Epinephrine, commonly known as adrenaline, is a naturally occurring hormone and a potent medication used in severe medical emergencies. This drug is a catecholamine, playing a significant role in the body’s stress response. In a medical setting, a “code” refers to cardiac arrest—a sudden loss of heart function, breathing, and consciousness. Standardized protocols, such as those published by the American Heart Association (AHA), govern the precise use of epinephrine during these life-threatening events.
The Role of Epinephrine in Cardiac Arrest
The primary function of epinephrine during cardiac arrest is to act as a vasoconstrictor, narrowing blood vessels by stimulating alpha-adrenergic receptors. This widespread constriction of peripheral vessels diverts blood flow to the body’s most vital organs.
By shunting blood to the central circulation, epinephrine increases pressure in the arteries supplying the heart and brain. This improvement in coronary and cerebral perfusion pressure is the main benefit during cardiopulmonary resuscitation (CPR). Maintaining adequate blood flow increases the chances of achieving Return of Spontaneous Circulation (ROSC).
Epinephrine also stimulates beta-adrenergic receptors, which can increase heart rate and the force of contraction. While these effects are beneficial in other clinical contexts, the alpha-receptor-mediated vasoconstriction remains the most important action in a pulseless patient.
Standard Adult Dosage and Concentration
The standard dose of epinephrine administered to an adult during cardiac arrest is fixed at 1 milligram (mg). This dosage is given as a rapid push into the circulatory system and is repeated according to established protocols throughout the resuscitation attempt.
The concentration of the solution is important for patient safety, as epinephrine comes in different strengths. The concentration used in cardiac arrest is a 1:10,000 solution, which contains 0.1 mg of epinephrine per milliliter (mL). Therefore, the 1 mg dose is delivered as 10 mL of the 1:10,000 solution.
Using the 1:10,000 concentration prevents accidentally administering a dangerously high dose. A more concentrated 1:1,000 solution is used for intramuscular injection in conditions like anaphylaxis, where 1 mg is contained in only 1 mL. The preferred route of administration is either through an intravenous (IV) line or an intraosseous (IO) line, which involves injecting the medication directly into the bone marrow when IV access is not possible.
Timing and Repetition of Administration
The 1 mg dose is repeated based on a precise schedule dictated by the resuscitation algorithm. The standard interval for repeating the epinephrine dose is every three to five minutes throughout the resuscitation effort. This repetition maintains sufficient drug levels to sustain the vasoconstrictive effects.
The initial timing of the first dose varies depending on the patient’s electrical rhythm.
Non-Shockable Rhythms
If the patient presents with a non-shockable rhythm, such as asystole (flatline) or Pulseless Electrical Activity (PEA), the first dose should be administered as soon as feasible. Earlier administration in these rhythms is associated with better outcomes.
Shockable Rhythms
If the patient has a shockable rhythm, specifically Ventricular Fibrillation (VF) or pulseless Ventricular Tachycardia (pVT), the protocol prioritizes electrical therapy first. The first dose of epinephrine is typically delayed and given after the second unsuccessful attempt at defibrillation. Subsequent doses are repeated every three to five minutes until the patient achieves a pulse or the resuscitation attempt is concluded.