Hyperdynamic circulation of liver disease 40 years later: pathophysiology and clinical consequences

Endothelial calcium-calmodulin dependent nitric oxide synthase in the in vitro vascular hyporeactivity of portal hypertensive rats

BACKGROUND/AIMS

Increased nitric oxide production has been implicated in impaired vascular responsiveness to vasoconstrictors in portal hypertension. However, there is no firm evidence concerning the involved nitric oxide synthase isoform. The present study investigated the possible contribution of one nitric oxide synthase isoform, the endothelial constitutive Ca2+-calmodulin dependent, in the overproduction of nitric oxide in portal hypertension.

METHODS

Vascular responses to norepinephrine and acetylcholine were evaluated in isolated thoracic aortic rings from normal and portal vein stenosed rats.

RESULTS

An impaired concentration-dependent contraction to norepinephrine was observed in intact rings from portal hypertensive rats compared to controls. The hyporeactivity to norepinephrine was reversed after endothelium denudation, the inhibition of nitric oxide synthase with L-NOARG or the inhibition of calmodulin with W-7, but not after pre-incubation with indomethacin. Stimulation of intact rings with norepinephrine after the inhibition of calmodulin with calmidazolium was followed by a decreased vascular response in vessels from normal rats but not in those from portal hypertensive rats. Stimulation of intact rings with norepinephrine in a Ca2+-free medium was followed by a decreased vascular response in vessels from both portal hypertensive and normal rats. No difference in vasoconstrictive responses was observed between the two groups after calmidazolium or in a Ca2+-free medium. Relaxation induced by acetylcholine in norepinephrine-precontracted rings was more marked in rings from portal hypertensive rats than in controls. No differences in the vasodilator responses were observed after relaxations had been inhibited by the removal of the endothelium, pre-incubation with L-NOARG, indomethacin, W-7 or calmidazolium and in a Ca2+-free medium.

CONCLUSIONS

This study demonstrates the involvement of the endothelial constitutive Ca2+-calmodulin dependent nitric oxide synthase isoform in the overproduction of nitric oxide in portal hypertension.

Cardiovascular status after postural change in compensated cirrhosis: an argument for vasodilatory concept

It seems that hypervolemia and vasodilatation coincide in compensated cirrhosis, but neither rank nor importance of these factors has been fully clarified in adaptive response to postural change. We studied, with gated equilibrium radionuclide angiography and thoracic electrical bioimpedance the hemodynamic status of 19 patients with compensated cirrhosis and 18 healthy subjects in upright and supine positions. In the upright position, the cirrhotic patients were hypotensive and had decreased peripheral vascular resistance despite increased cardiac output. The transition to the supine position was accompanied by a significant fall in the heart rate and an increase in the stroke volume in both controls (92 +/- 22 to 63 +/- 10 beats/min, and 38 +/- 9 to 62 +/- 19 ml/m2, respectively) and cirrhotic patients (101 +/- 20 to 79 +/- 13 beats/min, and 44 +/- 15 to 63 +/- 19 ml/m2, respectively). Besides, the diastolic arterial pressure fell in controls from 89 +/- 9 mmHg to 81 +/- 11 mmHg; p < 0.01, while it remained unchanged in cirrhotic patients (77 +/- 17 vs 82 +/- 13 mmHg). In the supine position, the cirrhotic patients presented tachycardia and left ventricular hyperkinesy (increased velocity of left ventricular filling and emptying). In conclusion, these results show that in compensated cirrhosis the decreased arterial tone and peripheral blood pooling are important factors of adaptive hemodynamic reaction to postural change.

Hyperdynamic circulation in patients with cirrhosis: direct measurement of nitric oxide levels in hepatic and portal veins

BACKGROUND/AIMS

Peripheral vasodilation represents the main vascular dysfunction associated with the hyperdynamic circulation of liver cirrhosis. This study was intended to measure directly regional and systemic levels of nitric oxide, a potent vasorelaxing mediator, in order to assess its role in the development of hemodynamic changes of cirrhosis.

METHODS

We compared nitric oxide levels in the splanchinic and systemic circulation of 25 patients with cirrhosis undergoing transjugular intrahepatic portosystemic stent shunt and in the hepatic vein and peripheral blood of 10 patients without cirrhosis submitted to venous catheterization. Nitric oxide levels were measured through electron paramagnetic resonance spectroscopy as nitrosylhemoglobin complexes.

RESULTS

Significantly higher nitric oxide levels were calculated in patients with cirrhosis with respect to controls, both in the peripheral and hepatic veins. In patients with cirrhosis, nitric oxide levels in the portal vein (3.44 +/- 2.17, expressed in arbitrary units) were higher than in the systemic circulation (1.89 +/- 1.15), but lower than in the hepatic vein (4.75 +/- 2.53; p < 0.001 by variance analysis).

CONCLUSIONS

These data suggest that nitric oxide synthetic pathway activity as well as nitric oxide release are enhanced at the level of splanchnic vasculature and, more important, in the hepatic tissue, confirming evidence of the predominant role of nitric oxide in the pathogenesis of hemodynamic changes in patients with cirrhosis with portal hypertension.

Nitric oxide synthase activity in arterial tissues of cirrhotic rats

The changes in the activities of constitutive nitric oxide (NO) synthase (cNOS) and inducible NOS (iNOS) were investigated in arterial tissues of CCl4-induced cirrhotic adult SD rats. The aortic tissue homogenate were prepared in normal and cirrhotic rats. NOS activity was measured by conversion of 3H-arginine to 3 H-citrulline. The activities of cNOS and iNOS were calculated in terms of presence or absence of Ca2+. The results showed that activities of total NOS, cNOS and iNOS in arterial tissues were all increased significantly in cirrhotic rats as compared with those in normal controls. There was a significant positive correlation between the activities of total NOS and cGMP content in cirrhotic arterial tissues.

Changes in plasma endothelin-1 and Big endothelin-1 induced by transjugular intrahepatic portosystemic shunts in patients with cirrhosis and refractory ascites

BACKGROUND/AIMS

Endothelin-1 (ET-1) is a potent vasoconstrictor that may be involved in the pathogenesis of splanchnic and renal hemodynamic changes associated with portal hypertension. The aim of this study was to measure the concentration of ET-1 and of its precursor Big endothelin-1 (Big ET-1) in the systemic circulation as well as in the splanchnic and renal venous beds and to evaluate changes after the relief of portal hypertension following transjugular intrahepatic portosystemic shunt placement.

METHODS

Plasma concentrations of ET-1 and of Big ET-1 were measured in the vena cava, renal vein, hepatic vein and portal vein in ten patients with cirrhosis and refractory ascites before and 1-2 months after transjugular intrahepatic portosystemic shunt. The porto-caval gradient, creatinine clearance, plasma aldosterone and renin activity, as well as daily urinary sodium excretion were measured at the same time.

RESULTS

The plasma concentration of ET-1 and Big ET-1, respectively, in peripheral blood of normal volunteers were 0.28 +/- 03 and 3.95 +/- 0.34 pg/ml; the concentrations of both peptides were higher in patients with cirrhosis, both in vena cava (0.61 +/- 0.14 and 10.01 +/- 1.47 pg/ml), hepatic vein (0.62 +/- 0.13 and 13.93 +/- 1.77 pg/ml), portal vein (1.21 +/- 0.12 and 17.84 +/- 1.98 pg/ml) and renal vein (0.76 +/- 0.12 and 14.21 +/- 1.55 pg/ml). Moreover ET-1 and Big ET-1 concentrations were more elevated in the portal vein than in the vena cava (+98% and +70%) and slightly higher in the renal vein as compared to the vena cava (+25% and +42%). After transjugular intrahepatic portosystemic shunt, a rise in creatinine clearance and urinary sodium excretion (+49%; and +53%) was observed together with a marked reduction in plasma aldosterone and renin activity (-59% and -49%). ET-1 and Big ET-1 concentrations remained unchanged in the vena cava whereas a significant reduction of ET-1 and Big ET-1 occurred both in the portal vein (-43% and -44%) and in the renal vein (-53% and -29%). Portal vein and renal vein concentrations of both peptides became similar to vena cava levels.

CONCLUSIONS

Splanchnic and renal hemodynamic changes occurring in patients with cirrhosis and refractory ascites could be related to the production of ET-1 by splanchnic and renal vascular beds. This was abolished by transjugular intrahepatic portosystemic shunt, which could explain the exacerbation of systemic vasodilation and the improvement in renal perfusion observed after the procedure.

Haemodynamic adaptation two months after transjugular intrahepatic portosystemic shunt (TIPS) in cirrhotic patients

BACKGROUND AND AIMS

In portal hypertensive patients, transjugular intrahepatic portosystemic shunt (TIPS) acutely increases cardiac output and exaggerates peripheral vasodilatation. It has been suggested that the worsened hyperdynamic state may progress to high output heart failure. The aim was to evaluate the acute and short-term haemodynamic adaptation to this procedure.

METHODS

Systemic, splanchnic, and pulmonary haemodynamics were studied in 15 cirrhotic patients under stable haemodynamic conditions before placement of TIPS, then 15-30 minutes after and two months later. For inclusion in the final analysis, an uneventful post-TIPS at two months follow up and a stable portacaval gradient were required. The following variables were measured or calculated: portacaval gradient; cardiac index (thermodilution); systolic and diastolic mean arterial, atrial, pulmonary arterial, and wedged pulmonary capillary pressures; heart rate; and total peripheral and pulmonary vascular resistances. Blood flow in the shunt was measured using duplex Doppler ultrasound.

RESULTS

The portacaval gradient decreased by 56% and remained stable thereafter. Shunt blood flow was unchanged when measured immediately after TIPS and two months later. Immediately after TIPS there was a pronounced increase in cardiac index (+32%; p < 0.05) in association with a decrease in peripheral and pulmonary vascular resistance (-21%; p < 0.05 and -14%; NS). Two months later, whereas the initial rise in cardiac index was attenuated, peripheral vascular resistances remained similar and pulmonary vascular resistances decreased further (-33%; p < 0.05) compared with immediate post-TIPS values.

CONCLUSIONS

Hyperdynamic circulation worsened immediately after TIPS, with a progressive adaptation during follow up. The mechanisms of post-TIPS induced haemodynamic changes include an abrupt volume load resulting from splanchnic decompression and an increased delivery of gut derived vasodilators to the systemic circulation. The persistence of decreased peripheral and pulmonary vascular resistances despite the reduction in high cardiac output two months after TIPS suggests that vasodilatation is not solely a compensatory response to a TIPS induced increased preload. Vasodilatory substances shunted away from the liver probably play an important part in this phenomenon.

Pathophysiology and treatment of variceal hemorrhage

Portal hypertension results from increases in portal flow and portal vascular resistance. Factors increasing portal blood flow are predominantly humoral. Resistance to portal flow has a fixed component due to distortion of the vasculature by cirrhotic nodules and a variable component that is related to vasoactive substances. Varices result from an increase in portal pressure. Factors predicting the risk of variceal bleeding include continued alcohol use, poor liver function, large varices, and red wale markings on varices at endoscopy. Octreotide is probably the drug of choice for pharmacologic management of bleeding esophageal varices. Propranolol has an established role in the prevention of variceal hemorrhage, and variceal band ligation may be the preferred endoscopic technique. Transjugular intrahepatic portosystemic shunts have emerged as an important treatment for patients in whom pharmacologic and endoscopic therapies have failed and are an effective bridge to liver transplantation.

Platelet basal cytosolic calcium: the influence of plasma factors in cirrhosis

BACKGROUND

Platelet cytosolic calcium is necessary for normal platelet function, and may reflect intracellular signalling in vascular smooth muscle cells.

METHODS

The cytosolic calcium of platelets from patients with cirrhosis and control subjects was measured in contact with plasma from either source, using FURA 2AM.

RESULTS

The basal cytosolic calcium of patients with cirrhosis was found to be significantly lower than that of control subjects (95.7 +/- 10.0 cf. 128.0 +/- 7.8 nmol/l; p = 0.02). When platelets from control subjects were incubated for 45 min with freshly obtained plasma from patients with cirrhosis, the control platelet cytosolic calcium fell to concentrations similar to those of patient platelets (93.0 +/- 7.8 nmol/l; p < 0.005). Such an effect was not observed if patient serum or plasma that had previously been frozen was used. When patient platelets were incubated with fresh control subject plasma, the platelet cytosolic calcium increased (165.4 +/- 19.9 nmol/l; p = 0.01).

CONCLUSION

These results indicate that a plasma-borne factor, sensitive to freezing, is responsible for the abnormalities of platelet calcium signalling noted in cirrhosis.

Effect of oxygen inhalation on systemic, central, and splanchnic haemodynamics in cirrhosis

BACKGROUND/AIMS

Patients with cirrhosis exhibit a hyperdynamic circulation with increased cardiac output and low arterial blood pressure. The aim of the present study was to assess the effects of oxygen inhalation on systemic, central, and splanchnic haemodynamics and vasoactive systems in patients with cirrhosis (n = 19).

RESULTS

Spirometry was normal, but the carbon monoxide diffusing capacity (transfer factor) was significantly decreased, 18.8 ml.min-1.mmHg-1 (-32% of that predicted, p < 0.0001), and correlated significantly with the cardiac output (r = 0.78, p < 0.0005), plasma volume (r = 0.72, p < 0.001) and the central and arterial blood volume (r = 0.67, p < 0.005). After inhalation of 100% oxygen over a period of 20 min, the cardiac output decreased from 7.4 to 6.6 l/min (p < 0.0005), and the systemic vascular resistance increased from 980 to 1124 dyn.s.cm-5 (p < 0.005). The change in systemic vascular resistance was significantly greater in patients with mild liver dysfunction than in those with severe liver dysfunction (p < 0.02). In contrast, no significant changes were seen in the arterial or portal venous pressures during inhalation of oxygen. Arterial concentrations of catecholamines, renin, endothelin-1, and calcitonin gene-related peptide were all increased in patients with cirrhosis, but only the catecholamine concentrations decreased significantly (noradrenaline -13%, p < 0.02 and adrenaline -16%, p < 0.01) in response to oxygen.

CONCLUSION

During oxygen inhalation cardiac output decreases and systemic vascular resistance increases in association with a decrease in arterial concentrations of catecholamine, but oxygen supply in patients with cirrhosis does not normalise the hyperdynamic circulation or the low arterial blood pressure.

Relation of calcitonin gene-related peptide to systemic vasodilatation and central hypovolaemia in cirrhosis

BACKGROUND

The aetiology of the reduced systemic vascular resistance and abnormal 'filling' of the vascular bed in cirrhosis is still obscure. As increased concentrations of the potent vasodilator calcitonin gene-related peptide (CGRP) have recently been reported in cirrhosis, we related CGRP to central and peripheral haemodynamics in patients with cirrhosis.

METHODS

Thirty-one cirrhotic patients and six control subjects underwent an investigation with determination of systemic haemodynamics and circulating CGRP.

RESULTS

Circulating CGRP was significantly increased in patients with cirrhosis (P < 0.02) and covaried directly with the severity of cirrhosis (P < 0.02). The increased CGRP covaried negatively with the reduced systemic vascular resistance (P < 0.02), the reduced central blood volume (P < 0.01), and reduced central circulation time (P < 0.002) and positively with the non-central blood volume (P < 0.05).

CONCLUSIONS

These results suggest that increased CGRP may play a role in the systemic vasodilatation in cirrhosis and may contribute to the abnormal distribution of the blood volume, which may lead to abnormal sodium and water handling.

Portal vascular responsiveness to sympathetic stimulation and nitric oxide in cirrhotic rats

AIMS/METHODS

The modulatory role of nitric oxide in portal vasoconstrictor responses was investigated in the isolated perfused liver of cirrhotic rats (induced by carbon tetrachloride/phenobarbitone; n = 6). Age-matched (n = 5) and phenobarbitone-treated rats (n = 5) served as controls.

RESULTS

At a constant flow rate of 5 ml/min there was no difference in basal perfusion pressure between the groups. Responses to electrical field stimulation of perivascular nerves caused frequency-dependent increases in perfusion pressure that were not significantly different between the groups. In contrast, dose-dependent vasoconstrictor responses to bolus injections of noradrenaline were up to two-fold greater than those observed in controls (p < 0.05). Vasoconstrictor responses to bolus injections of methoxamine (a selective alpha 1-adrenoceptor agonist) or adenosine 5'-triphosphate (ATP, a cotransmitter with noradrenaline in sympathetic nerves) were dose-dependent and similar between the groups. Infusion of the nitric oxide synthesis inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 30 microM) had no effect on basal tone or on responses to electrical field stimulation or injected agents. A step-wise increase in flow to 10, 15 and 20 ml/min produced a similar increase in perfusion pressure within each group. At increased flow, there was a decrease in responsiveness to noradrenaline (5 nmol) in preparations from all groups. In the presence of the K+ channel inhibitor glibenclamide (5 microM), the effect of noradrenaline in the cirrhotic group at flow rates of 5, 10 and 15 ml/min was maintained to a significantly greater extent than in either control group, suggesting that ATP-sensitive K+ channels in the portal venous bed may be activated in cirrhosis.

CONCLUSIONS

We conclude that portal vasoconstriction associated with noradrenaline, but not with sympathetic nerve stimulation, methoxamine or ATP, is enhanced in cirrhosis. Nitric oxide does not appear to play a modulatory role in these responses.

Cardiac modifications occurring in the ascitic rat with biliary cirrhosis are nitric oxide related

BACKGROUND/AIMS

Although the cardiac output is increased in liver cirrhosis, some degree of cardiac failure could coexist as suggested by human investigations showing cardiac enlargement in cirrhosis and by animal studies describing a limited response to fluid loading in the cirrhotic rat. Endotoxemia induces similar hemodynamic changes during the septic shock. This septic cardiomyopathy has been attributed to an increased secretion of nitric oxide by the myocytes. In this study, we aimed to verify if cirrhotic cardiomyopathy was present in the rat with biliary cirrhosis, and if it could be related to abnormal nitric oxide secretion.

METHODS

We therefore compared the coronary pressure, the systolic ventricular pressure and the peak rate of rise of the left ventricular pressure obtained from isolated hearts perfused with a modified Langendorff apparatus in control rats and in cirrhotic rats obtained by bile duct ligation. The variations occurring after inhibition of nitric oxide synthesis by the addition of NG monomethyl-L-arginine (10(-6)M) to the perfusing Krebs-Ringer solution were also studied in both groups.

RESULTS

We found that the coronary pressure and the contractility of the cirrhotic hearts decreased significantly when compared to the controls. Inhibition of the nitric oxide synthesis increased those values significantly when the hearts were obtained from cirrhotic animals. This was not observed in the control group.

CONCLUSIONS

Our data suggest that the cardiac modifications induced by the cirrhosis in the studied parameters are related to nitric oxide.

The hepatorenal syndrome

Hepatorenal syndrome may occur in any form of severe liver disease. It appears less common in children than adults, but still carries a poor prognosis. There are several factors involved in its aetiology, including a decreased renal perfusion pressure, activation of the renal sympathetic nervous system and increased synthesis of several vasoactive mediators, which may modulate glomerular filtration by acting as both renal vasoconstrictors and dynamic regulators of the glomerular capillary ultrafiltration coefficient, through their action on mesangial cells. This review will discuss the pathophysiology of the hepatorenal syndrome and some of the principles of management of patients with renal failure and severe liver disease. The role of renal support and liver transplantation will also be covered.