What are the contraindications for Low Molecular Weight Heparin (LMWH)?

Contraindications for Low Molecular Weight Heparin (LMWH)

LMWH is absolutely contraindicated in patients with active major bleeding, severe thrombocytopenia (platelets <30,000-50,000 × 10⁹/L), underlying bleeding disorders, and history of heparin-induced thrombocytopenia (HIT). 1, 2

Absolute Contraindications

Active Bleeding and Hemorrhagic Conditions

• Active, uncontrollable bleeding that cannot be reversed with medical or surgical intervention, including bleeding in critical sites (intracranial, spinal, retroperitoneal) 1, 2
• Recent intracranial or cerebral hemorrhage or active cerebrovascular bleeding 1, 2
• Dissecting or cerebral aneurysm due to catastrophic bleeding risk 1

Hematologic Contraindications

• Severe thrombocytopenia with platelet counts <30,000-50,000 × 10⁹/L 1, 2
• Underlying bleeding disorders including hemophilia, von Willebrand disease, or baseline prolonged prothrombin time/partial thromboplastin time (excluding lupus anticoagulant) 1
• History of heparin-induced thrombocytopenia (HIT) - this is critical as LMWH can cross-react with HIT antibodies despite lower risk of causing initial HIT 3, 4

Other Absolute Contraindications

• Severe, uncontrolled malignant hypertension (systolic >200 mmHg, diastolic >110 mmHg) 2, 3
• Bacterial endocarditis due to embolic and bleeding complications 1
• Active pericarditis 1

Relative Contraindications

Gastrointestinal and Recent Surgical

• Active peptic ulcer disease or gastrointestinal ulceration at high risk for bleeding 1, 2
• Major surgery or serious bleeding within the past 2 weeks 2

Neurologic Considerations

• Intracranial or spinal lesions at high risk for bleeding 2
• Recent CNS bleeding (within past 4 weeks) 2
• Severe head trauma 1
• Epidural catheter placement or neuraxial anesthesia - extreme caution required due to risk of epidural hematoma 2

Organ Dysfunction

• Severe renal insufficiency (creatinine clearance <30 mL/min) - LMWH accumulates due to renal elimination, significantly increasing bleeding risk 1, 5

  • Standard therapeutic doses of enoxaparin show 3.88-fold increased major bleeding risk in severe renal impairment 5
  • If LMWH must be used, consider dalteparin or tinzaparin which have lower renal metabolism, or use unfractionated heparin instead 1, 6

• Hepatic insufficiency with elevated INR (>1.5) affects baseline coagulation 2, 3

Hematologic

• Persistent thrombocytopenia (even if not severe) increases bleeding risk 2
• Severe platelet dysfunction compounds anticoagulant effects 2

Special Clinical Situations

When LMWH is Contraindicated - Alternative Approaches

• Use mechanical prophylaxis including intermittent pneumatic compression devices or graduated compression stockings when pharmacologic prophylaxis is contraindicated 1, 2
• Consider unfractionated heparin (UFH) in patients with severe renal impairment, high bleeding risk, or need for urgent procedures due to shorter half-life and reversibility 1, 6
• For patients with HIT requiring anticoagulation, use alternative agents such as direct thrombin inhibitors (argatroban, bivalirudin) or fondaparinux - never use LMWH 3, 7

High-Risk Populations Requiring Dose Adjustment

• Morbid obesity - requires weight-based dosing (0.5 mg/kg/day) rather than fixed dosing; dose capping leads to high thrombosis rates 1
• Elderly patients ≥90 years with creatinine clearance <60 mL/min should not receive tinzaparin 3

Context-Specific Contraindications in Sepsis

In patients with severe sepsis and contraindications to heparin (thrombocytopenia, severe coagulopathy, active bleeding, recent intracerebral hemorrhage), mechanical prophylaxis should be used instead, with pharmacologic prophylaxis initiated when risk decreases 1

Critical Pitfalls to Avoid

• Do not assume LMWH is safe in HIT - while LMWH has 2-3 fold lower risk of causing HIT compared to UFH, it cross-reacts with existing HIT antibodies and is absolutely contraindicated in patients with HIT history 4, 8
• Monitor platelet counts even with LMWH therapy, as LMW-HIT can occur with delayed onset and more severe thrombocytopenia than UFH-induced HIT 8
• Avoid standard enoxaparin dosing in severe renal impairment - this specific combination shows the highest bleeding risk; empirically adjusted doses may be safer 5
• Never use LMWH in patients with active major bleeding regardless of indication strength 1, 2