Hyponatraemia and the syndrome of inappropriate antidiuresis (SIAD) in cancer

Abstract

Hyponatraemia is a common electrolyte abnormality seen in a wide range of oncological and haematological malignancies, and confers poorer performance status, prolonged hospital admission and reduced overall survival, in patients with cancer. Syndrome of inappropriate antidiuresis (SIAD) is the commonest cause of hyponatraemia in malignancy, and is characterised by clinical euvolaemia, low plasma osmolality, and concentrated urine, with normal renal, adrenal and thyroid function. Causes of SIAD include ectopic production of vasopressin (AVP) from an underlying tumour, cancer treatments, nausea and pain. Cortisol deficiency is an important differential in the assessment of hyponatraemia, as it has an identical biochemical pattern to SIAD, and is easily treatable. This is particularly relevant with the increasing use of immune checkpoint inhibitors, which can cause hypophysitis and adrenalitis, leading to cortisol deficiency. Guidelines on the management of acute, symptomatic hyponatraemia recommend 100ml bolus of 3% saline with careful monitoring of the serum sodium to prevent overcorrection. In cases of chronic hyponatraemia, fluid restriction is recommended as first line treatment, however this is frequently not feasible in patients with cancer and has been shown to have limited efficacy. Vasopressin-2 receptor antagonists (vaptans), may be preferable, as they effectively increase sodium levels in SIAD and do not require fluid restriction. Active management of hyponatraemia is increasingly recognised as an important component of oncological management; correction of hyponatraemia is associated with shorter hospital stay and prolonged survival. The awareness of the impact of hyponatraemia, and the positive benefits of active restoration of normonatraemia, remain challenging in oncology.

Six-Lead Electrocardiography Enables Identification of Rhythm and Conduction Anomalies of Patients in the Telemedicine-Based, Hospital-at-Home Setting: A Prospective Validation Study

“…Electrolyte abnormalities are common in acute patients, especially those with many background comorbidities. For example, hyponatremia is common in cancer patients, suffering from both solid tumors and hematologic malignancies, and is associated with poor clinical outcomes [7]. Hyponatremia is also common in patients presenting COPD exacerbations, associated with worse prognosis, increased risk for readmissions, and death [8].…”

6-Lead Electrocardiography is a Viable Option for Identification of Rhythm and Conduction Anomalies of Patients in the Telemedicine-Based, Hospital-at-Home Setting. A Prospective Validation Study

“…Electrolyte abnormalities are common in acute patients, especially in those with many background comorbidities. For example, hyponatremia is common amongst cancer patients, suffering from both solid tumors and hematologic malignancies, and is associated with poor clinical outcomes [7]. Hyponatremia is also common amongst patients presenting with COPD exacerbations, associated with worse prognosis, increased risk for readmissions and death [8].…”

Potential pitfalls in diagnosis of immunotherapy-induced hypothalamic–pituitary–adrenal axis suppression

“…Cortisol deficiency also increases the expression of aquaporin-2 channels in the collecting duct of the kidneys which increases free water reabsorption. If hyponatraemia is present, it is mandatory to perform a morning cortisol as ACTH deficiency shares an identical biochemical signature to syndrome of inappropriate diuresis (SIAD), both characterised by raised urinary sodium and osmolality ( Mc Donald et al 2022 ). Differentiating between these two causes of hyponatraemia is important as ACTH deficiency is readily treatable with hydrocortisone and negates the need for arduous fluid restriction ( Garrahy & Thompson 2019 ).…”