objection to
donation.
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Types of donor

Living donor

Living donors are individuals who elect to donate while alive and play a key role in organ donation to reduce national
transplantation lists, particularly for renal transplantation.
Donations from living donors can be classi
Related donation to a blood relative (e.g. sibling/parent)
Unrelated donation to somebody who the recipient has a relationship with (e.g. spouse)
Altruistic donation to somebody who the donor does not know (e.g. unknown person on an organ transplant list)

Deceased donor

death is diagnosed\:
Deceased donors are those who donate after their death and can become donors via two pathways, depending on how
Donation after circulatory death (DCD)
2
Donation after brainstem death (DBD)
3
Identifying potential donors
A fundamental aspect of organ donation is the identi
that the primary reason for non-referral is the lack of identi
4
Identifying potential donors at the earliest opportunity facilitates discussion with families, optimises organ function,
and improves the e
eligibility.

Diagnosing death

There are two primary methods to diagnose death\:
1. Cardiorespiratory (pulselessness and apnoea)
2. Neurological (brainstem death)
The majority of organ donors are DBD donors. This is the most controlled manner of donation, facilitating organ retrieval
while maintaining organ perfusion.

Cardiorespiratory death

De
and the heart permanently stops beating; since the heart is no longer beating, blood
5
This refers to the standard condeath con.

Neurological death

De
cranial nerve activity and the capacity for consciousness.
6
Mechanical ventilation maintains oxygenation and cardiac function continues with the support of vasopressors and other
medications. This facilitates the optimisation of organ function and the potential donor organ(s).

Brainstem testing

Formal brainstem testing must be conducted by two doctors. One must be consultant level, and the other must be more
than
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Fundamentally, this means that two doctors perform brainstem testing together on two separate occasions, in order to
come to an agreed conclusion.

Preconditions

To diagnose death using neurological criteria, reversible causes of coma must be excluded. 7
Mean arterial pressure,
partial pressures of CO 2 2
and O , glucose and serum electrolytes must be measured to aid the exclusion of underlying
cardiorespiratory and endocrine causes.
Reversible causes of coma
Examples of reversible causes of coma include\:
Hypothermia
Overdose of certain illicit drugs and medications (e.g. opioids and benzodiazepines)
Severe hypothyroidism
Electrolyte disturbance (e.g. hypo/hypernatraemia)
Hypoglycaemia
Hypercarbia or hypoxia
Sedation (e.g. propofol, alfentanil)
If any reversible cause of coma is identi
To proceed with brainstem testing, there must be evidence of irreversible brain damage of known aetiology, at least 4
hours of observation with Glasgow Coma Scale (GCS) 3, non-reactive pupils, absence of cough and absence of respiratory
8
e
Adequate time since cessation of sedatives and neuromuscular blockades (consider drug levels and peripheral nerve
stimulation)
Normotension (mean arterial pressure > 60 mmHg)
Normothermia (> 34°C)
Normocarbia (PaCO \< 6.0 kPa i f p o s s i b l e )
2
Absence of hypoxia (PaO > 10 kPa i f p o s s i b l e )
2
Absence of acidaemia/alkalaemia (pH between 7.35-7.45 or [H+] between 45-35 nmol/L)
Absence of electrolyte disturbances
Appropriate ability to assess re

Components of testing

Central motor response
A painful stimulus is applied to the supra-orbital notch or temporomandibular junction. This tests cranial nerves V and VII,
and reassess the GCS.
The absence of a central motor response is consistent with a diagnosis of brainstem death.
Pupillary re
A light source is shone into each eye consecutively, and direct and consensual recranial
nerves II and III.
CN III palsy
In the case of a pre-existing CN III palsy, there would be an absence of direct pupillary constriction in the a
but preserved consensual constriction in the una
pupillary re
death is possible.
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If other re
to con
The absence of pupillary constriction in response to light is consistent with a diagnosis of brainstem death.
Corneal re
The cornea is touched with a piece of sterile gauze to observe for eyelid movement. This tests cranial nerves V and VII.
The absence of eyelid movement is consistent with a diagnosis of brainstem death.
Oculovestibular re
The tympanic membrane is visualised bilaterally with an otoscope to exclude obstruction of the auditory canal. The
patient is placed 30° head up with the head in the midline and the eyelids held open. The tympanum is irrigated with ice-
cold water, and the eyes are observed for nystagmus.
The cold water on the semicircular canal in the inner ear creates a vestibular input asymmetry. This disturbs balance by
simulating a movement that is not occurring, resulting in compensatory eye movements. This tests cranial nerves III, VI, and
VIII.
Absence of nystagmus is consistent with a diagnosis of brainstem death.
Pharyngeal re
The oropharynx is stimulated with a tongue depressor and the patient is observed for the gag re
for elevation as the brainstem controls this key re
independent airway protection. This tests cranial nerves IX and X.
Absence of gag or palatal movement is consistent with a diagnosis of brainstem death.
Cough re
A suction catheter is introduced via the endotracheal/tracheostomy tube into the carina. Any cough re
this stimulation is observed. This tests cranial nerves IX and X.
Absence of a cough re
Apnoea test
This test forms a key part of diagnosing death using neurological criteria. It forms the
lead to haemodynamic instability and hypoxaemia.
A baseline arterial blood gas (ABG) is taken. Before conducting the apnoea test, speci
8-9
Normotension
Normothermia
Euvolaemia
Absence of hypoxia
PaCO 2
> 6 kPa, but not substantially greater
pH \< 7.4
Testing involves disconnection of mechanical ventilation and maintenance of oxygenation via a C-circuit with FiO 1.0.
2
The patient is observed for respiratory e2
stimulates breathing. ABG
measurements are required to ensure a > 0.5 kPa rise in PaCO 2
over at least 5 minutes.
8
Absence of respiratory e
Conclusion
In the United Kingdom, if both sets of tests conducted by the two physicians are consistent with the diagnosis of death
using neurological criteria, then the time of death is recorded as the time of completion of the
As the examinations are independent, they can be sequential, and there is no requirement or need to wait a speci
amount of time between them.

Ancillary tests

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If certain aspects are ambiguous or cannot be completed, ancillary tests can be used as an adjunct to the core testing but
not as a replacement. Ancillary tests are not required to diagnose death using neurological criteria, but they assist in
certain cases (e.g. extensive facial injury).
Examples of ancillary tests include\:
Radiological evidence of absence of cerebral blood
Evidence of absence of bioelectrical activity (e.g. EEG, evoked potentials)

Family discussion

The diagnosis of death using neurological criteria can be extremely di
important to navigate this discussion in an informed manner and to establish the patient's wishes regarding organ
donation. These wishes may not align with the family’s, so this conversation should be respectful, using appropriate
vocabulary.
Specialist nurse for organ donation
A specialist nurse for organ donation (SNOD) is highly trained in the organ donation process. They are involved in
coordinating the surgical transplant team, and they liaise with multiple other teams. They are also pro
communication and working with families regarding organ donation and end-of-life conversations. This includes
conversations regarding the logistics of organ donation and providing speci
involvement of the SNOD aims to provide support throughout the process for the family

References

1. NHS Blood and Transplant. O r g a n d o n a t i o n l a w s . Available from\: [LINK].
2. NHS Blood and Transplant. D o n a t i o n a f t e r c i r c u l a t o r y d e a t h . 2023. Available from\: [LINK].
3. NHS Blood and Transplant. D o n a t i o n a f t e r b r a i n s t e m d e a t h . 2023. Available from\: [LINK].
4. NHS Blood and Transplant. Annual Report on the Potential Donor Audit. 2019. Available from\: [LINK].
5. Manara AR, Murphy PG, O’Callaghan G. D o n a t i o n a f t e r c i r c u l a t o r y d e a t h . British Journal of Anaesthesia. 2012. Available from\:
[LINK].
6. Academy of Medical Royal Colleges. A C o d e o f P r a c t i c e f o r t h e D i a g n o s i s a n d C o n
[LINK].
7. Edlow JA, Rabinstein A, Traub SJ, et al. D i a g n o s i s o f r e v e r s i b l e c a u s e s o f c o m a . The Lancet. 2014. Available from\: [LINK].
8. The Faculty of Intensive Care Medicine. D i a g n o s i n g D e a t h u s i n g N e u r o l o g i c C r i t e r i a . Available from\: [LINK].
9. Greer DM, Kirschen MP, Lewis A, Gronseth GS, Rae-Grant A, Ashwal S, et al. P a e d i a t r i c a n d A d u l t B r a i n D e a t h / D e a t h b y
N e u r o l o g i c C r i t e r i a C o n s e n s u s G u i d e l i n e . Neurology. 2023. Available from\: [LINK].

Reviewer

Dr Lauren O’Callaghan
Cardiac Anaesthesiology Fellow

Related notes

Anaesthetic Emergencies
Complications of Anaesthesia
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Regional Anaesthesia

Test yourself

Contents

Introduction
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