What Are the Effects of Epinephrine Injection?

If a patient is found to have no vital signs or limb responses, epinephrine injection will be administered. Sometimes, a heartbeat may appear after the injection of epinephrine. Epinephrine injection has the effects of epinephrine, acting on small arteries and precapillary sphincters, and stimulating the heart.

1. It acts on β1 receptors in the myocardium, conduction system, and sinoatrial node, enhancing myocardial contractility, accelerating conduction, increasing heart rate, and improving myocardial excitability. The β-effect on isolated myocardium is characterized by accelerated rates of contractile development. Due to increased myocardial contractility and accelerated heart rate, cardiac output increases. It also dilates coronary vessels, improves myocardial blood supply, and acts rapidly as a potent cardiac stimulant. However, its disadvantage is that it increases myocardial metabolism, leading to increased myocardial oxygen consumption, which can cause arrhythmias, premature contractions, and even ventricular fibrillation.

2. It acts on small arteries and precapillary sphincters. The effects of epinephrine on blood vessels in various parts of the body are inconsistent, with the most intense vasoconstriction occurring in the skin and mucosal vessels. Visceral vessels, especially renal vessels, also undergo significant vasoconstriction. The vasoconstrictive effects on the brain and pulmonary vessels are very weak and may sometimes be passively dilated due to increased blood pressure. The β2 receptors in skeletal muscle vessels predominate, resulting in vasodilation, and can also dilate coronary vessels.

3. As it stimulates the heart, increasing cardiac output, it raises systolic blood pressure and redistributes blood to various parts of the body, making it more suitable for meeting the energy supply needs of the body in emergency situations.

4. It can stimulate the β2 receptors of bronchial smooth muscle, exerting a powerful dilating effect. It can also inhibit the release of allergic substances such as histamine from mast cells, and can constrict bronchial mucosal vessels, reduce capillary permeability, and help eliminate bronchial mucosal edema.

1. It is contraindicated in patients with organic heart disease, hypertension, coronary artery disease, cardiogenic asthma, obstructive cardiomyopathy, arrhythmia, especially ventricular arrhythmia, hyperthyroidism, diabetes mellitus, brain tissue contusion, and parturition.

2. It should be used with caution in children, the elderly, patients with organic brain damage, and pregnant women.