Large-for-size liver transplantation: a flowmetry study in pigs

Does Arterialization of Portal Vein Have Any Effects in Large-for-Size Liver Transplantation? Hemodynamic, Histological, and Biomolecular Experimental Studies

BACKGROUND

In pediatric liver transplantation, the optimal size of the transplanted liver ranges between 0.8% and 4.0% of the recipient's weight. Sometimes, the graft weight exceeds this upper limit, characterizing the large-for-size condition potentially associated with reduced blood flow and worsening of ischemia-reperfusion injury. Therefore, it would be beneficial to increase the portal flow through arterialization of the portal vein. Materials and methods: Fifteen pigs underwent large-for-size liver transplants. They were divided into two groups: control (CTRL 6 animals - conventional technique) and arterialization - a shunt was established between the portal vein and the splenic artery (ART 9 animals). Hemodynamic, biochemical, histological, and molecular variables were compared. Results: Arterialization resulted in a significant increase in portal vein pressure but no changes in other hemodynamic variables, as shown in the analysis of variance. It was observed lower ALT values (p = 0.007), with no differences regarding the values of blood pH and lactate (p = 0.54 and p = 0.699 respectively) or histological variables (edema, steatosis, inflammation, necrosis, and IRI - p = 1.0, p = 0.943, p = 0.174, p = 0.832, p = 0.662, respectively). The molecular studies showed significantly increased expression of IL6 after 3 hours of reperfusion (p = 0.048) and decreased expression of ICAM immediately after reperfusion (p = 0.03). The regression analysis suggested a positive influence of portal flow and pressure on biochemical parameters. Conclusion: Arterialization of the portal vein showed no histological, biochemical, or molecular benefits in large-for-size transplantation.

Impact of Three Methods of Ischemic Preconditioning on Ischemia-Reperfusion Injury in a Pig Model of Liver Transplantation

BACKGROUND

Ischemic preconditioning (IPC), either direct (DIPC) or remote (RIPC), is a procedure aimed at reducing the harmful effects of ischemia-reperfusion (I/R) injury.

OBJECTIVES

To assess the local and systemic effects of DIPC, RIPC, and both combined, in the pig liver transplant model.

MATERIALS AND METHODS

Twenty-four pigs underwent orthotopic liver transplantation and were divided into 4 groups: control, direct donor preconditioning, indirect preconditioning at the recipient, and direct donor with indirect recipient preconditioning. The recorded parameters were: donor and recipient weight, graft-to-recipient weight ratio (GRWR), surgery time, warm and cold ischemia time, and intraoperative hemodynamic values. Blood samples were collected before native liver removal (BL) and at 0 h, 1 h, 3 h, 6 h, 12 h, 18 h, and 24 h post-reperfusion for the biochemical tests: aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), creatinine, BUN (blood urea nitrogen), lactate, total and direct bilirubin. Histopathological examination of liver, gut, kidney, and lung fragments were performed, as well as molecular analyses for expression of the apoptosis-related BAX (pro-apoptotic) and Bcl-XL (anti-apoptotic) genes, eNOS (endothelial nitric oxide synthase) gene, and IL-6 gene related to inflammatory ischemia-reperfusion injury, using real-time polymerase chain reaction (RT-PCR).

RESULTS

There were no differences between the groups regarding biochemical and histopathological parameters. We found a reduced ratio between the expression of the BAX gene and Bcl-XL in the livers of animals with IPC versus the control group.

CONCLUSIONS

DIPC, RIPC or a combination of both, produce beneficial effects at the molecular level without biochemical or histological changes.

Long-Term Outcomes of Abdominal Wall Reconstruction with Expanded Polytetrafluoroethylene Mesh in Pediatric Liver Transplantation

Background: Large-for-size syndrome caused by organ size mismatch increases the risk of abdominal compartment syndrome. Massive transfusion and portal vein clamping during liver transplantation may cause abdominal compartment syndrome (ACS) related to mesenteric congestion. In general pediatric surgery—such as correcting gastroschisis—abdominal wall reconstruction for the reparation of defects using expanded polytetrafluoroethylene is an established method. The purpose of this study is to describe the ePTFE-Gore-Tex closure method in patients with or at a high risk of ACS among pediatric liver transplant patients and to investigate the long-term prognosis and outcomes. Methods: From March 1988 to March 2018, 253 pediatric liver transplantation were performed in Seoul National University Hospital. We retrospectively reviewed the cases that underwent abdominal wall reconstruction with ePTFE during liver transplantation. Results: A total of 15 cases underwent abdominal closure with ePTFE-GoreTex graft. We usually used a 2 mm × 10 cm × 15 cm sized Gore-Tex graft for extending the abdominal cavity. The median follow up was 59.5 (17–128.7) months and there were no cases of ACS after transplantation. There were no infectious complications related to ePTFE implantation. The patient and graft survival rate during the study period was 93.3% (14/15). Conclusions: Abdominal wall reconstruction using ePTFE is feasible and could be an alternative option for patients with a high risk of ACS.

Protein Profiles of Pretransplant Grafts Predict Early Allograft Dysfunction After Liver Transplantation From Donation After Circulatory Death

BACKGROUND

Predicting the development of early allograft dysfunction (EAD) following liver transplantation (LT) remains challenging for transplant clinicians. The objectives of this study are to investigate the potential relationship between the protein profiles of pretransplant grafts and the onset of EAD, and then combine with clinical parameters to construct a mathematically predictive model.

METHODS

Clinical data of 121 LT procedures from donation after circulatory death at the authors' center were analyzed. The expression levels of 7 studied proteins were determined by immunohistochemistry. Another independent cohort of 37 subjects was designed for further validation of the predictive model.

RESULTS

With an incidence of 43.0% (52/121), EAD was linked to significantly increased risk of acute kidney injury and renal replacement therapy, as well as reduced 6-month patient and liver graft survival. Allograft weight and high intrahepatic vascular endothelial growth factor (VEGF) expression were identified as independent risk factors of EAD and survival outcomes. Liver grafts with high VEGF expression exhibited delayed functional recovery within the first postoperative week. The combination of VEGF overexpression and EAD yielded the highest frequency of renal dysfunction and the worst survival. Based on allograft weight and intrahepatic VEGF expression, an EAD risk assessment model was developed. The incidence of EAD differed significantly between grafts with risk scores ≥-1.72 and <-1.72. The model functioned well in the validation cohort.

CONCLUSIONS

Pretransplant intrahepatic protein profiling contributes to the estimation of early graft performance and recipient outcomes following LT. The predictive model could allow for an accurate prediction of EAD.

Large-for-Size Orthotopic Liver Transplantation: a Systematic Review of Definitions, Outcomes, and Solutions

BACKGROUND

We systematically reviewed the literature on definitions and outcomes of large-for-size (LFS) syndrome in orthotopic liver transplantation (LT).

METHODS

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The Cochrane Library, PubMed, and Embase were searched (January 1990-January 2019) for studies reporting LFS in LT. Primary outcomes were definitions and mortality of LFS LT.

RESULTS

Eleven studies reporting patients with LFS LT were identified. Four different formulas (graft-to-recipient weight ratio (GRWR), body surface area index (BSAi), donor standardized total liver volume (sTLV)-to-recipient sTLV ratio, and graft weight/right anteroposterior distance (RAP) ratio) with their critical thresholds were found. There were 81 patients (54% women) with a median weight and height of 62.5 kg (range, 40-105 kg) and 165 cm (range, 145-180 cm). The median graft weight was 1772 g (range, 1290-2400 g), and the median GWRW was 2.77% (range, 2.1-4.00%). Graft venous outflow obstruction was described in seven patients (8.6%). At the time of LT, fascial closure was not achieved in 24 patients (29.6%) and the graft size was reduced by a liver resection in three patients (3.7%). Thirteen deaths (16%) were reported in the first 90 postoperative days with two patients undergoing re-transplant.

CONCLUSIONS

LFS LT remains heterogeneously defined but characterized by high mortality rates despite the use of tailored surgical solutions (graft reduction and open abdomen). A composite definition is proposed in order to better describe LFS clinical syndrome.

Monitoring intra-abdominal pressure after liver transplantation in children

IAH after LTX can impair perfusion and threaten graft viability. This study aimed to assess the feasibility of longitudinal IAP measurements as an IAH screening method in children after LTX. A cohort of 23 children with a mean age (range) 3.1 (3 months-14 years) who underwent LTX between May 2017 and February 2018 were evaluated retrospectively. Longitudinal IAP measurements were compared to bedside Doppler US monitoring data. In total, 425 IAP measurements and 257 US examinations were performed. The mean ± SD (range) time expenditure for IAP measurement was 1.9 ± 0.4 (0.5-3.2) minutes. The mean post-operative IAP was 7.9 ± 3.6 (1-25) mm Hg. IAH (IAP ≥ 10 mm Hg) was noted in 102 (24%) of 257 measurements. Agitation had a significant impact on IAP (estimate: 9.3 mm Hg, CI: 6.72-11.97, P < .01). In patients with TAC, IAP was increased (6.7 ± 2.1 vs 8.7 ± 3.1 mm Hg, P = .02) while peak portal venous velocities decreased (38 ± 27 vs 26 ± 22 cm/s, P = .03) after patch reduction. An abdominal compartment syndrome with severely impaired vascular flow was noted in one patient. Episodes of elevated IAP were noted in a large proportion of patients, underscoring the need for IAP monitoring in pediatric liver transplant recipients. The safety and low time expenditure associated with IAP measurement could be included easily into standard nursing procedures for these patients.

In Situ Left Lateral Sectionectomy in Deceased Donor Liver Transplantation: Could This Be Another Solution for a Large-for-Size Graft? A Case Report

BACKGROUND

Large-for-size (LFS) graft should be avoided when performing an adult deceased donor liver transplantation (DDLT) as it is associated with abdominal compartment syndrome, severe graft injury, and primary graft nonfunction. When inadvertently facing with LFS graft intraoperatively, the most commonly reported approach has been a surgical reduction of the right lobe despite its technical difficulty in addition to ongoing coagulopathy after graft reperfusion. We report a case where we performed a left lateral sectionectomy instead of a right lobe modification.

CASE REPORT

A 44-year-old 58.4 kg female patient was admitted with drug-induced acute hepatic failure and underwent an emergency DDLT. The donor was a 51-year-old 60.0 kg man. At the time of procurement, the liver was noted to be hypertrophic. The estimated graft/recipient weight ratio was 3.49%. After completing the vascular and bile duct anastomosis, the abdomen could not be closed due to its large graft size. Because of the hypertrophic left lateral lobe and ongoing coagulopathy, we decided to perform an in situ left lateral sectionectomy rather than right posterior sectionectomy or right hemihepatectomy. The next day, the liver function failed to improve, and the patient's blood pressure began to decline gradually. Computed tomography showed severe inferior vena cava (IVC) compression by the graft, and the patient underwent transjugular IVC stent placement. Soon after, the patient's blood pressure improved and liver function gradually normalized. The patient was discharged uneventfully on postoperative day 45.

CONCLUSION

Under specific conditions, in situ left lateral sectionectomy is a solution for unexpected LFS graft during DDLT.

A Retrospective Cohort Study of Risk Factors for Surgical Site Infection Following Liver Transplantation

Background:

Surgical site infection is an important complication in the postoperative period among liver transplant recipients. However, little is known about the risk factors in this patient group. Therefore, the objective of this study was to analyze the incidence and risk factors for surgical site infections among adult liver transplant recipients.

Methods:

Medical records of adult liver transplant recipients from January 1, 2009, to December 31, 2015, were analyzed in this retrospective cohort study.

Results:

We enrolled 156 recipients’ medical records. Forty-two (26.9%) cases of surgical site infections were identified. The main isolated microorganisms were methicillin-resistant Staphylococcus species, extended spectrum β-lactamase-producing Klebsiella species, carbapenem-resistant Pseudomonas aeruginosa, carbapenem-resistant Acinetobacter baumannii, and vancomycin-susceptible Enterococcus faecalis. We found that long operative times (≥487 minutes) and differences in body mass index between donor and recipient (≥1.3 kg/m2) increased the risk for surgical site infections by approximately 5 times (odds ratio [OR], 5.5; 95% confidence interval [CI], 2.5-11.8), and capillary glycemia ≥175 mg/dL in the first 96 postoperative hours increased the risk by approximately 3 times (OR, 2.97; 95% CI, 1.43-6.17).

Conclusions:

There was a high incidence of surgical site infections among the studied population and that some risk factors identified differ from those reported in the scientific literature.

Analysis of the reversibility of biliary cirrhosis in young rats submitted to biliary obstruction

BACKGROUND/PURPOSE

Biliary atresia and other liver biliary obstructions are relevant conditions in pediatric surgery due to their progression to biliary cirrhosis and indication for liver transplantation. It is known that the period during which biliary obstruction persists determines the development of cirrhosis and its reversibility after a biliary drainage procedure. However, no time or histological markers of biliary cirrhosis reversibility have been established.

MATERIALS AND METHODS

One hundred and twenty-nine young Wistar rats underwent surgery for ligation of the common bile duct and were maintained until 8weeks. A part of these animals was submitted to biliary drainage surgery at 2, 3, 4, 5, or 6weeks after the initial procedure. After cyst formation at the site of obstruction, cyst-jejunal anastomosis was performed to restore bile flow. After biliary obstruction and drainage, liver samples were collected for histological and molecular analysis of the genes responsible for collagen deposition and fibrosis.

RESULTS

The mortality rates were 39.8% and 56.7% after the first and second procedures, respectively. Ductular proliferation (p=0.001) and collagen deposition increased according to the period under obstruction (p=0.0001), and both alterations were partially reduced after biliary drainage. There were no significant differences in the values of desmin and α-actin according to the period during which the animal remained with biliary obstruction (p=0.09 and p=0.3, respectively), although increased values of transforming growth factor beta 1 (TGFβ1) occurred after 8weeks (p=0.000). Desmin levels decreased, and α-actin and TGFβ1 levels increased according to the period under obstruction. The molecular alterations were partially reversed after biliary drainage.

CONCLUSIONS

The histologic and molecular changes in the liver parenchyma promoted by biliary obstruction in the young animal can be partially reversed by a biliary drainage procedure.

Extreme large-for-size syndrome after adult liver transplantation: A model for predicting a potentially lethal complication

There is currently no tool available to predict extreme large-for-size (LFS) syndrome, a potentially disastrous complication after adult liver transplantation (LT). We aimed to identify the risk factors for extreme LFS and to build a simple predictive model. A cohort of consecutive patients who underwent LT with full grafts in a single institution was studied. The extreme LFS was defined by the impossibility to achieve direct fascial closure, even after delayed management, associated with early allograft dysfunction or nonfunction. Computed tomography scan-based measurements of the recipient were done at the lower extremity of the xiphoid. After 424 LTs for 394 patients, extreme LFS occurred in 10 (2.4%) cases. The 90-day mortality after extreme LFS was 40.0% versus 6.5% in other patients (P = 0.003). In the extreme LFS group, the male donor-female recipient combination was more often observed (80.0% versus 17.4%; P < 0.001). The graft weight (GW)/right anteroposterior (RAP) distance ratio was predictive of extreme LFS with the highest area under the curve (area under the curve, 0.95). The optimal cutoff was 100 (sensitivity, 100%; specificity, 88%). The other ratios based on height, weight, body mass index, body surface area, and standard liver volume exhibited lower predictive performance. The final multivariate model included the male donor-female recipient combination and the GW/RAP. When the GW to RAP ratio increases from 80, 100, to 120, the probability of extreme LFS was 2.6%, 9.6%, and 29.1% in the male donor-female recipient combination, and <1%, 1.2%, and 4.5% in other combinations. In conclusion, the GW/RAP ratio predicts extreme LFS and may be helpful to avoid futile refusal for morphological reasons or to anticipate situation at risk, especially in female recipients. Liver Transplantation 23 1294-1304 2017 AASLD.

Does a meso-caval shunt have positive effects in a pig large-for-size liver transplantation model?

In pediatric liver transplantations with LFS grafts, higher incidences of graft dysfunction probably occur due to IRI. It was postulated that increasing the blood supply to the graft by means of a meso-caval shunt could ameliorate the IRI. Eleven pigs underwent liver transplantation and were divided into two groups: LFS and LFS+SHUNT group. A series of flowmetric, metabolic, histologic, and molecular studies were performed. No significant metabolic differences were observed between the groups. One hour after reperfusion, portal flow was significantly lower in the recipients than in the donors, proving that the graft was maintained in low portal blood flow, although the shunt could promote a transient increase in the portal blood flow and a decrease in the arterial flow. Finally, it was verified that the shunt promoted a decrease in inflammation and steatosis scores and a decrease in the expression of the eNOS gene (responsible for the generation of nitric oxide in the vascular endothelium) and an increase in the expression of the proapoptotic gene BAX. The meso-caval shunt was responsible for some positive effects, although other deleterious flowmetric and molecular alterations also occurred.

Size mismatch in liver transplantation

Size mismatch is an unique and inevitable but critical issue in live donor liver transplantation. Unmatched metabolic demand of recipient as well as physiologic mismatch aggravates the damage to liver graft, inevitably leading to graft failure on recipient. Also, an excessive resection of liver graft for better recipient outcome in live donor liver transplant may jeopardize the healthy donor well-being and even put donor life in danger. There is a fine balance between resected graft volume required to meet the recipient's metabolic demand and residual graft volume required for donor safety. The obvious clinical necessity of finding that balance has prompted a clinical need and promoted the improvement of knowledge and development of management strategies for size-mismatched transplants. The development of the size-matching methodology has significantly improved graft outcome and recipient survival in live donor liver transplants. On the other hand, the effect of size mismatch in cadaveric transplants has never been observed as being so pronounced. The importance of matching of the donor recipient size has been unrecognized in cadaveric liver transplant. In this review, we attempt to summarize the current most updated knowledge on the subject, particularly addressing the definition and complications of size-mismatched cadaveric liver transplant, as well as management strategies.

Serial volumetric assessment of large for size liver grafts after whole cadaveric liver transplant in adults: do large liver grafts shrink in size?

BACKGROUND

After whole graft orthotopic liver transplantation (OLT), adaptation of the large grafts' volume to recipient weight is widely accepted despite the paucity of evidence on this subject.

METHODS

Thirty nine patients with GRWR > 2.5% were included in this study and subsequently divided into two groups with 3 ≥ GRWR > 3%. Patients had CT scans at three predetermined time points after OLT used for measuring the liver volume. The objective of this study is to evaluate the volumetric changes of whole large liver grafts after adult OLT.

RESULTS

At LT, the mean graft recipient body weight ratio (GRWR) was 3.1 ± 0.4%. The mean liver weight was 1881 ± 68 g at LT, 2014 ± 99 ml at one week, 1725 ± 126 ml at 3 months, and 1632 ± 117 (ml) at >6 months. There is an initial increase at 1 week after LT and a subsequent decrease of liver volume on later measurements. None of the late volume measurements were significantly different from the initial graft volume at liver transplant in pair wise comparisons ANOVA repeated measures (p > 0.05). Similarly, the mean GRWR did not change significantly between the initial calculation at transplantation date and the subsequent measurements during the different study time points (F = 0.04, p = 0.96) with a mean of 3.1% (95% CI = 2.2-4.2). AUC ROC discriminated a cutoff of 3% for the initial GRWR above which grafts tend to decrease in size over time (c statistics = 0.74, p = 0.036). In a Clustered ANOVA repeated measures, there was no significant difference in the changes of liver volume between both groups. However, patients with GRWR > 3 showed a trend towards a latent reduction in volume over the tracing period. There was a tendency, but none significant; towards a higher bilirubin, AST, ALT levels over the first postoperative days in recipients with GRWR > 3.

CONCLUSION

Large grafts do not significantly decrease in size. Nonetheless, grafts weighing >3% of the GRWR show a different trend towards decrease in size over time.

Swine model in transplant research: Review of anaesthesia and perioperative management

Pigs are one of most common animal species to be used in biomedical models due to their many anatomical visceral similarities with humans, particularly with regards to transplantation. Despite this use, in many of the researches in which pigs are selected for transplantation, the anaesthesia used is an adaptation of human anaesthesia and presents some limitations such as a reduced analgesia a limited control in perioperative period. In this review we show some of the most important conditions in the preanaesthetic management and of swine as well as we review of anaesthetic protocols for the most common types of swine model of transplantation.

Effects of ischemic preconditioning in a pig model of large-for-size liver transplantation

OBJECTIVE

In most cases of pediatric liver transplantation, the clinical scenario of large-for-size transplants can lead to hepatic dysfunction and a decreased blood supply to the liver graft. The objective of the present experimental investigation was to evaluate the effects of ischemic preconditioning on this clinical entity.

METHODS

Eighteen pigs were divided into three groups and underwent liver transplantation: a control group, in which the weights of the donors were similar to those of the recipients, a large-for-size group, and a large-for-size + ischemic preconditioning group. Blood samples were collected from the recipients to evaluate the pH and the sodium, potassium, aspartate aminotransferase and alanine aminotransferase levels. In addition, hepatic tissue was sampled from the recipients for histological evaluation, immunohistochemical analyses to detect hepatocyte apoptosis and proliferation and molecular analyses to evaluate the gene expression of Bax (pro-apoptotic), Bcl-XL (anti-apoptotic), c-Fos and c-Jun (immediate-early genes), ischemia-reperfusion-related inflammatory cytokines (IL-1, TNF-alpha and IL-6, which is also a stimulator of hepatocyte regeneration), intracellular adhesion molecule, endothelial nitric oxide synthase (a mediator of the protective effect of ischemic preconditioning) and TGF-beta (a pro-fibrogenic cytokine).

RESULTS

All animals developed acidosis. At 1 hour and 3 hours after reperfusion, the animals in the large-for-size and large-for-size + ischemic preconditioning groups had decreased serum levels of Na and increased serum levels of K and aspartate aminotransferase compared with the control group. The molecular analysis revealed higher expression of the Bax, TNF-alpha, I-CAM and TGF-beta genes in the large-for-size group compared with the control and large-for-size + ischemic preconditioning groups. Ischemic preconditioning was responsible for an increase in c-Fos, IL-1, IL-6 and e-NOS gene expression.

CONCLUSION

Ischemia-reperfusion injury in this model of large-for-size liver transplantation could be partially attenuated by ischemic preconditioning.