Von Willebrand’s Disease (vWD)

Evaluation of Mixing Studies:

If lab prolongation is corrected => deficiency of clotting factor

If lab prolongation is not corrected or is only partially corrected, an inhibitor is present (most common inhibitor with in-hospital patients is heparin)

If it is more prolonged with clinical bleeding => an antibody against a clotting factor is present (mostly facors VIII, IX, or XI)

If there is no clinical bleeding but both the PTT and mixing study are prolonged, lupus anticoagulant (predisposition to excessive clotting)

N.B.

If the case describes a hemophilia patient, previously well controlled, who presents with sudden bleeding diathesis, order mixing studies (coagulation factor inhibitor—usually factor VIII inhibitor).

Drugs acting on Eicosanoids

Aspirin, Ibuprofen and other nonselective NSAIDs cause inhibition of platelet aggregation due to dose-dependent inhibition of COX-1. This leads to decreased levels of platelet thromboxane A2 and an increase in bleeding time.

Uremia disrupts platelet function; both adhesion and aggregation are impaired.

Bernard-Soulier syndrome

• autosomal recessive
• disease of platelet adhesion which causes prolonged bleeding times in the presence of normal platelet counts.
• These defective platelets cannot bind to subendothelial collagen properly because of a deficiency or dysfunction of the glycoprotein Ib-IX complex.