Efficacy and Safety of Combination Therapy with Tolvaptan and Furosemide in Children with Nephrotic Syndrome and Refractory Edema: A Prospective Interventional Study

OBJECTIVE

Severe edema in children with nephrotic syndrome is often refractory to conventional diuretics. Tolvaptan has been used satisfactorily for managing edema in patients with heart failure and cirrhosis. The safety and efficacy of combination therapy with oral tolvaptan and intravenous (IV) furosemide was assessed in patients with furosemide refractory edema.

METHODS

Patients, aged 5-18 y with nephrotic syndrome and severe edema, were screened for eligibility. After excluding hypovolemia, patients received IV furosemide (3-4 mg/kg/d) for 48 h. Those refractory to IV furosemide (weight loss < 3%) received tolvaptan (0.5-1 mg/kg once daily) and IV furosemide for the next 48 h. Parameters were compared between 48 h of furosemide alone and combination therapy.

RESULTS

A total of 24 patients (18 boys) with mean age of 8.0 ± 3.0 y were enrolled. Urine volume significantly increased with combination therapy as compared to furosemide therapy (mean difference: 1.2 mL/kg/h; 95% CI: 0.8-1.65 mL/kg/h) (p < 0.001). Compared to therapy with furosemide alone, combination therapy resulted in significant reduction in body weight from 26.9 ± 10.3 kg to 24.8 ± 9.7 kg (p < 0.001). Estimated glomerular filtration rate did not change (p = 0.81) but serum sodium increased from 135.7 ± 3.3 mEq/L to 140.4 ± 4.8 mEq/L (p < 0.001) with combination therapy; 2 patients showed asymptomatic hypernatremia.

CONCLUSION

The combination of oral tolvaptan and IV furosemide is effective in augmenting diuresis and reducing weight in patients with furosemide refractory edema but requires monitoring of electrolytes and volume status.

Mechanisms and management of edema in pediatric nephrotic syndrome

Edema is the abnormal accumulation of fluid in the interstitial compartment of tissues within the body. In nephrotic syndrome, edema is often seen in dependent areas such as the legs, but it can progress to cause significant accumulation in other areas leading to pulmonary edema, ascites, and/or anasarca. In this review, we focus on mechanisms and management of edema in children with nephrotic syndrome. We review the common mechanisms of edema, its burden in pediatric patients, and then present our approach and algorithm for management of edema in pediatric patients. The extensive body of experience accumulated over the last 5 decades means that there are many options, and clinicians may choose among these options based on their experience and careful monitoring of responses in individual patients.

Tolvaptan therapy to treat severe hyponatremia in pediatric nephrotic syndrome

BACKGROUND

Tolvaptan is a selective oral vasopressin V2-receptor antagonist. Some data have implicated stimulation of arginine vasopressin (AVP) as an important factor in oedema formation in a rodent model of nephrotic syndrome (NS) and adult NS patients. We report case of pediatric NS with severe hyponatremia efficiently treated by tolvaptan.

CASE/DIAGNOSIS - TREATMENT

A 22-month-old girl presented first with NS. She remained nephrotic after a 30-day course of oral steroids. Tacrolimus was inefficient and there was no response to plasma exchanges (15 sessions on a daily basis). She had severe oedema and ascites. Thus, in addition to immunosuppressive therapy, she received diuretics, furosemide 5 mg/kg/day, and amiloride 1 mg/kg/day, and required water restriction. She was hypertensive and was treated with a full dose of calcium inhibitor (amlodipine 0.5 mg/kg/day). After2 months of treatment, serum sodium reached 116 mmol/L and urinary osmolarity 547 mosmol/L, suggesting an inappropriate AVP secretion. Tolvaptan was introduced at 0.3 mg/kg/day and progressively increased to 3 mg/kg/day on day 4, leading to a partial correction of serum sodium (130 mmol/l) and a urinary osmolarity decrease to 90 mosmol/L. Tolvaptan was then continued at the dose of 3 mg/kg/day with unchanged serum sodium, without hypernatremia or dehydration. Her weight decreased from 14.8 k to 14 k, but oedema still persisted.

CONCLUSION

Tolvaptan was very efficient in this case of hyponatremia associated with steroid-resistant NS. Tolvaptan should be considered in the management of therapy-resistant hyponatremia in patients with NS.

Nephrotic Syndrome: Oedema Formation and Its Treatment With Diuretics

Oedema is a defining element of the nephrotic syndrome. Its' management varies considerably between clinicians, with no national or international clinical guidelines, and hence variable outcomes. Oedema may have serious sequelae such as immobility, skin breakdown and local or systemic infection. Treatment of nephrotic oedema is often of limited efficacy, with frequent side-effects and interactions with other pharmacotherapy. Here, we describe the current paradigms of oedema in nephrosis, including insights into emerging mechanisms such as the role of the abnormal activation of the epithelial sodium channel in the collecting duct. We then discuss the physiological basis for traditional and novel therapies for the treatment of nephrotic oedema. Despite being the cardinal symptom of nephrosis, few clinical studies guide clinicians to the rational use of therapy. This is reflected in the scarcity of publications in this field; it is time to undertake new clinical trials to direct clinical practice.

Effects of tolvaptan on renal function in chronic kidney disease patients with volume overload

Background

Fluid overload in chronic kidney disease (CKD) is generally controlled by diuretics, with potentially harmful effects on renal function. The efficacy of tolvaptan, a vasopressin V2-receptor antagonist and aquaretic, has not been evaluated for fluid control in CKD with reduced renal function.

Methods

Each patient from a group of 24 CKD patients on tolvaptan 15 mg/d plus conventional diuretics (T group) was matched by age and sex with a patient from a group of 24 CKD patients on conventional nonaquaretic diuretics alone not associated to tolvaptan other than tolvaptan (C group). Changes in renal function were compared between the groups for 1 year.

Results

There were no significant differences in blood pressure, hemoglobin levels, cardiac function, urine specific gravity, and urinary sodium concentration between the 2 groups at the beginning of the follow-up period and 1 year after. The estimated glomerular filtration rate (eGFR) by the formula developed by Japanese Society of Nephrology (in mL/min/1.73 m²) decreased: C group (from 28.3±13.6 to 23.0±12.3, p=0.09), T group (from 22.7±12.4 to 19.4±12.2, p=0.18), but both did not reach significance. A 50% reduction in eGFR was observed in 4 patients in the C group and 1 in the T group (p<0.05). A subgroup analysis performed on the patients with stage 3-4 CKD demonstrated a significant reduction in eGFR in the C group (n=17, p=0.04), but not in T group (n=17, p=0.07).

Conclusion

These results suggest that tolvaptan may have less effects on CKD progression among stage 3-4 CKD patients who are on conventional diuretics.

Effects of tolvaptan on urine output in hospitalized heart failure patients with hypoalbuminemia or proteinuria

Hypoalbuminemia is an independent prognostic factor in hospitalization for heart failure (HHF). Hypoalbuminemia or proteinuria is related to resistance to loop diuretics. Tolvaptan is an oral non-peptide, competitive antagonist of vasopressin receptor-2. It has been used for the treatment of volume overload in HHF patients in several Asian countries. Several studies have demonstrated marked improvement in congestion in HHF patients. However, whether tolvaptan is useful for HHF patients with hypoalbuminemia or proteinuria (both of which are related to resistance to loop diuretics) has not been clarified. We examined the diuretic response to tolvaptan in HHF patients with hypoalbuminemia or proteinuria. We defined hypoalbuminemia as a serum level of albumin < 2.6 g/dl. Fifty-one HHF patients who received additional tolvaptan upon therapies with loop diuretics were divided into the hypoalbuminemia group (n = 24) or control group (n = 27). The changes in urine output per day were not different between the two groups [610 (range 100–1032); 742 (505–1247) ml, P = 0.313]. There was no difference in diuretic responses between patients with and without proteinuria. The serum level of albumin did not correlate with changes in urine output per day after tolvaptan treatment (P = 0.276, r = 0.156). Thus, additional administration of tolvaptan elicited a good diuretic response in HHF patients with hypoalbuminemia or proteinuria. These data suggest that tolvaptan might be beneficial for such HHF patients.

Edematous Hyponatremia Treated with Tolvaptan in a Patient with Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) patients rarely present with either syndrome of inappropriate antidiuretic hormone secretion or generalized edema. Tolvaptan is a selective vasopressin V2 receptor antagonist that produces effective aquaresis, and its use in ALS patients has not been previously reported. A 50-year-old male ALS patient was admitted because of both generalized edema and dilutional hyponatremia. These manifestations were refractory to conventional diuretics and fluid therapy, but a very brisk diuresis was induced by tolvaptan administration. Edema and hyponatremia were also improved, and the patient was able to be discharged without tolvaptan. In this case report, we postulate how edema and dilutional hyponatremia developed in the patient, and discuss the mechanism of tolvaptan in treating hypervolemic hyponatremia. Further experience is necessary to evaluate the usefulness of tolvaptan in patients with neurological disorders.

Different Effects of Tolvaptan in Patients with Idiopathic Membranous Nephropathy with Nephrotic Syndrome

This case report discusses the clinical indication for immunosuppressants in patients with idiopathic membranous nephropathy (IMN). Because this disease occasionally shows spontaneous remission, it is necessary to determine the predictive values for a therapeutic effect in order to provide appropriate treatment. Two distinct cases described herein illustrate the different effects of tolvaptan in responders and non-responders, according to the pre-treatment levels of AQP-2 immunostaining in the samples from renal biopsy and urinary levels of AQP-2 and osmolality, suggesting that these values may be useful predictors of response to tolvaptan in patients with nephrotic IMN.

Pathophysiology, Evaluation, and Management of Edema in Childhood Nephrotic Syndrome

Generalized edema is a major presenting clinical feature of children with nephrotic syndrome (NS) exemplified by such primary conditions as minimal change disease (MCD). In these children with classical NS and marked proteinuria and hypoalbuminemia, the ensuing tendency to hypovolemia triggers compensatory physiological mechanisms, which enhance renal sodium (Na(+)) and water retention; this is known as the "underfill hypothesis." Edema can also occur in secondary forms of NS and several other glomerulonephritides, in which the degree of proteinuria and hypoalbuminemia, are variable. In contrast to MCD, in these latter conditions, the predominant mechanism of edema formation is "primary" or "pathophysiological," Na(+) and water retention; this is known as the "overfill hypothesis." A major clinical challenge in children with these disorders is to distinguish the predominant mechanism of edema formation, identify other potential contributing factors, and prevent the deleterious effects of diuretic regimens in those with unsuspected reduced effective circulatory volume (i.e., underfill). This article reviews the Starling forces that become altered in NS so as to tip the balance of fluid movement in favor of edema formation. An understanding of these pathomechanisms then serves to formulate a more rational approach to prevention, evaluation, and management of such edema.