Maintenance Fluid Calculation for a 67kg Adult Patient
For a 67kg adult patient, administer approximately 2,175 mL per day (or 91 mL/hour) of isotonic crystalloid solution as maintenance fluid therapy.
Calculation Method
Using the Holliday-Segar formula, which remains the standard approach for calculating maintenance fluid requirements 1:
- First 10 kg: 100 mL/kg/day = 1,000 mL
- Second 10 kg (10-20 kg): 50 mL/kg/day = 500 mL
- Remaining 47 kg (above 20 kg): 25 mL/kg/day = 1,175 mL
- Total: 2,675 mL/day
However, for adults (particularly those >60 years), the recommended baseline is 30-35 mL/kg/day 2:
- At 30 mL/kg: 67 kg × 30 = 2,010 mL/day
- At 35 mL/kg: 67 kg × 35 = 2,345 mL/day
The practical target is approximately 2,000-2,350 mL/day (83-98 mL/hour) 2.
Fluid Type Selection
Use isotonic crystalloid solutions (0.9% sodium chloride or balanced crystalloids) for maintenance therapy 2, 1:
- Isotonic fluids significantly reduce the risk of hospital-acquired hyponatremia compared to hypotonic solutions 2, 3
- Balanced crystalloids may be preferred over 0.9% saline to avoid hyperchloremic acidosis, though evidence is not definitive in adults 2
- The equal sodium-chloride concentration in normal saline can cause hyperchloremia and metabolic acidosis with prolonged use 2
Critical Adjustments Required
Volume Reduction Scenarios
Reduce maintenance fluid volume to 50-60% of calculated amount in patients with 2, 1:
- Heart failure
- Renal failure
- Hepatic failure
- Risk of fluid overload
For this 67kg patient, reduction would mean: 1,000-1,200 mL/day instead of 2,000+ mL/day.
Volume Increase Scenarios
Increase maintenance fluids for 2, 1:
- Fever: Add 2-2.5 mL/kg/day for each 1°C rise above 37°C 2
- For 67kg patient with 39°C fever: add approximately 270-335 mL/day
- Ongoing losses: Diarrhea, vomiting, nasogastric drainage, or hemorrhage require additional replacement 2
- Hyperventilation or hypermetabolic states 1
Electrolyte Supplementation
Standard electrolyte requirements per day 2:
- Sodium: 1-3 mmol/kg/day (67-201 mmol/day for 67kg patient)
- Potassium: 1-3 mmol/kg/day (67-201 mmol/day), added once renal function confirmed 2, 1
- Chloride: 2-4 mmol/kg/day 2
- Calcium: 10 mmol/day 2
- Magnesium: 10 mmol/day 2
- Phosphate: 25 mmol/day 2
Total Fluid Accounting
Calculate total daily fluid intake from ALL sources to prevent "fluid creep" 2, 1, 4:
- IV maintenance fluids
- IV medications and infusions (can represent 32.6% of total daily volume) 4
- Blood products
- Arterial and venous line flushes
- Enteral intake
- Do NOT include: resuscitation boluses or massive transfusion 2
Fluid creep—the hidden volume from medication vehicles—can exceed 600 mL/day and is a major contributor to unintentional fluid overload 4.
Monitoring Requirements
Daily reassessment is mandatory 2, 1:
- Fluid balance: Calculate cumulative fluid balance daily; >10% positive balance predicts worse outcomes 1
- Serum sodium: Monitor at least daily to detect hyponatremia early 2
- Other electrolytes: Potassium, chloride, and other electrolytes based on clinical status 2
- Clinical status: Assess for signs of fluid overload (edema, pulmonary congestion) or dehydration 2
- Urine output: Target adequate output as marker of perfusion 2
Critical Pitfalls to Avoid
Avoid fluid overload, which independently predicts 2, 1:
- Prolonged mechanical ventilation
- Increased ICU length of stay
- Higher mortality
Do not use hypotonic maintenance fluids in acutely ill adults, as they significantly increase hyponatremia risk 2, 3.
Avoid high-rate continuous maintenance infusions; instead use frequent small-volume boluses when additional fluid is needed 2.
Monitor for hyperchloremic acidosis with prolonged 0.9% saline use; consider switching to balanced crystalloids if chloride levels rise 2.