Epinephrine, also known as adrenaline, is a powerful vasopressor medication used during cardiopulmonary resuscitation (CPR) in an emergency setting known as a “code.” It works to narrow blood vessels and increase blood pressure. Epinephrine is a standard component of Advanced Cardiac Life Support (ACLS) protocols and is administered for all non-perfusing cardiac rhythms, including asystole and pulseless electrical activity (PEA). The timing of administration is carefully regulated to maximize the drug’s potential to improve the chances of a return of spontaneous circulation (ROSC).
Understanding the Standard Dose and Concentration
The quantity of epinephrine used in cardiac arrest is highly standardized for safety and effectiveness. The established adult dose for intravenous (IV) or intraosseous (IO) administration is 1 milligram (mg). This dose is repeated at intervals of every three to five minutes for the duration of the resuscitation attempt, following current guidelines.
The concentration is important for avoiding dangerous medication errors. For IV or IO administration, epinephrine is prepared at a 1:10,000 concentration, which equates to 0.1 mg per milliliter (mL). The standard 1 mg dose is typically delivered in a syringe containing 10 mL of solution.
The 1:10,000 concentration used in a code differs significantly from the 1:1,000 concentration used for intramuscular injections, such as for anaphylaxis. Using the wrong concentration intravenously could lead to an accidental ten-fold overdose. Therefore, precise medication identification is emphasized during resuscitation.
The Critical Administration Technique and Speed
Epinephrine must be delivered as a rapid intravenous push, also referred to as a bolus. This technique is necessary to ensure the drug reaches the heart and major blood vessels quickly. The goal is to achieve a peak plasma concentration almost instantaneously, which is necessary when the patient’s heart is not pumping blood effectively.
Immediate mechanical steps must follow the rapid push to ensure the drug is circulated from the peripheral IV site to the central circulation. Current protocols require that the dose be followed immediately by a rapid flush of at least 20 mL of a compatible IV fluid, such as normal saline. If the drug is delivered through a peripheral arm vein, the extremity is often elevated for 10 to 20 seconds to assist gravity in moving the medication toward the core.
This rapid push and immediate flush are a standard requirement for medications given peripherally during a cardiac arrest. Since blood flow is severely impaired or non-existent, the mechanical force of the flush is required to propel the medication through the veins. Following the administration sequence, chest compressions must resume immediately to circulate the drug throughout the body.
Why Rapid Delivery is Essential in Cardiac Arrest
The need for a rapid push is rooted in the physiological consequences of circulatory arrest and the drug’s mechanism of action. Epinephrine works primarily through powerful alpha-adrenergic effects, which cause intense constriction of the peripheral blood vessels. This widespread vasoconstriction is the main therapeutic goal because it increases the diastolic blood pressure.
During CPR, the diastolic blood pressure is the primary factor that determines Coronary Perfusion Pressure (CPP). CPP is the pressure gradient driving blood flow to the heart muscle itself. The heart cannot be successfully restarted unless the CPP is maintained above a certain threshold, typically cited as 15 to 20 mmHg. A rapid bolus of epinephrine is necessary to quickly raise the CPP to this level.
The rapid push technique maximizes the beneficial alpha-adrenergic effects. While the alpha effects are helpful, the drug also has beta-adrenergic effects that can increase the heart’s oxygen demand and irritability. Administering the drug quickly ensures beneficial vasoconstriction is achieved immediately, improving the likelihood of a Return of Spontaneous Circulation (ROSC). This effect is often short-lived, with peak blood pressure augmentation occurring within two minutes of administration.