What rate of 23.5% saline (sodium chloride) should be administered to an 80 kg patient undergoing Continuous Renal Replacement Therapy (CRRT) to deliver 232 mg/h of sodium?

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Calculating 23.5% Saline Infusion Rate for Sodium Delivery

To deliver 232 mg/h of sodium, you need to infuse 23.5% saline at approximately 1 mL/h.

Calculation Method

The calculation is straightforward using the concentration of sodium in 23.5% saline:

  • 23.5% saline contains 235 mg of sodium per mL (23.5 g NaCl per 100 mL, with sodium comprising approximately 40% of NaCl by weight, yielding ~4 mEq/mL or ~92 mg/mL of elemental sodium). More precisely, 23.5% saline = 4,017 mEq/L = 92,391 mg/L of sodium.

  • To deliver 232 mg/h of sodium:

    • Rate (mL/h) = Desired sodium delivery (mg/h) ÷ Sodium concentration (mg/mL)
    • Rate = 232 mg/h ÷ 235 mg/mL
    • Rate ≈ 0.99 mL/h (approximately 1 mL/h)

Clinical Context for CRRT Patients

While the provided evidence focuses primarily on managing dysnatremia during CRRT rather than sodium supplementation, several principles apply:

  • Monitor serum sodium every 4-6 hours to ensure appropriate correction rates and avoid complications 1, 2.

  • For hyponatremic patients on CRRT, the goal correction rate should be 4-6 mEq/L per 24 hours, not exceeding 8 mEq/L per 24 hours to prevent osmotic demyelination syndrome 1.

  • Standard CRRT replacement fluids contain 140 mEq/L (3,220 mg/L) of sodium 3, 2. When additional sodium supplementation is needed beyond what CRRT provides, hypertonic saline can be administered separately.

Important Considerations

  • This extremely slow infusion rate (1 mL/h) requires a precision infusion pump capable of accurate delivery at low flow rates.

  • The 80 kg patient context suggests this is supplemental sodium being added to a CRRT circuit, likely to prevent excessive sodium removal or to provide controlled sodium delivery 4, 5.

  • Verify the actual concentration of your 23.5% saline solution, as slight variations in formulation could affect the calculation. Commercial preparations should be labeled with exact sodium content.

  • Consider the total sodium balance from all sources including CRRT replacement fluid, dialysate, other IV fluids, and any enteral intake when managing sodium homeostasis 4, 5.

References

1
Guideline

Calculating Prefilter D5W Rate for Hyponatremic Patient on CRRT

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

3
Guideline

CRRT Orders: A Comprehensive Guide

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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