IntroductionOur aim was to investigate the impact of early versus late initiation of renal replacement therapy (RRT) on clinical outcomes in critically ill patients with acute kidney injury (AKI).MethodsSystematic review and meta-analysis were used in this study. PUBMED, EMBASE, SCOPUS, Web of Science and Cochrane Central Registry of Controlled Clinical Trials, and other sources were searched in July 2010. Eligible studies selected were cohort and randomised trials that assessed timing of initiation of RRT in critically ill adults with AKI.ResultsWe identified 15 unique studies (2 randomised, 4 prospective cohort, 9 retrospective cohort) out of 1,494 citations. The overall methodological quality was low. Early, compared with late therapy, was associated with a significant improvement in 28-day mortality (odds ratio (OR) 0.45; 95% confidence interval (CI), 0.28 to 0.72). There was significant heterogeneity among the 15 pooled studies (I2 = 78%). In subgroup analyses, stratifying by patient population (surgical, n = 8 vs. mixed, n = 7) or study design (prospective, n = 10 vs. retrospective, n = 5), there was no impact on the overall summary estimate for mortality. Meta-regression controlling for illness severity (Acute Physiology And Chronic Health Evaluation II (APACHE II)), baseline creatinine and urea did not impact the overall summary estimate for mortality. Of studies reporting secondary outcomes, five studies (out of seven) reported greater renal recovery, seven (out of eight) studies showed decreased duration of RRT and five (out of six) studies showed decreased ICU length of stay in the early, compared with late, RRT group. Early RRT did not; however, significantly affect the odds of dialysis dependence beyond hospitalization (OR 0.62 0.34 to 1.13, I2 = 69.6%).ConclusionsEarlier institution of RRT in critically ill patients with AKI may have a beneficial impact on survival. However, this conclusion is based on heterogeneous studies of variable quality and only two randomised trials. In the absence of new evidence from suitably-designed randomised trials, a definitive treatment recommendation cannot be made.

Background Acute liver failure (ALF) is a rare syndrome of severe, rapid-onset hepatic dysfunction without prior advanced liver disease that is associated with high morbidity and mortality. Intensive care and liver transplantation provide support and rescue, respectively. Objective To determine whether changes in causes, disease severity, treatment, or 21-day outcomes have occurred in recent years among adult patients with ALF referred to U.S. tertiary care centers. Design Prospective observational cohort study. (ClinicalTrials.gov: NCT00518440) Setting 31 liver disease and transplant centers in the United States. Patients Consecutively enrolled patients–without prior advanced liver disease–with ALF (n = 2070). Measurements Clinical features, treatment, and 21-day outcomes were compared over time annually for trends and were also stratified into two 8-year periods (1998 to 2005 and 2006 to 2013). Results Overall clinical characteristics, disease severity, and distribution of causes remained similar throughout the study period. The 21-day survival rates increased between the two 8-year periods (overall, 67.1% vs. 75.3%; transplant-free survival [TFS], 45.1% vs. 56.2%; posttransplantation survival, 88.3% vs. 96.3% [P < 0.010 for each]). Reductions in red blood cell infusions (44.3% vs. 27.6%), plasma infusions (65.2% vs. 47.1%), mechanical ventilation (65.7% vs. 56.1%), and vasopressors (34.9% vs. 27.8%) were observed, as well as increased use of N-acetylcysteine (48.9% vs. 69.3% overall; 15.8% vs. 49.4% [P < 0.001] in patients with ALF not due to acetaminophen toxicity). When examined longitudinally, overall survival and TFS increased throughout the 16-year period. Limitations The duration of enrollment, the number of patients enrolled, and possibly the approaches to care varied among participating sites. The results may not be generalizable beyond such specialized centers. Conclusion Although characteristics and severity of ALF changed little over 16 years, overall survival and TFS improved significantly. The effects of specific changes in intensive care practice on survival warrant further study. Primary Funding Source National Institutes of Health.

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High circulating ammonia concentrations are common in patients with acute liver failure (ALF) and are associated with hepatic encephalopathy (HE) and intracranial hypertension (ICH). Other risk factors are poorly characterized. We evaluated the relation of the admission arterial ammonia concentration and other clinical variables with the development of HE and ICH. Arterial ammonia was measured on admission to the intensive care unit in 257 patients; 165 had ALF and severe HE, and there were 3 control groups: acute hepatic dysfunction without severe HE (n ‫؍‬ 50), chronic liver disease (n ‫؍‬ 33), and elective surgery (n ‫؍‬ 9). Variables associated with ICH and HE were investigated with regression analysis. Ammonia was higher in ALF patients than controls. An independent risk factor for the development of severe HE and ICH, a level greater than 100 mol/L predicted the onset of severe HE with 70% accuracy. The model for end-stage liver disease (MELD) score was also independently predictive of HE, and its combination with ammonia increased specificity and accuracy. ICH developed in 55% of ALF patients with a level greater than 200 mol/L, although this threshold failed to identify most cases. After admission, ammonia levels remained high in those developing ICH and fell in those who did not. Youth, a requirement for vasopressors, and renal replacement therapy were additional independent risk factors. Conclusion: Ammonia is an independent risk factor for the development of both HE and ICH. Additional MELD scoring improved the prediction of HE. T here is now strong evidence of a central role for ammonia in the pathogenesis of hepatic encephalopathy (HE) that defines acute liver failure (ALF) and the cerebral edema (CE) and intracranial hypertension (ICH) that contribute to the high mortality seen in this condition. Elevations in the circulating ammonia concentration are a frequent finding in experimental and human ALF and appear to be closely related to these complications. 1-3 Experimental studies have demonstrated ammonia-induced changes in neurotransmitter synthesis and release, neuronal oxidative stress, impaired mitochondrial function, and osmotic disturbances resulting from astrocytic metabolism of ammonia to glutamine. [4][5][6] The net result of these changes is a marked alteration in cerebral function and astrocytic swelling. [5][6][7] Recent studies reporting circulating ammonia concentrations in patients with ALF have found levels higher than those seen in patients with HE accompanying chronic liver disease (CLD). 2,3,8,9 The magnitude of the elevation of ammonia, particularly if it is above 150 mol/L, has been reported to be related to an increased risk of major cerebral complications, including reduced consciousness level, seizures, cerebral herniation (CH), and death. 2,3,8,10,11 If confirmed, these findings have the potential to alter clinical practice; patients identified as being at high risk for HE and ICH in this way could be targeted with specific therapies to reduce the circulating ammonia concen-

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