Donor Evaluation and Management
There are very few absolute contraindications for abdominal organ donation, which can be summarized in the short form CHUMP: (1) Creutzfeldt-Jakob disease, (2) active HIV infection, (3) uncontrolled donor sepsis, (4) history of melanoma or other malignancy that poses a risk for transmission regardless of the apparent disease – free period, and (5) past history of non-curable malignancy (curable malignancy such as localized small kidney tumors, localized prostate cancer, localized colon malignancy >5 years previously may be considered after careful risk/benefit assessment). In addition to these general criteria, there are organ-specific criteria for guiding the acceptance of a liver for transplantation. A history of hepatitis or alcoholism is certainly a warning sign, but both livers from HBsAg-positive and/or HCV-positive donors are currently used worldwide, and suitability for transplant must be judged on a case-by-case basis. In general, in the case of a marginal liver donor, the intraoperative assessment by the donor surgeon, in addition to liver biopsy pathological evaluation, is the best single piece of information.
Technical Aspects of Liver Procurement
A midline laparotomy from the xyphoid to the pubis is performed and the round ligament divided. The intra-abdominal organs are explored to check for eventual malignancies, and the quality of the liver is assessed: in the absence of contraindications for a transplant, a sternotomy can be performed. Of note, in the presence of prior heart surgery, the complete warm dissection should be made prior to the sternotomy. It is also prudential to isolate and encircle the aorta prior to sternotomy in order to be ready to cannulate in the event of cardiac arrest/injury at thoracotomy. A blunt dissection behind the sternum just below the jugular notch should be performed until the fingertip can be placed retrosternal around the jugular notch. The sternotomy is then performed in a cranial to caudal direction with the sternum saw to avoid left innominate vein injury. The division of the left triangular ligament allows the mobilization of the left lateral segments of the liver and the exposure of the supraceliac aorta just below the diaphragm to be encircled. The division of the falciform ligament up to the suprahepatic inferior vena cava (IVC) provides more mobility of the liver, necessary when the IVC must be divided from a cardiac graft. Before starting the dissection of the hepatoduodenal ligament, the hepatogastric ligament must be inspected by dividing the lesser omentum. This ligament is usually very thin and transparent so that any replaced or accessory left hepatic artery should be easily visible. In addition, palpation of the ventral border of the foramen of Winslow makes it possible to identify a possible accessory or replaced right hepatic artery. Variations in the hepatic arterial supply can complicate the hilar dissection in up to one third of donors.
THE HILAR STRUCTURES
The hilar structures of the liver are then dissected free; the common bile duct (CBD) is dissected on the level of the edge of the second duodenal portion after opening of the peritoneum and visualization of the duct. In difficult cases, due to a high BMI, following the cystic duct out of the gall bladder can help to identify the CBD. The CBD should be encircled from the lateral border of the hepatoduodenal ligament in order to avoid injury of the portal vein. The CBD and the gallbladder are opened and flushed with normosaline solution. The origins of the gastroduodenal, gastric, and splenic arteries are then identified and encircled and, in the case of liver only procurement, will be taped just before cross-clamping in order to increase flushing through the hepatic artery to the liver.
VASCULAR CANULATION / SOLUTION PRESERVATION
The aorta can be isolated by two approaches. One approach requires mobilization of the right colon on top of Gerota’s fascia and should be extended into a Kocher maneuver to uncover both the inferior vena cava and the abdominal aorta; the other approach is performed by opening the root of the mesentery from the Treitz fascia, along the margin of the duodenum until visualization of the right iliac vessels and ureter is achieved. The inferior mesenteric artery can be tied and divided, and the abdominal aorta, just 2–3 cm above the bifurcation, isolated and encircled. The lumbar arteries could be either tied or clipped and then cut in order to provide mobility of the aorta and facilitate the cannulation. Two umbilical tapes are placed around the dissected segment of the aorta and secured by clamps and will be used to secure aortic cannulae to the vessel. The inferior mesenteric vein (IMV) is most commonly used for access into the portal system by ligating the distal part of it but leaving it uncut to retract the vein with a mosquito clamp. Another tie is then placed around the cranial portion of the vein, using it for occlusion of the vein by retracting it while a partial incision of the vein is performed. The portal cannula can be inserted into the IMV while the tension of the occluding tie is decreased before tying it around the vein and inserted cannula. At this point, 30,000-IU heparin should be given to prevent the blood from clotting after the cross-clamping. Once these preliminary procedures have been completed, the aortic cannulae (20-F armed cannulae) can be inserted into the distal abdominal aorta and secured with the umbilical tapes.
The subdiaphragmatic aorta is now clamped (cross-clamp), and cold preservation solution is then rapidly infused through the aortic and portal cannulae; the liver flow is decompressed by dividing the inferior vena cava in the chest. The abdomen is filled with water and ice. The choice of solution for infusion and its amount varies from center to center. The quality of the flush can be assessed by evaluating the outflow of the supradiaphragmatic IVC which should become more transparent with time as the blood in the abdominal organs is replaced by the preservation solution. After the flush is completed, some of the ice is removed from the abdomen to allow the cold dissection of the structures. The gastroduodenal, gastric, and splenic arteries can now be divided. Just below the gastroduodenal artery, the portal vein can be found and can be followed back, if pancreas procurement is not performed, by dividing the head of the pancreas. The cannulae in the IMV can now be removed, the splenic vein ligated and divided, and the venous cannulae replaced in the superior mesenteric vein once it is divided from its distal branches. The superior mesenteric artery (SMA) can now be found in the retro-pancreatic laminae and should be ligated, secured to a clamp and divided in order to find the aortic plane by following back the SMA. This dissection must be made on the left side of the SMA in order to avoid damage to a possible replaced or accessory right hepatic artery. The renal arteries are usually just below the SMA. They should be visualized before the suprarenal aorta is divided. This section must be made in 45°, first looking for ostia of accessory renal arteries before performing complete separation of the aorta. By following back the splenic and gastric arteries, the celiac trunk can be visualized. The aorta must now be divided just below the diaphragm, obtaining a patch containing the celiac trunk and the origin of the mesenteric artery. At this time point, a finger is placed in the supradiaphragmatic IVC helping to identify it while the diaphragm is cut. A portion of the diaphragm should be kept with the liver to ensure that this gross and fast dissection does not damage the organ. The diaphragm is cut to the right, and the incision is then continued between the right kidney and the liver, usually dividing the adrenal gland which is a good sign that none of the adjacent organs are damaged. The location for division of the infrahepatic IVC depends on the renal veins. These are identified on both sides, and the IVC can be safely divided on the virtual line about 1 cm above the renal veins. The only structures now holding the liver in the abdomen are the diaphragmatic pillars. By keeping the liver to the right thoracic cavity and holding the aortic patch, the resected IVC, and the portal vein with its cannulae, the liver removal can be completed by cutting the diaphragmatic muscles. The liver is freed and taken out of the abdomen. A further perfusion with cool preservation solution should be performed on the back table before packing the liver in the transportation box usually with 1 l of preservation solution. The liver can now be packed in the transportation box.
Liver Disease and Perioperative Risk
The liver is the biggest intestinal organ and plays a central role in the homeostasis of different physiological systems including nutrition and drug metabolism, the synthesis of plasma proteins and haemostatic factors, as well as the elimination of different endogenous and exogenous substances. Although the liver contributes with only 3% to total body weight, given its major role in homeostasis and high energy consumption, it receives 25% of total cardiac output (CO). Two vessels contribute to the perfusion of the liver. The majority (70%) of the hepatic perfusion is provided by the portal vein, which contributes 50% of the organ’s oxygen demand. The other 50% is provided by the hepatic artery, which makes up around 30% of total liver perfusion. Hepatic arterial blood flow is mainly dependent on the organ’s metabolic demands and controlled via autoregulatory mechanisms, whereas blood supply through the portal vein depends on the perfusion throughout the whole gastrointestinal tract and the spleen. This unique, dual perfusion system provides constant perfusion rates and oxygen supply, which is crucial for adequate liver function. These high oxygen demands are reflected in a hepatic vein saturation of almost 30%.
The liver is also unique in its ability of regeneration, which allows the performance of major surgery including, amongst others, extended resections of liver tumours, living donations and so on. Many patients have normal liver function parameters when they present for liver surgery, especially when the reason for resection is metastasis or a benign liver tumour. The most common causes of liver resections are the hepatocellular carcinoma (HCC) and the cholangiocellular carcinoma (CCC). Hepatocellular carcinoma (HCC) often develops in patients with underlying liver cirrhosis; many of these patients show signs of chronic liver dysfunction (CLD).
As explained previously, the liver plays a central role in a great deal of physiological systems. Therefore, in case of chronic liver dysfunction (CLD) or liver failure, several effects on other organ systems have to be expected. Consequently liver resections and bile duct surgery as having a high risk for perioperative cardiac events, with an estimated 30-day cardiac event rate (cardiac death and myocardial infarction) of more than 5%. Patients undergoing liver surgery pose a significant challenge to treating physicians in the perioperative period. Due to the improvement of surgical techniques, the “liver patient” is becoming more and more complex, confronting surgeons, anaesthetists and intensive care personnel with difficult intra- and postoperative courses, and considerable multiorgan disorders. The cornerstones of an optimal management are careful selection of the patients, appropriate monitoring and protection of the liver and other vital organs.