A22. Definition and ethical aspects of brain-stem death

From greek.doctor

Brain death

The notion of brain death generally refers to the permanent, complete, and irreversible loss of brain function. It's defined differently in different countries according to their laws. The concept of brain death is most important in the consideration of organ donations, as the donor being brain dead is a prerequisite for many organ donations.

When a person is brain dead, there is no hope of them returning to life, but their organs may be kept alive by mechanical ventilation and life-support, allowing the best conditions for organ donation.

In Hungary

In Hungary, brain death is defined in the law as “the irreversible cessation of all functions of the entire brain, including the brain stem”. To determine brain death, the following steps must be performed:

There must be no exclusion criteria present, like:

If no exclusion criteria are present, we must confirm the total absence of brain function and that this absence is irreversible.

Confirmation of total absence of brain function:

  • No motor activity at all, neither spontaneous nor upon stimulation
  • Absent brainstem reflexes (pupillary reflexes, corneal reflexes, gag reflex, etc.)
  • Apnoea test – measures brainstem activity
    • The patient is ventilated with 100% oxygen
    • Then disconnected from the ventilator
    • The patient is observed for spontaneous breathing
    • After 10 minutes, an ABG is performed and the PaCO2 is measured
    • If PaCO2 > 60 mmHg, there’s no activity of the brainstem respiratory centre
  • (Spinal reflexes may still be present)

Confirmation of the irreversibility of absent brain function during the observation period:

Brain death must be confirmed by 3 independent specialist doctors who go through all the steps and who agree unanimously.

The duration of the observation period depends on the injury. In case of primary brain injury, it is 12 hours, in case of secondary brain injury, it is 72 hours. For children < 3 years old, the period is longer.

After being confirmed brain dead, the organ coordination office must be called to inquire as to whether the patient is a donor or not. Contact relatives to give information. Their consent is needed in case of child donors.

The patient must be treated in the ICU while waiting for surgery, to maintain optimal perfusion of donor organs. There, the following are necessary:

Organ donation

Organ donation or organ transplantation refers to removing an organ from a donor to another person who needs the organ. An organ may be donated from a live (living) donor, if the organ transplantation can be performed without permanently harming the donor too much, or it may be donated rom a brain dead donor.

Donor conditioning (donorkondícionálás) is a Hungarian term which you won’t find in international texts. I believe it refers to the period from the diagnosis of brain death to the removal of the organs, during which the eligibility of organ donation is determined. Its goal is to donate as many organs as possible in the shortest possible time, of the best quality. The term is not mentioned in the English nor the Hungarian lecture, so it’s hard to know what they mean by it and what they expect us to know.

Recognition of potential dead organ donors should begin before brain death is diagnosed. Hungary is part of Eurotransplant, an organization which organizes the allocation of donor organs in central/Eastern EU.

The most common forms of organ transplantation are:

Consent

In Hungary, the consent for organ donation is presumed, meaning that all persons are organ donors unless they have opted out of it during life. This is not the case for all countries, for example USA, Germany, and Norway rather have opt-in systems.

Procedure

After brain death we must search for a statement of the patient objecting to organ donation, usually at the organ coordination office, or in the medical records or among the closest relatives. In countries with an opt-in system, a statement of willingness to donate must be searched for instead.

While waiting for the organ(s) to be harvested from the donor, the donor must be stabilised, usually in the intensive care unit. This involves monitoring and stabilisation to ensure:

  • Haemodynamic stability (prevent hypotension and myocardial depression)
  • Stability in the coagulation system (prevent coagulopathy)
  • Hormonal balance (replacement of pituitary hormones, prevent hypothyroidism, diabetes insipidus)
  • Metabolic balance
  • Normothermia
  • Ventilation
  • Nutrition and fluid therapy

Contraindications

There are several absolute contraindications to organ donation among the donor:

  • Malignancy (except low-grade, localised tumours without metastasis)
  • Unknown cause of death, unknown patient history
  • Prion disease
  • HIV, HBV, HCV
  • Autoimmune disease
  • Inflammatory disease of the CNS
  • Cooling (< 35°C)
  • Metabolic or endocrine coma
  • Drug effects
  • Poisoning

Sepsis is not an absolute contraindication, but it should be considered to delay organ procurement until the donor has received antibiotic therapy for 48 hours.

Kidney preservation

Organ preservation can be accomplished by cold storage or pulsatile preservation. Both methods employ hypothermia to maintain the cellular viability and to reduce ischaemic injury. In cold storage, the kidneys are flushed with preservation fluid and later stored in wet ice. In pulsatile preservation there is dynamic flow of cold perfusion fluid until the transplantation. This allows for longer ischaemic time but is much more expensive.

Perfusion fluids are used to wash out blood, cool down the organs, and to equalise the intra-and-extracellular media.

Cold ischaemic time (CIT) refers to the time when the organ has perfusion and cold storage. The ideal CIT for kidney is < 18 hours, but up to 36 hours is acceptable. For other solid organ transplants, these numbers are lower.

Warm ischaemic time (WIT) refers to the time the organ has no circulation, no perfusion, and no cold storage. In ideal cases, the WIT is zero. A kidney may function up to 60 minutes of WIT, but the risk for delayed graft function or event completely non-functional kidney transplant increases after 20 minutes.