Hemostasis and Thrombosis by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783030193300
Publisher: Springer International Publishing

 3. Start warfarin evening after surgery with goal INR 2–3

 4. Continue warfarin for at least 6 weeks after transplant

No ideal solution exists for the problem of vascular graft thrombosis. One trial has suggested that antiplatelet agents may be of value in preventing occlusion, but this is associated with a high rate of bleeding.

Paroxysmal Nocturnal Hemoglobinuria (PNH)

PNH is a rare hematological disorder that most often presents with low blood counts, hypocellular bone marrow, and a high incidence of thrombosis which is the leading cause of death in untreated patients. The underlying problem is a mutation in a gene which encodes the enzyme phosphatidylinositol glycan A. This enzyme helps construct the glycosylphosphatidylinositol (GPI) that links cell membrane proteins with the phospholipid membrane. The loss of these membrane proteins causes a variety of clinical effects. The disease takes its name from the loss of red cell membrane proteins which inactivate complement, rendering erythrocytes more susceptible to lysis by the membrane attack complex.

Patients may present with thrombosis at any site. PNH is one of the few thrombophilias which classically presents with Budd-Chiari syndrome . The thrombosis associated with PNH may be refractory to oral anticoagulants, and rare patients may thrombose even on therapeutic doses of heparin. Another diagnostic clue is that many patients have elevated LDH which is reflective of red cell destruction.

Pathogenesis of the thrombosis is unknown. There is speculation that the platelets are also more likely to be activated by complement, leading to thrombosis.

The diagnosis of PNH should be suspected in patients with pancytopenia and thrombosis. The classic “nocturnal hemoglobinuria ” is a rare finding. Most patients will have pancytopenia, although rare patients can present with elevated blood counts. Patients will usually have a high serum LDH. The older “Ham’s test ” and sucrose hemolysis tests have been replaced by flow cytometry. Flow cytometry will directly detect missing membrane proteins. Current technology uses fluorescein-labeled proaerolysin (FLAER) that directly binds GPI and is very sensitive to small cell populations that are missing this linker molecule.

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