Ammonia and urea metabolism in acute liver failure: A multicentre cohort study.

BACKGROUND & AIMS: Ammonia is metabolized into urea in the liver. In acute liver failure (ALF), ammonia has been associated with survival. However, urea variation has been poorly studied. METHODS: Observational cohort including ALF patients from Curry Cabral Hospital (Lisbon, Portugal) and Clinic Hospital (Barcelona, Spain) between 10/2010 and 01/2023. The United States ALF Study Group cohort was used for external validation. Primary exposures were serum ammonia and urea on ICU admission. Primary endpoint was 30-day transplant-free survival (TFS). Secondary endpoint was explanted liver weight. RESULTS: Among 191 ALF patients, median (IQR) age was 46 (32; 57) years and 85 (44.5%) were males. Overall, 86 (45.0%) patients were transplanted and 75 (39.3%) died. Among all ALF patients, following adjustment for age, sex, body weight, and aetiology, higher ammonia or lower urea was independently associated with higher INR on ICU admission (p < .009). Among all ALF patients, following adjustment for sex, aetiology, and lactate, higher ammonia was independently associated with lower TFS (adjusted odds ratio (95% confidence interval [CI]) = 0.991 (0.985; 0.997); p = .004). This model predicted TFS with good discrimination (area under receiver operating curve [95% CI] = 0.78 [0.75; 0.82]) and reasonable calibration (R2 of 0.43 and Brier score of 0.20) after external validation. Among transplanted patients, following adjustment for age, sex, actual body weight, and aetiology, higher ammonia (p = .024) or lower (p < .001) urea was independently associated with lower explanted liver weight. CONCLUSIONS: Among ALF patients, serum ammonia and urea were associated with ALF severity. A score incorporating serum ammonia predicted TFS reasonably well.

Persistent But Not Transient Acute Kidney Injury Was Associated With Lower Transplant-Free Survival in Patients With Acute Liver Failure: A Multicenter Cohort Study.

OBJECTIVES: Acute liver failure (ALF) is an orphan disease often complicated by acute kidney injury (AKI). We assessed the impact of transient versus persistent AKI on survival in patients with ALF. DESIGN: International multicenter retrospective cohort. SETTING: U.S. ALF Study Group prospective registry. PATIENTS: Patients with greater than or equal to 18 years and ALF in the registry from 1998 to 2016 were included. Patients with less than 3 days of follow-up, without kidney function evaluation on day 3, or with cirrhosis were excluded. INTERVENTIONS: AKI was defined by Kidney Disease Improving Global Outcomes guidelines on day 1. Kidney recovery was defined on day 3 as transient AKI, by a return to no-AKI within 48 hours or persistent AKI if no such recovery or renal replacement therapy (RRT) was observed. Primary outcome was transplant-free survival (TFS) at 21 days. MEASUREMENTS AND MAIN RESULTS: Among 1,071 patients with ALF, 339 (31.7%) were males, and median (interquartile range) age was 39 years (29-51 yr). Acetaminophen-related ALF was found in 497 patients (46.4%). On day 1, 485 of 1,071 patients (45.3%) had grade 3-4 hepatic encephalopathy (HE), 500 of 1,070 (46.7%) required invasive mechanical ventilation (IMV), 197 of 1,070 (18.4%) were on vasopressors, and 221 of 1,071 (20.6%) received RRT. On day 1, 673 of 1,071 patients (62.8%) had AKI. On day 3, 72 of 1,071 patients (6.7%) had transient AKI, 601 of 1,071 (56.1%) had persistent AKI, 71 of 1,071 (6.6%) had late onset AKI, and 327 of 1,071 (30.5%) remained without AKI. Following adjustment for confounders (age, sex, race, etiology, HE grade, use of IMV and vasopressors, international normalized ratio, and year), although persistent acute kidney injury (adjusted odds ratio [aOR] [95% CI] 0.62 [0.44-0.88]) or late onset AKI (aOR [95% CI] 0.48 [0.26-0.89]) was associated with lower TFS, transient AKI was not (aOR [95% CI] 1.89 [0.99-3.64]). CONCLUSIONS: In a multicenter cohort of patients with ALF, persistent but not transient AKI was independently associated with lower short-term TFS.

Liver trauma in the intensive care unit.

PURPOSE OF REVIEW: To review the surgical and critical care management of liver trauma; one of the most common abdominal injuries sustained due to its size and location. RECENT FINDINGS: Hepatic injuries range from negligible to life threatening: in the acute phase, the most common cause of morbidity and mortality is hemorrhage; however, severe traumatic hepatic injuries can also lead to biochemical abnormalities, altered coagulation, and ultimately liver failure. This brief review will review the classification of traumatic liver injuries by mechanism, grade, and severity. Most Grades I-III injuries can be managed nonoperatively, whereas the majority of Grades IV-VI injuries require operative management. Therapeutic strategies for traumatic liver injury including nonoperative, operative, radiologic will be described. The primary goal of liver trauma management in the acute setting is hemorrhage control, then the management of secondary factors such as bile leaks. The rapid restoration of homeostasis may prevent further damage to the liver and allow for deferred nonoperative management, which has been shown to be associated with good clinical outcomes. SUMMARY: A multidisciplinary approach to the care of these patients at an experienced liver surgery center is warranted.

Significant lung injury and its prognostic significance in acute liver failure: A cohort analysis.

BACKGROUND AND AIMS: Respiratory failure complicating acute liver failure (ALF) may preclude liver transplantation (LT). We evaluated the association between significant lung injury (SLI) and important clinical outcomes. METHODS: Retrospective cohort study of 947 ALF patients with chest radiograph (CXR) and arterial blood gas (ABG) data enrolled in the US Acute Liver Failure Study Group (US-ALFSG) from January 1998 to December 2016. SLI was defined by moderate hypoxaemia (Berlin classification; PaO2 /FiO2  < 200 mm Hg) and abnormalities on CXR. Primary outcomes were 21-day transplant-free survival (TFS) and overall survival. RESULTS: Of 947 ALF patients, 370 (39%) had evidence of SLI. ALF patients with SLI (ALF-SLI) had significantly worse oxygenation than controls on admission (median PF ratio 120 vs 300 mm Hg, P < .0001) and higher lactate (6.1 vs 4.6 mmol/l, P = .0008). ALF-SLI patients had higher rates of tracheal (19% vs 14%) and bloodstream (17% vs 11%, P < .005 for both) infections and were more likely to receive transfusions (red cells 55% vs 43%; FFP 74% vs 66%; P < .009 for both). ALF-SLI patients were less likely to receive LT (18% vs 25%, P = .02) and had significantly decreased 21-day TFS (34% vs 42%) and overall survival (49% vs 64%, P < .007 for both). After adjusting for significant covariates (INR, bilirubin, acetaminophen aetiology), the development of SLI was independently associated with decreased 21-day TFS (OR 0.71, P = .03) in ALF patients (C-index 0.78). The incorporation of SLI improved discriminatory ability of the King's College Criteria (P = .0061) but not the ALFSG prognostic index (P = .34). CONCLUSION: Significant lung injury is a common complication in ALF patients that adversely affects patient outcomes.

Continuous renal replacement therapy is associated with reduced serum ammonia levels and mortality in acute liver failure.

Hyperammonemia has been associated with intracranial hypertension and mortality in patients with acute liver failure (ALF). We evaluated the effect of renal replacement therapy (RRT) on serum ammonia level and outcomes in ALF. This was a multicenter cohort study of consecutive ALF patients from the United States ALF Study Group registry between January 1998 and December 2016. First, we studied the association of ammonia with hepatic encephalopathy (HE) and 21-day transplant-free survival (TFS; n = 1,186). Second, we studied the effect of RRT on ammonia for the first 3 days post study admission (n = 340) and on 21-day TFS (n = 1,186). Higher admission (n = 1,186) median ammonia level was associated with grade 3-4 HE (116 vs. 83 µmol/L) and mortality at day 21 attributed to neurological (181 vs. 90 µmol/L) and all causes (114 vs. 83 µmol/L; P < 0.001 for all). Among 340 patients with serial ammonia levels, 61 (18%) were on continuous RRT (CRRT), 59 (17%) were on intermittent RRT (IRRT), and 220 (65%) received no RRT for the first 2 days. From days 1 to 3, median ammonia decreased by 38%, 23%, and 19% with CRRT, IRRT, and no RRT, respectively. Comparing to no RRT use, whereas ammonia reduction with CRRT was significant (P = 0.007), with IRRT it was not (P = 0.75). After adjusting for year of enrollment, age, etiology, and disease severity, whereas CRRT (odds ratio [OR], 0.47 [95% confidence interval {CI}, 0.26-0.82]) was associated with reduction in 21-day transplant-free all-cause mortality, IRRT (OR, 1.68 [95% CI, 1.04-2.72]) was associated with an increase. Conclusion: In a large cohort of ALF patients, hyperammonemia was associated with high-grade HE and worse 21-day TFS. CRRT was associated with a reduction in serum ammonia level and improvement of 21-day TFS. (Hepatology 2018;67:711-720).

Lactate and number of organ failures predict intensive care unit mortality in patients with acute-on-chronic liver failure.

BACKGROUND AND AIMS: Patients with acute-on-chronic liver failure (ACLF) have high mortality rates. Most prognostic scores were not developed for the intensive care unit (ICU) setting. We aimed to improve risk stratification for patients with ACLF in the ICU. METHODS: A training set with 240 patients with cirrhosis and organ failures (Chronic Liver Failure Sequential Organ Failure Assessment score [CLIF-SOFA]) from Curry Cabral Hospital (Portugal) and University of Alberta Hospital (Canada) in 2010-2016 was used to derive a prognostic model for ICU mortality. A validation set with 237 patients with cirrhosis and organ failures from Vancouver General Hospital (Canada) in 2000-2011 was used to evaluate its performance. RESULTS: Amongst patients in the training set, ICU and hospital mortality rates were 39.2% and 54.6% respectively. Median lactate (4.4 vs 2.5 mmol/L) and number of organ failures (3 vs 2) on admission to ICU were associated with higher likelihood of ICU mortality (P < 0.001 for both). The lactate and organ failures predictive model (LacOF) was derived to predict ICU mortality: -2.420 + 0.072 × lactate + 0.569 × number of organ failures (area under-the-curve [AUC], 0.76). In the validation set, the LacOF model discriminative ability (AUC, 0.85) outperformed the CLIF-SOFA (AUC, 0.79), Chronic Liver Failure Consortium Acute-on-Chronic Liver Failure (AUC, 0.73), Model for End-stage Liver Disease score (AUC, 0.78) and Acute Physiology and Chronic Health Evaluation II scores (AUC, 0.74; P < 0.05 for all). The LacOF model calibration was good up to the 25% likelihood of ICU mortality. CONCLUSIONS: In patients with ACLF, lactate and number of organ failures on admission to ICU are useful to predict ICU mortality. This early prognostic evaluation may help to better stratify the risk of ICU mortality and thus optimize organ support strategies.

Respiratory Complications Before and After Liver Transplant.

Respiratory complications before and after liver transplant are common, diverse, and potentially have a negative impact on patient outcomes. In this review, we discuss the most frequent respiratory conditions that patients may develop in the perioperative period. Their prevention and/or treatment may help to maximize the benefit these patients may derive from liver transplant. This review examines diagnostic and therapeutic approaches to these complications for hepatologists, surgeons, and critical care physicians.

HBV-Associated Acute Liver Failure After Immunosuppression and Risk of Death.

BACKGROUND & AIMS: Acute liver failure (ALF) caused by hepatitis B virus (HBV) infection can occur after immunosuppressive treatment and be fatal, although it might be preventable. We aimed to characterize the causes, clinical course, and short-term outcomes of HBV-associated ALF after immune-suppressive therapy, compared with patients with HBV-associated ALF without immunosuppression (control subjects). METHODS: We performed a retrospective multicenter study of 156 consecutive patients diagnosed with HBV-associated ALF (22 with a solid or blood malignancy) enrolled in the Acute Liver Failure Study Group registry from January 1998 through April 2015. We collected data on results of serologic and hepatic biochemistry analyses, grade of hepatic encephalopathy, Model for End-Stage Liver Disease score, and King's College criteria. We also collected data on clinical features, medical therapies, and complications in the first 7 days following study enrollment. Logistic regression was used to identify factors associated with transplant-free survival at 21 days in HBV-associated ALF (the primary outcome). RESULTS: Among patients with HBV-associated ALF, 28 cases (18%) occurred after immunosuppressive therapy (15 patients received systemic corticosteroids and 21 received chemotherapy); and 128 cases did not (control subjects, 82%). Significantly greater proportions of patients with HBV-associated ALF after immunosuppression were nonwhite persons, and had anemia or thrombocytopenia than controls (P < .02 for all). The serologic profile of HBV infection, severity of liver failure (based on MELD score), and complications (hepatic encephalopathy or need for mechanical ventilation, vasopressors, or renal replacement therapy) were similar between the groups (P > .17 for all). Factors associated with 21 day transplant-free survival were increased MELD score (odds ratio ∼OR, 0.894 (95% confidence interval 0.842-0.949 per increment), requirement for mechanical ventilation (OR 0.111(0.041-0.300), and immunosuppressive therapy (OR 0.274(0.082-0.923)). CONCLUSIONS: Within a cohort study of patients with HBV-associated ALF, 18% had received immunosuppressive therapy. Significantly smaller proportions of patients with HBV-associated ALF after immunosuppression survive beyond 21 days than patients with HBV-associated ALF who did not receive immunosuppression. Patients undergoing chemotherapy should be screened for HBV infection and given appropriate antiviral therapies to reduce preventable mortality.

Clinical Impact of Portal Vein Thrombosis Prior to Liver Transplantation: A Retrospective Cohort Study.

INTRODUCTION: To identify the impact of portal vein thrombosis (PVT) and associated medical and surgical factors on outcomes post liver transplant (LT). MATERIAL AND METHODS: Two analyses were performed. Analysis One: cohort study of 505 consecutive patients who underwent LT (Alberta) between 01/2002-12/2012. PVT was identified in 61 (14%) patients. Analysis Two: cohort study of 144 consecutive PVT patients from two sites (Alberta and London) during the same period. Cox multivariable survival analysis was used to identify independent associations with post-LT mortality. RESULTS: In Analysis One (Alberta), PVT was not associated with post-LT mortality (log rank p = 0.99). On adjusted analysis, complete/occlusive PVT was associated with increased mortality (Hazard Ratio (HR) 8.4, p &lt; 0.001). In Analysis Two (Alberta and London), complete/occlusive PVT was associated with increased mortality only on unadjusted analysis (HR 3.7, p = 0.02). On adjusted analysis, Hepatitis C (HR 2.1, p = 0.03) and post-LT portal vein re-occlusion (HR 3.2, p = 0.01) were independently associated with increased mortality. CONCLUSION: Well-selected LT patients who had PVT prior to LT had similar post-LT outcomes to non-PVT LT recipients. Subgroups of PVT patients who did worse post-LT (complete/occlusive thrombosis pre-LT, Hepatitis C or post-LT portal vein re-occlusion) warrant closer evaluation in listing and management post-LT.

Comorbidities have a limited impact on post-transplant survival in carefully selected cirrhotic patients: a population-based cohort study.

BACKGROUND: Improving estimation of long-term survival of patients with end-stage liver disease after orthotopic liver transplantation (OLT) would optimize decisions on eligibility for transplant. We aimed to externally validate previously derived Charlson Comorbity Index for OLT (CCI-OLT); subsequently, we developed a new model to predict 5-year mortality after transplant. MATERIAL AND METHODS: This single center retrospective cohort study included 524 consecutive adult cirrhotic patients who underwent OLT in 2002-2012. External validation of CCI-OLT used Kaplan-Meier method. Derivation of the new predictive model used Cox proportional hazards regression. RESULTS: One-, 3-, and 5-year cumulative survival after OLT was 89%, 80%, and 73%, respectively. CCI-OLT was not associated with 5-year mortality after transplant (P = 0.34). We derived and internally validated a new predictive model of 5-year mortality after OLT based on six pre-transplant characteristics of patients: age, body mass index, hepatitis C, hepatic encephalopathy, intensive care unit stay at transplant, and live donor (C-index = 0.64). We further developed a nomogram to estimate individual probability of 1-, 3-, and 5-year survival after OLT. CONCLUSIONS: In our cohort, CCI-OLT was not associated with survival following transplant. The new predictive model discriminative capacity was only modest, suggesting that pre-transplant characteristics are of limited value in predicting post-transplant outcomes in thoroughly selected patients.

Incidence and outcomes of acute kidney injury following orthotopic lung transplantation: a population-based cohort study.

BACKGROUND: Acute kidney injury (AKI) is a serious complication following lung transplantation (LTx). We aimed to describe the incidence and outcomes associated with AKI following LTx. METHODS: A retrospective population-based cohort study of all adult recipients of LTx at the University of Alberta between 1990 and 2011. The primary outcome was AKI, defined and classified according to the Kidney Disease: Improving Global Outcomes (KDIGO) criteria, in the first 7 post-operative days. Secondary outcomes included risk factors, utilization of renal replacement therapy (RRT), occurrence of post-operative complications, mortality and kidney recovery. RESULTS: Of 445 LTx recipients included, AKI occurred in 306 (68.8%), with severity classified as Stage I in 38.9% (n = 173), Stage II in 17.5% (n = 78) and Stage III in 12.4% (n = 55). RRT was received by 36 (8.1%). Factors associated with AKI included longer duration of cardiopulmonary bypass [per minute, odds ratio (OR) 1.003; 95% confidence interval (CI), 1.001-1.006; P = 0.02], and mechanical ventilation [per hour (log-transformed), OR 5.30; 95% CI, 3.04-9.24; P < 0.001], and use of cyclosporine (OR 2.03; 95% CI, 1.13-3.64; P = 0.02). In-hospital and 1-year mortality were significantly higher in those with AKI compared with no AKI (7.2 versus 0%; adjusted P = 0.001; 14.4 versus 5.0%; adjusted P = 0.02, respectively). At 3 months, those with AKI had greater sustained loss of kidney function compared with no AKI [estimated glomerular filtration rate, mean (SD): 68.9 (25.7) versus 75.3 (22.1) mL/min/1.73 m(2), P = 0.01]. CONCLUSIONS: By the KDIGO definition, AKI occurred in two-thirds of patients following LTx. AKI portended greater risk of death and loss of kidney function.

What every Intensivist should know about ... Ammonia in liver failure.

PURPOSE: Acute liver failure (ALF) or acute-on-chronic liver failure (ACLF) patients have high short-term mortality and morbidity. In the context of liver failure, increased serum ammonia is associated with worse neurological outcomes, including high-grade hepatic encephalopathy (HE), cerebral edema, and intracranial hypertension. Besides its neurotoxicity, hyperammonemia may contribute to immune dysfunction and the risk of infection, a frequent trigger for multi-organ failure in these patients. MATERIAL AND METHODS: We performed a literature-based narrative review. Publications available in PubMed® up to June 2023 were considered. RESULTS: In the ICU management of liver failure patients, serum ammonia may play an important role. Accordingly, in this review, we focus on recent insights about ammonia metabolism, serum ammonia measurement strategies, hyperammonemia prognostic value, and ammonia-targeted therapeutic strategies. CONCLUSIONS: Serum ammonia may have prognostic value in liver failure. Effective ammonia targeted therapeutic strategies are available, such as laxatives, rifaximin, L-ornithine-l-aspartate, and continuous renal replacement therapy.

Continuous renal replacement therapy and survival in acute liver failure: A systematic review and meta-analysis.

OBJECTIVE: Acute liver failure (ALF) is a rare syndrome leading to significant morbidity and mortality. An important cause of mortality is cerebral edema due to hyperammonemia. Different therapies for hyperammonemia have been assessed including continuous renal replacement therapy (CRRT). We conducted a systematic review and meta-analysis to determine the efficacy of CRRT in ALF patients. MATERIALS AND METHODS: We searched MEDLINE, EMBASE, Cochrane Library, and Web of Science. Inclusion criteria included adult patients admitted to an ICU with ALF. Intervention was the use of CRRT for one or more indications with the comparator being standard care without the use of CRRT. Outcomes of interest were overall survival, transplant-free survival (TFS), mortality and changes in serum ammonia levels. RESULTS: In total, 305 patients underwent CRRT while 1137 patients did not receive CRRT. CRRT was associated with improved overall survival [risk ratio (RR) 0.83, 95% confidence interval (CI) 0.70-0.99, p-value 0.04, I2 = 50%] and improved TFS (RR 0.65, 95% CI 0.49-0.85, p-value 0.002, I2 = 25%). There was a trend towards higher mortality with no CRRT (RR 1.24, 95% CI 0.84-1.81, p-value 0.28, I2 = 37%). Ammonia clearance data was unable to be pooled and was not analyzable. CONCLUSION: Use of CRRT in ALF patients is associated with improved overall and transplant-free survival compared to no CRRT.

Referral for liver transplant following acute variceal bleeding: a multicenter cohort study.

OBJECTIVES: Referral for liver transplant (LT) following acute variceal bleeding (AVB) varies widely. We aimed to characterize and assess its impact on clinical outcomes. METHODS: Observational retrospective cohort including cirrhosis patients with AVB from 3 hospitals in Lisbon, Portugal, from 2018 to 2019. Primary exposure was referral for LT and primary endpoint was all-cause mortality within 2 years of index hospital admission. RESULTS: Among 143 patients, median (IQR) age was 59 (52-72) years and 90 (62.9%) were males. Median (IQR) MELDNa scores on hospital admission and discharge were 15 (11-21) and 13 (10-16), respectively. Overall, 30 (21.0%) patients were assessed for LT, 13 (9.1%) prior to and 17 (11.9%) within 2 years of hospital admission. Overall, 58 (40.6%) patients had at least one potential contra-indication for transplant. LT was performed in 3 (2.1%) patients (among 5 listed). Overall, 34 (23.8%) and 62 (43.4%) patients died at 6 weeks and 2 years post hospital admission, respectively. Following adjustment for confounders, referral for LT was associated with lower 2-year mortality (aHR (95% CI) = 0.20 (0.05-0.85)). CONCLUSION: In a multicenter cohort of cirrhosis patients with AVB, less than a quarter underwent formal LT evaluation. Improved referral for LT following AVB may benefit cirrhosis patients' longer-term mortality.