How much NaCl (sodium chloride) is needed to make 750 mL of 0.85% saline?

Calculating NaCl for 0.85% Saline Solution

To make 750 mL of 0.85% saline solution, you need 6.375 grams of NaCl (sodium chloride).

Calculation Method

The calculation for determining the amount of NaCl needed is straightforward:

1. A percentage solution indicates grams of solute per 100 mL of solution
2. For 0.85% saline: 0.85 g NaCl per 100 mL solution
3. For 750 mL solution: (0.85 g/100 mL) × 750 mL = 6.375 g NaCl

Verification of Calculation

This calculation can be verified using the formula:

• Weight (g) = (Concentration percentage × Volume in mL) ÷ 100
• Weight (g) = (0.85 × 750) ÷ 100 = 6.375 g

Clinical Context of Saline Solutions

Different concentrations of saline have specific clinical applications:

• 0.85% saline (our target solution) is slightly hypotonic compared to plasma
• 0.9% saline (normal saline) has an osmolarity of 308 mOsm/L and sodium concentration of 154 mmol/L 1
• Balanced crystalloids generally have lower sodium and chloride concentrations than normal saline

Common Pitfalls to Avoid

• Measurement accuracy: Use a calibrated scale for precise measurement of NaCl
• Solution preparation: Dissolve NaCl completely in water before adjusting to final volume
• Storage considerations: Store in appropriate containers to maintain sterility if for clinical use
• Concentration verification: For critical applications, verify concentration using appropriate methods

Additional Considerations

When preparing saline solutions for clinical use:

• Use pharmaceutical grade NaCl
• Use sterile water for injection
• Prepare in aseptic conditions
• Follow institutional protocols for solution preparation
• Label properly with concentration, preparation date, and expiration date

This calculation method can be applied to prepare any concentration of saline solution by adjusting the percentage in the formula accordingly.