Cardiovascular and Emergency Drugs in Anesthesia

Alpha-1 activation causes arterial and venous vasoconstriction. Presynaptic alpha-2 activation reduces norepinephrine release, while central alpha-2 activation reduces sympathetic outflow. Beta-1 activation increases heart rate, conduction, and contractility. Beta-2 activation relaxes bronchial and selected vascular smooth muscle and can drive potassium into cells.

Epinephrine activates alpha and beta receptors. It is used in cardiac arrest, anaphylaxis, and selected low-output states, but can cause tachyarrhythmia, myocardial ischemia, hyperglycemia, and lactic acidosis.

Norepinephrine has dominant alpha-1 activity with clinically important beta-1 activity. It raises systemic vascular resistance and is widely used for vasodilatory shock; extravasation can cause tissue ischemia.

Phenylephrine is a direct alpha-1 agonist that increases vascular tone and often causes reflex bradycardia. Ephedrine acts directly and indirectly, increasing norepinephrine release; repeated doses may show tachyphylaxis as stores are depleted.

Phentolamine is a nonselective alpha antagonist used for catecholamine-mediated hypertension and vasopressor extravasation. Labetalol blocks alpha-1 and beta receptors. Propranolol is a nonselective beta blocker, while esmolol is beta-1 selective and rapidly hydrolyzed, giving it a short duration.

• Beta blockade can worsen bradycardia, heart block, decompensated heart failure, or bronchospasm in susceptible patients.
• Alpha blockade before beta blockade is essential in catecholamine excess from pheochromocytoma to avoid unopposed vasoconstriction.
• Esmolol is useful when rapid titration and prompt offset are desired.

Nitroglycerin releases nitric oxide and predominantly dilates veins at lower doses, reducing preload. Headache, hypotension, tolerance, and methemoglobinemia with substantial exposure are recognized risks.

Sodium nitroprusside dilates arteries and veins through nitric oxide. Prolonged or high-dose exposure, especially with renal or hepatic dysfunction, increases risk from cyanide or thiocyanate accumulation. Hydralazine is a direct arteriolar vasodilator but is not classified as a nitric-oxide donor in the same way.

Verapamil is a nondihydropyridine calcium-channel blocker used for selected supraventricular tachyarrhythmias; it slows AV nodal conduction and can cause hypotension, bradycardia, or heart failure. Amiodarone has actions across several antiarrhythmic classes and can cause hypotension or bradycardia intravenously and thyroid, pulmonary, hepatic, ocular, and neurologic toxicity with chronic exposure.

High-quality CPR and defibrillation for shockable rhythms remain the priorities. In adult cardiac arrest, the standard epinephrine dose is 1 mg intravenously or intraosseously every 3 to 5 minutes. For refractory ventricular fibrillation or pulseless ventricular tachycardia, amiodarone or lidocaine may be considered.

Routine calcium, sodium bicarbonate, or magnesium is not recommended during undifferentiated adult cardiac arrest. Each may have a role in a defined special circumstance, such as torsades de pointes, hyperkalemia, or selected toxicologic emergencies.

Primary teaching source: Akram Amer, Pharmacology of Anesthesia Drugs, pages 35-45.

Cardiac-arrest content was aligned with the American Heart Association 2025 Adult Advanced Life Support guideline; drug-specific safety claims were checked against current prescribing information.

This material is educational and remains a draft until reviewed by a qualified clinician. Local protocols and current product information take precedence for patient care.