Hyponatremia: evaluation and management

Hyponatremia in patients with cancer

PURPOSE OF REVIEW

Hyponatremia is seen commonly in patients with cancer and is associated with increased mortality and morbidity. Understanding the proper diagnosis and therapy of cancer-associated hyponatremia is critical to ensure improved outcomes.

RECENT FINDINGS

The most common cancers associated with hyponatremia are the various forms of lung cancer with incidences approaching 25-45%. The most common causes of hyponatremia in cancer patients are the syndrome of inappropriate antidiuretic hormone secretion [syndrome of inappropriate antidiuretic hormone (ADH)] and volume depletion. Proper diagnosis rests on clinical information supplemented by laboratory studies and is critical to ensure appropriate therapy. In recent years, the development of drugs that specifically antagonize the vasopressin type 2 receptor in the distal tubule have offered targeted and highly effective therapies for syndrome of inappropriate ADH.

SUMMARY

Hyponatremia in cancer patients generally indicates advanced or severe disease but proper therapy that targets the underlying process can improve outcomes.

Electrolyte disorders with platinum-based chemotherapy: mechanisms, manifestations and management

Platinum chemotherapy, particularly cisplatin, is commonly associated with electrolyte imbalances, including hypomagnesemia, hypokalemia, hypophosphatemia, hypocalcemia and hyponatremia. The corpus of literature on these dyselectrolytemias is large; the objective of this review is to synthesize the literature and summarize the mechanisms responsible for these particular electrolyte disturbances in the context of platinum-based treatment as well as to present the clinical manifestations and current management strategies for oncologists and primary care physicians, since the latter are increasingly called on to provide care for cancer patients with medical comorbidities. Correct diagnosis and effective treatment are essential to improved patient outcomes.

Dehydration, Hypernatremia, and Hyponatremia

Disturbances of serum sodium are one of the most common findings in older persons. They are also a major cause of hospital admissions and delirium and are associated with frailty, falls, and hip fractures. Both hypernatremia and hyponatremia are potentially preventable. Treatment involves treating the underlying cause and restoring sodium and volume status to normal. The arginine vasopressin antagonists, vaptans, have increased the therapeutic armamentarium available to physicians.

A prospective study to compare the clinical efficacy of Tolvaptan with 3% hypertonic saline solution in hospitalized patients having hyponatremia

Objective:

Hyponatremia is one of the most common electrolyte abnormalities in hospitalized patients. The treatment of hyponatremia is controversial as rapid correction of serum sodium can give rise to neurologic disorder and at the same time if not corrected timely, it can lead to brain damage. The aim of this study was to compare the efficacy of Tolvaptan with 3% hypertonic saline solution for the management of hyponatremia in hospitalized patients.

Methods:

In this prospective observational study, data of 60 hospitalized patients having hyponatremia from February 2013 to July 2013 were collected and analyzed. Patients either received oral Tolvaptan or intravenous infusion of 3% hypertonic saline solution. The serum sodium concentration before administration of treatment and 24 h and 48 h after the administration of the drugs were recorded and analyzed. Data were analyzed using GraphPad Software, by Student's paired t-test and one-way analysis of Variance (ANOVA).

Findings:

Tolvaptan and 3% hypertonic saline solution had significant effects in raising serum sodium level in hyponatremic patients at both 24 h and 48 h (P < 0.0001). This increase was about 8.030 ± 0.6507 mEq/L and 12.33 ± 0.6489 mEq/L for 3% hypertonic saline and about 5.111 ± 0.6616 mEq/L and 10.11 ± 0.6230 mEq/L for Tolvaptan, after 24 h and 48 h, respectively.

Conclusion:

Both drugs had significant effects in raising serum sodium level in hyponatremic patients; however administration of 3% hypertonic saline solution had a slightly superior efficacy in raising the serum sodium concentration at both 24 h and 48 h periods in Hyponatremic patients compared with oral Tolvaptan.

Hyponatraemia in cancer: association with type of cancer and mortality

Hyponatraemia is common in patients with cancer. The objectives of this study are to investigate the severity distribution of hyponatraemia and its association with mortality. We retrospectively reviewed medical records for patients admitted to a national centre for cancer care and research in Qatar between 2008 and 2012. A model was built through multivariate analyses to investigate the role of hyponatraemia in mortality. Patients were grouped into those who had moderate-severe hyponatraemia (Na < 130) and those who only had normal-mild hyponatraemia (Na ≥ 130). A total of 2048 patients were included in this study. Prostate (57.1%), pancreatic (50%), liver (49%) and lung (40.2%) cancers showed the highest frequency of moderate-severe hyponatraemia, while breast cancer showed the lowest frequency at 23.5%. In the multivariate analyses, patients with moderate-severe hyponatraemia (Na < 130 mmol/L) were 4.28 times more likely to die than those with normal-mild hyponatraemia (Na ≥ 130) (P < 0.05). The present study shows that hyponatraemia is a common electrolyte disturbance among hospitalised patients with cancer diagnoses. The severity of hyponatraemia was a statistically significant independent factor associated with higher in-hospital mortality. This is in accordance with the reported literature and emphasises the importance of early diagnosis and correction of hyponatraemia.

Severe neurological symptoms in a patient with advanced renal cell carcinoma treated with sunitinib

Neurological symptoms are uncommon in patients administered sunitinib therapy; however, a few cases of dramatic neurotoxicity attributable to the development of reversible posterior leukoencephalopathy syndrome have been reported. Here, we report a case of a 71-year old woman with severe neurological symptoms occurring during sunitinib therapy for metastatic renal cell carcinoma. The clinical symptoms were typical for reversible posterior leukoencephalopathy syndrome, but there were no accompanying neuroimaging abnormalities. A Naranjo probability score of 3 indicates the adverse drug reaction was possible, but we discuss other potential causes of this event.

Diagnosis and management of hyponatremia in cancer patients

Hyponatremia, a common electrolyte abnormality in oncology practice, may be a negative prognostic factor in cancer patients based on a systematic analysis of published studies. The largest body of evidence comes from small-cell lung cancer (SCLC), for which hyponatremia was identified as an independent risk factor for poor outcome in six of 13 studies. Hyponatremia in the cancer patient is usually caused by the syndrome of inappropriate antidiuretic hormone (SIADH), which develops more frequently with SCLC than with other malignancies. SIADH may be driven by ectopic production of arginine vasopressin (AVP) by tumors or by effects of anticancer and palliative medications on AVP production or action. Other factors may cause hypovolemic hyponatremia, including diarrhea and vomiting caused by cancer therapy. Hyponatremia may be detected on routine laboratory testing before or during cancer treatment or may be suggested by the presence of mostly neurological symptoms. Treatment depends on several factors, including symptom severity, onset timing, and extracellular volume status. Appropriate diagnosis is important because treatment differs by etiology, and choosing the wrong approach can worsen the electrolyte abnormality. When hyponatremia is caused by SIADH, hypertonic saline is indicated for acute, symptomatic cases, whereas fluid restriction is recommended to achieve a slower rate of correction for chronic asymptomatic hyponatremia. Pharmacological therapy may be necessary when fluid restriction is insufficient. The orally active, selective AVP receptor 2 (V(2))-receptor antagonist tolvaptan provides a mechanism-based option for correcting hyponatremia caused by SIADH or other conditions with inappropriate AVP elevations. By blocking AVP effects in the renal collecting duct, tolvaptan promotes aquaresis, leading to a controlled increase in serum sodium levels.

Hyponatremia in cirrhosis and end-stage liver disease: treatment with the vasopressin V₂-receptor antagonist tolvaptan

Hyponatremia is common in patients with cirrhosis and portal hypertension, and is characterized by excessive renal retention of water relative to sodium due to reduced solute-free water clearance. The primary cause is increased release of arginine vasopressin. Hyponatremia is associated with increased mortality in cirrhotic patients, those with end-stage liver disease (ESLD) on transplant waiting lists, and, in some studies, posttransplantation patients. Clinical evidence suggests that adding serum sodium to model for ESLD (MELD) scoring identifies patients in greatest need of liver transplantation by improving waiting list mortality prediction. Hyponatremia is also associated with numerous complications in liver disease patients, including severe ascites, hepatic encephalopathy, infectious complications, renal impairment, increased severity of liver disease in cirrhosis, and increased hospital stay and neurologic/infectious complications posttransplant. Vasopressin receptor antagonists, which act to increase free water excretion (aquaresis) and thereby increase serum sodium concentration, have been evaluated in patients with hypervolemic hyponatremia (including cirrhosis and heart failure) and euvolemic hyponatremia (SIADH). Tolvaptan, a selective vasopressin V(2)-receptor antagonist, is the only oral agent in this class approved for raising sodium levels in hypervolemic and euvolemic hyponatremia. The SALT trials showed that tolvaptan treatment rapidly and effectively resolved hyponatremia in these settings, including cirrhosis, and it has been shown that this agent can be safely and effectively used in long-term treatment. Fluid restriction should be avoided during the first 24 h of treatment to prevent overly rapid correction of hyponatremia, and tolvaptan should not be used in patients who cannot sense/respond to thirst, anuric patients, hypovolemic patients, and/or those requiring urgent intervention to raise serum sodium acutely.

Hyponatremia in hospitalized patients: the potential role of tolvaptan

Hyponatremia (typically defined as serum sodium level < 135 mEq/L) is a common electrolyte abnormality among hospitalized patients. Whether present at admission or acquired during hospitalization, hyponatremia is associated with higher mortality and longer hospital stays. Failure to adequately investigate and treat hyponatremia may also be associated with adverse outcomes. The presence and severity of clinical symptoms largely depend on the rate and extent of the decline in serum sodium; rapid or large decreases may cause serious neurologic complications. The approach to treatment depends on the presence and severity of symptoms, the timing of their onset, the underlying etiology, and the patient's volume status. Patients with euvolemic or hypervolemic hyponatremia usually have inappropriately elevated levels of arginine vasopressin, which stimulates water reabsorption even in the presence of low serum osmolality. Tolvaptan is an orally active, selective V2-receptor antagonist that blocks the effects of arginine vasopressin in the renal collecting duct to promote aquaresis without increasing sodium or potassium excretion; as a result, it increases serum sodium in a controlled manner. Tolvaptan offers a mechanism-based treatment option for patients with euvolemic or hypervolemic hyponatremia who have serum sodium levels < 125 mEq/L or persistent symptoms resistant to fluid restriction.

Gender difference in antidiuretic response to desmopressin

Increased age and female gender are well-known risk factors for the development of desmopressin-induced hyponatremia. However, little focus has been on exploring gender differences in the antidiuretic response to desmopressin. Based on an exploratory analysis from three clinical trials, we report a significant gender difference in the effects of desmopressin on nocturnal urine volume that could not be explained by pharmacokinetic differences. Mean desmopressin concentration profiles were tested for covariates, and age and gender were not statistically significant and only weight was significant for log(C(max)) (P = 0.0183) and borderline significant for log(AUC) (P = 0.0571). The decrease in nocturnal urine volume in nocturia patients treated with desmopressin over 28 days was significantly larger for women at the lower desmopressin melt doses of 10 and 25 μg than for men. The ED(50) for men was modeled to be 43.2 μg and 16.1 μg for women, with the ED(50) men/women estimated to be 2.7 (1.3-8.1 95% CI), corresponding to significantly higher sensitivity to desmopressin in women. An increasing incidence of hyponatremia with increasing dose was found, and at the highest dose level of 100 μg decreases in serum sodium were approximately twofold greater in women over 50 yr of age than in men. A new dose recommendation stratified by gender is suggested in the treatment of nocturia: for men, 50- to 100-μg melt is an efficacious and safe dose, while for women a dose of 25 μg melt is recommended as efficacious with no observed incidences of hyponatremia. Areas for further research are proposed to uncover pathophysiological mechanism(s) behind these gender differences.