Severe hyponatremia in older patients at admission in an internal medicine department

• 72.26% of the patients admitted to Hospital were 65 years old or higher.
• Hyponatremia incidence was 27.55% at admission.
• The incidence of severe hyponatremia was 5.94%.
• Hyponatremia was associated with a higher mortality.
• HCTZ, ARBs, PPIs and spironolactone were the most relevant risk factors.

Hyponatremia is common in older people, most often of multifactorial origin, and can be associated with poor clinical outcomes. The aim was to analyze the frequency of severe hyponatremia (sodium concentration below 125 mmol/L), risk factors and mortality association in hospitalized older patients. A retrospective study was performed in older patients (over 65 years) with hyponatremia, diagnosed at admission in an Internal Medicine Department during one year. A control group of 127 older patients without hyponatremia was considered. Statistical analysis of the data gathered was made with SPSS Statistics 20. The main results were: a group of 1060 patients with age superior to 65 years was identified (representing 72.26% of total admissions); incidence of hyponatremia in those patients was 27.55% and severe hyponatremia was 5.94%; diagnosis of hyponatremia was mentioned in the discharge note in 66.67% of cases; mortality was 27.0%, against 16.0% in the control group (p = 0.057, Odds Ratio (OR) = 1.940); drugs were a significant risk factor (p < 0.001), specially thiazide diuretics (p = 0.029, OR = 2.774), angiotensin receptor blockers (ARB) (p = 0.001, OR = 4.097), proton-pump inhibitors (PPI) (p = 0.007, OR = 2.561) and spironolactone (p = 0.011, OR = 4.473); other relevant risk factors were: increased water intake (p = 0.004), tube feeding (p < 0.001), vomiting (p = 0.032, OR = 2.492), cirrhosis (p = 0.008, OR = 10.862) and hyperhidrosis (p = 0.017, OR = 2.542). We conclude that, although this group of patients had a high mortality, hyponatremia is often not investigated and not always mentioned as a diagnosis. Clinicians should have a clear appreciation of the roles that iatrogenic interventions and lapses in nutrition frequently play in upsetting the homeostatic balance in older patients.