Hyponatraemia is the most common electrolyte disturbance in the elderly. It can be asymptomatic or produce a spectrum of symptoms, particularly in the central nervous system, such as altered state of consciousness, lethargy, headache, seizures and gait disturbances, all of which are a common reason for consultation in this population. This condition has a high impact on the functionality of the patient given the need for multiple hospital stays, as well as on mortality. Its aetiology is multifactorial and its most common causes include low salt intake, chronic diseases such as kidney disease and heart failure, and the syndrome of inappropriate antidiuretic hormone secretion (SIADH), which is commonly caused by the chronic use of certain drugs, such as antidepressants, diuretics and antipsychotics, which are the most forgotten in clinical practice. The following clinical case presents the diagnostic approach of hyponatraemia and the importance of the medical history as a key tool to detect the aetiology of this clinical entity.

Severe congestive heart failure (CHF) patients are prone to hyponatremia. Peritoneal dialysis (PD) is increasingly used for long-term management of refractory CHF patients. The glucose polymer icodextrin was proposed to be a good option for fluid removal in such patients. A small, although statistically significant reduction in serum sodium (∼2mmol/l) consistently observed in multiple trials, is considered as not clinically relevant. Here we reported five refractory CHF patients who demonstrated sodium drop by median of 8meq/l (range 5.4-8.3meq/l) after icodextrin was added to their program. It seems that icodextrin may contribute to clinically relevant hyponatremia if the hyponatremia is compounded by other factors. Patients with extremely severe congestive heart failure are susceptible to this complication.