Hemodynamic changes in patients with portal venous obstruction

The metabolism and bioavailability of morphine in patients with severe liver cirrhosis

1. The oral and intravenous kinetics of morphine were investigated in seven cirrhotic patients with a history of encephalopathy. The plasma concentrations of morphine and its metabolites morphine-3 (M3G) and morphine-6 (M6G) were measured by h.p.l.c. 2. The mean terminal elimination half-life of morphine was 4.2 h (95% CI 3.6-4.8) the mean volume of distribution was 4.1 l kg-1 (95% CI 2.9-5.4) and the mean plasma clearance was 11.4 ml min-1 kg-1 (95% CI 8.1-14.7). The mean oral bioavailability was 101% (95% CI 56-147). 3. The plasma clearance of morphine was significantly lower, its terminal elimination half-life longer and its oral bioavailability greater in the cirrhotic patients compared with patients with normal liver function. The metabolic ratio M3G/morphine was significantly lower in the cirrhotic patients than in control subjects after oral dosing, but did not differ after intravenous dosing. 4. The average urinary recoveries of morphine plus M3G and M6G were 49.9% after i.v. and 57.7% after oral administration. There were no statistically significant differences in the urinary recovery between the two routes of administration or between the cirrhotic patients and controls. 5. Specific changes in the EEG pattern could not be detected after intravenous dosage. 6. The metabolism of morphine is impaired significantly in patients with severe cirrhosis. Clinically important findings were a high oral bioavailability and a long elimination half-life. These findings call for cautious dosing of oral and intravenous morphine in patients with severe end stage liver disease.

Hyperkinetic circulatory syndrome in patients with presinusoidal portal hypertension. Effect of propranolol

This study evaluates systemic and splanchnic haemodynamics and the effect of propranolol in 15 patients with presinusoidal portal hypertension (portal vein obstruction, n = 11; schistosomiasis, n = 4). These patients exhibited a hyperkinetic circulatory syndrome characterized by high cardiac index (4.4 +/- 1.61.min-1.m-2, mean +/- S.D.) and by low systemic vascular resistance despite normal liver function and sinusoidal pressure. Hepatic blood flow was decreased in half of the patients with portal vein obstruction. Azygos blood flow, an estimate of superior portal-systemic collateral circulation, was markedly increased in all patients (0.46 +/- 0.19 l/min, upper limit of normal: 0.19 l/min). Therefore, in these patients with normal hepatic venous pressure gradient, azygos blood flow measurement provides an index of splanchnic haemodynamic changes. Propranolol administration (15 mg, i.v.) reduced the hyperkinetic circulatory syndrome, with a significant decrease in heart rate (-17 +/- 6%), cardiac index (-25 +/- 12%) and azygos blood flow (-40 +/- 26%) and a significant increase in systemic vascular resistance (+40 +/- 40%). These results suggest that the hyperkinetic circulatory syndrome observed in these patients, could be related to an increase in beta-adrenergic activity. The decrease in azygos blood flow, after propranolol administration, was significantly correlated (r = 0.94) with the increase in right atrial pressure. This finding suggests that propranolol may act through an increase in portal-systemic collateral venous tone. These haemodynamic results justify, in patients with presinusoidal portal hypertension, clinical trials investigating the beneficial effect of beta-blockers on gastrointestinal bleeding caused by portal hypertension.

Diet-induced thermogenesis in patients with liver cirrhosis

Diet-induced thermogenesis after ingestion of a mixed meal was investigated in eight patients with documented liver cirrhosis and in eight age- and sex-matched healthy controls. Respiratory gas exchange was measured continuously for one hour in the basal state and for three hours after ingestion of a mixed liquid meal, consisting of 17% kJ protein, 28% kJ lipids and 55% kJ carbohydrates and dispensed to correspond to 60% of the individually computed energy expenditure. Arterial substrate and hormone concentrations were determined before and at timed intervals for three hours after the meal. Urine was collected for determination of nitrogen excretion. The patients' oxygen uptake, energy expenditure and respiratory quotient were similar to those of the controls in the basal state. After the meal, pulmonary oxygen uptake and energy expenditure rose markedly in both groups during the first hour and were subsequently stable. The average increase in oxygen uptake above basal during the whole study period was 21.2 +/- 1.8% and 22.3 +/- 1.2% (NS) in patients and controls, respectively. The corresponding increase in energy expenditure was 24.8 +/- 2.0% in the patients and 24.9 +/- 1.4% in the controls (NS). The respiratory quotient was elevated throughout the postprandial period in both groups but the quotient was significantly higher in the patients (P less than 0.05-0.001), suggesting a greater proportion of carbohydrate oxidation. The basal arterial concentrations of insulin and glucagon were significantly higher in the patients. After the meal the insulin level increased 10- to 20-fold in both groups. Glucose concentration rose significantly in both groups to a maximum of 8.82 +/- 1.00 and 8.03 +/- 0.95 mmol/l in patients and controls, respectively, at 60 min after the meal. This was accompanied by a fall in the levels of glycerol and ketone bodies in both groups, indicating decreased lipolysis. It is concluded that both the basal energy expenditure and the thermogenic response to a mixed meal are similar in patients with liver cirrhosis and in healthy controls. The patients' carbohydrate oxidation rose to a greater extent after the meal, probably as a consequence of excessive increases in insulin concentration, demonstrating that insulin resistance in these patients may be compensated for by postprandial hyperinsulinaemia.

Pathophysiology and epidemiology of portal hypertension

Changes in portal pressure are regulated by changes in hepatic vascular resistance, which is normally under neurohumoral control, and portal tributary blood flow. Two theories on the pathophysiology of portal hypertension have been proposed: the 'backward flow' theory, in which portal hypertension is attributable to increased resistance to portal venous flow, and the 'forward flow' theory, in which increased splanchnic blood flow maintains portal hypertension despite extreme portal-systemic shunting. The sinusoidal abnormalities caused by an accumulation of collagen in the perisinusoidal space of Disse may induce increased resistance to blood flow in various pathological conditions of the liver. Non-cirrhotic portal hypertension results from not only relatively uncommon disorders prevalent mainly in Asia and tropical countries, but also from acute and chronic phases of relatively common liver diseases. Systemic hyperdynamic circulation, characterised by an increased cardiac output and a reduced peripheral vascular resistance, and splanchnic hyperaemia may develop as consequences of portal hypertension. Although the mechanisms of these changes are not clearly understood, portal-systemic shunting as well as some vasoactive substances, including prostaglandins, may be involved. The erosive and eruptive mechanisms are the two potential explanations for variceal bleeding. In the latter, pressure should not be viewed in isolation and other additive factors such as variceal size may be involved. Several new techniques of measuring variceal pressure and blood flow may improve understanding of the actual pathophysiology of variceal bleeding. Renal haemodynamic alterations secondary to the systemic circulatory changes produced by portal hypertension may occur. The geographical pattern of prevalence in disorders associated with portal hypertension is briefly described in this paper.

Haemodynamic responses to 1.25 and 2 mg of terlipressin intravenously in man

The systemic and hepatic haemodynamic effects following terlipressin (Glypressin) administration were studied. Bolus intravenous injections of 1.25 and 2 mg significantly decreased wedged hepatic vein pressure gradient by 29% and 31%, respectively. With each dose there was a small increase in mean arterial blood pressure but after 1.25 mg of terlipressin, estimated hepatic blood flow fell by only 11% (not significant) compared to 24% after 2 mg, while the cardiac index fell by 12% compared to 29%. The adverse haemodynamic effects of terlipressin were diminished by a decrease in dosage, without any alteration in the beneficial effect of the drug upon portal pressure. Whether the smaller dose will be effective in arresting variceal haemorrhage remains to be determined.

Hyposensitivity to vasopressin in a hemorrhaged-transfused rat model of portal hypertension

This study was designed to evaluate the hemodynamic response to vasopressin infusion during hemorrhage and blood transfusion in a rat model of portal hypertension. Portal pressure, arterial pressure, and regional and systemic blood flows were measured in a rat model of portal hypertension receiving placebo or vasopressin infusion. Effects of the drugs were compared in control rats and rats subjected to hemorrhage and blood transfusion. In a stable portal hypertensive rat group (no hemorrhage or transfusion) a standard vasopressin dose, 2.5 mU X kg-1 X min-1, resulted in a significantly lower portal pressure (11.5 +/- 0.7 vs. 14.4 +/- 0.6 mmHg) with a concomitantly lower portal venous inflow (8.5 +/- 0.3 vs. 11.1 +/- 0.6 ml X min-1 X 100 g body wt-1) when compared with rats receiving placebo. These findings are in contrast to the effects obtained with the same dose of vasopressin given during blood transfusion to hemorrhaged portal hypertensive rats. The standard dose of vasopressin had no effect on any of the splanchnic or systemic circulatory parameters. Only when a dose of vasopressin 10 times larger was used in the hemorrhaged-transfused animals were hemodynamic effects noted. A significant decrease in portal flow and pressure was noted. These findings suggest that vasopressin given during hemorrhage may be less effective than when given during a stable state. Larger doses of vasopressin may be needed during hemorrhage to produce the same effect as seen during a controlled stable state. Caution should be used in extrapolating the results of pharmacologic studies in stable portal-hypertensive models to hypovolemic states in humans.

Portal hemodynamics in idiopathic portal hypertension (Banti's syndrome). Comparison with chronic persistent hepatitis and normal subjects

A comparative study of portal hemodynamics was made in 17 patients with idiopathic portal hypertension, 5 patients with chronic persistent hepatitis having no portal hypertension, and 21 healthy adults who served as the control for certain measurements. Venous pressures were measured by portal and hepatic vein catheterizations, blood flow by the pulsed Doppler flowmeter, organ volume by computed tomography, and intrahepatic shunt index by 99mTc-macroaggregated albumin instilled in the portal vein. The patients with idiopathic portal hypertension were divided into two groups: group A (n = 8) and group B (n = 9), consisting of those who respectively had portal venous flow per liver volume above and below the mean + 2 SD of healthy adults. In group A, portal vein pressure was moderately elevated, portal venous flow was significantly increased compared with the control, and portal vascular resistance was not much altered. In group B, portal vein pressure was markedly elevated above that of control, portal venous flow was comparable, and portal vascular resistance was significantly elevated. Splenic venous flow measured in the splenic vein between the left and short gastric veins was markedly increased in groups A and B, the increase being greater in the former. It was concluded that in some patients with idiopathic portal hypertension, increased portal venous flow, partly a result of increased splenic venous flow secondary to splenomegaly of an undetermined process, is the main contributor initially to the elevation of portal vein pressure; in others, possibly later, increased portal vascular resistance plays an important role.

Renal hyperemia in portal hypertension is not mediated by gastrointestinal peptides

The objectives of this study were to characterize the time course of development of the renal hyperemia induced by chronic portal vein stenosis (PVS) in the rat, and to assess the possibility that vasoactive blood-borne gastrointestinal peptides mediate the renal hyperemia in established portal hypertension. Blood flow to the kidneys was measured with radioactive microspheres over a ten day time course. On day 2, no difference in renal blood flow (RBF) was observed in PVS rats as compared with controls. However, by day 4, RBF significantly increased by 35% in PVS vs. control animals. On day 6, the renal hyperemia in PVS rats reached a maximal value that was 42% higher than controls. A steady state hyperemia (approximately 40%) was maintained thereafter. Radioimmunoassay of plasma from control and established portal hypertensive rats (10 days samples) revealed that vasoactive intestinal polypeptide, substance P, cholecystokinin, gastrin, neurotensin, pancreatic polypeptide, beta-endorphin and peptide histidine-isoleucine amide are not elevated in arterial plasma of portal hypertensive rats. These data suggest that the renal hyperemia induced by chronic portal vein stenosis is apparent within 4 days of the onset of a hypertensive state and attains a steady state by day 8. Furthermore, at least eight blood-borne gastrointestinal peptides are not directly involved in the renal hyperemia associated with chronic portal hypertension.

Hepatic siderosis in extrahepatic portal vein obstruction. Role of spontaneous portosystemic shunting?

We report on the observation of a 26-year-old woman with portal vein obstruction, diagnosed at the age of 3, and liver iron overload. Celiac and superior mesenteric angiography showed large and multiple venous collaterals between the portal and caval systems. Liver biopsy demonstrated, on Perl's staining, an important hemosiderin deposition, confirmed by an increased hepatic iron concentration (15.6 mumol/100 mg dry weight). No other histologic abnormality was found. This report suggests that large spontaneous portosystemic shunting may stimulate hepatic iron deposition in an otherwise normal liver. This mechanism could, at least in part, explain the significant hepatic siderosis observed in some cirrhotic patients.

Splanchnic and systemic hemodynamics in portal hypertensive rats during hemorrhage and blood volume restitution

In portal hypertension the hemodynamic events after episodes of bleeding and blood transfusions may have important pathophysiological and therapeutic implications. The present study was designed to evaluate the effect of hemorrhage and blood restitution on splanchnic and systemic hemodynamics in a rat model of portal hypertension induced by portal vein constriction. In 16 portal hypertensive rats, sequential measurements of arterial and portal pressure were obtained during withdrawal and reinfusion of 15 ml X kg-1 body wt of blood. At the completion of the hemorrhage, a decrease of 16.9% +/- 2.6% in arterial pressure and 27.3% +/- 2.2% in portal pressure was observed. After blood reinfusion, arterial pressure returned to baseline values while portal pressure increased by 20.4% +/- 3.2% (p less than 0.01). This increase in portal pressure was not observed in 5 normal rats that were subjected to the same blood volume changes. Hemodynamic studies using a radioactive microsphere technique revealed that the withdrawal of 15 ml X kg-1 body wt of blood is followed by a decrease in portal venous inflow (6.4 +/- 0.4 vs. 10.4 +/- 0.6 ml X min-1 X 100 g-1 body wt in the control group, p less than 0.01). After blood volume restitution, the portal venous inflow returned to control values while the portal-collateral resistance increased significantly (2.06 +/- 0.13 vs. 1.67 +/- 0.07 mmHg X min X ml-1. 100 g, p less than 0.05). These results indicate that during hypovolemia there is a marked reduction in portal pressure because of a reduction in portal venous inflow. Blood volume restitution returns the portal venous inflow to control values. However, the portal pressure increases beyond control values because of an increase in portal-collateral resistance.

Hemodynamic studies in long- and short-term portal hypertensive rats: the relation to systemic glucagon levels

It is not known whether the hyperdynamic state which has been observed in several experimental models and in patients with portal hypertension reflects a temporary phase during the evolution of the portal hypertensive syndrome or is an expression of a permanent steady state. A hemodynamic study was performed in a group of rats with long-standing portal hypertension induced by portal vein constriction performed 6.2 +/- 0.1 months earlier. A group of rats matched by age and weight with short-term (20.7 +/- 0.9 days) portal hypertension and a group of long-term (6.2 +/- 0.1 months) sham-operated rats were used as controls. Cardiac output and regional blood flows were measured using a radioactive microsphere technique. Arterial blood levels of glucagon, a known vasodilator that was implicated in the etiology of the hyperdynamic circulation, were also measured. Portal pressure in long- and short-term portal hypertensive groups (12.3 +/- 0.4 and 13.7 +/- 0.4 mm Hg; not statistically significant) was higher than in the sham group (9.0 +/- 0.3 mm Hg; p less than 0.01). Cardiac output in the long-term portal hypertensive rats was similar to the sham-operated group and lower than in the short-term portal hypertensive group (19.4 +/- 1.0 and 20.6 +/- 1.5 vs. 32.7 +/- 2.0 ml X min-1 X 100 gm body weight-1; p less than 0.01). Portal venous inflow in the long-term portal hypertensive group was also similar to the sham group and lower than in the short-term portal hypertensive group (4.51 +/- 0.36 and 4.58 +/- 0.39 vs. 6.72 +/- 0.48 ml X min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in isoprenaline sensitivity in patients with cirrhosis: evidence of abnormality of the sympathetic nervous activity

Isoprenaline sensitivity and plasma catecholamine concentrations were studied to assess the sympathetic nervous activity in 13 patients with alcoholic cirrhosis and were compared with five controls. In patients with cirrhosis, the dose of isoprenaline required to increase the resting heart rate by 25 beats min-1 (chronotropic dose 25 or CD25) ranged from 2.50 to 34.73 micrograms (median: 4.47 micrograms) and was significantly higher than in controls (range: 0.66 to 2.76 micrograms, median: 1.34 micrograms). In cirrhotic patients, CD25 values were significantly correlated with plasma albumin concentration, resting heart rate and wedged hepatic venous pressure. In patients with cirrhosis, plasma noradrenaline concentrations ranged from 192 to 978 pg ml-1 (median: 444 pg ml-1) and adrenaline concentrations ranged from 5 to 183 pg ml-1 (median: 47 pg ml-1). No correlation was found between noradrenaline or adrenaline concentrations and CD25 values in cirrhotic patients. In conclusion, in patients with cirrhosis, beta-adrenoceptor responsiveness assessed by isoprenaline sensitivity is altered.

Circulatory actions of vasopressin in anaesthetized rats with portal hypertension subjected to haemorrhage

To assess the influence of vasopressin on splanchnic and renal circulatory changes induced by haemorrhage in portal hypertension, we studied 4 groups of 7 rats with chronic portal vein stenosis. Two groups received saline (C and H) and two groups vasopressin, 0.01 IU/kg/min (VP and VP-H). Ten minutes after starting drug infusion, group H and VP-H animals were allowed to bleed from the superior mesenteric vein. Both haemorrhage and vasopressin alone, decreased portal venous tributary blood flow and pressure but their association was not additive (as reflected by comparable bleeding rate in groups H and VP-H). By contrast, vasopressin increased renal perfusion in bleeding and non-bleeding animals whereas haemorrhage alone decreased renal perfusion. These results indicate that the effects of vasopressin on the splanchnic circulation in bleeding anaesthetized animals differ from the effects observed when blood volume is normal. Therefore, in patients with cirrhosis the effects of vasopressin during bleeding might also differ from those observed in patients in stable condition.

Hemodynamic studies in a parabiotic model of portal hypertension

Splanchnic and systemic hemodynamic studies were performed in a rat model of parabiosis and portal hypertension. A portal hypertensive and a normal rat were surgically united side to side. A hyperdynamic circulation, characterized by increased cardiac index (413 +/- 26 vs 318 +/- 23 ml X min-1 X kg-1; p less than 0.05) and portal venous inflow (9.61 +/- 1.29 vs 6.33 +/- 0.36 ml X min-1 X 100 g b.wt-1; p less than 0.05), was found in all the portal hypertensive rats but not in the normal parabiotic partners. These results do not support the existence of a transferable humoral factor mediating the hyperdynamic circulatory state of chronic portal hypertension.

Effects of prostaglandin inhibition on systemic and hepatic hemodynamics in patients with cirrhosis of the liver

The role of prostaglandins in the pathogenesis of the circulatory abnormalities of cirrhosis was investigated by studying the effects of prostaglandin inhibition with indomethacin (50 mg/8 h for 24 h) on the systemic and splanchnic hemodynamics in 13 patients with cirrhosis of the liver. Indomethacin administration significantly reduced cardiac output (from 7.44 +/- 0.7 to 6.78 +/- 0.7 L/min, p less than 0.05) and increased peripheral vascular resistance (from 990 +/- 104 to 1155 +/- 140 dyn X s X cm-5, p less than 0.05). Arterial pressure was not modified. These changes in systemic hemodynamics were associated with a significant reduction in hepatic blood flow (from 1.88 +/- 0.43 to 1.48 +/- 0.3 L/min, p less than 0.05) and with a slight decrease of portal pressure (from 18.8 +/- 1.3 to 17.5 +/- 1.4 mmHg, p less than 0.05). These results suggest that endogenous prostaglandins contribute to the increased cardiac output and diminished vascular resistance observed in cirrhosis of the liver. In addition, by promoting splanchnic vasodilation, prostaglandins may contribute to increased portal pressure in these patients.