Adrenaline Autoinjector - Amplified

Quick Reference

Dosing by Weight

IM Adrenaline (Manual Draw-Up)

Using 1:1000 (1mg/mL) solution:

• Child: 10 mcg/kg IM (max 300 mcg)
• Adult: 500 mcg IM (0.5 mL)

Recognition of Anaphylaxis

Anaphylaxis is defined by sudden onset with multi-system involvement. A simple allergic reaction (e.g., localised hives) is NOT anaphylaxis - but can progress to it.

Airway: swelling, stridor, hoarse voice

Laryngeal oedema causes stridor (high-pitched inspiratory noise), voice changes, and a sensation of throat tightening. This is immediately life-threatening - obstruction can develop within minutes.

Breathing: wheeze, increased work of breathing

Bronchospasm causes wheeze and increased respiratory effort. Unlike asthma, anaphylaxis-related wheeze may not respond well to salbutamol alone - it needs adrenaline.

Circulation: tachycardia, hypotension, pale

Histamine-mediated vasodilation and capillary leak cause distributive shock. Signs: fast heart rate, weak pulse, low BP, prolonged cap refill, pallor, dizziness, and eventually collapse.

Skin: urticaria, angioedema, flushing

Present in ~90% of cases but NOT required for diagnosis. Urticaria (hives) are raised, itchy wheals. Angioedema is deeper swelling of lips, tongue, eyelids. Skin signs alone = allergic reaction, not anaphylaxis.

Prep

Confirm anaphylaxis (not just allergy)

Before giving adrenaline, confirm this is anaphylaxis:

• Sudden onset after known/likely trigger
• Involves at least TWO systems (e.g., skin + breathing, or skin + circulation)
• OR severe respiratory or cardiovascular compromise alone after likely allergen

Don't delay for perfect certainty - if in doubt, give adrenaline. It's safe IM.

Retrieve correct autoinjector for weight

Check the patient's weight and select the appropriate device. For children 20-50 kg, either EpiPen Jr (150 mcg) or adult EpiPen (300 mcg) can be used - 300 mcg is increasingly preferred.

Remove safety cap

EpiPen: Remove the blue safety cap (keeps it simple - "blue to the sky, orange to the thigh") Anapen: Remove the black needle cap

Device Selection

If no autoinjector available, draw up adrenaline from ampoule (1:1000 solution, 10 mcg/kg IM for children, 500 mcg IM for adults).

Execute

Site: Outer mid-thigh

Inject into the anterolateral thigh (vastus lateralis muscle). This location:

• Has good muscle mass for IM absorption
• Is accessible even through clothing
• Avoids major nerves and vessels

Can inject through clothing if needed - don't delay to undress.

Avoid: buttock (sciatic nerve risk, poor absorption), deltoid (smaller muscle), IV route (risk of arrhythmia)

Technique

EpiPen:

1. Remove blue safety cap
2. Hold with orange tip pointing down
3. Jab firmly into outer mid-thigh at 90° angle
4. You'll hear a click when it fires
5. Hold in place for 10 seconds
6. Remove - window will show red if dose delivered
7. Massage injection site for 10 seconds

Anapen:

1. Remove black needle cap
2. Place needle end against outer thigh
3. Press grey button firmly - it fires automatically
4. Hold for 10 seconds
5. Remove and check needle has extended

Finish

Call 000 if not already done

All anaphylaxis needs emergency services, even if responding to adrenaline. Biphasic reactions can occur hours later. Ambulance can provide monitoring and IV access.

Position: lay flat, elevate legs

Position the patient supine with legs elevated to optimise venous return and blood pressure. Exception: if severe respiratory distress, allow to sit up (prioritise breathing). If vomiting, recovery position.

Do not let them stand up - sudden standing in anaphylaxis can cause cardiac arrest.

Repeat in 5 min if no improvement

If symptoms persist or worsen after 5 minutes, give a second dose. Many cases of fatal anaphylaxis involve delayed or inadequate adrenaline dosing. You can repeat every 5 minutes as needed.

Monitor continuously - biphasic reactions occur

Anaphylaxis can recur 4-12 hours after the initial episode (biphasic reaction). All patients need minimum 4 hours observation in a monitored setting. Severe reactions may need overnight admission.

Pharmacology

Why Adrenaline Works

Adrenaline reverses every pathophysiological feature of anaphylaxis:

• α1 effects: vasoconstriction → raises BP, reduces oedema
• β1 effects: increases heart rate and contractility → improves cardiac output
• β2 effects: bronchodilation → relieves wheeze; also stabilises mast cells to reduce further histamine release

Why IM Not IV?

IV adrenaline in anaphylaxis risks fatal arrhythmias. IM into the thigh provides rapid absorption (peak levels in 8-10 minutes) and is much safer. IV adrenaline is reserved for cardiac arrest or refractory shock under expert guidance.