Octreotide in the treatment of refractory ascites of cirrhosis

Agonists, Antagonists and Receptors of Somatostatin: Pathophysiological and Therapeutical Implications in Neoplasias

Somatostatin is a peptide that plays a variety of roles such as neurotransmitter and endocrine regulator; its actions as a cell regulator in various tissues of the human body are represented mainly by inhibitory effects, and it shows potent activity despite its physiological low concentrations. Somatostatin binds to specific receptors, called somatostatin receptors (SSTRs), which have different tissue distributions and associated signaling pathways. The expression of SSTRs can be altered in various conditions, including tumors; therefore, they can be used as biomarkers for cancer cell susceptibility to certain pharmacological agents and can provide prognostic information regarding disease evolution. Moreover, based on the affinity of somatostatin analogs for the different types of SSTRs, the therapeutic range includes conditions such as tumors, acromegaly, post-prandial hypotension, hyperinsulinism, and many more. On the other hand, a number of somatostatin antagonists may prove useful in certain medical settings, based on their differential affinity for SSTRs. The aim of this review is to present in detail the principal characteristics of all five SSTRs and to provide an overview of the associated therapeutic potential in neoplasias.

Pharmacology of Octreotide: Clinical Implications for Anesthesiologists and Associated Risks

Many patients presenting with a history of foregut, midgut neuroendocrine tumors (NETs) or carcinoid syndrome can experience life-threatening carcinoid crises during anesthesia or surgery. Clinicians should understand the pharmacology of octreotide and appreciate the use of continuous infusions of high-dose octreotide, which can minimize intraoperative carcinoid crises. We administer a prophylactic 500-μg bolus of octreotide intravenously (IV) and begin a continuous infusion of 500 μg/h for all NET patients. Advantages include low cost and excellent safety profile. High-dose octreotide for midgut and foregut NETs requires an appreciation of the pathophysiology involved in the disease, pharmacology, drug-drug interactions, and side effects.

Management of refractory ascites

Ascites that does not respond or recurs after high-dose diuresis and sodium restriction should be considered refractory ascites. As cirrhosis advances, the escaping fluid overwhelms the lymphatic return. Decrease in renal plasma flow leads to increased sodium reabsorption at the proximal tubule leading to decreased responsiveness to loop diuretics and mineralocorticoid antagonists, which work distally. These complex hemodynamic alterations lead to refractory ascites. In refractory ascites, high-dose diuresis (400 mg of spironolactone and 160 mg of furosemide) and sodium restriction (<90 mmol/d) result in inadequate weight loss and sub optimal sodium excretion (<78 mmol/d). Further use of diuretics is limited by complications such as encephalopathy, azotemia, renal insufficiency, hyponatremia, and hyperkalemia. Therapy for refractory ascites is limited. The available therapies are repeated large volume paracentesis (LVP), transjugular intrahepatic portosystemic shunts, peritoneovenous shunts, investigational medical therapies, and liver transplantation. LVP with concomitant volume expanders is the initial treatment of choice. Transjugular intrahepatic portosystemic seems to be superior to LVP in reducing the need for repeated paracentesis and improves the quality of life. Several treatments that act at different steps in the pathogenesis of ascites are investigational, and some show promising results. Splanchnic and peripheral vasoconstrictors (Octreotide, Midodrine, and Terlipressin) increase effective arterial volume and decrease activation of the renin-angiotensin system with resultant increase in renal sodium excretion. Clonidine when given with spironolactone has been shown to cause rapid mobilization of ascites by significantly decreasing the sympathetic activity and renin-aldosterone levels. Natural aquaretics and synthetic V2 receptor antagonists (satavaptan) are being evaluated for mobilization of ascites by increasing the excretion of solute-free water. Liver transplantation remains the only definitive therapy for refractory ascites. Because refractory ascites is a poor prognostic sign, liver transplantation should be considered and incorporated early in the treatment plan.

[Ascites, hepatorenal syndrome and spontaneous bacterial peritonitis in patients with portal hypertension]

Ascites, hepatic encephalopathy and variceal hemorrhage are three major complications of portal hypertension. The diagnostic evaluation of ascites involves an assessment of its etiology by determining the serum-ascites albumin gradient and the exclusion of spontaneous bacterial peritonitis. Ascites is primarily related to an inability to excrete an adequate amount of sodium into urine, leading to a positive sodium balance. Sodium restriction and diuretic therapy are keys of ascites control. But, with the case of refractory ascites, large volume paracentesis and transjugular portosystemic shunts are required. In hepatorenal syndrome, splanchnic vasodilatation with reduction in effective arterial volume causes intense renal vasoconstriction. Splanchnic and/or peripheral vasoconstrictors with albumin infusion, and renal replacement therapy are only bridging therapy. Liver transplantation is the only definitive modality of improving the long term prognosis.

The effect of 1 month of therapy with midodrine, octreotide-LAR and albumin in refractory ascites: a pilot study

BACKGROUND

The pathogenesis of refractory ascites (RA) is linked to splanchnic vasodilation. We hypothesized that a combination of midodrine, octreotide long-acting release (LAR) and albumin would result in increased natriuresis, better control of ascites and an improvement in renal function in patients with RA+/-Type 2 hepatorenal syndrome.

METHODS

A prospective pilot study in patients with RA as defined by the International Ascites Club. Consecutive patients received an intramuscular injection of octreotide-LAR, 50 g of albumin three times per week and midodrine titrated to increase the systolic blood pressure for 1 month.

RESULTS

Ten patients with RA were enrolled and eight with complete data to 1 month post-treatment were included in the analysis. There was no change in renal function but there was a trend towards a reduction in the volume of ascites removed by paracentesis (P=0.08) and a significant reduction in the plasma renin (P=0.01) and aldosterone concentrations (P=0.01). Interestingly, there was a transient worsening in the model for end-stage liver disease (MELD) score (P=0.01). The deterioration in MELD was completely reversible after discontinuation of therapy.

CONCLUSIONS

To our knowledge, this is the first study of prolonged midodrine, octreotide and albumin therapy in RA. We observed a significant reduction in the plasma renin and aldosterone concentrations and a trend towards a reduction in the volume of ascites removed by paracentesis without an effect on renal function. The beneficial effects are at the expense of a reversible deterioration in the MELD score. Large controlled trials are needed before this therapy can be routinely recommended.

Evaluation and management of patients with refractory ascites

Some patients with ascites due to liver cirrhosis become no longer responsive to diuretics. Once other causes of ascites such as portal vein thrombosis, malignancy or infection and non-compliance with medications and low sodium diet have been excluded, the diagnosis of refractory ascites can be made based on strict criteria. Patients with refractory ascites have very poor prognosis and therefore referral for consideration for liver transplantation should be initiated. Search for reversible components of the underlying liver pathology should be undertaken and targeted therapy, when available, should be considered. Currently, serial large volume paracentesis (LVP) and transjugular intrahepatic portasystemic stent-shunt (TIPS) are the two mainstay treatment options for refractory ascites. Other treatment options are available but not widely used either because they carry high morbidity and mortality (most surgical options) rates, or are new interventions that have shown promise but still need further evaluation. In this comprehensive review, we describe the evaluation and management of patients with refractory ascites from the prospective of the practicing physician.