The technique of orthotopic liver homotransplantation in the pig

A simplified experimental model of large-for-size liver transplantation in pigs

OBJECTIVE

The ideal ratio between liver graft mass and recipient body weight for liver transplantation in small infants is unknown; however, if this ratio is over 4%, a condition called large-for-size may occur. Experimental models of large-for-size liver transplants have not been described in the literature. In addition, orthotopic liver transplantation is marked by high morbidity and mortality rates in animals due to the clamping of the venous splanchnic system. Therefore, the objective of this study was to create a porcine model of large-for-size liver transplantation with clamping of the supraceliac aorta during the anhepatic phase as an alternative to venovenous bypass.

METHOD

Fourteen pigs underwent liver transplantation with whole-liver grafts without venovenous bypass and were divided into two experimental groups: the control group, in which the weights of the donors were similar to the weights of the recipients; and the large-for-size group, in which the weights of the donors were nearly 2 times the weights of the recipients. Hemodynamic data, the results of serum biochemical analyses and histological examination of the transplanted livers were collected.

RESULTS

The mortality rate in both groups was 16.5% (1/7). The animals in the large-for-size group had increased serum levels of potassium, sodium, aspartate aminotransferase and alanine aminotransferase after graft reperfusion. The histological analyses revealed that there were no significant differences between the groups.

CONCLUSION

This transplant method is a feasible experimental model of large-for-size liver transplantation.

Step-by-step guide for a simplified model of porcine orthotopic liver transplant

BACKGROUND

Based on similar anatomy, physiology, and size to humans, pigs provide an excellent means for studying new therapies related to orthotopic liver transplant (OLT). Techniques that have been described to date, however, are unnecessarily complex and increase the likelihood of morbidity and adverse outcome.

MATERIALS AND METHODS

Male outbred weanling pigs underwent OLT according to our procedure, with a short anhepatic time (<20 min) and without veno-venous bypass or vasoactive substances during the anhepatic phase. Vascular anastomoses were performed identical to the clinical setting, and a simple stented choledochocholedochostomy was created.

RESULTS

The authors have performed this procedure 130 times using four transplant models: standard, whole-liver (n = 10), small-for-size (n = 48), donor after cardiac death (n = 44), and donor adenoviral gene transfection (n = 28). The average cold ischemic and anhepatic times were 302 ± 43 and 17 ± 3 min, respectively. Hypotension was successfully treated with intravenous fluids. In all cases, the recipient survived the operation and was extubated. Survival to the end follow-up varied according to the model and was 56% (73/130) for all cases. At autopsy or euthanasia, no vascular thrombosis or outflow obstruction was found. Survival was 100% for pigs transplanted with standard, whole-liver grafts (n = 10). In this group, AST and bilirubin rose during the first 24 h after graft reperfusion, while the Quick prothrombin time (QPT) fell. By the fifth postoperative day, these parameters had returned to baseline.

CONCLUSIONS

This model is straightforward and reproducible and offers surgeons and researchers the opportunity to perform OLT studies under clinically relevant conditions.

Twelve-hour liver preservation in the pig using hypothermia and hyperbaric oxygen

In an attempt to prolong successful storage of the pig liver beyond the 6–8 hours previously described from this laboratory, the addition of cell-membranestabilizing drugs to the preserving solution and the use of a potassium-rich solution were investigated. Using simple hypothermia alone, 10- and 12-hour storage was unsuccessful. Using the previously described hypothermic technique, but with the addition of hyperbaric oxygen at 3 atmospheres absolute (A.T.A.), consistently successful 12-hour preservation was achieved.

Diagnosing acute liver graft rejection: experimental application of an implantable telemetric impedance device in native and transplanted porcine livers

BACKGROUND AND AIMS

Diagnosis of acute rejection is a complex and persistent problem in liver transplantation. Focused on the use of proprietary impedance technology a porcine liver model was designed to provide immediate information for differentiation of normal and acute rejecting tissue by an implantable telemetric device.

METHODS

Electrical impedance was analyzed by electrodes implanted in vitro and in vivo in the liver of pigs, where impedance is derived from measurements of voltage transients produced in response to programmed current pulses. Consequent electric recordings in porcine livers after transplantation and after mere laparotomy were evaluated in relation to biochemical parameters and histological results of liver biopsies.

RESULTS

Acute rejection was correctly predicted in all cases and correctly excluded in the remaining 32 biopsy related impedance recordings (P<0.004). Impedance measurements not only correlated with the diagnosis from liver biopsy specimen (r=0.84, P<0.0001) but also exemplified the severity of histological acute rejection.

CONCLUSION

Impedance analysis reveals evident physiologic relation of acute liver graft rejection and electrical organ properties. Electrodes implanted in transplanted porcine livers allow running less invasive monitoring and thus early detection of rejection. The technology may have broad value in providing an immediate diagnosis of acute rejection, reducing unnecessary patient anxiety and eliminating the significant expenses associated with multiple referrals, expensive sample handling and tissue analysis.

Simplified technique of orthotopic liver transplantation in pigs

BACKGROUND

Pig models have become common in transplantation immunological research. However, in pigs, clamping of the venous splanchnic system during orthotopic liver transplantation (OLT) is responsible for high morbidity and mortality rates; therefore, the use of venovenous bypass (VVB) is advocated. Because venous bypass can also cause specific complications, a simplified method for OLT in pigs has been developed and evaluated in terms of morbidity and mortality.

METHODS

Twenty-three OLTs were performed between pairs of inbred miniature swine. Donor and recipient pairs (weighing 20-35 kg) were selected at 3-6 months of age. In the donor, the portal vein, infrahepatic vena cava, and suprahepatic vena cava were dissected, whereas the hepatic artery was preserved in continuity with the coeliac trunk and the abdominal aorta up to the iliac bifurcation. In situ cold perfusion was then performed. The recipient was prepared simultaneously by another surgical team. After total hepatectomy and complete portal and caval clamping, the suprahepatic vena cava and portal vein were sutured; VVB was not used. After completion of both venous sutures, the liver graft was reperfused. The infrahepatic vena cava was then anastomosed and unclamped. The donor aorta conduit was implanted end-to-side to the recipient infrarenal aorta, and the biliary reconstruction consisted of a cholecystojejunostomy with a Roux-Y loop.

RESULTS

Twenty of 23 (87%) animals survived more than 1 week (7-483 days). The mean anhepatic time was 29.6+/-4.12 min. Although severe hypotension was noted during the anhepatic phase, the hemodynamic status rapidly recovered and stabilized after graft reperfusion.

CONCLUSION

Simplified technique without VVB is appropriate for successfully achieving OLT in pigs.

Supraceliac aortic clamping during the anhepatic phase of experimental orthotopic liver transplantation

BACKGROUND

The pig tolerates simultaneous clamping of the liver pedicle and inferior vena cava poorly, so venovenous bypass has to be used during the anhepatic phase of experimental orthotopic liver transplantation (OLT). The aim of this work is to assess whether clamping of the supracoeliac aorta during the anhepatic phase (AP) of experimental OLT in pigs allows transplantation in stable hemodynamic conditions.

METHODS

Fourteen pigs (weight, 16 to 18 kg) received whole liver grafts from 14 age-matched donors and were subsequently divided into two groups: group I, OLT without venovenous bypass during the AP, group II, OLT with supracoeliac aortic clamping during the AP. Variables analyzed were cardiac output (CO) and related variables, mean systemic arterial pressure (MAP), mixed venous oxygen saturation (SvO2), hepatic artery and portal vein blood flow, systemic and hepatic O2 supply and uptake (SDO2, SVO2, HDO2, HVO2, respectively), liver enzymes, glucose, creatinine, and electrolytes.

RESULTS

In group I, CO, MAP, and SvO2, decreased during the AP (anhepatic) in comparison with baseline (preanhepatic) values (CO, 3.60+/-0.74, preanhepatic, v. 1.21+/-0.25 L x min(-1), anhepatic; P<.05. MAP, 97+/-12, preanhepatic, v. 43+/-17 mm Hg, anhepatic; P<.05. SvO2, 91.6+/-5.6, preanhepatic v. 70.0+/-12.5%, anhepatic; P<.05), and SDO2/SVO2 increased by 16% (preanhepatic) to 33% (anhepatic; P<.05). In group II, CO decreased during the anhepatic phase by only 21% (3.82+/-0.81, preanhepatic, v. 3.07+/-0.99 L x min(-1), anhepatic; not significant), the MAP increased significantly (100+/-8, preanhepatic, v. 135+/-4 mm Hg, anhepatic; P<.05), and SVO2, SDO2, SVO2, and SDO2/SVO2 remained unchanged. After revascularization, none of these variables differed significantly between groups, and levels of liver enzymes, glucose, creatinine, urea, and electrolytes were similar in both groups, both before and aftertransplantation.

CONCLUSIONS

Experimental OLT can be carried out in pigs without venovenous bypass, but it leads to severe hemodynamic disturbances. Clamping of the supraceliac artery during the AP is well tolerated and results in excellent hemodynamic stability, so it may prove to be a useful technique in liver transplantation in animals, such as dogs or pigs, that do not tolerate simultaneous clamping of the liver pedicle and inferior vena cava as well as human beings.

Liver transplantation in pigs: a model for studying reperfusion injury

A model of orthotopic liver transplantation in pigs was developed to investigate reperfusion injury of the liver. To have direct access to the liver for organ monitoring a relaparotomy was performed 6 h after revascularization. The details of modification in anesthesia and surgical technique are given. Salient features of the technique include (1) the use of an extremely short cuff of the donor suprahepatic caval vein, (2) the use of a central venous catheter fixed in a hepatic vein, and (3) the use of an aortic graft for standardized arterial reconstruction. Twenty-nine transplantations were performed. The total anesthetic time was 13.28 +/- 1.45 h and the operative time was 10.06 +/- 0.77 h. The animals withstood this long procedure remarkably well.

Orthotopic hepatic transplantation in the dog

Orthotopic hepatic transplantation has become a well-established treatment modality for end-stage liver disease, and research in this field is constantly evolving. Of the 34 canine liver transplants performed in this study, 17 (50%) survived more than 3 days (mean survival time 15 days). Causes of perioperative death included hemorrhage (4), anesthetic complications (3), systemic anaphylaxis (3), portal vein thrombosis (3), hepatic venous outflow block (2), and hepatic artery thrombosis (2). Gentle handling with minimal dissection of the donor liver in situ resulted in a decreased incidence of hepatic venous outflow block. The incidence of biliary leak was similar irrespective of the method of biliary reconstruction, although the incidence of acute cholangitis was 56% in the cholecystoduodenostomy group compared with 0% in the choledochocholedochostomy cohort. Using celiac to common hepatic end-to-side arterial anastomosis with preservation of the gastroduodenal artery, thrombosis of the hepatic artery was encountered in four instances, an incidence similar to previously reported studies where end-to-end hepaticohepatic arterial anastomosis or donor aortic conduit was utilized. The incidence of postoperative intestinal intussusception was reduced from 40 to 0% in those who underwent transmesenteric intestinal plication following implantation of the liver. Among short-term survivors, sepsis was the most frequent noted complication (10), followed by intestinal intussusception (6), rejection (6), and gastrointestinal bleeding (1). Among recipient dogs that survived more than 3 days, rejection was the most common cause of graft loss (5), followed by biliary leak (4) and hepatic artery thrombosis (2).

Immunosuppressive mechanism of 15-deoxyspergualin on sinusoidal lining cells in swine liver transplantation: suppression of MHC class II antigens and interleukin-1 production

To elucidate the precise mechanism of action of 15-deoxyspergualin (DSG) in swine liver transplantation, the expression of MHC class II antigens (Ia) on hepatic sinusoidal lining cells (SLC) and their production of interleukin-1 (IL-1) were examined. In our previous study, we isolated sinusoidal endothelial cells (SEC) and Kupffer cells (KC) by enzymatic digestion and centrifugal elutriation, and demonstrated that both SEC and KC present alloantigens effectively and generated IL-1 in response to allogenic or lipopolysaccharide stimulation. Animals were divided into three groups: group 1, nontransplanted normal controls (n = 3); group 2, no immunosuppressive treatment following liver transplantation (n = 5); group 3, DSG (0.8 mg/kg/day) intravenously for 7 days following liver transplantation (n = 5). At 1 week after transplantation, the three liver grafts in groups 2 and 3 were processed for the study of Ia expression and IL-1 production on SEC and KC. The expression of Ia was detected in 21.5 +/- 4.7% of SEC and 24.3 +/- 11.1% of KC in group 1. In group 3, Ia expression was suppressed compared with group 2, being 3.6 +/- 2.8% versus 22.0 +/- 2.8% for SEC (P less than 0.02) and 15.5 +/- 11.3% versus 24.3 +/- 7.1% for KC. IL-1 production by SEC and KC was respectively 11,483 +/- 3311 cpm and 9077 +/- 2161 cpm in group 1. In group 3, IL-1 production was inhibited compared with that in group 2, being 7190 +/- 883 cpm versus 19,297 +/- 5182 cpm for SEC (P less than 0.05) and 16,130 +/- 3769 cpm versus 25,857 +/- 3963 cpm for KC.(ABSTRACT TRUNCATED AT 250 WORDS)

Orthotopic porcine liver transplantation: operative technique

Considerable interest in experimental liver transplantation has been generated recently due to improvements in the results of clinical liver transplantation efforts. An operative technique for orthotopic porcine liver transplantation is presented which represents modifications of and improvements to previously published techniques. Salient features of the technique include (1) use of a diaphragmatic cuff for the suprahepatic inferior vena cava anastomosis, (2) use of a splenojugular shunt, (3) omission of caval shunts, and (4) use of isoflurane as the primary anesthetic agent. This operative technique has provided excellent survival rates in our transplanted animals.

A simple method of orthotopic liver transplantation in dogs

Orthotopic liver transplantations were performed by one team in 18 dogs using a cuff method to anastomose the portal vein, the suprahepatic vena cava and the infrahepatic vena cava without external or internal shunts. Total and warm ischemic times of donor liver averaged 124 and 32 minutes, respectively. The average occlusion time of the portal vein and the infrahepatic vena cava were 9.7 and 13.9 minutes, respectively. During this time, uncontrolled hypotension, petechiae or hemorrhagic enterogastritis did not develop. Sixteen of 18 dogs survived more than five days, and five dogs lived more than three weeks. The cause of death was not related to the cuff method in any instance. This approach proved to be a technically simple and satisfactory procedure.

[The allogeneic liver transplantation. I. Morphological and functional patterns in pig liver allografts (author's transl)]

Pigs usually reject MHC incompatible liver allografts less aggressively than skin or kidney allografts. Orthotopic liver allografts can survive undefinitely without any immunosuppression. The liver is considered to be an immunologically privileged organ. Despite this phenomenon, morphological changes and deranged liver function due to rejection reaction are regularly seen; their intensity depends on the histocompatibility antigen disparity between donor and recipient. In long-term survivors the continuous exposure of the recipient's immune system to the liver allograft results in an increasing fibrosis which can turn into liver cirrhosis being considered as the result of chronic rejection. The cholestasis represents a remarkable feature, which is mainly due to perfusion, infection and immunological reaction.

Early jaundice after pig liver transplantation

Of a series of pigs surviving orthotopic liver allotransplantation with end-to-end anastomosis of the bile duct, 70% were noted to be jaundiced at the end of the first week after transplantation. Seven animals in a subsequent series were investigated biochemically, but operative cholangiography, and by liver biopsy seven days after transplantation, when the jaundice was maximal. There was definite cholangiographic obstruction in only one animal, and this finding was subsequently confirmed at autopsy. This was also the only animal in which bile culture was positive. Jaundiced animals appeared to have more marked histological evidence of rejection than non-jaundiced ones. The jaundice was probably a result of transient rejection and usually resolved spontaneously without immunosuppression.

A model which can be used to improve the treatment of acute hepatic failure

A model using the pig from wich the liver has been removed for isolated perfusion, as a subject showing some of the features of acute hepatic failure for later treatment by cross-circulation with its own perfused liver, is desceribed. Effects of such a procedure on such a procedure on the glucose and halothane metabolism and intravascular coagulation and bleeding are detailed.

Technique of orthotopic liver transplantation in the pig

A technique of orthotopic liver transplantation in the pig is presented. Details of modifications in anaesthesia, collection of blood, and preparation of the donor liver are given. The use of a single venous by-pass, end-to-end hepatic artery anastomosis, and vagal crush with pyloromyotomy to prevent gastric ulceration have simplified the procedure and so reduced the operation time.

The natural history of liver alloone and autotransplantation in the pig

A series of 40 pig liver transplants surviving for at least 5 days is presented. Twenty orthotopic allografts are compared with 20 autograft controls, and in each group biliary drainage by a cholecystoduodenostomy (gall-bladder to duodenum anastomosis) is compared with a choledochocholedochostomy (direct bile-duct to bile-duct anastomosis).

The pigs with liver allotransplants usually demonstrated low-grade liver rejection, maximal during the second week, which subsequently spontaneously subsided without immunosuppression. However, in 15 per cent of the pigs the rejection process was more intense with death from rejection between the fifth and seventh days. Although prolonged survival was achieved in the remaining allografts, the final outcome was invariably a fatal one, owing either to gastric ulceration with haemorrhage or to infection. The mean survival time in the autograft controls was similar, and even when gastric ulceration was virtually eliminated in this group by a bile-duct to bile-duct anastomosis, death owing to infection usually occurred in the third week.

The autograft controls demonstrated the superiority of a direct bile-duct to bile-duct anastomosis in the pig, and reduced the incidence of biliary stasis and cholangitis as well as gastric ulceration in this group.

Repeated liver biopsies in both groups revealed that biochemical changes suggestive of rejection did not always represent rejection, but merely cholestasis, which could be caused by rejection or by other factors such as a cholestatic biliary anastomosis (cholecystoduodenostomy). This has important implications in human liver transplantation.

Experimental appraisal of factors involved in provision of donor livers

The results of a series of porcine orthotopic liver homotransplants have shown that hepatic damage is related almost entirely to the period of warm ischaemia following death. Low flow perfusion with modified plasma would seem to be a satisfactory method of preserving cadaveric livers for at least six hours.In man it would appear possible to use cadaver livers derived from patients who had or had not been treated with artificial ventilation during life, provided the period of warm ischaemia is not longer than 25 to 30 minutes.