The clinical importance of conventional and quantitative liver function tests in liver transplantation

Relationship Between Change Rate of Tacrolimus Clearance During Continuous Intravenous Infusion and Recipient Recovery at an Early Stage After Living Donor Liver Transplantation

BACKGROUND AND OBJECTIVE

Tacrolimus clearance (CL) is significantly altered according to recovery of liver function at an early stage after living donor liver transplantation (LDLT). In this study, we aimed to examine the impact of the change rate from postoperative day (POD) 1 in CL (ΔCL) of tacrolimus during continuous intravenous infusion (CIVI) on recipient recovery.

METHODS

A tacrolimus population pharmacokinetic model on POD1 after LDLT was developed using Phoenix NLME 1.3. The CL_POD1 was calculated using the final model. The CL_POD4-7 was calculated by dividing total daily tacrolimus dose by the area under the concentration-time curve from 0 to 24 h.

RESULTS

Data were obtained from 57 LDLT recipients, along with 540 points (177 points on POD1, 363 points on POD4-7) of tacrolimus whole blood concentrations at CIVI. The median tacrolimus CL decreased from POD1 to POD4 (from 2.73 to 1.40 L/h) and was then stable until POD7. Stepwise Cox proportional hazards regression analyses showed that the graft volume (GV)/standard liver volume (SLV) ratio (GV/SLV) and the tacrolimus ΔCL_POD6 were independent factors predicting early discharge (within 64 days median value) of recipients after LDLT [hazard ratio (HR) = 1.041, P = 0.001 and HR = 1.023, P = 0.004].

CONCLUSIONS

The tacrolimus ΔCL during CIVI immediately after LDLT in each recipient was a useful indicator for evaluation of recovery at an early stage after LDLT.

Drug metabolism and liver disease: a drug-gene-environment interaction

Despite the central role of the liver in drug metabolism, surprisingly there is lack of certainty in anticipating the extent of modification of the clearance of a given drug in a given patient. The intent of this review is to provide a conceptual framework in considering the impact of liver disease on drug disposition and reciprocally the impact of drug disposition on liver disease. It is proposed that improved understanding of the situation is gained by considering the issue as a special example of a drug-gene-environment interaction. This requires an integration of knowledge of the drug's properties, knowledge of the gene products involved in its metabolism, and knowledge of the pathophysiology of its disposition. This will enhance the level of predictability of drug disposition and toxicity for a drug of interest in an individual patient. It is our contention that advances in pharmacology, pharmacogenomics, and hepatology, together with concerted interests in the academic, regulatory, and pharmaceutical industry communities provide an ideal immediate environment to move from a qualitative reactive approach to quantitative proactive approach in individualizing patient therapy in liver disease.

Circulating sterols as predictors of early allograft dysfunction and clinical outcome in patients undergoing liver transplantation

INTRODUCTION

Sensitive and specific assessment of the hepatic graft metabolism after liver transplantation (LTX) is essential for early detection of postoperative dysfunction implying the need for consecutive therapeutic interventions.

OBJECTIVES

Here, we assessed circulating liver metabolites of the cholesterol pathway, amino acids and acylcarnitines and evaluated their predictive value on early allograft dysfunction (EAD) and clinical outcome in the context of LTX.

METHODS

The metabolites were quantified in the plasma of 40 liver graft recipients one day pre- and 10 days post-LTX by liquid chromatography/tandem mass spectrometry (LC-MS/MS). Plant sterols as well as cholesterol and its precursors were determined in the free and esterified form; lanosterol in the free form only. Metabolites and esterification ratios were compared to the model for early allograft function scoring (MEAF) which is calculated at day 3 post-LTX from routine parameters defining EAD.

RESULTS

The hepatic esterification ratio of all sterols, but not amino acids and acylcarnitine concentrations, showed substantial metabolic disturbances post-LTX and correlated to the MEAF. In ROC analysis, the low esterification ratio of β-sitosterol and stigmasterol from day 1 and of the other sterols from day 3 were predictive for a high MEAF, i.e. EAD. Additionally, the ratio of esterified β-sitosterol and free lanosterol were predictive for all days and the esterification ratio of the other sterols at day 3 or 4 post-LTX for 3-month mortality.

CONCLUSION

Low ratios of circulating esterified sterols are associated with a high risk of EAD and impaired clinical outcome in the early postoperative phase following LTX.

Liver transplantation from living donors with Gilbert's syndrome is a safe procedure for both donors and recipients

Liver transplantation (LT) has become a favorable therapeutic option for patients with end-stage liver diseases. Gilbert's syndrome (GS) is a benign condition characterized by intermittent mild jaundice due to unconjugated hyperbilirubinemia. It is not obvious whether living-donor liver transplantation (LDLT) from a donor with GS could result in a normal outcome for both the recipient and the donor. We aimed to determine whether right lobe hepatectomy is a safe procedure for living donors with GS and LT recipients. Between September 2011 and March 2015, 305 LDLT procedures using right lobe grafts were performed at Atasehir Memorial Hospital, Istanbul, Turkey. Nineteen of 305 LT candidates who had been diagnosed with GS were included in the current study. After a 12-h overnight fast, total and indirect bilirubin levels of donors and recipients were measured. The median follow-up after transplant was 16 months (range 3-36 months). The median age of donors was 25 (range 20-55 yr). Four donors (21%) were female, and 15 donors (89%) were male. The median age of donors was 51 (range 23-68 yr). Eleven recipients (57%) were female, and 8 (43%) were male. The median preoperative total bilirubin level of donors was 1.69 mg/dL (range 1.26-2.43 mg/dL) (normal range <1.2 mg/dL). The median total bilirubin level of donors on postoperative day 7 was 1.04 mg/dL (range 0.71-3.23 mg/dL). As our study has included a large number of donors with GS, it produced reliable evidence that right lobe hepatectomy is a safe procedure for living donors with GS and LT recipients.

Lidocaïne test for easier and less time consuming assessment of liver function in several hepatic injury models

PURPOSE

In this study, we developed an ex vivo functional assay to assess liver metabolic capacity adapted from the lidocaïne test in rats.

METHODS

Animals used were subjected to different models of liver injury: hypothermic ischemia (H/I, n = 8), ischemia-reperfusion (I/R, n = 8) and CCl4 induced liver cirrhosis (n = 11), and compared with sham operated rats (n = 5). Livers were then extracted and a fragment of whole tissue was incubated with lidocaïne for 15, 30, 60, 120, 240, 360, and 720 min at which both lidocaïne and its major metabolite monoethylglycinexylidide (MEGX) were measured by high performance liquid chromatography (HPLC). A histological study and biochemical assays (transaminase levels) were also performed to further evaluate and confirm our data.

RESULTS

Pharmacokinetic profile of lidocaïne metabolism in sham-operated animals revealed that the maximum concentration of MEGX is achieved at 120 min. Both lidocaïne metabolism and MEGX formation levels were significantly altered in all three models of hepatic injury. The extent of hepatic damage was confirmed by increased levels of transaminase levels and alteration of hepatocyte's structure with areas of necrosis.

CONCLUSION

Our method provides reliable and reproducible results using only a small portion of liver which allows for a fast and easy assessment of liver metabolic capacity. Moreover, our method presents an alternative to the in vivo technique and seems more feasible in a clinical setting.

Non-isotopic tyrosine kinetics using an alanyl-tyrosine dipeptide to assess graft function in liver transplant recipients - a pilot study

BACKGROUND

Although accurate assessment of liver function in liver transplant recipients is of crucial importance for optimal timing of the procedure and for determining graft viability, none of the many available methods has proven reliable in the clinical routine. Thus, a novel non-isotopic assay of tyrosine kinetics using the tyrosine-containing dipeptide L-alanyl-L-tyrosine (Ala-Tyr) was tested for its clinical feasibility in patients undergoing orthotopic liver transplantation (OLT).

METHODS

Plasma levels of tyrosine and clearance of tyrosine released after infusion of the dipetide Ala-Tyr were assessed before and one day after OLT in 10 liver transplant recipients with normal graft function, also in three organ donors and in three recipients showing poor graft function. Standard laboratory parameters (e.g. aminotransferases) and the plasma disappearance rate of indocyanine green were also measured.

RESULTS

Following uneventful OLT, tyrosine plasma levels (before 127 +/- 15 micromol/vs. post-OLT 52 +/- 6 micromol/l, P < 0.05) and kinetics (tyrosine clearance: before 206 +/- 77 ml/min vs. post-OLT 371 +/- 109 ml/min, P < 0.05) were normalized. In cases of severe graft dysfunction, tyrosine kinetics (tyrosine clearance: 238 +/- 61 ml/min) resembled the situation in end-stage liver disease, whereas no such correlation was seen with conventional markers of liver function. Organ preservation had only a minor impact on tyrosine kinetics (n.s.).

CONCLUSION

OLT rapidly normalizes both the plasma levels and the kinetics of tyrosine. Graft failure is associated with an immediate rise in plasma tyrosine levels and a delay in tyrosine elimination. Our results show that tyrosine clearance using the dipetide Ala-Tyr is a suitable non-isotopic, non-invasive indicator of graft viability in the early postoperative course following OLT.

Imaging of liver function with dedicated animal dynamic pinhole scintigraphy in rats

BACKGROUND

Non-invasive evaluation of liver function in small animal models remains a challenge. Hepatobiliary scintigraphy (HBS) enables the assessment of total and regional liver function for both uptake and excretion in larger species.

AIM

To validate quantitative liver function assessment with dedicated pinhole HBS in rats. To illustrate an application of this technique, liver function was assessed in two surgical models of liver regeneration.

METHODS

HBS was performed in 12 rats with 99mTc-mebrofenin on a dedicated animal pinhole gamma camera. The hepatic uptake rate was calculated twice by different observers to establish a normal range and the reproducibility of processing. The degree of hepatocellular injury and synthesis function were assessed by serum liver tests. Liver function was compared with liver weight. Subsequently, three groups of three rats were scanned on three separate days to assess the reproducibility of HBS. Finally, to illustrate an application of this technique, liver function was assessed in two surgical models of liver regeneration.

RESULTS

HBS in rats was feasible without mortality. The mean liver uptake rate was 77.29+/-1.29% . min(-1). Calculation of the liver uptake (% . min(-1)) was highly reproducible (r=0.95, P<0.001). There was a good correlation between liver weight and function measured by HBS at baseline and after partial resection (r=0.94, P<0.001).

CONCLUSION

HBS offers a unique combination of functional liver uptake and excretion assessment with the ability to determine the liver function reserve before and after an intervention in rats.

How much liver resection is too much?

BACKGROUND

Hepatic failure occurring after liver resection carries a poor prognosis and is a complication dreaded by surgeons. Inadequate reserve in the remaining parenchyma leads to a steady decrease in liver function, inability to regenerate, and progression to liver failure. For this reason, many methods to quantify functional hepatic reserve have been developed.

METHODS

This article reviews the main methods used in the assessment of hepatic reserve in patients undergoing hepatectomy and their use in operative decision making.

RESULTS

A range of methods to categorically quantify the functional reserve of the liver have been developed, ranging from scoring systems (such as the Child-Pugh classification) to tests assessing complex hepatic metabolic pathways to radiological methods to assess functional reserve. However, no one method has or is ever likely to emerge as a single measure with which to dictate safe limits of resectability.

CONCLUSIONS

In the future, the role of residual liver function assessment may be of most benefit in the routine stratification of risk, thus enabling both patient consent to be obtained and surgical procedure to be performed, with full information and facts regarding operative risks. However, there is no one single test that remains conclusively superior.