Prognostic impact of ICG-PDR in patients with hypoxic hepatitis

[Liver diseases in the intensive care unit]

The frequency of liver diseases in the intensive care unit has increased significantly in recent years and is now observed in up to 20% of critically ill patients. The occurrence of liver disease is associated with significantly increased morbidity and mortality. Two groups of liver diseases in the intensive care unit can be distinguished. First, the group of "primary hepatic dysfunctions", which includes primary acute liver failure as well as acute-on-chronic liver failure in patients with pre-existing liver cirrhosis. The second group of "secondary or acquired liver diseases" includes cholestatic liver diseases, as well as hypoxic liver injury and mixed forms, as well as other rarer liver diseases. Due to the diversity of liver diseases and the very different triggers, sufficient knowledge of the underlying changes (including hemodynamic changes, inflammatory states or drug-related) is essential. Early recognition, diagnosis, and treatment of the underlying disease are essential for all liver dysfunction in critically ill patients in the intensive care unit. This review article aims to take a closer look at liver diseases in the intensive care unit and provides insight into diagnostics and treatment options.

Acute liver failure after out-of-hospital cardiac arrest: An observational study

RATIONALE

Apart from hypoxic hepatitis (HH), the hepatic consequences of out-of-hospital cardiac arrest (OHCA) have been little studied. This cohort study aimed to investigate the characteristics of liver dysfunction resulting from OHCA and its association with outcomes.

METHODS

Among the conventional static liver function tests used to define acute liver failure (ALF), we determined which one correlated more closely with the reference indocyanine green (ICG) clearance test in a series of OHCA patients from the CYRUS trial (NCT01595958). Subsequently, we assessed whether ALF, in addition to HH (i.e., acute liver injury), was an independent risk factor for death in a large cohort of OHCA patients admitted to two intensive care units between 2007 and 2017.

RESULTS

ICG clearance, available for 22 patients, was impaired in 17 (77.3%) cases. Prothrombin time (PT) ratio was the only static liver function test that correlated significantly (r = -0.66, p < 0.01) with ICG clearance and was therefore used to define ALF, with the usual cutoff of < 50%. Of the 418 patients included in the analysis (sex ratio: 1.4; median age: 64 [53-75] years; non-shockable rhythm: 73%), 67 (16.0%) presented with ALF, and 61 (14.6%) had HH at admission. On day 28, 337 (80.6%) patients died. Following multivariate analysis, ALF at admission, OHCA occurring at home, absence of bystander, non-cardiac cause of OHCA, low-flow duration ≥ 20 min, and SOFA score excluding liver subscore at admission were independently associated with day 28 mortality.

CONCLUSIONS

ALF occurred frequently after OHCA and, unlike HH, was independently associated with day 28 mortality.

[Analysis of indocyanine green plasma disappearance rate in clinical practice]

OBJECTIVE

To justify the optimal method for determining indocyanine green plasma disappearance rate (PDRICG).

MATERIAL AND METHODS

We analyzed PDRICG in intensive care units. Indocyanine green was administered intravenously at a dose of 0.25 mg/kg. PDRICG was analyzed simultaneously by using of three methods: 1) PDD (PiCCO2 LiMON device), 2) SBS with analysis of plasma samples on precise spectrophotometer, 3) SBS with analysis of plasma samples on simple experimental photometer.

RESULTS

PDD method was used for 346 PDRICG tests in 256 patients. Of these, 14.3% of measurements were erroneous. Paired tests using PDD and SBS methods were performed in 299 cases. SBS method resulted erroneous data in 0.6% of cases. Certain correlation (r=0.79, p<0.001) was found between the reference method (SBS with spectrophotometry) and the PDD method. Bland-Altman plot for these two methods showed that proportional bias of mean difference was caused by extremely high PDRICG of the PDD method (for example, more than 30%/min). Comparison of two SBS variants (spectrophotometer and experimental photometer) revealed good correlation (r=0.91, p<0.001).

CONCLUSION

SBS method for measuring PDRICG ensures accurate results under mechanical interferences in patients with impaired capillary blood flow. This eliminates the need for redo measurement. Duplication of the PDD and SBS methods is recommended when repeating the test is not possible (organ donors).

Prediction of 30-day mortality in heart failure patients with hypoxic hepatitis: Development and external validation of an interpretable machine learning model

Background

This study aimed to explore the impact of hypoxic hepatitis (HH) on survival in heart failure (HF) patients and to develop an effective machine learning model to predict 30-day mortality risk in HF patients with HH.

Methods

In the Medical Information Mart for Intensive Care (MIMIC)-III and IV databases, clinical data and survival situations of HF patients admitted to the intensive care unit (ICU) were retrospectively collected. Propensity Score Matching (PSM) analysis was used to balance baseline differences between HF patients with and without HH. Kaplan Meier analysis and multivariate Cox analysis were used to determining the effect of HH on the survival of CF patients. For developing a model that can predict 30-day mortality in CF patients with HH, the feature recurrence elimination (RFE) method was applied to feature selection, and seven machine learning algorithms were employed to model construction. After training and hyper-parameter optimization (HPO) of the model through cross-validation in the training set, a performance comparison was performed through internal and external validation. To interpret the optimal model, Shapley Additive Explanations (SHAP) were used along with the Local Interpretable Model-agnostic Explanations (LIME) and the Partial Dependence Plot (PDP) techniques.

Results

The incidence of HH was 6.5% in HF patients in the MIMIC cohort. HF patients with HH had a 30-day mortality rate of 33% and a 1-year mortality rate of 51%, and HH was an independent risk factor for increased short-term and long-term mortality risk in HF patients. After RFE, 21 key features (21/56) were selected to build the model. Internal validation and external validation suggested that Categorical Boosting (Catboost) had a higher discriminatory capability than the other models (internal validation: AUC, 0.832; 95% CI, 0.819–0.845; external validation: AUC, 0.757 95% CI, 0.739–0.776), and the simplified Catboost model (S-Catboost) also had good performance in both internal validation and external validation (internal validation: AUC, 0.801; 95% CI, 0.787–0.813; external validation: AUC, 0.729, 95% CI, 0.711–0.745).

Conclusion

HH was associated with increased mortality in HF patients. Machine learning methods had good performance in identifying the 30-day mortality risk of HF with HH. With interpretability techniques, the transparency of machine learning models has been enhanced to facilitate user understanding of the prediction results.

Critical care hepatology: definitions, incidence, prognosis and role of liver failure in critically ill patients

Organ dysfunction or overt failure is a commonplace event in the critically ill affecting up to 70% of patients during their stay in the ICU. The outcome depends on the resolution of impaired organ function, while a domino-like deterioration of organs other than the primarily affected ones paves the way for increased mortality. “Acute Liver Failure” was defined in the 1970s as a rare and potentially reversible severe liver injury in the absence of prior liver disease with hepatic encephalopathy occurring within 8 weeks. Dysfunction of the liver in general reflects a critical event in “Multiple Organ Dysfunction Syndrome” due to immunologic, regulatory and metabolic functions of liver parenchymal and non-parenchymal cells. Dysregulation of the inflammatory response, persistent microcirculatory (hypoxic) impairment or drug-induced liver injury are leading problems that result in “secondary liver failure,” i.e., acquired liver injury without underlying liver disease or deterioration of preexisting (chronic) liver disease (“Acute-on-Chronic Liver Failure”). Conventional laboratory markers, such as transaminases or bilirubin, are limited to provide insight into the complex facets of metabolic and immunologic liver dysfunction. Furthermore, inhomogeneous definitions of these entities lead to widely ranging estimates of incidence. In the present work, we review the different definitions to improve the understanding of liver dysfunction as a perpetrator (and therapeutic target) of multiple organ dysfunction syndrome in critical care.

Graphic Abstract

[Hepatic dysfunction in sepsis]

Sepsis represents a life-threatening condition that frequently accompanies acute hepatic dysfunction. As a result of systemic inflammation, immune dysregulation, and microcirculatory derangements, different types of liver dysfunction can occur, such as hypoxic hepatitis, sepsis-associated cholestasis, or liver failure. A very serious and late sequela is secondary sclerosing cholangitis of the critically ill patient. Clinical management of sepsis-related liver dysfunction includes the rapid identification and treatment of the suspected underlying infection, hemodynamic stabilization to improve hepatic perfusion, and the optimization of oxygen delivery to the liver. Despite maximum efforts in supportive treatment, the outcome of patients with sepsis or septic shock and concomitant severe hepatic dysfunction remains very poor.

Liver Injury and Failure in Critical Illness

The frequency of acquired liver injury and failure in critical illness has been significantly increasing over recent decades. Currently, liver injury and failure are observed in up to 20% of patients in intensive care units and are associated with significantly increased morbidity and mortality. Secondary forms of liver injury in critical illness are divided primarily into cholestatic, hypoxic, or mixed forms. Therefore, sufficient knowledge of underlying alterations (e.g., hemodynamic, inflammatory, or drug induced) is key to a better understanding of clinical manifestations, prognostic implications, as well as diagnostic and therapeutic options of acquired liver injury and failure. This review provides a structured approach for the evaluation and treatment of acquired liver injury and failure in critically ill patients.

An efficient method for measuring plasma volume using indocyanine green dye

Plasma volume (PV) can be an important marker of health status and may affect the interpretation of plasma biomarkers, but is rarely measured due to the complexity and time required. Indocyanine green (ICG) is a water-soluble tricarbocyanine dye with a circulatory half-life of 2–3 min, allowing for quick clearance and repeated use. It is used extensively in medical diagnostic tests including ophthalmologic imaging, liver function, and cardiac output, particularly in critical care. ICG has been validated for measuring PV in humans, however previous work has provided minimal published details or has focused on a single aspect of the method. We aimed to develop a detailed, optimal protocol for the use of ICG to measure PV in women of reproductive age. We combined best practices from other studies and optimized the protocol for efficiency.

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This method reduces the time from blood collection to PV determination to ˜2 h and the amount of plasma required to estimate PV to 2.5 mL (1.5 mL before ICG injection and 1.0 mL post-injection).

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Participant inconvenience is reduced by inserting an intravenous (IV) catheter in only one arm, not both arms.

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Five post-injection plasma samples (2–5 min after ICG bolus) are enough to accurately develop the decay curve for plasma ICG concentration and estimate PV by extrapolation.

Hypoxic liver injury after in- and out-of-hospital cardiac arrest: Risk factors and neurological outcome

BACKGROUND

Hypoxic liver injury (HLI) is a frequent and life-threatening complication in critically ill patients that occurs in up to ten percent of critically ill patients. However, there is a lack of data on HLI following cardiac arrest and its clinical implications on outcome. Aim of this study was to investigate incidence, outcome and functional outcome of patients with HLI after in-hospital cardiac arrest (IHCA) and out-of-hospital cardiac arrest (OHCA).

METHODS

We conducted an analysis of a cardiac arrest registry data over a 7-year period. All patients with non-traumatic OHCA and IHCA with return of spontaneous circulation (ROSC) treated at the emergency department of a tertiary care hospital were included in the study. HLI was defined according to established criteria. Predictors of HLI, occurrence, clinical and neurological outcome were assessed using multivariable regression.

RESULTS

Out of 1068 patients after IHCA and OHCA with ROSC, 219 (21%) patients developed HLI. Rate of HLI did not differ significantly in IHCA and OHCA patients. Multivariate regression analysis identified time-to-ROSC [OR 1.18, 95% CI (1.01-1.38); p < 0.05], presence of cardiac failure [OR 2.57, 95% CI (1.65-4.01); p < 0.001] and Charlson comorbidity index [OR 0.83, 95% CI (0.72-0.95); p < 0.01] as independent predictors for occurrence of HLI. Good functional outcome was significantly lower in patients suffering from HLI after 28-days (35% vs. 48%, p < 0.001) and 1-year (34% vs. 44%, p < 0.001). Occurrence of HLI was associated with unfavourable neurological outcome [OR 1.74, 95% CI (1.16-2.61); p < 0.01] in multivariate regression analysis.

CONCLUSION

New onset of HLI is a frequent finding after IHCA and OHCA. HLI is associated with increased mortality, unfavourable neurological and overall outcome.

ICG Clearance Test and 99mTc-GSA SPECT/CT Fusion Images

Preoperative estimation of future remnant liver function is critical for major hepatic surgery to avoid postoperative morbidity and mortality. Among several liver function tests, the indocyanine green (ICG) clearance test is still the most popular dynamic method. The usefulness of ICG clearance test parameters, such as ICGR15, KICG, or PDRICG, has been reported by many investigators. The transcutaneous non-invasive pulse dye densitometry system has made the ICG clearance test more convenient and attractive, even in Western countries. The concept of future remnant KICG (rem KICG), which combines the functional aspect and the volumetric factor of the future remnant liver, seems ideal for determining the maximum extent of major hepatic resection that will not cause postoperative liver failure. For damaged livers with functional heterogeneity among the hepatic segments, fusion images combining technetium-99m-diethylenetriaminepentaacetic acid-galactosyl human serum albumin single photon emission computed tomography (99mTc-GSA SPECT) and X-ray CT are helpful to precisely estimate the functional reserve of the future remnant liver. Another technique for image-based liver function estimation, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid(Gd-EOB)-enhanced magnetic resonance imaging, may be an ideal candidate for the preoperative determination of future remnant liver function. Using these methods effectively, morbidity and mortality after major hepatic resection could be reduced.

Cholestatic Alterations in the Critically Ill: Some New Light on an Old Problem

Liver dysfunction and jaundice are traditionally viewed as late features of sepsis and other critical illnesses and are associated with a complicated ICU stay. However, study results suggest that cholestatic alterations occur early in the course of critical illnesses, perceived only as minor abnormalities in routinely used biochemical liver tests. Inflammation-induced alterations in the transport of bile acids (BAs) appear to drive BAs and bilirubin toward the systemic circulation. Ongoing BA synthesis with an, at least partial, loss of feedback inhibition further contributes to elevated circulating BAs and bilirubin. To what extent these changes reflect a biochemical epiphenomenon, true illness-induced liver dysfunction, or a beneficial and adaptive response to illness should be investigated further. Because of the lack of specificity of standard laboratory tests, especially in the context of a complex systemic condition such as critical illness, identifying true cholestatic liver dysfunction remains a great challenge. However, high levels of cholestatic markers that are sustained in patients with prolonged critical illness almost always indicate a complicated illness course and should be monitored closely. Preventing cholestatic liver dysfunction comprises minimizing inflammation and hypoxia in the liver and preventing hyperglycemia, avoiding early use of parenteral nutrition, and reducing the administration of avoidable drugs. Future research on the effects of BAs and on modulating underlying drivers of cholestasis induced by critical illness is warranted as this could open perspectives for a targeted diagnostic approach and ultimately for novel therapies to improve outcome.

Current concepts in ischemic hepatitis

PURPOSE OF REVIEW

The current review seeks to define ischemic hepatitis and its associated comorbidities. It means to review the pathophysiology, clinical presentation, clinical course, outcomes, and any potential therapies.

RECENT FINDINGS

Ischemic hepatitis has long been associated with cardiovascular disease; recent reports have found a substantial link between preexisting cardiovascular disease and the risk for developing ischemic hepatitis. A proposed mechanism by which hepatic congestion predisposes the liver to hemodynamic injury further defines this link. Treatment is aimed at the underlying hemodynamic disturbance; however, efforts to better predict mortality and improve outcomes continue to arise. The Acute Liver Failure Study Group proposed that, though uncommon, ischemic hepatitis may result in acute liver failure. With numerous studies identifying the multiple comorbid conditions associated with ischemic hepatitis, the sequela of acute liver failure is called into question.

SUMMARY

Ischemic hepatitis is a clinical syndrome frequently encountered in critically ill patients that represents a complication of underlying cardiac, circulatory, or respiratory failure. The pathogenesis of ischemic hepatitis appears to occur as a result of a 'two-hit' mechanism when the liver, which is at risk, is subsequently exposed to systemic hypoperfusion and ischemia, ultimately resulting in a marked but transient elevation in aspartate aminotransferase and alanine aminotransferase. Mortality is high and is dependent largely on the underlying cause of hypotension. Treatment is directed at the underlying cause of hemodynamic disturbance.

Hypoxic Hepatitis: A Review and Clinical Update

Hypoxic hepatitis (HH), also known as ischemic hepatitis or shock liver, is characterized by a massive, rapid rise in serum aminotransferases resulting from reduced oxygen delivery to the liver. The most common predisposing condition is cardiac failure, followed by circulatory failure as occurs in septic shock and respiratory failure. HH does, however, occur in the absence of a documented hypotensive event or shock state in 50% of patients. In intensive care units, the incidence of HH is near 2.5%, but has been reported as high as 10% in some studies. The pathophysiology is multifactorial, but often involves hepatic congestion from right heart failure along with reduced hepatic blood flow, total body hypoxemia, reduced oxygen uptake by hepatocytes or reperfusion injury following ischemia. The diagnosis is primarily clinical, and typically does not require liver biopsy. The definitive treatment of HH involves correction of the underlying disease state, but successful management includes monitoring for the potential complications such as hypoglycemia, hyperglycemia, hyperammonemia and hepatopulmonary syndrome. Prognosis of HH remains poor, especially for cases in which there was a delay in diagnosis. The in-hospital mortality rate is >50%, and the most frequent cause of death is the predisposing condition and not the liver injury itself.