Overview of hyponatremia in elderly.....

discussed cause , diagnosis and management

1. Overview of hyponatremia By Irfat Mahjabeen

2. Introduction: Serum sodium <136 mmol /L ( normal 136- 146 mmol / L ) Most common electrolyte abnormality seen in elderly or in nursing home patients Affects 15% to 30% of hospital inpatients Age is a strong independent risk factor, and symptoms of hyponatremia are often masked in frailty. Poor prognosis and increased mortality risk in elderly when associated with other comorbidities.

3. Classification:

4. Hypotonic hyponatremia : according to volume status : TBW ↑↑ Na ↑ TBW ↓ Na ↓↓ TBW ↑ Na ↔

5. Physiology : Hyponatremia does not always necessarily imply Na+ depletion Plasma Na+ concentration depends on  amount of extracellular water volume relative to sodium . Plasma sodium conc is maintained by: RAA system  Thirst ADH secretion

6. Causes : Hypervolemia Euvolemia Hypovolemia Heart failure Liver failure Nephrotic syndrome hypoalbuminaemia SIADH Hypothyroidism Primary Polydipsia GI or extra-renal fluid losses Diuretics Primary hypoaldosteronism Cerebral salt wasting syndrome In elderly patients, multiple factors are usually implicated in the development of hyponatremia. the aging-related impaired water-excretory capacity frequent exposure to medications and diseases associated with hyponatremia.

7. History :

8. Clinical features : Postural hypotension, gait abnormality, recurrent fall

9. Medication : Antihypertensive : ACEI, amlodipine, thiazide*, indapamide Anticancer drug : Cisplatin, vincristine Antiarrythmic : amiodarone Anti reflux : PPI Antibiotic : Trimethoprim, ciprofloxacin Antidepressant * : TCA, lithium, SSRI, MAOI, Phenothiazine Antipsychotics *: Phenothiazine Antiepileptics : Carbamazepine, valproate

10. Investigation : serum osmolality urine sodium concentration urine osmolality Others : Serum electrolytes, urea, creatinine, and glucose Urinary protein analysis and 24 hr urinary protein for NS, Liver function tests, clotting functions and albumin in cirrhosis BNP, echocardiography if there are features of congestive cardiac failure TSH, serum cortisol level MRI brain serum lipids and serum protein electrophoresis

11. Hyponatraemia Assess serum osmolarity > 100 mosm /L Isotonic 275 to 295 mosm /L Hyperlipidemia Hyperproteinemia Hypotonic <275 mosm /L Hypertonic >295 mosm /L Hyperglycemia, mannitol, IV contrast <100 mosm /L Primary polydipsia Low solute intake Assess Urinary Na osmolality Diagnostic approach :

12. Assess urinary Na and volume status Diuretics or kidney disease Urinary Na < 30 Low effective arterial volume Urinary Na > 30 Decreased GFR/ inability to dilute urine Urinary Na osmolarity > 100 mosm/L Euvolumic SIADH 2ndary adrenal insufficiency Hypothyroidism hypovolumic D + V 3rd space fluid loss Burn Hypervolumic cirrhosis, NS, HF Hypoalbuminemia Diuretics CKD Hypovolemia Primary Adrenal insufficiency Cerebral salt wasting Yes NO

13. Management :

14. Acute hyponatremia with moderate or severe symptoms: Aim is to improve symptoms, NOT correct Na+ back to normal Critical care r/v if CNS symptoms as risk of developing brain edema Hypertonic saline 3% NaCl, 150 ml via central line over 20 minutes. Repeat VBG after 20 min - if no clinical improvement Na level remains same - Repeat bolus dose of hypertonic saline, maximum 3 time. Stop infusion : If clinical symptoms improve Serum Na concentration increased 5 mmol/L

15. Monitoring of Na level in acute hyponatremia: Na+ should not rise > 10 mmol/l in first 24 hours. Recheck Na+ level at 6, 12, 24 and 48 hours . Urine output should not be 0.5 - 1 ml/hr. Increase U/O - rapid overcorrection of Na Rapid overcorrection in chronic cases leads to a risk of osmotic demyelination syndrome. If rapid overcorrection : discontinuing the ongoing treatment. consulting an expert to consider IV dextrose or desmopressin is suggested. 1 L of 3% NaCl has 513 mEq of Na, whereas, isotonic NaCl has 154 mEq of Na

16. Acute or chronic hyponatremia with mild or no symptoms: Non-essential parenteral fluids Stop if any p rovoking medication Treatment of underlying cause.

17. Chronic hyponatremia : Assess volume status

18. Summary: Evaluation and the treatment of hyponatremia pose many challenges in the elderly population. In elderly, hyponatremia can be iatrogenic. Avoidance of polypharmacy, considering low dose of provoking medications/ alternative should be a priority in elderly people. A sudden and acute fall in serum sodium concentration can result in severe cerebral oedema, leading to cerebral herniation and death. Risk of morbidity from delaying in treatment is more than osmotic demyelination syndrome.

19. Reference : Hyponatremia in the elderly: challenges and solutions - PMC (nih.gov) Assessment of hyponatraemia - Differentials | BMJ Best Practice Clinical practice guideline on diagnosis and treatment of hyponatraemiaThe guidelines were peer reviewed by the owner societies and by external referees prior to publication. | European Journal of Endocrinology | Oxford Academic (oup.com) Hyponatraemia | Health topics A to Z | CKS | NICE Management of Hyponatraemia Clinical Guideline (cornwall.nhs.uk) http://www.gloshospitals.nhs.uk/media/documents/Hyponatraemia.pdf