Sammanfattning
Introduction: Hyponatremia is a common electrolytic disturbance. Although a great deal of theoretical knowledge of its causes and treatment exists, in daily clinical practice it is often difficult to decide on cause and treatment. Materials and methods: In a four-month period all acutely admitted medical patients at the Geriatric Clinic, H:S Frederiksberg Hospital, with a plasma sodium level < 130 mmol/L were examined thoroughly to determine its cause. Afterwards every case was discussed in a project group consisting of a geriatrician, a nephrologist and an endocrinologist, and a consensus was reached on the probable cause of the hyponatremia. Results: 7.4% of the acutely admitted medical patients had a plasma sodium level < 130 mmol/L. The major causes were: Syndrome of inappropriate antidiuretic hormone (SIADH) 22%, edema (due to cardiac, hepatic or renal disease) 23%, treatment with thiazide 20%, dehydration 17% and treatment with loop diuretics 8%. The age-related incidence rose until the age of 70 years and thereafter fell. Almost half the patients (49%) had previously been admitted with hyponatremia. Discussion: The frequency of hyponatremia and the distribution of its causes in this study were similar to what has been shown by other studies. The falling frequency with higher age have not previously been shown. One possible explanation is selection: hyponatremia is, in many diseases, a serious symptom associated with high mortality. Only 17% of the patients were dehydrated, indicating that treatment with sodium infusion or tablets is seldom indicated.