Which agent is primarily used in cardiopulmonary bypass to prevent clot formation?

Heparin is primarily used in cardiopulmonary bypass to prevent clot formation because it is an effective anticoagulant that works by inhibiting thrombin and factor Xa, which are crucial components in the coagulation cascade. When patients undergo cardiopulmonary bypass, the blood is exposed to artificial surfaces of the bypass circuit, which can activate the coagulation system and lead to clot formation. Heparin helps to prevent this by maintaining a state of anticoagulation during the procedure.

Its rapid onset and short duration of action also make it particularly suitable for this context, allowing for quick adjustments based on the patient's needs. Heparin can be monitored with activated clotting time (ACT) to ensure adequate anticoagulation while minimizing the risk of excessive bleeding. Other anticoagulants, such as warfarin, are not used in this setting due to their long duration of action and need for more careful management, while medications like aspirin and clopidogrel primarily work through platelet inhibition and are not adequate for the intensive anticoagulation required during bypass surgery.