HPi: A Novel Parameter to Predict Graft-related Outcome in Adult Living Donor Liver Transplant

Intraoperative Hemodynamic Monitoring and Prediction of Early Allograft Dysfunction Following Living Donor Liver Transplantation: A Systematic Review

BACKGROUND

Multiple intraoperative hemodynamic parameters are associated with an increased risk of early allograft dysfunction (EAD) following living donor liver transplantation (LDLT); however, there is significant center-to-center variability in terms of which parameters are used. We sought to determine which intraoperative hemodynamic parameters are most predictive of EAD following LDLT.

METHODS

This is a systematic review following PRISMA guidelines (PROSPERO ID: CRD42023409711). Receiver operating characteristic (ROC) analyses were used to compare predictive parameters.

RESULTS

A total of 4399 articles were identified from 3 large, international databases (PubMed, Embase, and Web of Science). Eighteen articles fit the inclusion criteria. The most commonly evaluated hemodynamic parameter was the postreperfusion portal venous pressure (PVP). A postreperfusion PVP of <15-20 mmHg was consistently associated with lower rates of EAD and, in some cases, improvements in patient survival. Other hemodynamic parameters evaluated included portal venous flow, hepatic arterial flow, portal venous velocities, and the hyperperfusion index.

CONCLUSION

Hemodynamic measurements indicative of portal hyperperfusion, especially elevated PVP, have been consistently associated with the development of EAD. Intraoperative hemodynamics should be monitored on all LDLT recipients, with portal inflow modulation procedures indicated if portal hyperperfusion is present.

Role of the portal system in liver regeneration: From molecular mechanisms to clinical management

The liver has a strong regenerative capacity that ensures patient recovery after hepatectomy and liver transplantation. The portal system plays a crucial role in the dual blood supply to the liver, making it a significant factor in hepatic function. Several surgical strategies, such as portal vein ligation, associating liver partition and portal vein ligation for staged hepatectomy, and dual vein embolization, have highlighted the portal system's importance in liver regeneration. Following hepatectomy or liver transplantation, the hemodynamic properties of the portal system change dramatically, triggering regeneration via shear stress and the induction of hypoxia. However, excessive portal hyperperfusion can harm the liver and negatively affect patient outcomes. Furthermore, as the importance of the gut-liver axis has gradually been revealed, the effect of metabolites and cytokines from gut microbes carried by portal blood on liver regeneration has been acknowledged. From these perspectives, this review outlines the molecular mechanisms of the portal system's role in liver regeneration and summarizes therapeutic strategies based on the portal system intervention to promote liver regeneration.

From large-for-size to large-for-flow: A paradigm shift in liver transplantation

Liver graft-recipient matching remains challenging, and both morphologic and hemodynamic characteristics have been shown to be relevant indicators of post-transplant outcomes. However, no combined analysis is available to date. To study the impact of both morphologic and hemodynamic characteristics of liver grafts on transplantation outcomes, we retrospectively evaluated all consecutive 257 liver transplantations with prospective hemodynamic measurements from 2017 to 2020 in a single-center perspective. First, a morphologic analysis compared recipients with or without large-for-size (LFS), defined by a graft/recipient weight ratio >2.5% and excluding extreme LFS. Second, a hemodynamic analysis compared recipients with or without low portal flow (LPF; <80 mL/min per 100 g of liver tissue). Third, an outcome analysis combining LPF and LFS was performed, focusing on liver graft-related morbidity (LGRM), graft and patient survival. LGRM was a composite endpoint, including primary nonfunction, high-risk L-Graft7 category, and portal vein thrombosis. Morphologic analysis showed that LFS (n=33; 12.9%) was not associated with an increased LGRM (12.1% vs 9.4%; p =0.61) or impaired graft and patient survival. However, the hemodynamic analysis showed that LPF (n=43; 16.8%) was associated with a higher LGRM (20.9% vs 7.5%, p = 0.007) and a significantly impaired 90-day graft and patient survival. Multivariable analysis identified LPF but not LFS as an independent risk factor for LGRM (OR: 2.8%; CI:1.088-7.413; and p = 0.03), 90-day (HR: 4%; CI: 1.411-11.551; and p = 0 .01), and 1-year patient survival. LPF is a significant predictor of post-liver transplantation morbi-mortality, independent of LFS when defined as a morphologic metric alone. Consequently, we propose the novel concept of large-for-flow, which may guide graft selection and improve perioperative management of LPF.

e-GLR Score Predicts Early Graft Loss in Adult Live-Donor Liver Transplantation

Objective

This study aimed to analyze risk factors and develop a predictive model for early allograft loss due to early graft dysfunction (EGD) in adult live-donor liver transplantation (LDLT).

Methods

Data of patients who underwent LDLT from 2011 to 2019 were reviewed for EGD, associated factors, and outcomes. A homogeneous group of 387 patients was analyzed: random cohort A (n = 274) for primary analysis and random cohort B (n = 113) for validation.

Results

Of 274 recipients, 92 (33.6%) developed EGD. The risk of graft loss within 90 days was 29.3% and 7.1% in those with and without EGD, respectively (P < 0.001). Multivariate logistic regression analysis determined donor age (P = 0.045), estimated (e) graft weight (P = 0.001), and the model for end-stage liver disease (MELD) score (0.001) as independent predictors of early graft loss due to EGD. Regression coefficients of these factors were employed to formulate the risk model: Predicted (P) early graft loss risk (e-GLR) score = 10 × [(donor age × 0.052) + (e-Graft weight × 1.681) + (MELD × 0.145)] - 8.606 (e-Graft weight = 0, if e-Graft weight ≥640 g and e-Graft weight = 1, and if e-Graft weight < 640 g). Internal cross-validation revealed a high predictive value (C-statistic = 0.858).

Conclusions

Our novel risk score can efficiently predict early allograft loss following graft dysfunction, which enables donor-recipient matching, evaluation, and prognostication simply and reliably in adult LDLT.

Volumetric graft changes after liver transplantation: evidence of adaptation to recipient body size

It is believed that whole liver grafts adjust their size to fit the body size of the recipient after transplantation, despite a lack of evidence. The aim of this study was to test this hypothesis. This was a retrospective cohort study of 113 liver transplantations performed at Karolinska University Hospital. The cohort was divided based on graft volume-to-standard liver volume ratio (GV/SLV) into quartiles of small, mid, and large grafts. Serial volumetric assessment was performed on the day of transplantation and at posttransplant check-ups early (<2 mo) and late (9-13 mo) after transplantation using computed tomography (CT) volumetry. Change in GV/SLV ratio over time was analyzed with ANOVA repeated measures. A multiple regression model was used to investigate the influence of intraoperative blood flow, recipient body size, age, and relative sickness on graft volume changes. Between the three time points, mean GV/SLV ratio adapted to 0.55-0.94-1.00 in small grafts (n = 29, P < 0.001); 0.87-1.18-1.13 in midgrafts (n = 56, P < 0.001); 1.11-1.51-1.18 in large grafts (n = 28, P < 0.001). Regression analysis showed a positive correlation between posttransplant graft growth and portal flow (β = 1.18, P = 0.005), arterial flow (β = 0.17, P = 0.001), and recipient body surface area (β = 59.85, P < 0.001). A negative correlation was observed for graft weight-to-recipient weight ratio (GRWR; β = -33.12, P < 0.001). Grafts with initial GV/SLV-ratio < 0.6 adapt toward the ideal volume for recipient body size 1 year after transplantation. The disparity between graft size relative to recipient body size, and the portal and arterial perfusion, influence volumetric graft changes.NEW & NOTEWORTHY This is the first and largest human study to verify the hypothesis that whole liver grafts adjust their size to match recipient body size 1 year after transplantation-a phenomenon that has previously only been observed in experimental animal studies and human case reports. The direction of volumetric changes is driven by the disparity between graft size relative to recipient body surface area and weight, as well as the intraoperative portal- and arterial graft perfusion.

Left Lobe First With Purely Laparoscopic Approach: A Novel Strategy to Maximize Donor Safety in Adult Living Donor Liver Transplantation

OBJECTIVE

Evaluate outcome of left-lobe graft (LLG) first combined with purely laparoscopic donor hemihepatectomy (PLDH) as a strategy to minimize donor risk.

BACKGROUND

An LLG first approach and a PLDH are 2 methods used to reduce surgical stress for donors in adult living donor liver transplantation (LDLT). But the risk associated with application LLG first combined with PLDH is not known.

METHODS

From 2012 to 2023, 186 adult LDLTs were performed with hemiliver grafts, procured by open surgery in 95 and PLDH in 91 cases. LLGs were considered first when graft-to-recipient weight ratio ≥0.6%. Following a 4-month adoption process, all donor hepatectomies, since December 2019, were performed laparoscopically.

RESULTS

There was one intraoperative conversion to open (1%). Mean operative times were similar in laparoscopic and open cases (366 vs 371 minutes). PLDH provided shorter hospital stays, lower blood loss, and lower peak aspartate aminotransferase. Peak bilirubin was lower in LLG donors compared with right-lobe graft donors (1.4 vs 2.4 mg/dL, P < 0.01), and PLDH further improved the bilirubin levels in LLG donors (1.2 vs 1.6 mg/dL, P < 0.01). PLDH also afforded a low rate of early complications (Clavien-Dindo grade ≥ II, 8% vs 22%, P = 0.007) and late complications, including incisional hernia (0% vs 13.7%, P < 0.001), compared with open cases. LLG was more likely to have a single duct than a right-lobe graft (89% vs 60%, P < 0.01). Importantly, with the aggressive use of LLG in 47% of adult LDLT, favorable graft survival was achieved without any differences between the type of graft and surgical approach.

CONCLUSIONS

The LLG first with PLDH approach minimizes surgical stress for donors in adult LDLT without compromising recipient outcomes. This strategy can lighten the burden for living donors, which could help expand the donor pool.

Early allograft dysfunction after living donor liver transplantation-current concepts and future directions

Early allograft dysfunction (EAD) after liver transplantation is a significant clinical problem that negatively impacts graft and patient outcomes. The rising incidence of EAD and what it means concerning living donor liver transplantation (LDLT) is an area of great interest. However, EAD after LDLT is a complex research topic yet to be reviewed comprehensively. Most of the literature on EAD is based on experience in deceased donor liver transplantation, and limited information is available in the context of LDLT. Thus, in this review, we present an overview of EAD after LDLT and have attempted to present balanced points of view on all its aspects, such as definitions, pathogenesis, risk factors, predictive markers, and management. The review aims to broadly overview the nature and extent of ongoing research evidence on this complex topic and inform practice in the field by identifying key concepts and knowledge gaps and highlighting areas that require further inquiry.

Living Donor Liver Transplantation With Augmented Venous Outflow and Splenectomy: A Promised Land for Small Left Lobe Grafts

OBJECTIVE

Living donor liver transplantation (LDLT) using small grafts, especially left lobe grafts (H1234-MHV) (LLG), continues to be a challenge due to small-for-size syndrome (SFSS). We herein demonstrate that with surgical modifications, outcomes with small grafts can be improved.

METHODS

Between 2012 and 2020, we performed 130 adult LDLT using 61 (47%) LLG (H1234-MHV) in a single Enterprise. The median graft-to-recipient weight ratio was 0.84%, with graft-to-recipient weight ratio <0.7% accounting for 22%. Splenectomy was performed in 72 (56%) patients for inflow modulation before (n=50) or after (n=22) graft reperfusion. In LLG-LDLT, venous outflow was achieved using all three recipient hepatic veins. In right lobe graft (H5678) (RLG)-LDLT, the augmented graft right hepatic vein was anastomosed to the recipient's cava with a large cavotomy. Outcome measures include SFSS, early allograft dysfunction (EAD), and survival.

RESULTS

Graft survival rates at 1, 3, and 5 years were 94%, 90%, and 83%, respectively, with no differences between LLG (H1234-MHV) and RLG (H5678). Splenectomy significantly reduced portal flow without increasing the complication rate. Despite the aggressive use of small grafts, SFSS and EAD developed in only 1 (0.8%) and 18 (13.8%) patients, respectively. Multivariable logistic regression revealed model for end-stage liver disease score and LLG (H1234-MHV) as independent risk factors for EAD and splenectomy as a protective factor (odds ratio: 0.09; P =0.03). For LLG (H1234-MHV)-LDLT, patients who underwent prereperfusion splenectomy tended to have better 1-year graft survival than those receiving postreperfusion splenectomy.

CONCLUSIONS

LLG (H1234-MHV) are feasible in adult LDLT with excellent outcomes comparable to RLG (H5678). Venous outflow augmentation and splenectomy help lower the threshold of using small-for-size grafts without compromising graft survival.