The effect of mechanically enhancing portal venous inflow on hepatic oxygenation, microcirculation, and function in a rabbit model with extensive hepatic fibrosis.

Enhancing the portal venous blood flow (PVBF) has been shown to reduce portal pressure and intrahepatic vascular resistance and to improve liver function in isolated cirrhotic rodent livers in vitro. The aim of this study was to assess the short-term effect of mechanically pumping the portal inflow on hepatic microcirculation (HM), oxygenation, and function in an animal model of extensive hepatic fibrosis. New Zealand white rabbits underwent laparotomy and exposure of the liver: group 1 (n = 7) were normal controls; group 2 (n = 7) had hepatic fibrosis. Total hepatic blood flow (THBF) and HM was measured along with continuous monitoring of intrahepatic tissue oxygenation using near infrared spectroscopy (NIRS). Baseline hepatic hemodynamics and liver function were measured in both groups. PVBF was then increased by 50% over a 3-hour period in the hepatic fibrosis group using a miniature portal pump designed for human implantation, and the hemodynamics were monitored continuously. Liver function tests were repeated after portal pumping. In comparison with normal controls, animals with hepatic fibrosis had a higher portal pressure (13.0 +/- 3.6 vs. 3.7 +/- 1.4 mm Hg, P <.001, mean +/- SD vs. controls), reduced PVBF (52.4 +/- 24.6 vs. 96.9 +/- 21.1 mL/min, P =.003), and increased portal vascular resistance (P =. 001). THBF and flow in the HM was lower than in controls, and liver function tests were abnormal. After a 3-hour period of enhanced portal flow in animals with hepatic fibrosis, the portal pressure greatly reduced (13.0 +/- 3.6 to 2.5 +/- 1.1 mm Hg, P <.001) as did the intrahepatic portal resistance (0.32 +/- 0.18 to 0.04 +/- 0.03 mm Hg/mL/min, P =.006). Flow in the HM improved (143 +/- 16 to 173 +/- 14 flux units, P =.006) and was associated with improved hepatic tissue oxygenation, tissue oxy-hemoglobin (HbO2) and cytochrome oxidase being increased by 24.4 +/- 7.5 and 5.65 +/- 2.30 micromol/L above the baseline value (P <.001), respectively. A 3-hour period of mechanical portal pumping produced a dramatic improvement in liver function, bilirubin (41.1 +/- 25.9 to 10.0 +/- 5.9 micromol/L, P =. 040), aspartate transaminase (AST) (135.5 +/- 52.3 to 56.3 +/- 19.8 U/L, P =.006) and lactate dehydrogenase (LDH) (2,030.1 +/- 796.3 to 1,309.8 +/- 431.6 IU/L, P =.006; prepumping vs. postpumping, all P <. 050). In conclusion, portal pumping in this rabbit model with extensive hepatic fibrosis improved liver parenchymal perfusion, oxygenation, and function.     

Intrahepatic pressure measurement: not an accurate reflection of portal vein pressure

Previous studies have established the reliability of percutaneous portal venous pressure measurement using a Chiba needle, a procedure requiring fluoroscopic guidance. Intrahepatic pressure has been advocated by some as a simple and safe index of portal venous pressure. The aim of this study was to examine the reliability of intrahepatic pressure measurement and its relationship to portal venous pressure. Fifty patients requiring liver biopsy were included: 29 with cirrhosis (n = 20 micronodular, n = 9 macronodular) and 21 with various hepatic disorders but no cirrhosis. The procedure was performed under fluoroscopic guidance, using a Chiba needle connected to a manometer by a saline-filled catheter. Immediately prior to biopsy, each patient underwent measurement of: (i) 3 to 5 separate intrahepatic pressures, the intraparenchymal site being inferred by the lack of blood or bile return; and (ii) portal and hepatic venous pressures, the intravascular position of the needle being ascertained by the reflux of blood and the vessel identified with injection of contrast. Intrahepatic pressure measurements showed great intraindividual variability (variation coefficient up to 115%). Mean intrahepatic pressure (13.19 +/- 8.32 mm Hg) was similar to portal venous pressure (14.43 +/- 6.10 mm Hg) in the noncirrhotics but significantly lower in the cirrhotics (intrahepatic pressure = 18.34 +/- 8.82 mm Hg, portal venous pressure = 22.52 +/- 9.47 mm Hg; p less than 0.01). The difference between these two parameters exceeded 3 mm Hg in 50% of patients (mean = 9 mm Hg, range = 4 to 19 mm Hg), both in cirrhotics and noncirrhotics.(ABSTRACT TRUNCATED AT 250 WORDS)     

Simvastatin enhances hepatic nitric oxide production and decreases the hepatic vascular tone in patients with cirrhosis

BACKGROUND & AIMS: In cirrhosis, an insufficient release of nitric oxide contributes to increased hepatic resistance and portal pressure and enhances the postprandial increase in portal pressure. We hypothesized that simvastatin, which enhances Akt-dependent endothelial nitric oxide synthase phosphorylation, may increase hepatic nitric oxide release and decrease hepatic resistance in patients with cirrhosis and portal hypertension. METHODS: In protocol 1, 13 patients had measurements of the hepatic venous pressure gradient, hepatic blood flow, mean arterial pressure, cardiac output, and nitric oxide products before and 30 and 60 minutes after 40 mg of simvastatin. In protocol 2, 17 patients were randomized to receive placebo or simvastatin (40 mg) 12 hours and 1 hour before the study. After baseline measurements of the hepatic venous pressure gradient, hepatic blood flow, and nitric oxide products, a standard liquid meal was given, and measurements were repeated at 15, 30, and 45 minutes. RESULTS: In protocol 1, acute simvastatin did not modify the hepatic venous pressure gradient but increased the hepatic blood flow (21% +/- 13% at 30 minutes; P = 0.01) and decreased hepatic sinusoidal resistance by 14% +/- 11% (P = 0.04). Nitric oxide product levels significantly increased in hepatic venous blood (from 31.4 +/- 12.3 nmol. mL(-1) to 35.8 +/- 10.7 nmol. mL(-1); P = 0.04), but not in peripheral blood. Systemic hemodynamics were not modified. In protocol 2, simvastatin pretreatment significantly attenuated the postprandial increase in hepatic venous pressure gradient (mean peak increase, 10% +/- 9% vs. 21% +/- 6% in placebo; P = 0.01). Hepatic blood flow increased similarly in the 2 groups. Hepatic nitric oxide products increased in the simvastatin group but not in the placebo group. CONCLUSIONS: Simvastatin administration increases the hepatosplanchnic output of nitric oxide products and decreases hepatic resistance in patients with cirrhosis.     

Portal hemodynamics during nitroglycerin administration in cirrhotic patients

Nitroglycerin is a potent venous dilator and a mild arterial vasodilator that has been shown to improve the hemodynamic response to vasopressin in portal hypertensive patients and to decrease portal pressure in experimental animals. In order to determine the effect of nitroglycerin on portal venous hemodynamics, we studied 11 patients with alcoholic cirrhosis before and during the administration of sublingual nitroglycerin (0.4 and 0.6 mg). The hepatic venous pressure gradient (which was obtained by subtracting the free hepatic venous pressure from the wedged hepatic venous pressure) decreased from 17.9 +/- 6.5 mm Hg (mean +/- S.D.) to 15.1 +/- 5.1 mm Hg (p less than 0.02) at the peak of the effect, which occurred from 2 to 12 min after nitroglycerin administration. The mean arterial pressure was reduced from 96 +/- 10 mm Hg to a peak decrease of 76 +/- 18 mmHg (p less than 0.001). The peak change in the hepatic venous pressure gradient induced by nitroglycerin correlated directly with the peak change in mean arterial pressure (r = 0.79, p less than 0.01). There was a moderate increase in heart rate in response to the decrease in blood pressure (73 +/- 15 to 83 +/- 15 beats per min, p less than 0.001). Two of the 11 patients did not reduce their hepatic venous pressure gradient after 0.6 mg nitroglycerin. Reductions in portal pressure were observed with both increases and moderate decreases in azygos blood flow, suggesting that, as observed in experimental animals, the portal-pressure-reducing effect of nitroglycerin could be due to two different and independent mechanisms, a reduction in portal blood flow or portal-collateral vasodilatation.     

Increased blood flow through the portal system in cirrhotic rats

Portal venous pressure is the result of the interplay between portal venous blood flow and the vascular resistance offered to that flow. Whether portal hypertension is maintained only by an increased portal venous resistance or also by an increased blood flow within the portal venous system is still open to speculation. To resolve these differences, splanchnic and systemic hemodynamics were evaluated in cirrhotic rats, induced by CCl4. Blood flow and portal-systemic shunting were measured by radioactive microsphere techniques. All cirrhotic rats had portal hypertension (portal venous pressure 13.5 +/- 1.1 vs. 9.0 +/- 0.5 mmHg, in normal control rats; p less than 0.01), but portal-systemic shunting in cirrhosis (31% +/- 13% vs. 0.2% +/- 0.02%; p less than 0.05) was variable, ranging from 1% to 97%. Portal venous inflow, the total blood flow within the portal system, was increased in cirrhotic rats (5.75 +/- 0.04 vs. 4.52 +/- 0.36 ml/min per 100 g; p less than 0.05). Total splanchnic arterial resistance was reduced in cirrhotic rats (3.3 +/- 0.2 vs. 5.8 +/- 0.5 dyn X s X cm-5 X 10(5); p less than 0.01). Portal venous resistance, however, was not abnormally elevated in cirrhotic rats (4.6 +/- 0.5 vs. 4.7 +/- 0.5 dyn X s X cm-5 X 10(4), p = NS). Splanchnic hemodynamics in cirrhotic rats demonstrate that portal hypertension is maintained, at least in part, by a hyperdynamic portal venous inflow. The hemodynamic data in cirrhotic rats provided evidence that supports the role of an increased portal blood flow in portal hypertension and gives a quantitative definition of splanchnic hemodynamics in intrahepatic portal hypertension.     

Hyperdynamic circulation in a chronic murine schistosomiasis model of portal hypertension

Chronic murine schistosomiasis is a natural disease model of portal hypertension closely mimicking the clinical and histological features of human hepatic schistosomiasis. We studied the splanchnic and systemic hemodynamics in the murine model of schistosomiasis by radioactive microsphere technique. Mice infected with 60 cercariae of Schistosoma mansoni (n = 8) were studied hemodynamically 11 wk after the infection and were compared with age-matched healthy controls (n = 11). Mean portal venous inflow in the infected mice (3.82 +/- 0.32 ml/min) was 61% higher than in the healthy animals (2.37 +/- 0.25 ml/min; p less than 0.01). A twofold increase in hepatic arterial flow was also seen in mice with schistosomiasis (0.47 +/- 0.14 ml/min) as compared with controls (0.16 +/- 0.03 ml/min; p less than 0.05), whereas splanchnic arteriolar resistance (60.91 +/- 7.64 vs. 101.21 +/- 11.06 mm Hg.min.ml-1.gm; p less than 0.05) and peripheral vascular resistance (112.05 +/- 14.05 vs 254.53 +/- 29.86 mm Hg.min.ml-1.gm; p less than 0.01) were reduced. There was a significant increase in cardiac index (752 +/- 99 vs. 453 +/- 55 ml.min-1.kg body weight-1; p less than 0.05) and reduction in mean arterial pressure (81.37 +/- 3.09 vs. 101.45 +/- 5.85 mm Hg; p less than 0.05) in the infected animals compared with controls. These observations clearly demonstrate the existence of a hyperdynamic circulatory state in this model of portal hypertension.     

Acute effect of propranolol on splanchnic circulation in normal and portal hypertensive rats

Propranolol decreases portal venous pressure in patients with cirrhosis but no method is available in man to study the effect of this beta-blocker on splanchnic organ blood flow. Because in rats, the microsphere method allows evaluation of regional blood flow, the acute effect of propranolol on both splanchnic and systemic circulations was studied in normal rats and in rats with portal hypertension due to portal vein stenosis. Portal venous pressure significantly decreased during propranolol administration in normal (5.6 +/- 1.0-4.7 +/- 1.1 mm Hg; mean +/- SD) as well as in portal hypertensive rats (11.7 +/- 2.3-10.3 +/- 1.8 mm Hg). Propranolol slightly decreased cardiac output and arterial pressure in all rats. Portal tributary blood flow was significantly reduced by propranolol in normal rats (17.4 +/- 3.0-11.3 +/- 2.2 ml/min) and in portal hypertensive rats (23.7 +/- 5.0-16.6 +/- 3.3 ml/min). Accordingly vascular resistance of the different organs in the portal venous territory increased in these rats receiving propranolol. The percentage of the decrease in portal tributary blood flow was significantly more marked than the percentage of reduction in cardiac output in portal hypertensive rats but, in normal rats, these percentages were parallel. Hepatic arterial blood flow did not change or slightly increased and, consequently, hepatic arterial vascular resistance decreased. These findings further clarify the marked effects of propranolol on splanchnic circulation.     

Low doses of isosorbide mononitrate attenuate the postprandial increase in portal pressure in patients with cirrhosis

Postprandial hyperemia is associated with a significant increase in portal pressure in cirrhosis, which may contribute to progressive dilation and rupture of gastroesophageal varices. In cirrhosis, an insufficient hepatic production of nitric oxide (NO) may impair the expected hepatic vasodilatory response to increased blood flow, further exaggerating the postprandial increase in portal pressure. This study was aimed at investigating whether low doses of an oral NO donor might counteract the postprandial peak in portal pressure. Twenty-three portal hypertensive cirrhotics, 8 of them under propranolol therapy, were randomized to receive orally 5-isosorbide mononitrate (ISMN; 10 mg; n = 11) or placebo (n = 12) and a standard liquid meal 15 minutes later. Hepatic venous pressure gradient (HVPG), mean arterial pressure (MAP), and hepatic blood flow (HBF) were measured at baseline and 15, 30, and 45 minutes after a meal. ISMN significantly attenuated the postprandial increase in portal pressure as compared with placebo (peak HVPG increase: 2.4 +/- 1.4 mm Hg vs. 5.2 +/- 2.1 mm Hg, P =.002). Percentual increases in HBF were similar in both groups. MAP decreased slightly in ISMN group (-7.5% +/-.5%; P <.01 vs. baseline). These effects were also observed in patients on chronic propranolol therapy. In conclusion, hepatic NO supplementation by low doses of ISMN effectively reduces the postprandial increase of portal pressure in cirrhosis, with only a mild effect on arterial pressure. The same was observed in patients receiving propranolol. Our results suggest that therapeutic strategies based on selective hepatic NO delivery may improve the treatment of portal hypertension.     

Reduction of Portal Pressure by Chronic Administration of Isosorbide Dinitrate in Patients with Cirrhosis: Effects on Systemic and Splanchnic Hemodynamics and Liver Function

We investigated the chronic effects of isosorbide dinitrate on systemic and splanchnic hemodynamics and liver function in 13 patients with liver cirrhosis and portal hypertension. Placebo administration for 4 wk (n = 4) had no significant effects on these parameters. In contrast, oral administration of 40 mg/day of isosorbide dinitrate for 4 wk (n = 9) caused a significant fall in portal pressure (-18%, p less than 0.02), as evaluated by measurements of the hepatic venous pressure gradient with no modification in hepatic blood flow (from 0.72 +/- 0.29 to 0.71 +/- 0.34 L/min, NS), suggesting decreased intrahepatic or collateral vascular resistance. On the other hand, there was no significant correlation between the changes in mean arterial pressure and hepatic venous pressure gradient (r = 0.42). Thus, it seems unlikely that a reduction in portal blood inflow by baroreceptor-mediated reflex splanchnic vasoconstriction contributed to the fall in portal pressure. In addition, this drug had no adverse effects on liver function, as evaluated by measurements of the intrinsic clearance. These results suggest that chronic administration of isosorbide dinitrate could be a potentially useful and associated with cirrhosis.     

Hepatic arterial pulsatility index in cirrhosis: correlation with portal pressure.

BACKGROUND/AIMS: Determination of the pulsatility index by means of duplex sonography provides the opportunity to evaluate the vascular resistance of the hepatic artery noninvasively. The aim of this study was to investigate the relationship between the hepatic arterial pulsatility index and the hepatic venous pressure gradient in cirrhosis. METHODS: In 50 patients with cirrhosis, hepatic venous pressure gradient was determined in the fasting state. Immediately thereafter, hepatic arterial pulsatility index and portal blood flow velocity were measured by duplex sonography with no knowledge of hepatic venous pressure values. In addition, the duplex parameters were determined in 20 controls. RESULTS: Hepatic arterial pulsatility index was significantly higher in patients with cirrhosis than in controls (0.92+/-0.1 vs. 1.14+/-0.18; p<0.001) and directly correlated with the hepatic venous pressure gradient (r = 0.7; p<0.001). Furthermore, weak correlations were found between hepatic arterial pulsatility index and Child-Pugh score (r = 0.49; p<0.01) and between portal blood flow velocity and hepatic venous pressure gradient (r = -0.48; p<0.01). CONCLUSION: In cirrhosis the hepatic arterial vascular resistance seems to increase parallel to the rise of the portal pressure. Therefore, duplex sonographic determination of the hepatic arterial pulsatility index may contribute to the noninvasive evaluation of portal hypertension.     

Intraportal administration of glyceryl trinitrate or nitroprusside exerts more systemic than intrahepatic effects in anaesthetised cirrhotic rats.

BACKGROUND/AIMS: Increased intrahepatic vascular tone can be pharmacologically manipulated in isolated cirrhotic livers. Intrahepatic endothelial dysfunction may lead to a decreased production of the potent endogenous vasodilator nitric oxide in cirrhotic livers. The aims of the study were to determine whether portal pressure can be lowered in vivo by injecting nitric oxide donors glyceryl trinitrate or nitroprusside directly in the portal vein and whether this is related to a decrease in intrahepatic resistance. METHODS: In anaesthetised CCl4 cirrhotic rats, intraportal doses of glyceryl trinitrate 0.5, 1 or 5 microg/kg/ min or nitroprusside 1, 5 or 10 microg/kg/min did not decrease portal pressure but only arterial pressure. Systemic and splanchnic haemodynamics were measured before and during 15 min intraportal infusion of glyceryl trinitrate 10 microg/kg/min or nitroprusside 20 microg/kg/min. RESULTS: Glyceryl trinitrate decreased portal pressure from 14.0+/-1.1 to 11.8+/-1.4 mm Hg, splanchnic perfusion pressure from 102+/-10 to 74+/-5 mm Hg and portal sinusoidal flow from 2.11+/-0.38 to 1.70+/-0.35 ml/min/g liver (all p<0.05). Nitroprusside did not decrease portal pressure significantly but led to a reduction of the splanchnic perfusion pressure (104+/-9 to 66+/-7 mm Hg) and the portal sinusoidal flow (2.39+/-0.50 to 1.77+/-0.31 ml/min/g liver; all p<0.05). Portal sinusoidal resistance was not altered by either drug. CONCLUSIONS: Intraportal infusion of nitric oxide donors decreased arterial pressure more than portal pressure. Portal sinusoidal resistance remained unaffected, but the liver parenchyma became less perfused with high doses. The systemic effects of nitric oxide donating drugs prevailed.     

急性肝内窦前型门静脉高压症大鼠肝内门体分流的变化及其意义

目的探讨急性肝内窦前型门静脉高压症时肝内门体分流的变化及其意义。方法经大鼠门静脉注射乳胶微球造成急性肝内窦前型门静脉高压症。采用肝山梨醇摄取率法测定功能性肝血流量和肝内门体分流量,采用放射性微球法测定肝内较大门体分流侧支(直径>15μm)的分流率。结果对照组肝山梨醇摄取率为(97.9±0.5)％,肝总血流量为每100g体重(2.52±0.23)ml／min。微球组,肝山梨醇摄取率锐减至(12.8±4.3)％,微球加肝动脉结扎组则下降至(4.1±0.7)％,t值为3.541和3.668,P值均<0.01;肝内门体分流量对照组、微球组、微球加肝动脉结扎组分别为每100g体重(0.06±0.02)、(1.46±0.15)和(1.16±0.19)ml／min,t值分别为5.468和6.869,P值均<0.01;门静脉血流量3组差异无统计学意义。结论肝内门体分流的直径大多<15μm。其开放可使70％的门静脉血绕过肝窦而直接注入肝静脉,并有效阻止了门静脉压力的升高。     

Potentiation of cocaine-induced coronary vasoconstriction by beta-adrenergic blockade

STUDY OBJECTIVE: To determine whether beta-adrenergic blockade augments cocaine-induced coronary artery vasoconstriction. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: A cardiac catheterization laboratory in an urban teaching hospital. PATIENTS: Thirty clinically stable patient volunteers referred for catheterization for evaluation of chest pain. INTERVENTIONS: Heart rate, arterial pressure, coronary sinus blood flow (by thermodilution), and epicardial left coronary arterial dimensions were measured before and 15 minutes after intranasal saline or cocaine administration (2 mg/kg body weight) and again after intracoronary propranolol administration (2 mg in 5 minutes). MEASUREMENTS AND MAIN RESULTS: No variables changed after saline administration. After cocaine administration, arterial pressure and rate-pressure product increased; coronary sinus blood flow fell (139 +/- 28 [mean +/- SE] to 120 +/- 20 mL/min); coronary vascular resistance (mean arterial pressure divided by coronary sinus blood flow) rose (0.87 +/- 0.10 to 1.05 +/- 0.10 mm Hg/mL.min); and coronary arterial diameters decreased by between 6% and 9% (P less than 0.05 for all variables). Subsequently, intracoronary propranolol administration caused no change in arterial pressure or rate-pressure product but further decreased coronary sinus blood flow (to 100 +/- 14 mL/min) and increased coronary vascular resistance (to 1.20 +/- 0.12 mm Hg/mL.min) (P less than 0.05 for both). CONCLUSIONS: Cocaine-induced coronary vasoconstriction is potentiated by beta-adrenergic blockade. Beta-adrenergic blocking agents probably should be avoided in patients with cocaine-associated myocardial ischemia or infarction.     

Chronic bile duct ligation in the dog: hemodynamic characterization of a portal hypertensive model

Splanchnic and systemic hemodynamics were measured in six normal dogs and in 18 dogs that had the bile ducts ligated for a period of 8 weeks. In the bile duct-ligated dogs, there was a decrease in arterial pressure (110 +/- 4 mm Hg vs. normal 136 +/- 6 mm Hg; p less than 0.005) and peripheral vascular resistance (4.60 +/- 0.38 vs. 6.28 +/- 0.38 dynes-sec-cm-5; p less than 0.02), and an increase in cardiac index (129 +/- 7 vs. 98 +/- 9 ml per min per kg; p less than 0.05). The splanchnic hemodynamic characteristics in the bile duct-ligated dogs included an increase in portal venous pressure (13.3 +/- 0.6 mm Hg vs. 6.7 +/- 0.5 mm Hg; p less than 001) and wedged hepatic venous pressure (14 +/- 1.2 mm Hg), the development of extensive portal-systemic shunting (49 +/- 10 vs. 0.03 +/- 0.01%; p less than 0.01), and a decrease in portal venous flow (194 +/- 21 ml per min vs. 427 +/- 21 ml per min; p less than 0.001). This study demonstrated that chronic bile duct-ligated dogs develop sinusoidal portal hypertension with extensive portal-systemic shunting and a hyperdynamic systemic circulation. These findings closely resembled hemodynamic abnormalities observed in human cirrhosis and suggest that this model is useful in physiopathological and pharmacological studies of portal hypertension.     

Mixed endothelin receptor antagonist, SB209670, decreases portal pressure in biliary cirrhotic rats in vivo by reducing portal venous system resistance

BACKGROUND/AIMS: This study aimed to evaluate the hemodynamic effects of endothelin-1 or mixed endothelin receptor antagonist, SB209670 in cirrhotic rats, and to elucidate the role of endothelin in cirrhotic portal hypertension. METHODS: Secondary biliary cirrhosis was induced by bile duct ligation. Hemodynamics were studied using the radioactive microsphere technique. RESULTS: Plasma and hepatic endothelin levels in cirrhotic rats were significantly higher than those in normal rats (plasma, 9.0+/-1.3 vs. 2.6+/-0.5 pg/ml, p<0.001; liver, 74.8+/-13.3 vs. 12.6+/-2.5 pg/g wet tissue, p<0.001). Intraportal administration of endothelin-1 (3 nmol/kg) progressively raised portal pressure without an initial transient reduction, which was observed in systemic arterial pressure, in both cirrhotic and normal rats. SB209670 (5.4 micromol/kg) reduced portal pressure in cirrhotic rats (-19+/-5%, p<0.01) without modifying systemic arterial pressure and renal blood flow, but not in normal rats. This reduction was associated with reduced portal venous system resistance (vehicle, 2.5+/-0.2 vs. SB209670, 1.7+/-0.1 mmHg x min x 100 g bw/ml, p<0.01), but not with change in portal venous inflow and collateral blood flow. CONCLUSIONS: Mixed endothelin antagonist, SB209670, decreased portal pressure by reducing portal venous system resistance without modifying systemic arterial pressure and renal blood flow in cirrhotic rats. This result, together with the findings that plasma and hepatic endothelin levels were elevated in cirrhotic rats and that exogenous endothelin-1 increased portal pressure, provides further support for a role of endothelin in portal hypertension and suggests a potential use of mixed endothelin antagonist in the pharmacological treatment of portal hypertension.     

Octreotide inhibits the meal-induced increases in the portal venous pressure of cirrhotic patients with portal hypertension: a double-blind, placebo-controlled study.

The aim of this study was to determine the effects of the long-acting somatostatin analog, octreotide, on portal venous pressure and collateral blood flow in cirrhotic patients with portal hypertension during fasting and postprandial states. In a double-blind, placebo-controlled study, we investigated the effects of octreotide on the hepatic venous pressures and azygos blood flow of 21 patients before and after a standard liquid meal containing 40 gm of protein in 250 ml. Octreotide significantly reduced azygos blood flow from a mean of 499 +/- 65 ml/min to a mean of 355 +/- 47 ml/min (p < 0.01), but it had no effect on the hepatic venous pressure gradient. The hepatic venous pressure gradient of patients in the placebo group increased significantly, from a fasting mean of 16.4 +/- 1.6 mm Hg to a mean of 20.0 +/- 1.7 mm Hg 30 min after the meal (p < 0.01). In a second protocol hepatic venous pressures were measured in 20 patients at 30-min intervals for 2 hr after ingestion of the mixed meal. Again the placebo group showed a significant increase in the hepatic venous pressure gradient 30 min after the meal (20.4 +/- 1.5 mm Hg vs. 18.2 +/- 1.2 mm Hg; p < 0.05), but the group receiving octreotide showed no significant changes during the 2 hr of observation. We conclude that octreotide significantly reduces azygos blood flow, with little effect on portal venous pressure, and that it appears to inhibit postprandial increases in portal pressure in cirrhotic patients with portal hypertension.     

Measurement of Intrahepatic Pressure as an Index of Hepatic Sinusoidal Pressure

Intrahepatic pressure was measured in 148 patients with liver disease (32 outpatients, 116 inpatients) and 13 controls with almost normal liver histology (inpatients), with a 23-gauge needle (inner diameter 0.38 mm). Intrahepatic pressure was significantly elevated in the group order of chronic active hepatitis without bridging necrosis (n = 17, 9.2 +/- 3.0 mm Hg), chronic active hepatitis with bridging necrosis (n = 24, 12.3 +/- 5.7), and posthepatitic liver cirrhosis (n = 65, 18.8 +/- 4.2), compared with controls (n = 13, 6.8 +/- 2.7), whereas it was not elevated in the group of idiopathic portal hypertension (n = 9, 7.8 +/- 2.5 mm Hg), acute hepatitis (n = 10, 8.4 +/- 2.6 mm Hg), and chronic persistent hepatitis (n = 23, 7.9 +/- 2.7 mm Hg), compared with controls. As complications, four patients had abdominal discomfort continuing for more than a day; however, patients were allowed to walk after they had rested on their beds for 30 min. In 37 patients (27 with cirrhosis, seven idiopathic portal hypertension, and three others), portal vein and/or hepatic vein catheterization was performed during the same procedure of intrahepatic pressure measurement. Intrahepatic pressure showed significant correlations with corrected wedged hepatic vein pressure (r = 0.91), portohepatic gradient (r = 0.69), wedged hepatic vein pressure (r = 0.79), and portal vein pressure (r = 0.68). Slopes were 0.97, 0.83, 0.66, and 0.65, respectively. In conclusion, intrahepatic pressure reflects hepatic sinusoidal pressure (corrected wedged hepatic vein pressure), and intrahepatic pressure starts to elevate at the stage of chronic active hepatitis.     

Spontaneous intermittent reversal of blood flow in intrahepatic portal vein branches in cirrhosis of the liver

The intrahepatic portal venous flow in cirrhosis of the liver was evaluated by percutaneous transhepatic portography and hepatic arteriography. Spontaneous reversal of flow in segmental portal vein branches was documented. Changes in hepatic arterial inflow and portal venous pressure may result in intermittent changes in the direction of flow in segmental portal venous branches within the cirrhotic liver. Segmental reversal of blood flow seems to be the precursor of total hepatofugal portal flow.     

Glucagon hinders the effects of somatostatin on portal hypertension. A study in rats with partial portal vein ligation.

Whether the decrease of portal venous inflow and portal pressure induced by somatostatin is related to the effects of somatostatin in inhibiting the secretion of glucagon and other vasodilatory peptides that are increased in portal hypertension was investigated in the current study. Splanchnic vascular resistance and splanchnic blood flow were determined using radioactive microspheres in rats with portal hypertension caused by partial portal vein ligation. Somatostatin infusion significantly decreased portal pressure (from 13.1 +/- 1.9 to 12.1 +/- 2.2 mm Hg; P less than 0.05). This was associated with a significant decrease in portal venous inflow caused by splanchnic vasoconstriction, as evidenced by increased splanchnic vascular resistance, and with a marked suppression of glucagon secretion. The simultaneous infusion of somatostatin and glucagon (2.8 ng/min, a dose that prevented any decrease in circulating glucagon levels) abolished all the hemodynamic effects of somatostatin. This effect seems to be specific because no hemodynamic changes were noted in portal hypertensive rats receiving only the glucagon infusion.     

Endothelin-1 and heme oxygenase-1 as modulators of sinusoidal tone in the stress-exposed rat liver

Heme oxygenase (HO)-1 is up-regulated after ischemia/reperfusion and contributes to maintenance of hepatic perfusion and integrity. Blockade of HO-1 leads to an increased portal pressor response in the stress-exposed liver. We tested whether the increase in portal pressure reflects unmasking of a concomitant up-regulation of the vasoconstrictor endothelin (ET)-1. Hemorrhagic shock induced messenger RNAs encoding HO-1 (16-fold) and ET-1 (9-fold) with a similar time course in the liver. At maximum induction of both mediators, rats received either vehicle or the endothelin ET(A/B) antagonist bosentan (10 mg/kg intravenously). Subsequently, the HO pathway was blocked in all animals by tin-protoporphyrin (SnPP)-IX (50 micromol/kg intravenously). Portal and sinusoidal hemodynamics were measured using microflow probes and intravital microscopy, respectively. Blockade of the HO pathway led to a significant increase in portal resistance (sham/SnPP-IX, 0.17 +/- 0.046 mm Hg. min. mL(-1); shock/vehicle/SnPP-IX, 0.57 +/- 0.148 mm Hg. min. mL(-1); P <.05) and a decrease in sinusoids conducting flow (shock/vehicle/SnPP-IX: baseline, 28.3 +/- 0.85 sinusoids/mm; 10 minutes after SnPP-IX, 23.1 +/- 1.09 sinusoids/mm; P <.05). Intravital microscopy showed narrowing of failing sinusoids colocalizing with stellate cells after blockade of the HO pathway. Blockade of ET(A/B) receptors attenuated the increase in portal resistance (shock/bosentan/SnPP-IX, 0.29 +/- 0.051 mm Hg. min. mL(-1)) and prevented sinusoidal perfusion failure (shock/bosentan/SnPP-IX: baseline, 28.2 +/- 0.97 sinusoids/mm; 10 minutes after SnPP-IX, 28.8 +/- 1.18 sinusoids/mm) as well as sinusoidal narrowing. In conclusion, a functional interaction of the up-regulated vasodilatory HO system and the vasoconstrictor ET-1 on the sinusoidal level exists under stress conditions. Both mediator systems affect sinusoidal diameter via direct action on hepatic stellate cells in vivo.