Heparin Infusion Rate Calculation for 1000 Units/Hour
For a pre-mixed heparin solution of 25,000 units in 500cc, the infusion rate to deliver 1000 units per hour is 20 mL/hour.
Calculation Method
- To calculate the infusion rate, you need to determine the concentration of the heparin solution and then apply the formula: Rate (mL/hr) = Desired dose (units/hr) ÷ Concentration (units/mL) 1
- The concentration of the pre-mixed solution is: 25,000 units ÷ 500 mL = 50 units/mL 1
- Therefore: Infusion rate = 1000 units/hr ÷ 50 units/mL = 20 mL/hr 1
Verification and Clinical Context
- This calculation follows standard practice for continuous IV heparin infusions, where the rate is determined by dividing the desired hourly dose by the concentration of the solution 2
- For therapeutic anticoagulation, the FDA recommends continuous infusion rates of 20,000-40,000 units/24 hours (approximately 830-1,670 units/hour) 2
- The prescribed dose of 1000 units/hour falls within this recommended range for therapeutic anticoagulation 2
Monitoring Considerations
- When administering heparin by continuous IV infusion, monitor aPTT at baseline, approximately 4 hours after initiation, and after any dose adjustments 2
- The target therapeutic range for aPTT is typically 1.5-2.5 times the control value (approximately 45-75 seconds) 1
- Early achievement of therapeutic aPTT (within 24 hours) is associated with better outcomes in patients with thromboembolism 1, 3
Common Pitfalls to Avoid
- Using incorrect concentration calculations can lead to significant dosing errors; always verify the concentration of pre-mixed solutions 2
- Failure to invert the container at least six times when adding heparin to an infusion solution can result in inadequate mixing and pooling of heparin 2
- Inadequate initial dosing may delay achievement of therapeutic anticoagulation, potentially increasing the risk of thrombotic complications 4, 3
- Weight-based dosing protocols (typically 18 units/kg/hr) are more effective than fixed-dose regimens for rapidly achieving therapeutic anticoagulation, but require patient weight for calculation 3