Endocrine Abstracts

Introduction: Hyponatremia is the most frequent electrolyte alteration in hospitalized patients, and is associated with increased morbimortality. Hyponatremia in patients receiving parenteral nutrition (PN) is generally overlooked. Our objective was to classify the types of hyponatremia observed in patients on PN, and to describe the prescribed treatments and evolution.

Material and methods: We undertook a prospective study of all patients on medical wards receiving PN with hyponatremia – serum sodium (SNa) <135 mmol/l – attended by our team between 01/06/12 and 01/12/12. Study included physical examination, serum (S)/plasma (P) and urine(U) electrolytes and osmolality (Osm), glycemia, circulating TSH, fT₄, cortisol, ACTH, urea/creatinina, and transaminase levels.

Results: Twenty out of 85 patients (23.5%) presented hyponatremia (9 women), average age 68.5 (S.D. 13.15), SNa 130.8 mmol/l (S.D. 4.03), nadir SNa 128.95 (S.D. 3.2). 70% (14) were euvolemic, 20% (4) hypovolemic, and 10% (2) hypervolemic. SNa euvolemics: 130.5 (IR 129–133), P_osm 274 mOsm/Kg (IR 266.7–280). U_Na: 121 mmol/l (IR 82–128), U_osm: 454 mOsm/Kg (IR 366–786).

Diagnosis/treatment: euvolemics: Three cases of pain-related physiologic ADH elevation were treated with analgesics: SNa pre-treatment 132.5 (IR 131.6–137.6) and post-treatment 137.5 (IR 133–138). 10 cases presented SIADH. Of whom 8 received fluid restriction and increased sodium in PN: SNa pre-treatment 129 (IR 129–133) post-treatment 134.0 (IR 133.2–136.1), 2 required tolvaptan: SNa pre-treatment 127.83 (IR 126.6–129) post-treatment 137 (IR 136–138); In one case of thiazide-induced hyponatremia the diuretic was discontinued: SNa pre-withdrawal 133, post-withdrawal 137. Hypovolemics were treated with an increase in PN volume. SNa pre-treatment 132 (IR 124.2–133.7), post-treatment 134 (IR 132.1–136.5). HYPERVOLEMICS received furosemide and NP volume was reduced: SNa pre-treatment 130.50 (IR 130.0–131.0), post-treatment 137.5 (IR 133–142).

Conclusions: SIADH was the most frequent cause of hyponatremia in our PN-treated patients. A correct diagnosis of the cause of hyponatremia in patients receiving PN is essential for adequate treatment of this common electrolyte disorder.