When should Low Molecular Weight Heparin (LMWH) be initiated in patients in a ward and Intensive Care Unit (ICU) setting?

LMWH Initiation Timing in Ward and ICU Patients

For VTE prophylaxis in both ward and ICU patients, LMWH should be initiated within 24-48 hours of admission once there are no active bleeding contraindications, with critically ill ICU patients receiving strong priority for early initiation. 1

Ward Patients (Acutely Ill Medical Patients)

Timing of Initiation

• Begin LMWH prophylaxis within 24 hours of hospital admission for acutely ill medical patients at risk for VTE 1
• Standard prophylactic dosing includes enoxaparin 40 mg once daily or dalteparin 5,000 units once daily subcutaneously 1
• Duration should continue for the length of hospital stay or until the patient is fully ambulatory 1

Key Considerations for Ward Patients

• LMWH is strongly recommended over unfractionated heparin (UFH) for prophylaxis in medical patients 1
• Do not extend prophylaxis beyond hospital discharge in standard acutely ill medical patients, as extended outpatient prophylaxis increases bleeding risk without clear benefit 1
• Mechanical prophylaxis alone (compression devices) should only be used if pharmacological prophylaxis is contraindicated 1

ICU Patients (Critically Ill Medical Patients)

Timing of Initiation

• Initiate LMWH prophylaxis within 24-48 hours of ICU admission for all critically ill patients without contraindications 1, 2
• In a Franco-Canadian study, 91.7% of eligible medical ICU patients appropriately received either UFH or LMWH prophylaxis, with most initiated early in the ICU course 2
• For trauma patients in the ICU, LMWH can be safely initiated within 48 hours of admission, even in those with stable intracranial injuries 3

Dosing Considerations for ICU Patients

• LMWH is preferred over UFH in critically ill patients (strong recommendation from the American Society of Hematology) 1
• Standard prophylactic doses may be insufficient in critically ill patients with obesity, severe inflammation, or hypercoagulability 4, 5
• For obese ICU patients (BMI ≥30 kg/m²), consider intermediate doses: enoxaparin 4000 IU every 12 hours subcutaneously instead of standard once-daily dosing 5
• In patients with renal failure (creatinine clearance <30 mL/min), UFH may be preferred over LMWH 1, 2

Special ICU Populations

Mechanically Ventilated Patients:

• Mechanical ventilation is an independent predictor for receiving heparin prophylaxis (OR 2.4) and should prompt immediate LMWH initiation 2
• These patients have higher VTE risk and benefit most from early prophylaxis 2

Trauma ICU Patients:

• LMWH can be safely initiated within 48 hours even in multisystem trauma patients requiring multiple procedures 3
• DVT screening with duplex ultrasonography should be performed within 48 hours of admission and repeated after 7-10 days 3
• Once-daily dalteparin prophylaxis in high-risk trauma patients showed DVT rates of only 3.9% and PE rates of 0.8% 3

COVID-19 ICU Patients:

• Standard prophylactic LMWH doses may be inadequate due to hypercoagulability 4, 5
• Consider intensified dosing (intermediate or therapeutic doses) based on D-dimer levels (>3 μg/mL) and fibrinogen levels (>8 g/L) 5
• Monitor anti-factor Xa levels as standard dosing often fails to achieve target prophylactic range 4

Contraindications to Assess Before Initiation

Absolute contraindications requiring delay:

• Active major bleeding or recent hemorrhage 6
• Recent intracranial hemorrhage or stroke 6
• Ongoing gastrointestinal bleeding 6
• Severe thrombocytopenia (platelets <50,000/μL) 1

Relative contraindications requiring risk-benefit assessment:

• Recent surgery within 48-72 hours (high bleeding risk procedures) 1, 7
• Epidural catheter in place (maintain 10-12 hour interval before/after LMWH dose) 1
• Moderate renal impairment (adjust dose or use UFH) 1

Monitoring Requirements

For Ward Patients:

• Baseline hemoglobin, platelet count, and creatinine before initiation 7
• No routine anti-factor Xa monitoring needed for standard prophylactic doses 1

For ICU Patients:

• Monitor platelet count if LMWH continued beyond 5 days (risk of heparin-induced thrombocytopenia) 6
• Consider anti-factor Xa monitoring in obese patients, those with renal dysfunction, or when using non-standard doses 4, 5
• Reassess renal function postoperatively as it affects LMWH dosing 7
• In critically ill patients with severe inflammation, monitor D-dimers and fibrinogen every 48 hours to guide dose intensification 5

Common Pitfalls to Avoid

• Do not delay LMWH initiation beyond 48 hours in eligible patients, as VTE risk increases significantly with prolonged immobilization 1, 3
• Do not use standard prophylactic doses in morbidly obese ICU patients (>120 kg); these patients require weight-adjusted intermediate dosing 5
• Do not administer LMWH within 10-12 hours of neuraxial procedures or epidural catheter removal to avoid spinal hematoma 1
• Do not assume standard doses are adequate in critically ill patients with marked hypercoagulability; consider monitoring and dose adjustment 4, 5