Effects of propranolol on gastric microcirculation and acid secretion in portal hypertensive rats

Role of acute elevation of portal venous pressure by exogenous glucagon on gastric mucosal injury in rats with portal hypertension

Time-course studies revealed the increased susceptibility of the gastric mucosa to noxious injury in portal hypertension correlates with the level of elevated portal venous pressure and hyperglucagonemia. Whether acute elevation of portal venous pressure by exogenous glucagon aggravates such injury is not known. We tested the hypothesis that glucagon in a dose sufficient to acutely elevate portal venous pressure aggravates noxious injury of the gastric mucosa in rats with portal hypertension. Infusion of a portal hypotensive dose of somatostatin should reverse these changes. In anesthetized rats with portal vein ligation, glucagon, somatostatin or the combination was administered intravenously in a randomized, coded fashion. Acidified ethanol-induced gastric mucosal injury was determined. Portal venous pressure and gastric mucosal perfusion and oxygenation (reflectance spectrophotometry) were monitored to confirm the effects of the respective intravenous treatments. Exogenous glucagon exacerbated acidified ethanol-induced gastric mucosal injury. The exacerbation was attenuated by somatostatin. These changes paralleled the portal hypertensive and hypotensive effects of glucagon and somatostatin, respectively. Our data suggest that a unique mechanism is triggered with the onset of portal hypertension. In an antagonistic manner, glucagon and somatostatin modulate this novel mechanism that controls portal venous pressure and susceptibility of the gastric mucosa to noxious injury.

Gastric mucosal resistance to acute injury in experimental portal hypertension

1. The gastric mucosa of portal hypertensive rats exhibits important microvascular changes and a nitric oxide (NO)-dependent hyperemia. This study analyses whether portal hypertensive mucosa exhibits changes in its ability to withstand aggression. 2. Portal hypertension was induced by partial portal vein ligation (PPVL) or common bile duct ligation (CBDL) and gastric damage was induced by oral administration of ethanol or aspirin. Experiments were performed in conscious or anaesthetized rats and some animals were pre-treated with the NO-synthesis inhibitor L-NAME. 3. Conscious PPVL or CBDL rats showed an increased resistance to the damaging effects of ethanol. Oral administration of aspirin produced less gastric damage in PPVL conscious rats than in the control group. 4. The protective effects of portal hypertension were maintained in animals anaesthetized with ketamine and absent when pentobarbital was employed. 5. Pre-treatment with L-NAME restored the damaging effects of ethanol and aspirin in PPVL rats without modifying the level of damage in control animals. 6. Gastric bleeding induced by oral aspirin, as measured by the luminal release of (51)Cr-labelled erythrocytes, was significantly greater in PPVL rats than in control animals. 7. Semi-quantitative analysis by RT--PCR of the mRNA for endothelial NO-synthase (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) levels showed that the expression of iNOS was slightly increased in both the gastric mucosa and smooth muscle of PPVL rats. No changes were observed in eNOS and nNOS expression. 8. Conscious portal hypertensive rats exhibit an enhanced resistance to acute gastric damage which is absent under the influence of some types of anaesthesia and seems related to an increased synthesis of nitric oxide. However, mucosal lesions in these animals show an augmented bleeding per area of injury.

New insights into impairment of mucosal defense in portal hypertensive gastric mucosa

Portal hypertension (PHT) increases susceptibility of the gastric mucosa to injury. The aim of this study was to investigate whether PHT affects rat gastric mucosal defense mechanisms in vivo at the pre-epithelial, epithelial, and/or post-epithelial levels. PHT was produced in rats by staged portal vein ligation and sham-operated (SO) rats served as controls. The gastric mucosa was exposed, chambered, and continuously superfused with buffers under in vivo microscopy. We measured gastric mucosal gel layer thickness, surface epithelial cell intracellular pH (pHi), mucosal blood flow, and mucosal/serosal oxygenation. In PHT rats, gastric mucosal gel layer thickness was significantly reduced (88 +/- 16 microm in PHT rats vs. 135 +/- 25 microm in SO rats; P <0.0001), and the surface epithelial cell pHi was significantly decreased (6.80 +/- 0.11 in PHT rats vs. 7.09 +/- 0.21 in SO rats; P <0.01). Although total gastric mucosal blood flow was significantly increased in PHT rats by 72% (P <0.05), the oxygenation of the gastric mucosal surface was decreased by 42% (P <0.05) compared with SO rats. PHT impairs pre-epithelial (mucosal gel layer thickness), epithelial (pHi), and post-epithelial (maldistribution of blood flow) components of the gastric mucosal barrier. These findings can explain the increased susceptibility of portal hypertensive gastric mucosa to injury.

Portal-hypertensive gastropathy

In the present article we describe updated information concerning the clinical feature of portal-hypertensive gastropathy (PHG), which is characterized by mucosal and submucosal vascular dilatation without inflammation. Although this lesion represents non-variceal bleeding, there is a wide variation of its prevalence. Portal pressure and some humoral factors may play important roles in its pathogenesis. Gastric acid secretory activity is reduced, whereas the gastric mucosal barrier is impaired. With regard to gastric mucosal haemodynamics, whether 'overflow' (i.e. active congestion) or 'stasis' (i.e. passive congestion) cause gastric mucosal hyperaemia is not known. A severe lesion is a potential source of bleeding, while mild lesions are of little clinical significance and endoscopic variceal obliteration aggravates PHG in some patients. In the treatment of PHG, pharmacological (e.g. propranolol), surgical (e.g. portosystemic shunt) and radiological (e.g. transjugular intrahepatic portosystemic shunt) procedures may be useful in preventing bleeding from PHG.

Portal Hypertensive gastropathy

The term portal hypertensive gastropathy (PHG) defines a wide spectrum of diffuse macroscopic lesions that appear in the gastric mucosa of patients with portal hypertension. Histologically, these lesions correspond to dilated vessels in the mucosa and submucosa in the absence of erosions or inflammation. Endoscopically, the lesions are classified as mild when mosaic pattern or superficial reddening are present, and severe when gastric mucosa appear with diffuse cherry red spots. Mild lesions are highly prevalent (65-90%), whereas severe lesions are present in only 10-25% of cirrhotic patients. The pathogenesis of PHG is not well known, but both venous congestion related with raised portal pressure and increased gastric blood flow seem to be crucial factors for its development. Variceal sclerosis may contribute to the development or aggravation of the lesions. Bleeding is the unique clinical manifestation of PHG, and occurs only in those patients with severe lesions. During a 5-year follow-up, the risk of overt bleeding or chronic bleeding, which induces anaemia, is 60 % and 90%, respectively, for patients with severe PHG. Propranolol is the only pharmacological treatment that has been proven useful in preventing bleeding from PHG. Porto-systemic shunts and liver transplantation are also effective.

Helicobacter pylori infection in congestive gastropathy

BACKGROUND

This study determines the prevalence and significance of Helicobacter pylori infection in portal hypertensive patients.

MATERIALS AND METHODS

Patients numbered 118 and consisted of 90 patients with portal hypertension (66 men; 24 women; mean age, 49.1 +/- 2.1 years) and 28 noncirrhotic patients with nonulcer dyspepsia, (12 men; 16 women; mean age, 47.6 +/- 2.8 years), who made up the control group. In all patients, diagnostic upper endoscopy was performed, and gastric biopsies were taken for histological examination and diagnosis of H. pylori.

RESULTS

Of the portal hypertensive patients, 42 (47%) had congestive gastropathy, 11 (26%) of whom were positive for H. pylori, and 48 (53%) did not have gastropathy, 12 (25%) of whom were positive for H. pylori. In the control group, 15 of 28 (54%) were positive for H. pylori. H. Pylori was found less frequently in congestive gastropathy patients than in the control group. We found also that the presence and severity of congestive gastropathy is independent of H. pylori status.

CONCLUSIONS

We conclude that the role of H. pylori in the pathogenesis of congestive gastropathy is unlikely, and we suggest that there is no need for its routine eradication in cirrhotic patients.

Weakness of mucosal barrier in portal hypertensive gastropathy of alcoholic cirrhosis. Effects of propranolol and enprostil

BACKGROUND/AIMS

It has been suggested that the vulnerability of gastric mucosa is increased in patients with cirrhosis as a result of a PGE2 deficiency. Therefore, we evaluated whether PGE2 mucosal generation, and gastric potential difference - a reflection of the gastric mucosal barrier - were correlated to endoscopic features and whether these alterations could be alleviated.

METHODS

The potential difference was measured before (basal) and after a stimulation test by aspirin. The serum levels of gastrin and glucagon were also determined. Finally, the effects of a 1-week administration of propranolol or enprostil were tested on potential difference. The endoscopic grade of portal hypertensive gastropathy was assessed according to McCormack et al. The results are presented respectively for controls, patients with mild gastropathy, and patients with severe gastropathy. Comparisons were made using variance or covariance analysis after adjustment with age.

RESULTS

Basal potential difference was significantly different between the three groups: -30.6, -28.8, -24.9 mV, p <0.05, respectively. The effects of aspirin administration on potential difference parameters were significantly different between the three groups (irritability index: 35 +/- 25, 92 +/- 98, 114 +/- 74 mV2.min, p <0.05, respectively) when non-responders to aspirin were excluded. PGE2 mucosal generation was significantly increased in both the antrum (9.8, 19.5, 19.7 ng/mg proteins, p<0.05, respectively) and in the corpus (8.1, 14.0, 20.2 ng/mg proteins, p<0.05, respectively). PGE2 generation was not related to potential difference. Glucagon serum levels were related to the grade of gastropathy. A 1-week administration of 160 mg/d long-acting propranolol, 35 micro g/d enprostil or placebo did not significantly modify basal potential difference.

CONCLUSIONS

Portal hypertensive gastropathy is characterized by a decreased potential difference proportional to the endoscopic severity. The gastric mucosa of patients with cirrhosis seems to be more susceptible to aspirin than that of healthy subjects. It appears that the role of PGE2 is controversial in portal hypertensive gastropathy. Propranolol and enprostil do not improve this decreased potential difference.

Time-course changes in gastric mucosal blood perfusion following portal vein constriction in rats

BACKGROUND/AIMS

Gastric mucosal blood flow is increased in all experimental models of chronic portal hypertension, when portosystemic shunting and the hyperdynamic circulation are fully developed. However, some controversy exists concerning the time course of this event. This study was undertaken to investigate the chronological changes in gastric mucosal blood perfusion during the first 7 days after partial portal vein constriction.

METHODS

Portal hypertensive and sham operated animals were studied. Gastric mucosal blood flow was measured by hydrogen-gas clearance and gastric oxygen and hemoglobin content by reflectance spectrophotometry, prior to and immediately after partial portal vein constriction, and 1, 2, 7 and 15 days after induction of portal hypertension.

RESULTS

Immediately after partial portal vein constriction, gastric mucosal blood flow and gastric oxygen were significantly decreased by 27% and 32% respectively, and gastric hemoglobin significantly increased by 19%. On day 1, gastric mucosal blood flow was increased in both portal hypertensive and sham operated rats. However, while this parameter returned to normal in sham operated rats, it remained high on days 2, 7 and 15 in portal hypertensive rats. In portal hypertensive rats, gastric oxygen values were not significantly different from those in sham operated animals, but hemoglobin tended to increase with development of portal hypertension, being significantly higher than in sham operated rats at days 2 and 7. Similar results were obtained when analyzing gastric mucosal blood perfusion 2 and 7 days after two-staged total portal vein constriction.

CONCLUSIONS

Increased gastric mucosal blood perfusion is present in portal hypertensive rats from the first day after partial portal vein constriction. The lack of significant differences in all parameters on day 1 between portal hypertensive and sham operated rats is probably related to an increased mucosal blood perfusion related to surgery.

Gastric microcirculatory changes of portal-hypertensive rats can be attenuated by long-term estrogen-progestagen treatment

It has been suggested that estrogen-progestagen therapy may be useful in preventing bleeding from gastric angiodysplasia, a vascular lesion similar to that described in portal-hypertensive gastropathy. In this study we assessed the effects of estrogen-progestagen therapy on gastric microcirculation and systemic and splanchnic hemodynamics in portal-hypertensive and sham-operated rats. One week after the surgical procedure (partial portal vein ligation or sham surgery), animals were given an intramuscular injection of a slow-release preparation of estrogen-progestagen or its vehicle. Two weeks later, gastric mucosal blood flow was measured by means of hydrogen gas clearance, a morphometrical analysis of gastric mucosal blood vessels was performed and systemic and splanchnic hemodynamics were evaluated with a radiolabeled-microspheres technique. In portal-hypertensive rats, estrogen-progestagen therapy induced a significant reduction in gastric mucosal blood flow, number of blood vessels and relative area of vessels. Similar changes, although of lesser magnitude, were achieved with estrogen or progestagen given separately and with the low dose of combined estrogen-progestagen. Estrogen-progestagen treatment also induced significant reductions in portal pressure and porto-collateral resistance without changing systemic or splanchnic hemodynamics. In contrast, estrogen-progestagen treatment did not induce changes in any of the parameters studied in sham-operated rats. We conclude that long-term estrogen-progestagen therapy reduces the gastric hyperemia, increased mucosal vessel density and portal pressure in portal-hypertensive rats.

Effects of propranolol on gastric mucosal perfusion and serum gastrin level in cirrhotic patients with portal hypertensive gastropathy

Gastric mucosal hyperemia associated with elevated serum gastrin level has been suggested in cirrhotic patients with portal hypertensive gastropathy (PHG). Clinical evidence has shown that these patients may benefit from propranolol administration. The aim of this study was to investigate effect of propranolol on gastric mucosal perfusion and serum gastrin level in cirrhotic patients with portal hypertensive gastropathy. Gastric mucosal perfusion was assessed by laser Doppler flowmetry. Measurements were performed under basal conditions and after observer-blind administration of propranolol (30-60 mg/day, N = 9) or placebo (N = 9) for seven days. Placebo had no effect on either gastric mucosal perfusion or serum gastrin level. In contrast, propranolol administration significantly decreased both antrum gastric mucosal perfusion (from 0.88 +/- 0.28 to 0.73 +/- 0.26 V, P < 0.05) and corpus gastric mucosal perfusion (from 0.94 +/- 0.35 to 0.78 +/- 0.25 V, P < 0.05). However, this drug had no effect on serum gastrin level. We conclude that chronic propranolol administration in cirrhotic patients with portal hypertensive gastropathy may reduce gastric mucosal perfusion without changing serum gastrin level.

Effect of bolus injection and continuous infusion of somatostatin on gastric perfusion in cirrhotic patients with portal-hypertensive gastropathy

Gastric perfusion has been found to be increased in cirrhotic patients with portal-hypertensive gastropathy. This phenomenon may contribute to gastric bleeding from these lesions. Therefore drugs reducing gastric mucosal perfusion may be beneficial in the treatment of bleeding portal-hypertensive gastropathy. In this study, gastric mucosal perfusion was assessed, by means of laser-Doppler flowmetry and reflectance spectrophotometry, in 36 cirrhotic patients with portal-hypertensive gastropathy in basal conditions and after double-blind administration of placebo or somatostatin. Intravenous bolus injection of 250 micrograms somatostatin induced a rapid, marked decrease in gastric perfusion (-31.6% +/- 7.9%, p < 0.05), as assessed on laser-Doppler flowmetry, that lasted for only 6 min. Changes in the hemoglobin content of the gastric mucosa paralleled those of laser-Doppler signal. The oxygen content of the gastric mucosa was mildly reduced (-6.9% +/- 1.1%, p < 0.05). When the bolus injection was followed by a continuous infusion of somatostatin, the reduction in gastric perfusion, as assessed by means of laser-Doppler flowmetry, was maintained, although the magnitude of the reduction (-17% +/- 7%) was significantly lower than that observed immediately after the bolus (p < 0.05); the hemoglobin content of the gastric mucosa was also significantly reduced (-8% +/- 1%), but no changes were observed in the oxygen content. Placebo administration had no effect on any of these parameters. We conclude that the increased gastric perfusion in cirrhotic patients with portal-hypertensive gastropathy can be effectively decreased by somatostatin administration.

Pharmacological treatment of portal hypertension: hemodynamic effects and prevention of bleeding

In the past 10 years, it has been clearly shown that vasoactive substances reduce portal pressure in patients or animals with portal hypertension. Some of these substances act by inducing splanchnic vasoconstriction, while others reduce hepatic and porto-systemic collateral vascular resistance and, thus, induce a portal hypotensive effect. Still others induce arterial hypotension, which causes a vasoconstrictive effect in the splanchnic territory. Since these drugs act on different vascular receptors, their combination should have a more marked effect on portal hypertension. Up to now, only nonselective beta-blockers have been used in the prevention of first gastrointestinal bleeding in patients with portal hypertension and esophageal varices and in the prevention of recurrent gastrointestinal bleeding. These trials have shown that propranolol or nadolol significantly reduce either a first episode of bleeding or recurrent bleeding. This pharmacological treatment also improves the survival rate in these patients. All of these studies have helped us to understand, in part, why gastrointestinal hemorrhage occurs in certain patients. Additional studies of beta-blockers or other substances are, nevertheless, necessary to select patients who will respond to this type of treatment. Finally, it is possible that the pharmacological treatment of portal hypertension may also be used before esophageal varices occur.

Reduction of gastric hyperemia by glypressin and vasopressin administration in cirrhotic patients with portal hypertensive gastropathy

Gastric mucosal perfusion is increased in portal-hypertensive gastropathy, and this may contribute to gastric bleeding from these lesions. Therefore drugs reducing gastric mucosal perfusion may be beneficial in the treatment of overt bleeding from portal-hypertensive gastropathy. In this study gastric mucosal perfusion was assessed in 28 cirrhotic patients with portal-hypertensive gastropathy under basal conditions and after double-blind intravenous administration of vasopressin (0.4 U/min), glypressin (2-mg injection) or placebo, with laser-Doppler flowmetry and reflectance spectrophotometry. Vasopressin and glypressin induced a significant increase in blood pressure and a decrease in heart rate. These effects were more pronounced in the vasopressin group. Both vasopressin and glypressin induced a sustained and similar reduction in gastric mucosal perfusion as assessed by laser-Doppler flowmetry (-36% +/- 8% and -34% +/- 6%, respectively; p < 0.05 with respect to basal values and with respect to the control group), whereas placebo had no effect. Both drugs significantly reduced the oxygen content of the gastric mucosa; however, the impairment in mucosal oxygenation was greater (p < 0.05) in the vasopressin group (-17% +/- 3%) than in the glypressin group (-6% +/- 0.1%). We conclude that the increased gastric perfusion in cirrhotic patients with portal-hypertensive gastropathy may be reduced by either vasopressin or glypressin. These findings support the use of these drugs in clinical trials treating bleeding portal-hypertensive gastropathy. The lower reduction in gastric mucosal oxygen content observed with glypressin could decrease the incidence of ischemic adverse events associated with the use of vasopressin.

Octreotide decreases canine gastric mucosal blood flow: a controlled assessment by endoscopic reflectance spectrophotometry

The aim of this study was to evaluate the effects of octreotide, a long-acting somatostatin analogue, on canine gastric mucosal blood flow and hemodynamics. We hypothesized that octreotide might decrease gastric mucosal blood flow without causing adverse hemodynamic effects. Two groups of dogs were anesthetized (six normal dogs and six dogs with prehepatic portal hypertension), and each dog was administered intravenous octreotide, normal saline solution, and vasopressin for 30 minutes on separate days in a blinded, randomized fashion. Vasopressin was included as treatment for a positive control. Gastric mucosal blood flow was assessed at the fundus, corpus, and antrum by endoscopic reflectance spectrophotometry. A femoral arterial catheter monitored systemic blood pressure and heart rate. Treatment responses for all observations were calculated for each dog as a percentage of baseline values. For mucosal blood flow, treatment responses did not differ significantly over time or between animal group or gastric location. Octreotide significantly decreased indices of hemoglobin concentration (-19%, p = 0.01) and oxygen saturation (-17%, p = 0.0002) compared to saline (-9% and -7%, respectively). The mean arterial pressure was increased after octreotide compared to saline (+23% versus +7%, p = 0.01), but octrotide had no effect on heart rate (+2% versus +1%). Vasopressin also decreased the indices of hemoglobin concentration (-34%) and oxygen saturation (-82%) significantly more than saline (p = 0.001). Vasopressin increased mean arterial pressure (+55%), but also caused reflex bradycardia (-22%) significantly more than saline (p = 0.001). We conclude that octreotide decreases canine gastric mucosal blood flow and appears to cause minimal hemodynamic changes.

Involvement of nitric oxide and prostaglandins in gastric mucosal hyperemia of portal-hypertensive anesthetized rats

This study investigates the effects of inhibition of nitric oxide synthesis by NG-nitro-L-arginine methyl ester (L-NAME), the inhibition of prostaglandin synthesis with indomethacin and the combined effects on gastric mucosal hyperemia of ketamine-anesthetized rats with portal hypertension induced by partial portal vein ligation. The hydrogen gas-clearance technique was used for measurement of gastric mucosal blood flow. Blood pressure increased with L-NAME administration in a similar manner in portal-hypertensive and sham-operated rats. Low doses of L-NAME (1 and 3 mg/kg, intravenously) caused a significant and dose-dependent reduction in gastric mucosal blood flow in portal-hypertensive rats but had no effect on sham-operated animals. With a higher dose of L-NAME (13 mg/kg, intravenously), a significant decrease in gastric mucosal blood flow was observed in both portal-hypertensive and sham-operated rats. Indomethacin pretreatment (5 mg/kg, subcutaneously) caused a significant decrease in basal gastric mucosal blood flow of portal-hypertensive rats but did not modify this parameter in sham-operated animals. In sham-operated rats pretreated with indomethacin, the lower dose of L-NAME (3 mg/kg) did not significantly modify basal gastric mucosal blood flow. Likewise, pretreatment with indomethacin in sham-operated rats did not augment the significant reduction in gastric mucosal blood flow produced by the higher dose of L-NAME. In portal-hypertensive rats the significant dose-dependent reduction in gastric mucosal blood flow induced by L-NAME (3 and 13 mg/kg) was not significantly altered by pretreatment with indomethacin.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastric secretion and peptic ulceration in cirrhosis

Stomach function and secretions are altered significantly in patients with cirrhosis, both with or without portal hypertension. This review covers the abnormalities of gastric acid and pepsin secretion, and gastrin release. Histological and endoscopic changes, and the impaired cytoprotection associated with cirrhosis, are discussed in the context of abnormal gastric secretion. In addition, the symptomatology and association of H. pylori, and treatment of duodenal ulceration in cirrhosis are discussed. It is clear from this review that additional studies are needed to further understand gastric function in cirrhotic patients.

Effects of propranolol on gastric mucosal perfusion in cirrhotic patients with portal hypertensive gastropathy

This study investigated the effects of the short-term administration of propranolol on gastric blood perfusion in cirrhotic patients with portal hypertensive gastropathy. Portal hypertensive gastropathy is a common cause of nonvariceal bleeding in cirrhosis, which is associated with increased gastric mucosal perfusion and is favorably influenced by propranolol therapy. Gastric mucosal perfusion was evaluated with laser-Doppler flowmetry and reflectance spectrophotometry. Measurements were performed under basal conditions and after the double-blind administration of propranolol (0.15 mg/kg intravenously) or placebo. Propranolol administration significantly reduced (p < 0.001) the laser-Doppler signal (2.93 +/- 0.23 vs. 2.25 +/- 0.22 V) and the hemoglobin content of the gastric mucosa (99.2 +/- 3.8 vs. 89.3 +/- 3.1 arbitrary units), whereas the oxygen content remained unchanged (37.4 +/- 1.2 vs. 36.9 +/- 1.0 arbitrary units). Placebo administration had no effect in any of these parameters. Changes in gastric perfusion after propranolol administration were associated with a significant decrease in hepatic venous pressure gradient and azygos blood flow. We conclude that short-term propranolol administration, in addition to lowering portal pressure, reduces the increased gastric blood perfusion in cirrhotic patients with portal hypertensive gastropathy, an effect that may contribute to prevention of bleeding from these lesions.

Increased gastric mucosal perfusion in cirrhotic patients with portal hypertensive gastropathy

To characterize gastric mucosal perfusion in cirrhotic patients with portal hypertensive gastropathy, 34 cirrhotics with this lesion and 24 noncirrhotics were studied by reflectance spectrophotometry and laser-Doppler flowmetry during endoscopy. A significant correlation was observed between the hemoglobin content of the gastric mucosa, measured by reflectance spectrophotometry, and the serum hemoglobin concentration both in cirrhotics (r = 0.72) and in noncirrhotics (r = 0.87). IHb ratio (hemoglobin content of gastric mucosa divided by blood hemoglobin concentration) was higher in cirrhotics with portal hypertensive gastropathy than in noncirrhotics (P < 0.001), whereas the oxygen content of the gastric mucosa was similar in both groups. This pattern indicates that cirrhotics with portal hypertensive gastropathy have increased gastric perfusion without congestion. Gastric blood flow estimated by laser-Doppler was significantly higher in cirrhotics with portal hypertensive gastropathy than in noncirrhotics (P < 0.001). In cirrhotic patients, gastric areas with cherry red spots showed a significantly higher IHb ratio than areas with a mosaic or scarlatina pattern (P < 0.05). The magnitude of changes in gastric perfusion and the endoscopic severity of portal hypertensive gastropathy had no relationship with the degree of portal hypertension or the azygos blood flow.

Hepatic, splanchnic and systemic haemodynamic abnormalities in portal hypertension

Portal hypertension is characterized by a pathological increase in portal venous pressure that leads to the formation of portosystemic collaterals that divert portal blood to the systemic circulation, bypassing the liver. Increased vascular resistance to portal blood flow is the initiating factor in portal hypertension. Increased resistance along the hepatic and portocollateral circulation is in part modifiable by pharmacological agents. An additional factor is splanchnic vasodilatation with increased portal blood inflow, which contributes to the maintenance and aggravation of the portal hypertension. Endogenous vasodilators are thought to be responsible for the splanchnic hyperaemia of portal hypertension. Vasodilatation is also prominent in the stomach and lungs, and plays an important role in the pathophysiology of portal hypertensive gastropathy and of the hepatopulmonary syndrome. The systemic circulation is markedly hyperkinetic, with reduced arterial pressure and peripheral resistance and increased cardiac output. The plasma volume is expanded due to renal sodium retention. The expanded plasma volume enables the increase in cardiac output, and represents another mechanism contributing to the increase in portal pressure.

Effects of inhibiting nitric oxide biosynthesis on the systemic and splanchnic circulation of rats with portal hypertension

1. The effects of inhibiting endogenous nitric oxide (NO) synthesis with NG-monomethyl-L-arginine (L-NMMA) on the systemic and splanchnic circulation have been investigated in rats with experimental chronic portal hypertension, anaesthetized with ketamine. 2. Portal hypertension was induced by partial portal vein ligation, 2 weeks prior to study. This procedure induced a reduction in systemic arterial blood pressure (MAP), an increase in cardiac output as measured by radiolabelled microspheres, a reduction in peripheral and splanchnic vascular resistance and an increased portal venous inflow (PVI) and portal pressure, as compared to control non-ligated rats. 3. L-NMAA (6.25 and 50 mg kg-1, i.v.) dose-dependently increased MAP, reduced cardiac output and PVI, and increased peripheral and splanchnic vascular resistance. With L-NMMA (50 mg kg-1), PVI and the vascular resistances returned to values comparable to those determined in control non-ligated anaesthetized rats under resting conditions. 4. Porto-collateral resistance was also increased by these doses of L-NMMA, whereas portal pressure was unchanged. The increase in renal blood flow and decrease in renal vascular resistance also seen in portal-hypertensive rats was reversed by L-NMMA (50 mg kg-1). 5. These effects of L-NMMA (50 mg kg-1) were inhibited by prior administration of L-arginine (300 mg kg-1, i.v.). 6. These findings indicate that the chronic hyperdynamic circulatory characteristics following portal vein stenosis can be attenuated by L-NMMA. Thus, the excessive formation of endogenous NO may be implicated in the pathogenesis of the haemodynamic disturbances and splanchnic vasodilatation associated with chronic portal hypertension.

Propranolol in prevention of recurrent bleeding from severe portal hypertensive gastropathy in cirrhosis

The two main causes of gastrointestinal bleeding in cirrhosis are oesophageal varices and portal hypertensive gastropathy (PHG). Rebleeding from varices can be prevented by beta-blockers, but it is not clear whether these drugs effectively reduce rebleeding from PHG. 54 cirrhotic patients with acute or chronic bleeding from severe PHG took part in a randomised, controlled trial to investigate the efficacy of propranolol in prevention of rebleeding from PHG. 26 patients were randomised to receive propranolol daily at a dose that reduced the resting heart rate by 25% or to 55 bpm (20-160 mg twice daily), throughout mean follow-up of 21 (SD 11) months. 28 untreated controls were followed-up, with the same examinations, for 18 (13) months. The actuarial percentages of patients free of rebleeding from PHG were significantly higher in the propranolol-treated patients than in the untreated controls at 12 months (65% vs 38%; p less than 0.05) and at 30 months of follow-up (52% vs 7%; p less than 0.05). Propranolol-treated patients had fewer episodes of acute bleeding than controls (0.010 [0.004] vs 0.120 [0.040] per patient per month). Multivariate analysis showed that absence of propranolol treatment was the only predictive variable for rebleeding. Actuarial survival was slightly higher in the propranolol group than in the controls, but the difference was not significant. Thus, long-term propranolol treatment significantly reduces the frequency of rebleeding from severe PHG, and may improve the prognosis of cirrhotic patients with this disorder.