The 1995 Ciba-Geigy Award Lecture. Intrinsic regulation of hepatic blood flow

Lesion or Pseudolesion? A Comprehensive Description of Perfusion-Based Liver Alterations on Contrast-Enhanced Computed Tomography and Literature Review

ABSTRACT

Pseudolesions on contrast-enhanced computed tomography represent a diagnostic challenge for radiologists because they could be difficult to distinguish from true space-occupying lesions. This article aims to provide a detailed overview of these entities based on radiological criteria (hyperattenuation or hypoattenuation, localization, morphology), as well as a brief review of the hepatic vascular anatomy and pathophysiological process. Relevant examples from hospital case series are reported as helpful hints to assist radiologists in recognizing and correctly diagnosing these abnormalities.

Hemodynamic alterations with large spontaneous splenorenal shunt ligation during adult deceased donor liver transplantation

Background

A large spontaneous splenorenal shunt (SRS) will greatly impact portal inflow to the graft during liver transplantation (LT). Direct ligation of a large SRS is an uncommon surgical procedure and the hemodynamic consequences of this procedure are unknown.

Methods

In this retrospective study, we described our technique for direct ligation of a large SRS and the consequent hemodynamic changes during LT. 3-Dimensional computed tomography and Doppler ultrasonography were used to evaluate SRS and portal vein blood flow volume (PFV).

Results

A total of 22 recipients had large SRS including 13 with PFV <85 ml/min/100 g (ligation group) and 9 with PFV ≥85 ml/min/100 g (no ligation group). The diameter of SRS was significantly larger in the ligation group than in the non-ligation group (22.92 ± 4.18 vs. 16.24 ± 3.60 mm; p = 0.0009). In all ligation patients, the SRS was easily identified and isolated, it was located just below the distal pancreas and beside the inferior mesenteric vein. PV flow increased significantly from 68.74 ± 8.77 to 116.80 ± 16.50 ml/min/100 g (p < 0.0001) after ligation; this was followed by a reduction in peak systolic velocity of the hepatic artery from 58.17 ± 14.87 to 46.67 ± 13.28 cm/s (p = 0.0013).

Conclusions

Direct ligation of large SRS was an effective and safe surgical procedure to overcome the problem of portal hypoperfusion during LT.

Grayscale and Spectral Doppler Ultrasound in the Diagnosis of Hepatic Veno-occlusive Disease/Sinusoidal Obstruction Syndrome After Hematopoietic Stem Cell Transplantation in Children

The aim of this study is to determine the ultrasound criteria in the diagnosis of hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) after hematopoietic stem cell transplantation (HSCT) in children. A total of 158 pediatric patients underwent HSCT between January 2016 and January 2018. In all, 71 patients with clinically suspicious hepatic VOD/SOS have been followed with serial ultrasound examinations. Hepatomegaly, gallbladder wall thickening, ascites, pleural effusion, reverse flow in the portal vein, and diameter and peak systolic velocity of the hepatic artery were evaluated. Patients were divided into 2 groups retrospectively: VOD/SOS and non-VOD/SOS. The predictive value of all findings was determined, respectively. Gallbladder wall thickening, increase of diameter and peak systolic velocity of the hepatic artery, and the presence of ascites are highly predictive for VOD/SOS (P=0.001 and < 0.05). The reversed portal venous flow was developed in 3 patients in the VOD/SOS group, no significant difference was found between the 2 groups (P>0.05). Hepatomegaly was recorded in 29 (70.7%) patients in the VOD/SOS group, 13 of them was presented related to a primary disease. Pleural effusion is not associated with the diagnosis of VOD/SOS (P>0.05). Gallbladder wall edema, an increase of peak systolic velocity of the hepatic artery, and the presence of ascites are highly related to the diagnosis of VOD/SOS in children after HSCT. Ultrasound findings must be correlated with clinical criteria.

Ultrasound in Hepatic Veno-occlusive Disease (HVOD) after Pediatric Hematopoietic Stem Cell Transplantation (HSCT): Comparison of Diagnostic Criteria Including the Pediatric Criteria of European Society for Blood and Marrow Transplantation (EBMT)

The European Society for Blood and Marrow Transplantation (EBMT) has recently announced new diagnostic criteria for pediatric hepatic veno-occlusive disease (HVOD) after hematopoietic stem cell transplantation (HSCT). We retrospectively inspected 97 ultrasound exams of 60 pediatric HSCT patients, and compared its diagnostic value using the Baltimore, Seattle and pediatric EBMT criteria. Nine of the ten patients who were diagnosed as HVOD only in the EBMT criteria had severe or very severe HVOD. In the Seattle and EBMT criteria, portal vein velocity, peak systolic velocity and resistance index of hepatic artery, gallbladder wall thickening and ascites were statistically significant. No ultrasound variable showed significant association in the Baltimore criteria. All patients with portal vein velocity below 10 cm/s were in higher EBMT grade. A scoring system was developed, to evaluate the overall relationship of the ultrasound findings with the diagnosis of HVOD, showing fair (0.768 and 0.733) AUC in the ROC curve of EBMT and Seattle criteria.

Liver Transplantation

The field of liver transplantation has changed since the MELD scoring system became the most widely used donor allocation tool. Due to the MELD-based allocation system, sicker patients with higher MELD scores are being transplanted. Persistent organ donor shortages remain a challenging issue, and as a result, the wait-list mortality is a persistent problem for most of the regions. This chapter focuses on deceased donor and live donor liver transplantation in patients with complications of portal hypertension. Special attention will also be placed on donor-recipient matching, perioperative management of transplant patients, and the impact of hepatic hemodynamics on transplantation.

Vascular input function correction of inflow enhancement for improved pharmacokinetic modeling of liver DCE-MRI

PURPOSE

To propose a simple method to correct vascular input function (VIF) due to inflow effects and to test whether the proposed method can provide more accurate VIFs for improved pharmacokinetic modeling.

METHODS

A spoiled gradient echo sequence-based inflow quantification and contrast agent concentration correction method was proposed. Simulations were conducted to illustrate improvement in the accuracy of VIF estimation and pharmacokinetic fitting. Animal studies with dynamic contrast-enhanced MR scans were conducted before, 1 week after, and 2 weeks after portal vein embolization (PVE) was performed in the left portal circulation of pigs. The proposed method was applied to correct the VIFs for model fitting. Pharmacokinetic parameters fitted using corrected and uncorrected VIFs were compared between different lobes and visits.

RESULTS

Simulation results demonstrated that the proposed method can improve accuracy of VIF estimation and pharmacokinetic fitting. In animal study results, pharmacokinetic fitting using corrected VIFs demonstrated changes in perfusion consistent with changes expected after PVE, whereas the perfusion estimates derived by uncorrected VIFs showed no significant changes.

CONCLUSION

The proposed correction method improves accuracy of VIFs and therefore provides more precise pharmacokinetic fitting. This method may be promising in improving the reliability of perfusion quantification. Magn Reson Med 79:3093-3102, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Simultaneous acquisition sequence for improved hepatic pharmacokinetics quantification accuracy (SAHA) for dynamic contrast-enhanced MRI of liver

PURPOSE

To propose a simultaneous acquisition sequence for improved hepatic pharmacokinetics quantification accuracy (SAHA) method for liver dynamic contrast-enhanced MRI.

METHODS

The proposed SAHA simultaneously acquired high temporal-resolution 2D images for vascular input function extraction using Cartesian sampling and 3D large-coverage high spatial-resolution liver dynamic contrast-enhanced images using golden angle stack-of-stars acquisition in an interleaved way. Simulations were conducted to investigate the accuracy of SAHA in pharmacokinetic analysis. A healthy volunteer and three patients with cirrhosis or hepatocellular carcinoma were included in the study to investigate the feasibility of SAHA in vivo.

RESULTS

Simulation studies showed that SAHA can provide closer results to the true values and lower root mean square error of estimated pharmacokinetic parameters in all of the tested scenarios. The in vivo scans of subjects provided fair image quality of both 2D images for arterial input function and portal venous input function and 3D whole liver images. The in vivo fitting results showed that the perfusion parameters of healthy liver were significantly different from those of cirrhotic liver and HCC.

CONCLUSIONS

The proposed SAHA can provide improved accuracy in pharmacokinetic modeling and is feasible in human liver dynamic contrast-enhanced MRI, suggesting that SAHA is a potential tool for liver dynamic contrast-enhanced MRI. Magn Reson Med 79:2629-2641, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Changes in liver perfusion and function before and after percutaneous occlusion of spontaneous portosystemic shunt

PURPOSE

To evaluate changes in liver perfusion after occlusion of spontaneous portosystemic shunt and to analyze mechanisms of liver profile improvement.

MATERIALS AND METHODS

Liver function changes and portal venous and hepatic arterial blood flow were evaluated using perfusion CT before and after shunt occlusion in 23 patients who underwent percutaneous occlusion of spontaneous portosystemic shunt because of gastric varices (n = 15) or hepatic encephalopathy (n = 8).

RESULTS

Portal venous blood flow was significantly higher at 1 week (278.7 ml/min, 92.7-636.7, p = 0.012), 1 month (290.0 ml/min, 110.1-560.1, p < 0.001) and 3 months (299.6 ml/min, 156.7-618.5, p = 0.033) after shunt occlusion than the baseline (220.9 ml/min, 49.5-566.7). Hepatic arterial liver blood flow became lower than the baseline (132.3 ml/min, 47.9-622.3) after shunt occlusion, but a significant decrease was observed only at 1 month later (107.9 ml/min, 45.8-263.6 p = 0.027). Serum albumin concentration became significantly higher than the baseline (3.4 mg/dl, 1.9-4.5) at 1 month (3.8 mg/dl, 2.3-4.3, p = 0.018) and 3 months (3.9 mg/dl, 2.6-4.3, p = 0.024) after shunt occlusion.

CONCLUSION

Shunt occlusion increases portal venous blood flow and decreases hepatic arterial blood flow, thereby improving the liver profile.

The Diagnostic Value of Hepatic Arterial Velocity in Venoocclusive Disease After Pediatric Hematopoietic Stem Cell Transplantation

The aim of this study was to determine usefulness of measurements of maximal systolic velocity of the hepatic artery with Doppler ultrasonography in the diagnosis of venoocclusive disease (VOD) after hematopoietic stem cell transplantation. We prospectively obtained 5 sonograms per patient: pretransplantation, day +1, +7, +14, and +28 on 36 nonconsecutive children who underwent hematopoietic stem cell transplantation. We examined the hepatic artery, the portal, hepatic and splenic veins, the thickness of the gallbladder wall, the presence of ascites, and the liver and spleen size. The diagnosis of VOD was based on clinical and laboratory data. Patients were divided into 2 groups: those with VOD (n=18) and those without VOD (n=18). The variance of 2 groups was analyzed. Vmax of the hepatic artery had a strong correlation with clinical VOD diagnosis (P<0.001). There was no statistically significant difference in the other Doppler parameters. The results of our study showed that the measurement of Vmax of the hepatic artery can provide important support in the diagnosis of VOD and can be useful in the follow-up of treatment response.

Anesthetic considerations for liver diseases unique to pregnancy

Liver diseases that are most unique to pregnancy consist of hyperemesis gravidarum, acute fatty liver of pregnancy, intrahepatic cholestasis of pregnancy, and hemolysis, elevated liver enzymes and low platelets syndrome. In this review, risk factors, etiology, symptoms, diagnosis, prognosis and treatment of each entity followed by principles of anesthetic management based on the case reports or retrospective records will be addressed.

Prediction of portal and hepatic blood flow from intake level data in cattle

Interest is growing in developing integrated postabsorptive metabolism models for dairy cattle. An integral part of linking a multi-organ postabsorptive model is the prediction of nutrient fluxes between organs, and thus blood flow. The purpose of this paper was to use a multivariate meta-analysis approach to model portal blood flow (PORBF) and hepatic venous blood flow (HEPBF) simultaneously, with evaluation of hepatic arterial blood flow (ARTBF; ARTBF=HEPBF - PORBF) and PORBF/HEPBF (%) as calculated values. The database used to develop equations consisted of 296 individual animal observations (lactating and dry dairy cows and beef cattle) and 55 treatments from 17 studies, and a separate evaluation database consisted of 34 treatment means (lactating dairy cows and beef cattle) from 9 studies obtained from the literature. Both databases had information on dry matter intake (DMI), metabolizable energy intake (MEI), body weight, and a basic description of the diet including crude protein intake and forage proportion of the diet (FP; %). Blood flow (L/h or L/kg of BW^0.75/h) and either DMI or MEI (g or MJ/d or g or MJ/kg of BW^0.75/d) were examined with linear and quadratic fits. Equations were developed using cow within experiment and experiment as random effects, and blood flow location as a repeated effect. Upon evaluation with the evaluation database, equations based on DMI typically resulted in lower root mean square prediction errors, expressed as a % of the observed mean (rMSPE%) and higher concordance correlation coefficient (CCC) values than equations based on MEI. Quadratic equation terms were frequently nonsignificant, and the quadratic equations did not outperform their linear counterparts. The best performing blood flow equations were PORBF (L/h)=202 (±45.6) + 83.6 (±3.11) × DMI (kg/d) and HEPBF (L/h)=186 (±45.4) + 103.8 (±3.10) × DMI (kg/d), with rMSPE% values of 17.5 and 16.6 and CCC values of 0.93 and 0.94, respectively. The residuals (predicted - observed) for PORBF/HEPBF were significantly related to the forage % of the diet, and thus equations for PORBF and HEPBF based on forage and concentrate DMI were developed: PORBF (L/h)=210 (±51.0) + 82.9 (±6.43) × forage (kg of DM/d) + 82.9 (±6.04) × concentrate (kg of DM/d), and HEPBF (L/h)=184 (±50.6) + 92.6 (±6.28) × forage (kg of DM/d) + 114.2 (±5.88) × concentrate (kg of DM/d), where rMSPE% values were 17.5 and 17.6 and CCC values were 0.93 and 0.94, respectively. Division of DMI into forage and concentrate fractions improved the joint Bayesian information criterion value for PORBF and HEPBF (Bayesian information criterion=6,512 vs. 7,303), as well as slightly improved the rMSPE and CCC for ARTBF and PORBF/HEPBF. This was despite minimal changes in PORBF and HEPBF predictions. Developed equations predicted blood flow well and can easily be used within a postabsorptive model of nutrient metabolism. Results also suggest different sensitivity of PORBF and HEPBF to the composition of DMI, and accounting for this difference resulted in improved ARTBF predictions.

Hepatic arterial buffer response: pathologic evidence in non-cirrhotic human liver with extrahepatic portal vein thrombosis

Increase in hepatic arterial flow in response to reduced portal flow (hepatic arterial buffer response) has been demonstrated experimentally and surgically. We provide pathologic evidence for hepatic arterial buffer response in non-cirrhotic patients with extrahepatic portal vein thrombosis and elucidate the histopathologic spectrum of non-cirrhotic portal vein thrombosis. Liver biopsies and resections from non-cirrhotic patients with extra-hepatic portal vein thrombosis were retrieved. Morphologic features, extent of CD34 staining, outer diameters, luminal diameters and wall thickness of hepatic arteries cut in cross-section and outer diameters of cross-sectioned paired bile ducts were compared with age- and gender-matched controls. There were 12 male and 9 female patients. Measurements of 280 and 193 arteries from patients and controls, respectively, demonstrated statistically significant (P<0.05) arterial dilatation (increase in percentage of arterial lumen to outer diameter) and arterial wall thinning in resection specimens of non-cirrhotic patients with extra-hepatic portal vein thrombosis. Subtle and/or focal dilatation of central veins, portal veins and sinusoids; focal trabecular thinning/thickening and mild ductular reaction were common findings in both the patient and control groups. Diffuse and obvious changes, and portal vein absence or attenuation were seen only in the patient group. Capillarization of sinusoids was not seen on CD34 stain. Two patients showed significant ductular reaction, one of who developed biliary strictures on follow-up. Hepatic arterial dilatation and wall thinning in non-cirrhotic patients with portal vein thrombosis provide pathologic evidence of hepatic arterial buffer response in the human liver. Obvious and diffuse sinusoidal dilatation and absence or attenuation of portal veins are highly suggestive of extrahepatic portal vein thrombosis in non-cirrhotic patients with portal hypertension. Periportal shunt vessels, hypervascular portal tracts, muscularized portal veins, large thick-walled or dilated arteries aid diagnosis but are rare findings. Normal or near-normal biopsies do not rule out portal vein thrombosis.

[Anesthesia with liver failure]

Liver failure can be categorized into acute liver failure, chronic liver failure and acute decompensation of chronic liver failure, the so-called acute-on-chronic liver failure, the incidence of which has increased over the last few years. Liver failure leads to a variety of pathophysiological changes where the extent is dependent on the nature and duration of the liver disease. This includes restriction of synthesis and metabolism, such as coagulation defects. Especially chronic liver failure is associated with malfunction of extrahepatic organs, such as the cardiovascular system, the respiratory system and the kidneys. In addition to these pathophysiological alterations the Child-Turcotte-Pugh classification (CTP) and the model of end stage liver disease (MELD) are used for perioperative risk stratification.

Addressing the Global Burden of Trauma in Major Surgery

Despite a technically perfect procedure, surgical stress can determine the success or failure of an operation. Surgical trauma is often referred to as the "neglected step-child" of global health in terms of patient numbers, mortality, morbidity, and costs. A staggering 234 million major surgeries are performed every year, and depending upon country and institution, up to 4% of patients will die before leaving hospital, up to 15% will have serious post-operative morbidity, and 5-15% will be readmitted within 30 days. These percentages equate to around 1000 deaths and 4000 major complications every hour, and it has been estimated that 50% may be preventable. New frontline drugs are urgently required to make major surgery safer for the patient and more predictable for the surgeon. We review the basic physiology of the stress response from neuroendocrine to genomic systems, and discuss the paucity of clinical data supporting the use of statins, beta-adrenergic blockers and calcium-channel blockers. Since cardiac-related complications are the most common, particularly in the elderly, a key strategy would be to improve ventricular-arterial coupling to safeguard the endothelium and maintain tissue oxygenation. Reduced O2 supply is associated with glycocalyx shedding, decreased endothelial barrier function, fluid leakage, inflammation, and coagulopathy. A healthy endothelium may prevent these "secondary hit" complications, including possibly immunosuppression. Thus, the four pillars of whole body resynchronization during surgical trauma, and targets for new therapies, are: (1) the CNS, (2) the heart, (3) arterial supply and venous return functions, and (4) the endothelium. This is termed the Central-Cardio-Vascular-Endothelium (CCVE) coupling hypothesis. Since similar sterile injury cascades exist in critical illness, accidental trauma, hemorrhage, cardiac arrest, infection and burns, new drugs that improve CCVE coupling may find wide utility in civilian and military medicine.

Hepatic arterial vasodilation is independent of portal hypertension in early stages of cirrhosis

Introduction

The compensatory increase in hepatic arterial flow with a decrease in portal venous flow is known as the hepatic arterial buffer response. In cirrhosis with elevated portal pressure, the vascular resistance of the hepatic artery is decreased. Whether this lower resistance of the hepatic artery is a consequence of portal hypertension or not remains unknown.

Study Aim

The aim of the study was to investigate the hepatic arterial resistance and response to vasoconstriction in cirrhosis without portal hypertension (normal portal resistance).

Methods

Cirrhosis was induced by CCl₄-inhalation for 8 weeks (8W, normal portal resistance) and for 12–14 weeks (12W, elevated portal resistance). Bivascular liver perfusion was performed at 8W or 12W and dose response curves of methoxamine were obtained in the presence or absence of LNMMA (nitric oxide synthase blocker). Vascular resistances of the hepatic artery (HAR), portal vein (PVR) and sinusoids (SVR) were measured. Western Blot (WB) and Immunohistochemistry (IHC) were done to measure eNOS and HIF 1a expression.

Results

HAR in both groups of cirrhotic animals (8W and 12W) were lower compared to controls. Dose response curves to methoxamine revealed lower HAR in both cirrhotic models (8W and 12W) regardless the magnitude of portal resistance. LNMMA corrected the dose response curves in cirrhosis (8W and 12W) to control. WB and IHC show increased protein expression of eNOS and HIF1a in 8W and 12W.

Conclusion

Hepatic arterial resistance is decreased in cirrhosis independent of portal resistance. Vasodilation of the hepatic artery in cirrhosis seems to be influenced by hypoxia rather than increase in portal resistance. Nitric oxide is the main vasodilator.

Intravenous hypnotic regimens in patients with liver disease; a review article

CONTEXT

The liver as an important organ in the body has many essential functions in physiological processes. One of the major activities of liver is drug metabolism. Hepatic dysfunction affecting hepatic physiological activities, especially drug metabolism can cause many problems during anesthesia and administration of different drugs to patients.

EVIDENCE ACQUISITION

Studies on hepatic disorders and hypnotic anesthetics prescribed in hepatic disorders were included in this review. For this purpose, reliable databases were used.

RESULTS

Anesthesia should be performed with caution in patients with hepatic dysfunction and drugs with long half-life should be avoided in these patients.

CONCLUSIONS

A review of the literature on the use of hypnotic drugs in patients with liver dysfunction showed that some hypnotic drugs used during anesthesia could be safely used in patients with impaired liver function. In these patients, certain drugs should be used with caution.

Anesthesia for patients with liver disease

CONTEXT

Liver plays an important role in metabolism and physiological homeostasis in the body. This organ is unique in its structure and physiology. So it is necessary for an anesthesiologist to be familiar with various hepatic pathophysiologic conditions and consequences of liver dysfunction.

EVIDENCE ACQUISITION

WE SEARCHED MEDLINE (PUB MED, OVID, MD CONSULT), SCOPUS AND THE COCHRANE DATABASE FOR THE FOLLOWING KEYWORDS: liver disease, anesthesia and liver disease, regional anesthesia in liver disease, epidural anesthesia in liver disease and spinal anesthesia in liver disease, for the period of 1966 to 2013.

RESULTS

Although different anesthetic regimens are available in modern anesthesia world, but anesthetizing the patients with liver disease is still really tough. Spinal or epidural anesthetic effects on hepatic blood flow and function is not clearly investigated, considering both the anesthetic drug-induced changes and outcomes. Regional anesthesia might be used in patients with advanced liver disease. In these cases lower drug dosages are used, considering the fact that locally administered drugs have less systemic effects. In case of general anesthesia it seems that using inhalation agents (Isoflurane, Desflurane or Sevoflurane), alone or in combination with small doses of fentanyl can be considered as a reasonable regimen. When administering drugs, anesthetist must realize and consider the substantially changed pharmacokinetics of some other anesthetic drugs.

CONCLUSIONS

Despite the fact that anesthesia in chronic liver disease is a scary and pretty challenging condition for every anesthesiologist, this hazard could be diminished by meticulous attention on optimizing the patient's condition preoperatively and choosing appropriate anesthetic regimen and drugs in this setting. Although there are paucity of statistics and investigations in this specific group of patients but these little data show that with careful monitoring and considering the above mentioned rules a safe anesthesia could be achievable in these patients.

Role of vasodilation during normothermic machine perfusion of DCD porcine livers

INTRODUCTION

Normothermic machine perfusion (NMP) of the liver is a promising preservation modality that holds the potential to better preserve and even repair marginal grafts. In spite of several literature studies showing the benefits of NMP over cold storage, there is paucity of data regarding the mechanisms involved in the optimization of the microcirculation during preservation of these organs. We present our data on the impact of different vasodilators on DCD porcine livers preserved with NMP.

MATERIALS AND METHODS

Livers from 15 female Yorkshire pigs (30-40 kg) were subjected to 60 min of WIT followed by 10 h of NMP. Group PC (n = 5) received a prostacyclin analog (epoprostenol sodium) and the AD group (n = 5) received adenosine, whereas group WV (n = 5) was perfused without using any vasodilator. Liver function was assessed by measuring, liver enzyme levels, bile production rate, and histological analysis.

RESULTS

At the end of perfusion, the PC group showed significantly lower AST (583 ± 62 vs. 2471 ± 745 and 2547 ± 690 IU/dl), ALT (41 ± 3 vs. 143 ± 28 and 111 ± 25 IU/dl) and LDH (840 ± 85 vs. 2756 ± 408 and 4153 ± 1569 IU/dl) levels compared to the AD and WV groups respectively (p<0.05). Bile production was significantly higher in the PC group compared to the AD group and WV, respectively (95 ± 9 vs. 37 ± 10 and 45 ± 18ml) (p<0.05). Histological samples of the PC group showed preserved hepatic architecture while those of the AD group and WV showed sinusoidal dilatation, architectural distortion, and profuse intraparenchymal hemorrhage.

CONCLUSIONS

Maintenance of optimal microcirculatory homeostasis using proper vasodilators is a key factor in NMP of DCD livers.

"Small-for-flow" syndrome: shifting the "size" paradigm

The "small-for-size" syndrome and "post-hepatectomy liver failure" refers to the development of liver failure (hyperbilirubinemia, coagulopathy, encephalopathy and refractory ascites) resulting from the reduction of liver mass beyond a certain threshold. This complication is associated with a high mortality and is a major concern in liver transplantation involving reduced liver grafts from deceased and living donors as well as in hepatic surgeries involving extended resections of liver mass. The limiting threshold for liver resection or transplantation is currently predicted based on the mass of the remnant liver (or donor graft) in relation to the body weight of the patient, with a ratio above 0.8 being considered safe. This approach, however, has proved inaccurate, because some patients develop the "small-for-size" syndrome despite complying with the "safe" threshold while other patients who surpass the threshold do not develop it. We hypothesize that the development of the "small-for-size" syndrome is not exclusively determined by the ratio of the mass of the liver remnant (or graft) to the body weight, but it is instead strictly determined by the hemodynamic parameters of the hepatic circulation. This hypothesis is based in recent clinical and experimental reports showing that relative portal hyperperfusion is a critical factor in the development of the "small-for-size" syndrome and that maneuvers that manipulate the hepatic vascular inflow are able to prevent the development of the syndrome despite liver-to-body weight ratios well below the "limiting" threshold. Measurements of hepatic blood flow and pressure, however, are not routinely performed in hepatic surgeries. Focusing on the "flow" rather than in the "size" may improve our understanding of the pathophysiology of the "small-for-size" syndrome and "post-hepatectomy liver failure" and it would have important implications for the clinical management of patients at risk. First, hepatic hemodynamic parameters would have to be measured in hepatic surgeries. Second, these parameters (in addition to liver mass) would be the principal basis for deciding the "safe" threshold of viable liver parenchyma. Third, the hepatic hemodynamic parameters are amenable to manipulation and, consequently, the "safe" threshold may also be manipulated. Shifting the paradigm from "small-for-size" to "small-for-flow" syndrome would thus represent a major step for optimizing the use of donor livers, for expanding the indications of hepatic surgery, and for increasing the safety of these procedures.

[Small-for-size: experimental findings for liver surgery]

The characteristics of the hepatic macrocirculation, i.e., the parallel portal-venous and arterial blood supply, is of utmost relevance for liver surgery. With extended hepatectomy or transplantation of a reduced-size liver the remaining or transplanted liver tissue is overperfused because the liver fails to regulate the portal-venous inflow. This portal hyperperfusion is responsible for the initiation of liver cell proliferation but represents at the same time one of the substantial events in the pathogenesis of the small-for-size syndrome. Portal-venous hyperperfusion, the so-called hepatic arterial buffer response, which describes the semi-reciprocal relationship between the portal-venous and hepatic arterial blood flows, leads to an arterial hypoperfusion of the small-for-size liver. In this article experimental and clinical data are discussed which underline the high but so far overseen relevance of this arterial underperfusion in the development of a small-for-size syndrome.

Descending aortic blood flow during aortic cross-clamp indicates postoperative splanchnic perfusion and gastrointestinal function in patients undergoing aortic reconstruction

BACKGROUND

The purpose of this observational study was to investigate the relationship between splanchnic and renal blood flow during infrarenal aortic cross-clamp (XC) and postoperative gastrointestinal perfusion and function.

METHODS

Descending aortic blood flow (DABF) was continuously monitored with an oesophageal Doppler monitor (Cardio-Q, Deltex Ltd, Chichester, UK) in 31 patients undergoing elective abdominal aortic aneurysm repair. Cardiac output (CO) was determined by indocyanine green dilution before, during, and after XC. Perioperative gastrointestinal perfusion was assessed by gastric intramucosal pH (pHi, Tonocap, GE Healthcare, Helsinki, Finland). Postoperative gastrointestinal recovery was assessed by the number of postoperative days until the patient successfully resumed solid food intake. The relationship between the mean DABF during XC and gastric pHi after XC release and postoperative gastrointestinal recovery was analysed with Spearman's correlation coefficient.

RESULTS

accounted for ∼ 55% of CO during XC and significantly decreased during XC, despite arterial pressure remaining within an optimal range. There were two distinct relationships between DABF during XC and gastric pHi after XC release. Gastric pHi steeply and linearly declined when indexed DABF was below 0.82 litre min(-1) m(-2). Above this critical value, there was no linear relationship between them. The duration of postoperative gastrointestinal dysfunction was inversely correlated with the mean DABF during XC. The best cut-off value of the mean indexed DABF during XC to prevent prolonged gastrointestinal dysfunction was 1.2 litre min(-1) m(-2).

CONCLUSIONS

Decreased DABF during XC associates splanchnic hypoperfusion after XC release and delayed recovery of gastrointestinal function.

A critical appraisal of the hemodynamic signal driving liver regeneration

BACKGROUND

Many aspects of the signaling mechanisms involved in the initiation of hepatic regeneration are under current investigation. Nevertheless, the actual mechanisms switching liver regeneration on and off are still unknown. Hemodynamic changes in the liver following partial hepatectomy have been suggested to be a primary stimulus in triggering liver regeneration. Most of the new knowledge about the impact of hemodynamic changes on liver regeneration is both conceptually important and directly relevant to clinical problems.

PURPOSE

The purpose of this review is therefore to exclusively address the hemodynamic signal driving the liver regeneration process.

The role of the A2a receptor agonist, regadenoson, in modulating hepatic artery flow in the porcine small-for-size liver graft

BACKGROUND

Hepatic artery vasoconstriction plays a major role in the pathophysiology of the small-for-size (SFS) liver graft injury and is reversed by adenosine. The A2a adenosine receptor (AR) has been suggested to be one of the key receptors that modulate hepatic hemodynamic changes. The aim of the study is to define the effects of the A2a AR agonist, regadenoson, in modulating hepatic artery flow (HAF) in SFS liver grafts of a porcine model.

METHODS

Seven female recipient pigs (66-70 kg) receiving 20% liver grafts were treated with regadenoson, 0.1 ug/kg/min starting on POD1 (n = 7). Results were compared with those with untreated 20% liver grafts (n= 8). The recipients were observed for 14 d. Hepatic artery flow (HAF) and portal vein flow (PVF) were recorded. Liver biopsies and serum samples were also taken at the designed time points through postoperative day (POD)14.

RESULTS

Dose-response curves of regadenoson established 0.1 ug/kg/min as the most effective dose of regadenoson for maintaining an increase in HAF. No adverse effects were seen with regadenoson infusion. HAF immediately increased by up to 2.2-fold after regadenoson infusion. The levels of daily average of HAF and percentage of HAF in total liver blood flow were 34.5% and 41.8%, respectively, higher in the regadenoson group than in the untreated group. Histologic scores of hepatic artery spasm and bile duct necrosis were significantly lower in the regadenoson group than in the untreated group (P = 0.01 and 0.04, respectively). The complication rates of hepatic artery thrombosis and gastrointestinal bleeding were lower in the regadenoson group than in the untreated group (0/7, 0% versus 2/8, 25% and 0/7, 0% versus 2/8 and 25%, respectively). The 14-d survival rates were 4/7 (57.1 %) in regadenoson group compared with 2/8 (25%) in the untreated group.

CONCLUSION

Adenosine A2a AR agonist, regadenoson, increases HAF in the recipients of SFS grafts with modest improvements in outcome.

Fetal hemodynamic development in macrosomic growth

OBJECTIVE

To determine the venous and arterial hemodynamics underlying macrosomic fetal growth.

METHODS

Fifty-eight healthy women who previously had given birth to a large neonate were included in a prospective longitudinal study. Of these, 29 gave birth to neonates with birth weight ≥ 90th percentile and were included in the statistical analysis. Umbilical vein blood flow and Doppler measurements of the ductus venosus, left portal vein and the hepatic, splenic, superior mesenteric, cerebral and umbilical arteries were repeated at 3-5 examinations during the second half of pregnancy and compared with the corresponding reference values. Ultrasound biometry was used to estimate fetal weight.

RESULTS

Umbilical blood flow increased faster in macrosomic fetuses, showed less blunting near term and was also significantly higher when normalized for estimated fetal weight (P < 0.0001). The portocaval perfusion pressure of the liver (expressed by the ductus venosus systolic blood velocity) and the left portal vein blood velocity (expressing umbilical venous distribution to the right liver lobe) were significantly higher. Systolic velocity was higher in the splenic, superior mesenteric, cerebral and umbilical arteries, while the pulsatility index was unaltered in the cerebral, hepatic, splenic and mesenteric arteries, but lower in the umbilical artery.

CONCLUSIONS

There is an augmented umbilical flow in macrosomic fetuses particularly near term, also when normalized for estimated fetal weight, providing increased liver perfusion, including the right liver lobe. Signs of increased vascular cross section and flow are also seen on the arterial side but not expressed in the pulsatility index of organs with prominent auto-regulation (i.e., brain, liver, spleen and gut).

Liver resection associated with mini porto-caval shunt as salvage treatment in patients with progression of hepatocellular carcinoma before liver transplantation: a case report

Tumor progression before orthotopic liver transplantation (OLT) is the main cause of dropouts from waiting lists among patients with hepatocellular carcinoma (HCC). Performing a porto-caval shunt (PCS) before parenchymal liver transection has the potential to allow an extended hepatectomy in patients with decompensated liver cirrhosis, reducing portal hyperflow and therefore the sinusoidal shear-stress on the remnant liver. We report the case of a 59-year-old man affected by hepatitis C virus (HCV)-related decompensated liver cirrhosis (Child Pugh score presentation, C-10; Model for End Stage Liver Disease score, 18) and HCC (2 lesions of 2 and 2.8 cm). The patient began the evaluation to join the OLT waiting list, but, in the 3 months required to complete the evaluation, he developed tumor progression: 3 HCC lesions, the largest 1 with a diameter of about 4.4 cm. These findings excluded transplantation criteria and the patient was referred to our center. After appropriate preoperative studies, the patient underwent a major liver resection (trisegmentectomy) after side-to-side PCS by interposition of an iliac vein graft from a cadaveric donor. The patient overcame the worsened severity of cirrhosis. After 6 months of follow-up, he developed 2 other HCC nodules. He was then included on the waiting list at our center, undergoing OLT from a cadaveric donor at 8 months after salvage treatment. At 36 months after OLT, he is alive and free from HCC recurrence. Associating a partial side-to-side PCS with hepatic resection may represent a potential salvage therapy for patients with decompensated cirrhosis and HCC progression beyond listing criteria for OLT.

Hypoxic hepatitis - epidemiology, pathophysiology and clinical management

Hypoxic hepatitis (HH), also known as ischemic hepatitis or shock liver, is characterized by centrilobular liver cell necrosis and sharply increasing serum aminotransferase levels in a clinical setting of cardiac, circulatory or respiratory failure. Nowadays it is recognized as the most frequent cause of acute liver injury with a reported prevalence of up to 10% in the intensive care unit. Patients with HH and vasopressor therapy have a significantly increased mortality risk in the medical intensive care unit population. The main underlying conditions contributing to HH are low cardiac output and septic shock, although a multifactorial etiology is found in the majority of patients. HH causes several complications such as spontaneous hypoglycemia, respiratory insufficiency due to the hepatopulmonary syndrome, and hyperammonemia. HH reverses after successful treatment of the basic HH-causing disease. No specific therapies improving the hepatic function in patients with HH are currently established. Early recognition of HH and its underlying diseases and subsequent initiation of therapy is of central prognostic importance. The purpose of this review is to provide an update on the epidemiology, pathophysiology, and diagnostic and therapeutic options of HH.

The use of beta-adrenergic drugs improves hepatic oxygen metabolism in cirrhotic patients undergoing liver resection

BACKGROUND & AIMS

Hepatic resection is associated with hemodynamic and oxygen metabolism disturbances of the residual liver resulting from liver regeneration. In underlying liver disease, the remnant liver responds inadequately to increased energy demands leading to a less efficient recovery process. The aim of this study was to assess the effect of vasoactive drugs on hepatic oxygen metabolism and hemodynamics in cirrhotic patients that have undergone liver resection.

METHODS

Thirty patients were randomly allocated to receive peri-operatively low doses (4 microg/kg/min) of dopamine (DaG, n=10), dobutamine (DbG, n=10) or saline (CG, n=10). Hepatic hemodynamics, hepatic oxygen metabolism and lactate uptakes were evaluated before drug administration and at the time of abdominal closure. Post-operative liver function and outcome were recorded.

RESULTS

The peri-operative use of vasoactive drugs preserved total hepatic blood flow and hepatic compliance, even increasing in patients who received Db, whereas those parameters decreased in CG after liver resection. At this time, oxygen delivery and consumption decreased in CG patients, but were unchanged when vasoactive drugs were used. In all groups, lactate uptake decreased sharply and only DbG showed positive lactate extraction capacity. The peak of post-operative bilirubin, which resumed baseline values more quickly in DbG, inversely correlated with intra-operative hepatic compliance and hepatic oxygen extraction.

CONCLUSION

Low doses of vasoactive drugs, especially dobutamine, improved hepatic oxygen supply and uptake preserving immediate function of the remnant cirrhotic liver.

Adenosine restores the hepatic artery buffer response and improves survival in a porcine model of small-for-size syndrome

The aim of the study is to define the role of the HABR in the pathophysiology of the SFS liver graft and to demonstrate that restoration of hepatic artery flow (HAF) has a significant impact on outcome and improves survival. Nine pigs received partial liver allografts of 60% liver volume, Group 1; 8 animals received 20% LV grafts, Group 2; 9 animals received 20% LV grafts with adenosine infusion, Group 3. HAF and portal vein flow (PVF) were recorded at 10 min, 60 min and 90 min post reperfusion, on POD 3 and POD 7 in Group 1, and daily in Group 2 and 3 up to POD 14. Baseline HAF and PVF (ml/100 g/min) were 29 +/- 12 (mean +/- SD) and 74 +/- 8 respectively, with 28% of total liver blood flow (TLBF) from the HA and 72% from the PV. PVF peaked at 10 mins in all groups, increasing by a factor of 3.8 in the 20% group compared to an increase of 1.9 in the 60% group. By POD 7-14 PVF rates approached baseline values in all groups. The HABR was intact immediately following reperfusion in all groups with a reciprocal decrease in HAF corresponding to the peak PVF at 10 min. However in the 20% group HAF decreased to 12 +/- 8 ml/100 g/min at 90 min and remained low out to POD 7-14 despite restoration of normal PVF rates. Histopathology confirmed evidence of HA vasospasm and its consequences, cholestasis, centrilobular necrosis and biliary ischemia in Group 2. HA infusion of adenosine significantly improved HAF (p < .0001), reversed pathological changes and significantly improved survival (p = .05). An impaired HABR is important in the pathophysiology of the SFSS. Reversal of the vasospasm significantly improves outcome.

Fetal superior mesenteric artery: longitudinal reference ranges and evidence of regulatory link to portal liver circulation

OBJECTIVE

To establish longitudinal reference ranges for the fetal superior mesenteric artery (SMA) flow velocity and pulsatility index (PI(SMA)). Also to examine the hemodynamic relationship to venous liver perfusion and umbilical flow distribution in the liver, to other splanchnic arteries, and more generally to the middle cerebral and umbilical artery.

METHODS

Prospective longitudinal study of 161 low-risk pregnancies using Doppler recordings including the SMA, repeated on 3-5 occasions at 3-5 weekly intervals. Umbilical venous flow was estimated, blood velocity in the shunt ductus venosus represented umbilico-caval (i.e. porto-caval) pressure gradient, and left portal vein blood velocity represented umbilical distribution within the liver. The correlation between PI(SMA) and the splenic and hepatic artery PI were analysed (PI(SA) and PI(HA)), and the association to middle cerebral and umbilical artery PI (PI(MCA) and PI(UA)) assessed.

RESULTS

Reference ranges for the SMA for gestational weeks 21-39 were based on 589 observations. Low impedance in the SMA (i.e. low PI(SMA)) was associated with low umbilical flow and porto-caval pressure gradient (i.e. <10th centile), and high distribution of umbilical flow to the right lobe (i.e. left portal vein blood velocity >90th centile). PI(SMA) correlated weakly with PI(SA) and PI(HA) (r=0.30, 95%CI 0.22-0.37, and r=0.39, 95%CI 0.27-0.51, respectively). PI(SMA) was positively associated with PI(MCA) and PI(UA).

CONCLUSION

We have provided longitudinal reference ranges for fetal SMA flow velocity and PI, and shown that the SMA, which perfuses the fetal gut, is also involved in the regulation of the liver perfusion.

[Cholestasis and liver dysfunction in critical care patients]

Cornerstones of the diagnostic investigations of disturbances in liver function are analysis and sophisticated evaluation of serum liver enzymes, bilirubin and ammonia. Coagulation factors, serum albumin and cholinesterase levels are indicators of the hepatic metabolic capacity. Dynamic assessment of complex liver functions allows quantification of the hepatic metabolic activity and excretory function. Imaging techniques permit visualization of the size and texture of the liver, the vascular supply and perfusion as well as an assessment of the gall bladder and the extra-hepatic and intra-hepatic bile ducts. Manifold causes for cholestasis and/or liver dysfunction are known, such as ventilation with high pressure, total parenteral nutrition, shock, hypoxia and certain drugs. Obstructive cholestasis requires reconstitution of bile duct drainage, while non-obstructive cholestasis primarily requires treatment of the causative disease. The symptomatic therapy of liver insufficiency is rarely possible via direct treatment of the cause, but mostly requires specific management of secondary organ dysfunctions related to hepatic dysfunction including circulatory failure, hepatorenal syndrome and hepatic encephalopathy. In rare cases a temporary liver surrogate is necessary. The molecular absorbent recirculating system (MARS), a form of extracorporeal albumin dialysis, is introduced as a modality for the treatment of liver failure.

Vasopressin decreases portal vein pressure and flow in the native liver during liver transplantation

Vasodilation due to impaired vascular tone is common in liver failure. Vasoconstrictor drugs are almost always required during the anhepatic phase of a liver transplant to maintain blood pressure unless venovenous bypass is employed. Arginine-vasopressin can be used as a vasoconstrictor instead of or in addition to norepinephrine for this purpose, but the effect of vasopressin on the portal vein pressure and flow in this setting is unknown. Portal vein pressure, portal vein blood flow, hemodynamic variables, and plasma vasopressin levels were measured in 16 patients during liver transplantation after ligation of the hepatic artery before and after a vasopressin infusion of 3.8 +/- 1.1 units/hour. Measurements were performed on the native liver prior to caval clamping. After vasopressin infusion, the portal vein pressure decreased significantly from 24.0 +/- 6.5 to 21.5 +/- 7.4 mm Hg [mean +/- standard deviation (SD), P = 0.006]. The portal vein blood flow also decreased (from 1.01 +/- 0.53 to 0.76 +/- 0.53 L/minute, mean +/- SD, P < 0.0001), as did the portal vein blood flow to cardiac output ratio (from 0.14 +/- 0.06 to 0.10 +/- 0.07, mean +/- SD, P < 0.0001). In conclusion, vasopressin significantly decreased portal vein pressure and flow of the native liver without decreasing cardiac output or intestinal perfusion in patients undergoing liver transplantations.

Fetal celiac and splenic artery flow velocity and pulsatility index: longitudinal reference ranges and evidence for vasodilation at a low portocaval pressure gradient

OBJECTIVES

To establish longitudinal reference ranges for the fetal celiac and splenic arteries flow velocity and pulsatility index (PI), and to determine their hemodynamic relationship to venous liver perfusion and distribution and to other essential arteries.

METHODS

This was a prospective longitudinal study of 161 low-risk pregnancies. Doppler recordings of the celiac and splenic arteries were made on three to five occasions at 3-5-week intervals to establish reference ranges for blood velocity and PI measurements. Peak systolic velocity in the ductus venosus, a shunt between the umbilical and inferior caval veins, was used to represent the umbilicocaval (i.e. portocaval) pressure gradient, and the left portal vein blood velocity represented the umbilical distribution to the right liver lobe. The correlations between the celiac, splenic and hepatic arteries were determined, and their association with the middle cerebral and umbilical artery PIs (MCA-PI and UA-PI) was assessed.

RESULTS

Longitudinal reference ranges for the fetal celiac and splenic arteries were established based on 510 and 521 observations, respectively, during gestational weeks 21-39. Terms for calculating conditional reference ranges to be used for repeat observations are provided. Celiac and splenic artery PIs were low when portocaval pressure and umbilical supply to the right lobe were low (P < 0.0001). Their peak systolic velocity and PI were correlated (r = 0.7 (95% CI, 0.6-0.8) and r = 0.5 (95% CI, 0.3-0.6), respectively), while the PI of the hepatic artery correlated weakly with those of the celiac and splenic arteries. They were positively associated with the MCA-PI and UA-PI (P < 0.0001).

CONCLUSION

We provide longitudinal reference ranges for the fetal celiac and splenic arteries Doppler measurements and show that they are involved in maintaining portal liver perfusion independently from the hepatic artery.

Hepatic artery hemodynamics suggest operation of a buffer response in the human fetus

After birth, the hepatic artery buffer response helps to maintain liver perfusion. Here, the authors establish a Doppler technique to measure fetal hepatic artery flow velocity and test the hypothesis that the buffer response also operates prenatally. Women with low-risk pregnancies were recruited to a longitudinal study (N = 161). Measurement techniques and reference ranges for hepatic artery velocities and pulsatility index (PI) were established. Ductus venosus peak velocity (V(DVps)) represented the portocaval pressure gradient, and umbilical venous flow (Q(UV)) represented portal flow. Reference ranges were established for the more accessible left hepatic artery branch. Hepatic artery PI was lower in fetuses with V(DVps) <10th centile (P < .05) and in those with Q(UV) <10th centile ( P < .0001). Conversely, hepatic artery PI was higher in those with Q(UV) >90th centile (P < .0001). The authors establish a method for measuring fetal hepatic arterial blood velocity, provide reference ranges, and show that the hepatic artery buffer response operates prenatally.

Effects of diffuse fatty infiltration of the liver on portal vein flow hemodynamics

PURPOSE

To investigate the effects of various degrees of diffuse fatty infiltration of the liver on portal vein blood flow with Doppler sonography.

METHODS

One hundred forty subjects were examined with color and spectral Doppler sonography. The subjects were divided into 4 groups of 35 subjects each according to the degree (normal, grade 1, grade 2 and grade 3) of hepatic fatty infiltration assessed on gray-scale images. The portal vein pulsatility index (VPI) and time-averaged mean flow velocity (MFV) were calculated for each subject. VPI was calculated as (peak maximum velocity - peak minimum velocity) / peak maximum velocity.

RESULTS

VPI and MFV values were, respectively, 0.32 +/- 0.06 and 16.8 +/- 2.6 cm/second in the normal group, 0.27 +/- 0.07 and 14.2 +/- 2.2 cm/second in the group with grade 1 fatty infiltration, 0.22 +/- 0.06 and 12.2 +/- 1.8 cm/second in the group with grade 2 fatty infiltration, and 0.18 +/- 0.04 and 10.8 +/- 1.5 cm/second in the group with grade 3 fatty infiltration. There was a negative inverse correlation between the grade of fatty infiltration and both VPI (f = 55.3, p < 0.001) and MFV (f = 43.9, p < 0.001).

CONCLUSION

The pulsatility index and mean velocity of the portal vein blood flow decrease as the severity of fatty infiltration increases.

Effects of low abdominal blood flow and dobutamine on blood flow distribution and on the hepatic arterial buffer response in anaesthetized pigs

Low cardiac output impairs the hepatic arterial buffer response (HABR). Whether this is due to low abdominal blood flow per se is not known. Dobutamine is commonly used to increase cardiac output, and it may further modify hepatosplanchnic and renal vasoregulation. We assessed the effects of isolated abdominal aortic blood flow changes and dobutamine on hepatosplanchnic and renal blood flow. Twenty-five anesthetized pigs with an abdominal aorto-aortic shunt were randomized to 2 control groups [zero (n = 6) and minimal (n = 6) shunt flow], and 2 groups with 50% reduction of abdominal blood flow and either subsequent increased abdominal blood flow by shunt reduction (n = 6) or dobutamine infusion at 5 and 10 microg kg(-1) min(-1) with constant shunt flow (n = 7). Regional (ultrasound) and local (laser Doppler) intra-abdominal blood flows were measured. The HABR was assessed during acute portal vein occlusion. Sustained low abdominal blood flow, by means of shunt activation, decreased liver, gut, and kidney blood flow similarly and reduced local microcirculatory blood flow in the jejunum. Shunt flow reduction partially restored regional blood flows but not jejunal microcirculatory blood flow. Low-but not high-dose dobutamine increased gut and celiac trunk flow whereas hepatic artery and renal blood flows remained unchanged. Neither intervention altered local blood flows. The HABR was not abolished during sustained low abdominal blood flow despite substantially reduced hepatic arterial blood flow and was not modified by dobutamine. Low-but not high-dose dobutamine redistributes blood flow toward the gut and celiac trunk. The jejunal microcirculatory flow, once impaired, is difficult to restore.

Essential hypertension and chronic viral hepatitis

OBJECTIVE

Both arterial hypertension and chronic hepatitis are common disorders. The relationship between arterial pressure and liver cirrhosis has been extensively studied, but no studies are available in chronic hepatitis (CH). Recently, a few studies have reported that treatment with angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin-receptor blockers (ARBs), commonly used in arterial hypertension, reduce hepatic fibrosis in patients with viral CH and in nonalcoholic steatohepatitis. This study was aimed at comparing the evolution of post-viral CH in patients with/without concomitant essential hypertension.

METHODS

Two sets of observations were carried out: (a) a cross-sectional cohort study of 95 patients with viral CH, to compare the severity of histological and biochemical data at diagnosis, in relation to pharmacologically treated essential hypertension, and (b) a retrospective study with the observation of 254 patients with CH of viral etiology, followed up from 2 to 20 years, to establish the natural history of viral CH in relation to treated essential hypertension.

RESULTS

In the cross-sectional analysis, patients with treated hypertension had a significantly older age at diagnosis of CH (51.4 +/- 8.4 years vs. 46.2 +/- 12.2 in normotensive; P < 0.001) and histological evidence of less severe necro-inflammatory liver damage. ALT levels were also lower (109.8 +/- 62.5 U/L vs. 166.0+/-169.5 in normotensive; P < 0.001) as were endothelin-1 levels (0.74 +/- 0.97 vs. 1.77 +/- 1.51 fmol/mL; P < 0.001). The retrospective study confirmed an older age at diagnosis in patients with treated hypertension (48.7 +/- 9.8 vs. 41.9 +/- 11.8 years; P < 0.001) and lower death rates (2.2% vs. 11%; P < 0.05).

CONCLUSIONS

The evolution of post-viral CH seems to be less severe in subjects with essential hypertension, possibly in relation to treatment with antihypertensive drugs.

Contribution of hepatic adenosine A1 receptors to renal dysfunction associated with acute liver injury in rats

Acute liver injury is associated with renal insufficiency, whose mechanism may be related to activation of the hepatorenal reflex. We previously showed that intrahepatic adenosine is involved in activation of the hepatorenal reflex to restrict urine production in both healthy rats and in rats with cirrhosis. The aim of the present study was to test the hypothesis that activation of intrahepatic adenosine receptors is involved in the pathogenesis of the renal insufficiency seen in acute liver injury. Acute liver injury was induced by intraperitoneal injection of thioacetamide (TAA, 500 mg/kg) in rats. The animals were instrumented 24 hours later to monitor systemic, hepatic, and renal circulation and urine production. Severe liver injury developed following TAA insult, which was associated with renal insufficiency, as demonstrated by decreased (approximately 25%) renal arterial blood flow, a lower (approximately 30%) glomerular filtration rate, and decreased urine production. Further, the increase in urine production following volume expansion challenge was inhibited. Intraportal, but not intravenous, administration of a nonselective adenosine receptor antagonist, 8-phenyltheophylline, improved urine production. To specify receptor subtype, the effects of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, an adenosine A(1) receptor antagonist) and 3,7-dimethyl-1-propargylxanthine (DMPX, an adenosine A(2) receptor antagonist) were compared. Intraportal but not intravenous administration of DPCPX greatly improved impaired renal function induced by acute liver injury, and this beneficial effect was blunted in rats with liver denervation. In contrast, neither intraportal nor intravenous administration of DMPX showed significant improvement in renal function. In conclusion, an activated hepatorenal reflex, triggered by intrahepatic adenosine A(1) receptors, contributed to the pathogenesis of the water and sodium retention associated with acute liver injury.

Hypoxic liver injury

Hypoxic liver injury is defined as a massive, but transient, increase in serum transaminase levels due to an imbalance between hepatic oxygen supply and demand in the absence of other acute causes of liver damage. It typically occurs in elderly individuals with right-sided congestive heart failure and low cardiac output. Precipitating factors include arrhythmias or pulmonary edema. Symptoms include weakness, shortness of breath, and right upper quadrant pain. Less commonly, hypoxic liver injury is seen in patients with severe hypoxemia or septic shock. Characteristically, the transaminase level is elevated 20-fold but normalizes rapidly over several days. Imaging studies reveal hypoechoic or hypodense lesions that resolve completely with reversal of the initiating event. Treatment and prognosis depend on the underlyIng disease.

Portal and umbilical venous blood supply to the liver in the human fetus near term

OBJECTIVES

To determine the contribution of the umbilical (UV) and portal (PV) veins to blood supply to the human fetal liver in a low-risk population near term, and to assess the distribution between the left and right lobes.

METHODS

In 91 low-risk pregnancies with normally grown fetuses at 36 weeks of gestation we measured the distribution of blood in the UV and PV to the right and left hepatic lobes using ultrasound imaging and Doppler techniques.

RESULTS

The median (10(th), 90(th) centile) total UV return was 205 (127, 294) mL/min, of which 25% (13, 47%) was shunted through the ductus venosus, 55% (35, 66%) was distributed to the left hepatic lobe, and 20% (11, 30%) was distributed to the right hepatic lobe. While the left lobe was supplied exclusively by the UV, the right lobe received 50% (20, 70%; 37 (16, 65) mL/min) of its venous blood supply from the PV. The total venous blood supply to the liver parenchyma was 185 (114, 277) mL/min; 21% (8, 34%) came from the PV supply to the right lobe and the remainder came from the UV supply to both lobes.

CONCLUSIONS

The venous supply to the left lobe is from nutrient-rich UV blood; for the right lobe, half is from UV blood and half from nutrient-poor PV blood. This watershed between the portal and umbilical venous flows to the fetal liver suggests a corresponding functional dichotomy; this may be modified by hemodynamic influences, with long-term consequences.

Opposite effects of prostacyclin on hepatic blood flow and oxygen consumption after burn and sepsis

BACKGROUND

Burn and sepsis are associated with hepatic ischemia and reperfusion injury. This study examines the hypothesis that postburn treatment with the vasodilator prostacyclin would be beneficial for hepatic perfusion and oxygenation.

METHODS

Female pigs (n = 18, 20-25 kg) underwent laparotomy, during which ultrasonic flow probes were placed on the portal vein and the common hepatic artery. Catheters were inserted in the superior mesenteric and left hepatic veins. After 5 days, all animals were anesthetized and 12 of them received 40% total body surface area third-degree burn; 100 microg/kg Escherichia coli lipopolysaccharide (LPS) was intravenously administered 18 hours postburn. Burned animals were randomized to receive a constant infusion of iloprost (20 ng/kg per minute) or an equivalent amount of carrier solution (normal saline). All animals were studied for 42 hours.

RESULTS

Burn caused a 2.5-fold increase in hepatic arterial vascular resistance (HAVR) and a 39% decrease in hepatic arterial blood flow (HABF). Postburn administration of iloprost did not improve the hepatic arterial hemodynamics (1.8-fold increase in HAVR and 38% decrease in HABF). Post-LPS, HABF was significantly reduced to 22% of baseline and HAVR was 15-fold increased (P < 0.05 vs. baseline, ANOVA). In contrast, iloprost-treated animals did not show hepatic arterial vasoconstriction, as both HABF and HAVR remained baseline values during the endotoxic phase (P < 0.05 vs. nontreated group, ANOVA). Postburn iloprost treatment yielded a significant improvement in post-LPS portal venous blood flow (PVBF, 79% of baseline vs. 45% of baseline in nontreated animals, P < 0.05, ANOVA). Portal venous pressure showed 16% and 56% increases after burn and endotoxin, respectively. Portal hypertension did not occur in iloprost-treated animals, as portal venous pressure remained within baseline range (P < 0.05 vs. nontreated group, ANOVA). Burn and endotoxemia resulted in a significant decrease of hepatic oxygen delivery (hDO2, 63% and 12% of baseline, respectively) and hepatic oxygen consumption (hVO2, 61% and 21% of baseline, respectively). Only during the postburn endotoxic phase, iloprost improved hDO2 and hVO2 (140% and 79%, respectively; P < 0.05 vs. nontreated group, ANOVA).

CONCLUSIONS

Postburn prostacyclin treatment appears to have no beneficial effects on hepatic perfusion early postburn. However, during the late postburn endotoxic phase, prostacyclin seems to significantly improve hepatic total blood flow and oxygenation. In addition, prostacyclin treatment attenuated burn- and endotoxin-induced portal hypertension.

Splanchnic blood flow in low-flow states

IMPLICATIONS

Insufficient splanchnic blood flow in critically ill patients is the result of a multitude of different diseases, treatment modalities and their interplay, and is associated with increased morbidity and mortality. A combination of diminished and heterogeneous mesenteric blood flow, impaired or exhausted regulatory mechanisms and adverse drug effects may coexist with normal systemic hemodynamics.