Hepatic venous oxygen content in alcoholic cirrhosis and non-cirrhotic alcoholic liver disease

Acid-base disturbance in patients with cirrhosis: relation to hemodynamic dysfunction

PURPOSE

Acid-base disturbances were investigated in patients with cirrhosis in relation to hemodynamic derangement to analyze the hyperventilatory effects and the metabolic compensation.

METHODS

A total of 66 patients with cirrhosis and 44 controls were investigated during a hemodynamic study.

RESULTS

Hyperventilatory hypocapnia was present in all patients with cirrhosis and progressed from Child class A to C (P<0.01). Arterial pH increased significantly from class A to C (P<0.001) and was correlated inversely to the mean arterial blood pressure (r=-0.30, P<0.02), systemic vascular resistance (r=-0.25, P<0.05), indocyanine green clearance (r=-0.37, P<0.005), and serum sodium (r=-0.38, P<0.002). Metabolic compensation was shown by a reduced standard base excess in all patients (P<0.001). Standard base excess contained elements related to changes in serum albumin, water dilution, and effects of unidentified ions (all P<0.001). A significant hepatic component in the acid-base disturbances could not be identified.

CONCLUSION

Hypocapnic alkalosis is related to disease severity and hyperdynamic systemic circulation in patients with cirrhosis. The metabolic compensation includes alterations in serum albumin and water retention that may result in a delicate acid-base balance in these patients.

Hepatic arterial and portal venous oxygen content and extraction in liver cirrhosis

We examined the oxygen content in the hepatic arterial, hepatic venous and portal venous blood to evaluate the oxygen supply to the liver and hepatic oxygen extraction in cirrhosis. The arterial-portal venous difference of the oxygen content was within the normal range in cirrhosis patients, although the oxygen content of the hepatic artery and portal vein was lower than in the control patients. The hepatic venous oxygen content was normal in the cirrhosis patients. The oxygen tension and saturation were always higher in the splenic vein than in the other branches of the portal system. Oxygen was supplied chiefly by the hepatic artery, and arterial oxygen extraction was normal in cirrhosis. In addition, there was no change in arterial extraction during oxygen inhalation by cirrhosis patients. Portal venous oxygen extraction was decreased in cirrhosis and was increased by oxygen inhalation. These findings indicate the autoregulation of hepatic oxygen through a mutual relationship between the hepatic arterial and the portovenous oxygen supply.

Insights into the pathogenesis of alcoholic liver necrosis and fibrosis: status report

The use of the Tsukamoto-French rat model of alcoholic liver disease facilitated pathological, physiological, biochemical and cell biological experiments that examined the validity of some of the existing hypotheses for pathogenesis of alcoholic liver necrosis and fibrosis. Results obtained to date strongly support the contribution of centrilobular hypoxia as a pathogenetic mechanism of alcoholic liver necrosis. The enhanced hepatic lipid peroxidation was not evident at the early stage of ethanol-induced liver necrosis but could be demonstrated at the late stage when the liver damage progressed to liver fibrosis. This suggests that the lipid peroxidation may not be an important mechanism of alcoholic liver necrosis but may be an initiation factor for liver fibrogenesis as recently proposed by others (88). The high-fat diet appears to have promoting effects on both induction of alcoholic liver necrosis and stimulation of liver fibrogenesis. The former may be related to the induction of MEOS by the high-fat diet and consequent centrilobular hypoxia caused by inadequately compensated hepatic overuse of oxygen. The latter can be mediated through sensitization of Ito cells by a high-fat diet. We propose that Kupffer cell-derived TGF beta is, at least in part, responsible for some of phenotypical changes of Ito cells associated with their activation. Our model provides maximal experimental control and induces the discrete stages of alcoholic liver injury that can be reproduced with its pathological evolution telescoped into a short time. Because of these features, replication of the experimental conditions in different laboratories is possible so that results can be validly compared through precise standardization of the experimental protocols. This model requires some training in implantation and maintenance of the gastric catheter. However, the training can be easily attained by anyone who has experience in animal surgery. Another requirement is the initial fund to acquire infusion devices and metabolism cages. Once this equipment is purchased, however, the maintenance cost is low. Even if the initial expenses are included, the cost per animal is relatively inexpensive when compared with the cost involved in the use of larger animals such as baboons or pigs. Since administration of diet and ethanol (or isocaloric glucose solution) is precisely controlled by infusion pumps, this system makes unnecessary the measurement of diet consumption that has to be done daily for each animal with other methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of ethanol induced hepatic injury

Ethanol is hepatotoxic through redox changes produced by the NADH generated in its oxidation via the alcohol dehydrogenase pathway, which in turn affects the metabolism of lipids, carbohydrates, proteins and purines. Ethanol is also oxidized in liver microsomes by an ethanol-inducible cytochrome P-450 (P-450IIE1) which contributes to ethanol metabolism and tolerance, and activates xenobiotics to toxic radicals thereby explaining increased vulnerability of the heavy drinker to industrial solvents, anesthetic agents, commonly prescribed drugs, over-the-counter analgesics, chemical carcinogens and even nutritional factors such as vitamin A. Induction also results in energy wastage and increased production of acetaldehyde. Acetaldehyde, in turn, causes injury through the formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair, and alterations in microtubules, plasma membranes and mitochondria with a striking impairment of oxygen utilization. Acetaldehyde also causes glutathione depletion and lipid peroxidation, and stimulates hepatic collagen synthesis, thereby promoting fibrosis.

Impaired oxygen utilization. A new mechanism for the hepatotoxicity of ethanol in sub-human primates

The role of oxygenation in the pathogenesis of alcoholic liver injury was investigated in six baboons fed alcohol chronically and in six pair-fed controls. All animals fed alcohol developed fatty liver with, in addition, fibrosis in three. No evidence for hypoxia was found, both in the basal state and after ethanol at moderate (30 mM) or high (55 mM) levels, as shown by unchanged or even increased hepatic venous partial pressure of O2 and O2 saturation of hemoglobin in the tissue. In controls, ethanol administration resulted in enhanced O2 consumption (offset by a commitant increase in splanchnic blood flow), whereas in alcohol fed animals, there was no increase. At the moderate ethanol dose, the flow-independent O2 extraction, measured by reflectance spectroscopy on the liver surface, tended to increase in control animals only, whereas a significant decrease was observed after the high ethanol dose in the alcohol-treated baboons. This was associated with a marked shift in the mitochondrial redox level in the alcohol-fed (but not in control) baboons, with striking rises in splanchnic output of glutamic dehydrogenase and acetaldehyde, reflecting mitochondrial injury. Increased acetaldehyde, in turn, may aggravate the mitochondrial damage and exacerbate defective O2 utilization. Thus impaired O2 consumption rather than lack of O2 supply characterizes liver injury produced by high ethanol levels in baboons fed alcohol chronically.

Incomplete compensation of enhanced hepatic oxygen consumption in rats with alcoholic centrilobular liver necrosis

Centrilobular hypoxia mediated by enhanced hepatic consumption of oxygen has been hypothesized to be a factor of pathogenetic importance in ethanol-induced liver injury. In the present study, this hypothesis was tested in a rat model which developed alcoholic centrilobular liver necrosis. Male Wistar rats were infused with high fat diet plus ethanol or isocaloric glucose for 7 weeks, a duration which resulted in induction of balloon cell degeneration, focal necrosis, and inflammation in the centrilobular region of the liver of the ethanol-fed animals. Hepatic blood flow, oxygen consumption and oxygen delivery were determined by the radiolabeled microsphere method and measurement of oxygen content in arterial, portal venous, and hepatic venous blood. Hepatic oxygen consumption was markedly increased by 159% in the ethanol-fed animals compared to that in the controls when results were expressed as relative to body weight. Even after these results were standardized per gram of liver weight, hepatic oxygen consumption was still significantly elevated in the ethanol-fed group, but the magnitude of the elevation was reduced to 70%, due to marked hepatomegaly observed in these animals. There was a concomitant 59% increase in hepatic oxygen delivery in the ethanol-fed rats when expressed per kilogram of body weight, and this effect was attributable entirely to increased portal blood flow. However, the increment of this increase in oxygen delivery was much too small to compensate for the 159% increase in oxygen consumption. In addition, this increase in hepatic oxygen delivery was no longer observable when the results were reexpressed based on the liver weight.(ABSTRACT TRUNCATED AT 250 WORDS)