A client with a history of unstable angina presents to the emergency department with constant chest pressure that is unrelieved with rest. The client appears anxious, pale, and diaphoretic. After obtaining the client's vital signs, which action should the nurse take next?

A. Place an indwelling urinary catheter and institute strict intake and output measurements: Monitoring fluid balance is important in cardiac clients, but it is not the immediate priority during an acute chest pain episode suggestive of myocardial infarction. B. Evaluate upper and lower extremities for perfusion, pulse volume, and pitting edema: Assessing perfusion is relevant, but it is secondary to initiating urgent interventions aimed at reducing cardiac damage. C. Administer four 81 mg aspirin tablets providing instructions to chew before swallowing: Chewing aspirin promptly inhibits platelet aggregation, which is a critical first-line intervention in suspected acute coronary syndrome to reduce clot formation and limit myocardial injury. D. Secure client consent for coronary angiography and percutaneous coronary intervention: Consent may be needed later, but immediate medical stabilization, including aspirin administration, takes priority before diagnostic or interventional procedures.