What are the indications, mechanisms, and dosages of adrenaline (epinephrine) in emergency situations?

Epinephrine (Adrenaline): Mechanism, Indications, and Dosage in Emergency Situations

Epinephrine is the cornerstone of treatment for anaphylaxis and cardiac arrest, with different dosing regimens based on the specific emergency situation. 1

Mechanism of Action

• Epinephrine is a non-selective alpha and beta adrenergic agonist that produces multiple physiological effects 2:
  • Alpha-adrenergic effects: Vasoconstriction, increased systemic vascular resistance, increased blood pressure 3
  • Beta-1 adrenergic effects: Increased heart rate, increased myocardial contractility 3
  • Beta-2 adrenergic effects: Bronchodilation, decreased mediator release from mast cells and basophils 4

Indications

1. Anaphylaxis

• Emergency treatment of allergic reactions (Type I), including anaphylaxis 2
• Signs and symptoms include: flushing, syncope, tachycardia, hypotension, airway swelling, laryngospasm, bronchospasm, urticaria, angioedema 2

2. Cardiac Arrest

• Standard resuscitative measure for all types of cardiac arrest 1
• Primary mechanism in cardiac arrest is alpha-adrenergic mediated increase in coronary perfusion pressure 3

Dosage and Administration

For Anaphylaxis:

1. Intramuscular Administration (Preferred Initial Route) 1, 5:

   • Adults and children ≥30 kg: 0.2-0.5 mg (1:1000) IM into anterolateral thigh 1, 2
   • Children <30 kg: 0.01 mg/kg (0.01 mL/kg) up to 0.3 mg IM 2
   • May repeat every 5-15 minutes as needed 1

2. Intravenous Administration (when IV access is established) 1:

   • Dose: 0.05-0.1 mg (1:10,000) IV 1
   • This is 5-10% of the dose used in cardiac arrest 1

3. Continuous IV Infusion 1:

   • Dose: 5-15 μg/min 1
   • Reasonable alternative to IV boluses for ongoing treatment 1
   • Allows for careful titration and avoidance of overdosing 1

For Cardiac Arrest:

• Higher doses are required compared to anaphylaxis 6
• Standard ACLS dosing applies 1
• Administer as soon as feasible in cardiac arrest with non-shockable rhythms 1
• For shockable rhythms, consider administering after initial defibrillation attempts have been unsuccessful 1

Special Considerations

• Monitoring: Close hemodynamic monitoring is essential in anaphylactic shock as cardiovascular and respiratory status can change rapidly 1

• Airway Management: When anaphylaxis produces obstructive airway edema, rapid advanced airway management is critical, potentially including surgical airway management 1

• Route of Administration: Intramuscular is the preferred initial route for anaphylaxis due to ease of administration, effectiveness, and safety 1, 4

• Medication Errors: Confusion between anaphylaxis dosing and cardiac arrest dosing has led to iatrogenic overdoses with potentially life-threatening complications 6

• Fluid Resuscitation: Important adjunct therapy in anaphylactic shock due to vasodilation and increased capillary permeability 5

Common Pitfalls and Caveats

• Dosing Errors: Ensure proper distinction between anaphylaxis dosing (lower) and cardiac arrest dosing (higher) 6

• Route Confusion: Do not inject epinephrine into buttocks, digits, hands, or feet as this may cause tissue damage 2

• Adverse Effects: Common adverse reactions include anxiety, restlessness, tremor, dizziness, sweating, palpitations, nausea, headache 2

• Cardiac Risks: May aggravate angina or produce ventricular arrhythmias, particularly in patients with underlying heart disease 2, 7

• Special Populations: Patients with hyperthyroidism, Parkinson's disease, diabetes, and pheochromocytoma are at greater risk of adverse reactions 2

• Drug Interactions: Be aware of interactions with sympathomimetics, cardiac glycosides, tricyclic antidepressants, MAO inhibitors, beta-blockers, and alpha-blockers 2