IV Normal Saline Q4H Over 24 Hours: Volume Calculation
For a 38-kg patient receiving IV normal saline every 4 hours over 24 hours, the total volume administered depends entirely on the clinical indication and ordered volume per dose—there is no standard "Q4H" volume without specifying the amount per administration.
Understanding the Order
The abbreviation "Q4H" means "every 4 hours," which results in 6 doses over 24 hours (at hours 0,4,8,12,16, and 20). However, this frequency alone does not determine total volume—you must know the volume ordered per dose.
Common Clinical Scenarios for This Patient
Maintenance Fluid Therapy
- For a 38-kg pediatric patient, maintenance fluid requirements using the 4-2-1 rule are 78 mL/hour, totaling approximately 1,872 mL (1.9 L) over 24 hours 1
- First 10 kg: 4 mL/kg/hr = 40 mL/hr
- Next 10 kg: 2 mL/kg/hr = 20 mL/hr
- Remaining 18 kg: 1 mL/kg/hr = 18 mL/hr
- Total: 78 mL/hr × 24 hours = 1,872 mL
- If dividing this into Q4H dosing: approximately 312 mL every 4 hours = 1.9 L total over 24 hours 1
Resuscitation/Bolus Therapy
- Initial fluid boluses for shock or severe dehydration are 10-20 mL/kg (380-760 mL per bolus for this patient), with reassessment after each bolus 2
- Up to 40-60 mL/kg (1,520-2,280 mL total) may be required in the first hour for septic shock if intensive care is available 2
- For anaphylaxis, children may receive up to 30 mL/kg (1,140 mL) in the first hour 3
Scheduled Intermittent Dosing
If the order specifies a fixed volume Q4H (e.g., "250 mL NS Q4H"):
- 250 mL × 6 doses = 1.5 L over 24 hours
- 500 mL × 6 doses = 3.0 L over 24 hours
Critical Monitoring Considerations
- Reassessment after each fluid administration is mandatory to prevent fluid overload, particularly monitoring heart rate, blood pressure, capillary refill, mental status, and urine output 2
- Avoid exceeding 60 mL/kg/day (2,280 mL for this patient) of crystalloid, as volumes above this threshold are associated with significantly worse outcomes in pediatric trauma patients 2
- Patients with congestive heart failure, chronic renal disease, or hepatic failure require reduced volumes and close monitoring to prevent volume overload 3, 2
Clinical Pitfall
The most common error is assuming "Q4H" implies a standard volume—it does not. Always verify the ordered volume per dose with the prescribing physician. Without this information, you cannot calculate total 24-hour volume. The clinical context (maintenance vs. resuscitation vs. medication dilution) dramatically changes the appropriate volume.