Timing of liver transplantation

Review article: the assessment of liver function using breath tests

BACKGROUND

Hepatologists have long sought to develop a test for assessing liver function, but this aim has been stalled by the complexity of the liver and its diverse functions. Results of metabolic tests, including breath tests, correlate with clinical and histological parameters of patients with liver disorders; however, these tests tend to be cumbersome and impractical for everyday use. The recent development of a real-time, point-of-care liver function breath test has made it straightforward to assess the metabolic function of the liver.

AIM

To review the available data on the use of breath tests for assessing liver reserve in various conditions and their application in various clinical hepatology settings.

RESULTS

The (13)C-methacetin breath test enables accurate follow-up of patients with acute or chronic liver damage, where overall hepatic function is significantly suppressed by known causes of liver disorders, including acute, sub-acute or chronic conditions. The metabolic breath test can detect both gradual and spontaneous improvements in liver function and the effects of treatment.

CONCLUSIONS

Breath testing that provides continuous quantification of methacetin metabolism may be a sensitive tool for the diagnosis and follow-up of patients with liver disorders.

A model to predict the development of mental status changes of unclear cause after liver transplantation

Postoperative mental status changes are common after liver transplantation (LT). A clear cause of these mental status changes cannot be identified in a significant proportion of patients. In adult liver transplant recipients, our goals are to: (1) identify independent predictors for the development of post-LT mental status changes of unclear cause and (2) derive a practical formula to predict the risk for developing this complication by using simple clinical parameters. Eligible patients had documented mental status changes of at least 3 days' duration, occurring within 1 month of LT. Exclusion criteria were known structural brain disorders, major organ dysfunction, or metabolic causes of altered mentation. Age- and sex-matched controls were liver transplant recipients without post-LT neurological sequelae. Data were collected on preoperative, intraoperative, and postoperative variables. Univariate and multivariate analyses were performed to detect factors predictive of the development of post-LT mental status of unclear cause. There were 40 cases and 40 controls. Independent predictors of mental status changes of unclear cause included alcoholic and metabolic liver diseases; pre-LT mechanical ventilation; Model for End-Stage Liver Disease (MELD) score greater than 15; and nonelective LT. Using these four preoperative factors, a simple predictive rule was developed. Risk for developing altered mental status of unclear cause after LT was 78% to 89% if all four predictors were present versus 0.8% to 2.4% if no predictors were present. In conclusion, alcoholic and metabolic liver diseases, pre-LT mechanical ventilation, MELD score greater than 15, and nonelective LT are independent predictive factors for post-LT altered mental status changes of unclear cause. A simple model can be used to calculate the risk for developing altered mental status post-LT.

Model for end-stage liver disease and Child-Turcotte-Pugh score as predictors of pretransplantation disease severity, posttransplantation outcome, and resource utilization in United Network for Organ Sharing status 2A patients

The Model for End-Stage Liver Disease (MELD) has been proposed as a replacement for the Child-Turcotte-Pugh (CTP) classification to stratify patients for prioritization for orthotopic liver transplantation (OLT). Improved classification of patients with decompensated cirrhosis might allow timely OLT before the development of life-threatening complications, reducing the number of critically ill patients listed as United Network for Organ Sharing (UNOS) status 2A at the time of OLT. We compared the ability of the MELD and CTP scores to predict pre-OLT disease severity, as well as outcome and resource utilization post-OLT. Data from 42 consecutive UNOS status 2A patients undergoing OLT at a single center were used to calculate MELD and CTP scores at the time of status 2A listing. Multivariate analysis was used to determine the relationship between these scores and pre-OLT disease severity measures, survival post-OLT, and measures of resource use post-OLT. The MELD was superior to CTP score in predicting pre-OLT requirements for mechanical ventilation and dialysis. Neither score correlated with the resource utilization parameters studied. Only two patients died within 3 months post-OLT; neither score was predictive of survival in this cohort. In summary, the MELD is superior to CTP score in estimating pre-OLT disease severity in UNOS status 2A patients and thus may help risk stratify status 2A or decompensated status 2B OLT candidates and optimize the timing of OLT. However, neither score correlated with resource use post-OLT in the strata of critically ill patients.