Prophylaxis with heparin is indicated for which of the following conditions?

Heparin is an anticoagulant commonly used for prophylaxis against thromboembolic events, particularly in patients at increased risk of venous thromboembolism (VTE). Major surgery significantly elevates the risk of VTE due to factors like prolonged immobility and the surgical trauma itself, which can lead to a hypercoagulable state.

In the context of major surgery, it is especially important to implement prophylactic measures to reduce the risk of deep vein thrombosis (DVT) and pulmonary embolism (PE), both of which can have serious consequences. Heparin, as a form of pharmacologic prophylaxis, is often administered to patients undergoing major surgical procedures, especially orthopedic, abdominal, or pelvic surgeries, where the risk is particularly high.

On the other hand, conditions like chronic bronchitis, asthma exacerbations, and pneumonia do not typically present the same risk level for thromboembolic events as major surgery. Therefore, heparin prophylaxis is not routinely indicated for these conditions. The focus in respiratory diseases usually involves managing airflow obstruction and infection rather than preventing coagulation complications.