Version 1.0 — Published April 2026
Quick Answer
Anaphylaxis is a severe, life-threatening, generalized hypersensitivity reaction with rapid onset, requiring immediate IM adrenaline. In an 8-year-old child with known peanut allergy who develops urticaria, stridor, vomiting and hypotension within 10 minutes of exposure, follow this 6-step protocol:
- Call for help and remove the trigger — discontinue any ongoing exposure
- IM adrenaline 0.01 mg/kg (1:1000) into anterolateral thigh — for a 25 kg child, 0.25 mg = 0.25 mL of 1:1000; max 0.3 mg in children <30 kg
- Position supine with legs elevated — never sit up (risk of empty-ventricle PEA arrest); position-of-comfort if airway compromise
- High-flow oxygen 15 L/min via non-rebreather + IV access × 2 — fluid bolus 20 mL/kg of normal saline if hypotensive
- Repeat IM adrenaline every 5-15 min if no improvement — second-line: IV antihistamines, IV hydrocortisone, nebulized salbutamol
- Observe for at least 4-6 hours (12-24 if high-risk) — discharge with two EpiPens, written action plan, allergist referral
The case
An 8-year-old boy is brought to the pediatric ED by his school teacher, 15 minutes after collapsing during the school lunch break. He has a known peanut allergy diagnosed at age 3 (after an episode of facial swelling) but has never had a severe reaction since the family removed peanuts from his diet. Today, he ate from a friend's lunchbox containing a "peanut chikki" (Indian peanut brittle) — within 5-10 minutes he developed an itchy rash on his arms and chest, started coughing, complained that his throat was "tight," vomited twice, and then became drowsy.
His teacher recognized the rash and brought him directly to the hospital. No EpiPen is available — the family had been prescribed one but had not refilled it.
On arrival, vitals are: pulse 152/min, BP 76/42 mmHg, respiratory rate 36/min with audible inspiratory stridor and expiratory wheeze, SpO2 88 percent on room air, temperature 36.6 C, capillary glucose 98 mg/dL. He is drowsy (GCS 12 — E3 V3 M6), with extensive urticarial wheals over the trunk, arms, and face, perioral and periorbital angioedema, and mild lip swelling. There is no drooling. Auscultation reveals bilateral wheeze and stridor heard over the larynx. Capillary refill 4 seconds, mottled extremities. Weight estimated 25 kg.
ABCD assessment
The diagnostic criteria for anaphylaxis (NIAID/FAAN 2020 update) are met if any ONE of three:
- Acute onset of skin/mucosa involvement PLUS at least one of: respiratory compromise OR hypotension/end-organ dysfunction
- Two or more of the following after likely allergen exposure: skin/mucosa, respiratory, cardiovascular, persistent GI symptoms
- Reduced BP after known allergen exposure (age-specific: SBP <70 mmHg below 1 year; <[70 + 2×age] from 1-10 years; <90 mmHg above 10 years)
This patient meets criterion 1 — urticaria + angioedema (skin/mucosa) PLUS stridor and hypotension (respiratory and CV). Diagnosis: severe pediatric anaphylaxis from peanut exposure.
A — Airway: Stridor and lip swelling indicate impending airway obstruction. Immediate IM adrenaline. Prepare for difficult airway — call senior anesthetist, ENT backup. Have a smaller endotracheal tube (one size smaller than predicted) and a surgical airway kit at the bedside.
B — Breathing: RR 36, SpO2 88 percent, wheeze + stridor — type I respiratory failure with combined upper and lower airway involvement. Apply non-rebreather mask 15 L/min. Nebulized salbutamol 2.5 mg + ipratropium 250 mcg for bronchospasm. Nebulized adrenaline 1:1000, 0.5 mL/kg (max 5 mL) for stridor (Croup-style use).
C — Circulation: HR 152, BP 76/42, prolonged capillary refill — distributive shock from histamine-induced vasodilation and capillary leak (up to 50 percent of intravascular volume can shift in minutes). Establish 2 IV lines (or IO if difficulty), give normal saline bolus 20 mL/kg over 10-15 minutes (= 500 mL for 25 kg child); repeat if no response.
D — Disability: GCS 12 from cerebral hypoperfusion. Will improve with adrenaline + fluids. Glucose 98 — no hypoglycemia.
Immediate management — adrenaline first, everything else second
Step 1: Intramuscular adrenaline (the only first-line drug)
IM adrenaline 1:1000 (1 mg/mL), 0.01 mg/kg into the anterolateral mid-thigh (vastus lateralis muscle).
For our 25 kg patient: 0.25 mg = 0.25 mL of 1:1000 adrenaline. Maximum single dose 0.3 mg in children below 30 kg, 0.5 mg in adolescents and adults.
| Age/Weight | IM dose (1:1000) |
|---|
| Below 6 months / <7.5 kg | 0.05 mL |
| 6 months - 6 years / 7.5-15 kg | 0.15 mL (150 mcg) |
| 6-12 years / 15-30 kg | 0.30 mL (300 mcg) — EpiPen Jr |
| Above 12 years / >30 kg | 0.50 mL (500 mcg) — EpiPen |
Why anterolateral mid-thigh and not deltoid? Vastus lateralis has a richer blood supply, faster absorption, and reaches peak plasma levels in 5-10 minutes versus 10-30 minutes for deltoid IM or subcutaneous routes.
Why IM and not IV? IV adrenaline as a bolus causes ventricular arrhythmias and hypertensive crisis — and is the most common cause of iatrogenic deaths in anaphylaxis. IV adrenaline (as an infusion at 0.1-1 mcg/kg/min) is reserved for refractory anaphylaxis after 2-3 IM doses have failed.
Repeat: if no clinical improvement within 5-15 minutes, repeat IM adrenaline at the same dose. Most patients respond after 1-2 doses; about 10 percent need 3 or more.
Step 2: Position the patient supine with legs elevated
Lay the patient flat with legs raised to improve venous return and cardiac preload. Sudden movement to upright posture in a volume-depleted anaphylactic patient can cause empty ventricle syndrome and pulseless electrical activity — there are documented case reports of death from this maneuver.
Exceptions:
- Airway compromise (stridor, drooling): keep in position of comfort, usually sitting forward
- Vomiting: left lateral position
- Pregnancy: left lateral to relieve aortocaval compression
Step 3: Oxygen, IV access, fluids
- High-flow oxygen 15 L/min via non-rebreather (regardless of saturation initially)
- Two large-bore IV cannulae (or intraosseous if difficulty within 90 seconds)
- Normal saline bolus 20 mL/kg over 10-15 minutes for hypotension; repeat up to total 60 mL/kg in first hour
- For our patient: 25 × 20 = 500 mL NS bolus; reassess; up to 1500 mL in the first hour
Step 4: Second-line adjunctive therapies (NOT substitutes for adrenaline)
| Drug | Pediatric dose | Role |
|---|
| H1 antihistamine — chlorphenamine | 0.2 mg/kg IV/IM (max 10 mg in 6-12 yr) | Relieves urticaria/itching ONLY — no airway/CV benefit |
| H2 antihistamine — ranitidine | 1 mg/kg IV (max 50 mg) | Adjunct to H1 for cutaneous symptoms |
| IV hydrocortisone | 4 mg/kg IV (max 200 mg) | Reduces biphasic reaction risk; takes 4-6 hours to act |
| Nebulized salbutamol | 2.5 mg neb (5 mg if >5 yr) | Bronchospasm not relieved by adrenaline |
| Nebulized adrenaline 1:1000 | 0.5 mL/kg (max 5 mL) | Upper airway edema/stridor as a bridge to definitive airway |
| Glucagon | 20-30 mcg/kg IV (max 1 mg) | For patients on beta-blockers with refractory hypotension |
Step 5: Refractory anaphylaxis
If 2-3 IM adrenaline doses fail to stabilize the patient, escalate:
- IV adrenaline infusion 0.1-1 mcg/kg/min titrated to BP and HR (cardiac monitoring mandatory)
- Add second vasopressor: noradrenaline or vasopressin
- Consider methylene blue 1-2 mg/kg IV for refractory shock (off-label, last-resort)
- ICU admission, prepare for advanced airway management
For our patient — the response
After the first IM adrenaline 0.25 mg into the right thigh, plus 500 mL NS over 10 minutes and high-flow oxygen, by the 8-minute mark: HR drops to 124, BP rises to 96/58, stridor resolves, SpO2 improves to 96 percent on 2 L. The patient becomes alert (GCS 15). Second-line agents — IV chlorphenamine 5 mg, IV hydrocortisone 100 mg, nebulized salbutamol 2.5 mg — are given over the next 30 minutes. He is admitted to the pediatric HDU for 12-24 hour observation.
Biphasic anaphylactic reaction
A biphasic reaction is the recurrence of anaphylactic symptoms 1-72 hours (most commonly 4-12 hours) after apparent resolution, without re-exposure to the trigger. Incidence is 5-20 percent of all anaphylaxis cases.
Risk factors for biphasic reactions:
- Severe initial reaction with hypotension
- Delayed adrenaline (more than 30 minutes from symptom onset)
- Need for more than one adrenaline dose
- Severe initial respiratory or CV compromise
- Initial laryngeal edema
- Drug or food trigger (versus venom)
Observation duration based on risk:
| Risk profile | Minimum observation |
|---|
| Mild reaction, prompt single-dose adrenaline response | 4-6 hours |
| Multiple adrenaline doses needed OR hypotension | 12-24 hours |
| Severe airway compromise OR delayed adrenaline | 24 hours, often in HDU/ICU |
Discharge planning and counseling — six essentials
- Two EpiPens prescribed — one for home, one for school. Reason for two: a single device may fail to fire, and 10-20 percent of patients need a second dose before paramedic arrival. EpiPen Jr (150 mcg) for 7.5-30 kg children; EpiPen (300 mcg) for above 30 kg.
- EpiPen administration training — demonstrate on a trainer device. Steps: blue safety cap off, orange tip into anterolateral mid-thigh (through clothing if necessary), push firmly until click, hold for 3 seconds, massage area for 10 seconds, call ambulance immediately.
- Personalized written action plan — naming the trigger, listing symptoms, specifying when to give EpiPen, and "always call ambulance after any EpiPen use even if symptoms improve."
- Strict allergen avoidance — food label reading education ("may contain traces of peanuts" labels), restaurant communication, school canteen notification.
- Specialist referral — pediatric allergist within 4-6 weeks for skin prick or specific IgE testing, consideration of oral immunotherapy (OIT, an emerging treatment for peanut allergy).
- Medical alert — bracelet/necklace stating "Peanut allergy — anaphylaxis"; school authorities, class teachers, and bus drivers all informed; supply of EpiPens at school with a Care Plan.
How NEET PG tests anaphylaxis
NEET PG tests anaphylaxis through five recurring patterns. Each pattern targets a single high-yield decision point.
Pattern 1 — The first-line drug question: "8-year-old child with bee-sting anaphylaxis. The first drug to give is?" Answer: IM adrenaline 0.01 mg/kg. Trap: "IV chlorphenamine" or "IV hydrocortisone" — antihistamines and steroids are NEVER first-line.
Pattern 2 — The dose question: "Pediatric anaphylaxis dose of adrenaline?" Answer: 0.01 mg/kg of 1:1000 IM, max 0.3 mg in <30 kg children. Trap: confusing 1:1000 with 1:10,000 (1:10,000 is for IV cardiac arrest, NOT IM anaphylaxis).
Pattern 3 — The route question: "Best route for adrenaline in anaphylaxis?" Answer: intramuscular into anterolateral thigh. Trap: "subcutaneous" (slower absorption) or "IV bolus" (causes arrhythmias).
Pattern 4 — The biphasic reaction question: "Patient improved 1 hour after adrenaline; when can you discharge?" Answer: minimum 4-6 hours observation, longer if high-risk. Trap: "discharge after 1 hour if asymptomatic."
Pattern 5 — The position question: "Best position in anaphylactic shock?" Answer: supine with legs elevated (unless airway compromise — then position of comfort). Trap: "Trendelenburg" (no longer recommended) or "sitting upright."
High-yield one-liners:
- IM adrenaline 1:1000, 0.01 mg/kg, anterolateral thigh — first and only first-line drug
- Max single dose: 0.3 mg in <30 kg, 0.5 mg in >30 kg
- Repeat every 5-15 minutes if no response
- IV adrenaline = infusion only, NOT bolus
- Antihistamines and steroids are second-line; they don't reverse shock or airway
- Position supine with legs up; sitting up can cause PEA arrest
- Observe at least 4-6 hours; 12-24 hours if high-risk
- Two EpiPens at discharge + written action plan + allergist referral
- Diagnostic criteria: NIAID/FAAN 2020 — skin + airway/CV after exposure
- Refractory: IV adrenaline infusion 0.1-1 mcg/kg/min after 2-3 IM doses
Frequently Asked Questions
What is the dose of intramuscular adrenaline in pediatric anaphylaxis?
IM adrenaline (1:1000, 1 mg/mL) at 0.01 mg/kg (0.01 mL/kg) into the anterolateral mid-thigh (vastus lateralis), maximum single dose 0.5 mg in adults, 0.3 mg in children below 30 kg. Repeat every 5-15 minutes if no improvement. Never give IV adrenaline as a first-line bolus in anaphylaxis — it causes ventricular arrhythmias and hypertensive crisis. IV adrenaline infusion (0.1-1 mcg/kg/min) is reserved for refractory anaphylaxis after 2-3 IM doses fail.
Why is adrenaline first-line and antihistamines second-line in anaphylaxis?
Adrenaline acts on alpha-1 (vasoconstriction reverses hypotension and mucosal edema), beta-1 (positive inotropy and chronotropy), and beta-2 receptors (bronchodilation, mast cell stabilization). It works in 5 minutes. Antihistamines (H1 blockers like chlorphenamine or diphenhydramine) only relieve cutaneous symptoms (itching, urticaria) — they do NOT reverse airway obstruction, hypotension, or shock. Steroids take 4-6 hours to work and only reduce biphasic reaction risk. Delay in giving adrenaline is the leading cause of death in anaphylaxis.
What is a biphasic anaphylactic reaction and how is it managed?
A biphasic reaction is recurrence of anaphylactic symptoms 1-72 hours (typically 4-12 hours) after apparent resolution, occurring in 5-20% of cases without continued mediator release. Risk factors: severe initial reaction, delayed adrenaline (above 30 minutes), need for more than one adrenaline dose, hypotension. Management: observe all anaphylaxis patients for at least 4-6 hours; observe high-risk patients (hypotension, multiple doses, severe airway involvement) for 12-24 hours. Discharge with two EpiPens, written action plan, and oral steroids for 3 days.
What positioning is correct in anaphylaxis?
Lay the patient supine with legs elevated to improve venous return and cardiac preload. Do NOT sit them up — sudden upright posture in volume-depleted anaphylaxis can cause empty ventricle syndrome and pulseless electrical activity (PEA arrest). The exception: if the patient has airway compromise (stridor, drooling), keep them in their position of comfort, usually sitting forward. In pregnancy, place in left lateral position to relieve aortocaval compression.
How do you counsel a child and family after anaphylaxis discharge?
Six discharge essentials: (1) Prescribe two EpiPens (one for school, one for home; one device may fail or a second dose may be needed), (2) Demonstrate EpiPen use on a trainer device — anterolateral thigh, through clothing, hold 3 seconds, (3) Personalized written action plan listing trigger, symptoms, when to give EpiPen, and when to call ambulance, (4) Strict allergen avoidance with food label education, (5) Refer to pediatric allergist for skin prick or specific IgE testing and discussion of oral immunotherapy, (6) Medical alert bracelet and notification of school authorities and class teachers.
This content is for educational purposes for NEET PG exam preparation. It is not a substitute for professional medical advice, diagnosis, or treatment. Clinical information has been reviewed by qualified medical professionals.
Written by: NEETPGAI Editorial Team
Reviewed by: Pending SME Review
Last reviewed: April 2026
