Variability of atrial natriuretic peptide plasma levels in ascitic cirrhotics: pathophysiological and clinical implications

Splanchnic vasodilation and hyperdynamic circulatory syndrome in cirrhosis

Portal hypertension is a clinical syndrome which leads to several clinical complications, such as the formation and rupture of esophageal and/or gastric varices, ascites, hepatic encephalopathy and hepato-renal syndrome. In cirrhosis, the primary cause of the increase in portal pressure is the enhanced resistance to portal outflow. However, also an increase in splanchnic blood flow worsens and maintains portal hypertension. The vasodilatation of arterial splanchnic vessels and the opening of collateral circulation are the determinants of the increased splanchnic blood flow. Several vasoactive systems/substances, such as nitric oxide, cyclooxygenase-derivatives, carbon monoxide and endogenous cannabinoids are activated in portal hypertension and are responsible for the marked splanchnic vasodilatation. Moreover, an impaired reactivity to vasoconstrictor systems, such as the sympathetic nervous system, vasopressin, angiotensin II and endothelin-1, plays a role in this process. The opening of collateral circulation occurs through the reperfusion and dilatation of preexisting vessels, but also through the generation of new vessels. Splanchnic vasodilatation leads to the onset of the hyperdynamic circulatory syndrome, a syndrome which occurs in patients with portal hypertension and is characterized by increased cardiac output and heart rate, and decreased systemic vascular resistance with low arterial blood pressure. Understanding the pathophysiology of splanchnic vasodilatation and hyperdynamic circulatory syndrome is mandatory for the prevention and treatment of portal hypertension and its severe complications.

Vasoactive factors and hemodynamic mechanisms in the pathophysiology of portal hypertension in cirrhosis

Portal hypertension is primarily caused by the increase in resistance to portal outflow and secondly by an increase in splanchnic blood flow, which worsens and maintains the increased portal pressure. Increased portal inflow plays a role in the hyperdynamic circulatory syndrome, a characteristic feature of portal hypertensive patients. Almost all the known vasoactive systems/substances are activated in portal hypertension, but most authors stress the pathogenetic role of endothelial factors, such as COX-derivatives, nitric oxide, carbon monoxide. Endothelial dysfunction is differentially involved in different vascular beds and consists in alteration in response both to vasodilators and to vasoconstrictors. Understanding the pathogenesis of portal hypertension could be of great utility in preventing and curing the complications of portal hypertension, such as esophageal varices, hepatic encephalopathy, ascites.

Spironolactone alone or in combination with furosemide in the treatment of moderate ascites in nonazotemic cirrhosis. A randomized comparative study of efficacy and safety

BACKGROUND/AIMS

The most rational treatment of moderate ascites is spironolactone alone or in combination with furosemide. However, it is unknown which of these two treatment schedules is preferable.

METHODS

One hundred nonazotemic cirrhotic patients with moderate ascites were randomly assigned to be treated with spironolactone and furosemide (Group 1: 50 patients) or with spironolactone alone (Group 2: 50 patients). If no response was obtained, the doses of diuretics were increased up to 400 mg/day of spironolactone and 160 mg/day of furosemide. In patients of group 2 not responding to 400 mg/day of spironolactone, furosemide was added. In cases with an excessive response, the dosage of diuretics was reduced.

RESULTS

The response rate (98% in Group 1 vs. 94% in Group 2), the rapidity of ascites mobilization and the incidence of complications induced by diuretic therapy was similar in both groups. The need to reduce the diuretic dosage was significantly higher in Group 1 than Group 2 (68% vs. 34%; P=0.002).

CONCLUSIONS

In the treatment of moderate ascites, spironolactone alone seems to be as safe and effective as spironolactone associated with furosemide. Since spironolactone alone requires less dose adjustment, it would be more suitable for treating ascites on an outpatient basis.

Increased activity of guanosine 3'-5'-cyclic monophosphate phosphodiesterase in the renal tissue of cirrhotic rats with ascites

A possible defect of guanosine 3'-5'-cyclic monophosphate (cGMP) content in the renal tissue caused by an increased activity of cGMP phosphodiesterase (PDE) has, so far, not been evaluated in the pathogenesis of renal resistance to endogenous natriuretic peptides (ENP) in cirrhosis with ascites. To test this hypothesis the activity of cGMP-PDE and the concentration of cGMP were evaluated in vitro in the renal tissue of 10 control rats and 10 cirrhotic rats with ascites before and after the intravenous (IV) administration of Zaprinast (Sigma, St. Louis, MO), a specific cGMP-PDE inhibitor (30 microgram/kg/min). Moreover, the effects of the intravenous administration of Zaprinast (15 microgram/kg/min and 30 microgram/kg/min) on renal plasma flow (RPF), glomerular filtration rate (GFR), and urinary sodium excretion (U(Na)V) were evaluated in 10 conscious control rats and 10 conscious cirrhotic rats with ascites. The effects of Zaprinast on plasma renin activity (PRA) was also evaluated in 10 control rats and in 10 cirrhotic rats with ascites. Finally, the effect of Zaprinast on RPF, GFR, and U(Na)V were evaluated in 10 cirrhotic rats after the IV administration of the ENP-receptor antagonist, HS-142-1. The renal content of cGMP was reduced in cirrhotic rats because of increased activity of cGMP-PDE. Zaprinast inhibited cGMP-PDE activity and increased the renal content of cGMP in these animals. The inhibition of cGMP-PDE was associated with an increase in RPF, GFR, and U(Na)V and a reduction in PRA. HS-142-1 prevented any renal effect of Zaprinast in cirrhotic rats. In conclusion, an increased activity of the cGMP-PDE in renal tissue contributes to the renal resistance to ENP in cirrhosis with ascites.

Reversal of type 1 hepatorenal syndrome with the administration of midodrine and octreotide

The aim of the study was to verify the effects of the administration of an inhibitor of the release of endogenous vasodilators together with a vasoconstrictor agent in patients with hepatorenal syndrome (HRS). This new medical perspective was compared with a traditional medical approach for HRS, such as the infusion of nonpressor doses of dopamine to produce renal vasodilation. Thirteen patients with type 1 HRS were enrolled in the study. Five of them were treated with the oral administration of midodrine and the parenteral administration of octreotide. In addition, the patients received 50 to 100 mL of 20% human albumin solution daily for 20 days. Midodrine and octreotide were dosed to obtain a stable increase of at least 15 mm Hg of mean arterial pressure. Eight patients were treated with the intravenous administration of nonpressor doses of dopamine (2-4 micrograms/kg/min) and the same daily amount of albumin. After 20 days of treatment with midodrine and octreotide, an impressive improvement in renal plasma flow (RPF), glomerular filtration rate, and urinary sodium excretion was observed in patients. This was accompanied by a significant reduction in plasma renin activity, plasma vasopressin, and plasma glucagon. No side effects were observed. Three patients were discharged from the hospital. One of them successfully underwent liver transplantation. One of the two remaining patients is still alive after 472 days with a preserved renal function, and the other died from terminal liver failure after 76 days. One of the two patients who were not discharged from the hospital successfully underwent liver transplantation, and the other died from pneumonia after 29 days. Seven out of eight patients who were treated with dopamine experienced a progressive deterioration in renal function and died during the first 12 days. Only one patient recovered renal function and underwent liver transplantation. In conclusion, the long-term administration of midodrine and octreotide seems to be an effective and safe treatment of type 1 HRS in patients with cirrhosis.

Acute effects of the oral administration of midodrine, an alpha-adrenergic agonist, on renal hemodynamics and renal function in cirrhotic patients with ascites

The effects of the acute administration of arterial vasoconstrictors on renal plasma flow (RPF) and urinary sodium excretion (UNaV) in cirrhotic patients with ascites with or without hepatorenal syndrome (HRS) are still controversial. As a consequence, vasoconstrictors are not actually used in the treatment of renal sodium retention or HRS in these patients, regardless of the several lines of evidence suggesting that these renal functional abnormalities are related to a marked arterial vasodilation. The lack of an orally available effective arterial vasoconstrictor probably represents a further reason for this omission. Consequently, the present study was made to evaluate the acute effects of the oral administration of midodrine, an orally available -mimetic drug, on systemic and renal hemodynamics and on UNaV in cirrhotic patients with ascites. Mean arterial pressure (MAP), heart rate (HR), cardiac index (CI), systemic vascular resistance (SVR), left forearm blood flow (LFBF), left leg blood flow (LLBF), RPF, glomerular filtration rate (GFR), UNaV, plasma renin activity (PRA), plasma concentration of antidiuretic hormone (ADH), and the serum levels of nitrite and nitrate (NOx) were evaluated in 25 cirrhotic patients with ascites (17 without HRS and 8 with type 2 HRS) before and during the 6 hours following the oral administration of 15 mg of midodrine. During the first 3 hours after the drug administration, a significant increase in MAP (89.6 +/- 1.7 vs. 81.80 +/- 1.3 mm Hg; P < .0001) and SVR (1, 313.9 +/- 44.4 vs. 1,121.2 +/- 60.1 dyn . sec . cm-5; P < .0001) accompanied by a decrease in HR (69 +/- 2 vs. 77 +/- 3 bpm; P < .005) and CI (2,932.7 +/- 131.4 vs. 3,152.5 +/- 131.4 mL . min-1 . m2 BSA; P < .0025) was observed in patients without HRS. No change was observed in LFBF and LLBF. The improvement in systemic hemodynamics, which was also maintained during the the 3- to 6-hour period after midodrine administration, was accompanied by a significant increase in RPF (541.5 +/- 43.1 vs. 385.7 +/- 39.9 mL . min-1; P < .005), GFR (93.1 +/- 6.5 vs. 77.0 +/- 6.7 mL . min-1; P < .025), and UNaV (92.7 +/- 16.4 vs. 72.2 +/- 10.7 microEq . min-1; P < .025). In addition, a decrease in PRA (5.33 +/- 1.47 vs. 7.74 +/- 2.17 ng . mL-1 . h; P < .05), ADH (1.4 +/- 0.2 vs. 1.7 +/- 0.2 pg . mL-1; P < .05), and NOx (33.4 +/- 5.0 vs. 49.3 +/- 7.3 micromol-1; P < .05) was found. In patients with HRS, the effects of the drug on the systemic hemodynamics was smaller and shorter. Accordingly, regardless of a significant decrease in PRA (15.87 +/- 3.70 vs. 20.70 +/- 4.82 ng . mL-1 . h; P < .0025) in patients with HRS, no significant improvement was observed in RPF, GFR, or UNaV. In conclusion, the acute oral administration of midodrine is associated with a significant improvement in systemic hemodynamics in nonazotemic cirrhotic patients with ascites. As a result, renal perfusion and UNaV also improve in these patients. By contrast, midodrine only slightly improves systemic hemodynamics in patients with type 2 HRS, with no effect on renal hemodynamics and renal function.

Chronic glucocorticoid excess and impaired osmoregulation of vasopressin release in dogs with hepatic encephalopathy

Chronic liver disease may be accompanied by disturbed sodium and water homeostasis. There is usually sodium retention and ascites. However, spontaneous natriuresis has also been reported in humans and experimental animals with liver cirrhosis. Chronic hypercortisolism, which may occur in dogs with advanced liver disease, is known to induce the inhibition of the osmostimulation of vasopressin (AVP) release. We have therefore investigated the osmoregulation of AVP release in 11 dogs with chronic hypercortisolism associated with advanced liver dysfunction and hepatic encepahlopathy and in 10 control dogs. Basal pituitary-adrenocortical activity was investigated by measuring the concentration in multiple plasma samples of adrenocorticotropin (ACTH), alpha-melanocyte-stimulating hormone (MSH), and cortisol and the cortisol:creatinine ratio in 24-hr urine. Urine specific gravity was also measured. The feedback regulation of the system was investigated by measuring these hormones in plasma after an intravenous (iv) injection of 0.01 mg/kg of dexamethasone. The osmoregulation of the release of AVP was investigated by the intravenous infusion of a 20% NaCl solution at a flow rate of 0.03 ml/kg for 2 hr and the measurement of AVP in plasma sampled at 20-min intervals. The AVP release was analyzed in terms of the threshold osmolality at which it commenced and the sensitivity, which reflects the magnitude of the response. All dogs had highly increased urinary cortisol:creatinine ratios, ranging from 21 to 210 x 10(-6) (normally < 10 x 10(-6)). The mean basal plasma concentrations of the three pituitary-adrenocortical hormones were significantly increased. ACTH values were 35 to 146 ng/l (normally, 14 to 68), MSH values were 26 to 118 ng/l (normally, 10 to 36), and cortisol values were 88 to 194 nmol/l (normally, 23 to 112). The feedback inhibition of the secretion of ACTH and cortisol in response to dexamethasone was unaffected. Urine specific gravity was significantly decreased. The regulation of AVP release was found to be abnormal in all dogs with hepatic encephalopathy. The osmotic threshold at which the release of AVP was induced was abnormally high in seven of the dogs with liver disease and in the normal range in one. It could not be determined in three dogs. The sensitivity of AVP release in response to increasing plasma hypertonicity was normal in two dogs and decreased in nine. In three dogs, there was no increase in AVP release. None of the dogs had normal values for both the sensitivity and the threshold.(ABSTRACT TRUNCATED AT 400 WORDS)

Stepped care medical treatment for cirrhotic ascites: analysis of factors influencing the response to treatment

Thirty-two patients with liver cirrhosis and ascites were treated by stepped care diuretic treatment as follows: step 1, placed on a 35 mEq sodium diet; step 2, given 400 mg/day of potassium canrenoate in addition to step 1 treatment; step 3, given 40-80 mg/day of furosemide in addition to step 2 treatment. Eleven out of 32 patients (34.4%, group 1) and 12 of 21 patients (57.1%, group 2) lost their ascites at step 1 and step 2, respectively. The remaining nine patients (group 3) required step 3 treatment. Basal urinary sodium excretion and creatinine clearance were significantly lower and beta 2-microglobulin was significantly higher in group 3 than those in groups 1 and 2. Elevation of basal plasma renin activity and norepinephrine was evident only in group 3. In group 1, urinary sodium excretion decreased after the treatment. In group 2, plasma alpha-atrial natriuretic polypeptide was lowered and plasma renin activity and norepinephrine were elevated after the treatment. These results suggest that basal renal function and plasma renin activity and norepinephrine levels are useful indices to predict the effect of ascites treatment and that responders to sodium restriction or potassium canrenoate may be in the state of vascular overflow, while non-responders to potassium canrenoate may be in the state of vascular underfilling. In summary, this stepped care treatment is safe without any side effects, although the diuretics themselves may lead to relative vascular underfilling.

Renal effects of natriuretic peptide receptor blockade in cirrhotic rats with ascites

The aim of this study was to assess the effect of HS-142-1, a recently discovered specific antagonist of endogenous natriuretic peptides, on systemic hemodynamics, renal function, and the renin-aldosterone system in rats with cirrhosis and ascites. The study consisted of three protocols, each including 10 conscious control rats and 10 conscious rats with carbon-tetrachloride-induced cirrhosis with ascites. In protocol 1, HS-142-1 administration (by intravenous bolus of 20 mg.kg-1.body weight in all protocols) was not associated with significant changes in mean arterial pressure, heart rate, cardiac output or total peripheral resistance in the two groups of animals. In protocol 2, HS-142-1 induced a significant reduction in glomerular filtration rate (from 4.2 +/- 0.5 to 2.6 +/- 0.3 ml/min, p < 0.025) in control animals. A decrease in renal plasma flow and an increase in renal vascular resistance also occurred, but these changes were not statistically significant. In cirrhotic rats, HS-142-1 resulted in a significant decrease in renal plasma flow (from 10.9 +/- 0.7 to 4.3 +/- 0.6 ml/min, p < 0.001) and a significant increase in renal vascular resistance (from 6.0 +/- 0.6 to 16.3 +/- 2.7 mm Hg.min.ml-1, p < 0.025). Glomerular filtration rate decreased more in cirrhotic rats with ascites than in control rats (from 3.8 +/- 0.3 to 1.3 +/- 0.2 ml/min, p < 0.001). Changes in urine flow rate and urinary sodium excretion rate paralleled those of glomerular filtration rate in both groups of animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic factor in cirrhosis: relationship to renal function and hemodynamic changes

Plasma atrial natriuretic factor concentrations and different hemodynamic parameters, including the evaluation of femoral arteriovenous shunting by measuring the arteriovenous difference of oxygen content (Ca-vO2), were determined in eight healthy subjects and 24 patients with cirrhosis without renal failure (group I: seven patients without ascites, group II: nine patients with ascites and UNaV > 10 mEq/24 h and group III: eight patients with ascites and UNaV < or = 10 mEq/24 h). Atrial natriuretic factor was 34 +/- 4.7 pg/ml in the control group and 44.28 +/- 5.4, 67.89 +/- 8.8 and 84 +/- 10.8 pg/ml in groups I, II and III respectively (p < 0.001. group III vs. I and control and II vs. control). Atrial natriuretic factor directly correlated with cardiac index (p < 0.01), blood volume (p: 0.01), femoral blood flow (p < 0.01) and inversely with systemic and femoral vascular resistances (p < 0.02), Ca-vO2 (p < 0.01), serum albumin (r: -0.61; p < 0.01) and prothrombin index (r: -0.63; p < 0.02). These results indicate that plasma atrial natriuretic factor is increased in patients with cirrhosis, especially in those with advanced disease and marked renal sodium retention. This suggests that in cirrhosis, arteriolar vasodilation and peripheral arteriovenous shunting influence renal function while inducing a state of overflow at the central venous compartment leading to increased atrial natriuretic factor secretion. Increased production of this vasodilatory hormone may thus contribute to the hyperkinetic circulation of cirrhosis.

Randomized clinical study of the efficacy of amiloride and potassium canrenoate in nonazotemic cirrhotic patients with ascites

Although some clinical studies seem to prove the efficacy of nonantialdosteronic potassium-sparing diuretics in the treatment of ascites, no controlled study has compared the efficacy of these drugs with that of antialdosteronic diuretics. Forty nonazotemic cirrhotic patients were randomized to receive amiloride (group A, n = 20) or potassium canrenoate (group B, n = 20). The initial doses of amiloride and potassium canrenoate were 20 mg and 150 mg, respectively. The doses were increased in stepwise fashion to 60 and 500 mg/day, respectively, if no response ensued. Nonresponders to the highest doses of each drug were later treated with potassium canrenoate and amiloride, respectively. Seven of 20 group A patients responded to amiloride, whereas 14 of 20 group B patients responded to potassium canrenoate (p < 0.025). Seven of 13 nonresponders to amiloride later responded to potassium canrenoate, whereas only two of the nonresponders to potassium canrenoate later responded to amiloride. The diuretic responses to amiloride and potassium canrenoate were related to the activity of the renin-aldosterone system. All responders to amiloride (n = 9) had normal values of plasma aldosterone. All nonresponders to amiloride who later responded to potassium canrenoate (n = 7) had increased levels of plasma aldosterone. Moreover, on comparison of all responders (n = 21) and nonresponders (n = 12) to potassium canrenoate, a higher degree of renal proximal sodium reabsorption (with consequent limitation of sodium delivery to the distal tubule) was found to be the main difference.(ABSTRACT TRUNCATED AT 250 WORDS)

Peritoneovenous shunting restores atrial natriuretic factor responsiveness in refractory hepatic ascites

BACKGROUND

Sodium retention in cirrhosis has been attributed to an imbalance between vasoconstrictive, antinatriuretic forces such as the renin aldosterone angiotensin system and the sympathetic nervous system, and vasodilatory, natriuretic agents such as atrial natriuretic factor (ANF). Patients with diuretic resistant refractory ascites may require peritoneovenous shunting (PVS) to control ascites.

METHODS

To study the factors responsible for the improvement in sodium homeostasis post-PVS, we compared the response to ANF infusion before and 1 month after PVS in 6 patients with massive ascites.

RESULTS

Before PVS, sodium excretion at baseline and in response to ANF infusion was blunted but became more normal post-PVS. ANF infusion post-PVS induced a significant increase in the glomerular filtration rate and filtration fraction and also in distal delivery of sodium. ANF's distal effect of increasing the fractional excretion of distally delivered sodium was present pre-PVS and was not significantly increased post-PVS. Changes in sodium handling were accompanied by a significant decrease in antinatriuretic forces (baseline aldosterone, 2079 +/- 507 vs. 647 +/- 17 nmol/L; P < 0.04) post-PVS.

CONCLUSIONS

The improvement in sodium homeostasis and response to ANF infusion post-PVS appears to be associated with the decrease in antinatriuretic forces with the loss of massive refractory ascites. Thus, PVS restores the balance toward ANF responsiveness.

The role of atrial natriuretic peptide (ANP) in chronic liver disease

The role of atrial natriuretic peptide (ANP) and potential defects of ANP in liver disease are reviewed. Patients with cirrhosis of the liver show no decrease of ANP plasma concentrations nor changes in the pattern of ANP immunoreactivity nor changes of splanchnic ANP clearance. The renal effects of exogenously administered as well as endogenously released ANP are blunted in cirrhosis, in particular in patients with ascites. This seems due to increased activity of sodium-retaining hormonal systems and changes of the renal ANP receptor status. Pharmacological inhibition of ANP-degradation or clearance may yield therapeutic potential.