1/4 Normal Saline Infusion Rate Calculation
For an 87.7 kg adult patient, the maintenance infusion rate of 1/4 Normal Saline (1/4NS) should be approximately 108 mL/hour, calculated using the Holliday-Segar formula. 1
Calculation Method Using Holliday-Segar Formula
The Holliday-Segar formula remains the standard approach for calculating maintenance fluid requirements, even though it was originally developed for pediatric patients 1:
Step-by-step calculation for 87.7 kg patient:
- First 10 kg: 100 mL/kg/day = 1,000 mL/day (or 4 mL/kg/hour = 40 mL/hour) 1
- Next 10 kg (10-20 kg): 50 mL/kg/day = 500 mL/day (or 2 mL/kg/hour = 20 mL/hour) 1
- Remaining 67.7 kg (above 20 kg): 25 mL/kg/day = 1,692.5 mL/day (or 1 mL/kg/hour = 67.7 mL/hour) 1
Total maintenance rate = 40 + 20 + 67.7 = 127.7 mL/hour 1
However, since 1/4NS contains less sodium than isotonic solutions, and current guidelines strongly recommend isotonic fluids for maintenance hydration in most clinical scenarios 1, this calculation assumes the clinician has a specific indication for hypotonic fluid use.
Critical Clinical Considerations
Isotonic fluids are strongly preferred over hypotonic solutions like 1/4NS for maintenance hydration in most adult patients. 1 Multiple large meta-analyses have documented increased risk of hospital-acquired hyponatremia (<135 mmol/L) and potentially fatal hyponatremic encephalopathy with hypotonic maintenance fluids compared to isotonic fluids (Na 140 mmol/L). 1
If isotonic fluid (0.9% Normal Saline or balanced crystalloid) is clinically appropriate instead:
- The same calculated rate of approximately 108-128 mL/hour would apply for maintenance needs 1, 2
- For general adult maintenance, rates of 75-100 mL/hour are commonly used to maintain euvolemia 2
Specific Clinical Scenarios Requiring Rate Adjustment
The calculated maintenance rate must be adjusted based on clinical circumstances: 1
- Increased fluid needs: Fever, hyperventilation, hypermetabolism, gastrointestinal losses require higher rates 1
- Decreased fluid needs: Renal failure, congestive heart failure, critical illness, mechanical ventilation, temperature-controlled environments require lower rates 1
- Fluid retention or dehydration: Individual patient needs may deviate markedly from calculated ranges 1
Important Caveats
Monitor for hyponatremia risk: If 1/4NS must be used, frequent electrolyte monitoring is essential, particularly in postoperative patients, critically ill patients, or those with large gastrointestinal losses. 1, 2
Avoid large-volume 0.9% saline when possible: If using isotonic saline at these rates for extended periods, balanced crystalloids (Ringer's lactate, Plasma-Lyte) are preferred over 0.9% saline to prevent hyperchloremic metabolic acidosis. 2
This is maintenance rate only: Additional fluid boluses or replacement of ongoing losses (urinary, stool, insensible losses) must be calculated separately and added to maintenance requirements. 1