EpistemisEphedrine, Phenylephrine and Atropine
Perioperative vasoactive drugs are essential, fast-acting agents designed to maintain perfusion of vital organs in the face of cardiovascular alterations secondary to general or regional anesthetic techniques.
Mechanism
Mechanism of action and cardiovascular differentiation
Ephedrine: It is a sympathomimetic amine that acts through a double mechanism of direct adrenergic stimulation of α and β receptors and indirect stimulation through the induction of the physiological release of endogenous norepinephrine stored in the presynaptic vesicles of adrenergic autonomic neurons. It raises systolic blood pressure in a coordinated manner with a concomitant increase in cardiac output and heart rate.
Phenylephrine: It is a pure and highly selective agonist of postsynaptic α1 adrenergic receptors, inducing immediate generalized systemic vasoconstriction with an increase in systemic vascular resistance (SVR) and a concomitant increase in systolic blood pressure, accompanied by compensatory vagal reflex sinus bradycardia, very useful for hemodynamic control in patients with severe mitral stenosis or chronic aortic stenosis.
Atropine: It is a classic competitive antagonist of peripheral and central muscarinic cholinergic receptors (M1, M2, M3). Increases heart rate by blocking chronic vagal stimulation on the sinoatrial node (SAN), immediately accelerating the conduction potential in the atrioventricular node (AVN).
⚡ Ephedrine
- Indication of choice: Arterial hypotension associated with epidural or spinal block in the obstetric patient (optimally preserves the blood flow of the uterine artery without inducing significant fetal metabolic acidosis).
- It presents a phenomenon of rapid tachyphylaxis due to the progressive depletion of presynaptic reserves of cellular norepinephrine.
🎯 Phenylephrine
- Indication of choice: Management of acute systemic vasodilation induced by general anesthetic agents or sympathetic neuraxial blocks in patients with preserved heart rate reserve or associated supraventricular tachycardias.
- Does not increase direct myocardial contractility, secondary decreasing oxygen consumption of the myocardial wall.
Indicators and dose
Dosage and Crisis Management
- Ephedrine (IV rescue bolus): 5 - 10 mg slow intravenous, repeatable every 5-10 minutes according to tonic hemodynamic response.
- Phenylephrine (IV rescue bolus): 50 - 100 µg slow intravenous, or maintenance infusion adjusted to response at doses of 0.15 - 1.5 µg/kg/min.
- Atropine (Treatment of Symptomatic Bradyarrhythmia): 0.5 - 1.0 mg direct IV, repeatable up to a maximum total cumulative dose of 3.0 mg in adults.
Epistemis is educational review material. It is not a medical device, does not diagnose or prescribe treatment, and does not replace formal medical training, current clinical guidelines, or professional clinical judgment.
- System
- Anesthesiology
- Cluster
- Perioperative Hemodynamic Support