Pharmacological management of hyponatremia

Efficacy and safety of V1a receptor antagonists in autism spectrum disorder: A meta-analysis

This meta-analysis has evaluated the efficacy and safety of V1a receptor antagonists in ASD compared to placebo. The reviewers extracted data from four relevant clinical trials after a literature search on databases and clinical trial registries. Quality assessment was done using the risk of bias assessment tool, and the random-effects model was used to estimate effect size. Subgroup analysis, meta-regression and sensitivity analysis were done. PRISMA guidelines were followed in the selection, analysis and reporting of findings. V1a receptor antagonists did not reduce Vineland II Adaptive behaviour composite score significantly (SMD: 0.14; 95% CI: -0.06-0.35; p = 0.16; PI: -0.44-0.73), communication domain subscale score and socialization domain subscale score. The change in daily living skills domain subscale score was significant and favourable for V1a receptor antagonists (SMD: 0.15; 95% CI: 0.03-0.26; p = 0.01). The subgroup analysis revealed a significant improvement in Vineland II Adaptive behaviour composite score with doses <10 mg (SMD: 0.45; 95% CI: 0.11-0.78; p = 0.009). Meta-regression does not show a significant association between SMD of ASD symptom score reduction with the duration and dose of V1a receptor antagonist therapy. Treatment-emergent adverse effects were not serious and dose dependent. Low doses (<10 mg) of V1a receptor antagonist may be effective in reducing the core symptoms of ASD compared to placebo; however, future active-controlled clinical trials are necessary to generate conclusive evidence.

Hyponatremia in Patients with Hematologic Diseases

Hyponatremia is the most common electrolyte disorder in clinical practice and is associated with increased morbidity and mortality. It is frequently encountered in hematologic patients with either benign or malignant diseases. Several underlying mechanisms, such as hypovolemia, infections, toxins, renal, endocrine, cardiac, and liver disorders, as well as the use of certain drugs appear to be involved in the development or the persistence of hyponatremia. This review describes the pathophysiology of hyponatremia and discusses thoroughly the contributing factors and mechanisms that may be encountered specifically in patients with hematologic disorders. The involvement of the syndrome of inappropriate antidiuretic hormone (SIADH) secretion and renal salt wasting syndrome (RSWS) in the development of hyponatremia in such patients, as well as their differential diagnosis and management, are also presented. Furthermore, the distinction between true hyponatremia and pseudohyponatremia is explained. Finally, a practical algorithm for the evaluation of hyponatremia in hematologic patients, as well as the principles of hyponatremia management, are included in this review.

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.

Risk factors for sodium overcorrection in non-hypovolemic hyponatremia patients treated with tolvaptan

PURPOSE

In this study, the risk factors associated with sodium overcorrection were investigated with an optimal cutoff for baseline serum sodium for use in daily clinical practice.

METHODS

Electronic medical records of patients who received tolvaptan for non-hypovolemic hyponatremia were reviewed. Demographic and clinical data including age, sex, weight, height, comorbidity, cause of hyponatremia, hypertonic saline use, and comedication were collected. Baseline laboratory parameters measured included serum sodium, serum potassium, serum creatinine, blood urea nitrogen, serum tonicity, ALT, AST, and urine osmolality. The primary outcome was the overcorrection of serum sodium, which was defined as an increase in serum sodium by more than 10 mmol/L in 24 h.

RESULTS

From a total of 77 patients included in the analysis, 24 (31.2%) showed sodium overcorrection (> 10 mmol/L/24 h); 2 (2.6%) in heart failure cohort, 17 (22.1%) in SIADH cohort, and 5 (6.5%) in unknown cause cohort. More than half of patients (51.9%) were administered hypertonic saline prior to tolvaptan. Hypertension, cancer, diuretics, baseline serum sodium, and SIADH were associated with the risk of overcorrection in the univariable analysis. Significant factors for the overcorrection from multivariable analysis were lower body mass index, presence of cancer (adjusted odds ratio, 10.87; 95% CI, 1.23-96.44), and lower serum sodium at baseline (adjusted odds ratio, 0.76 for every 1 mEq/L increase; 95% CI, 0.61-0.94).

CONCLUSION

The overcorrection of hyponatremia in non-hypovolemic patients treated with tolvaptan was significantly associated with lower body mass index, presence of cancer, and lower serum sodium at baseline. In subgroup analysis using SIADH patients, baseline sodium and cancer were found to be significant factors of overcorrection.

Arginine Vasopressin and Posterior Reversible Encephalopathy Syndrome Pathophysiology: the Missing Link?

Posterior reversible encephalopathy syndrome (PRES) is a clinicoradiological entity characterized by a typical brain edema. Its pathogenesis is still debated through hypoperfusion and hyperperfusion theories, which have many limitations. As PRES occurs almost exclusively in clinical situations with arginine vasopressin (AVP) hypersecretion, such as eclampsia and sepsis, we hypothesize that AVP plays a central pathophysiologic role. In this review, we discuss the genesis of PRES and its symptoms through this novel approach. We theorize that AVP axis stimulation precipitates PRES development through an increase in AVP secretion or AVP receptor density. Activation of vasopressin V_1a receptors leads to cerebral vasoconstriction, causing endothelial dysfunction and cerebral ischemia. This promotes cytotoxic edema through hydromineral transglial flux dysfunction and may increase endothelial permeability, leading to subsequent vasogenic brain edema. If our hypothesis is confirmed, it opens new perspectives for better patient monitoring and therapies targeting the AVP axis in PRES.