Hyponatremia and polypharmacy in an older outpatient
A 76-year-old man with heart failure (EF 45%), hypertension, depression, and osteoarthritis presents with 2 weeks of fatigue, confusion, and one fall. Medications: furosemide 40 mg daily, lisinopril 10 mg, sertraline 50 mg, hydrochlorothiazide 25 mg, ibuprofen 400 mg three times daily as needed, and desmopressin? no - he takes no desmopressin. Labs: sodium 124 mEq/L (was 136 two months ago), potassium 3.4, creatinine 1.3 (baseline 1.0), glucose 110, TSH normal. He appears euvolemic. He has been drinking more water because of thirst. His wife notes he has been more forgetful and unsteady.
1. What is the likely cause of his hyponatremia, and which medications contribute?
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Likely cause: euvolemic hyponatremia, probably SIADH-like, with multiple contributors. Key clues: euvolemic exam, normal glucose and TSH, recent onset, increased water intake (polydipsia), and a medication list full of culprits.
Contributing medications:
- Hydrochlorothiazide - classic cause of hyponatremia (impaired free-water excretion, often with hypokalemia - his K is 3.4).
- Sertraline (SSRI) - well-known cause of SIADH/hyponatremia, especially in older adults.
- Furosemide - can contribute, though less classically than thiazides.
- Ibuprofen (NSAID) - causes sodium and water retention and worsens renal function; contributes to AKI (creatinine rose from 1.0 to 1.3) and blunts diuretic effect.
Other considerations: evaluate for adrenal insufficiency, hypothyroidism (TSH normal), and true SIADH criteria (serum osmolality low, urine osmolality high, urine sodium high, euvolemia). Consider whether heart failure is contributing (but exam is euvolemic).
Symptom relevance. Sodium 124 with confusion and a fall suggests symptomatic hyponatremia - the fall and cognitive change may be attributable.
2. How should the hyponatremia be managed, and what is the correction rate limit?
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Assess severity. He has symptoms (confusion, fall) but is not seizing or comatose. If severe neurologic symptoms (seizure, obtundation) were present, hypertonic (3%) saline boluses would be indicated. Here, manage more conservatively.
First steps:
- Stop the offending drugs: hold hydrochlorothiazide, sertraline, and ibuprofen. Correct hypokalemia (K 3.4) - potassium repletion helps raise sodium.
- Fluid restriction (e.g., ~1–1.2 L/day) is first-line for SIADH-like hyponatremia; address polydipsia.
- Monitor sodium and volume status closely; avoid rapid correction.
Correction limit. Aim to raise sodium by no more than 8–10 mEq/L in 24 hours (and ~18 mEq/L in 48 hours) to avoid osmotic demyelination, especially in a malnourished or chronic case. If correction overshoots, free water or desmopressin can be used to re-lower it under expert guidance.
Reassess. Repeat electrolytes in 24–48 hours; consider nephrology if not improving. Once stable, reintroduce only necessary medications and avoid thiazides and SSRIs if possible.
3. What changes to his medication regimen and monitoring would you make going forward?
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Deprescribe and substitute:
- Hydrochlorothiazide: stop; use an alternative antihypertensive if needed (e.g., amlodipine) with monitoring.
- Sertraline: consider switching to an agent with lower SIADH risk (e.g., mirtazapine or bupropion) or nonpharmacologic depression care, with monitoring.
- Ibuprofen: stop; use acetaminophen and topical agents for osteoarthritis; avoid NSAIDs in heart failure and CKD.
- Furosemide and lisinopril: reassess doses given AKI; monitor renal function and potassium.
Monitoring: electrolytes and renal function after changes; watch for recurrent hyponatremia; educate him and his wife about symptoms (confusion, falls, nausea) and fluid intake.
Fall and cognition: recheck cognition after sodium correction; involve PT for gait and balance; review home safety. Document a medication reconciliation and rationale.