8.4 ACLS Emergency Drug Reference & Administration Routes

Vascular Access Routes & Pharmacokinetics in Resuscitation

Rapid and reliable administration of emergency resuscitation medications is a foundational pillar of Advanced Cardiovascular Life Support (ACLS). The chosen route of administration governs drug pharmacokinetics, determining the peak blood concentration and the time required for medication to reach target cardiovascular receptors.

1. Peripheral Intravenous (IV) Access

Peripheral IV placement (typically in the antecubital vein) is the standard initial access route. However, during cardiac arrest, severe peripheral vasoconstriction and collapsed circulatory pressures cause pronounced venous stasis, significantly delaying drug transit from peripheral limbs to the heart.

• The Mandatory Flush Protocol: To overcome venous stasis, every IV push medication administered during cardiac arrest must be immediately followed by a rapid bolus of 20 mL of normal saline (0.9% NaCl).
• Limb Elevation: Following the saline flush, the provider must elevate the extremity above the level of the heart for 10 to 20 seconds to utilize gravity to rapidly wash the drug bolus into central venous circulation.

2. Intraosseous (IO) Access

If peripheral IV access cannot be established within 90 seconds or after two attempts during a cardiac arrest, healthcare providers must establish Intraosseous (IO) access without delay. IO cannulation utilizes a powered drill or manual needle to penetrate the rigid cortical bone, placing the catheter tip directly into the rich, non-collapsible venous plexus of the bone marrow cavity.

• Anatomic Insertion Sites: Primary sites include the Proximal Tibia (approximately 2 cm medial to the tibial tuberosity), the Humeral Head (greater tubercle of the humerus, which provides faster central flow and higher flow rates), and the Distal Tibia (flat inner surface 2 cm proximal to the medial malleolus).
• Pharmacokinetics and Safety: Because marrow sinusoids drain directly into the central circulation, drug onset and peak serum concentrations via IO access are virtually identical to central venous catheterization. All ACLS medications, vasopressors, antiarrhythmics, bolus fluids, and blood products can be safely administered via IO. Note that fluid boluses require a pressure bag or syringe push to overcome intraosseous resistance.

3. Endotracheal (ET) Route (Last Resort)

When neither IV nor IO access can be obtained, specific ACLS drugs may be administered directly down the endotracheal tube as a temporary last resort. Pulmonary mucosal absorption is erratic, unpredictable, and results in lower peak drug levels.

• Eligible Medications (NAVEL Mnemonic): Only specific drugs can be given endotracheally: Naloxone, Atropine, Vasopressin/Epinephrine, and Lidocaine.
• Dosing and Administration Protocol: Because absorption across alveoli is poor, the endotracheal dose must be increased to 2 to 2.5 times the standard IV dose. The drug must be diluted in 5 to 10 mL of sterile water or normal saline, injected directly into the ETT using a long catheter past the tip of the tube, and immediately followed by 5 to 10 rapid manual ventilations to disperse the medication into the distal bronchial tree.

Core Vasopressors & Antiarrhythmics in Cardiac Arrest

Emergency pharmacology during cardiac arrest focuses on restoring cerebral and coronary perfusion while treating life-threatening ventricular arrhythmias.

Epinephrine (Vasopressor of Choice)

Epinephrine is a non-selective alpha-1, beta-1, and beta-2 adrenergic agonist. Its therapeutic primary mechanism in cardiac arrest is mediated by alpha-1 receptor stimulation, which causes intense systemic arterial and venous vasoconstriction. This vasoconstriction increases systemic vascular resistance, raising aortic diastolic pressure and driving Coronary Perfusion Pressure (CPP) and cerebral perfusion pressure during chest compressions.

• Indications: All cardiac arrest rhythms: Ventricular Fibrillation (VF), Pulseless Ventricular Tachycardia (pVT), Asystole, and Pulseless Electrical Activity (PEA).
• Dosing and Timing: Administer 1 mg IV/IO (10 mL of 1:10,000 solution) every 3 to 5 minutes.
  • Non-Shockable Rhythms (Asystole/PEA): Administer epinephrine as soon as possible after cardiac arrest recognition.
  • Shockable Rhythms (VF/pVT): Administer epinephrine after the second defibrillation shock has failed.

Amiodarone (Primary Antiarrhythmic)

Amiodarone is a Class III antiarrhythmic agent that prolongs action potential duration and refractory periods while exhibiting Class I (sodium channel), Class II (beta-blocker), and Class IV (calcium channel) properties.

• Indications: Refractory VF or pulseless VT that persists despite high-quality CPR, defibrillation shocks, and vasopressor administration.
• Dosing Schedule:
  • First Bolus: 300 mg IV/IO push, administered after the third shock.
  • Second Bolus: 150 mg IV/IO push, administered after the fifth shock if VF/pVT persists.
• Post-ROSC Maintenance: If ROSC is achieved following Amiodarone administration, initiate a continuous maintenance IV infusion of 1 mg/min for 6 hours, followed by 0.5 mg/min for 18 hours (maximum 2.2 g in 24 hours).

Lidocaine (Alternative Antiarrhythmic)

Lidocaine is a Class Ib antiarrhythmic and sodium channel blocker that suppresses ventricular automaticity and raises the ventricular fibrillation threshold.

• Indications: Alternative to Amiodarone for refractory VF/pVT in pulseless arrest.
• Dosing Schedule:
  • First Bolus: 1.0 to 1.5 mg/kg IV/IO push (typically 75 to 100 mg for an adult).
  • Second/Subsequent Boluses: 0.5 to 0.75 mg/kg IV/IO every 5 to 10 minutes, up to a maximum cumulative dose of 3.0 mg/kg.
• Post-ROSC Maintenance: Continuous IV infusion of 1 to 4 mg/min.

Medications for Bradycardia, Tachycardia & Special Resuscitation Indications

ACLS algorithms incorporate targeted medications for symptomatic bradycardia, stable tachycardias, and metabolic derangements.

Atropine Sulfate

Atropine is a competitive parasympatholytic (anticholinergic) agent that blocks muscarinic acetylcholine receptors, blunting vagal tone and accelerating SA node automaticity and AV nodal conduction.

• Indications: First-line pharmacological treatment for symptomatic sinus bradycardia, first-degree AV block, and Mobitz Type I (Wenckebach) second-degree AV block.
• Dosing: Administer 1 mg IV/IO push every 3 to 5 minutes, up to a maximum cumulative dose of 3 mg.
• Clinical Caution: Atropine is ineffective for Mobitz Type II second-degree AV block and Third-Degree (Complete) Heart Block with wide QRS complexes because these infranodal blocks lack parasympathetic innervation. For these high-grade blocks, transcutaneous pacing or continuous infusions of dopamine or epinephrine are indicated.

Adenosine

Adenosine is an endogenous purinergic nucleoside that transiently slows conduction through the AV node by activating A1 adenosine receptors, interrupting re-entry pathways involving the AV node.

• Indications: First-line medication for stable narrow-complex Supraventricular Tachycardia (SVT) including AV nodal re-entrant tachycardia (AVNRT).
• Dosing & Slam Technique:
  • First Dose: 6 mg rapid IV push through a proximal vein (antecubital), followed IMMEDIATELY by a rapid 20 mL normal saline flush.
  • Second Dose: If SVT does not convert within 1 to 2 minutes, administer 12 mg rapid IV push followed by a 20 mL flush.
• Half-Life: Adenosine has an extremely short half-life (<10 seconds in blood). It must be pushed as rapidly as possible (over 1–2 seconds) using a two-syringe technique or three-way stopcock.

Magnesium Sulfate

Magnesium acts as a cofactor in the Na+/K+-ATPase pump and regulates calcium channels in myocardial cells.

• Indications: Treatment of choice for Torsades de Pointes (polymorphic VT associated with a prolonged QT interval) and severe hypomagnesemia.
• Dosing: Administer 1 to 2 grams IV/IO diluted in 10 mL D5W pushed over 5 to 20 minutes (or rapid IV push during pulseless Torsades).

Comprehensive ACLS Emergency Drug Reference Table

The following reference table summarizes key ACLS emergency medications, their mechanisms of action, standard dosing protocols, and critical clinical notes.