PROSPECTIVE ASSESSMENT OF HEPATIC FUNCTION AND MECHANISMS OF DYSFUNCTION IN THE CRITICALLY ILL

[Indocyanine green in liver tumor resection]

Primary liver cancer and colorectal cancer liver metastases are among the leading causes of cancer-related mortality worldwide. Surgery is one of the main methods of treatment to achieve the best results in overall and recurrence-free survival. The main objectives in this surgery are preoperative planning, assessment of functional viability of liver parenchyma and total resection with low complication rate. Post-resection liver failure is one of the most formidable and often fatal complication following functional failure of liver remnant. Thus, preoperative assessment of liver functional reserves is a necessary step for adequate selection of patients and safe surgery. Passive liver tests, such as biochemical parameters or clinical scales, do not accurately reflect the actual functional component of liver parenchyma. The most accurate method is dynamic quantitative test of liver, such as indocyanine green clearance. The authors discuss the practical aspects of preoperative assessment of liver functional reserves using indocyanine green, as well as the concept and technical foundations of fluorescent imaging in hepatobiliary surgery.

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

Spatial quantification of clinical biomarker pharmacokinetics through deep learning-based segmentation and signal-oriented analysis of MSOT data

Although multispectral optoacoustic tomography (MSOT) significantly evolved over the last several years, there is a lack of quantitative methods for analysing this type of image data. Current analytical methods characterise the MSOT signal in manually defined regions of interest outlining selected tissue areas. These methods demand expert knowledge of the sample anatomy, are time consuming, highly subjective and prone to user bias. Here we present our fully automated open-source MSOT cluster analysis toolkit Mcat that was designed to overcome these shortcomings. It employs a deep learning-based approach for initial image segmentation followed by unsupervised machine learning to identify regions of similar signal kinetics. It provides an objective and automated approach to quantify the pharmacokinetics and extract the biodistribution of biomarkers from MSOT data. We exemplify our generally applicable analysis method by quantifying liver function in a preclinical sepsis model whilst highlighting the advantages of our new approach compared to the severe limitations of existing analysis procedures.

Biomarkers of Cholestasis and Liver Injury in the Early Phase of Acute Respiratory Distress Syndrome and Their Pathophysiological Value

Background: Impaired liver function and cholestasis are frequent findings in critically ill patients and are associated with poor outcomes. We tested the hypothesis that hypoxic liver injury and hypoxic cholangiocyte injury are detectable very early in patients with ARDS, may depend on the severity of hypoxemia, and may be aggravated by the use of rescue therapies (high PEEP level and prone positioning) but could be attenuated by extracorporeal membrane oxygenation (ECMO). Methods: In 70 patients with ARDS, aspartate-aminotransferase (AST), alanin-aminotransferase (ALT) and gamma glutamyltransferase (GGT) were measured on the day of the diagnosis of ARDS and three more consecutive days (day 3, day 5, day 10), total bile acids were measured on day 0, 3, and 5. Results: AST levels increased on day 0 and remained constant until day 5, then dropped to normal on day 10 (day 0: 66.5 U/l; day 3: 60.5 U/l; day 5: 63.5 U/l, day 10: 32.1 U/l), ALT levels showed the exact opposite kinetic. GGT was already elevated on day 0 (91.5 U/l) and increased further throughout (day 3: 163.5 U/l, day 5: 213 U/l, day 10: 307 U/l), total bile acids levels increased significantly from day 0 to day 3 (p = 0.019) and day 0 to day 5 (p < 0.001), but not between day 3 and day 5 (p = 0.217). Total bile acids levels were significantly correlated to GGT on day 0 (p < 0.001), day 3 (p = 0.02), and in a trend on day 5 (p = 0.055). PEEP levels were significantly correlated with plasma levels of AST (day 3), ALT (day 5) and GGT (day 10). Biomarker levels were not associated with the use of ECMO, prone position, the cause of ARDS, and paO₂. Conclusions: We found no evidence of hypoxic liver injury or hypoxic damage to cholangiocytes being caused by the severity of hypoxemia in ARDS patients during the very early phase of the disease. Additionally, mean PEEP level, prone positioning, and ECMO treatment did not have an impact in this regard. Nevertheless, GGT levels were elevated from day zero and rising, this increase was not related to paO₂, prone position, ECMO treatment, or mean PEEP, but correlated to total bile acid levels.

Peripheral arterial tonometry as a method of measuring reactive hyperaemia correlates with organ dysfunction and prognosis in the critically ill patient: a prospective observational study

Predictions of mortality may help in the selection of patients who benefit from intensive care. Endothelial dysfunction is partially responsible for many of the organic dysfunctions in critical illness. Reactive hyperaemia is a vascular response of the endothelium that can be measured by peripheral arterial tonometry (RH-PAT). We aimed to assess if reactive hyperaemia is affected by critical illness and if it correlates with outcomes. Prospective study with a cohort of consecutive patients admitted to an Intensive Care Unit. RH-PAT was accessed on admission and on the 7th day after admission. Early and late survivors were compared to non-survivors. The effect of RH-PAT variation on late mortality was studied by a logistic regression model. The association between RH-PAT and severity scores and biomarkers of organic dysfunction was investigated by multivariate analysis. 86 patients were enrolled. Mean ln(RHI) on admission was 0.580 and was significantly lower in patients with higher severity scores (p < 0.01) and early non-survivors (0.388; p = 0.027). The model for prediction of early-mortality estimated that each 0.1 decrease in ln(RHI) increased the odds for mortality by 13%. In 39 patients, a 2nd RH-PAT measurement was performed on the 7th day. The variation of ln(RHI) was significantly different between non-survivors and survivors (- 24.2% vs. 63.9%, p = 0.026). Ln(RHI) was significantly lower in patients with renal and cardiovascular dysfunction (p < 0.01). RH-PAT is correlated with disease severity and seems to be an independent marker of early mortality, cardiovascular and renal dysfunctions. RH-PAT variation predicts late mortality. There appears to be an RH-PAT impairment in the acute phase of severe diseases that may be reversible and associated with better outcomes.

Liver-lung interactions in acute respiratory distress syndrome

Patients with liver diseases are at high risk for the development of acute respiratory distress syndrome (ARDS). The liver is an important organ that regulates a complex network of mediators and modulates organ interactions during inflammatory disorders. Liver function is increasingly recognized as a critical determinant of the pathogenesis and resolution of ARDS, significantly influencing the prognosis of these patients. The liver plays a central role in the synthesis of proteins, metabolism of toxins and drugs, and in the modulation of immunity and host defense. However, the tools for assessing liver function are limited in the clinical setting, and patients with liver diseases are frequently excluded from clinical studies of ARDS. Therefore, the mechanisms by which the liver participates in the pathogenesis of acute lung injury are not totally understood. Several functions of the liver, including endotoxin and bacterial clearance, release and clearance of pro-inflammatory cytokines and eicosanoids, and synthesis of acute-phase proteins can modulate lung injury in the setting of sepsis and other severe inflammatory diseases. In this review, we summarized clinical and experimental support for the notion that the liver critically regulates systemic and pulmonary responses following inflammatory insults. Although promoting inflammation can be detrimental in the context of acute lung injury, the liver response to an inflammatory insult is also pro-defense and pro-survival. A better understanding of the liver–lung axis will provide valuable insights into new diagnostic targets and therapeutic strategies for clinical intervention in patients with or at risk for ARDS.

Secondary hepatic dysfunction in pediatric intensive care unit: Risk factors and outcome

BACKGROUND

Hepatic dysfunction has a significant role in intensive care unit patients' morbidity and mortality.

AIM

To study the frequency, risk factors and outcome of secondary hepatic dysfunction in children admitted to the pediatric intensive care unit.

METHODS

Secondary hepatic dysfunction was defined as the development of abnormal liver functions in a patient without a previous liver disease during intensive care unit stay. The following data were collected: age, gender, indication of admission, type of organ dysfunction, presence of sepsis, shock, need for inotropic support or mechanical ventilation, administered medications and mortality scores. Liver function tests were done on admission and at 7-day intervals.

RESULTS

One hundred and fifty-one patients were included. Forty-three (28.5%) acquired secondary hepatic dysfunction. Several risk factors were significantly associated with secondary hepatic dysfunction: sepsis (p<0.001), cardiovascular events (p<0.001), hypoxia (p<0.001), number of administered antibiotics (P = 0.001), use of inotropes (p<0.001) and mechanical ventilation (p = 0.001). Secondary hepatic dysfunction was significantly associated with mortality and prolonged length of stay (P=<0.001).

CONCLUSION

Secondary hepatic dysfunction is a common finding in the pediatric intensive care unit. Sepsis, cardiovascular events and hypoxia, are the main risk factors for secondary hepatic dysfunction. Mortality and prolonged length of stay are strongly related to secondary hepatic dysfunction.

The role of bilirubin to albumin ratio as a predictor for mortality in critically ill patients without existing liver or biliary tract disease

Background:

Hyperbilirubinemia and hypoalbuminemia are frequently appeared and associated with poor prognosis in critically ill patients. We aim to evaluate the association between the bilirubin to albumin ratio and prognosis in intensive care unit (ICU) patients.

Methods:

This was a retrospective study of 731 patients who were admitted to the medical intensive care unit (MICU) at a tertiary-care center from July 2015 to September 2017. We analyzed the bilirubin to albumin ratio on admission to the MICU, including clinical characteristics and other examinations.

Results:

The overall 28-day survival of MICU patients was 69.1%. On univariate analysis, Acute Physiology and Chronic Health Evaluation (APACHE) II score (P<0.001), Sequential Organ Failure Assessment score (P<0.001), Simplified Acute Physiology Score II score (P<0.001), Creactive protein (P=0.015), and bilirubin/albumin ratio (P<0.001) were associated with mortality of ICU patients. The receiver operating characteristic curves for ICU patients mortality between bilirubin to albumin ratio and APACHE II score were not statistically significant (P=0.282). On multivariate analysis, higher APACHE II score (hazard ratio [HR], 1.05; 95% CI, 1.03 to 1.06; P<0.001) and bilirubin to albumin ratio (HR, 1.65; 95% CI, 1.23 to 2.20; P=0.001) were independently related to the ICU patient mortality.

Conclusions:

A higher bilirubin to albumin ratio was related to the unfavorable prognosis and mortality in critically ill patients.

Plasma Disappearance Rate of Indocyanine Green for Determination of Liver Function in Three Different Models of Shock

The measurement of the liver function via the plasma disappearance rate of indocyanine green (PDR_ICG) is a sensitive bed-side tool in critical care. Yet, recent evidence has questioned the value of this method for hyperdynamic conditions. To evaluate this technique in different hemodynamic settings, we analyzed the PDR_ICG and corresponding pharmacokinetic models after endotoxemia or hemorrhagic shock in rats. Male anesthetized Sprague-Dawley rats underwent hemorrhage (mean arterial pressure 35 ± 5 mmHg, 90 min) and 2 h of reperfusion, or lipopolysaccharide (LPS) induced moderate or severe (1.0 vs. 10 mg/kg) endotoxemia for 6 h (each n = 6). Afterwards, PDR_ICG was measured, and pharmacokinetic models were analyzed using nonlinear mixed effects modeling (NONMEM^®). Hemorrhagic shock resulted in a significant decrease of PDR_ICG, compared with sham controls, and a corresponding attenuation of the calculated ICG clearance in 1- and 2-compartment models, with the same log-likelihood. The induction of severe, but not moderate endotoxemia, led to a significant reduction of PDR_ICG. The calculated ICG blood clearance was reduced in 1-compartment models for both septic conditions. 2-compartment models performed with a significantly better log likelihood, and the calculated clearance of ICG did not correspond well with PDR_ICG in both LPS groups. 3-compartment models did not improve the log likelihood in any experiment. These results demonstrate that PDR_ICG correlates well with ICG clearance in 1- and 2-compartment models after hemorrhage. In endotoxemia, best described by a 2-compartment model, PDR_ICG may not truly reflect the ICG clearance.

Clearance of Indocyanine Green in Severe Pediatric Burns

BACKGROUND

Clearance of indocyanine green dye (ICGc) reflects sinusoidal perfusion and hepatocyte cell membrane function. Thus, ICGc is a reflection of the functional reserve of intact hepatocytes. The purpose of this study was to identify predictors of ICGc in severely burned children during the acute hospitalization and at the time of discharge from the intensive care unit (ICU). A secondary aim was to determine the relationship between liver size and patient ICGc.

METHODS

Twenty-six children (0.8-17 years old) with 35% or greater total body surface area burned (%TBSA-B) were included. Assessment of ICGc (in milliliters per minute per meter squared) was done during the acute hospitalization (median: 6 days after admission, median: 14 days postburn) and at the time of discharge from the ICU (median: 19 days after admission, median: 27 days postburn). Age, TBSA-B, % third-degree burns, inhalation injury, preexisting chronic malnutrition, hematocrit, liver dysfunction, and time from burn injury were incorporated in multiple linear regressions as predictive variables of ICGc. Only variables with p < 0.05 were retained in the final models.

RESULTS

Time from injury and age were the strongest predictors of ICGc during the acute admission but not at the time of discharge from the ICU. Time from injury was negatively associated with ICGc, whereas age was positively associated. At the time of discharge from the ICU, ICGc was increased in proportion to the %TBSA-B, whereas inhalation injury and preexisting chronic malnutrition were associated with lower ICGc. There was no correlation between change-to-predicted liver length and ICGc.

CONCLUSIONS

The intrinsic ability of the liver to extract ICG from plasma was lower in younger burned patients during the acute admission and in those with preexisting chronic malnutrition and inhalation injury at the time of discharge from the ICU.

LEVEL OF EVIDENCE

Prognostic/Epidemiologic, level III.

Disease-Associated Changes in Drug Transporters May Impact the Pharmacokinetics and/or Toxicity of Drugs: A White Paper From the International Transporter Consortium

Drug transporters are critically important for the absorption, distribution, metabolism, and excretion (ADME) of many drugs and endogenous compounds. Therefore, disruption of these pathways by inhibition, induction, genetic polymorphisms, or disease can have profound effects on overall physiology, drug pharmacokinetics, drug efficacy, and toxicity. This white paper provides a review of changes in transporter function associated with acute and chronic disease states, describes regulatory pathways affecting transporter expression, and identifies opportunities to advance the field.

Liver function assessment by indocyanine green plasma disappearance rate in patients with intra-abdominal hypertension after "non-hepatic" abdominal surgery

BACKGROUND AND OBJECTIVE

Liver function assessment in patients with intra-abdominal hypertension (IAH) after major abdominal surgery is complex and often confounding. Elevated intra-abdominal pressure (IAP) often occurs after major abdominal surgery, and is associated with decreased abdominal blood flow and organ dysfunction, and it could cause abdominal compartment syndrome (ACS), which is a life-threatening condition. Plasma disappearance rate (PDR) of indocyanine green (ICG) and ICG retention rate after 15 min (R15) were used to evaluate liver function and as a prognostic parameter after major abdominal surgery.

METHODS

In this prospective/observational study, 51 patients were followed in the surgical intensive care unit after major abdominal surgery (operation of the small and large intestine, stomach, pancreas, spleen, or resection of the abdominal aorta), 29 had IAH. The PDR-ICG and R15 were analyzed 24 h after surgery concurrently with IAP, APP, bilirubin, AST, ALT, prothrombin time, albumin, cardiac index, arterial lactate, oxygen delivery, MAP (mean arterial pressure), APACHE II (acute physiology and chronic health evaluation), SOFA (sequential organ failure assessment), and SAPS II (simplified acute physiology score). IAH has been defined as a peak intra-abdominal pressure (IAP) value of ≥12 mmHg, at a minimum, as two standardized measurements obtained 1-6 h apart.

RESULTS

The PDR-ICG measured 24 h after surgery was not different among groups (20.95% [SD = 10.34] vs 25.40% [SD = 7.42]), p = .094. ICG R15 was significantly higher in patients with IAH, 11.10% [SD = 13.82] vs 8.30 [SD = 11.46], p < .05, respectively. The PDR/ICG value was significantly lower in non-survivors than survivors (16.82 [SD = 10.87] vs 24.35 [SD = 8.48], p < .05).

CONCLUSIONS

The results suggest that PDR/ICG and ICG R15 are useful dynamic tests for evaluation of complex liver function and survival prediction after major abdominal surgery in patients with IAH.

Deterioration of Organ Function As a Hallmark in Sepsis: The Cellular Perspective

Development of organ dysfunction discriminates sepsis from uncomplicated infection. The paradigm shift implicated by the new sepsis-3 definition holds that initial impairment of any organ can pave the way for multiple organ dysfunction and death. Moreover, the role of the systemic inflammatory response, central element in previous sepsis definitions, has been questioned. Most strikingly, a so far largely underestimated defense mechanism of the host, i.e., "disease tolerance," which aims at maintaining host vitality without reducing pathogen load, has gained increasing attention. Here, we summarize evidence that a dysregulation of critical cellular signaling events, also in non-immune cells, might provide a conceptual framework for sepsis-induced dysfunction of parenchymal organs in the absence of significant cell death. We suggest that key signaling mediators, such as phosphoinositide 3-kinase, mechanistic target of rapamycin, and AMP-activated protein kinase, control the balance of damage and repair processes and thus determine the fate of affected organs and ultimately the host. Therapeutic targeting of these multifunctional signaling mediators requires cell-, tissue-, or organ-specific approaches. These novel strategies might allow stopping the domino-like damage to further organ systems and offer alternatives beyond the currently available strictly supportive therapeutic options.

Photonic monitoring of treatment during infection and sepsis: development of new detection strategies and potential clinical applications

Despite the strong decline in the infection-associated mortality since the development of the first antibiotics, infectious diseases are still a major cause of death in the world. With the rising number of antibiotic-resistant pathogens, the incidence of deaths caused by infections may increase strongly in the future. Survival rates in sepsis, which occurs when body response to infections becomes uncontrolled, are still very poor if an adequate therapy is not initiated immediately. Therefore, approaches to monitor the treatment efficacy are crucially needed to adapt therapeutic strategies according to the patient's response. An increasing number of photonic technologies are being considered for diagnostic purpose and monitoring of therapeutic response; however many of these strategies have not been introduced into clinical routine, yet. Here, we review photonic strategies to monitor response to treatment in patients with infectious disease, sepsis, and septic shock. We also include some selected approaches for the development of new drugs in animal models as well as new monitoring strategies which might be applicable to evaluate treatment response in humans in the future. Figure Label-free probing of blood properties using photonics.

Fast simultaneous assessment of renal and liver function using polymethine dyes in animal models of chronic and acute organ injury

Simultaneous assessment of excretory liver and kidney function is still an unmet need in experimental stress models as well as in critical care. The aim of the study was to characterize two polymethine-dyes potentially suitable for this purpose in vivo. Plasma disappearance rate and elimination measurements of simultaneously injected fluorescent dyes DY-780 (hepato-biliary elimination) and DY-654(renal elimination) were conducted using catheter techniques and intravital microscopy in animals subjected to different organ injuries, i.e. polymicrobial sepsis by peritoneal contamination and infection, ischemia-reperfusion-injury and glycerol-induced acute kidney-injury. DY-780 and DY-654 showed organ specific and determined elimination routes in both healthy and diseased animals. They can be measured simultaneously using near-infrared imaging and spectrophotometry. Plasma-disappearance rates of DY-780 and DY-654 are superior to conventional biomarkers in indicating hepatic or kidney dysfunction in different animal models. Greatest impact on liver function was found in animals with polymicrobial sepsis whereas glomerular damage due to glycerol-induced kidney-injury had strongest impact on DY-654 elimination. We therefore conclude that hepatic elimination and renal filtration can be assessed in rodents measuring plasma-disappearance rates of both dyes. Further, assessment of organ dysfunction by polymethine dyes correlates with, but outperforms conventional biomarkers regarding sensitivity and the option of spatial resolution if biophotonic strategies are applied. Polymethine-dye clearance thereby allows sensitive point-of-care assessment of both organ functions simultaneously.

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.

Hepatic Perfusion Alterations in Septic Shock Patients: Impact of Early Goal-directed Therapy

BACKGROUND

Early goal-directed therapy (EGDT) has become an important therapeutic management in early salvage stage of septic shock. However, splenic organs possibly remained hypoperfused and hypoxic despite fluid resuscitation. This study aimed to evaluate the effect of EGDT on hepatic perfusion in septic shock patients.

METHODS

A prospective observational study was carried out in early septic shock patients who were admitted to Intensive Care Unit within 24 h after onset and who met all four elements of the EGDT criteria after treatment with the standard EGDT procedure within 6 h between December 1, 2012 and November 30, 2013. The hemodynamic data were recorded, and oxygen metabolism and hepatic functions were monitored. An indocyanine green clearance test was applied to detect the hepatic perfusion. The patients' characteristics were compared before treatment (T0), immediately after EGDT (T1), and 24 h after EGDT (T2). This study is registered at ClinicalTrials.org, NCT02060773.

RESULTS

Twenty-one patients were included in the study; however, the hepatic perfusion data were not included in the analysis for two patients; therefore, 19 patients were eligible for the study. Hemodynamics data, as monitored by pulse-indicator continuous cardiac output, were obtained from 16 patients. There were no significant differences in indocyanine green plasma disappearance rate (ICG-PDR) and 15-min retention rate (R15) at T0 (11.9 ± 5.0%/min and 20.0 ± 13.2%), T1 (11.4 ± 5.1%/min and 23.6 ± 14.9%), and T2 (11.0 ± 4.5%/min and 23.7 ± 15.3%) (all P > 0.05). Both of the alterations of ICG-PDR and R15 showed no differences at T0, T1, and T2 in the patients of different subgroups that achieved different resuscitation goal numbers when elected (P > 0.05).

CONCLUSION

There were no hepatic perfusion improvements after EGDT in the early phase of patients with septic shock.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02060773 (https://clinicaltrials.gov/ct2/show/NCT02060773).

Incidence, laboratory detection and prognostic relevance of hypoxic hepatitis in cardiogenic shock

BACKGROUND

Despite the improvement of therapeutic options for patients in acute myocardial infarction (AMI), cardiogenic shock (CS) remains a complication with high mortality rates. Organ failure centrally determines the prognosis of these high-risk patients. Aim of the current study was to assess the incidence of hypoxic hepatitis (HH) in CS, its laboratory detection evaluating novel and established biomarkers and to estimate the prognostic relevance of HH in current clinical practice.

METHODS

In 172 patients with CS complicating AMI, blood samples were collected at admission and after 1 day as prespecified subanalysis of the intra-aortic balloon pumping IABP-SHOCK II trial. Classic parameters of HH were measured in addition to argininosuccinate synthase 1 and sulfotransferase isoform SULT2A1 was determined as new biomarker using standard enzyme-linked immunosorbent assay kits. All-cause mortality at 30 days was used for outcome assessment.

RESULTS

The overall mortality rate was 40%. The incidence of HH with an increase of aminotransferase levels to be 20 times above the upper normal level was 18%. Patients with HH had a distinctly higher 30-day mortality rate compared to patients without HH (68 vs. 34%; p < 0.001). After multivariable adjustment aspartate-aminotransferase (ASAT) remained an independent predictor of 30-day mortality together with serum lactate and serum creatinine, while the new biomarkers failed to predict outcome. Comparing different liver markers using receiver operating characteristic analysis, ASAT showed the highest area under the curve for the prediction of outcome.

CONCLUSIONS

HH occurs frequently in CS and is associated with particular poor outcome. As conventional biomarker, ASAT is the strongest laboratory predictor of outcome. ClinicalTrials.gov Identifier: NCT00491036.

Warm ischemia time-dependent variation in liver damage, inflammation, and function in hepatic ischemia/reperfusion injury

BACKGROUND

Hepatic ischemia/reperfusion (I/R) injury is characterized by hepatocellular damage, sterile inflammation, and compromised postoperative liver function. Generally used mouse I/R models are too severe and poorly reflect the clinical injury profile. The aim was to establish a mouse I/R model with better translatability using hepatocellular injury, liver function, and innate immune parameters as endpoints.

METHODS

Mice (C57Bl/6J) were subjected to sham surgery, 30min, or 60min of partial hepatic ischemia. Liver function was measured after 24h using intravital microscopy and spectroscopy. Innate immune activity was assessed at 6 and 24h of reperfusion using mRNA and cytokine arrays. Liver inflammation and function were profiled in two patient cohorts subjected to I/R during liver resection to validate the preclinical results.

RESULTS

In mice, plasma ALT levels and the degree of hepatic necrosis were strongly correlated. Liver function was bound by a narrow damage threshold and was severely impaired following 60min of ischemia. Severe ischemia (60min) evoked a neutrophil-dominant immune response, whereas mild ischemia (30min) triggered a monocyte-driven response. Clinical liver I/R did not compromise liver function and displayed a cytokine profile similar to the mild I/R injury model.

CONCLUSIONS

Mouse models using ≤30min of ischemia best reflect the clinical liver I/R injury profile in terms of liver function dynamics and type of immune response.

GENERAL SIGNIFICANCE

This short duration of ischemia therefore has most translational value and should be used to increase the prospects of developing effective interventions for hepatic I/R.

Hypoxic hepatitis after out-of-hospital cardiac arrest: Incidence, determinants and prognosis

AIM

Hypoxic hepatitis (HH) may complicate the course of resuscitated out-of-hospital cardiac arrest (OHCA) patients admitted in intensive care unit (ICU). Aims of this study were to assess the prevalence of HH, and to describe the factors associated with HH occurrence and outcome.

METHODS

We conducted an observational study over a 6-year period (2009-2014) in a cardiac arrest center. All non-traumatic OHCA patients admitted in the ICU after return of spontaneous circulation (ROSC) and who survived more than 24h were included. HH was defined as an elevation of alanine aminotransferase over 20 times the upper limit of normal during the first 72h after OHCA. Factors associated with HH and ICU mortality were picked up by multivariate logistic regression.

RESULTS

Among the 632 OHCA patients included in the study, HH was observed in 72 patients (11.4% (95% CI: 9.0%, 14.1%)). In multivariate analysis, time from collapse to ROSC [OR 1.02 per additional minute; 95% CI (1.00, 1.04); p=0.01], male gender [OR 0.53; 95% CI (0.29, 0.95); p=0.03] and initial shockable rhythm [OR 0.35; 95% CI (0.19, 0.65); p<0.01] were associated with HH occurrence. After adjustment for confounding factors, HH was associated with ICU mortality [OR 4.39; 95% CI (1.71, 11.26); p<0.01] and this association persisted even if occurrence of a post-CA shock was considered in the statistical model [OR 3.63; 95% CI (1.39, 9.48); p=0.01].

CONCLUSIONS

HH is not a rare complication after OHCA. This complication is mainly triggered by the duration of resuscitation and is associated with increased ICU mortality.

Prognostic impact of ICG-PDR in patients with hypoxic hepatitis

Background

Hepatic impairment is found in up to 20 % in critically ill patients. Hypoxic/ischemic hepatitis (HH) is a diffuse hepatic damage associated with high morbidity and mortality. Indocyanine green plasma disappearance rate (ICG-PDR) is an effective tool assessing liver function in acute and chronic hepatic diseases. Aim of this study was to evaluate the prognostic impact of ICG-PDR in comparison to established parameters for risk stratification.

Methods

Patients with HH were included in this prospective observational study and compared to cirrhosis, acute liver failure (ALF) and patients without underlying liver disease. ICG-PDR, measured non-invasively by finger pulse densitometry, was assessed on admission and in patients with HH serially and results were compared between groups. Diagnostic test accuracy of ICG-PDR predicting 28-day mortality was analyzed by receiver operating characteristics (ROC).

Results

ICG-PDR on admission was significantly lower in patients with liver diseases than in patients without hepatic impairment (median 5.7 %/min, IQR 3.8–7.9 vs. 20.7 %/min, IQR 14.1–25.4 %/min; p < 0.001). ICG-PDR predicted 28-day mortality independently of SOFA score and serum lactate in patients with underlying liver disease (HR 1.27, 95 % CI 1.10–1.45, p < 0.001). In patients with HH, ICG-PDR was identified as best predictor of 28-day mortality which performed significantly better than SOFA, lactate, INR and AST over course of time (p < 0.05). Best cut-off for identification of 28-day survivors was ICG-PDR ≥9.0 %/min 48 h after admission.

Conclusions

ICG-PDR is an independent predictor of mortality in patients with liver disease. Diagnostic test accuracy of ICG-PDR was superior to standard liver function parameters and established scoring systems in patients with HH.

Early Hepatic Dysfunction Is Associated with a Worse Outcome in Patients Presenting with Acute Respiratory Distress Syndrome: A Post-Hoc Analysis of the ACURASYS and PROSEVA Studies

Introduction

Bilirubin is well-recognized marker of hepatic dysfunction in intensive care unit (ICU) patients. Multiple organ failure often complicates acute respiratory distress syndrome (ARDS) evolution and is associated with high mortality. The effect of early hepatic dysfunction on ARDS mortality has been poorly investigated. We evaluated the incidence and the prognostic significance of increased serum bilirubin levels in the initial phase of ARDS.

Methods

The data of 805 patients with ARDS were retrospectively analysed. This population was extracted from two recent multicenter, prospective and randomised trials. Patients presenting with ARDS with a ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen < 150 mmHg measured with a PEEP ≥ 5 cm of water were included. The total serum bilirubin was measured at inclusion and at days 2, 4, 7 and 14. The primary objective was to analyse the bilirubin at inclusion according to the 90-day mortality rate.

Results

The 90-day mortality rate was 33.8% (n = 272). The non-survivors were older, had higher Sepsis-related Organ Failure Assessment (SOFA) score and were more likely to have a medical diagnosis on admission than the survivors. At inclusion, the SOFA score without the liver score (10.3±2.9 vs. 9.0±3.0, p<0.0001) and the serum bilirubin levels (36.1±57.0 vs. 20.5±31.5 μmol/L, p<0.0001) were significantly higher in the non-survivors than in the survivors. Age, the hepatic SOFA score, the coagulation SOFA score, the arterial pH level, and the plateau pressure were independently associated with 90-day mortality in patients with ARDS.

Conclusion

Bilirubin used as a surrogate marker of hepatic dysfunction and measured early in the course of ARDS was associated with the 90-day mortality rate.

Secondary Sclerosing Cholangitis in Critically Ill Patients: Clinical Presentation, Cholangiographic Features, Natural History, and Outcome: A Series of 16 Cases

Secondary sclerosing cholangitis in critically ill patients (SSC-CIP) is an important differential diagnosis in patients presenting with cholestasis and PSC-like cholangiographic changes in endoscopic retrograde cholangiography (ERC). As a relatively newly described entity, SSC-CIP is still underdiagnosed, and the diagnosis is often delayed. The present study aims to improve the early detection of SSC-CIP and the identification of its complications.A total of 2633 records of patients who underwent or were listed for orthotopic liver transplantation at the University Hospital Charité, Berlin, were analyzed retrospectively. The clinical presentation and outcome (mean follow-up 62.7 months) of the 16 identified SSC-CIP cases were reviewed.Cholestasis was the first sign of SSC-CIP. GGT was the predominant enzyme of cholestasis. Hypercholesterolemia occurred in at least 75% of the patients. SSC-CIP provoked a profound weight loss (mean 18 kg) in 94% of our patients. SSC-CIP was diagnosed by ERC in all patients. The 3 different cholangiographic features detected correspond roughly to the following stages: (I) evidence of biliary casts, (II) progressive destruction of intrahepatic bile ducts, and (III) picture of pruned tree. Biliary cast formation is a hallmark of SSC-CIP and was seen in 87% of our cases. In 75% of the patients, the clinical course was complicated by cholangiosepsis, cholangitic liver abscesses, acalculous cholecystitis, or gallbladder perforation. SSC-CIP was associated with worse prognosis; transplant-free survival was ∼40 months (mean).Because of its high rate of serious complications and unfavorable prognosis, it is imperative to diagnose SSC-CIP early and to differentiate SSC-CIP from other types of sclerosing cholangitis. Specific characteristics enable identification of SSC-CIP. Early cooperation with a transplant center and special attention to biliary complications are required after diagnosis of SSC-CIP.

Beneficial effects of dantrolene on sepsis-induced diaphragmatic dysfunction are associated with downregulation of high-mobility group box 1 and calpain-caspase-3 proteolytic pathway

BACKGROUND

Intracellular calcium overload is a major contributing factor to diaphragmatic dysfunction triggered by sepsis. In this study, the possible role of dantrolene, a ryanodine receptor inhibitor, in preventing the release of calcium from the sarcoplasmic reticulum in diaphragmatic dysfunction and weakness was explored.

METHODS

A middle-grade severity sepsis rat model was established for the effects of treatment with dantrolene, on diaphragm harvested 24 h after cecal ligation and puncture (CLP), and analyzed using functional, histologic, and biomarker assays.

RESULTS

It was found that in septic rats, treatment with dantrolene significantly improved the contractility, relaxation, and fatigue index of the diaphragm in a dose-dependent manner. The benefits are associated with improvement in ultrastructural changes of Z band integrity and myofilament arrangements along with increases both in the ratio of slow-twitch type composition. Moreover, dantrolene effectively inhibits the overexpression of high-mobility group box 1 and reduces the calpain-1-caspase-3 proteolytic activity.

CONCLUSIONS

Dantrolene can effectively attenuate the dysfunction of diaphragm in septic rats; Furthermore, the beneficial effects were associated with downregulation of high-mobility group box 1 and calpain-1-caspase-3 proteolytic activity.

Early Liver Dysfunction in Patients With Intra-Abdominal Infections

Liver dysfunction is commonly seen in patients with severe sepsis; however, few studies were reported in intra-abdominal infections (IAIs). This study was performed to assess the risk factors for early liver dysfunction (ELD) in patients with IAIs and to determine the effects of ELD on outcomes of these patients.From January 2011 to November 2014, a retrospective study that screened 421 patients with IAIs was performed. ELD was defined as an increase in serum total bilirubin (TB) >2 mg/dL or aminotransferases levels greater than twice the normal value within 48 hours after IAIs' onset. Patients with pre-existing liver disease or major hepatobiliary injury were excluded. Risk factors for ELD and outcomes were compared by univariate and multivariate analyses. Subgroup analysis was performed for ELD patients within 24 to 48 hours.Of 353 enrolled patients admitted with IAIs, 147 (41.6%) developed ELD. Significant independent risk factors for ELD were trauma (odds ratio [OR] 1.770, 95% confidential interval [CI] 1.126-2.783, P = 0.01) and abdominal compartment syndrome (ACS) (OR 3.199, 95% CI 1.184-8.640, P = 0.02). Successful source control <24 hours was shown to exert protection against ELD after 24 hours during IAIs (OR 0.193, 95% CI 0.091-0.409, P < 0.001). ELD was associated with significantly worse outcomes, including longer ICU length of stay and higher in-hospital mortality. Multivariate analysis also showed that development of ELD was a predisposing factor of mortality in IAIs patients (P < 0.001).ELD was a common complication in patients with IAIs associated with worse outcomes. Trauma and ACS were relevant risk factors. Early successful source control appeared to be an important method to prevent and/or reduce ELD in patients with IAIs.

Alterations in hepatic lobar function in regenerating rat liver

BACKGROUND

Ligation of a branch of the portal vein redirects portal blood to nonligated lobes resulting in lobar hypertrophy. Although the effect of portal vein ligation on liver volume is well documented, the parallel alterations in liver function are still the subject of controversy. Our aim was to assess the time-dependent reactions of regional hepatic function to portal vein ligation by selective biliary drainage.

METHODS

Male Wistar rats (n = 44) underwent 80% portal vein ligation. Before the operation as well as 1, 2, 3, 5, and 7 d after circulation, morphology and function (laboratory blood test; hepatic bile flow; plasma disappearance rate of indocyanine green; and biliary indocyanine green excretion) of the liver were examined.

RESULTS

Although portal vein ligation affected liver circulation and morphology to a great extent, serum albumin levels, bilirubin levels, and total hepatic bile flow did not change significantly after the operation. Nevertheless, plasma disappearance rate and biliary indocyanine green excretion indicated a temporary impairment of total liver function with the lowest value on the second day and normalization by the fifth day. Bile production and biliary indocyanine green excretion of ligated lobes decreased rapidly after the operation and remained persistently suppressed, whereas the secretory function of nonligated lobes--after a temporary decline--showed a greater increase than the weight of the lobes.

CONCLUSIONS

Portal vein ligation induced temporary impairment of total liver function, followed by rapid recovery mainly by reason of increase in the function of nonligated lobes. Functional increase in nonligated lobes was more pronounced than suggested by the degree of volume gain.

[Monitoring of liver function in the critically ill]

Liver failure and hepatic dysfunction represent diagnostic and therapeutic challenges for the intensivist. Besides acute liver failure, hypoxic hepatitis, sepsis and (secondary) sclerosing cholangitis may lead to massive liver dysfunction with subsequent multiorgan dysfunction syndrome that limits survival. Among classical laboratory parameters (so-called static liver parameters) liver function tests may help with the diagnosis to allow early treatment or prevention of liver dysfunction. The aim of this article is to present the current aspects of liver function monitoring and to provide guidelines to the intensivist for diagnosing liver dysfunction in the intensive care setting.

Indocyanine green plasma disappearance rate as dynamic liver function test in critically ill patients

BACKGROUND

Indocyanine green (ICG) is a water-soluble fluorescent dye that is bound to plasma protein when administered intravenously. Removal of ICG from the blood depends on hepatic blood flow, function of the parenchymal cells and biliary excretion. ICG elimination is described as a useful dynamic liver function test.

METHODS

In this review, we looked at the most recent literature to clarify why ICG is useful in critically ill patients, the validity of the ICG plasma disappearance rate (ICG-PDR) measured transcutaneously and whether ICG-PDR has any prognostic value.

CONCLUSION

In conclusion, measuring ICG-PDR is a valuable method for dynamic assessment of liver function, and is found to be a valuable prognostic tool in predicting survival for septic patients, patients presenting with acute liver failure and critically ill patients.

Biomarkers in Hepatic Disease: A Review Focused on Critically Ill Patients

The ability to make a diagnosis early and appropriately is paramount for the survival of the critically ill ICU patient. Along with the myriad physical examination and imaging modalities available, biomarkers provide a window on the disease process. Herein we review hepatic biomarkers in the context of the critical care patient.

Systemic CD14 inhibition attenuates organ inflammation in porcine Escherichia coli sepsis

Sepsis is an infection-induced systemic inflammatory response syndrome. Upstream recognition molecules, like CD14, play key roles in the pathogenesis. The aim of the present study was to investigate the effect of systemic CD14 inhibition on local inflammatory responses in organs from septic pigs. Pigs (n = 34) receiving Escherichia coli-bacteria or E. coli-lipopolysaccharide (LPS) were treated with an anti-CD14 monoclonal antibody or an isotype-matched control. Lungs, liver, spleen, and kidneys were examined for bacteria and inflammatory biomarkers. E. coli and LPS were found in large amounts in the lungs compared to the liver, spleen, and kidneys. Notably, the bacterial load did not predict the respective organ inflammatory response. There was a marked variation in biomarker induction in the organs and in the effect of anti-CD14. Generally, the spleen produced the most cytokines per weight unit, whereas the liver contributed the most to the total load. All cytokines were significantly inhibited in the spleen. Interleukin-6 (IL-6) was significantly inhibited in all organs, IL-1β and IP-10 were significantly inhibited in liver, spleen, and kidneys, and tumor necrosis factor, IL-8, and PAI-1 were inhibited only in the spleen. ICAM-1 and VCAM-1 was significantly inhibited in the kidneys. Systemic CD14-inhibition efficiently, though organ dependent, attenuated local inflammatory responses. Detailed knowledge on how the different organs respond to systemic inflammation in vivo, beyond the information gained by blood examination, is important for our understanding of the nature of systemic inflammation and is required for future mediator-directed therapy in sepsis. Inhibition of CD14 seems to be a good candidate for such treatment.

RAGE blockade and hepatic microcirculation in experimental endotoxaemic liver failure

BACKGROUND

Activation of the receptor for advanced glycation endproducts (RAGE) causes sustained activation of multiple inflammatory pathways. Therefore, RAGE has potential as a new therapeutic target in sepsis. The aim of this study was to analyse whether RAGE blockade in vivo prevents microcirculatory dysfunction and subsequent tissue injury in endotoxaemic liver failure.

METHODS

The hepatic microcirculation was analysed using intravital fluorescence microscopy in murine livers exposed to galactosamine/lipopolysaccharide (G/L) and treated with an anti-RAGE antibody (abRAGE) either 12 h before or h after exposure to G/L. Blood and liver tissue samples were harvested for analysis of leucocyte tissue infiltration, apoptotic and necrotic damage as well as RAGE downstream pathway signalling.

RESULTS

Sinusoidal perfusion failure in livers exposed to G/L was reduced significantly by both pretreatment and post-treatment with abRAGE. Hepatic inflammation induced by exposure to G/L was also attenuated by abRAGE administration, as shown by a 55 per cent reduction in sinusoidal leucocyte stasis, a 65 per cent decrease in venular leucocyte rolling and adhesion, and an 85 per cent reduction in leucocyte tissue infiltration. Treatment with abRAGE markedly reduced hepatocellular apoptosis and necrosis in livers exposed to G/L, and blunted the rise in plasma high-mobility group protein B1 levels. Finally, G/L-induced activation of the mitogen-activated protein kinase cascade was also reduced significantly by blockade of RAGE.

CONCLUSION

RAGE plays an important role in mediating endotoxaemic liver damage. RAGE blockade may have potential therapeutic value. SURGICAL RELEVANCE: The innate immune response to endoxaemia is initiated by a group of pattern recognition receptors, including the receptor for advanced glycation endproducts (RAGE). As RAGE is well known for perpetuation of inflammatory processes, blockade of this receptor might be of particular value in reducing or even halting endoxaemia-related organ disorders. Using intravital fluorescence microscopy this study demonstrated in vivo that pretreatment, but also post-treatment, with a RAGE-blocking antibody attenuated hepatic microcirculatory deterioration and leucocyte recruitment, and thus diminished liver injury in a murine model of endotoxaemic organ failure. These data underline the important role of RAGE in the innate immune response and support the potential therapeutic value of blocking this pattern recognition receptor.

Physiological and biochemical basis of clinical liver function tests: a review

OBJECTIVE

To review the literature on the most clinically relevant and novel liver function tests used for the assessment of hepatic function before liver surgery.

BACKGROUND

Postoperative liver failure is the major cause of mortality and morbidity after partial liver resection and develops as a result of insufficient remnant liver function. Therefore, accurate preoperative assessment of the future remnant liver function is mandatory in the selection of candidates for safe partial liver resection.

METHODS

A MEDLINE search was performed using the key words "liver function tests," "functional studies in the liver," "compromised liver," "physiological basis," and "mechanistic background," with and without Boolean operators.

RESULTS

Passive liver function tests, including biochemical parameters and clinical grading systems, are not accurate enough in predicting outcome after liver surgery. Dynamic quantitative liver function tests, such as the indocyanine green test and galactose elimination capacity, are more accurate as they measure the elimination process of a substance that is cleared and/or metabolized almost exclusively by the liver. However, these tests only measure global liver function. Nuclear imaging techniques ((99m)Tc-galactosyl serum albumin scintigraphy and (99m)Tc-mebrofenin hepatobiliary scintigraphy) can measure both total and future remnant liver function and potentially identify patients at risk for postresectional liver failure.

CONCLUSIONS

Because of the complexity of liver function, one single test does not represent overall liver function. In addition to computed tomography volumetry, quantitative liver function tests should be used to determine whether a safe resection can be performed. Presently, (99m)Tc-mebrofenin hepatobiliary scintigraphy seems to be the most valuable quantitative liver function test, as it can measure multiple aspects of liver function in, specifically, the future remnant liver.

Hepatic excretory function in sepsis: implications from biophotonic analysis of transcellular xenobiotic transport in a rodent model

Introduction

Hepatobiliary elimination of endo- and xenobiotics is affected by different variables including hepatic perfusion, hepatocellular energy state and functional integrity of transporter proteins, all of which are altered during sepsis. A particular impairment of hepatocellular transport at the canalicular pole resulting in an accumulation of potentially hepatotoxic compounds would have major implications for critical care pharmacology and diagnostics.

Methods

Hepatic transcellular transport, that is, uptake and hepatobiliary excretion, was studied in a rodent model of severe polymicrobial sepsis by two different biophotonic techniques to obtain insights into the handling of potentially toxic endo- and xenobiotics in sepsis. Direct and indirect in vivo imaging of the liver was performed by intravital multifluorescence microscopy and non-invasive whole-body near-infrared (NIRF) imaging after administration of two different, primarily hepatobiliary excreted xenobiotics, the organic anionic dyes indocyanine green (ICG) and DY635. Subsequent quantitative data analysis enabled assessment of hepatic uptake and fate of these model substrates under conditions of sepsis.

Results

Fifteen hours after sepsis induction, animals displayed clinical and laboratory signs of multiple organ dysfunction, including moderate liver injury, cholestasis and an impairment of sinusoidal perfusion. With respect to hepatocellular transport of both dyes, excretion into bile was significantly delayed for both dyes and resulted in net accumulation of potentially cytotoxic xenobiotics in the liver parenchyma (for example, specific dye fluorescence in liver at 30 minutes in sham versus sepsis: ICG: 75% versus 89%; DY635 20% versus 40% of maximum fluorescence; P < 0.05). Transcutaneous assessment of ICG fluorescence by whole body NIRF imaging revealed a significant increase of ICG fluorescence from the 30th minute on in the bowel region of the abdomen in sham but not in septic animals, confirming a sepsis-associated failure of canalicular excretion.

Conclusions

Hepatocytes accumulate organic anions under conditions of sepsis-associated organ dysfunction. These results have potential implications for monitoring liver function, critical care pharmacology and the understanding of drug-induced liver injury in the critically ill.

How to assess liver function?

PURPOSE OF REVIEW

The liver comprises a multitude of parenchymal and nonparenchymal cells with diverse metabolic, hemodynamic and immune functions. Available monitoring options consist of 'static' laboratory parameters, quantitative tests of liver function based on clearance, elimination or metabolite formation and scores, most notably the 'model for end-stage liver disease'. This review aims at balancing conventional markers against 'dynamic' tests in the critically ill.

RECENT FINDINGS

There is emerging evidence that conventional laboratory markers, most notably bilirubin, and the composite model for end-stage liver disease are superior to assess cirrhosis and their acute decompensation, while dynamic tests provide information in the absence of preexisting liver disease. Bilirubin and plasma disappearance rate of indocyanine green reflecting static and dynamic indicators of excretory dysfunction prognosticate unfavorable outcome, both, in the absence and presence of chronic liver disease better than other functions or indicators of injury. Although dye excretion is superior to conventional static parameters in the critically ill, it still underestimates impaired canalicular transport, an increasingly recognized facet of excretory dysfunction.

SUMMARY

Progress has been made in the last year to weigh static and dynamic tests to monitor parenchymal liver functions, whereas biomarkers to assess nonparenchymal functions remain largely obscure.

Relationship between intra-abdominal pressure and indocyanine green plasma disappearance rate: hepatic perfusion may be impaired in critically ill patients with intra-abdominal hypertension

Background

Monitoring hepatic blood flow and function might be crucial in treating critically ill patients. Intra-abdominal hypertension is associated with decreased abdominal blood flow, organ dysfunction, and increased mortality. The plasma disappearance rate (PDR) of indocyanine green (ICG) is considered to be a compound marker for hepatosplanchnic perfusion and hepatocellular membrane transport and correlates well with survival in critically ill patients. However, correlation between PDR_ICG and intra-abdominal pressure (IAP) remains poorly understood. The aim of this retrospective study was to investigate the correlation between PDR_ICG and classic liver laboratory parameters, IAP and abdominal perfusion pressure (APP). The secondary goal was to evaluate IAP, APP, and PDR_ICG as prognostic factors for mortality.

Methods

A total of 182 paired IAP and PDR_ICG measurements were performed in 40 critically ill patients. The mean values per patient were used for comparison. The IAP was measured using either a balloon-tipped stomach catheter connected to an IAP monitor (Spiegelberg, Hamburg, Germany, or CiMON, Pulsion Medical Systems, Munich, Germany) or a bladder FoleyManometer (Holtech Medical, Charlottenlund, Denmark). PDR_ICG was measured at the bedside using the LiMON device (Pulsion Medical Systems, Munich, Germany). Primary endpoint was hospital mortality.

Results

There was no significant correlation between PDR_ICG and classic liver laboratory parameters, but PDR_ICG did correlate significantly with APP (R = 0.62) and was inversely correlated with IAP (R = -0.52). Changes in PDR_ICG were associated with significant concomitant changes in APP (R = 0.73) and opposite changes in IAP (R = 0.61). The IAP was significantly higher (14.6 ± 4.6 vs. 11.1 ± 5.3 mmHg, p = 0.03), and PDR_ICG (10 ± 8.3 vs. 15.9 ± 5.2%, p = 0.02) and APP (43.6 ± 9 vs. 57.9 ± 12.2 mmHg, p < 0.0001) were significantly lower in non-survivors.

Conclusions

PDR_ICG is positively correlated to APP and inversely correlated to IAP. Changes in APP are associated with significant concomitant changes in PDR_ICG, while changes in IAP are associated with opposite changes in PDR_ICG, suggesting that an increase in IAP may compromise hepatosplanchnic perfusion. Both PDR_ICG and IAP are correlated with outcome. Measurement of PDR_ICG may be a useful additional clinical tool to assess the negative effects of increased IAP on liver perfusion and function.

Hyperresponsiveness of mice deficient in plasma-secreted sphingomyelinase reveals its pivotal role in early phase of host response

Plasma secretion of acid sphingomyelinase is a hallmark of cellular stress response resulting in the formation of membrane embedded ceramide-enriched lipid rafts and the reorganization of receptor complexes. Consistently, decompartmentalization of ceramide formation from inert sphingomyelin has been associated with signaling events and regulation of the cellular phenotype. Herein, we addressed the question of whether the secretion of acid sphingomyelinase is involved in host response during sepsis. We found an exaggerated clinical course in mice genetically deficient in acid sphingomyelinase characterized by an increased bacterial burden, an increased phagocytotic activity, and a more pronounced cytokine storm. Moreover, on a functional level, leukocyte-endothelial interaction was found diminished in sphingomyelinase-deficient animals corresponding to a distinct leukocytes’ phenotype with respect to rolling and sticking as well as expression of cellular surface proteins. We conclude that hydrolysis of membrane-embedded sphingomyelin, triggered by circulating sphingomyelinase, plays a pivotal role in the first line of defense against invading microorganisms. This function might be essential during the early phase of infection leading to an adaptive response of remote cells and tissues.

Clinical review: The liver in sepsis

During sepsis, the liver plays a key role. It is implicated in the host response, participating in the clearance of the infectious agents/products. Sepsis also induces liver damage through hemodynamic alterations or through direct or indirect assault on the hepatocytes or through both. Accordingly, liver dysfunction induced by sepsis is recognized as one of the components that contribute to the severity of the disease. Nevertheless, the incidence of liver dysfunction remains imprecise, probably because current diagnostic tools are lacking, notably those that can detect the early liver insult. In this review, we discuss the epidemiology, diagnostic tools, and impact on outcome as well as the pathophysiological aspects, including the cellular events and clinical picture leading to liver dysfunction. Finally, therapeutic considerations with regard to the weakness of the pertinent specific approach are examined.

Pharmacokinetic evaluation of voriconazole treatment in critically ill patients undergoing continuous venovenous hemofiltration

INTRODUCTION

Voriconazole represents an essential part of antimicrobial therapy in critically ill patients. The aim of this study was to exclude a significant alteration in voriconazole pharmacokinetics in critically ill patients undergoing continuous venovenous hemofiltration (CVVH).

METHODS

Six patients dependent on CVVH with evidence of an invasive mycotic infection treated with intravenous voriconazole at the standard dosing regimen were investigated. The total serum concentration of voriconazole in arterial blood and the concentration in ultrafiltrate were measured by reverse-phase high-performance liquid chromatography with ultraviolet detection. The authors profiled a 5-point pharmacokinetic concentration-time curve during the 12-hour standard maintenance dosing interval and derived the basic pharmacokinetic parameters.

RESULTS

The serum voriconazole concentration did not decrease <1.0 mg/L at any time point, and the mean was 4.3 ± 2.6 mg/L and the median (range) 3.6 (9.0) mg/L. The sieving coefficient of the drug did not exceed 0.30 in any patient (0.22 ± 0.08). The mean serum AUC0-12, the mean total clearance, and the mean clearance via CVVH were 53.52 ± 29.97 mg·h/L [the median (range) of 57.74 (62.34) mg·h/L], 0.11 ± 0.07 L·h-1·kg-1, and 0.007 ± 0.003 L·h-1·kg-1, respectively. The clearance by the CVVH method ranged from 4% to 20% of the total drug clearance. The disposition of voriconazole was not compromised. The mean elimination half-life was 27.58 ± 35.82 hours [the median of 13.10 (92.21) hours], and the mean distribution volume value was 3.28 ± 3.10 L/kg [the median of 2.01 (8.10) L/kg]. Marked variability in serum concentrations, elimination half-life, distribution volume, and total clearance was seen. Half of the patients showed some drug accumulation.

CONCLUSIONS

The clearance of voriconazole by CVVH is not clinically significant. In view of this finding, voriconazole dose adjustment in patients undergoing the standard method of CVVH is not required. However, the observed potential for an unpredictable voriconazole accumulation suggests the usefulness for monitoring its levels in critically ill patients.

Insulin inhibits hepatocyte iNOS expression induced by cytokines by an Akt-dependent mechanism

Hepatocyte inducible nitric oxide synthese (iNOS) expression is a tightly controlled pathway that mediates hepatic inflammation and hepatocyte injury in a variety of disease states. We have shown that cyclic adenosine monophosphate (cAMP) regulates cytokine-induced hepatocyte iNOS expression through mechanisms that involve protein kinase B/Akt. We hypothesized that insulin, which activates Akt signaling in hepatocytes, as well as signaling through p38 and MAPK p42/p44, would regulate iNOS expression during inflammation. In primary rat hepatocytes, insulin inhibited cytokine-stimulated nitrite accumulation and iNOS expression in a dose-dependent manner. Inhibition of MAPK p42/p44 with PD98059 had no effect on iNOS activation, whereas SB203580 to block p38 reversed insulin's inhibitory effect. However, insulin did not increase p38 activation and inhibition of p38 signaling with a dominant negative p38 plasmid had no effect on cytokine- or insulin-mediated effects on iNOS. We found that SB203580 blocked insulin-induced Akt activation. Inhibition of Akt signaling with LY294002 or a dominant negative Akt plasmid increased cytokine-stimulated nitrite production and iNOS protein expression and blocked the inhibitory effects of insulin. NF-κB induces iNOS expression and can be regulated by Akt, but insulin had no effect on cytokine-mediated IκBα levels or NF-κB p65 translocation. Our data demonstrate that insulin inhibits cytokine-stimulated hepatocyte iNOS expression and does so through effects on Akt-mediated signaling.

Compartmental modeling in the analysis of biological systems

Compartmental models are composed of sets of interconnected mixing chambers or stirred tanks. Each component of the system is considered to be homogeneous, instantly mixed, with uniform concentration. The state variables are concentrations or molar amounts of chemical species. Chemical reactions, transmembrane transport, and binding processes, determined in reality by electrochemical driving forces and constrained by thermodynamic laws, are generally treated using first-order rate equations. This fundamental simplicity makes them easy to compute since ordinary differential equations (ODEs) are readily solved numerically and often analytically. While compartmental systems have a reputation for being merely descriptive they can be developed to levels providing realistic mechanistic features through refining the kinetics. Generally, one is considering multi-compartmental systems for realistic modeling. Compartments can be used as "black" box operators without explicit internal structure, but in pharmacokinetics compartments are considered as homogeneous pools of particular solutes, with inputs and outputs defined as flows or solute fluxes, and transformations expressed as rate equations.Descriptive models providing no explanation of mechanism are nevertheless useful in modeling of many systems. In pharmacokinetics (PK), compartmental models are in widespread use for describing the concentration-time curves of a drug concentration following administration. This gives a description of how long it remains available in the body, and is a guide to defining dosage regimens, method of delivery, and expectations for its effects. Pharmacodynamics (PD) requires more depth since it focuses on the physiological response to the drug or toxin, and therefore stimulates a demand to understand how the drug works on the biological system; having to understand drug response mechanisms then folds back on the delivery mechanism (the PK part) since PK and PD are going on simultaneously (PKPD).Many systems have been developed over the years to aid in modeling PKPD systems. Almost all have solved only ODEs, while allowing considerable conceptual complexity in the descriptions of chemical transformations, methods of solving the equations, displaying results, and analyzing systems behavior. Systems for compartmental analysis include Simulation and Applied Mathematics, CoPasi (enzymatic reactions), Berkeley Madonna (physiological systems), XPPaut (dynamical system behavioral analysis), and a good many others. JSim, a system allowing the use of both ODEs and partial differential equations (that describe spatial distributions), is used here. It is an open source system, meaning that it is available for free and can be modified by users. It offers a set of features unique in breadth of capability that make model verification surer and easier, and produces models that can be shared on all standard computer platforms.

Neutrophils and intravascular immunity in the liver during infection and sterile inflammation

The liver is a target of many inflammatory pathologies of both infectious and noninfectious etiology. As key effectors of the innate immune system, neutrophils are critical for defense against microbial infections but are often the source of profound collateral damage to host tissues during disease states. In this article based on the authors' presentation at the 2011 Society of Toxicologic Pathology Annual Symposium, they review the molecular mechanisms of neutrophil recruitment to the liver in response to sepsis/endotoxemia, as well as sterile inflammation, and discuss variations in the molecular choreography of neutrophil trafficking in response to these different insults. Furthermore, the authors discuss the functional contributions of neutrophils within the liver microvasculature during severe sepsis, including their contributions to both host defense and organ damage. Given that inappropriate neutrophilic inflammation contributes to the pathogenesis of many liver diseases, a thorough understanding of the molecular mechanisms that regulate the recruitment of neutrophils to the liver, and their functions therein, may reveal new avenues for therapeutic interventions to treat inflammatory liver pathologies.

A physiologically based model of hepatic ICG clearance: interplay between sinusoidal uptake and biliary excretion

Although indocyanine green (ICG) has long been used for the assessment of liver function, the respective roles of sinusoidal uptake and canalicular excretion in determining hepatic ICG clearance remain unclear. Here this issue was addressed by incorporating a liver model into a minimal physiological model of ICG disposition that accounts of the early distribution phase after bolus injection. Arterial ICG concentration-time data from awake dogs under control conditions and from the same dogs while anesthetized with 3.5% isoflurane were subjected to population analysis. The results suggest that ICG elimination in dogs is uptake limited since it depends on hepatocellular uptake capacity and on biliary excretion but not on hepatic blood flow. Isoflurane caused a 63% reduction in cardiac output and a 33% decrease in the ICG biliary excretion rate constant (resulting in a 26% reduction in elimination clearance) while leaving unchanged the sinusoidal uptake rate. The terminal slope of the concentration-time curve, K, correlated significantly with elimination clearance. The model could be useful for assessing the functions of sinusoidal and canalicular ICG transporters.

Characteristics of clinical sepsis reflected in a reliable and reproducible rodent sepsis model

BACKGROUND

Sepsis models are frequently based on induction of peritonitis, with cecal ligation and puncture reflecting the prototypical model. However, there is an ongoing discussion about the limitations of these models due to their variability in progression and outcome. Since standardization is a cornerstone of experimental models, we aimed to develop a reliable and reproducible procedure for induction of peritonitis.

MATERIALS AND METHODS

A human stool batch was processed for -80° storage. For induction of peritonitis in fluid-resuscitated rats, a defined volume of stool suspension from this batch was injected intraperitoneally. For characterization of the model, physiologic and inflammatory changes were evaluated after sepsis induction. Survival analyses with the same batch were repeated in four independent experiments over a time period of 16 mo.

RESULTS

The polymicrobial infection resulted in severe peritoneal inflammation with a systemic increase in cytokines. The mortality rate at 15 h was 29% and this was reproducible over a 16 mo time period. If antibiotic treatment was applied, a 50% survival was achieved. Laboratory markers indicated a progressive multi-organ dysfunction, while blood gas analysis showed respiratory compensation of a metabolic acidosis, and maintenance of PaO(2). Intravital microscopy of the liver revealed an impaired microcirculation. A decreased hemostatic potential was demonstrated by rotational thromboelastometry. Despite clinical recovery within 3 d, surviving animals showed laboratory and histologic signs of persisting inflammation even after 2 wk.

CONCLUSIONS

This model reflects many features of human sepsis. Application of an infectious focus that is both quantitatively and qualitatively defined assures high reproducibility. Moreover, the procedure is simple and can be easily standardized.

The impact of resuscitated fecal peritonitis on the expression of the hepatic bile salt transporters in a porcine model

Sepsis is often associated with cholestatic liver dysfunction caused by changes in the expression profile of hepatic bile salt transporters. However, in rodent endotoxin models, the role of ischemic hepatitis caused by liver hypoperfusion cannot be delineated. We hypothesized that hepatocytes change their expression pattern of bile salt transporters during early severe sepsis despite adequate resuscitation. Fifteen anesthetized and instrumented pigs were randomized to either fecal peritonitis (n = 8) or control (n = 7). Resuscitation was performed by hydroxyethyl starch and norepinephrine infusion. Hemodynamic parameters and markers of cholestatic and ischemic hepatic dysfunction were recorded. At baseline and after 21 h, messenger RNA (mRNA) and protein expression of bile salt transporters was determined by quantitative real-time polymerase chain reaction and immunohistochemistry, respectively, on in vivo liver biopsies. All resuscitated septic pigs developed a normotensive hyperdynamic circulation with increased portal flow. After 21 h of peritonitis, no signs of biochemical or histological cholestasis were present. Na-taurocholate cotransporting polypeptide and bile salt export pump mRNA were downregulated by 83% (P = 0.001) and 67% (P = 0.001), respectively, in comparison with controls, whereas multidrug resistance-associated protein 4 (MRP4) mRNA was upregulated by 85% (P = 0.02). Bile salt export pump and MRP2 staining were downregulated in septic pigs. During early porcine fluid-resuscitated sepsis, hepatic basolateral influx (Na-taurocholate cotransporting polypeptide) and canalicular efflux (bile salt export pump) of bile salts were downregulated without hemodynamic signs of hepatic hypoperfusion or biochemical signs of cholestasis. In parallel, the basolateral escape transport (MRP4) was markedly upregulated, possibly as an early adaptive response to counteract hepatocellular accumulation of toxic bile acids.

Critical care "normality": individualized versus protocolized care

Patients with critical illness are heterogeneous, with differing physiologic requirements over time. Goal-directed therapy in the emergency room demonstrates that protocolized care could result in improved outcomes. Subsequent studies have confirmed benefit with such a "bundle-based approach" in the emergency room and in preoperative and postoperative scenarios. However, this cannot be necessarily extrapolated to the medium-term and long-term care pathway of the critically ill patient. It is likely that the development of mitochondrial dysfunction could result in goal-directed types of approaches being detrimental. Equally, arterial pressure aims are likely to be considerably different as the patient's physiology moves toward "hibernation." The agents we utilize as sedative and pressor agents have considerable effects on immune function and the inflammatory profile, and should be considered as part of the total clinical picture. The role of gut failure in driving inflammation is considerable, and the drive to feed enterally, regardless of aspirate volume, may be detrimental in those with degrees of ileus, which is often a difficult diagnosis in the critically ill. The pathogenesis of liver dysfunction may be, at least in part, related to venous engorgement that will contribute toward portal hypertension and gut edema. This, in association with loss of the hepatosplanchnic buffer response, it is likely to contribute to venous pooling in the abdominal cavity, impaired venous return, and decreased central blood volumes. Therapies such as those used in "small-for-size syndrome" may have a role in the chronic stages of septic vascular failure.

Drug dosing considerations for the critically ill patient with liver disease

Hepatic dysfunction in the critically ill patient presents a unique challenge to clinicians when designing pharmacotherapeutic treatment plans. Overall, the literature regarding drug dosing in critically ill patients with hepatic dysfunction is incomplete and current tools available to bedside clinicians have limitations. Despite these challenges, rational drug regimens can be implemented by critical care nurses who consider the potential impact of hepatic dysfunction on drug pharmacokinetics. This information can be applied clinically and careful monitoring plans can be implemented to assess a drug for efficacy and safety. This article reviews the pharmacokinetic changes that can occur in hepatic failure, identifies practical ways to quantify the severity of dysfunction, and discusses general drug dosing strategies in this patient population.