Adrenaline Dosing for Anaphylactic Shock
Primary Recommendation
For anaphylactic shock, administer intramuscular (IM) epinephrine 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) into the anterolateral thigh as first-line treatment; if intravenous access is already established and the patient remains profoundly hypotensive, give IV epinephrine 0.05-0.1 mg (0.5-1 mL of 1:10,000 solution) slowly, with continuous hemodynamic monitoring. 1, 2, 3
Route Selection Algorithm
First-Line: Intramuscular Administration
- IM epinephrine is the preferred initial route due to ease of administration, rapid peak plasma concentrations, effectiveness, and superior safety profile compared to IV administration 1, 2, 4
- Inject into the anterolateral aspect of the mid-thigh, never into buttocks, digits, hands, or feet 3
- Adult dose: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 concentration) 1, 3
- Pediatric dosing:
When to Use Intravenous Route
Consider IV epinephrine only when: 2
- IV access is already in place, AND
- Patient has cardiac arrest from anaphylaxis, OR
- Profound hypotension persists despite IV fluids and IM epinephrine, OR
- Patient fails to respond to several IM doses
IV Bolus Dosing
- Initial IV dose: 0.05-0.1 mg (0.5-1 mL of 1:10,000 concentration), which represents 5-10% of the cardiac arrest dose 1, 2
- Administer slowly over several minutes to minimize adverse cardiovascular effects 2
- Adult dose from anaesthesia guidelines: 50 mcg (0.5 mL of 1:10,000) initially, with additional doses as needed for severe hypotension or bronchospasm 1
- Pediatric IV dosing: 1 mcg/kg initially, titrating to response (prepare 1 mL of 1:10,000 per 10 kg body weight) 1
Repeat Dosing
- Repeat IM doses every 5-10 minutes as necessary if symptoms persist or recur 3
- Recurrence of symptoms after 5-15 minutes is commonly reported, with 8-28% of patients requiring two or more doses 5
- If multiple doses are required, transition to continuous IV infusion rather than repeated boluses 1, 2
Continuous Infusion Protocol
When to Initiate
- Consider infusion when shock recurs after initial treatment or multiple bolus doses are needed 1, 2
- Infusion allows for careful titration and avoidance of epinephrine overdose 2
Preparation Methods
Two acceptable concentrations: 2
- Add 1 mg (1 mL of 1:1000) to 250 mL D5W = 4 mcg/mL concentration
- Add 1 mg (1 mL of 1:1000) to 100 mL saline = 10 mcg/mL concentration
Infusion Rate
- Start at 5-15 mcg/min and titrate to hemodynamic response 1, 2
- Alternative dosing: 0.05-0.1 mcg/kg/min, titrating every 5-15 minutes to achieve mean arterial pressure ≥65 mmHg 6
Critical Monitoring Requirements
For IV Administration
- Continuous hemodynamic monitoring is mandatory when administering IV epinephrine 2
- In settings without advanced monitoring: every-minute blood pressure measurements, continuous pulse monitoring, and ECG monitoring 2
- Monitor for adverse effects: tachyarrhythmias, hypertension, potentially lethal arrhythmias, and extravasation injury 2
General Monitoring
- Cardiovascular and respiratory status can change rapidly, making close monitoring imperative 1
- Assess tissue perfusion markers: lactate clearance, urine output, mental status, and capillary refill 6
Adjunctive Therapies (Secondary Management)
After epinephrine administration: 1
- High-rate IV fluid resuscitation with 0.9% saline or lactated Ringer's solution (large volumes may be required)
- Chlorphenamine 10 mg IV (adult dose)
- Hydrocortisone 200 mg IV (adult dose)
- For persistent bronchospasm: IV salbutamol infusion, metered-dose inhaler, or consider aminophylline/magnesium sulfate 1
Refractory Cases
- For patients on β-blockers: consider glucagon 1-5 mg IV over 5 minutes followed by infusion 2
- For refractory hypotension despite epinephrine: consider alternative vasopressors such as dopamine 2-20 mcg/kg/min or metaraminol 1, 2
Common Pitfalls and How to Avoid Them
Concentration Confusion (Life-Threatening Error)
- Never confuse 1:1000 (IM) with 1:10,000 (IV) concentrations 7
- Giving cardiac arrest dose (1 mg IV push) instead of anaphylaxis dose (0.05-0.1 mg IV) causes iatrogenic overdose with potentially lethal cardiac complications including severe systolic dysfunction 7
- Solution: Stock prefilled, clearly labeled IM epinephrine syringes (0.3-0.5 mg) in crash carts that are visually distinct from IV cardiac arrest syringes 7
Delayed Administration
- Failure to inject epinephrine promptly contributes to anaphylaxis fatalities 4
- Epinephrine is most effective when given immediately after symptom onset 4
- Do not delay epinephrine while focusing on second-line treatments (antihistamines, steroids) 2
Route Selection Errors
- Subcutaneous injection has delayed onset of action compared to IM 4
- IV administration without proper dilution and slow infusion increases risk of adverse cardiovascular effects 2, 7
- Injection into buttocks, digits, hands, or feet can cause tissue injury 3
Inadequate Dosing
- Only 16.8% of junior doctors in one survey would administer epinephrine correctly per guidelines, with widespread confusion about dose and route 8
- Standard resuscitative measures and immediate epinephrine administration should take priority in cardiac arrest from anaphylaxis 1
Special Populations
Drug Interactions
- Sympathomimetic agents: possible additive effects 3
- Beta-blockers: antagonize cardiostimulating and bronchodilating effects; consider glucagon 2, 3
- Tricyclic antidepressants, MAO inhibitors: potentiate epinephrine effects 3
- Alpha-blockers: antagonize vasoconstricting effects 3
High-Risk Patients
- Patients with underlying heart disease may develop angina or ventricular arrhythmias with IM/SC administration 3
- Hyperthyroidism, Parkinson's disease, diabetes, pheochromocytoma: greater risk of adverse reactions 3
- Elderly and pregnant patients: may be at greater risk of adverse reactions with parenteral epinephrine 3
- Sulfite presence in formulation should not deter use for anaphylaxis 3