Key Points
- Use the highest‑yield diagnostic test early; do not let testing delay time‑critical therapy.
- Set objective targets and reassess frequently.
- Plan definitive source control or disease‑specific therapy when indicated; document follow‑up and patient education.
Algorithm
- Confirm hypotonic hyponatremia; assess severity/symptoms.
- Give 3% saline bolus(es) for seizures/coma; start DDAVP clamp to control rise.
- Define etiology via urine studies; treat underlying cause; set daily Na+ targets (≤8 mEq/L/day).
- If overcorrection → give DDAVP and D5W to relower sodium safely; ongoing neuro checks.
Clinical Synopsis & Reasoning
Manage severe or symptomatic hyponatremia with hypertonic saline boluses and a desmopressin ('DDAVP') clamp to prevent overly rapid correction. Identify etiology (hypovolemic, euvolemic/SIADH, hypervolemic) and treat the cause while monitoring sodium correction limits to prevent osmotic demyelination.
Treatment Strategy & Disposition
Stabilize ABCs. Initiate guideline‑concordant first‑line therapy with precise dosing and continuous monitoring. Escalate to advanced/procedural interventions based on explicit failure criteria. Define ICU, step‑down, and ward disposition triggers; involve specialty teams early.
Epidemiology / Risk Factors
- Risk varies by comorbidity and precipitants; see citations for condition‑specific data.
Investigations
| Test | Role / Rationale | Typical Findings | Notes |
|---|
| Serum/urine osmolality and urine sodium | Etiology | Differentiate hypovolemic, SIADH, hypervolemic | Key branch point |
| Serum sodium q2–4 h during correction | Safety | Avoid overcorrection (>8 mEq/L/24 h) | Use DDAVP clamp |
| Thyroid and adrenal testing (selected) | Secondary causes | Hypothyroidism/adrenal insufficiency | — |
High-Risk & Disposition Triggers
| Trigger | Why it matters | Action |
|---|
| Seizures/coma or impending herniation | Brain injury risk | 3% saline bolus; ICU; DDAVP clamp |
| Na+ rise >8–10 in 24 h | ODS risk | DDAVP + D5W relowering |
| Adrenal/thyroid failure | Reversible cause | Steroids/thyroid replacement |
Pharmacology
| Medication/Intervention | Mechanism | Onset | Role in Therapy | Limitations |
|---|
| Hypertonic saline 3% 100 mL IV bolus (repeat up to 3) | Tonicity therapy | Minutes | Raise Na+ by 4–6 mEq/L in severe symptoms | Follow with controlled infusion |
| Desmopressin 1–2 µg IV/SC q6–8 h (clamp) | AVP analog | Hours | Prevents rapid aquaresis and overcorrection | Pair with 3% to steer rate |
| Loop diuretics with saline (hypervolemic) or salt tabs/urea (SIADH) | Adjuncts | Hours‑days | Tailor to phenotype | Fluid restriction as baseline |
Prognosis / Complications
- Outcome depends on timeliness of diagnosis and definitive therapy; monitor for complications.
Patient Education / Counseling
- Provide red‑flag education, adherence guidance, and explicit return precautions; arrange timely specialty follow‑up.
References
- European/American hyponatremia guidelines — Link