Bedside Snapshot
- Use It For
- Severe symptomatic hyponatremia (seizure, coma, obtundation); moderately severe symptomatic hyponatremia; symptomatic exercise-associated hyponatremia; raised ICP or herniation signs in TBI, ICH or cerebral edema
- Adult Dose
- Severe hyponatremia: 100–150 mL IV bolus over 10–20 min, up to 3 boluses total until Na⁺ is up 4–6 mEq/L
- ICP/herniation: 3% 250 mL IV bolus, or 23.4% 30 mL via central line only
- Pediatric Dose
- Hyponatremia: not established in children; specialist use only, no dose shown. Raised ICP (severe TBI): 2–5 mL/kg IV over 10–20 min; refractory: 23.4% 0.5 mL/kg central line (max 30 mL)
- Onset / Duration
- IV: immediate osmotic effect / duration varies with dose, renal water handling and the underlying cause
- Do Not Give / Hold If
- Stop boluses once symptoms resolve or Na⁺ is up 4–6 mEq/L; stop if the rise nears 10 mEq/L in the first 24 hr or 8 in any later 24 hr (8 in any 24 hr if high ODS risk); ICP: reassess if Na⁺ >155–160 or Cl⁻ >110–115 mEq/L
- Watch For
- Overcorrection (Na⁺ after each bolus, surge in dilute urine); osmotic demyelination days later (dysarthria, dysphagia, weakness); pulmonary edema (crackles, SpO₂); IV-site infiltration
- Reversal / Rescue
- No antidote. Overcorrection: stop 3%, give D5W 10 mL/kg IV over 1 hr plus desmopressin 2 mcg IV (not more often than every 8 hr) with expert input
- Must Remember
- Bolus to stop symptoms, not to normalize Na⁺. Program the volume on a pump: one 500 mL bag holds 256.5 mEq Na⁺. 23.4% (4 mEq/mL) goes through a central line only.
Indications
Emergency & Prehospital
- Severe symptomatic hyponatremia: seizures, coma, deep somnolence, vomiting or cardiorespiratory distress from hypotonic hyponatremia. Treat it now. Acute or chronic makes no difference.
- Symptomatic exercise-associated hyponatremia (EAH): confusion, seizure or coma during or up to 24 hr after prolonged exertion (endurance events, hiking, military training), with a normal or minimally raised core temperature. The Wilderness Medical Society (WMS) guideline supports hypertonic saline boluses in the field, even with no point-of-care Na⁺ test. Event medicine or agency protocol decides who may give it.
- Clinical signs of brain herniation: unilateral fixed dilated pupil, posturing or Cushing response with a suspected mass lesion. This is not guideline-endorsed as a field indication. The Brain Trauma Foundation (BTF) 2023 prehospital TBI guideline advises against prehospital hyperosmolar therapy (mannitol or hypertonic saline) as prophylaxis for suspected raised ICP, with or without herniation signs, at this time (weak recommendation). Any field or CCT use follows local protocol and medical direction (off-label).
ED / ICU / Transport
- Moderately severe symptomatic hyponatremia: confusion, nausea without vomiting or headache. Give one bolus while you work up the cause.
- Elevated intracranial pressure (ICP) or cerebral edema in traumatic brain injury (TBI): for initial osmotherapy, the Neurocritical Care Society (NCS) 2020 guideline suggests hypertonic sodium over mannitol (off-label).
- Elevated ICP in intracerebral hemorrhage (ICH): NCS 2020 suggests hypertonic sodium over mannitol. Either a symptom-based bolus or a sodium target is acceptable (off-label).
- Elevated ICP or cerebral edema in subarachnoid hemorrhage (SAH): NCS 2020 suggests symptom-based boluses over dosing to a sodium target (off-label).
- Elevated ICP in acute ischemic stroke or hepatic encephalopathy: NCS 2020 has no preference between hypertonic sodium and mannitol. In stroke, consider hypertonic sodium if mannitol fails (off-label).
- Pediatric severe TBI with intracranial hypertension: bolus and continuous infusion both follow the Brain Trauma Foundation (BTF) pediatric guideline (off-label).
Other Uses
- FDA-labeled use: "source of water and electrolytes." The hyponatremia regimens and every ICP use come from guidelines and practice. The label doesn't cover them.
- Not indicated: mild or asymptomatic chronic hyponatremia (treat the cause), or hypovolemic hyponatremia without severe symptoms (restore volume with isotonic crystalloid). It's not indicated to normalize Na⁺.
Composition
| Component | Per Liter | Comparison to Plasma |
|---|---|---|
| Sodium chloride | 30 g/L (3 g per 100 mL) | — |
| Na⁺ | 513 mEq/L (256.5 mEq per 500 mL bag; 51.3 mEq per 100 mL) | About 3.6 times plasma (135–145 mEq/L) |
| Cl⁻ | 513 mEq/L | About 5 times plasma (96–106 mEq/L) |
| K⁺, Ca²⁺, Mg²⁺, buffer, glucose | None | — |
| Osmolarity | 1,027 mOsm/L (calculated) | About 3.5 times plasma (about 280–310 mOsm/L per label) |
| pH | 5.0 (range 4.5–7.0) | Plasma 7.35–7.45 |
| Tonicity | Hypertonic | — |
- No free water: Water leaves the cells and enters the extracellular fluid. Plasma volume grows by more than the volume infused. That shrinks swollen brain cells and supports blood pressure.
- Chloride load: Repeated doses cause hyperchloremic metabolic acidosis. Track Cl⁻ and bicarbonate.
- 23.4% concentrate: 4 mEq/mL (8,008 mOsm/L). A 30 mL dose holds 120 mEq Na⁺, about the sodium in 234 mL of 3%.
- Products: The values are for US 3% Sodium Chloride Injection, USP in 500 mL bags. Products in other countries may differ.
Expected Na⁺ change from 1 L of 3% saline (Adrogué–Madias)
ΔNa⁺ = (513 − serum Na⁺) ÷ (total body water + 1)
Total body water runs about 0.6 × weight in kg in children and younger men, 0.5 in younger women and older men, and 0.45 in older women. Worked example: a 70 kg man with Na⁺ 115 mEq/L. (513 − 115) ÷ 43 ≈ 9.3 mEq/L per liter, so 100 mL raises Na⁺ by about 0.9 mEq/L. Once a water diuresis starts, the formula underestimates the rise. Measure Na⁺. Don't bank on the estimate.
Dosing & Administration
Available Forms
- 3% Sodium Chloride Injection, USP: 30 mg/mL (513 mEq/L Na⁺) in 500 mL single-dose bags, 256.5 mEq Na⁺ per bag. EDs, ICUs and critical-care transport carry this form.
- 5% Sodium Chloride Injection, USP: 50 mg/mL (856 mEq/L Na⁺) in 500 mL bags. Rarely used. Never swap it in for 3% without recalculating the dose.
- 23.4% Sodium Chloride Injection, USP (concentrate): 234 mg/mL (4 mEq/mL). The label lists it as an additive that must be diluted. Undiluted ICP boluses are off-label. Central line only, under ICU or neurocritical care protocols.
High-Alert Medication: ISMP lists hypertonic sodium chloride (greater than 0.9%) as high-alert. Three ways this goes wrong. A 500 mL bag runs free-flow or gets programmed at a maintenance rate. 3%, 5% or 23.4% gets picked in place of 0.9%. 23.4% goes through a peripheral line. Program the bolus volume on a pump. Then get an independent double-check of concentration, volume and line.
Adult Dosing
| Indication | Dose & Route | Repeat / Max | Notes |
|---|---|---|---|
| Severe symptomatic hyponatremia | 3% 100–150 mL IV bolus over 10–20 min (European guideline, Spasovski 2014: 150 mL over 20 min; 100 mL over 10 min per Adrogué 2022). Consider 2 mL/kg in low or unusual body weight. | Check Na⁺ after each bolus; repeat up to 3 boluses total until symptoms improve or Na⁺ is up 4–6 mEq/L. Max rise 10 mEq/L in the first 24 hr, then 8 mEq/L per 24 hr (8 mEq/L in any 24 hr if high ODS risk). | High-alert. Give regardless of chronicity. Stop boluses at the target, then treat the cause. Severe symptoms persist after a 5 mEq/L rise: look for another cause; with expert input, continue 3% aiming for about 1 mEq/L/hr until symptoms improve, the total rise reaches 10 mEq/L or Na⁺ reaches 130 mEq/L. |
| Symptomatic exercise-associated hyponatremia (field) | 3% 100 mL IV bolus (WMS guideline); give without waiting for a Na⁺ value when point-of-care testing is not available | Repeat every 10 min if no improvement, up to 3 boluses total; further doses per medical direction. Same 24-hr limits once Na⁺ is measured. | High-alert. Peripheral IV. Check core (rectal) temperature first to exclude exertional heat stroke. No isotonic or hypotonic IV fluid boluses. |
| Moderately severe symptomatic hyponatremia | 3% 150 mL IV over 20 min, once (European guideline) | Single bolus; aim for about 5 mEq/L rise in 24 hr. Max rise 10 mEq/L in the first 24 hr, then 8 mEq/L per 24 hr (8 mEq/L in any 24 hr if high ODS risk). | High-alert. Check Na⁺ at 1, 6 and 12 hr; start cause-specific treatment. |
| Elevated ICP or herniation signs | 3% 250 mL IV bolus (250–500 mL in published practice). No guideline sets the infusion time: program both volume and time on a pump per protocol; never free-flow | Repeat by ICP and neuro exam. Na⁺ >155–160 or Cl⁻ >110–115 mEq/L (NCS levels for AKI risk): reassess before more | High-alert. Off-label. Peripheral line in a large vein is acceptable for 3%. Check Na⁺ every 4–6 hr. |
| Refractory ICP or herniation (ICU) | 23.4% 30 mL IV via central line only; rate per protocol | 30–60 mL doses studied; repeat per neurocritical care protocol; same Na⁺ and Cl⁻ reassessment levels | High-alert. Off-label use of a concentrate. Can cause transient hypotension. |
Pediatric Dosing
| Indication | Dose (per kg) & Route | Max Single / Max Total | Notes |
|---|---|---|---|
| Symptomatic hyponatremia (seizure, encephalopathy) | Not established in children; specialist use only (no dose shown) | No pediatric maximum established | High-alert. No dose in AHA/AAP 2025, NASEMSO v3.0 or the US label. Specialist use only; do not dose from hospital pathways alone. |
| Intracranial hypertension (severe TBI) | 3% 2–5 mL/kg IV over 10–20 min | Repeat by ICP; avoid sustained Na⁺ >160 mEq/L (DVT) and Na⁺ >170 mEq/L for more than 72 hr (thrombocytopenia, anemia) | High-alert. Off-label. BTF 2019 pediatric guideline, Level II: "Recommended effective doses for acute use range between 2 and 5 mL/kg over 10–20 minutes." |
| Refractory intracranial hypertension | 23.4% 0.5 mL/kg IV via central line only | Max 30 mL/dose | High-alert. Off-label. BTF 2019 pediatric guideline, Level III: "The suggested dose is 0.5 mL/kg with a maximum of 30 mL." PICU use. |
Pediatric sources: Pediatric doses follow AHA/AAP 2025 wherever it states a dose. If it doesn't, they follow the NASEMSO National Model EMS Clinical Guidelines v3.0 (2022). The US label comes last. When none of them gives a dose, no dose is shown. A pediatric maximum never exceeds the adult maximum dose (NASEMSO Universal Care Guideline, p. 13). Doses are off-label unless marked labeled.
Neonates and weight: Neonatal dosing isn't established on this page. Follow NICU protocols. Use actual body weight for mL/kg doses. See weight-based dosing.
Continuous Infusion
| Setting | Example Concentration | Start | Titrate | Usual Range / Max |
|---|---|---|---|---|
| Adult hyponatremia, non-emergent (specialist) | 3% (513 mEq/L) | Rate calculated by nephrology or ICU from the Adrogué–Madias formula; no standard mL/kg/hr range | To a 4–6 mEq/L rise per day; Na⁺ every 2–4 hr while 3% is infusing (more often if high ODS risk or urine output rises) | Example: 70 kg man, Na⁺ 115: about 27 mL/hr (0.4 mL/kg/hr) gives about 6 mEq/L/day before any water diuresis. Max 10 mEq/L in the first 24 hr, then 8 per 24 hr (8 in any 24 hr if high ODS risk) |
| Adult neurocritical care (sodium target) | 3% (513 mEq/L) | Per protocol | Na⁺ every 4–6 hr to the team target (studies used 145–155 mEq/L). Not favored in SAH: NCS suggests symptom-based boluses | Reassess at Na⁺ 155–160 mEq/L or Cl⁻ 110–115 mEq/L (NCS levels for AKI risk) |
| Pediatric severe TBI | 3% (513 mEq/L) | Low end of range | Sliding scale to the lowest dose keeping ICP <20 mmHg | 0.1–1 mL/kg/hr; avoid sustained Na⁺ >160 mEq/L |
Preparation & Administration
- Dilution: None for 3%. Give it as supplied. Don't add drugs to the bag, since additives may be incompatible.
- Bolus delivery: Program the bolus volume (for example, 100 mL or 150 mL) on an infusion pump. Never hang the 500 mL bag free-flow. For symptomatic hyponatremia, guidelines use repeated boluses, not a slow drip.
- Line: 3% can run through a well-working peripheral IV in a large vein. The 3% and 5% label warns of venous damage, so give it through a large vein. Check the site often. Concentrations above 3% generally go central, per institutional policy. 23.4% goes only through a central venous catheter. That's protocol practice. The label warns of severe local tissue necrosis if it's given extravascularly.
- Do not delay: For a seizing or herniating patient, start 3% peripherally. Don't wait for central access.
- Blood products: Don't run it through the same administration set as whole blood or cellular blood components.
- Pump requirement: Always use a pump for boluses and infusions. A dedicated line or lumen is preferred.
Contraindications & Precautions
Contraindications
- 3% saline: The US label lists none. None is absolute in hyponatremic seizure or herniation.
- Hypernatremia or hyperosmolar state (relative): Not indicated. It pushes Na⁺ even higher.
- 23.4% concentrate: The label contraindicates it in hypernatremia and fluid retention. It warns of severe local tissue necrosis if given extravascularly. Central line only is protocol practice.
Precautions
- High risk of osmotic demyelination syndrome (ODS): Na⁺ ≤105 mEq/L, alcohol use disorder, malnutrition, hypokalemia or liver disease. Set the ceiling at 8 mEq/L in any 24 hr.
- After the first 24 hr (standard risk): Keep the rise to 8 mEq/L per 24 hr or less until Na⁺ reaches 130 mEq/L (European guideline).
- Reversible causes: Once you remove the cause (volume restored, offending drug stopped), a water diuresis can push Na⁺ up fast. That can happen even after the 3% is stopped.
- Heart failure, cirrhosis, kidney disease, edema states, preeclampsia: Sodium retention and pulmonary edema (label).
- Low body weight: Fixed 100–150 mL boluses overcorrect more easily. Use weight-based dosing.
Hold / Reassess If
- Hyponatremia target reached: Symptoms resolved, or Na⁺ is up 4–6 mEq/L. Stop boluses. Severe symptoms still there after a 5 mEq/L rise? Look for another cause. With expert input, continue 3% aiming for about 1 mEq/L/hr. Stop once symptoms improve, the total rise reaches 10 mEq/L, or Na⁺ reaches 130 mEq/L.
- 24-hr rise near the limit: Approaching 10 mEq/L in the first 24 hr, or 8 mEq/L in a later 24 hr (8 mEq/L in any 24 hr if high ODS risk). Stop the 3% and call the prescriber. Over the limit? Relower (see Adverse Effects).
- ICP therapy: NCS suggests keeping Na⁺ at or below 155–160 mEq/L and Cl⁻ at or below 110–115 mEq/L to lower AKI risk. Above these levels, reassess before giving more hypertonic sodium. Herniation rescue runs per neurocritical care.
- Volume overload: new crackles, falling SpO₂ or rising oxygen need.
- IV site: pain, swelling or blanching: stop and resite.
Confirm true hypotonic hyponatremia: Check glucose. When it's available, check serum osmolality (<275 mOsm/kg). Hyperglycemia lowers measured Na⁺ without making the blood hypotonic. 3% saline won't help it.
Adverse Effects & Toxicity
Common
- Infusion-site reactions: pain, phlebitis, thrombosis, erythema. Peripheral lines cause more of them.
- Hyperchloremia and hyperchloremic metabolic acidosis with repeated doses
- Increased urine output (the solution can induce diuresis)
- Hypokalemia with large sodium chloride loads
- Transient hypotension during 23.4% boluses
- Hypersensitivity or infusion reactions (rare): fever, chills, urticaria, hypotension
Serious / Life-Threatening
| Effect | Recognition | Management |
|---|---|---|
| Overcorrection and osmotic demyelination syndrome | Na⁺ rise above the 24-hr limit; days later dysarthria, dysphagia, behavior change, quadriparesis, locked-in state | Prevent with limits and frequent Na⁺; if exceeded, relower promptly (below); neurology consult |
| Hypernatremia and hyperosmolality | Na⁺ above target; lethargy, seizures, coma | Stop infusion; electrolyte-free water per protocol; serial Na⁺ |
| Volume overload, pulmonary edema | Crackles, hypoxia, rising work of breathing, edema | Stop; oxygen and ventilatory support; loop diuretic such as furosemide per prescriber |
| Hyperchloremia and acute kidney injury | Cl⁻ >110–115 mEq/L, falling bicarbonate, rising creatinine | Reassess the need for more hypertonic sodium; review the chloride load with the team |
| Extravasation | Swelling, pain, blanching at the site; necrosis with 23.4% | Stop, remove the catheter, elevate, restart at another site; escalate for tissue injury |
Overdose & Toxicity Management
- Signs: hypernatremia (seizures, coma, cerebral injury) and sodium overload (peripheral and pulmonary edema).
- Immediate: stop the infusion. Check Na⁺, Cl⁻, bicarbonate, osmolality and volume status.
- Overcorrected hyponatremia (rise >10 mEq/L in the first 24 hr or >8 mEq/L in any later 24 hr, or >8 mEq/L in any 24 hr if high ODS risk): stop 3%. With expert input, give D5W 10 mL/kg IV over 1 hr under strict urine-output and fluid-balance monitoring, plus desmopressin 2 mcg IV (not repeated more often than every 8 hr).
- Antidote: none.
Monitoring
| Parameter | When / How Often | Target / Act If |
|---|---|---|
| Clinical: neuro status (GCS, pupils, seizure activity) | Continuous during boluses; after each bolus | Symptoms resolved: stop boluses. New dysarthria, dysphagia or weakness days after correction: suspect ODS |
| Clinical: urine output | Hourly during treatment; urine osmolality and Na⁺ when available | Sudden large volume of dilute urine (urine osmolality <100 mOsm/kg): water diuresis; recheck Na⁺ now; desmopressin per prescriber |
| Clinical: lung sounds, SpO₂, blood pressure | Before and after each bolus; regularly during infusions | Crackles or falling SpO₂: stop and reassess volume; hypotension after 23.4%: slow or pause, support BP |
| Laboratory: Na⁺ (hyponatremia) | After each bolus (20 min after a 150 mL bolus); every 2–4 hr while 3% is infusing; otherwise at least at 6 and 12 hr, then daily | Up 4–6 mEq/L: stop boluses. Nearing 10 mEq/L in the first 24 hr, or 8 in a later 24 hr until Na⁺ 130 (8 in any 24 hr if high ODS risk): stop and call. Over the limit: relower |
| Laboratory: Na⁺ (ICP therapy) | Every 4–6 hr | Na⁺ >155–160 mEq/L: reassess before more hypertonic sodium (NCS level for AKI risk) |
| Laboratory: Cl⁻ and bicarbonate | With each Na⁺ check on repeated dosing | Cl⁻ >110–115 mEq/L or falling bicarbonate: reassess the chloride load |
| Laboratory: K⁺ | Baseline and with Na⁺ checks | Replace hypokalemia; IV potassium also raises Na⁺, so count it toward the 24-hr rise |
| Laboratory: glucose and serum osmolality | Baseline, before treating hyponatremia | Osmolality ≥275 mOsm/kg or marked hyperglycemia: not hypotonic hyponatremia; reconsider 3% |
| Laboratory: creatinine | Daily during repeated dosing | Rising creatinine: review Na⁺ and Cl⁻ ceilings and fluid balance |
| Infusion safety: IV site and pump | Frequently during the infusion | Infiltration: stop and resite. Confirm bag concentration and programmed volume at every handoff |
Interactions & Compatibility
Clinically Significant Interactions
| Drug / Class | Effect | What To Do |
|---|---|---|
| Desmopressin | Stops water excretion; used on purpose with 3% (proactive "clamp") or after overcorrection. Stopping it releases a water diuresis | Use only with a clear plan and frequent Na⁺ checks; restrict free water while it acts |
| Vasopressin-receptor antagonists (tolvaptan, conivaptan) | Additive rapid Na⁺ rise; overcorrection | Avoid together: the tolvaptan label does not recommend co-use with hypertonic saline; use the same caution with conivaptan |
| Thiazide diuretics, antidepressants and other drugs that cause hyponatremia | Stopping the drug can start a water diuresis and fast autocorrection | Recheck Na⁺ often after stopping them |
| IV potassium chloride | Raises serum Na⁺ as well as K⁺ | Count potassium replacement toward the 24-hr Na⁺ limit |
| Loop diuretics (furosemide) | Lower medullary tonicity and increase electrolyte-free water excretion, adding to the Na⁺ rise; also cause potassium loss. Sometimes given with 3% to limit the volume load in edematous patients | Use per prescriber; check Na⁺ and K⁺ closely, and count any potassium replacement toward the 24-hr Na⁺ limit |
| Mannitol | Additive osmotic effect; mannitol diuresis can cause hypovolemia and hypotension | Track osmolality, Na⁺ and fluid balance when both are used |
| Corticosteroids | Sodium and fluid retention (label) | Watch for edema and pulmonary congestion |
| Lithium | Sodium loading increases renal lithium clearance; lithium levels may fall (label) | Monitor lithium levels |
IV Compatibility
- Give 3% as supplied, through a dedicated line or lumen when you can. Don't add other drugs to the bag.
- Don't run it through the same set as whole blood or cellular blood components.
- Unless the plan is to relower Na⁺, don't run hypotonic fluids (D5W, 0.45% saline) alongside it during hyponatremia correction.
- Check it against an institutional compatibility resource.
Special Populations
- Pediatrics: Use in children rests on clinical practice, not labeled trials. Children may regulate fluid and electrolytes poorly. Monitor Na⁺ closely. See the Pediatric Dosing table.
- Neonates: This page establishes no routine dose. Follow NICU protocols.
- Pregnancy: There are no adequate human studies and no animal reproduction studies. Sodium chloride is a normal body electrolyte. Untreated hyponatremic encephalopathy or herniation threatens mother and fetus, so treat the emergency. Use extra care in preeclampsia (sodium retention).
- Lactation: Whether it passes into breast milk isn't known (label). Don't withhold emergency treatment over that.
- Older Adults: Renal, cardiac and hepatic disease are more common. Low body weight raises the overcorrection risk with fixed boluses. Start at the low end and recheck Na⁺ often.
- Renal Impairment: No dose adjustment is established. Severe renal impairment favors sodium retention and volume overload (label). Monitor fluid balance and Na⁺ closely.
- Hepatic Impairment: Cirrhosis drives sodium retention and edema. Liver disease also puts patients at high risk for ODS. Cap the Na⁺ rise at 8 mEq/L in any 24 hr.
- Obesity / Dosing Weight: Fixed 100–150 mL boluses suit average adults. With an obviously unusual body composition, the European guideline advises 2 mL/kg. For pediatric mL/kg doses, use actual body weight.
- Heart Failure: Pulmonary edema is a high risk. Give the smallest effective dose. Reassess the lungs after each bolus.
Field & Transport Considerations
- Scope: RN and critical-care transport (flight and ground CCT) give or continue 3%. Paramedic-level IV fluid scope allows it only where the agency stocks it and the medical director approves. Ground ALS rarely carries it. Field use for brain herniation is not guideline-endorsed (see Prehospital TBI below), and it needs online medical direction. Field use for exercise-associated hyponatremia (EAH) is supported by the Wilderness Medical Society. It belongs in event-medicine or wilderness protocols with a medical director. Varies by state and agency protocol.
- Storage & Stability: Keep 3% bags at room temperature (25°C [77°F]). A brief exposure up to 40°C (104°F) does not harm the product (label). Avoid excessive heat in vehicles. Store 23.4% vials at 20–25°C (68–77°F).
- Carried Concentration: Store 3% bags apart from 0.9% saline. Store 23.4% vials (4 mEq/mL) apart from both. Read the percentage aloud before you spike or draw up.
- Prehospital TBI: The BTF 2023 prehospital guideline says not to give hyperosmolar therapy (mannitol and hypertonic saline) prophylactically for suspected raised ICP, with or without herniation signs, in the prehospital setting at this time (weak recommendation). Its summary frames this as discouraging prophylactic use without herniation signs. The guideline allows hypertonic fluid resuscitation when GCS is <8 and raised ICP is suspected (weak). NCS 2020 recommends against prehospital hypertonic saline to improve neurologic outcome. Any field or CCT use for herniation signs follows local protocol and medical direction.
- Exercise-associated hyponatremia (event and wilderness medicine): Altered mental status after prolonged exertion? Check core (rectal) temperature first. Above 40°C (104°F), it's exertional heat stroke until proven otherwise. Cool immediately. Normal or minimally raised temperature? Assume severe EAH. Give 3% 100 mL IV, repeated every 10 min up to 3 boluses total if there is no improvement. Use point-of-care Na⁺ if you have it, but don't wait for it. Don't give isotonic or hypotonic IV fluid boluses. They dilute Na⁺ further and can cause pulmonary edema. If both are possible, give the hypertonic saline boluses and cool. Observe for at least 1 hr after treatment. Hand off every fluid volume and type given.
- Infusions in Transport: Program the bolus volume on the pump and use a dedicated line. Check the site during the flight or drive. Verify concentration, rate and volume remaining at handoff. On long transports, use point-of-care Na⁺ testing if it's available.
- Handoff Essentials: indication; volume, concentration and time of each bolus; every Na⁺ value with its time; urine output trend; neuro exam trend; desmopressin or potassium given.
Clinical Pearls
Bolus to stop symptoms, then stop: In hyponatremia, the goal is a 4–6 mEq/L rise. It isn't a normal Na⁺. Overcorrection can still follow the boluses. A water diuresis can cause it, and so can a 3% drip left running.
Fix the seizure with sodium: A 4–6 mEq/L rise usually stops a hyponatremic seizure. Give 3% early while you manage the airway. Don't rely on escalating anticonvulsants alone.
Watch the urine: A sudden surge of dilute urine after volume repletion, or after stopping a thiazide, means the kidneys have started dumping water. Recheck Na⁺ now. Desmopressin may be needed to hold the rise.
Exam discriminator: 3% vs 23.4% vs mannitol:
- 3%: a bolus you can run peripherally. It expands volume.
- 23.4%: 30 mL holds 120 mEq Na⁺, about the sodium in 234 mL of 3%. Central line only.
- Mannitol: an osmotic diuretic. In a hypovolemic trauma patient, it can drop BP.
- None of these has been shown to improve neurologic outcome in TBI. They buy time until definitive care.
Sodium rise predicts reversal: In the 23.4% herniation studies, a rise of 5 mEq/L or more at 1 hr predicted reversal. Draw a Na⁺ after the dose. That's how you judge the response.
Know the high-risk patient: Na⁺ ≤105 mEq/L, alcohol use disorder, malnutrition, hypokalemia or liver disease. For these patients, use the 8 mEq/L ceiling for every 24 hr. Set the ceiling, and the plan to reach it, before the first bolus.
Pharmacology
Mechanism of Action
- Raises plasma tonicity, so water moves out of brain cells into the vascular space. Result: less cerebral edema and lower ICP.
- Corrects hypotonicity in hyponatremia, which reverses hyponatremic brain swelling (encephalopathy, seizures).
- Draws intracellular water into the plasma. Intravascular volume expands, which supports blood pressure and cerebral perfusion pressure.
- A large chloride load lowers the strong-ion difference. With repeated doses, that means hyperchloremic metabolic acidosis.
Pharmacokinetics
| Route | Onset | Peak | Duration |
|---|---|---|---|
| IV | Immediate (osmotic shift within minutes) | Serum Na⁺ highest at the end of the bolus | Variable: depends on dose, renal sodium and water handling and the underlying cause |
- Half-life: None in the drug sense. Na⁺ and Cl⁻ join the extracellular pool.
- Metabolism: none.
- Elimination: Renal. Aldosterone and antidiuretic hormone control it. The kidneys can excrete the sodium in concentrated urine, and that changes the net Na⁺ rise.
Names & Classification
- Generic Name
- Sodium chloride injection, USP, 3% (hypertonic saline)
- Brand Names
- None; generic products from several US manufacturers. Related concentrations: 5% and 23.4% sodium chloride
- Pharmacologic Class
- Hypertonic crystalloid
- Therapeutic Class
- Osmotic agent; electrolyte replenisher
- Controlled Substance
- Not controlled
- ISMP High-Alert
- Yes: ISMP high-alert medication (sodium chloride for injection, hypertonic, greater than 0.9%)
- Look-Alike / Sound-Alike
- 3% / 5% / 23.4% sodium chloride / 0.9% sodium chloride (similar bags, vials and labels)
References
- Baxter Healthcare Corporation. (2026). 3% and 5% Sodium Chloride Injection, USP in Viaflex plastic container [prescribing information] (label revised May 2018; DailyMed version March 2026). DailyMed, U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=181705c7-40e4-4d7d-b9ea-ada99380e7a9
- Spasovski, G., Vanholder, R., Allolio, B., et al. (2014). Clinical practice guideline on diagnosis and treatment of hyponatraemia (current European guideline). European Journal of Endocrinology, 170(3), G1–G47. https://doi.org/10.1530/EJE-13-1020
- Adrogué, H. J., Tucker, B. M., & Madias, N. E. (2022). Diagnosis and management of hyponatremia: a review. JAMA, 328(3), 280–291. https://doi.org/10.1001/jama.2022.11176
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