Ascites is a serious complication of cirrhosis, occurring in about 50% of patients within 10 years after diagnosis, and it is associated with 50% mortality in 2 years.1, 2 Patients with ascites have hyperdynamic circulation, which is characterized by peripheral and splanchnic arterial vasodilatation and reduced arterial blood pressure and systemic vascular resistance.3 Portal hypertension and splanchnic vasodilatation are major factors in the development of ascites.4, 5 Secondary to vasodilatation, vasoactive hormones, such as the renin-angiotensin-aldosterone system and the sympathetic nervous system, are activated. This leads to renal vasoconstriction and reduced renal perfusion and filtration pressure. The current standard treatment of ascites involves diuretics and paracentesis, which are not designed to improve the underlying pathophysiology. The changes in the renal handling of water and salt seem to develop stepwise from a stage that can be controlled by diuretics to a stage refractory to diuretics and finally to full-blown renal failure, which is known as hepatorenal syndrome (HRS) type 1.6 Several clinical studies have evaluated the efficacy of the long-term administration of terlipressin [a vasopressin 1 (V1) receptor agonist] in patients with HRS,7–13 and there is evidence that terlipressin may improve renal function and survival in patients with HRS type 1. The mechanisms behind the effect of terlipressin in HRS have not been thoroughly investigated. Terlipressin seems to revert the systemic vasodilatation and increase blood pressure14 and thereby improve renal perfusion pressure and renal function. As HRS is most often preceded by the development of ascites, vasoconstrictors may also have a beneficial effect in decompensated cirrhosis without severe renal impairment and thereby represent a novel future treatment for ascites. This is a pathophysiological study in which we investigated if the acute administration of the vasoconstrictor terlipressin improves renal perfusion, glomerular filtration, and renal excretion of salt and water in patients with cirrhosis with nonrefractory ascites and refractory ascites.
Patients with advanced cirrhosis and ascites are characterized by circulatory dysfunction with splanchnic vasodilatation and renal vasoconstriction, which often lead to ascites. The vasoconstrictor terlipressin improves renal function in hepatorenal syndrome (HRS). The aim of this study was to evaluate if terlipressin also improves renal function in patients with ascites without HRS. Twenty-three patients with cirrhosis participated; 15 with nonrefractory ascites were randomized to either terlipressin (N group, n = 11) or a placebo (P group, n = 4), and 8 had refractory ascites and received terlipressin (R group). The glomerular filtration rate (GFR), sodium clearance (CNa), lithium clearance (CLi), osmolal clearance (COsm), and urine sodium concentration (UNa) were assessed before and after the injection of 2 mg of terlipressin or the placebo. GFR increased in the N group (69 ± 19 versus 92 ± 25 mL/min, P < 0.005) and in the R group (31 ± 19 versus 41 ± 31 mL/min, P < 0.05) after terlipressin. In the N group, terlipressin induced an increase in CNa (0.89 ± 0.21 versus 1.52 ± 1.45 mL/min, P < 0.05), CLi (17.3 ± 8.9 versus 21.5 ± 11.6 mL/min, P < 0.05), and COsm (2.10 ± 0.81 versus 3.06 ± 2.0 mL/min, P < 0.05). In the R group, terlipressin induced an increase in CNa (0.11 ± 0.18 versus 0.35 ± 0.40 mL/min, P < 0.05) and CLi (5.5 ± 4.2 versus 9.5 ± 8.55 mL/min, P < 0.05). UNa increased in both groups after terlipressin (P < 0.005). Plasma norepinephrine (P < 0.05) and renin (P < 0.05) decreased after terlipressin. All parameters remained unchanged after the placebo. Conclusion: The vasopressin 1 receptor agonist terlipressin improves renal function and induces natriuresis in patients with cirrhosis and ascites without HRS. Vasoconstrictors may represent a novel future treatment modality for these patients. (HEPATOLOGY 2007.)
Patients and Methods
The study included 23 patients, between 18 and 75 years of age, with alcoholic cirrhosis and ascites; 2 patients also had a chronic hepatitis C infection. Of the patients, 15 with nonrefractory ascites were investigated in a randomized, double-blinded, placebo-controlled design, and 8 with diuretic-resistant ascites were investigated in an unblinded design. We chose not to randomize the patients with diuretic-resistant ascites because they are rare and, on account of the advanced disease, are difficult to handle in a clinical study. Patients were ineligible if they had HRS as defined by the International Ascites Club,3 gastrointestinal bleeding within the week before the study, insulin-dependent diabetes mellitus, acute or chronic intrinsic renal or cardiovascular disease, arterial hypertension, abnormal urine analyses or electrocardiograms, hepatocellular carcinoma or portal vein thrombosis, or any other acute medical conditions such as infections or lung diseases. Furthermore, alcohol abstinence for 2 months was required.
Refractory ascites was defined by the diagnostic criteria set by the International Ascites Club,15 which are in brief as follows: ascites that cannot be mobilized or early recurrence that cannot be satisfactorily prevented by medical therapy. All patients with nonrefractory ascites had visible ascites verified by an abdominal ultrasound examination within the 2 months before the investigation.
All patients received diuretics prior to the study. The diuretic treatment was administered according to the current guidelines with stepwise increases until a clinical effect or the development of hyperkalemia, hyponatremia, encephalopathy, or an increase in serum creatinine.16 Five of the patients could not tolerate the maximum dose of diuretics, which was 160 mg of furosemide and 400 mg of spironolactone, because of an increase in creatinine or potassium. Patients with refractory ascites had a mean of 6 therapeutic paracenteses (range: 2–12) performed, although none were performed within the last week before the investigations. Diuretics and beta-blockers were temporarily discontinued 60 hours before the investigations. The patients were on a sodium-restricted diet (60 mmol/day) the last 72 hours before the investigations. They were carefully instructed orally and given written information about the diet by a dietician. During the last 24 hours before the investigations, all patients were hospitalized, and the nutrition unit of the hospital prepared their food with a 60 mmol/day sodium diet.
Design and Methods.
A nurse who was unrelated to the study drew opaque sealed envelopes prepared by an external statistician. Among the 15 patients with nonrefractory ascites, 11 were randomized to 2 mg of terlipressin, and 4 patients were randomized to an infusion of a placebo. Only 4 received the placebo because of computer randomization. A computer made the randomization code with 21 envelopes, with one-third for the placebo and two-thirds for terlipressin, and only 15 were used. The 8 patients with refractory ascites all received 2 mg of terlipressin. The nurse also administered the infusion of terlipressin or the placebo. As the placebo, 10 mL of an isotonic saline solution was infused. Unblinding was not performed until the data had been typed into the database, the calculations had been performed, and the data had been monitored by the good clinical practice (GCP) unit.
The patients were studied at 9:00 AM after a 9-hour fast. At 10:00 PM of the previous day, an oral dose of 300 mg of lithium carbonate was administered. An oral water load of 200 mL of tap water was given every half hour from 9:00 AM to the end of the clearance periods. The patients were in the supine position throughout the investigation. All patients had a bladder catheter placed before the clearance periods to ensure correct urine sampling.
The infusion of tracers was prepared in 60 mL of isotonic saline with 16 MBq of 51Cr–ethylene diamine tetraacetic acid (EDTA; GE-Healthcare, Hilleroed, Denmark) and 10 MBq of 131I-hippuran (GE-Healthcare). At 9:00 AM, a priming dose of 8 mL of the 51Cr-EDTA and 131I-hippuran solution was given as a rapid intravenous bolus injection together with 6.5 MBq of 51Cr-EDTA, which was followed by a constant infusion of 8 mL/h (P 300 pump, Kivex, Hoersholm, Denmark) for 3.5 hours for a total of 10 MBq. 51Cr-EDTA and 131I-hippuran were used to determine the glomerular filtration rate (GFR) and effective renal plasma flow. After an equilibrium period of 2 hours, blood samples were drawn for analyses of the plasma lithium, sodium, osmolality, 51Cr-EDTA, and 131I-hippuran. The blood sampling was immediately followed by urine collection from the bladder catheter. The urine volume was recorded, and the samples were assayed for lithium, sodium, osmolality, 51Cr-EDTA, and 131I-hippuran. A gamma counter (1480 Wizard 3, Wallac, Turku, Finland) was used to assess the radioactivity of 51Cr-EDTA and 131I-hippuran in the samples. The samplings were repeated at 30-minute intervals, and this resulted in 3 clearance periods after equilibration and before the intervention. Thereafter, patients with nonrefractory ascites were randomized to an infusion of 2 mg of terlipressin (Ferring Pharmaceuticals, Copenhagen, Denmark) or 10 mL of isotonic saline, whereas all patients with refractory ascites received 2 mg of terlipressin. Urine and blood sampling for renal function tests was then repeated for 3 more clearance periods of 30 minutes. Blood samples for vasoactive substances were obtained after the second clearance period at the baseline and after terlipressin or the placebo.
Clearance during the steady state was calculated by the standard formula Cx = Ux × Vu/Px, where Cx is the renal clearance of substance x, Ux is the concentration in urine of substance x, Vu is the urinary flow rate, and Px is the mean plasma concentration of substance x in the clearance period. Lithium clearance (CLi) is used as a marker of proximal sodium reabsorption under the assumption that lithium is filtered freely across the glomerulus and is reabsorbed in proportion to sodium and water in the proximal tubules and no reabsorption or secretion takes place in the distal tubules.17 The fractional excretion (FE) of x is calculated as follows: FE = Cx/GFR. The free water clearance (CH2O) is determined as follows: CH2O ′ Vu − COsm, where COsm is the clearance of osmotic substances determined by the standard clearance formula. The proximal fractional resorption (PFR) of sodium and water is estimated as 1 − CLi/GFR.17 The distal fractional resorption of sodium (DFRNa) is estimated as 1 − CNa/CLi, where CNa is the sodium clearance.17
Plasma concentrations of norepinephrine were determined by high-performance liquid chromatography, as described elsewhere.18 The intra-assay and interassay coefficients of variation were 8% and 9%, respectively. The plasma renin concentration was determined with a commercially available 2-site immunoradiometric assay (DGR International, Inc., Hamburg, Germany). The mean plasma concentration of renin in 536 healthy subjects was 26 pg/mL (range: 5.2–33.4).19 Aldosterone was measured with a commercial radioimmune assay kit (DSL-8600, Diagnostic Systems Laboratories, Inc., Webster, TX). The mean morning plasma concentration in 73 healthy adults in the supine position was 192 pmol/L (range: 80–450).19 Plasma calcitonin gene–related peptide (CGRP) was analyzed radioimmunologically, as described elsewhere.20 The intra-assay and interassay coefficients of variation were 4% and 7%, respectively. The mean concentration of CGRP in the plasma of normal subjects was 37 pmol/L (range: 24–50).19 N-terminal pro-atrial natriuretic peptide (pro-ANP; 1–30) was measured radioimmunologically with antiserum and calibrator material from Peninsula Laboratories (Los Angeles, CA) and a tracer prepared in house, as described elsewhere.21 The intra-assay and interassay coefficients of variation were 2.3% and 6.8%, respectively. The mean plasma concentration in 48 healthy subjects was 1411 pg/mL (range: 479–4669).19
Plasma and urinary lithium concentrations were measured by atomic absorption spectrophotometry (PerkinElmer 2380). Sodium in plasma and urine was measured by flame emission photometry (PerkinElmer 2380). Plasma and urine osmolarities were measured by the method of freezing-point depression (Osmomat 030-D, Gonotec, Berlin, Germany).
The study was conducted according to GCP and was approved and monitored by the GCP unit of Copenhagen University Hospital. Furthermore, the study was approved and inspected by the Danish Medicines Agency (EudraCT no. 2004.000568-29). The regional ethics committee also approved the study (KF 02-059/04), which was registered on clinicaltrials.gov (NCT00115947).
For the estimation of patient numbers, a type 1 error of 0.05 and a type 2 error of 0.20 were chosen. The standard deviation (SD) of the estimate of renal function in these patients was approximately 20%.22 In a paired design, 8 patients are required for the detection of a difference of 20% after terlipressin treatment. We did not expect any change in the renal function in the control group during the short study period. This assumption was based on a previous study, the same methods being applied without changes in the placebo group.22 However, the stimulation of diuresis with 200 mL of water every half hour may increase CH2O. The results are expressed as the mean ± the SD of the 3 clearance periods before and after terlipressin or the placebo. Illustrating mean values ignores the time response; however, analyses using summary measures (for example, the final level and the change from the first measurement to the last) did not change the statistical outcomes. Vasoactive substances are additionally shown as medians and total ranges because of nonnormal distributions. Statistical analyses were performed with an unpaired Student t test, a Mann-Whitney test and a paired Student t test, or a Wilcoxon test, as appropriate. All reported P values are 2-tailed, with values less than 0.05 considered significant. The SPSS 10.1 statistical package (SPSS, Inc., Chicago, Il) was applied throughout the study.
The groups consisting of patients with nonrefractory ascites randomized to either terlipressin (N group) or the placebo (P group) were identical with respect to demographic, clinical, and biochemical variables (Table 1). The serum alanine aminotransferase was higher in the N group (P < 0.05), but only 1 patient in the ascites group had a value of 113 U/L, which exceeded the reference interval. In the refractory ascites group (R group), the plasma albumin was, as expected, somewhat lower (P < 0.05), and the model for end-stage liver disease score was borderline-significantly higher (P = 0.06) than the P group (Table 1).
|R Group (Refractory Ascites + Terlipressin; n = 8)||N Group (Nonrefractory Ascites + Terlipressin; n = 11)||P Group (Nonrefractory Ascites + Placebo; n = 4)|
|Age (years)||54 ± 7.8||58 ± 7.9||58 ± 9.5|
|Child-Pugh score||10.5 ± 1.2||9.0 ± 2.2||7.8 ± 1.5|
|MELD score||13.2 ± 6.4*||9.6 ± 5.2||5.6 ± 4.4|
|Spironolactone (mg/day)||182 ± 160||166 ± 106||113 ± 63|
|Furosemide (mg/day)||140 ± 81||62 ± 21||100 ± 85|
|Plasma coagulation factors II, VII, and X (units; 0.70–1.30)||0.57 ± 0.27||0.56 ± 0.14||0.70 ± 0.14|
|Serum sodium (mmol/L; 136–146)||132 ± 6||135 ± 4||136 ± 3|
|Serum creatinine (μmol/L; 60–130)||126 ± 47||75 ± 19||72 ± 26|
|Serum albumin (μmol/L; 540–800)||383 ± 63†||480 ± 96||526 ± 77|
|Blood hemoglobin (mmol/L; males: 8.0–11.0, females: 7.0–10.0)||7.5 ± 1.5||7.4 ± 1.2||7.3 ± 0.7|
|HR (minute−1)||67 ± 19||72 ± 10||87 ± 17|
|MAP (mm Hg)||83 ± 16||92 ± 12||88 ± 10|
After the infusion of terlipressin, the mean arterial blood pressure (MAP) increased by 16 ± 16 mm Hg (mean change ± SD; P < 0.005) in the N group and by 19 ± 11 mm Hg (P < 0.005) in the R group, whereas no change was observed in the P group (1 ± 10 mm Hg). A corresponding decrease in the heart rate occurred in the N group (12 ± 9 minutes−1, P < 0.005) and in the R group (13 ± 9 minutes−1, P < 0.01). The heart rate was unaltered in the P group [−0.3 ± 3.0 minutes−1, not significant (NS)].
Renal Perfusion and Glomerular Filtration [GFR, Renal Blood Flow (RBF), and Filtration Fraction (FF)].
At the baseline, there were no differences between the N group and the P group with respect to GFR, RBF (Fig. 1), and FF (Table 2); GFR (P < 0.005), RBF (P < 0.05; Fig. 1), and FF (P < 0.05) were significantly lower in the R group than in the P and N groups. A significant increase in GFR of approximately 30% was observed in both treatment groups after terlipressin. In the N group, GFR increased from 69 ± 19 to 92 ± 25 mL/min (P < 0.005), and in the R group, it increased from 31 ± 19 to 41 ± 31 mL/min (P < 0.05). No change occurred in the placebo group (Fig. 1). RBF (mL/min) did not change significantly in the N and R groups (566 ± 237 versus 632 ±199 mL/min, P = 0.31, and 370 ± 248 versus 437 ± 255 mL/min, P = 0.16, respectively). FF increased significantly in the N group (0.20 ± 0.05 versus 0.23 ± 0.04, P < 0.05; Table 2). There was no linear correlation between the improvement in GFR and RBF and the change in MAP. However, the improvement in GFR correlated with the Child-Pugh score (r = 0.42, P = 0.04).
|R Group (Refractory Ascites; n = 8)||N Group (Nonrefractory Ascites; n = 11)||P Group (Nonrefractory Ascites; n = 4)|
|Baseline||After Terlipressin||Baseline||After Terlipressin||Baseline||Placebo|
|FF (%)||0.15 ± 0.09‡||0.15 ± 0.05||0.20 ± 0.05||0.23 ± 0.04*||0.18 ± 0.04||0.19 ± 0.05|
|Vu (mL/min)||1.1 ± 0.8§||1.3 ± 0.9||2.0 ± 1.5||2.2 ± 1.6||3.0 ± 1.1||3.0 ± 0.9|
|CH2O (mL/min)||−0.04 ± 0.9‡||−0.92 ± 0.4†||−0.13 ± 0.8§||−0.32 ± 0.5||0.97 ± 069||1.44 ± 0.7|
|Uosm (mOsm/kg)||394 ± 191‡||379 ± 105||377 ± 165‡||441 ± 112*||237 ± 75||141 ± 41|
|ULi (mmol/L)||1.87 ± 2.43‡||1.66 ± 1.53||2.62 ± 1.83||2.33 ± 1.64||2.70 ± 2.10||1.31 ± 0.47*|
|UNa (mmol/L)||12 ± 18‡||27 ± 23†||66 ± 41‡||87 ± 36†||38 ± 26||32 ± 23|
|PFR (%)||0.83 ± 0.08§||0.80 ± 0.10||0.75 ± 0.1||0.76 ± 0.12||0.74 ± 0.03||0.78 ± 0.06|
|DFRNa (%)||0.98 ± 0.02‡||0.97 ± 0.03||0.95 ± 0.03||0.94 ± 0.04||0.95 ± 0.04||0.95 ± 0.03|
|FeNa (%)||0.003 ± 0.003§||0.007 ± 0.009*||0.01 ± 0.01||0.02 ± 0.02||0.014 ± 0.01||0.011 ± 0.01|
|FeLi (%)||0.17 ± 0.08§||0.20 ± 0.10||0.25 ± 0.10||0.24 ± 0.12||0.26 ± 0.03||0.22 ± 0.06*|
Renal Clearances of Electrolytes and Water.
The effects of terlipressin and the placebo on CNa (mL/min), CLi (mL/min), COsm (mL/min), and CH2O (mL/min) are shown in Fig. 2.
In the R group, all clearances at the baseline were significantly lower than those in the P group (Fig. 2). In the N group, the baseline CH2O value was lower than that in the P group (P < 0.05). In the N group, terlipressin induced a significant increase in CNa (0.89 ± 0.21 versus 1.52 ± 1.45 mL/min, P < 0.05), CLi (17.3 ± 8.9 versus 21.5 ± 11.6 mL/min, P < 0.05), and COsm (2.1 ± 0.8 versus 3.1 ± 2.0 mL/min, P < 0.05) and a corresponding drop in CH2O (0.0 ± 0.9 versus −0.92 ± 0.4 mL/min, P < 0.005). In the R group, terlipressin induced a significant increase in CNa (0.11 ± 0.18 versus 0.35 ± 0.40 mL/min, P < 0.05) and CLi (5.5 ± 4.2 versus 9.5 ± 8.55 mL/min, P < 0.05). The changes in COsm (1.23 ± 0.94 versus 1.63 ± 1.05 mL/min) and CH2O (−0.1 ± 0.9 versus −0.3 ± 0.5 mL/min) were not significant in the R group. On the contrary, in the P group, there were decreases in COsm (2.0 ± 0.4 versus 1.5 ± 0.5 mL/min, P < 0.05), CLi (17.3 ± 1.9 versus 14.1 ± 3.2 mL/min, NS), and CNa (0.87 ±0.65 versus 0.74 ± 0.50 mL/min, NS) and an increase in CH2O (1.0 ± 0.7 versus 1.4 ± 0.7 mL/min, NS).
Renal Sodium and Lithium Handling.
At the baseline in the R group, the urinary flow rate (Vu; P < 0.005), urinary lithium concentration (P < 0.05), urine sodium concentration (UNa; P < 0.05), fractional sodium excretion (P < 0.005), and fractional lithium excretion (P < 0.005) were significantly lower than those in the P group, and the proximal and distal fractional sodium reabsorption (PFR, P < 0.005; DFRNa, P < 0.05) and urine osmolality (UOsm; P < 0.05) were significantly higher (Table 2). In the N group, UOsm (P < 0.05) and UNa (P < 0.05) were higher than those in the P group.
After terlipressin, UOsm increased by 17% in the N group (P < 0.05), whereas no change was observed in the R group. In the P group, UOsm decreased by 40% (P = 0.07) after the placebo (Table 2). Vu did not change in any of the groups. UNa increased significantly in both groups after terlipressin (P < 0.005, Table 2). The urinary lithium concentration was unaltered after terlipressin but exhibited a significant drop in the P group (P < 0.05; Table 2).
PFR and DFRNa did not change after terlipressin. The fractional sodium excretion increased by 233% in the R group (P < 0.05, Table 2) and showed a borderline-significant increase in the N group (39%, P = 0.07). The fractional lithium excretion did not change after terlipressin in contrast to a significant decrease in the P group (P < 0.05).
Terlipressin induced a significant reduction in the circulating levels of norepinephrine and renin in both the N and R groups (P < 0.05) and a significant increase in pro-ANP (P < 0.05) and CGRP (P < 0.05; Table 3). We observed an increase in aldosterone in the N group (median increase: 9%, P < 0.05) and no change in the R group (−5%, NS). No change in epinephrine was observed. All hormones remained unchanged in the P group.
|R Group (Refractory Ascites; n = 8)||N Group (Nonrefractory Ascites; n = 11)||P Group (Nonrefractory Ascites; n = 4)|
|Baseline||After Terlipressin||Baseline||After Terlipressin||Baseline||Placebo|
|Norepinephrine (nmol/L)||0.99 (0.31–4.41)||0.59 (0.24–1.48)*||0.79 (0.21–2.40)||0.52 (0.16–1.52)*||1.25 (0.19–1.73)||1.03 (0.69–2.35)|
|Renin (pg/mL)||339 (7–4,003)||164 (7–2,221)*||17 (8–1,215)||8 (7–810)*||19 (9–214)||13 (7–253)|
|Aldosterone (pmol/L)||2,229 (118–13,659)||2,269 (612–14,538)||468 (73–10,329)||573 (260–11,286)*||378 (114–1,729)||209 (106–1,574)|
|CGRP (pmol/L)||125 (67–234)||129 (70–237)*||102 (30–185)||106 (29–205)*||107 (90–126)||99 (88–121)|
|Pro-ANP (pg/mL)||1,876 (657–3,793)||3,237 (771–3,551)*||1,075 (477–2,069)||1,352 (1,008–2,462)†||927 (871–1,634)||940 (885–1,575)|
Eleven of the patients had loose stools. Three had abdominal cramps, and 1 also had nausea and vomited. All observed side effects were self-limiting.
The major new findings in this pathophysiological study are that the acute effect of the V1 receptor agonist terlipressin induces a significant improvement in the renal function in patients with refractory and nonrefractory ascites without HRS. It improves the GFR and the urinary clearances of sodium, lithium, and osmoles and ameliorates the activation of potent vasoactive systems responsible for renal vasoconstriction and renal sodium and water retention in patients with ascites without HRS.
Several clinical studies have evaluated the efficacy of terlipressin in HRS.7–13 Only a few studies have investigated the renal effects of vasoconstrictors in patients with ascites without HRS. Two different receptor systems have been approached: the V1 vasopressin receptors and the alpha-1-adrenoceptors. In 8 patients with refractory ascites without HRS, Gadano et al.23 found an increase in the renal perfusion pressure and RBF after terlipressin but no significant change in GFR or urinary sodium excretion. However, these findings may have been blurred, as the urine production was not stimulated by oral water ingestion and a catheter did not collect the urine, and only 3 patients had detectable urine sodium. Furthermore, renal clearances of electrolytes and water were not determined.
In a recent study, 12 patients with ascites were treated with the alpha-1-adrenergic agonist midodrine for 7 days.24 Following a delay of 3-5 days, a significant increase in GFR, UNa, Vu, and creatinine clearance was seen. In another study on acute effects of midodrine, an improvement in GFR and UNa was observed in patients with ascites, and no effect was seen in patients with type 2 HRS.25 Although the V1 receptor agonists induce splanchnic vasoconstriction, the effects of alpha-1-adrenergic agonists on splanchnic vasodilatation, which is considered a key factor in the pathogenesis of ascites,5 are unknown in patients with cirrhosis.
Some of the patients in the treatment groups were treated with beta-blockers (Table 1). For ethical reasons, we could not discontinue beta-blocker therapy for more than 3 days in patients with esophageal varices; however, beta-blockers do not seem to affect RBF and GFR,26, 27 and as propranolol has a half-life of 3-6 hours, the pharmacological effect at that point is probably negligible. None of the patients in the P group were on beta-blocker therapy because the 2 patients (50%) who had indications for beta-blocker therapy both had intolerance to beta-blockers.
An important factor contributing to ascites in patients with portal hypertension is splanchnic vasodilatation.4–6 In this study, we therefore approach the treatment of ascites with the understanding that ascites is due to splanchnic arterial vasodilatation, arterial underfilling, reduced renal perfusion pressure, and activation of vasoconstrictors (that is, the sympathetic nervous system and renin-angiotensin-aldosterone system). Terlipressin activates the V1 receptors, which are predominantly located in the vasculature in the splanchnic region, causes vasoconstriction,28 and thereby reduces the splanchnic arterial vasodilatation and portal pressure and ameliorates the hyperdynamic circulation.14, 29 This improves the effective circulatory volume and renal perfusion pressure.23, 29 In this study, we showed that these improvements in hemodynamics are associated with an increase in GFR and a deactivation of vasoconstrictors and sodium-conserving hormones (that is, norepinephrine and renin).
We observed an increase in CLi, which reflects an increase in the delivery of sodium and water from the proximal straight tubules to the loops of Henle.17, 30 As PFR is unchanged, the increase in CLi is most likely the result of the increase in GFR. Because the kidneys maintain the glomerulotubular balance, an increased GFR will, in general, be associated with a nearly constant proximal fractional reabsorption. The result of the increase in GFR and the delivery of sodium and water from the proximal straight tubules (CLi) is increased sodium excretion, as seen by the increase in CNa and COsm and the increase in UNa and UOsm. The use of CLi as a marker of intrarenal sodium handling in patients with a severe reduction of fractional sodium clearance has been questioned. The main reason is a potential distal reabsorption of lithium. However, in a study by Angeli et al.31 of patients with cirrhosis with ascites and avid sodium retention, no reabsorption in the distal tubule was found.31 A negative CH2O value in the treatment groups represents hypertonic urine, in contrast to the urine in the placebo group, which becomes more hypotonic. The mean value of CH2O in the P group in the 3 baseline clearance periods was higher (Fig. 2B) than that in the N and R groups. The levels of CH2O were identical in the first baseline clearance period; however, the P group showed a more pronounced increase in CH2O during the baseline clearance periods (data not shown). This probably represents a slight difference in the ability to suppress vasopressin in response to the 200-mL oral water load that the patients were given every half hour.32 This also held true in the N group; however, in the R group, CH2O did not change. This corresponds to the nonrefractory and refractory disease stages, respectively.
Although the major reasons for increased natriuresis after terlipressin are most likely the increased MAP and the improvement in the hemodynamics, the natriuretic effect of terlipressin will be enhanced by decreased sympathetic nerve activity (decreased plasma norepinephrine), decreased renin secretion, and increased atrial natriuretic peptide (ANP) secretion. The mechanism of release of ANP from the heart is mainly facilitated by an increase in the atrial pressure and stretching of the atria. However, an additional pressure-independent release may exist. It has been shown that ANP secretion increases in response to vasopressin analogs and pressor agents.33 High activity in the sympathetic nervous system decreases RBF by alpha-1-adrenergic receptors and increases sodium reabsorption and renin secretion by beta-1-adrenergic receptors in the juxtaglomerular cells.34, 35 The decrease in norepinephrine therefore contributes to the increased perfusion and increased sodium excretion. The increase in plasma aldosterone in group R was, however, small (median 9%) in light of the range of 72-10,320, despite a reduction of plasma renin probably due to the delay in this system. Thus, the half-life of aldosterone in cirrhosis is rather long (mean: 63-112 minutes).36, 37
Although this is a pathophysiological study of the acute effects of terlipressin and extensions to therapy should be conducted very carefully, the study has implications for further research and a new hypothesis. Dosage regimens and especially ischemic side effects should be further evaluated. In patients with HRS treated with terlipressin, about 15% discontinue therapy because of side effects.7–13 However, we believe that our study provides a proof of concept of the arterial vasodilation hypothesis of sodium retention in cirrhosis. From a pathophysiological viewpoint, the perfect drug for treating ascites in cirrhosis would be a combination of the V1 receptor agonist and vasopressin 2 (V2) receptor antagonist. The V1 receptor agonist terlipressin ameliorates the hyperdynamic circulation and increases GFR and the delivery of tubular fluid to the distal nephron, causing natriuresis. However, the increased natriuresis is associated with increased UOsm and decreased CH2O. The decreased CH2O value points to increased water reabsorption in the collecting ducts, which are the sites of action of the V2 receptor antagonists. The V2 receptor antagonists are drugs that interfere with the renal effects of antidiuretic hormones and inhibit water reabsorption in the collecting ducts and cause aquaresis.38 A V2 receptor antagonist has been proven effective in patients with cirrhosis and hyponatremia.39 However, the isolated effect of aquaretics in patients with ascites without hyponatremia is questionable as natriuresis is essential for the treatment and there is a risk of hypernatremia.
In conclusion, the V1 receptor agonist terlipressin improves renal function and induces natriuresis in patients with cirrhosis and ascites without HRS. Vasoconstrictors may represent a novel future treatment modality for these patients.