Continuous Infusion of Unfractionated Heparin for DVT Prophylaxis
Continuous intravenous infusion of unfractionated heparin (UFH) is NOT the recommended route for DVT prophylaxis—subcutaneous administration at 5000 IU every 8 hours is the standard prophylactic regimen. 1, 2, 3
Why Continuous Infusion is Not Used for Prophylaxis
Continuous IV infusion is reserved exclusively for therapeutic anticoagulation, not prophylaxis, as it requires intensive monitoring, IV access, and hospitalization 1, 3
The therapeutic continuous infusion regimen consists of an initial 5000 IU IV bolus followed by 20,000-40,000 units per 24 hours (or 18 U/kg/hour) with aPTT monitoring every 4 hours to maintain levels 1.5-2.5 times control 1, 3
This intensive regimen is indicated for treatment of established DVT or pulmonary embolism, not prevention 1
Correct UFH Prophylactic Regimen
Standard Dosing
The recommended prophylactic dose is UFH 5000 IU subcutaneously every 8 hours, which provides superior DVT prevention compared to twice-daily dosing in surgical patients 1, 2, 4, 3
Three times daily dosing (every 8 hours) provides more consistent anticoagulant effect and reduces DVT incidence more effectively than every 12-hour administration 2, 4
Administer via deep subcutaneous injection into the abdominal fat layer or above the iliac crest, rotating injection sites to prevent hematoma formation 3
Timing Considerations
Begin prophylaxis 2 hours before surgery and continue every 8-12 hours for at least 7 days or until the patient is fully ambulatory, whichever is longer 3
For medical patients, continue until hospital discharge or full ambulation 4
When UFH Prophylaxis is Preferred Over LMWH
Severe renal impairment (CrCl <30 mL/min): UFH is the agent of choice as it is primarily metabolized by the liver rather than renally excreted 2, 4, 5
Patients at high bleeding risk where rapid reversibility may be needed, though this is less relevant for prophylactic dosing 2
When LMWH is contraindicated or unavailable in ICU settings 2
Critical Monitoring and Safety
Do NOT routinely monitor aPTT or anti-Xa levels for prophylactic subcutaneous dosing—this is unnecessary and not indicated 2, 4
Monitor platelet counts every 2-3 days from day 4 to day 14 to screen for heparin-induced thrombocytopenia (HIT), which has a risk ≥1% 2
Absolute contraindications include: active or history of HIT (use argatroban or fondaparinux instead) and recent neuraxial anesthesia due to spinal hematoma risk 2, 4, 5
Avoid intramuscular administration due to frequent hematoma formation at injection sites 3
Common Pitfall to Avoid
The most critical error is confusing therapeutic anticoagulation (which uses continuous IV infusion) with prophylaxis (which uses subcutaneous dosing). Continuous infusion requires 5000 IU bolus followed by 18 U/kg/hour with intensive aPTT monitoring every 4 hours—this is appropriate only for treating established thrombosis, not preventing it. 1, 3