Calculating Heparin Units per Hour: A Practical Guide

Calculating heparin units per hour involves determining the infusion rate at which a patient should receive a continuous intravenous (IV) infusion of heparin to achieve a specific therapeutic effect, such as preventing or treating blood clots. Heparin is an anticoagulant medication that is administered in units per hour to maintain the desired level of anticoagulation in the blood. Here's a practical guide on how to calculate heparin units per hour:

Note: This calculation is typically performed by healthcare professionals, such as nurses or pharmacists, and should be based on the specific orders and protocols established by the healthcare provider.

Step 1: Gather Information

1. Heparin Order: Obtain the heparin order from the healthcare provider. This order should specify the target activated partial thromboplastin time (aPTT) or other relevant parameter.

2. Heparin Concentration: Determine the concentration of the heparin solution prescribed for the IV infusion. Common concentrations include 1,000 units/mL or 5,000 units/mL.

3. Patient Weight: Know the patient's weight in kilograms (kg), as dosages may be weight-based.

Step 2: Calculate the Initial Bolus (if applicable)

In some cases, a loading or initial bolus dose of heparin may be prescribed. If so, calculate the initial bolus based on the order. For example, if the order is for 80 units/kg as a bolus and the patient weighs 70 kg:

Initial Bolus = 80 units/kg × 70 kg = 5,600 units

Step 3: Determine the Maintenance Infusion Rate

To calculate the maintenance infusion rate in units per hour, you can use the following formula:

$\text{Infusion Rate (units/hour)} = \frac{\text{Target Rate (units/kg/hour)} × \text{Patient Weight (kg)}}{\text{Heparin Concentration (units/mL)}}$

1. Target Rate (units/kg/hour): The target rate depends on the specific order and the patient's condition. For example, a common starting point for prophylaxis is 18 units/kg/hour.

2. Patient Weight (kg): Use the patient's weight in kilograms.

3. Heparin Concentration (units/mL): The concentration of the heparin solution being used for the infusion (e.g., 1,000 units/mL or 5,000 units/mL).

Step 4: Set the Infusion Pump

Program the infusion pump with the calculated maintenance infusion rate (in units per hour). Ensure that the pump is properly calibrated and set to deliver the correct dosage.

Step 5: Monitor and Adjust

Continuous monitoring of the patient's aPTT or other relevant parameters is essential to ensure that the desired therapeutic effect is achieved. The heparin infusion rate may need to be adjusted based on the patient's response and ongoing clinical assessment.

Please note that this calculation is for informational purposes and should not replace guidance from a qualified healthcare professional. The administration of heparin is a critical medical intervention that requires proper training and adherence to established protocols and guidelines. Always follow the orders and recommendations of the healthcare provider and facility-specific policies when administering medications like heparin.

Heparin units per hour = 25,000 U/mL * 18 U/kg/hr * 75 kg = 1350 U/hr