Which scenario is a contraindication to pharmacologic DVT prophylaxis after surgery?

Which scenario is a contraindication to pharmacologic DVT prophylaxis after surgery?

• A. History of heparin-induced thrombocytopenia
• B. Age over 70
• C. Prior DVT
• D. Mild dehydration

Answer: (A)

The key idea is understanding when pharmacologic DVT prophylaxis cannot be used because of a reaction to heparin. Heparin-induced thrombocytopenia is an immune-mediated problem where exposure to heparin leads to antibodies that activate platelets, creating a high risk of dangerous thrombosis. In someone with a history of HIT, giving heparin or low-molecular-weight heparin can trigger or worsen clotting, so it is a contraindication to using these agents for prophylaxis. Instead, you rely on mechanical methods (like intermittent pneumatic compression or early ambulation) and consider non-heparin anticoagulants if needed, under careful guidance. Why the other scenarios aren’t contraindications: being over 70 years old does not by itself prohibit pharmacologic prophylaxis; many elderly patients safely receive it with bleeding risk considered. A prior DVT does not preclude prophylaxis, though the history may influence the choice or duration of prophylaxis. Mild dehydration is not a contraindication to pharmacologic prophylaxis; it may affect overall fluid management, but it does not by itself prevent use of anticoagulants.

The key idea is understanding when pharmacologic DVT prophylaxis cannot be used because of a reaction to heparin. Heparin-induced thrombocytopenia is an immune-mediated problem where exposure to heparin leads to antibodies that activate platelets, creating a high risk of dangerous thrombosis. In someone with a history of HIT, giving heparin or low-molecular-weight heparin can trigger or worsen clotting, so it is a contraindication to using these agents for prophylaxis. Instead, you rely on mechanical methods (like intermittent pneumatic compression or early ambulation) and consider non-heparin anticoagulants if needed, under careful guidance.

Why the other scenarios aren’t contraindications: being over 70 years old does not by itself prohibit pharmacologic prophylaxis; many elderly patients safely receive it with bleeding risk considered. A prior DVT does not preclude prophylaxis, though the history may influence the choice or duration of prophylaxis. Mild dehydration is not a contraindication to pharmacologic prophylaxis; it may affect overall fluid management, but it does not by itself prevent use of anticoagulants.