Introduction

Case Presentation

  • MJ is a 56-year-old female who presents to the ED with a chief complaint of progressively worsening weakness and fatigue over the past week, associated with a loss of appetite, nausea, and occasional confusion.
    • MJ denies shortness of breath, chest or abdominal pain, cough, pain or swelling in her legs, other neurological symptoms, fever, vomiting, or diarrhea.
    • Her medical history is significant for hypothyroidism, hypercholesterolemia, and hypertension.
    • According to family, she was hospitalized for three days a few months ago due to “dehydration,” at which time she was given “fluids.”
    • While transporting MJ to the CT scanner, she has a witnessed prolonged tonic-clonic seizure.
    • POC labs are unremarkable, except a serum sodium of 118 mEq/L.
  • How would you manage this patient?
    • 3% Sodium Chloride STAT!

Clinical Detail

Pharmacology — 3% Sodium Chloride (NaCl)

ParameterDetail
Dose*
  • 2 mL/kg or 50–150 mL
    • Maximum of 3 boluses of 3% NaCl, preferably 10–30 minutes apart
  • Option to dose based on the calculated sodium deficit
Administration*
  • IV bolus is the recommended administration for symptomatic hyponatremia
  • Administered over 10–60 minutes
  • May be given through peripheral (PIV) access while central access is obtained
Adverse Effects
  • Hypernatremia
  • Fluid or solute overload
  • Hypokalemia
  • Acidosis
  • Overcorrection of hyponatremia
Monitoring
  • BMP (Na+, K+, Cl−)
  • Symptoms of hyponatremia
  • Serum osmolality
  • Volume status
  • Neurological exam
Compatibility
  • Not compatible with blood products or with drugs that are incompatible with normal saline
Comments
  • Critical to establish IV access with the largest bore at the most proximal point
  • During emergencies, it is acceptable to administer through a peripheral IV

*Check institutional guidelines.

Keys to Managing Symptomatic Hyponatremia

ParameterDetail
Indications for emergency treatment
  • Confusion, agitation, coma, or seizures secondary to low serum sodium levels
  • Symptoms of severe hyponatremia
Goal Na+ & correction limits
  • Acute target: 4–6 mEq/L rise in the first 1–2 hours to break severe symptoms — this is enough; do not chase normonatremia
  • Ceilings: ≤8 mEq/L/24h and ≤16 mEq/L/48h in high-risk (Na ≤105, alcohol use disorder, severe hypokalemia, malnutrition, advanced liver disease); ≤10–12 mEq/L/24h and ≤18 mEq/L/48h otherwise. The 4–6 mEq/L emergency bump counts toward the 24h limit
  • Aim ~120 mEq/L initially, then slower to ~130 mEq/L over 24–48 h; keep the initial goal lower if baseline Na < 100 mEq/L
Preventing overcorrection (ODS)
  • Limits apply to chronic (≥48h)/unknown-duration hyponatremia; high-risk features (Na ≤105, alcohol use disorder, severe hypokalemia, malnutrition, advanced liver disease) trigger the tighter ≤8/24h ceiling
  • Anticipate auto-correction when the ADH stimulus resolves (volume repletion, thiazide stopped, adrenal insufficiency treated, desmopressin withdrawal/beer potomania) — watch urine output (brisk dilute aquaresis warns of overshoot); recheck Na q2h
  • Proactive DDAVP clamp: give or continue desmopressin 1–2 mcg IV/SC q6–8h; do NOT abruptly stop desmopressin in desmopressin-induced hyponatremia
  • If the limit is exceeded: re-lower with D5W ~3 mL/kg/h plus desmopressin 2–4 mcg IV, titrated to just below the limit
  • Watch potassium: K repletion itself raises serum Na — count it in the correction trajectory

Evidence

Overview of Evidence

Author, yearDesign, sample sizeIntervention & comparisonOutcome
Ayus, 2025Systematic review / meta-analysis
16 cohorts, N = 11,811		Rapid vs slow vs very-slow correction of severe hyponatremia
  • Slow & very-slow correction associated with higher mortality (in-hospital OR 0.67 and 0.29 favoring rapid)
  • Rapid correction not associated with increased ODS
Baek, 2021 (SALSA)RCT
N = 178		Rapid intermittent bolus (RIB) vs slow continuous infusion (SCI) of 3% NaCl
  • Overcorrection (>12 mEq/L/24h) 17.2% vs 24.2% (P=0.26, not significant — primary outcome)
  • Less therapeutic re-lowering with RIB (41.4% vs 57.1%; NNT 6.3)
  • RIB better at achieving target correction within 1 h
Dutta, 2025Meta-analysis
3 studies, N = 290		RIB vs SCI of 3% NaCl
  • No difference in overcorrection, re-lowering, ODS, or mortality
  • SCI marginally shorter length of stay
Adrogué, 2022JAMA narrative reviewManagement of severe symptomatic hyponatremiaRaise Na 4–6 mEq/L within 1–2 h; do not exceed ~10 mEq/L in the first 24 h; ODS risk with over-rapid correction
Spasovski, 2024Treatment standard (review)Severe symptomatic hyponatraemia100–150 mL 3% bolus; rapid intermittent administration preferred; maintain readiness for hypotonic fluids/desmopressin to manage overcorrection
Dillon, 2018Observational
N = 66		3% NaCl through PIV
  • Max rate = 50 mL/hr
  • Mean infusion duration = 14 hrs (IQR 4–30)
  • Infusion-related phlebitis = 3%
Perez, 2017Observational
N = 28		3% NaCl through PIV
  • Max rate = 50 mL/hr
  • Mean infusion duration = 36 hrs (range 1–124)
  • Infusion-related phlebitis = 3%
Jones, 2016Observational
N = 213		3% NaCl through PIV
  • Max rate = 30 mL/hr
  • Mean infusion duration = 0.85 hr (IQR 0.4–1.3)
  • Infusion-related phlebitis = 4%
Ayus, 2015Case series
N = 47		3% NaCl 500 mL over 6 hrs via PIV
  • Increase in serum sodium of 1.26 mEq/L/hr
  • Improvement in symptoms in 97% of cases
Hew-Butler, 2015Exercise-Associated Hyponatremia (EAH) consensus guidelineRecommendation for severe EAH“100 mL bolus of 3% NaCl, repeated twice if there is no clinical improvement (10 min intervals have been recommended).”
Spasovski, 2014European Renal Best Practice (ERBP) hyponatraemia guidelineRecommendation for severe hyponatremia“We recommend prompt IV infusion of 150 mL 3% hypertonic saline or equivalent over 20 minutes. (1D)”
Verbalis, 2013Expert panel recommendations for hyponatremiaRecommendation for symptomatic acute hyponatremia“For severe symptoms, 100 mL of 3% NaCl infused IV over 10 minutes × 3 as needed.”

Conclusions

  • Severe symptomatic hyponatremia (confusion, agitation, coma, or seizures from a low serum sodium) is a neurologic emergency: 3% sodium chloride STAT. Do not let fear of osmotic demyelination delay treating a seizing patient. A 2025 meta-analysis of observational cohorts (n=11,811) found faster correction associated with lower mortality without a significant rise in ODS on primary analysis (Ayus 2025) — an association, not license to exceed the correction limits.
  • Use one coherent regimen: 100 mL of 3% NaCl over 10 min, up to 3 doses (or 2 mL/kg over 10 min, max 150 mL). Reassess symptoms and serum Na 10–20 min after each bolus; stop once symptoms improve or Na has risen 4–6 mEq/L (target that rise within the first 1–2 hours, faster if actively seizing). A peripheral IV is fine in the emergency. Rapid intermittent bolus is a reasonable guideline-preferred default (SALSA) but is not proven safer than a continuous infusion (Dutta 2025); frequent Na checks matter more than the delivery mode.
  • Correction limits (to prevent ODS) apply to chronic (≥48h) or unknown-duration hyponatremia. High-risk features — serum Na ≤105, alcohol use disorder, severe hypokalemia, malnutrition, or advanced liver disease — tighten the ceiling to ≤8 mEq/L/24h and ≤16 mEq/L/48h. Without those features: ≤10–12 mEq/L/24h and ≤18 mEq/L/48h. The 4–6 mEq/L emergency bump counts toward the 24-hour limit. Genuinely acute hyponatremia (exercise-associated, water intoxication) tolerates faster correction.
  • Anticipate overshoot when the ADH stimulus resolves: volume repletion, stopping a thiazide, treating adrenal insufficiency, or desmopressin withdrawal / beer potomania. Watch urine output (a brisk dilute aquaresis warns of overshoot) and recheck Na q2h. Proactive DDAVP clamp: give or continue desmopressin 1–2 mcg IV/SC q6–8h to hold a controlled rate — do not abruptly stop desmopressin in desmopressin-induced hyponatremia. If the limit is exceeded, re-lower with D5W ~3 mL/kg/h plus desmopressin 2–4 mcg IV, titrated to just below the limit.
  • Fixed-dose boluses over-correct low-body-weight and under-correct high-body-weight patients (Pelouto 2023) — favor weight-based dosing at the extremes and confirm by the measured serum Na, not the formula. Note that potassium repletion itself raises serum sodium, so count it in the correction trajectory and check Na more often during aggressive K replacement. Always check institutional guidelines.

References

  • Sodium chloride. Micromedex [Electronic version]. Greenwood Village, CO: Truven Health Analytics. Retrieved December 21, 2019, from http://www.micromedexsolutions.com/
  • Rogers IR, et al. Clin J Sport Med. 2011 May;21(3):200-3. PMID: 21519296
  • Dillon RC, et al. J Intensive Care Med. 2018 Jan;33(1):48-53. PMID: 28372499
  • Perez CA, et al. J Neurosci Nurs. 2017 Jun;49(3):191-195. PMID: 28471928
  • Jones GM, et al. Am J Crit Care. 2016 Dec;26(1):37-42. PMID: 27965228
  • Ayus JC, et al. Am J Kidney Dis. 2015 Mar;65(3):435-42. PMID: 25465163
  • Hew-Butler T, et al. Clin J Sport Med. 2015 Jul;25(4):303-20. PMID: 26102445
  • Spasovski G, et al. Nephrol Dial Transplant. 2014 Apr;29 Suppl 2:i1-i39. PMID: 24569496
  • Verbalis JG, et al. Am J Med. 2013 Oct;126(10 Suppl 1):S1-42. PMID: 24074529
  • Baek SH, et al. (SALSA). JAMA Intern Med. 2021;181(1):81-92. PMID: 33104189
  • Ayus JC, et al. JAMA Intern Med. 2025;185(1):38-51. PMID: 39556338
  • Dutta D, et al. Ann Afr Med. 2025;24(2):431-437. PMID: 40053429
  • Adrogué HJ, et al. JAMA. 2022;328(3):280-291. PMID: 35852524
  • Spasovski G. Nephrol Dial Transplant. 2024;39(10):1583-1592. PMID: 39009016
  • Pelouto A, et al. Eur J Endocrinol. 2023;188(3):322-330. PMID: 36881992
Tags:hyponatremia 3% Sodium Chloride sodium seizure