Brainstem Death

Brainstem death is a clinical syndrome characterised by the absence of reflexes mediated through the brainstem in a deeply comatose, ventilator-dependent patient. The brainstem connects the spinal cord to the mid-brain, cerebellum, and cerebral hemispheres. This condition carries a grave prognosis; cessation of heartbeat often occurs within days, although intensive support can prolong survival for weeks.

In the UK, brainstem death can be certified as death based on criteria established in "A Code of Practice for the Diagnosis and Confirmation of Death" by the Academy of Medical Royal Colleges, published in 2008. The premise is that a person is dead when consciousness and the ability to breathe are permanently lost. This concept is also accepted in India and Trinidad & Tobago. However, in the US, death on neurological grounds requires the cessation of all brain function, not just brainstem death.

Evolution of Diagnostic Criteria

The UK criteria for brainstem death were first published in 1976 by the Conference of Medical Royal Colleges. Initially, these were prognostic guidelines for managing deeply comatose patients on mechanical ventilators showing no recovery signs. These criteria included negative responses to bedside tests of reflexes via the brainstem and specific challenges to the brainstem respiratory centre, excluding endocrine, metabolic, and drug effects.

In 1979, the criteria were deemed sufficient for diagnosing death. This has continued, particularly for organ transplantation, although the conceptual basis has evolved. In 1995, the term "brainstem death" was formally adopted, and a new definition of death was proposed: "irreversible loss of the capacity for consciousness, combined with irreversible loss of the capacity to breathe". Irreversible cessation of brainstem function was considered equivalent to death.

Diagnosis

The UK’s diagnostic criteria for brainstem death have seen minor modifications since 1976. The most recent revision reaffirms the preconditions for its consideration:

1. The patient's deeply comatose, unresponsive state requiring artificial ventilation is due to irreversible brain damage of a known cause.
2. The absence of depressant drugs.
3. Exclusion of primary hypothermia.
4. Exclusion of reversible circulatory, metabolic, and endocrine disturbances.
5. Exclusion of reversible causes of apnoea, such as muscle relaxants and cervical cord injury.

The definitive criteria include:

1. Fixed pupils unresponsive to light.
2. No corneal reflex.
3. Absent oculovestibular reflexes (via the caloric reflex test).
4. No response to supraorbital pressure.
5. No cough reflex to bronchial stimulation or gagging response to pharyngeal stimulation.
6. No respiratory effort in response to ventilator disconnection for sufficient duration to elevate arterial partial pressure of carbon dioxide, ensuring adequate oxygenation. This dangerous apnoea test may be lethal.

Two qualified doctors must diagnose death on these criteria, repeating tests after a short period to return arterial blood gases and baseline parameters to pre-test states. These criteria are inapplicable to infants below two months.

Prognosis and Management

Testing for brainstem death may be delayed beyond the temporary absence of brainstem reflexes, as cerebral blood flow may still support brain cell recovery. There has been interest in neuronal protection through moderate hypothermia and correction of neuroendocrine abnormalities.

Studies show that even with continued ventilation, the heart stops beating within hours or days in patients meeting brainstem death or whole brain death criteria. However, there are rare cases of long-term survival, including the maintenance of bodily functions in pregnant brain-dead women until term.

Criticism

The initial use of brainstem death criteria for diagnosing death itself faced immediate protest. The basis shifted from diagnosing total brain death to defining death as the permanent loss of consciousness and spontaneous breathing. There are doubts about the general acceptance and stringency of the testing. The apnoea test, involving carbon dioxide elevation, poses risks, potentially exacerbating brain damage or causing death.

Sound scientific support for the specified bedside tests diagnosing total brainstem death is lacking. The neurological consensus indicates that consciousness arousal depends on reticular components in the midbrain, diencephalon, and pons. There are questions about the permanence of consciousness loss based on animal and human studies. Proper caution is advised before accepting a diagnosis of permanent consciousness loss without the cessation of all cerebral blood flow.

No testing of certain brainstem functions, such as oesophageal and cardiovascular regulation, is specified. Published evidence suggests the persistence of brainstem blood pressure control in organ donors. Some UK medical practitioners argue that the current diagnostic protocol does not satisfy the requirements for diagnosing brainstem death or permanent loss of consciousness and breathing capacity.

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Self-assessment MCQs (single best answer)

What is the clinical syndrome characterised by the absence of reflexes mediated through the brainstem in a deeply comatose, ventilator-dependent patient?

Which organisation published "A Code of Practice for the Diagnosis and Confirmation of Death" in the UK?

In which year were the criteria for diagnosing brainstem death first published by the Conference of Medical Royal Colleges?

Which of the following is NOT a condition that must be excluded before diagnosing brainstem death?

What is the dangerous test used to confirm brainstem death that involves ventilator disconnection?

How many qualified doctors must diagnose brainstem death, and what must they do after a short period?

What is the term adopted in 1995 to describe the irreversible cessation of brainstem function?

Which reflex is NOT tested in the UK criteria for diagnosing brainstem death?

What is the prognosis for patients who meet the brainstem death criteria?

Which of the following is a criticism of the brainstem death diagnostic criteria?