What is the protocol for ordering a heparin drip?

Heparin Drip Ordering Protocol

For therapeutic anticoagulation, initiate heparin with an 80 units/kg IV bolus followed by 18 units/kg/hour continuous infusion, targeting an aPTT of 1.5-2.5 times control (approximately 50-70 seconds), with the first aPTT checked 6 hours after initiation. 1, 2

Initial Dosing

Standard Weight-Based Protocol

• Bolus dose: 80 units/kg IV push (maximum 10,000 units for patients >125 kg) 1, 2
• Initial infusion rate: 18 units/kg/hour 1, 2
• This weight-based approach achieves therapeutic anticoagulation in 97% of patients within 24 hours, compared to only 77% with fixed-dose regimens 3

Alternative Dosing for Specific Conditions

• ST-elevation MI with fibrinolytic therapy: 60 units/kg bolus (maximum 4,000 units) followed by 12 units/kg/hour (maximum 1,000 units/hour initial infusion) 1, 2
• Cardiac surgery/PCI: 100-150 units/kg bolus, targeting ACT >300 seconds 1, 4, 2
• Pediatric patients: 75-100 units/kg bolus over 10 minutes, then 25-30 units/kg/hour for infants or 18-20 units/kg/hour for children >1 year 2

Monitoring Protocol

Timing of Laboratory Tests

• First aPTT: Draw 6 hours after bolus dose 1
• Subsequent aPTTs: Every 6 hours until therapeutic, then every 4 hours initially, then at appropriate intervals once stable 1, 2
• Target aPTT: 1.5-2.5 times control (typically 50-70 seconds or 45-75 seconds depending on reagent) 1, 4

Additional Monitoring

• Platelet count: Check daily to monitor for heparin-induced thrombocytopenia 1, 2
• Hematocrit and occult blood: Monitor periodically throughout therapy 2
• Achieving therapeutic aPTT within 24 hours is critical—failure to do so increases recurrent thromboembolism risk 10-22 fold 1

Dose Adjustment Nomogram

Use this table for aPTT-based adjustments: 1, 2

aPTT Result	Action	Repeat aPTT
<35 seconds (<1.2× control)	80 units/kg bolus, increase infusion by 4 units/kg/hour	6 hours
35-45 seconds (1.2-1.5× control)	40 units/kg bolus, increase infusion by 2 units/kg/hour	6 hours
46-70 seconds (1.5-2.3× control)	No change	Next morning or per protocol
71-90 seconds (2.3-3× control)	Decrease infusion by 2 units/kg/hour	6 hours
>90 seconds (>3× control)	Hold infusion 1 hour, then decrease by 3 units/kg/hour	6 hours

Preparation and Administration

Critical Safety Steps

• Verify vial concentration to avoid confusing 1 mL treatment vials with catheter lock flush vials—this is a common fatal error 2
• Inspect solution: Use only if clear and seal intact 2
• Mix thoroughly: Invert infusion container at least 6 times to prevent pooling 2

Route of Administration

• Preferred: Continuous IV infusion via dedicated line 1, 2
• Alternative: Deep subcutaneous injection (above iliac crest or abdominal fat layer) for prophylaxis only 2
• Never use: Intramuscular route due to hematoma risk 2

Special Populations

Morbidly Obese Patients

• Consider using a modified dosing weight calculated as the average of actual body weight and ideal body weight, rather than actual body weight alone, to avoid supratherapeutic levels 5
• Standard weight-based dosing using actual body weight may result in excessive anticoagulation 5

Renal Impairment

• Heparin clearance involves both saturable (cellular) and nonsaturable (renal) mechanisms 1
• At therapeutic doses, most clearance is via the saturable mechanism, so dose adjustment is generally not required 1
• Monitor aPTT more frequently in severe renal dysfunction 1

Pregnancy

• Use preservative-free formulations only 2
• Heparin does not cross the placenta and is safe in pregnancy 6

Common Pitfalls to Avoid

• Subtherapeutic dosing in first 24 hours: This increases recurrent VTE risk by 10-22 fold—be aggressive with initial dosing 1
• Using fixed-dose rather than weight-based protocols: Weight-based dosing achieves therapeutic levels 20% more often 3
• Delaying first aPTT beyond 6 hours: Early monitoring allows rapid dose optimization 1
• Forgetting platelet monitoring: HIT can occur in up to 5% of patients receiving UFH 1
• Using actual body weight in morbidly obese patients: This may lead to overdosing 5

Duration and Transition

• Continue heparin for 5-10 days for VTE treatment 6, 7
• Overlap with warfarin for 4-5 days until INR is therapeutic (2-3) for at least 24 hours before discontinuing heparin 2, 6
• For direct oral anticoagulants, stop heparin infusion immediately after first dose or 0-2 hours before next scheduled intermittent dose 2