Heparin Drip Rate for DVT Prophylaxis
Critical Clarification: Heparin "Drip" is NOT Used for DVT Prophylaxis
Unfractionated heparin (UFH) for DVT prophylaxis is administered subcutaneously, not as a continuous intravenous drip. 1, 2 A heparin "drip" (continuous IV infusion) is reserved for therapeutic anticoagulation in patients with established DVT or PE, not for prophylaxis. 3
Standard Prophylactic UFH Dosing (Subcutaneous)
Primary Recommendation: Three Times Daily Dosing
For DVT prophylaxis in hospitalized patients, administer UFH 5000 units subcutaneously every 8 hours (three times daily). 1, 2
This regimen is specifically recommended for:
Three times daily dosing has been shown to be more effective than twice-daily administration in preventing DVT in surgical patients. 2
Alternative: Twice Daily Dosing
UFH 5000 units subcutaneously every 12 hours (twice daily) is an acceptable alternative for general medical patients. 1
- Meta-analyses show no significant difference in overall VTE rates between twice-daily versus three times daily dosing in medical patients. 2
- However, twice-daily dosing showed less reduction in the combined endpoint of proximal DVT and PE (p=0.05). 2
- The risk of major bleeding was significantly higher with three times daily dosing (p<0.001), which may favor twice-daily dosing in medical patients at higher bleeding risk. 2
- A large propensity-matched study of 30,800 critically ill patients found no significant difference in new VTE between three times daily (6.16%) versus twice daily (6.23%) dosing (p=0.8). 4
Special Populations
Severe Renal Impairment (CrCl <30 mL/min)
UFH is the preferred agent for DVT prophylaxis in patients with severe renal impairment, using standard dosing of 5000 units subcutaneously every 8 hours without dose adjustment. 2, 3
- UFH is primarily metabolized by the liver rather than renally excreted, making it safe in renal failure. 2, 3
- LMWH is contraindicated when CrCl <30 mL/min due to accumulation and bleeding risk. 5, 3, 6
- A subgroup analysis of the PROTECT trial showed no significant difference in major bleeding between UFH and dalteparin in patients with severe renal dysfunction (8.9% vs. 11.0%; p=0.66). 6
Cancer Patients
Cancer patients should receive UFH 5000 units subcutaneously every 8 hours throughout hospitalization until fully ambulatory. 1, 2
- Consider extended prophylaxis for 10-14 days, and up to 35 days in high-risk surgical patients. 1
When to Choose UFH Over LMWH
Prefer UFH over LMWH in the following situations:
- Severe renal impairment (CrCl <30 mL/min) 2, 3
- Active or history of heparin-induced thrombocytopenia (HIT)—use argatroban, danaparoid, or fondaparinux instead 2, 3
- Settings where rapid reversibility is needed (though less relevant for prophylactic dosing) 2
- Cost considerations or lack of reliable subcutaneous access for LMWH 2
However, LMWH is generally preferred over UFH when renal function is normal due to more predictable pharmacokinetics, reduced healthcare worker exposure, lower rates of missed doses, and lower risk of HIT. 2, 7
Monitoring and Safety
Platelet Monitoring for HIT
Monitor platelet counts every 2-3 days from day 4 to day 14 in patients with HIT risk ≥1%. 5, 2
- UFH has a higher risk of HIT compared to LMWH, with risk as high as 5%. 5
- Post-surgical patients are at particularly high risk. 5
No Routine aPTT Monitoring for Prophylaxis
Do not routinely monitor aPTT or anti-Xa levels for prophylactic UFH dosing. 2
- Monitoring is unnecessary for standard prophylaxis and adds no clinical benefit. 2
Common Pitfalls to Avoid
Do not confuse prophylactic subcutaneous UFH with therapeutic IV heparin drips. Prophylaxis uses fixed subcutaneous dosing without monitoring; therapeutic anticoagulation requires weight-based IV infusion with aPTT monitoring. 3
Do not use UFH in patients with active or history of HIT. Use a direct thrombin inhibitor or fondaparinux instead. 2, 3
Do not administer anticoagulants too close to neuraxial anesthesia due to spinal hematoma risk. 2, 3
Do not use LMWH in severe renal impairment (CrCl <30 mL/min). UFH is the safest choice. 5, 2, 3
Do not overlook injection site bruising, which occurs in approximately 20% of patients but is generally not clinically significant. 8
Efficacy Evidence
A randomized trial in medical patients with heart failure and/or chest infection showed that UFH 5000 units every 8 hours significantly reduced DVT frequency from 26% to 4% (p<0.01). 8
A network meta-analysis of 13 RCTs (9,619 patients) found that LMWH reduces incidence of DVT compared with control treatment (OR 0.59,95% CrI 0.33-0.90; high certainty), while UFH may reduce DVT (OR 0.82,95% CrI 0.47-1.37; low certainty). 7
LMWH is probably more effective than UFH in reducing incidence of DVT (OR 0.72,95% CrI 0.46-0.98; moderate certainty) and should be considered the primary pharmacologic agent for thromboprophylaxis when renal function is normal. 7