Organ donation

The shortage of organs for transplantation remains a major challenge to the transplant community, with demand consistently outstripping supply over many years (Fig. 25.3). Such a shortage has led to significant changes in practice over the last decade, with an increasing number of patients undergoing transplants from living donors, and from marginal or extended criteria deceased donors. These will be discussed in this section.

Fig. 25.3 Number of cadaveric donors and transplants in the UK, 1 April 1995 to 31 March 2009, and patients on the waiting lists at 31 March each year (ODT statistics).

Deceased donation

The identification and selection of potential donors and the subsequent approach to the family has been the focus of much attention within the United Kingdom. A UK Organ Donor Taskforce has made a series of recommendations which are aimed at increasing donor numbers. The donor transplant co-ordinators, now known as Specialist Nurses in Organ Donation, play a pivotal role in organ donation; they are now embedded within critical care areas, involved in the education of critical care staff on organ donation and transplantation, in addition to their key roles in donor management and discussion with donor families.

Current UK legislation is based on an ‘opt in’ policy, so that lack of objection must be obtained from the family in order to proceed. Other countries adopt an ‘opt out’ policy of presumed consent. There is a real need to raise public awareness of organ donation and to encourage individuals to carry organ donor cards.

Few absolute contraindications for organ donation exist; those that do are directed against the avoidance of disease transmission from donor to recipient (Table 25.3).

Table 25.3 Donor contraindications to organ donation

General contraindications

Organ-specific donor contraindications

Liver

• acute hepatitis (AST > 1000 IU/L)

• cirrhosis

• portal vein thrombosis

Kidney

• chronic kidney disease (CKD stage 3B and below, eGFR < 45)

• long-term dialysis, (that is, not relating to acute illness)

• any history of renal malignancy

• previous kidney transplant, > 6 months previously

Pancreas

• insulin dependent diabetes (excluding ICU associated insulin requirement)

• any history of pancreatic malignancy

Specific criteria must be met in order to make the diagnosis of brain-stem death (Table 25.4). Events leading up to brain death may impact upon the quality of the retrieved organs. Initially, at the point of brainstem death, compression associated with coning results in hypertension and bradycardia, known as the Cushing reflex. An autonomic storm ensues, characterized by the massive release of catecholamines, with resultant hypertension and hypoperfusion. The effect on cardiac function is the deterioration of ventricular systolic function, the liver and kidneys are affected by hypoperfusion, and it is likely that these changes contribute to non-specific endothelial cell damage, which increases the immunogenicity of the organs.

Table 25.4 Criteria for diagnosis of brain-stem death

Preconditions

• Ventilated and in a coma

• Known diagnosis for coma

• Sufficient length of time on ventilator to determine severity of brain injury

• Optimization of condition, to reverse injury

• Interval of 6–24 hours from latest intervention and testing

Exclusions

• Drug or alcohol intoxication require a delay appropriate to half-life of drug

• Time for clearance of neuromuscular blocking agents

• Primary hypothermia, metabolic and endocrine disturbances

• Coma of unknown aetiology