Figure 34.1 Trends in organ donors in the United Kingdom, 2000–2010. There are now more live donors in the United Kingdom, most of whom give a single kidney, although around 20 liver lobes are donated each year. The number of DCDs has also increased ninefold in the last 10 years, while there has been little change in the number of DBDs in the last 3 years. (Reproduced with permission from Watson CJE, Dark JH, British Journal of Anaesthesia 2012, 108: 129–142.)

Only after the subsequent certification of brain death can an individual become an organ donor (DBD). DBD donors are the most common and most important source of organs for transplantation in the Western world.

34.1.4  Donation after cardiac death

When brainstem testing has not confirmed death or it is not possible to perform brainstem death testing, donation is still possible after the confirmation of the cessation of cardiac function after cardiorespiratory arrest.

The diagnosis of death is generally performed by a registered medical practitioner not involved in any transplant activity. It is confirmed by the simultaneous and irreversible onset of apnoea and unconsciousness in the absence of circulation. This is followed by at least 5 min of observation to then confirm the absence of pupillary response to light, corneal reflexes and any motor response to supraorbital pressure [1]. Only after this can the individual become an organ donor (DCD).

The Maastricht classification [3] grouped DCDs into four categories:

• Uncontrolled DCD (no control over time of cardiac arrest)

•  Type I: Dead on arrival (irreversible cardiac arrest on the street)

•  Type II: Unsuccessful resuscitation (this includes patients brought into the emergency room while being resuscitated by the ambulance crew)

• Controlled DCD (planned cardiac arrest that occurs after withdrawal of medical care)

•  Type III: Imminent cardiac arrest in intensive care (ventilator switch-off)

•  Type IV: Cardiac arrest during or after the brain death diagnosis

Currently in the United Kingdom, there is only permission to use organs retrieved from controlled DCDs [4].

34.2  CHARACTERISTICS OF THE DECEASED DONORS FOR PAEDIATRIC LIVER TRANSPLANTATION

The liver grafts used for paediatric liver transplantation are generally obtained from DBD donors; however, there is an increasing interest in using DCD liver grafts for children. During the retrieval of a DCD liver graft, there is an important interval of time, called the warm ischaemia time (WIT), that occurs from the moment the liver does not receive adequate oxygenated blood until the time that it is perfused with a cold preservation solution. It has been established that good-quality DCD liver grafts with a WIT of <30 min can be used safely in paediatric recipients with satisfactory outcomes [5,6].

Some of the characteristics that should be considered when selecting a donor for a paediatric liver transplant recipient include the following:

• Donor age. In the United Kingdom, grafts from donors <40 years of age are preferentially allocated for organ sharing and should be considered for split liver transplantation and the grafts used in at least one paediatric recipient [7]. In general, livers from donors >40 years of age tend to be used less commonly in children. On the other hand, there is no lower-age donor limit for liver donation; however, the use of livers from donors >6 months of age has been associated with a higher incidence of hepatic artery thrombosis [8]. Livers from newborn donors can be used for hepatocyte transplantation.

• Donor blood group. An identical or compatible ABO blood group–matched graft is generally used for paediatric liver transplantation. However, for patients of <1 year of age, liver grafts from an incompatible blood group donor can be used safely [9].

• Liver graft size. Grafts from size-matched donors are not common in paediatric liver transplantation, and if these were the only grafts used, the mortality on the waiting lists would increase. Therefore, several surgical techniques have been developed to provide partial liver grafts from adult donors, including reduced grafts, split grafts and partial grafts from living donors (see Chapters 36 and 37). They are all based on the segmental anatomy of the liver, as first described by Couinaud^* [10]. The liver can be reduced to a left lateral segment (segments II and III) to overcome a donor–recipient size discrepancy of up to 10:1, but it is still possible to further reduce these grafts to transplant smaller recipients with a single segment graft (monosegment) [11].

34.3  LIVER RETRIEVAL SURGICAL TECHNIQUE FOR DBDs

Donor livers are removed as part of a multiorgan retrieval; in general, this includes the removal of heart and lungs (by a cardiothoracic retrieval team) and liver, pancreas, kidneys and small bowel (by an abdominal retrieval team). Both teams will convene simultaneously at the donor hospital to proceed with the organ retrieval.

The surgical techniques for both paediatric and adult organ retrieval are the same. In the United Kingdom, the surgical team is led by a senior surgeon with advanced surgical skills and a good knowledge of the abdominal anatomy. The team should also include an assistant surgeon, a scrub nurse and a donor technician.

The surgical retrieval technique used in DBDs can be divided into two phases:

• Donor hepatectomy (‘warm phase’)

• Liver retrieval (‘cold phase’)

34.3.1  Donor hepatectomy: warm phase

During this phase, the donor’s heart is still beating and delivering adequate oxygenated blood to the abdominal organs. It is during this phase that most of the dissection of the liver, pancreas and small bowel is performed. Identification of the detailed anatomy is easier during this time; however, latrogenic damage of critical structures (e.g. accidental division of important vessels) or acute haemodynamic decompensation of the donor (e.g. significant bleeding during dissection) could render the grafts unusable.

Once in the operating theatre, the donor is positioned in a supine position with neck extended and arms by the side. The donor’s skin is shaved from the neck to the suprapubic region, and aqueous iodine is applied before sterile draping is placed over the patient.

The surgical procedure starts with a full-length mid-line incision from the xiphisternum to the pubic symphysis (skirting the umbilicus) to open the chest and abdomen. The peritoneum is opened at the level of the mesogastrium and is carefully extended through the midline, avoiding damage to the bowel below. The falciform ligament and ligamentum teres are divided, and the abdominal retractor is positioned (Figure 34.2). At this point, it is important to visualise and report the first impressions of the liver (Box 34.1).

A complete exploration of the abdominal cavity is then performed, with special attention given to the pancreas, small bowel and colon to rule out malignancy and detect evidence of peritonitis or pathologically enlarged lymph nodes. If suspicious masses are found, biopsies and histopathological support are needed to make definite diagnosis of malignancy (Box 34.2).

The liver is then mobilised by dividing the falciform ligament up to the origin of the hepatic veins. The left triangular ligament is carefully divided to expose the lesser omentum behind the left lateral segment. The gastrohepatic ligament is inspected to detect the presence or absence of an accessory left hepatic artery arising from the left gastric artery and avoid damaging it. Division of the right triangular ligament is not recommended during the warm phase, as capsular tears on the right lobe are common due to lack of adequate space for this manoeuvre.

The porta hepatis dissection starts by carefully looking for the presence of a right accessory hepatic artery arising from the superior mesenteric artery (SMA) located on the right posterolateral aspect of the portal hepatis. At the superior margin of the pancreas, it is necessary to identify important anatomical structures close to the duodenum, such as the right gastric artery (which should be ligated), gastroduodenal artery (GDA), portal vein and common bile duct (CBD). Further dissection is performed to identify the common hepatic artery (CHA) and the splenic artery. Traction on the arterial structures should be avoided, as damage of the arterial intimal layer is common but difficult to detect, and it can cause arterial thrombosis after transplantation.

The identification and dissection of the infrahepatic inferior vena cava (IVC) is advised in order to get better control of the liver outflow after reperfusion. To do this, the second portion of the duodenum is mobilised (Kocher manoeuvre) in order to identify the portion of the IVC below the liver and above the renal veins and then encircle the vena cava with a plastic sling. This sling will guide the surgeon in case quick access is needed to the infrahepatic IVC, so as to give an outflow route to the preservation solution. (This manoeuvre is recommended when the thoracic team wants to clamp the suprahepatic IVC during perfusion.)

Figure 34.2 Midline thoracic and abdominal incision.

The lower abdominal aorta needs to be dissected, as it will be used to position one of the cannulas used to perfuse cold preservation solution. To do this, it is advisable to first identify the angle of Treitz^* at the duodenal–jejunal junction and position the whole of the small bowel to the right. The aorta is identified by palpation, and the lymphatic and perineural tissue over the distal infrarenal aorta is dissected between the inferior mesenteric artery (IMA) and the bifurcation originating the common iliac arteries. If there is excessive aortic atheroma or if there is any doubt regarding the presence of an accessory renal artery at this level, then both common iliac arteries should be exposed. One will be tied off, and the other one should be prepared for the insertion of the aortic cannula. Otherwise, the lower aorta is encircled with two strong ties (1/0 Vicryl). (Two cotton tapes could be used if there is significant atheroma inside the artery to reduce the danger of fracturing the atheroma when positioning the cannula.)

The second cannula for perfusion should be placed in the superior mesenteric vein (SMV). To do this, the transverse colon needs to be lifted to be able to dissect the bowel mesentery at 3 cm from the origin of the mesocolon. Here, the SMV should be identified and isolated for a length of 2–3 cm and encircled with two ties (1/0 Vicryl) in preparation for cannulation. (This step should not be performed if the pancreas has been allocated for transplantation.)

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