Final answer:
Nitroglycerin is used sublingually for immediate cardiac relief in cases of stable and unstable angina as part of the medical directive for cardiac ischemia. It works as a vasodilator to improve blood flow and reduce tissue hypoxia. Its exact mechanism involves the release of nitric oxide but is not fully understood.
Step-by-step explanation:
Nitroglycerin, also known as glyceryl trinitrate, is a critical medication in the management of cardiac ischemia and myocardial infarction (MI). It is administered sublingually to rapidly absorb and exert its vasodilator effects. The main conditions for its use include the relief of chest pain associated with stable angina, which is usually triggered by exertion and alleviated by rest or nitroglycerin, and the more serious unstable angina, which occurs at rest and may signify an impending heart attack. In the case of cardiac ischemia, nitroglycerin aids in improving blood flow by relaxing the smooth muscles within the coronary vessels, thus reducing ischemia and hypoxia. Immediate treatments for MI also involve supplemental oxygen and aspirin, which helps to prevent clotting, thereby addressing the reduced oxygen supply to the cardiac tissues.
Furthermore, longer-term treatments such as thrombolytic agents (e.g., streptokinase), anticoagulants like heparin, and surgical interventions may follow, depending on the severity of the condition. While nitroglycerin has been used since the 1880s, the exact mechanism of action is still not completely understood, but it is believed to involve the release of nitric oxide, a known vasodilator.