Anaphylaxis Treatment with IM Adrenaline
Dosing and Administration
- The recommended dose of intramuscular (IM) adrenaline for anaphylaxis treatment is 0.01 mg/kg of 1:1000 concentration, up to a maximum of 0.5 mg for adults and 0.3 mg for children, administered in the anterolateral thigh (vastus lateralis muscle) 1
- For autoinjectors in children: 0.15 mg dose for children weighing 10-25 kg and 0.3 mg dose for children weighing ≥25 kg 2, 3
- Intramuscular injection in the lateral thigh leads to faster absorption compared to subcutaneous injection (peak plasma concentration at 8±2 minutes vs. 34±14 minutes) 3, 4
Important Clinical Considerations
- No absolute contraindications exist for using epinephrine to treat anaphylaxis, even in patients with cardiac disease, advanced age, or frailty 1
- Delay in administering epinephrine has been associated with anaphylaxis fatalities and increased risk of biphasic reactions 1
- Patients requiring more than one dose of epinephrine have higher risk of biphasic reactions 1, 5
Special Situations
- For severe, refractory anaphylaxis unresponsive to IM epinephrine, IV epinephrine infusion may be considered at 1-4 mcg/min, titrated up to a maximum of 10 mcg/min 6
- Biphasic reactions may occur up to 72 hours later, with a mean of 11 hours 1
Common Pitfalls to Avoid
- Delaying epinephrine administration while giving antihistamines or corticosteroids first - epinephrine is the first-line treatment 5
- Using subcutaneous instead of intramuscular route, which delays absorption 3, 4
- Underdosing in adults or overdosing in small children due to fixed-dose autoinjectors 3, 4
Weight Threshold for Switching from Junior to Adult EpiPen
Dosing Recommendations
- The recommended dose of epinephrine for anaphylaxis is 0.01 mg/kg up to a maximum of 0.30 mg, according to the American Academy of Pediatrics 7, 8
- Children should switch from the junior EpiPen (0.15 mg) to the adult version (0.30 mg) at approximately 25 kg (55 lbs), as recommended by the American Academy of Pediatrics 9
Clinical Rationale for the 25 kg Threshold
- At 25 kg, the 0.15 mg junior dose would provide only 0.006 mg/kg, which is considered an underdose, according to the American Academy of Pediatrics 9
- The 0.30 mg adult dose at 25 kg provides 0.012 mg/kg, which is a slight overdose but preferable to underdosing during anaphylaxis, as stated by the American Academy of Pediatrics 9
Special Considerations
- For children with asthma or other risk factors for fatal anaphylaxis, switching to the higher dose at a lower weight might be considered, according to the American Academy of Pediatrics 9
- The therapeutic effects of epinephrine cannot be dissociated from its adverse effects, which include pallor, tremor, anxiety, palpitations, headache, and nausea, as reported by the American Academy of Pediatrics 7
Potential Risks to Consider
- Using an ampule/syringe/needle instead of an autoinjector is not recommended due to significant delays and dosing inaccuracies, as found by the American Academy of Pediatrics 7, 9
- The American Heart Association and American Red Cross guidelines emphasize that prompt administration of epinephrine is critical for preventing mortality in anaphylaxis 10, 11
Intramuscular Adrenaline Administration
Rationale for 90-Degree Angle
- The American Heart Association recommends intramuscular adrenaline 1:1000 0.5ml should be administered at a 90-degree angle into the anterolateral thigh for optimal absorption and rapid onset of action 12, 13, 14
- The intramuscular route requires perpendicular needle insertion to ensure the medication reaches the muscle tissue rather than subcutaneous fat, which is critical for optimal absorption and rapid onset of action 12, 13
- The vastus lateralis muscle in the anterolateral thigh is the preferred site because intramuscular injection at this location produces rapid peak plasma epinephrine concentrations compared to subcutaneous injection 12
Proper Injection Technique
- The American Academy of Pediatrics recommends inserting the needle perpendicular to the skin surface in the mid-outer aspect of the thigh (anterolateral region) 12, 13, 15
- The injection can be given through clothing if necessary during emergency situations, as delay in administration is associated with increased mortality 14
- Use a needle length appropriate for the patient's body habitus to ensure intramuscular delivery - typically 22-25mm for adults 13
Critical Pitfalls to Avoid
- The American Heart Association recommends avoiding the deltoid muscle for initial anaphylaxis treatment, as the anterolateral thigh provides superior and more consistent absorption 12, 13
- Do not delay administration to achieve "perfect" technique - prompt intramuscular injection at 90 degrees into the thigh is more important than technical perfection, as delayed epinephrine has been associated with anaphylaxis fatalities 14
- The dose may be repeated every 5-15 minutes if there is inadequate response, using the same 90-degree intramuscular technique 12, 13, 15
Epinephrine Administration in Anaphylaxis
Dosing and Administration
- The American Academy of Allergy, Asthma, and Immunology recommends repeat dosing of epinephrine every 5-15 minutes if symptoms persist or recur, with the option to liberalize the interval for more frequent injections as clinically needed 16
- For severe, refractory anaphylaxis, an initial infusion of 1 mg (1 mL of 1:1000) epinephrine in 250 mL D5W, yielding a 4 μg/mL concentration, can be administered, with an infusion rate of 1-4 μg/min (15-60 drops/min with microdrop apparatus), titrating up to a maximum of 10 μg/min 16
Intravenous Epinephrine Protocol
- The American Academy of Allergy, Asthma, and Immunology suggests an alternative protocol of 1:100,000 solution (1 mg in 100 mL saline) at 30-100 mL/h (5-15 μg/min), titrated based on clinical response 16
- For children, the "Rule of 6" alternative can be used, where 0.6 × body weight (kg) = mg diluted to 100 mL saline, and then 1 mL/h delivers 0.1 μg/kg/min 16