Is LiFe worth living? It all depends on the liver

Abstract

Regardless of the initial cause, critical illness almost invariably involves serious derangement of function across multiple organs and body systems. While much attention has rightly been directed towards the development of predictive models which seek to measure illness severity and forecast outcome in severe multiple organ failure [1], severe respiratory failure [2] and renal injury [3], less work has been undertaken to elucidate the specific impact of acute hepatic dysfunction in the context of chronic liver disease-despite recognition that liver injury in critically ill patients is associated with poor outcome [4]. The complex care needs and high mortality of patients with severe acute liver failure is well-described [5], and approaches for predicting outcomes for patients with chronic liver disease [6], decompensated cirrhosis [7] and cirrhotic patients in the intensive care unit (ICU) [8] are established. Regardless of these advances, however, the importance of evolving hepatic dysfunction as part of an overall non-liver specific critical illness may still be underappreciated [9], even in patients with known chronic liver problems. In their work to develop a laboratory-based liver injury failure evaluation (LiFe) score, Edmark et al. [10] outline an interesting approach to the development, validation and potential application of a simple tool that may assist intensivists in the evaluation and management of patients with known chronic liver disease admitted to the ICU.In developing the LiFe score, Edmark and colleagues first conducted an online survey of European Society of Intensive Care Medicine members and received over 150 responses, mainly from European clinicians. Over onethird of respondents indicated that they worked in academic centers with specific hepatobiliary expertise. From the survey results, the three most highly ranked markers of liver injury were identified: the international normalised ratio (INR), total bilirubin and arterial lactate-considered to be representative of liver synthetic capacity, excretory function and metabolic properties, respectively. A research registry holding records from two large academic medical centres in Boston was then accessed to obtain de-identified records of patients admitted to the ICU during an 18-year period ending in 2007. Over 90,000 records were evaluated, of which more than 85,000 were excluded from the analysis because the patients did not have chronic liver disease and more than 6000 were excluded because laboratory test results for the three aforementioned parameters were not available. The Boston-based derivation cohort was therefore ultimately based on 945 patients. Records from a major liver transplant centre in London were then accessed to obtain the validation cohort of 971 patients. A clinical prediction tool was then created using a logistic regression model describing the risk of 30-day mortality as a function of lactate, INR and total bilirubin data collected from the derivation cohort at admission to ICU. Further statistical refinement an...