Non-heart beating donation

Introduction
Prior to the introduction of brain-stem death into law in the mid to late 1970s, all organ transplants from cadaveric donors came from non-heart beating donors (NHBD).

Brain-stem dead donors, however, lead to better results as the organs were perfused with oxygenated blood until the point of perfusion and cooling at organ retrieval, and so non-heart beating donors were generally no longer used except in Japan, where brain-stem death was not legally (until very recently) or culturally (still) recognised.

However, a growing discrepancy between demand for organs and their availability from brain-stem dead donors has lead to a re-examination of using non-heart beating donors, and many centres are now using such donors to expand their potential pool of organs.



Tissue donation (corneas, heart valves, skin, bone) has always been possible for non-heart beating donors, and many centres now have established programmes for kidney transplants from such donors. A few centres have also moved into NHBD liver and lung transplants. Many lessons have been learnt since the 1970s, and results from current NHBD transplants are comparable to transplants from brain-stem dead donors.

Maastricht classification
NHBDs are grouped by the Maastricht classification (1995; amended 2003):

I Brought in dead
II Unsuccessful resuscitation
III Awaiting cardiac arrest
IV Cardiac arrest after brain-stem death
V Cardiac arrest in a hospital inpatient (new category, 2003)

Categories I and II are termed uncontrolled and categories III to V are controlled. Only tissues can be taken from category I donors. Category II donors are patients who have had a witnessed cardiac arrest outside hospital, have cardiopulmonary resusciation by trained paramedics commenced within 10 minutes but who cannot be successfully resuscitated. Category III donors are patients on intensive care units with non-survivable injuries who have treatment withdrawn; where such patients wished in life to be organ donors, the transplant team can attend at the time of treatment withdrawal and retrieve organs after cardiac arrest has occurred.

Organs that can be used:
Kidneys can be used from category II donors, and all organs except the heart can potentially be used from category III, IV and V donors. An unsuccessful kidney recipient can remain on dialysis, unlike recipients of some other organs, meaning that a failure will not result in death.

Kidneys from uncontrolled (category II) donors must be assessed with care as there is otherwise a high rate of failure. Many centres have protocols for formal viability assessment. Relatively few centres worldwide retrieve such kidneys, and leaders in this field include the transplant units in Maastricht (the Netherlands), Newcastle upon Tyne and Leicester (United Kingdom), Madrid (Spain), and Washington, DC (United States).

Livers and lungs for transplant can only be taken from controlled donors, and are still somewhat experimental as they have only been performed successfully in relatively few centres. In the United Kingdom, NHBD liver transplants are currently only performed in Newcastle upon Tyne, Leeds and King's College Hospital London.

Procedure for uncontrolled donors
Following declaration of death, cardiopulmonary resusciation (CPR) is continued until the transplant team arrive. A stand-off period is observed after cessation of CPR to ensure that death has occurred; this is usually from 5 to 10 minutes in length and varies according to local protocols.

Once the stand-off period has elapsed, a cut down is performed over the femoral artery, and a double-balloon triple-lumen (DBTL) catheter is inserted into the femoral artery and passed into the aorta. The balloons are inflated to occlude the aorta above and below the renal arteries (any donor blood specimens required can be taken before the top balloon is inflated). A pre-flush with streptokinase or another thrombolytic is given through the catheter, followed by 20 litres of cold kidney perfusion fluid; the opening of the lumen is between the balloons so that most of the flush and perfusion fluid goes into the kidneys. Another catheter is inserted into the femoral vein to allow venting of the fluid.

Once full formal consent for organ donation has been obtained from relatives, and other necessary formalities such as identification of the deceased by the police and informing the Coroner (in the UK), the donor is taken to the operating room, and the kidneys and heart valves retrieved.

Procedure for controlled donors
If the liver or lungs are felt to be suitable for transplantation, then the donor is usually taken directly to the operating room after cardiac arrest, and a rapid retrieval operation is performed once a 10 minute stand-off period has elapsed. This is similar to a normal multi-organ retrieval, but prioritises rapid cannulation, perfusion and cooling with ice, with dissection following later.

If only the kidneys are suitable for retrieval, either rapid retrieval or cannulation with DBTL catheter can be used. Use of a DBTL catheter allows relatives of the deceased to see them after death, but the donor must be taken to the operating room as soon as possible.

The formalities necessary for donation can usually be carried out prior to treatment withdrawal in controlled donation, so early retrieval should be possible.

Category IV donors (who are already brain-stem dead), should either proceed as for a normal multi-organ retrieval – if this has already started – or should be managed as a category II or III as appropriate to the circumstances of cardiac arrest.

Results of NHBD transplantation
NHBD kidney transplantation, from both controlled and uncontrolled donors, has been shown to have almost identical graft survival times and long-term function as kidneys from brain-stem dead donors. In the short-term they are prone to delayed graft function of around 7-14 days (this does not affect long term function in NHBD kidneys) and have a failure rate of around 5-10% (compared to 3-5% for kidneys from brain-stem dead donors).

There is not as much long-term data for NHBD liver transplants, but published results are promising. Unlike in kidneys, where delayed graft function simply means a need for dialysis, delayed graft function in livers is fatal, which is why only controlled donors are used for livers. Intra-hepatic biliary strictures are a complication more common in NHBD livers than in brain-stem dead donors. Many transplant surgeons feel that NHBD livers should not be used to transplant acutely sick patients with acute liver failure.

Long-term data on NHBD lung transplants is not yet available.

Ethical issues
Certain ethical issues are raised by NHBD transplantation, and require due sensitivity to ensure that ethical standards are maintained.

In category II uncontrolled donors, the donor may die and the transplant team arrive before the donor's next-of-kin can be contacted. It is controversial whether cannulation and perfusion can be started in these circumstances. On one hand, it can be considered a violation of the potential donor's autonomy to cannulate before their in-life wishes are known. On the other hand, delay in cannulation may mean that a patient's strongly-held wish to be donor cannot be respected. Many ethicists also feel that a doctor's duty of care to the still living outweighs any duty of care to the dead. The compromise reached is usually to cannulate if there is any evidence of a wish to donate (such as a donor card or registration as a donor) even in the absence of next-of-kin.

For category III donors, treatment is being withdrawn from a living person, who will then die and become a donor. It is important that the decisions that injuries are non-survivable, continued treatment is futile and that withdrawal is in the patient's best interests be made completely independently of any consideration of suitability as an organ donor. Withdrawal of life-prolonging treatment in the face of a hopeless prognosis should be a standard part of patient care, irrespective of whether a patient can be a donor. Only after such decisions have been firmly made should a patient be considered as a potential organ donor. Although such treatment can be continued until the transplant team arrive, no additional treatment should be started to improve the organs – until the point of death, the patient should be treated exactly as any other dying patient.

Source: Wikipedia, the free encyclopedia.
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