Beyond the numbers: rational and ethical application of outcome models for organ allocation in liver transplantation

Clinical Implications, Evaluation, and Management of Hyponatremia in Cirrhosis

Hyponatremia is the most common electrolyte abnormality in patients with decompensated cirrhosis on Liver Transplantation (LT) waiting list. Most of these patients have dilutional or hypervolemic hyponatremia secondary to splanchnic vasodilatation. Excessive secretion of the antidiuretic hormone also plays an important role. Hypervolemic hyponatremia is commonly associated with refractory ascites, spontaneous bacterial peritonitis, and hepatic encephalopathy. Although uncommon, the use of diuretics and laxatives can cause hypovolemic hyponatremia that is characterized by the striking absence of ascites or pedal edema. Clinical features are often nonspecific and depend on the acuity of onset rather than the absolute value of serum sodium. Symptoms may be subtle, including nausea, lethargy, weakness, or anorexia. However, rarely patients may present with confusion, seizures, psychosis, or coma. Treatment includes discontinuation of diuretics, beta-blockers, and albumin infusion. Hypertonic saline (3%) infusion may be used in patients with very low serum sodium (<110 mmol/L) or when patients present with seizures or coma. Short-term use of Vasopressin (V₂) receptor antagonists may also be used to normalize sodium levels prior to LT. However, all these measures may be futile, and LT remains the definite treatment in these patients to improve survival. In this review, we describe the classification, pathogenesis of hyponatremia, and its clinical implications in patients with cirrhosis. Approach to these patients along with management will also be discussed briefly.

Changing prioritization for transplantation: MELD-Na, hepatocellular carcinoma exceptions, and more

PURPOSE OF REVIEW

This article summarizes the landmark events that shaped current deceased donor liver allocation and distribution policy in the USA and to provide an update on recently approved and anticipated policy changes.

RECENT FINDINGS

For liver transplant candidates with model for end-stage liver disease more than 11, the 'MELD-Na' equation incorporating serum sodium will be used for allocation starting January 2016. The 'delay and cap' policy for hepatocellular carcinoma delays the start of model for end-stage liver disease exception by 6 months and subsequently grants 28 points, with increases every 3 months thereafter up to a maximum score at 34 points. There is new guidance for exception petitions for neuroendocrine tumors, polycystic liver disease, and primary sclerosing cholangitis. New guidelines for selecting candidates for simultaneous liver-kidney transplant are being developed that may include a 'safety net' for liver-only recipients with posttransplant renal failure. In an effort to provide broader geographic sharing of livers than in the current distribution system, new larger geographic areas are being considered.

SUMMARY

Recent policy changes were designed to reduce waitlist mortality, yet inclusion of outcomes measures in allocation and the use of larger geographic distribution units will likely guide future policy changes.

Living donor liver transplantation for high model for end-stage liver disease score: What have we learned?

AIM: To assess the impact of model for end-stage liver disease (MELD) score on patient survival and morbidity post living donor liver transplantation (LDLT).

METHODS: A retrospective study was performed on 80 adult patients who had LDLT from 2011-2013. Nine patients were excluded and 71 patients were divided into two groups; Group 1 included 38 patients with a MELD score < 20, and Group 2 included 33 patients with a MELD score > 20. Comparison between both groups was done regarding operative time, intra-operative blood requirement, intensive care unit (ICU) and hospital stay, infection, and patient survival.

RESULTS: Eleven patients died (15.5%); 3/38 (7.9%) patients in Group 1 and 8/33 (24.2%) in Group 2 with significant difference (P = 0.02). Mean operative time, duration of hospital stay, and ICU stay were similar in both groups. Mean volume of blood transfusion and cell saver re-transfusion were 8 ± 4 units and 1668 ± 202 mL, respectively, in Group 1 in comparison to 10 ± 6 units and 1910 ± 679 mL, respectively, in Group 2 with no significant difference (P = 0.09 and 0.167, respectively). The rates of infection and systemic complications (renal, respiratory, cardiovascular and neurological complications) were similar in both groups.

CONCLUSION: A MELD score > 20 may predict mortality after LDLT.

Pretransplant prediction of posttransplant survival for liver recipients with benign end-stage liver diseases: a nonlinear model

Background

The scarcity of grafts available necessitates a system that considers expected posttransplant survival, in addition to pretransplant mortality as estimated by the MELD. So far, however, conventional linear techniques have failed to achieve sufficient accuracy in posttransplant outcome prediction. In this study, we aim to develop a pretransplant predictive model for liver recipients' survival with benign end-stage liver diseases (BESLD) by a nonlinear method based on pretransplant characteristics, and compare its performance with a BESLD-specific prognostic model (MELD) and a general-illness severity model (the sequential organ failure assessment score, or SOFA score).

Methodology/Principal Findings

With retrospectively collected data on 360 recipients receiving deceased-donor transplantation for BESLD between February 1999 and August 2009 in the west China hospital of Sichuan university, we developed a multi-layer perceptron (MLP) network to predict one-year and two-year survival probability after transplantation. The performances of the MLP, SOFA, and MELD were assessed by measuring both calibration ability and discriminative power, with Hosmer-Lemeshow test and receiver operating characteristic analysis, respectively. By the forward stepwise selection, donor age and BMI; serum concentration of HB, Crea, ALB, TB, ALT, INR, Na⁺; presence of pretransplant diabetes; dialysis prior to transplantation, and microbiologically proven sepsis were identified to be the optimal input features. The MLP, employing 18 input neurons and 12 hidden neurons, yielded high predictive accuracy, with c-statistic of 0.91 (P<0.001) in one-year and 0.88 (P<0.001) in two-year prediction. The performances of SOFA and MELD were fairly poor in prognostic assessment, with c-statistics of 0.70 and 0.66, respectively, in one-year prediction, and 0.67 and 0.65 in two-year prediction.

Conclusions/Significance

The posttransplant prognosis is a multidimensional nonlinear problem, and the MLP can achieve significantly high accuracy than SOFA and MELD scores in posttransplant survival prediction. The pattern recognition methodologies like MLP hold promise for solving posttransplant outcome prediction.

Inequities of the Model for End-Stage Liver Disease: an examination of current components and future additions

PURPOSE OF REVIEW

The aim of this article is to examine the limitations of the Model for End-Stage Liver Disease (MELD) components and summarize data on promising new predictor variables.

RECENT FINDINGS

Promising modifications to MELD have been aimed at identifying more accurate measurements of the current MELD components and at improving survival prediction in earlier stages of cirrhosis. Incorporation of new measurements of cholestasis, coagulopathy and renal dysfunction should improve accuracy and reliability of MELD in predicting mortality in end stage liver disease. Direct bilirubin may be a more specific surrogate marker of liver disease than total bilirubin and further investigation of its use in liver mortality risk models in warranted. The recently developed liver-specific international normalized ratio may mitigate thromboplastin-related variation in international normalized ratio measurements. The incorporation of more accurate assessments of renal function into MELD should improve prognostic accuracy and would avert systematic biases associated with serum creatinine. Hepatic venous pressure gradient and serum sodium are promising predictors of liver-related mortality that may warrant further consideration.

SUMMARY

Modification to MELD, particularly if intended for use in liver transplant allocation, should be based upon objective, reliable, reproducible and readily available predictors; and be able to withstand rigorous model development and validation.