Acute effects of peritoneovenous shunting on plasma atrial natriuretic peptide in cirrhotic patients with massive refractory ascites

Pathophysiology and Prevention of Paracentesis-induced Circulatory Dysfunction: A Concise Review

Annually, 10% of cirrhotic patients with ascites develop refractory ascites for which large-volume paracentesis (LVP) is a frequently used therapeutic procedure. LVP, although a safe method, is associated with circulatory dysfunction in a significant percentage of patients, which is termed paracentesis-induced circulatory dysfunction (PICD). PICD results in faster reaccumulation of ascites, hyponatremia, renal impairment, and shorter survival. PICD is diagnosed through laboratory results, with increases of >50% of baseline plasma renin activity to a value ≥4 ng/mL/h on the fifth to sixth day after paracentesis. In this review, we discuss the pathophysiology and prevention of PICD.

Prevention of Renal Impairment by Continuous Infusion of Human Atrial Natriuretic Peptide after Liver Transplantation

BACKGROUND

Acute renal failure occurring immediately after liver transplantation and requiring hemodialysis is a major problem resulting in a poor prognosis. We investigated the efficacy of human atrial natriuretic peptide, which has potent natriuretic effects and unique protective effects for glomeruli in preventing acute renal failure after liver transplantation.

METHODS

Thirty-seven patients who underwent live donor liver transplantation with model for end-stage liver disease scores greater than 15 were the subjects of the study. Subjects were prospectively randomized into two groups: patients that received synthetic human atrial natriuretic peptide infusion (Group H: n=19) and those that received conventional diuretics, furosemide and potassium canrenoate (Group C: n=18). The peri- and postoperative changes in hemodynamic status and renal function were compared between the two groups.

RESULTS

There were no statistical differences in the changes in hemodynamic status between groups. Hemodialysis was required after liver transplantation in nine patients, two in Group H and seven in Group C (P=0.04). Postoperative creatinine clearance was higher in Group H (P=0.03). Aldosterone level was suppressed in group H (P=0.006).

CONCLUSIONS

Continuous infusion of synthetic human atrial natriuretic peptide might be effective for preventing acute renal failure requiring hemodialysis after liver transplantation.

Inhibition of cGMP-specific phosphodiesterase type 5 reduces sodium excretion and arterial blood pressure in patients with NaCl retention and ascites

In the present study, we tested the hypothesis that inhibition of renal phosphodiesterase type 5 (PDE5) in patients with liver cirrhosis and ascites increases sodium excretion. The effect of sildenafil citrate was studied in a randomized double-blind. placebo-controlled crossover study. Diuretics were withdrawn, and a fixed sodium diet (100 mmol/day) was given to the patients for 5 days before both study days. After a 60-min basal period, eight patients received either oral sildenafil (50 mg) or placebo. Glomerular filtration rate (GFR) and renal blood flow (RBF) were determined by 99mTc-diethylenetriamine-pentaacetate and (131)I-hippuran clearances. In human nephrectomy specimens, PDE5 mRNA was expressed at similar levels in the cortex (n = 6) and inner medulla (n = 4). Histochemical staining showed PDE5 immunoreactivity in collecting ducts and vascular smooth muscle. At baseline, cirrhotic patients exhibited elevated plasma concentrations of ANP, renin, ANG II, and aldosterone that did not differ on the 2 study days. Basal sodium excretion was similar at the 2 study days (median 17 and 18 mmol, respectively), and patients were in positive sodium balance. Sildenafil increased heart rate, plasma renin activity, plasma ANG II, and aldosterone concentrations significantly after 60 min. Plasma cGMP concentration was increased after 120 and 180 min, and urinary sodium excretion and mean arterial blood pressure were decreased significantly at 120 and 180 min. Plasma ANP concentration, GFR, and RBF did not change after sildenafil. In patients with ascites and cirrhosis, inhibition of PDE5 did not promote natriuresis but led to increased plasma levels of the renin-angiotensin-aldosterone system.

The pathophysiologic basis for the treatment of cirrhotic ascites

Advances in the understanding of the pathophysiology of sodium retention and ascites formation in cirrhosis has helped improve the treatment of ascites in these patients. It is likely that further unraveling of these pathophysiologic changes will lead to the development of novel and better treatment options. For example, the development of aquaretic agents for the management of hyponatremia in cirrhosis may allow more effective use of diuretic therapy. The ultimate challenge is to use the understanding of the pathophysiology to develop new strategies to prevent the development of ascites in cirrhosis.

Atrial natriuretic peptide attenuates flow in an isolated lymph duct preparation

We investigated the hypothesis that atrial natriuretic peptide (ANP) attenuates lymph vessel pumping. In the present experiments, isolated bovine lymphatic vessels were cannulated at each end to create inflow and outlfow ports for the administration of Krebs' solution (vehicle) or ANP and for the measurement of fluid pumped by the vessel respectively. Once cannulated, the vessels were placed in a temperature-regulated bath circulated with oxygenated vehicle. Transmural pressure was regulated by the height of a fluid-filled reservoir. Lymph pump activity was assessed by measuring the volume of outlfow every ten minutes, ANP was administered at concentrations of 0 (control), 0.1, 1.0, 10 and 100 nM. Data were expressed as a percentage of the value in the control period. When compared with vehicle, ANP produced a significant inhibition of lymph pump activity by 7.7% at 0.1 nM, 24.2% at 10 nM and 38.26% at 100 nM averaged over the hour for which the vessels were exposed to each concentration. Thus ANP inhibits lymph pumping concentration dependently. This may be yet another mechanism by which ANP exerts its haemodynamic effects.

Comparison of candoxatril and atrial natriuretic factor in healthy men. Effects on hemodynamics, sympathetic activity, heart rate variability, and endothelin

The purpose of these experiments was to compare the effects of endopeptidase inhibition with oral candoxatril on systemic and forearm hemodynamics and muscle sympathetic nerve activity with responses to a low-dose atrial natriuretic factor infusion. Eleven healthy men received at random on three separate days either intravenous saline, natriuretic factor (1.6 pmol/kg per minute) plus saline, or oral candoxatril (200 mg) plus saline. Measurements were made at baseline and 30, 60, and 90 minutes after interventions. Atrial natriuretic factor lowered diastolic pressure (P < .01), central venous pressure (P < .001), forearm blood flow (P < .05), and forearm vascular compliance (P < .05) but had no effect on systolic pressure, heart rate or its variability, stroke volume, sympathetic nerve activity, plasma norepinephrine, or endothelin-1. Plasma epinephrine increased (P < .01). Candoxatril lowered central venous pressure (P < .001) and increased systolic pressure (from 116 +/- 6 to 120 +/- 7 mm Hg; P < .05), endothelin (from 4.6 +/- 1.1 to 6.8 +/- 3.2 pmol/L; P < .02), and epinephrine (P < .05), without affecting any other variables. Candoxatril and atrial natriuretic factor lowered central venous pressure in healthy men without causing a reflex increase in sympathetic nerve activity or norepinephrine, yet epinephrine rose. This suggests that both interventions may specifically inhibit sympathetic nerve traffic to muscle at physiological plasma atrial natriuretic factor concentrations. However, whereas the peptide lowered blood pressure, candoxatril increased systolic pressure. These contrasting hemodynamic responses may be related to differences in plasma atrial natriuretic peptide concentration and to altered endothelin metabolism by candoxatril.

Hemodynamic and renal effects of ascites apheresis, concentration and reinfusion in advanced cirrhosis

BACKGROUND/AIMS

We studied the effects of ascites apheresis, concentration and reinfusion, a new form of treatment for tense or refractory ascites, on systemic hemodynamics and renal function.

METHODS

Twelve patients with advanced cirrhosis (two belonging to Child-Pugh's class B and the remainder to class C) were monitored. They were evaluated under baseline conditions, just after the treatment, and 24 and 48 h after baseline assessment. In addition to systemic hemodynamics--as evaluated by Doppler echocardiography--and renal function, indirect markers of effective volemia, such as atrial natriuretic factor, plasma renin activity and aldosterone concentration, and plasma norepinephrine were also measured.

RESULTS

The technique led to significant changes in systemic hemodynamics, such as an increase in stroke volume and cardiac output. However, due to a striking reduction in peripheral vascular resistance, mean arterial pressure also declined. The hemodynamic changes were associated with a parallel increase in atrial natriuretic factor. Despite the reduction in arterial pressure, plasma renin activity also significantly declined, while plasma norepinephrine did not undergo significant changes. Although an improvement in glomerular filtration rate and renal sodium excretion occurred, neither change reached statistical significance. All the hemodynamic, renal and neuro-humoral changes described above subsided almost entirely after 48 h, when no significant changes with respect to baseline values were any longer detectable with the exception of a slight reduction in mean arterial pressure.

CONCLUSIONS

In advanced cirrhosis ascites apheresis, concentration and reinfusion enhance central volemia, but an exaggerated peripheral vasodilation largely wastes the potential favourable effect on arterial volemia. As a result, no significant improvement in renal perfusion and sodium excretion can ensue.

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)

Time course of circulatory and humoral effects of rapid total paracentesis in cirrhotic patients with tense, refractory ascites

BACKGROUND/AIMS

Tense ascites of cirrhosis can be treated with total paracentesis; however, the short-term effects of this procedure are poorly defined.

METHODS

The circulatory and humoral changes induced by total paracentesis (250 mL/min) were studied in 12 cirrhotics with tense, refractory ascites. Data were collected before, during, and after paracentesis and 24 hours later (after albumin infusion). Hormonal parameters were recorded again 48 hours and 6 days thereafter.

RESULTS

Paracentesis (10.7 +/- 4.4 L; 64 +/- 20 minutes) caused marked reduction of intra-abdominal, intrathoracic, right atrial, and pulmonary pressures. Heart rate did not change. Cardiac output and heart volumes increased. Systemic vascular resistances and mean arterial pressure slightly decreased. Baseline plasma renin and aldosterone levels were markedly increased; a reduction was already evident during paracentesis with the lowest values at the end of the procedure. All changes were maintained 24 hours later. Hormones regained baseline levels 6 days later.

CONCLUSIONS

Rapid total paracentesis is accompanied by marked cardiovascular and humoral changes. Some of these changes can be explained by mechanical factors that are directly or indirectly related to the relief of abdominal pressure. However, other changes (systemic vasodilatation, humoral deactivation) have a non-mechanical nature and may depend on reflexes originating from cardiac volume receptor stimulation. Most changes may beneficially (albeit transiently) influence the cardiovascular system of cirrhotic patients with tense ascites.

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.

Angiotensin II modulates atrial natriuretic factor-induced natriuresis in cirrhosis with ascites

Resistance to the natriuretic action of atrial natriuretic factor (ANF) in cirrhosis with ascites has been correlated with rising levels of antinatriuretic factors, such as renin, angiotensin II (AII), and aldosterone, as well as increased sympathetic nerve activity. To determine whether AII can serve as a mediator rather than only as a marker of the antinatriuresis, a nonpressor dose of AII (5 ng/kg/min) was given during an ANF infusion in eight patients with cirrhosis and ascites who responded to ANF infusion with a natriuresis. Patients were maintained in metabolic balance and measurements of para-aminohippuric acid, inulin, and lithium clearance were taken before and during infusion of ANF with or without AII. Atrial natriuretic factor infusion was associated with a natriuretic response accompanied by an increase in glomerular filtration rate, filtration fraction, and lithium clearance compared with baseline. The addition of AII was associated with a return of the glomerular filtration rate to baseline, with no change in filtration fraction. This was reversible on withdrawal of AII infusion. Natriuresis induced by ANF occurred despite baseline elevations of the renin angiotensin aldosterone system and was associated with an increase in distal delivery of sodium and a decrease in fractional reabsorption of distally delivered sodium as estimated by lithium clearance parameters. Angiotensin II infusion exerted effects on both proximal and distal nephron sites to abrogate ANF-induced natriuresis. These results suggest that AII may serve as a mediator as well as a marker of resistance to the natriuretic effect of ANF in patients with cirrhosis and ascites.(ABSTRACT TRUNCATED AT 250 WORDS)

Concentrated ascitic fluid reinfusion after cascade filtration in tense ascites

A new method for concentrated ascitic fluid reinfusion using a double ultrafiltration device is reported as 22 procedures in 20 cirrhotic patients (6 females, 14 males; median age 55 years, range 33-69) with tense, refractory ascites. Eight of the 20 patients had elevated creatinine levels. The mean time for each procedure was 189 +/- 82 min, during which a mean of 7.7 liters (1.3-13.3) of ultrafiltered ascitic fluid was removed and 613 ml (140-1700) of concentrated ascitic fluid rich in albumin (mean: 60 g, range 14-175) was reinfused. The procedure resulted in a mean weight loss of 8.1 kg (2.2-14.0) and a mean increase of 163 ml in urine output (24 hr). A reduction in the serum creatinine level (P < 0.05) and an increase in the plasma atrial natriuretic factor level (P < 0.02) 24 hr after reinfusion, while no changes in serum albumin, plasma and urinary electrolytes, plasma renin activity, aldosterone, and antidiuretic hormone levels were noted. Although minor evidence for a disturbance in coagulation was observed, there were no episodes of clinical bleeding. Four patients (20%) had transient chills or fever. Based upon this experience, it can be concluded that reinfusion of cascade filtered and concentrated ascitic fluid is a rapid, safe, and effective treatment for patients with tense ascites; it appears to have less side effects than more traditional methods and importantly does not require administration of heterologous plasma derivatives.

Hypotension in experimental cirrhosis. Is loss of vascular responsiveness to norepinephrine the cause of hypotension in chronic bile-duct-ligated dogs?

It has been postulated that one of the mechanisms of hypotension associated with cirrhosis is an attenuated responsiveness to catecholamines despite the increased activity of the sympathetic nervous system and the elevated plasma concentrations of the sympathetic neurotransmitter, norepinephrine. This abnormality was studied in a dog model of portal hypertension and cirrhosis. Twelve weeks after bile duct ligation (n = 16), intrasplenic pressure rose significantly from 6.3 +/- 0.4 to 14.6 +/- 1.6 mmHg (p < 0.05), mean arterial pressure had fallen from 106 +/- 4 to 83 +/- 8 mmHg (p < 0.01), cardiac output had risen from 3.1 +/- 0.2 to 3.8 +/- 0.8 l/min (p < 0.05) and plasma norepinephrine concentrations rose from 0.22 +/- 0.12 to 1.17 +/- 0.52 nmol/l (p < 0.05). In 7 sham-operated dogs, the changes in these 4 variables over the same period were non-significant. In vivo pressor responsiveness was tested by studying the effects of intravenous and intra-arterial infusions of norepinephrine and the non-selective beta-adrenoceptor agonist, isoproterenol. In vitro responsiveness was tested by measuring the effects of isoproterenol on the isometric twitch of isolated ventricular strips and the effects of norepinephrine on femoral, mesenteric and renal arterial rings. There was no significant change in the in vivo responses of chronic bile-duct-ligated dogs at 12 weeks compared to the preoperative assessment, or to sham-operated dogs at 12 weeks. Furthermore, there was no significant difference between the in vitro responses of ventricular strips to isoproterenol or arterial rings to norepinephrine prepared from chronic bile-duct-ligated and sham-operated dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

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

Ascitic cirrhotic patients are a heterogenous population with respect to factors that may affect plasma human atrial natriuretic peptide levels (such as degree of plasma volume and plasma levels of angiotensin II, vasopressin and norepinephrine). Thus the proven variability of plasma human atrial natriuretic peptide values in ascitic cirrhotic patients may be due also to the selection of patients, not only to the study conditions. The response to standardized stepped-care medical treatment of ascites makes it possible to characterize ascitic cirrhotic patients with different patterns of renal sodium excretion, intrarenal sodium handling, plasma renin activity, plasma aldosterone and thus, probably, effective circulating volume. Consequently, we evaluated human atrial natriuretic peptide plasma levels in controls (n = 23), in ascitic cirrhotic patients who underwent spontaneous diuresis (group A, n = 7) and in cirrhotic patients who required diuretic treatment (group B, n = 44). The last group was then divided into two subgroups. Subgroup B-R (n = 25) included patients who responded to spironolactone alone, whereas subgroup B-NR (n = 19) included patients who did not respond to 500 mg/day spironolactone. All patients were maintained on identical normocaloric restricted sodium intake (80 mEq/day) throughout the study. Ascitic cirrhotic patients, as a whole, had higher values of human atrial natriuretic peptide than did controls (70.8 +/- 46.6 pg/ml vs. 41.7 +/- 16.3 pg/ml, p < 0.025). No difference was found in human atrial natriuretic peptide/plasma renin activity between the two groups (87 +/- 160 pg/ng/hr vs. 44 +/- 73 pg/ng/hr, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Estimated central blood volume in cirrhosis: relationship to sympathetic nervous activity, beta-adrenergic blockade and atrial natriuretic factor

The estimated central blood volume (i.e., blood volume in the heart cavities, lungs and central arterial tree) was determined by multiplying cardiac output by circulatory mean transit time in 19 patients with cirrhosis and compared with sympathetic nervous activity and circulating level of atrial natriuretic factor. Arterial norepinephrine level, an index of overall sympathetic nervous activity (3.08 nmol/L in patients vs. 1.36 nmol/L in controls; p < 0.01) was negatively correlated (r = -0.54, p < 0.01) with estimated central blood volume (mean = 23 ml/kg in patients vs. 27 ml/kg in controls; p < 0.05). Similarly, renal venous norepinephrine level (an index of renal sympathetic tone; 4.26 nmol/L in patients vs. 1.78 nmol/L in controls; p < 0.01) was inversely correlated with estimated central blood volume (r = -0.53, n = 18, p < 0.02). No significant correlation could be established between arterial atrial natriuretic factor level (8.9 pmol/L in patients vs. 9.6 pmol/L in controls; not significant) and estimated central blood volume. Hemodynamic values were subsequently modified with oral propranolol (80 mg). During beta-adrenergic blockade, the mean estimated central blood volume was not altered significantly, except in six patients who exhibited decreases in mean arterial blood pressure (85 to 69 mm Hg; n = 6) and decreases in mean estimated central blood volume (23.2 to 20.6 ml/kg; n = 6, p < 0.05). Slight increases were observed in mean right atrial pressure (2.2 to 3.7 mm Hg; n = 14, p < 0.05); this change was positively correlated with the change in estimated central blood volume (r = 0.44, n = 14, p = 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)

Renal insensitivity to atrial natriuretic peptide in patients with cirrhosis and ascites. Effect of increasing systemic arterial pressure

The IV infusion of pharmacological doses (0.05 microgram.kg-1.min-1) of atrial natriuretic peptide to 16 patients with cirrhosis and ascites induced a significant increase in sodium excretion (65 +/- 23 to 517 +/- 231 mu Eq/min), urine volume (10.7 +/- 2.3 to 15.7 +/- 3.7 mL/min), and glomerular filtration rate (89 +/- 4 to 110 +/- 4 mL/min) in only 5 patients (responders). No significant changes in these parameters (15 +/- 6 to 11 +/- 4 mu Eq/min, 5.5 +/- 1.0 to 4.2 +/- 1.1 mL/min, and 81 +/- 5 to 79 +/- 6 mL/min, respectively) were observed in the remaining patients (nonresponders). Compared with responders, nonresponders had significantly lower baseline sodium excretion (P less than 0.02), urine flow (P less than 0.05), free water clearance (2.5 +/- 0.9 vs. 6.9 +/- 2.1 mL/min; P less than 0.05), and mean arterial pressure (82 +/- 3 vs. 96 +/- 2 mm Hg; P less than 0.01) and significantly higher plasma renin activity (16.3 +/- 4.9 vs. 1.8 +/- 0.2 ng.mL-1.h-1; P less than 0.05) and aldosterone level (99 +/- 24 vs. 13 +/- 2 ng/dL; P less than 0.05). Atrial natriuretic peptide produced a similar reduction of arterial pressure in both groups. To investigate whether the blunted natriuretic response to atrial natriuretic peptide in nonresponders was caused by their lower arterial pressure, atrial natriuretic peptide was infused in 7 of these patients after increasing their arterial pressure to the levels of responders with nonrepinephrine. The increase in arterial pressure (from 81 +/- 5 to 95 +/- 5 mm Hg), which was not associated with significant changes in plasma renin activity and aldosterone concentration, did not reverse the blunted renal response to atrial natriuretic peptide in any of these patients. These results indicate that cirrhotic patients with blunted renal response to atrial natriuretic peptide are characterized by low arterial pressure, marked overactivity of the renin-aldosterone system, and severe sodium and water retention. Correction of hypotension without increasing effective blood volume does not restore renal insensitivity to atrial natriuretic peptide.

Muscle sympathetic nerve activity and renal responsiveness to atrial natriuretic factor during the development of hepatic ascites

PURPOSE

Sodium retention in cirrhosis has been attributed to an imbalance between vasoconstrictive antinatriuretic forces such as the sympathetic nervous system and vasodilatory natriuretic agents such as atrial natriuretic factor (ANF). With the development of refractory ascites, cirrhotic patients become unresponsive to the natriuretic effect of ANF. Animal data suggest that the sympathetic nervous system plays a key role in mediating the refractoriness to ANF. We therefore studied the relationship between sympathetic nerve activity (SNA) and the natriuretic response to ANF in normal subjects and cirrhotic patients. We also attempted to localize the intrarenal site of refractoriness to ANF by lithium clearance.

PATIENTS AND METHODS

Twenty-six patients with biopsy-proven cirrhosis and seven age- and sex-matched normal volunteers were studied after a week of 20 mmol/day sodium intake and no diuretics. Muscle SNA was recorded from the peroneal nerve (microneurography) and correlated with responsiveness to a 2-hour ANF infusion. Lithium clearance was used as a marker of sodium reabsorption proximal to the intramedullary collecting duct, the main site of ANF action. Plasma norepinephrine, renin, and aldosterone levels were also determined. Patients were categorized into three groups: nine patients free of ascites (by ultrasonography), five ascitic patients who responded to a 2-hour ANF infusion (i.e., had a natriuretic response to ANF above 0.83 mmol/hour), and 12 ascitic patients who did not respond.

RESULTS

Muscle SNA was greatly increased in the ascitic nonresponder patients compared with the normal subjects (64 +/- 4 versus 27 +/- 7 bursts/minute, p less than 0.001), moderately increased in ascitic responders (47 +/- 6 bursts/minute, p less than 0.05), but not significantly increased in nonascitic patients with cirrhosis (34 +/- 5 bursts/minute). SNA was positively correlated with plasma norepinephrine levels (r = 0.69; p less than 0.005) and inversely correlated with peak sodium excretion during the ANF infusion (r = -0.63; p less than 0.001). Plasma renin activity and aldosterone were markedly elevated in ascitic nonresponders, and normal in ascitic responders and nonascitic patients. Lithium clearance was reduced in ascitic patients compared with nonascitic patients, did not change after the ANF infusion, and correlated inversely with SNA (r = -0.61; p less than 0.01).

CONCLUSION

These results support the concept that the sympathetic nervous system is a factor in renal sodium handling in cirrhosis, especially in the initiation of sodium retention and the development of refractory ascites. Refractoriness to ANF might be explained, at least in part, by increased neurally mediated sodium reabsorption proximal to the intramedullary collecting duct, the main site of ANF action.

Effect of intrathoracic pressure on plasma arginine vasopressin levels

Abdominal distention during pneumoperitoneum results in a marked increase in plasma arginine vasopressin levels, which has been ascribed to an increase in intrathoracic pressure. Because of this relationship, tense ascites could contribute to nonosmotic release of antidiuretic hormone, to the development of hyponatremia, and eventually to further ascites formation. The effect of pneumoperitoneum, thoracocentesis, and paracentesis on plasma arginine vasopressin levels was studied in three groups of patients, and the mechanism by which these maneuvers may induce these changes was investigated. Patients with pleural effusion, pneumothorax, or ascites showed a significant increase in plasma arginine vasopressin levels, and thoracocentesis or paracentesis resulted in a decrease in these levels. Plasma vasopressin levels increased significantly during pneumoperitoneum, as did intrathoracic and atrial pressures; the atrial transmural pressure gradient declined. However, no changes in plasma levels of norepinephrine, aldosterone, and renin activity were observed during pneumoperitoneum. Changes in plasma arginine vasopressin levels correlated with the changes in intrathoracic and atrial pressures and transmural pressure gradient. The authors conclude that increased intrathoracic pressure is associated with an increase in plasma arginine vasopressin levels and propose that ascites could be a factor promoting vasopressin release by acting on intrathoracic volume receptors in decompensated cirrhotics.

The response of atrial natriuretic factor and sodium excretion to dietary sodium challenges in patients with chronic liver disease

Despite intensive investigation, the pathogenesis of sodium retention in patients with chronic liver disease is not fully known. We have studied 19 chronic liver disease patients, 13 without (group 1) and six with (group 2) histories of clinical sodium retention (ascites or edema) by varying dietary sodium intake. The patients were placed on a 20 mmol/day constant diet for 1 wk, followed by a constant 100 mmol/day sodium diet for 1 wk under strict metabolic conditions. After 5 days of equilibration on each diet, blood and urine samples were collected for plasma atrial natriuretic factor levels and urinary sodium excretion. Group 1 patients (n = 6) achieved near sodium balance in 5 days on both a 20-mmol (urinary sodium output = 17 +/- 3 mmol/day) and a 100-mmol sodium diet (urinary sodium output = 80 +/- 5 mmol/day). Atrial natriuretic factor levels in these patients tended to be elevated, but the increase was not significantly greater than that in normal control subjects (10 +/- 4 pg/ml to 19 +/- 4 pg/ml) on the same diets. In contrast, group 2 patients (n = 5) were in significant positive sodium balance on both the 20 mmol/day sodium diet (mean urinary sodium output = 9.5 +/- 3.3 mol/day) and the 100 mmol/day sodium diet (urinary sodium output = 37 +/- 13 mmol/day). This occurred despite significantly elevated baseline atrial natriuretic factor levels and a significant increase in plasma atrial natriuretic factor levels after sodium challenge (62 +/- 9 pg/ml, p less than 0.05) on a 100 mmol/day sodium diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial volume in cirrhosis: relationship to blood volume and plasma concentration of atrial natriuretic factor

Increased blood volume, atrial size, and plasma concentration of atrial natriuretic factor are described in cirrhosis. Their interrelationships were examined in 17 men with alcoholic liver disease, 7 with and 10 without ascites. Atrial size was determined by two-dimensional echocardiography. Patients with cirrhosis had significantly increased left atrial volume and plasma concentration of atrial natriuretic factor when compared with normal male subjects. Right atrial volume was normal in patients with cirrhosis, as was left ventricular function. Patients with ascites had significantly increased blood volume and plasma atrial natriuretic factor concentration compared with patients without ascites. Left and right atrial volume did not differ between the groups. Blood volume correlated significantly with left atrial volume, which correlated significantly with plasma concentration of atrial natriuretic factor. Cirrhosis is associated with related increases in vascular volume, left atrial size, and plasma atrial natriuretic factor concentration. Increased blood volume probably contributes to the increase in left atrial volume, which is in turn one reason for the elevation of plasma atrial natriuretic factor concentration.

Sympathoinhibitory effects of atrial natriuretic factor in normal humans

In rats, atrial natriuretic factor (ANF) reduces sympathetic nerve activity (SNA) reflexively by sensitizing cardiac mechanoreceptors with inhibitory vagal afferents. We performed three series of experiments in 26 normal young men to document whether ANF inhibits SNA in humans and if so, to determine potential mechanisms for this phenomenon. First, we recorded muscle SNA before and during brief infusions of ANF, vehicle (saline solution), and sodium nitroprusside, titrated to achieve reductions similar to those produced by ANF in diastolic pressure and central venous pressure, and we also assessed the effect of ANF on sympathetic nerve responses to a cold pressor test (CPT). Second, we determined the effect of ANF on Doppler-derived measurements of cardiac output and responses to hypotensive (-40 mm Hg) lower-body negative pressure (LBNP) and its sudden cessation. Third, we applied nonhypotensive (-15 mm Hg) LBNP to selectively unload cardiopulmonary baroreceptors, and we released LBNP to stimulate these inhibitory afferents during sequential infusions of nitroglycerin, vehicle (saline solution), and ANF. Our key findings were that 1) reductions in arterial and central venous pressures during ANF infusion were not accompanied by anticipated reflex increases in muscle SNA; 2) ANF blunted the increase in SNA with CPT; 3) ANF increased stroke volume and cardiac output; and 4) sympathoneural responses to both the application and the sudden cessation of nonhypotensive LBNP were attenuated, not augmented, by ANF. Changes in plasma norepinephrine concentrations reflected these sympathetic nerve responses to ANF. These results do not support the concept that ANF inhibits sympathetic outflow reflexively in humans by increasing discharge from cardiac mechanoreceptors with inhibitory vagal afferents but are consistent with either a central or a ganglionic sympathoinhibitory action of ANF. ANF could facilitate hypotension and natriuresis in humans by attenuating the reflex sympathetic response to baroreceptor deactivation.

Atrial natriuretic factor in cirrhotic patients with tense ascites. Effect of large-volume paracentesis

The plasma levels of atrial natriuretic factor in liver cirrhosis can be affected by various factors, such as ascites, renal function, use of diuretics drugs and dietary sodium intake. Moreover, the influence of high intra-abdominal pressure on cardiac atrial natriuretic factor release in patients with tense ascites has not been investigated. The aim of the present study was to evaluate the circulating levels of atrial natriuretic factor and their relationships to plasma renin activity, aldosterone concentration, and urinary sodium excretion in 45 cirrhotic patients divided into 4 groups: (a) cirrhotics without ascites; (b) nonazotemic cirrhotics with ascites; (c) cirrhotics with ascites and functional renal failure; and (d) cirrhotics with ascites taking diuretics. In some patients with tense ascites, atrial natriuretic factor was also measured after rapid abdominal relaxation by large volume paracentesis. Plasma levels of atrial natriuretic factor obtained in 13 healthy control subjects after 5 days on a 40-50 mEq sodium daily intake were 22.8 +/- 3.3 pg/ml. Mean plasma atrial natriuretic factor levels were normal in patients without ascites (35.1 +/- 11.4 pg/ml) and in those with ascites taking diuretics (27 +/- 9.2 pg/ml), but elevated in patients with ascites not taking diuretics (59.6 +/- 12 pg/ml) and in those with ascites and functional renal failure (58.5 +/- 16.6 pg/ml). These data show that plasma atrial natriuretic factor levels are elevated only in cirrhotic patients who are ascitic and not taking diuretics. In these patients atrial natriuretic factor levels were directly correlated with urinary sodium excretion, even though sodium balance was positive. This could be the consequence of the contrasting effects of antinatriuretic factors, as suggested by the inverse relationships between atrial natriuretic factor and urinary sodium on the one hand and plasma renin activity and plasma aldosterone concentration on the other. Twenty-six patients with tense ascites (12 taking diuretics and 14 not) were treated with rapid large-volume paracentesis (6500 +/- 330 ml of ascitic fluid removed in 168 +/- 16 min). At the end of the procedure, plasma atrial natriuretic factor levels had increased in all patients (from 45.5 +/- 10.1 to 100 +/- 17 pg/ml), whereas plasma renin activity and plasma aldosterone concentration had decreased (from 10.3 +/- 1.6 to 7 +/- 1.3 ng/ml/h, and 1160 +/- 197 to 781 +/- 155 pg/ml, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of repeated atrial natriuretic peptide bolus injections in cirrhotic patients with refractory ascites

The renal and hormonal effects of repeated atrial natriuretic peptide (ANP) boli (1 microgram/kg of body weight) were studied in eight cirrhotic patients with refractory ascites. Under basal conditions the patients showed a striking activation of the renin-angiotensin-aldosterone system (plasma renin activity 19.3 +/- 3.0 ng/ml.h, plasma aldosterone concentration 3.87 +/- 0.58 ng/ml) and a tenfold elevation in plasma ANP levels compared to healthy subjects (131.7, range 47.0-288.6, vs. 9.8, range 5.0-15.0, fmol/ml, p less than 0.001). The first ANP injection was followed by a remarkable increase in plasma ANP levels and by a slight increase in urinary cyclic guanosine-monophosphate excretion (from 1050.8 +/- 454.8 to 1446.6 +/- 822.2 pmol/min). A significant reduction of mean blood pressure (MBP) occurred 5 min after the first injection (from 86.7 +/- 7.2 to 79.9 +/- 5.8 mmHg, p less than 0.05), but values gradually returned to the baseline after 30 min. Heart rate (HR) increased 10 min after the first bolus injection (from 83.75 +/- 4.7 to 88.1 +/- 4.6 beats/min) and reached baseline values after 30 min. Similar behaviour of MBP and HR was observed after the second, third and fourth bolus injections. Urinary sodium excretion, urinary flow, glomerular filtration rate, plasma renin activity, and plasma aldosterone concentration did not show any significant modification during ANP administration, nor did these parameters change in the following 12-h recovery period.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal prostaglandin E2 and other vasoactive modulators in refractory hepatic ascites: response to peritoneovenous shunting

To assess the role of renal prostaglandin E2 in the pathogenesis of refractory ascites, in relation to renal sodium handling and circulating levels of vasoconstrictive substances, we studied 12 cirrhotic patients with refractory ascites before and after peritoneovenous shunting. Baseline values for urinary prostaglandin E2 excretion, sodium excretion, and creatinine clearance, as well as serum aldosterone, plasma renin activity, and plasma free norepinephrine, were obtained preoperatively with patients on a sodium- and fluid-restricted diet. Diuretics were also withheld. Similar parameters were measured immediately postoperatively during four consecutive 2-h intervals, then again at 2 wk and 3 mo. In patients with refractory ascites, mean baseline urinary prostaglandin E2 excretion was significantly elevated (2.5 +/- 0.8 pmol/min), compared with that in both normal controls and cirrhotics without ascites (1.3 +/- 0.3 pmol/min). A significant natriuresis occurred immediately postoperatively and persisted at 2 wk and 3 mo. Concomitantly, the elevated levels of preoperative vasoconstrictor substances gradually normalized by 2 wk. Urinary prostaglandin E2 excretion, however, rose transiently in the immediate postoperative period and then fell gradually to within the normal range by 3 mo. Enhanced renal prostaglandin E2 synthesis, therefore, does not play a role in the sustained improvement in sodium homeostasis after peritoneovenous shunting in patients with refractory ascites.

Role of atrial natriuretic peptide in the natriuretic response to central volume expansion induced by head-out water immersion in sodium-retaining cirrhotic subjects

PURPOSE

It is possible that abnormalities in atrial natriuretic peptide may be involved in the pathogenesis of sodium retention in edema states. We performed a study in a group of 12 sodium-retaining cirrhotic subjects to determine the role of this peptide in mediating differences in the natriuretic response to central volume expansion induced by head-out water immersion.

PATIENTS AND METHODS

Each patient was maintained for seven days on a 20-mmol sodium intake, and then studied on both control and immersion days. On each day, measurements of the following were obtained: plasma atrial natriuretic peptide, hematocrit, electrolytes, creatinine, plasma renin activity, serum aldosterone, urinary cyclic guanosine monophosphate (cGMP), blood pressure, and pulse rate.

RESULTS

In six subjects, immersion resulted in a marked natriuresis sufficient to induce negative sodium balance by the third hour, and these subjects were termed "responders." In these six patients, baseline pre-immersion levels of plasma renin activity and serum aldosterone were all below 3 ng/liter/second and 4 nmol/liter, respectively. In the other six subjects, the natriuretic response to immersion was markedly blunted and insufficient to induce negative sodium balance, and these subjects were termed "non-responders." In these subjects, baseline pre-immersion levels of plasma renin activity and aldosterone were all above 3.5 ng/liter/second and 5 nmol/liter, respectively, and were significantly elevated compared with the responders, and compared with the normal range for control subjects consuming the same sodium intake. In both groups of cirrhotic subjects, baseline levels of plasma atrial natriuretic peptide and cGMP excretion were significantly and comparably elevated compared with the normal range for control subjects ingesting the same sodium intake. Despite the marked difference in the natriuretic response to immersion in both responders and non-responders, there was a significant and comparable further elevation of plasma atrial natriuretic peptide and urinary cGMP excretion during immersion, compared with the control day.

CONCLUSION

These results suggest that the relative resistance to the natriuretic action of atrial natriuretic peptide in the non-responders compared with the responders is mediated by anti-natriuretic factors acting at a level parallel with or beyond atrial natriuretic peptide release or coupling to its cGMP-linked receptors.