Heparin Drip Calculation Practice

Find the bag's concentration, then divide the dose by it. Concentration: 25,000 units ÷ 500 mL = 50 units/mL. Rate: 1,300 units/hr ÷ 50 units/mL = 26 mL/hr, written with no trailing zero. Check backward: 26 mL/hr × 50 units/mL = 1,300 units/hr. Common errors: multiplying instead of dividing (65,000), or using 100 units/mL, the strength of a 250 mL bag, which gives 13 mL/hr and half the prescribed dose. Heparin is a high-alert medication, and many agencies require an independent double check of the rate. Takeaway: mL/hr = units/hr ÷ units/mL; read the bag's concentration every time.

Sources: DailyMed: Heparin Sodium in 5% Dextrose Injection label (25,000 units in 500 mL and in 250 mL; dose adjusted by aPTT); StatPearls: Dose Calculation Dimensional Analysis Factor-Label Method; Open RN Nursing Skills (ACC adaptation), 5.15 IV Infusion by Pump; ISMP List of High-Alert Medications in Acute Care Settings (2024)

To find the dose a pump is giving, multiply the rate by the bag's concentration. Concentration: 25,000 units ÷ 250 mL = 100 units/mL. Dose: 14 mL/hr × 100 units/mL = 1,400 units/hr. The mL cancel, leaving units/hr. Common errors: using 50 units/mL, the strength of a 500 mL bag, which gives 700 units/hr, or dividing the rate by the concentration. The nurse compares the 1,400 units/hr with the current prescription; if they do not match, the nurse verifies the prescription before changing anything. Takeaway: units/hr = mL/hr × units/mL. Working backward from the pump is a quick check at handoff.

Sources: DailyMed: Heparin Sodium in 5% Dextrose Injection label (25,000 units in 500 mL and in 250 mL; dose adjusted by aPTT); StatPearls: Dose Calculation Dimensional Analysis Factor-Label Method

The aPTT of 43 seconds is below the target of 48 to 64 seconds and falls in the protocol row for 40 to 47 seconds: bolus 40 units/kg and increase the infusion by 2 units/kg/hr. New dose per kg: 18 + 2 = 20 units/kg/hr. New dose: 20 units/kg/hr × 81.6 kg = 1,632 units/hr. The 40 units/kg bolus (3,264 units) is given separately and is not added to the hourly dose. Common errors: adding 2 units/hr rather than 2 units/kg/hr, or using the row for less than 40 seconds. To set the pump, the nurse then divides by the bag's 50 units/mL: 32.6 mL/hr. Takeaway: read the aPTT against the protocol, change the units/kg/hr, then multiply by the weight in kg.

Sources: Raschke RA et al. The weight-based heparin dosing nomogram. Ann Intern Med 1993 (80 units/kg bolus, 18 units/kg/hr); Schurr JW et al. Implementation of a weight-based, nurse-driven heparin nomogram. Clin Appl Thromb Hemost 2018; DailyMed: Heparin Sodium in 5% Dextrose Injection label (25,000 units in 500 mL and in 250 mL; dose adjusted by aPTT); DailyMed: Heparin sodium injection label (aPTT 1.5 to 2 times normal); StatPearls: Partial Thromboplastin Time

Bolus dose: 80 units/kg × 74 kg = 5,920 units. Volume: 5,920 units ÷ 5,000 units/mL = 1.184 mL. A volume of 1 mL or more is rounded to the nearest tenth, so the nurse draws up 1.2 mL. Common errors: stopping at 5,920 and recording units instead of mL, or dividing 5,000 by 5,920. Heparin vials come in several strengths, and mix-ups between them have caused fatal errors, so the nurse reads the concentration on the vial and follows agency policy on an independent double check before giving the bolus. Takeaway: bolus units = units/kg × kg; then mL = units ÷ units/mL on the vial.

Sources: Raschke RA et al. The weight-based heparin dosing nomogram. Ann Intern Med 1993 (80 units/kg bolus, 18 units/kg/hr); DailyMed: Heparin Sodium Injection label (verify the strength before use); DailyMed: Heparin Sodium Injection vials label (1,000, 5,000 and 10,000 units/mL); Open RN Nursing Skills (ACC adaptation), 5.5 Rounding; ISMP List of High-Alert Medications in Acute Care Settings (2024)

The aPTT of 86 seconds is above the target of 42 to 56 seconds and falls in the row for greater than 70 seconds: hold for 1 hour, then decrease by 3 units/kg/hr. Weight: 196 lb ÷ 2.2 = 89.09 kg, rounded to 89.1 kg. New dose per kg: 18 − 3 = 15 units/kg/hr. New dose: 15 units/kg/hr × 89.1 kg = 1,336.5 units/hr. Concentration: 25,000 units ÷ 250 mL = 100 units/mL. Rate: 1,336.5 units/hr ÷ 100 units/mL = 13.365 mL/hr, rounded to 13.4 mL/hr. Common errors: using 196 as kg, using 50 units/mL, or restarting at the old rate of 16 mL/hr. Takeaway: convert the weight, apply the protocol change in units/kg/hr, then divide by the bag's units/mL.

Sources: Raschke RA et al. The weight-based heparin dosing nomogram. Ann Intern Med 1993 (80 units/kg bolus, 18 units/kg/hr); Schurr JW et al. Implementation of a weight-based, nurse-driven heparin nomogram. Clin Appl Thromb Hemost 2018; DailyMed: Heparin Sodium in 5% Dextrose Injection label (25,000 units in 500 mL and in 250 mL; dose adjusted by aPTT); DailyMed: Heparin sodium injection label (aPTT 1.5 to 2 times normal); StatPearls: Partial Thromboplastin Time; Open RN Nursing Skills (ACC adaptation), 5.4 Equivalencies