Management of Prolonged Partial Thromboplastin Time (PTT)

Causes of Prolonged PTT

Anticoagulant therapy, particularly unfractionated heparin (UFH) or low molecular weight heparin (LMWH), is the most common cause of prolonged PTT in clinical settings 1
Heparin-induced thrombocytopenia (HIT) can cause prolonged PTT and requires monitoring platelet counts every 2-3 days from day 4 to day 14 of therapy 2

The American College of Cardiology recommends verifying if a patient is receiving anticoagulants, and reviewing medication history for UFH, LMWH, direct thrombin inhibitors, or warfarin 1, 3
For patients on heparin therapy, the target PTT range should be 1.5-2.5 times the control value for UFH 2

For patients on UFH, the standard IV dosing is 80 U/kg bolus followed by 18 U/kg/hour infusion, and the dose should be adjusted to maintain PTT ratio of 1.5-2.5 times control value 2
For patients with renal impairment, caution should be used with LMWH if creatinine clearance <30 mL/min due to drug accumulation, and consideration should be given to UFH with careful monitoring or reduced LMWH dosing with anti-Xa monitoring 3, 4
The American Heart Association recommends that for patients with HIT, all heparin products should be discontinued, and alternative anticoagulants such as argatroban should be considered 4

For pregnant women, heparin does not cross the placenta and is generally considered safer than warfarin during pregnancy, and LMWH may offer advantages over UFH during pregnancy 5
The American College of Chest Physicians recommends that for patients on UFH, protamine sulfate should be used to reverse anticoagulation if bleeding occurs, at a dose of 1 mg per 100 units of heparin administered in the last 2-3 hours (maximum 50 mg) 1