Heparin-Induced Thrombocytopenia with LMWH Prophylaxis

Risk Stratification for HIT with LMWH

The American Society of Anesthesiologists notes that medical patients receiving LMWH prophylaxis have a low risk of HIT, approximately 0.2%, which is considered low risk (<0.1-0.2%) 1, 2
The risk of developing HIT with LMWH varies by clinical context, with low risk (<0.1%) observed in medical patients receiving LMWH prophylaxis (except cancer patients) 1, 3
Obstetrical patients outside surgical context have a low risk of HIT with LMWH [<0.1%) 3, 4
Minor trauma patients have a low risk of HIT with LMWH [<0.1%) 5
Any heparin treatment (UFH or LMWH) lasting beyond one month has a low risk of HIT [<0.1%) 3
Surgical patients receiving LMWH prophylaxis have an intermediate risk of HIT (0.1-1%) 1, 6
Cancer patients receiving LMWH have an intermediate risk of HIT (0.1-1%) 3
Severe trauma patients receiving LMWH have an intermediate risk of HIT (approximately 0.36%) 3
Post-cardiac surgery patients receiving LMWH have an intermediate risk of HIT (approximately 0.4%) 3
Most patients receiving UFH (prophylactic or therapeutic) have a high risk of HIT (>1%) 3, 6

The American College of Chest Physicians recommends that low-risk patients (medical patients on LMWH prophylaxis) do not require routine platelet monitoring 3, 7
Intermediate-risk patients (surgical patients on LMWH) should have platelet monitoring once to twice weekly 7
All patients should have a baseline platelet count before initiating heparin therapy 7

Continuing LMWH in patients with suspected HIT while awaiting laboratory confirmation is a common pitfall 3
Delaying alternative anticoagulation when HIT is suspected is a common pitfall 3
Not obtaining baseline platelet counts before initiating heparin therapy is a common pitfall 7