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Bedside Snapshot
- Core dose: Resuscitation: 500–1000 mL IV bolus, repeat as needed; Maintenance: 1–2 mL/kg/hr; DKA/HHS: often 15–20 mL/kg/hr initially
- Onset/duration: Volume effect immediate; ~25% remains intravascular at 1 hr; most redistributes to interstitium within hours
- Key danger: Hyperchloremic metabolic acidosis with large volumes; volume overload in heart/renal failure; dilutional coagulopathy
- Special: 0.9% NaCl (154 mEq/L each Na⁺ and Cl⁻); slightly hypertonic to plasma; preferred for hyponatremia correction and with blood products; avoid in hypernatremia
Brand & Generic Names
- Generic Name: Sodium chloride
- Common Names: 0.9% Sodium Chloride Injection, USP; Normal Saline (NS)
Medication Class
Isotonic crystalloid; fluid and electrolyte replenisher
Pharmacology
Mechanism of Action:
- Expands the extracellular fluid (ECF) space, increasing intravascular and interstitial volume
- Approximately 25–30% of an isotonic crystalloid bolus remains intravascular after distribution; the rest distributes to the interstitial space
- The high chloride content can lower the strong ion difference, predisposing to a non-anion gap (hyperchloremic) metabolic acidosis
- May cause renal vasoconstriction via tubuloglomerular feedback
Pharmacokinetics/Disposition:
- Distribution: Distributes to ECF (intravascular + interstitial)
- Elimination: Sodium and chloride are primarily eliminated renally with tight hormonal regulation (RAAS/ADH)
- Duration: Effective intravascular volume expansion is transient without ongoing pathology control
- Note: There is no meaningful plasma half-life as with drugs
Indications
- Initial resuscitation of hypovolemia, hemorrhage, sepsis, and shock when isotonic crystalloid is indicated
- Maintenance of intravascular access; medication dilution/carrier fluid
- Priming of tubing and hemodialysis circuits
- Electrolyte disorders and acid-base therapy contexts:
- Hypovolemic hyponatremia (raises serum Na in volume-depleted states)
- Hypernatremia with hypovolemia (restore intravascular volume before free-water replacement)
- Hypermagnesemia (forced diuresis with loop diuretic + NS)
- Hypercalcemia (with loop diuretics for calciuresis)
Note: Many guidelines suggest balanced crystalloids over normal saline for sepsis resuscitation based on recent pragmatic trials showing reduced composite renal outcomes.
Conditions Treated
- Hypovolemia (any cause)
- Hemorrhagic shock
- Septic shock
- Hypovolemic hyponatremia
- Dehydration
- Hypercalcemia (with loop diuretics)
- Hypermagnesemia (with loop diuretics)
Dosing & Administration
Adult Dosing (IV infusion):
- General bolus: 500–1000 mL rapidly; titrate to perfusion (MAP, mentation, urine output)
- Sepsis-induced hypoperfusion or septic shock: 30 mL/kg within the first 3 hours (guideline suggestion)
- Medication carrier: Per drug labeling; common rates 25–150 mL/h as needed
- Transfusion: NS is the preferred fluid for line priming and co-infusion with blood products per AABB standards
Pediatric Dosing:
- Shock/Dehydration bolus: 10–20 mL/kg isotonic crystalloid over 5–20 minutes
- Reassess and repeat to 40–60 mL/kg in the first hour for septic shock where ICU-level care is available
- Special populations: Use 10 mL/kg aliquots in neonates or children with cardiac disease
- Maintenance and special populations per institutional protocols
Contraindications
Absolute Contraindications:
- None for isotonic NS when clinically indicated
Relative Contraindications / Cautions:
- Hypernatremia
- Hyperchloremia
- Severe renal impairment or oliguria/anuria
- Congestive heart failure, cirrhosis, or other edematous states
- Pulmonary edema
- Patients requiring large volumes where balanced crystalloids may be preferable
DKA Caution: Use cautiously in DKA once intravascular volume is restored. Consider switching strategy to avoid hyperchloremic acidosis.
Adverse Effects
Metabolic:
- Hyperchloremic (non-anion gap) metabolic acidosis; decreased strong ion difference
- Acute kidney injury risk signal with high-chloride fluids (observational and pragmatic trial data)
- Hypernatremia
Fluid Overload:
- Peripheral edema
- Pulmonary edema
Local:
- Infusion site irritation
- Infiltration
- Very rare: infection or air embolism related to IV access
Compatibility
Blood Products:
- NS is compatible and preferred through the same line
- Avoid dextrose-containing solutions with blood
- Calcium-containing solutions (e.g., LR) are generally avoided in the same line with PRBCs due to theoretical precipitation with citrate; many institutions retain this policy
Medication Compatibility:
- NS is widely compatible with most medications
- Always check Y-site compatibility for specific agents
Monitoring
Perfusion Monitoring:
- MAP, heart rate, mental status
- Capillary refill
- Urine output (≥0.5 mL/kg/h adults; ≥1 mL/kg/h children)
Electrolytes/Acid-Base:
- Serum sodium, chloride, potassium
- Bicarbonate or base excess
- Lactate
- Venous/arterial blood gas if needed
- Serum osmolality with large-volume therapy
Renal Function:
- Serum creatinine, BUN
- Watch for MAKE30 endpoints in ICU settings (Major Adverse Kidney Events at 30 days)
Fluid Balance and Signs of Overload:
- Weights, input/output
- Lung exam, oxygenation
- Chest imaging if indicated
Formulation & Physicochemical Properties
| Property | Value |
|---|---|
| Ionic composition (per liter) | Na⁺ 154 mEq/L; Cl⁻ 154 mEq/L |
| Osmolarity | ≈308 mOsm/L (calculated) |
| pH (nominal, range) | ≈5.5 (4.5–7.0) |
| Tonicity | Isotonic |
| Container | Single-dose flexible IV bags; also vials for admixture |
| Compatibility | Preferred diluent/flushing fluid; compatible with blood components per transfusion standards |
Clinical Pearls
Chloride Load: Each liter provides 154 mEq of Na⁺ and Cl⁻. Anticipate chloride load and acid-base effects with large-volume resuscitation.
Intravascular Persistence: Roughly 250–300 mL of each liter remains intravascular at steady state. Frequent reassessment prevents fluid overload.
Hypovolemic Hyponatremia: In hypovolemic hyponatremia, NS may raise serum sodium ~1–2 mEq/L per liter infused. Avoid NS in SIADH with high urine osmolality.
Sepsis Resuscitation: Consider balanced crystalloids first for sepsis resuscitation based on current guidelines. NS is reasonable if balanced fluids are unavailable or contraindicated.
Transfusion Lines: Use NS for blood product administration. Avoid dextrose solutions and avoid Y-siting calcium-containing fluids into the same line as PRBCs.
Comparison with Balanced Crystalloids:
| Property | 0.9% Saline | Lactated Ringer's | Plasma-Lyte A |
|---|---|---|---|
| Na (mEq/L) | 154 | 130 | 140 |
| Cl (mEq/L) | 154 | 109–110 | 98 |
| K (mEq/L) | 0 | 4 | 5 |
| Ca (mEq/L) | 0 | 3 (≈2.7) | 0 |
| Buffer | None | Lactate 28 mEq/L | Acetate 27 / Gluconate 23 mEq/L |
| Osmolarity / pH | ≈308 mOsm; pH ~5.5 | ≈273–275 mOsm; pH 6.0–7.5 | ≈294 mOsm; pH ~7.4 |
Evidence Summary: Pragmatic trials in ED/ICU populations found balanced crystalloids reduced a composite renal outcome (death, new RRT, or persistent renal dysfunction) versus saline, with no mortality difference in most subgroups. Sepsis guidelines (adult and pediatric) suggest balanced crystalloids over saline for initial resuscitation, acknowledging low–very low certainty. NS remains appropriate when chloride repletion is desired (e.g., hypochloremic metabolic alkalosis), when co-infusing with blood products, or for specific medication compatibility needs.
References
- 1. Baxter Healthcare Corporation. (2024). Sodium Chloride Injection, USP [Package insert]. U.S. Food and Drug Administration.
- 2. Semler, M. W., Self, W. H., Wanderer, J. P., et al. (2018). Balanced crystalloids versus saline in critically ill adults. The New England Journal of Medicine, 378(9), 829–839.
- 3. Self, W. H., Semler, M. W., Wanderer, J. P., et al. (2018). Balanced crystalloids versus saline in noncritically ill adults. The New England Journal of Medicine, 378(9), 819–828.
- 4. Evans, L., Rhodes, A., Alhazzani, W., et al. (2021). Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2021. Critical Care Medicine, 49(11), e1063–e1143.
- 5. Weiss, S. L., Peters, M. J., et al. (2020). Surviving sepsis campaign international guidelines for the management of septic shock and sepsis-associated organ dysfunction in children. Intensive Care Medicine, 46, 10–67.
- 6. Tonog, P., & Zaidi, S. (2022). Normal Saline. In StatPearls. StatPearls Publishing.
- 7. Singh, S., & Kaur, P. (2023). Ringer's Lactate. In StatPearls. StatPearls Publishing.
- 8. American Association of Blood Banks. (2023). Circular of Information for the Use of Human Blood and Blood Components.
- 9. Pocket Guide to Critical Care Pharmacotherapy. (2010s). Selected sections on fluids and electrolytes.