**Question:** In the management of pulmonary emboli, alteplase (-PA) is infused for:

**Core Concept:** Pulmonary embolism (PE) is a serious medical emergency caused by the blockage of pulmonary arteries by a blood clot. Alteplase, also known as tissue plasminogen activator (tPA), is a thrombolytic agent that acts as a fibrin-specific serine protease, breaking down fibrin within the blood clot.

**Why the Correct Answer is Right:** Alteplase is a specific fibrinolytic agent, meaning it breaks down fibrin, the primary component of blood clots. In the context of pulmonary emboli, its infusion helps to dissolve the blood clot and improve blood flow in the pulmonary arteries, thereby reducing the risk of complications such as right ventricular failure and death.

**Why Each Wrong Option is Incorrect:**

A. Pulmonary artery constriction: While pulmonary artery constriction may occur as a physiological response to PE, alteplase is not indicated for this purpose. The drug's primary function is to dissolve the blood clot, not constrict blood vessels.

B. Thrombocytopenia prevention: Alteplase does not prevent thrombocytopenia; it is a fibrinolytic agent that dissolves blood clots.

C. Anticoagulation: Alteplase is a fibrinolytic agent, not an anticoagulant. It helps dissolve the blood clot, not prevent clot formation or prolong coagulation time.

D. Reducing pulmonary artery pressure: While pulmonary artery pressure may decrease as the blood clot is dissolved, alteplase is primarily used for clot dissolution, not solely for reducing pressure.

**Clinical Pearl:** In cases of pulmonary emboli, the primary goal of alteplase administration is to dissolve the blood clot, restoring blood flow in the pulmonary arteries and reducing the risk of complications. This is crucial for the management of severe PE cases, as timely intervention can prevent right ventricular failure and other severe consequences of PE.