Sodium Content in Normal Saline
A liter of normal saline (0.9% NaCl) contains 154 mmol of sodium.
Normal saline is composed of 9.0 grams of sodium chloride (NaCl) per liter of water 1. This translates to:
Key Clinical Context
Normal saline is slightly hyperosmolar, not truly "isotonic" despite its common designation 1. The term "normal saline" is actually a historical misnomer with little scientific basis for its routine use, originating from misconceptions during the 1831 cholera pandemic rather than physiological principles 3.
Important Physiological Considerations
The equal concentrations of sodium and chloride in normal saline (154 mmol/L each) are non-physiological 2, 4. In normal plasma, sodium concentration is approximately 140 mmol/L while chloride is only 100-106 mmol/L—a difference of about 40 mEq/L 2. This discrepancy means that large-volume administration of normal saline can cause:
- Hyperchloremic metabolic acidosis in a dose-dependent manner 2, 4
- Potential renal dysfunction compared to balanced crystalloid solutions 5, 2
- Worsening of pre-existing acidosis, particularly when associated with hyperchloremia 1, 5
Clinical Recommendations
Recent guidelines increasingly favor balanced crystalloid solutions (such as Lactated Ringer's or Plasma-Lyte) over normal saline for most clinical applications 1, 5. When normal saline must be used, it should be limited to a maximum of 1-1.5 liters to minimize hyperchloremic effects 1, 5.
The only clear indication where normal saline remains preferred is in hypovolemic hyponatremia where true volume depletion exists 6. In patients with severe head trauma, hypotonic solutions like Ringer's lactate should be avoided, but this doesn't necessarily mandate normal saline use 1.