Nitrovasodilators and portal hypertension

Pharmacotherapy plus endoscopic intervention is more effective than pharmacotherapy or endoscopy alone in the secondary prevention of esophageal variceal bleeding: a meta-analysis of randomized, controlled trials

BACKGROUND

Previous clinical trials on the treatment of esophageal variceal bleeding yielded mixed results regarding the efficacy of endoscopic procedures compared with pharmacotherapy only.

OBJECTIVE

To compare the efficacy of endoscopic procedures with that of pharmacotherapy in the prevention of mortality and rebleeding.

DESIGN AND SETTING

A systematic literature review was performed to identify randomized, controlled trials of the efficacy of pharmacotherapy and endoscopic therapy. A meta-analysis was performed by using the Comprehensive MetaAnalysis software package. A 2-sided alpha error <.05 was considered statistically significant (P < .05).

PATIENTS

Twenty-five clinical trials with a total of 2159 patients were eligible for meta-analysis.

OUTCOME MEASUREMENTS

Relative risk (RR) with 95% confidence interval (CI) was computed for all-cause mortality, mortality from rebleeding, all-cause rebleeding, and rebleeding caused by varices.

RESULTS

Pharmacotherapy was as effective as endoscopic procedures in preventing rebleeding (RR 1.067; 95% CI, 0.865-1.316; P = .546), variceal rebleeding (RR 1.143; 95% CI, 0.791-1.651; P = .476), all-cause mortality (RR 0.997; 95% CI, 0.827-1.202, P = .978), and mortality from rebleeding (RR 1.171; 95% CI, 0.816-1.679; P = .39). Pharmacotherapy combined with endoscopic procedures did not reduce all-cause mortality (RR 0.787; 95% CI, 0.587-1.054; P = .108) or mortality caused by rebleeding (RR 0.786; 95% CI, 0.445-1.387; P = .405) compared with endoscopic procedures. However, combination therapy (endoscopic procedure plus pharmacotherapy) significantly reduced the incidence of all rebleeding (RR 0.623; 95% CI, 0.523-0.741; P < .001) and variceal rebleeding (RR 0.601; 95% CI, 0.440-0.820; P < .001).

LIMITATIONS

Heterogeneity of patient population and different treatment protocols may have affected our meta-analysis.

CONCLUSION

Pharmacotherapy may be as effective as endoscopic therapy in reducing rebleeding rates and all-cause mortality. Pharmacotherapy plus endoscopic intervention is more effective than endoscopic intervention alone.

[Progress in portal hypertension]

In patients with portal hypertension due to cirrhosis, the mechanisms responsible for circulatory modifications are well-known. An elevation in intrahepatic vascular resistance related to a hepatic endothelin hyperproduction and an arterial nitric oxide (NO) hyperproduction. The presence and the degree of portal hypertension might be determined by the measurement of the hepatic venous pressure gradient but non-invasive technique as FibroTest or FibroScan might be useful to estimate the presence of severe portal hypertension. Numerous substances decrease portal pressure either by reducing hepatic vascular resistance or by reducing portal tributary blood flow. The combination of both types of substances is probably the best pharmacological treatment of portal hypertension but further hemodynamic and clinical studies are needed.

Transjugular intrahepatic portosystemic shunt in the prevention of rebleeding in oesophageal varices

Variceal bleeding is a common complication of cirrhosis and has a high in-patient mortality (30-50%). Rebleeding is a major cause of death and occurs in 35% of patients at 6 weeks after the initial bleeding episode and 75% at 1 year. Therefore, strategies that improve survival by preventing rebleeding in the early period are crucial to improve long-term survival. This review concentrates on the evidence for transjugular intrahepatic portosystemic shunt in the prevention of rebleeding. Transjugular intrahepatic portosystemic shunt in comparison with endoscopic and pharmacological therapies is clearly superior at reducing the rate of rebleeding in those patients who had an oesophageal variceal haemorrhage. It, however, does not improve mortality and is associated with a greater risk of encephalopathy and is more costly than endoscopic procedures. It is therefore generally used when endoscopic therapy has failed but may be useful in patients who would tolerate a rebleed poorly such as Child's C patients. Randomized-controlled trials are required to evaluate the role of polytetrafluoroethylene shunts in the prevention of rebleeding as their improved patency and suggested reduced incidence of encephalopathy make them a very attractive potential treatment for rebleeding.

When endoscopic therapy or pharmacotherapy fails to control variceal bleeding: what should be done? Immediate control of bleeding by TIPS?

BACKGROUND

Acute variceal bleeding is the major cause of death in patients with chronic liver disease. This justifies the search for a more effective therapy to achieve rapid and definitive hemostasis in every patient. At present, the recommended standard treatment for acute variceal bleeding consists of immediate drug treatment with terlipressin or octreotide together with early endoscopic band ligation or sclerotherapy. In the case of ectopic varices terlipressin and cyanoacrylate embolization (if varices can be reached by endoscope) are in use.

FOCUS

The treatment is considered to have failed when bleeding continues or significant bleeding recurs within 48 h. This indicates the need for emergency transjugular intrahepatic portosystemic shunting (TIPS) which has been regarded as rescue treatment of choice when standard treatment fails. Although randomized studies against supportive treatment are lacking, the high efficacy and relatively low mortality after TIPS implantation are convincing. It is reasonable that smaller shunts should be preferred (probably 8 mm in diameter) since most patients have an increased risk of liver failure. To increase the effect of the shunt with respect to acute hemostasis it should be combined with transjugular embolization of the varices.

CONCLUSION

Only strict adherence to the definition of failure of standard treatment and a generous indication to the TIPS implantation before multiorgan failure occurs may decrease the high mortality of acute variceal bleeding.

Nadolol is superior to isosorbide mononitrate for the prevention of the first variceal bleeding in cirrhotic patients with ascites

BACKGROUND/AIMS

beta-blockers effectively prevent first variceal bleeding (FVB) in cirrhotic patients. In patients with ascites, however, their use might be precluded by a high rate of contraindications and side effects. We compared the efficacy and applicability of nadolol and isosorbide-mononitrate (IsMn) in preventing FVB in a population of cirrhotic patients at high risk of variceal bleeding with ascites, who can be frequently intolerant to beta-blockers.

METHODS

A total of 80 consecutive cirrhotic patients with ascites and esophageal varices (25% average risk of bleeding at 1 year) were considered, 28 were excluded due to contraindications and 52 were randomly assigned to receive nadolol (n=25) or IsMn (n=27).

RESULTS

Frequency of contraindications was greater for beta-blockers than IsMn (35 versus 0%, P=0.001). During 21.3+/-11.6 months of follow-up, side effects forced six patients taking nadolol and four taking IsMn to stop treatment. Bleeding occurred in two patients taking nadolol and ten taking IsMn. The probability of bleeding was significantly lower in the nadolol group (P<0.05), whereas overall survival was similar (seven patients on IsMn and eight on nadolol died, P=0.3).

CONCLUSIONS

In patients with ascites IsMn is tolerated but ineffective while nadolol is effective but less tolerated.

Nitrovasodilators inhibit platelet-derived growth factor-induced proliferation and migration of activated human hepatic stellate cells

BACKGROUND & AIMS

Nitrovasodilators have been proposed for the treatment of portal hypertension alone or in combination with beta-blockers. In addition to their vasodilatory properties, nitric oxide (NO) donors may exert direct antifibrogenic properties. We evaluated the effect of nitroglycerin (NTG) and S-nitroso-N-acetyl penicillamine (SNAP) on the mitogenic and chemotactic properties of platelet-derived growth factor (PDGF)-BB and the modulation of the relative intracellular signaling pathways in fully activated human hepatic stellate cells (HSCs), a cell type that plays an active role in liver fibrogenesis and portal hypertension.

METHODS & RESULTS

Both NTG and SNAP induced a dose-dependent decrease in PDGF-induced DNA synthesis and cell migration, which was associated with a decrease in PDGF-induced intracellular Ca(2+) increase and extracellular signal-regulated kinase (ERK) activity. These effects were not related to activation of the classic soluble guanylate cyclase (sGC)/guanosine 3',5'-cyclic monophosphate pathway; accordingly, Western blot analysis of HSC lysates revealed the absence of the alpha(1)beta(1) ubiquitous subunits of sGC, whereas they were detectable in quiescent HSCs, freshly isolated from normal human liver. Conversely, both NTG and SNAP induced a more than 10-20-fold increase in prostaglandin E(2) in cell supernatants within 1 minute, associated with an increase in intracellular adenosine 3',5'-cyclic monophosphate levels. Accordingly, the inhibitory effects of NO donors on PDGF action and signaling were eliminated after preincubation with ibuprofen.

CONCLUSIONS

These results suggest that NO donors may exert a direct antifibrogenic action by inhibiting proliferation, motility, and contractility of HSCs in addition to a reduction of fibrillar extracellular matrix accumulation.

Isosorbide mononitrate and propranolol compared with propranolol alone for the prevention of variceal rebleeding

The aim of this study was to test the effectiveness of isosorbide-5-mononitrate (IM) as an adjunct to propranolol (PR) in the prevention of variceal rebleeding. Ninety-five cirrhotic patients with variceal bleeding were randomly assigned to treatment with PR + IM (46 patients) or PR alone (49 patients). Eighteen patients in the PR + IM group and 28 in the PR group had rebleeding during the 2 years after randomization. The actuarial probability of rebleeding 2 years after randomization was lower in the PR + IM group (40.4% vs. 57.4%) but the difference was not significant (P =. 09). However, the decrease in the risk of rebleeding reached statistical significance after stratification according to age, i.e. less than 50 versus >/=50 years old, (P =.03) or by adding an additional year of follow-up (P =.05). No significant difference was found in rebleeding index and survival. The multivariate Cox analysis indicated first, that both treatment (P =.03) and age (P =. 001) were factors predictive of rebleeding and second, that PR + MI reduced the risk of rebleeding by half (relative risk: 0.51, 95% confidence interval: 0.28-0.95). Seven patients in the PR + MI group and 1 patient in the PR group had to discontinue one of the drugs because of adverse events (P =.03). These results suggest that the addition of IM improves the efficacy of PR alone in the prevention of variceal rebleeding in cirrhotic patients. However no beneficial effects were observed on other parameters reflecting the efficacy of treatment.

Influence of nitrovasodilators and endothelin-1 on rheology of human blood in vitro

1. The shear stress of flowing blood profoundly influences the release of endothelium-dependent vasodilative and constrictive factors. Conversely, the influence of these mediators such as nitric oxide (NO) or endothelin-1 (ET-1) on blood rheology remains elusive. In the present study the influence of nitrovasodilators and ET-1 on red blood cell (RBC) shape and whole blood viscosity were investigated. 2. Incubation of whole blood with sodium-nitroprusside (SNP, 10-5 - 10-2 M), glyceryl trinitrate (GTN, 0.0001 - 0.1 mg mL-1), S-nitroso-N-acetylpenicillamine (SNAP, 10-6 - 10-3 M), and the active metabolite of molsidomine (SIN-1, 10-6 - 10-3 M), but not molsidomine (10-6 - 10-3 M), resulted in significantly increased amounts of methaemoglobin, indicating a relevant interaction with RBCs. Treatment with SNP at 10-2 M induced a marked echinocytosis (morphological index: 2.23+/-0.98 vs -0.17+/-0.10; P<0.001) and increased blood viscosity (haematocrit 45%) at a high shear rate of 94.5 s-1 (6.46+/-0.60 vs 5.07+/-0.35 mPa.s; P<0.01) and a low shear rate of 0.1 s-1 (88.6+/-36.8 vs 42.1+/-11.7 mPa.s; P<0.01). Echinocytosis was probably due to cyanide accumulation. SIN-1 at 10-3 M slightly decreased high shear viscosity (4.88+/-0.28 vs 4. 95+/-0.30 mPa.s; P<0.05). SNAP at 10-3 M slightly increased both high (5.14+/-0.23 vs 5.05+/-0.24 mPa.s; P<0.01) and low shear (53.9+/-7.2 vs 51.2+/-5.9 mPa.s; P<0.05) viscosity. Molsidomine and GTN failed to influence whole blood viscosity. ET-1 (10-9 - 10-6 M) had no effect on RBC shape and viscosity. 3. We conclude that the most important modulators of vascular tone, NO and ET-1, do not affect RBC shape and blood viscosity, which is important from both a physiological and a pharmacological point of view.

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.

Vascular hyporeactivity persists despite increased contractility after long-term administration of isosorbide dinitrate in portal hypertensive rats

BACKGROUND/AIMS

Portal hypertension is associated with decreased vascular responsiveness to vasoconstrictors, which may contribute to the hyperdynamics. Isosorbide dinitrate is an effective portal hypotensive drug. The present study aimed to investigate whether chronic administration of isosorbide dinitrate could affect vascular responsiveness in portal hypertensive rats.

METHODS

Portal hypertension was induced by partial portal vein ligation. Sham-operated (Sham) rats served as controls. There were four animal groups for this study: portal vein ligation-isosorbide dinitrate group, portal vein ligation-vehicle (Veh) group, Sham-isosorbide dinitrate group and Sham-Veh group. Isosorbide dinitrate (5 mg x kg(-1) x 12 h(-1) was given by gavage for 8 days starting 1 day before ligation and continuing thereafter. Mesenteric arteries were removed for contractile study after hemodynamic measurement.

RESULTS

Contractile responses to KCI (15-90 mM) and phenylephrine (10(-9)-10(-4) M) were recorded. Both vascular reactivity and sensitivity were significantly reduced in portal vein ligation rats as compared to Sham rats. Chronic isosorbide dinitrate treatment reduced portal venous pressure in portal vein ligation rats. Moreover, the maximal contractile responses to KCl and phenylephrine were significantly enhanced in both portal vein ligation and Sham rats after isosorbide dinitrate treatment, but relative hyporeactivity persisted in portal vein ligation rats. In contrast, a single dose of isosorbide dinitrate did not alter the contractile sensitivity or reactivity to KCl or phenylephrine in either portal vein ligation or Sham rats.

CONCLUSION

Our results show that long-term administration of isosorbide dinitrate enhanced vascular contractility in both portal vein ligation and Sham rats, but relative hyporeactivity persisted in portal vein ligation rats.

Vascular hyporesponsiveness to vasodilators in rats with cirrhosis

BACKGROUND/AIMS

In cirrhosis, the activation of nitric oxide and prostacyclin contributes to vasodilation, and ATP-sensitive K+ (KATP) channel activation or L-type calcium (Ca2+) channel inhibition may also play a role in this process. At the same time in cirrhosis, certain endogenous mechanisms may be stimulated which limit the influence of vasodilator mechanisms on vascular tone, thus altering vascular responses to exogenous substances such as nitric oxide donors, exogenous prostacyclin, KATP channel openers or L-type Ca2+ channel blockers. The aim of the present study was to examine the arterial depressor to these exogenous substances in normal rats and in rats with secondary biliary cirrhosis.

METHODS

Arterial depressor dose-response curves to nitroprusside (a nitric oxide donor, 5-60 micrograms.kg-1.min-1), prostacyclin (0.5-5 micrograms.kg-1) and aprikalim (a KATP channel opener, 10-200 micrograms.kg-1) were obtained in both groups. The effects of different L-type Ca2+ channel blockers, i.e. nicardipine (a dihydropyridine, 0.02-0.5 mg.kg-1), diltiazem (a benzothiazepine, 0.5-5 mg.kg-1) and verapamil (a phenylalkylamine, 0.02-0.2 mg.kg-1. min-1), were also studied.

RESULTS

Cirrhosis produced hyporeactivity to the arterial depressor effect of all doses of nitroprusside, the lowest dose of prostacyclin and the highest doses of aprikalim or diltiazem. Cirrhosis did not significantly change depressor responses to nicardipine or verapamil.

CONCLUSIONS

Rats with cirrhosis are hyporeactive to exogenous nitric oxide, prostacyclin, KATP channel opener and benzothiazepine (an L-type Ca2+ channel blocker). Therefore, cirrhosis-induced mechanisms seem to limit the decrease in vascular tone by most vasodilators. However, these mechanisms appear to be more marked in nitric oxide-mediated vasodilation than in other vasorelaxation mechanisms.

Role of pentobarbitone anaesthesia and sympathetic tone in the haemodynamic effects of isosorbide dinitrate in rats with cirrhosis

The haemodynamic effects of nitrovasodilators and their mechanisms of action on portal hypertension remain unclear. The splanchnic and systemic haemodynamic response to the infusion of isosorbide dinitrate (100 micrograms/kg per min), a nitrovasodilator, was investigated in cirrhotic rats. The role of the conscious state in the haemodynamic response to isosorbide dinitrate was examined using rats that were anaesthetized with pentobarbitone. The role of sympathetic tone in the haemodynamic response to isosorbide dinitrate was examined using rats pretreated with the ganglion blocker hexamethonium. Isosorbide dinitrate had no haemodynamic effects in conscious, unblocked normal and cirrhotic rats. Isosorbide dinitrate had no haemodynamic effects in normal and cirrhotic rats treated with hexamethonium. In normal anaesthetized rats, isosorbide dinitrate significantly decreased systemic vascular resistance (414 +/- 25 vs 290 +/- 26 dyn.s/cm-5 per 100 g). In cirrhotic anaesthetized rats, isosorbide dinitrate significantly decreased mean arterial pressure (98 +/- 6 vs 79 +/- 7 mmHg), systemic vascular resistance (318 +/- 30 vs 207 +/- 10 dyn.s/cm-5 per 100 g), portal pressure (14.0 +/- 1.0 vs 11.3 +/- 0.9 mmHg) and portal territory vascular resistance (1362 +/- 163 vs 1031 +/- 182 dyn.s/cm5 per 100 g). In conclusion, this study shows that the portal hypotensive effects of isosorbide dinitrate depend upon the alterations of vascular tone by pentobarbitone.

Acute effects of sublingual nitroglycerin on hepatic blood flow in healthy volunteers

Duplex sonography was used to assess the effects on hepatic blood flow after administering 0.6 mg nitroglycerin (NTG) sublingually to ten healthy volunteers. The study was a randomized, placebo-controlled, cross-over study in which subjects were studied on three separate occasions. Each visit involved administering either placebo or NTG followed by estimation of blood flow through a particular branch of the hepatic artery, portal vein, and hepatic vein every minute for 15 minutes after NTG and placebo administration. Two hours later, subjects were crossed over to the other treatment and the same vessel branch was again examined for 15 minutes. Total blood flow increased 7% in the portal vein and 27% in the hepatic vein during NTG treatment, but did not change significantly in the hepatic artery. Vascular resistance was increased in the hepatic artery and decreased in the portal and hepatic veins after NTG. Qualitatively, flow changed dramatically in the hepatic vein after NTG with the disappearance of normal retrograde flow. The results indicate that nitroglycerin effects hepatic blood flow through the portal and hepatic veins with a decrease in vascular resistance in the portal and hepatic veins and an increase in resistance in the hepatic artery.

Hemodynamic effects of combined treatment with somatostatin analogue (SMS 201-995) and low-dose isosorbide dinitrate on portal hypertension in conscious cirrhotic rats

The authors investigated whether combined treatment with the somatostatin analogue, SMS 201-995, and low-dose isosorbide dinitrate enhanced the hemodynamic effects of the individual agents on rats with thioacetamide-induced cirrhosis. Four groups of cirrhotic rats received SMS 201-995 (0.1 microgram.min-1.kg-1), isosorbide dinitrate (10 micrograms.min-1.kg-1), both agents, or placebo, respectively. Hemodynamics were measured serially in conscious rats, using a radioactive microsphere method. SMS 201-995 reduced portal venous inflow 21 +/- 4% and portal pressure 17 +/- 3%. Isosorbide dinitrate decreased portal venous inflow 20 +/- 4%, by inducing splanchnic vasoconstriction mediated by low pressure baroreflexes, and this agent also decreased portal pressure, by 14 +/- 2%. Portal venous resistance rose 7.6 +/- 3% with isosorbide dinitrate alone, but decreased 18 +/- 4% with combination therapy. This effect may have been induced by the pronounced vasodilatory effect of isosorbide dinitrate on the venous vasculature, since the reflex splanchnic vasoconstriction that occurs with low-dose isosorbide dinitrate disappears when this agent is combined with SMS 201-995. The decrease in portal pressure was more marked (22 +/- 4%) and changes in systemic hemodynamics were milder with the combined treatment. It was concluded that combination therapy with SMS 201-995 and low-dose isosorbide dinitrate may be beneficial for portal hypertension in liver cirrhosis.

Isosorbide-5-mononitrate versus propranolol in the prevention of first bleeding in cirrhosis

BACKGROUND

Hemodynamic studies have shown the efficacy of nitrates in reducing portal pressure in cirrhosis. We therefore studied the efficacy of isosorbide-5-mononitrate vs. propranolol in the prevention of first bleeding within a prospective controlled trial.

METHODS

One hundred eighteen cirrhotics with esophageal varices were blindly randomized to receive 20 mg of isosorbide-5-mononitrate three times a day (n = 57) or propranolol (n = 61) up to the maximum tolerated dose. Both groups also received ranitidine (150 mg/day).

RESULTS

The median follow-up was 29 months. Twenty-six patients dropped out (13 in the isosorbide group) because of poor compliance or complications unrelated to treatment. Eighteen patients died (9 in the isosorbide-treated group), 6 due to bleeding. The 1- and 2-year actuarial percentages of patients free of bleeding was 90.8% and 82.2% in the isosorbide-5-mononitrate--and 93.9% and 85.8% in the propranolol-treated groups, respectively (P = NS). These values are higher than those expected from the North Italian Endoscopic Club predicting scores. There were few major side effects in either group. The 2-year survival rate did not differ between the two groups (82.2% vs. 85.4%).

CONCLUSIONS

Isosorbide-5-mononitrate administered orally is a safe and effective alternative to propranolol in the prophylaxis of bleeding in cirrhosis.