Clinical Guides
Anaphylaxis: Recognition and Emergency Management
A clinically focused guide to recognising and treating anaphylaxis across Indian emergency, hospital and immunisation settings, prepared for mandatory clinical review.
MedNext Academy | 12 min read
Anaphylaxis: Recognition and Emergency Management
A clinically focused guide to recognising and treating anaphylaxis across Indian emergency, hospital and immunisation settings, prepared for mandatory clinical review.
Summary
Anaphylaxis is a rapidly evolving systemic hypersensitivity reaction that can obstruct the airway, impair breathing or cause circulatory collapse. Treat the clinical syndrome immediately; neither absence of a rash nor uncertainty about the trigger justifies waiting when airway, breathing or circulation compromise follows a plausible exposure. Stop the suspected trigger when feasible, call for resuscitation support, position the patient safely, assess airway-breathing-circulation and give intramuscular adrenaline into the mid-anterolateral thigh. For healthcare dosing, use adrenaline 1 mg/mL (often labelled 1:1000) at 0.01 mg/kg, capped at 0.5 mg per dose; repeat after about 5 minutes if life-threatening features persist. Oxygen, monitoring, intravenous or intraosseous access and crystalloid are supportive measures, never replacements for adrenaline. Intravenous adrenaline is hazardous and belongs only in monitored, expert-led management of refractory shock or cardiac arrest protocols. After recovery, document the chronology, consider timed mast-cell tryptase without delaying treatment, observe according to recurrence risk, prescribe an emergency plan when appropriate and arrange allergy evaluation. A post-vaccination event must also enter India’s AEFI pathway. This guide is educational and deliberately quarantined following MedNext Clinical Team review by the MedNext Clinical Team; local emergency protocols, product labels and senior clinical judgement remain controlling.
How Common Is It?
The frequency of anaphylaxis depends on how cases are defined, which exposures are studied and whether community events are captured. International guidance describes an increasing burden, but Indian population-level estimates remain incomplete and should not be converted into a confident national incidence. Food, medicines and insect venom are common trigger groups; perioperative agents, radiocontrast, latex and vaccines account for smaller but operationally important subsets. Vaccine-associated anaphylaxis is very rare, yet every immunisation session must be equipped because delay in a rare emergency can be fatal. Surveillance reports count events after immunisation, not automatically events caused by a vaccine: temporal association requires investigation and formal causality assessment. Underrecognition occurs when skin findings are absent, hypotension is attributed to vasovagal syncope, wheeze is labelled asthma alone, or gastrointestinal and cardiovascular features are considered separately. Overdiagnosis also occurs, especially when anxiety, flushing or a simple faint follows an injection. Therefore, service quality is better measured by readiness, timely adrenaline, accurate reporting and appropriate follow-up than by an unsupported local prevalence figure. Clinicians should record the denominator when auditing a defined setting—for example, administrations, infusions or anaesthetics—and avoid comparing rates derived from incompatible definitions.
Risk Factors
A previous reaction to the same allergen is the clearest warning, but a first recognised episode can occur without known allergy. Important triggers include foods, antibiotics and other medicines, insect stings, radiocontrast, latex, biological agents, perioperative drugs and, rarely, vaccine components. Exercise, acute infection, alcohol, sleep deprivation, non-steroidal anti-inflammatory drugs and menstruation can act as cofactors that lower the reaction threshold in susceptible people. Poorly controlled asthma, mast-cell disorders and cardiovascular disease may increase severity or complicate rescue. Older age, pregnancy, beta-blocker or renin-angiotensin-system therapy and delayed access to emergency care can make haemodynamic management more difficult, although none is a reason to withhold intramuscular adrenaline. Risk is shaped by route and rate: intravenous exposure may provoke an abrupt severe reaction, while an ingested allergen can continue to be absorbed. In an immunisation clinic, screen for a prior anaphylactic reaction to a previous dose or known component, distinguish this from expected fever or local pain, and keep an in-date adrenaline kit at every fixed, outreach and mobile session. Do not invent broad vaccine exemptions for eczema, family history or mild intercurrent illness. The history should identify the exact product, formulation, timing, co-exposures and treatment because a vague label such as ‘allergic to injections’ can deny beneficial therapy without improving safety.
Diagnosis
History
Diagnose clinically from sudden illness after a likely exposure. Establish the minute-by-minute sequence: trigger, route, dose, first symptom, progression and treatment. Ask about throat tightness, voice change, stridor, wheeze, breathlessness, collapse, confusion, urticaria, angioedema, flushing, severe cramping or repetitive vomiting. Record cofactors, prior reactions, asthma, mast-cell disease, medicines and baseline cardiovascular status. Skin or mucosal change supports the diagnosis but may be absent in severe reactions. Ask a witness what changed first, because a patient with hypoxia or shock may not recall the sequence. Identify all foods, medicines, infusions, antiseptics, exercise and stings in the relevant window rather than anchoring on the most conspicuous exposure.
Examination
Assess airway, breathing, circulation, disability and skin simultaneously. Look for tongue or laryngeal swelling, hoarseness, stridor, hypoxaemia, bronchospasm, tachycardia, hypotension, poor perfusion and altered consciousness. Expose sufficiently to find generalised erythema or hives while preventing heat loss. A supine patient with pallor, bradycardia and rapid recovery may have vasovagal syncope; persistent respiratory or circulatory compromise is not a simple faint. Reassess continuously because findings evolve. Record serial observations and the physiological response after each intervention; improvement following adrenaline supports management but is not a retrospective diagnostic test.
Investigations
No test should postpone adrenaline. Use pulse oximetry, repeated non-invasive blood pressure, ECG and capnography where available. Obtain investigations directed by complications. Timed mast-cell tryptase can support later assessment, especially in adults, but a normal result does not exclude anaphylaxis; document sampling time relative to onset. Save product and batch details after a suspected AEFI and complete the national reporting record.
Differential Diagnosis
The dangerous differential is any condition that causes sudden airway, respiratory or circulatory failure. Vasovagal syncope usually brings pallor, sweating, bradycardia and prompt improvement when supine; anaphylaxis more often produces persistent compromise, tachycardia, wheeze, stridor, mucosal swelling or generalised skin findings. Panic and hyperventilation can cause tingling, dizziness and dyspnoea but do not explain objective airway oedema, bronchospasm or shock. Acute severe asthma may be indistinguishable when cutaneous signs are absent, so a plausible allergen exposure and systemic features matter. Consider aspiration, pulmonary embolism, acute coronary syndrome, arrhythmia, sepsis, haemorrhage and other shock states. Upper-airway mimics include foreign body, inducible laryngeal obstruction and hereditary or bradykinin-mediated angioedema; the latter often lacks urticaria and responds poorly to adrenaline, although airway support remains urgent. Scombroid poisoning may affect several diners with flushing and headache. Perioperative reactions require reconstruction of every administered agent, antiseptic, latex exposure and timing. After vaccination, distinguish immunisation stress-related responses, breath-holding, hypoglycaemia and seizure, while treating suspected anaphylaxis first if objective life-threatening features exist. The correct discipline is parallel reasoning: initiate time-critical care, then refine the diagnosis as response, records and investigations accumulate.
Management
Call for help and an emergency transfer while removing the trigger if this is immediately safe—for example, stop an intravenous infusion without delaying care. Place most patients flat with legs supported; do not allow sudden standing or walking. Use a left-sided semi-recumbent position in pregnancy, recovery position if unconscious but breathing, and cautious sitting only when respiratory distress makes lying flat intolerable. Give intramuscular adrenaline promptly into the mid-anterolateral thigh: 0.01 mg/kg of 1 mg/mL solution, maximum 0.5 mg. In an adult or adolescent, 0.5 mg is the usual healthcare dose; use weight-based paediatric dosing. If airway, breathing or circulation problems continue, repeat at roughly 5-minute intervals while reassessing. Deliver high-concentration oxygen, attach monitoring, obtain IV or IO access and give rapid isotonic crystalloid for shock, with repeated boluses guided by age, response and comorbidity. Begin cardiopulmonary resuscitation if arrest occurs. Nebulised bronchodilator may treat persistent wheeze and nebulised adrenaline may be an adjunct for upper-airway obstruction, but neither replaces intramuscular adrenaline. Antihistamines address residual skin symptoms only after stabilisation; corticosteroids are not routine first-line rescue. Refractory anaphylaxis after repeated appropriate IM doses and fluid requires early critical-care help and a carefully titrated IV adrenaline infusion in a monitored environment. For vaccine-associated anaphylaxis in the Indian field protocol, the ANM gives the authorised first dose, records it, activates transport and transfers with the patient; the receiving medical officer prepares for ongoing resuscitation and reporting.
Prescribing Information
Adrenaline is the decisive medicine. Confirm concentration before drawing it up: 1 mg/mL is the intramuscular anaphylaxis preparation, and 0.01 mg equals 0.01 mL. Thus a 20 kg child receives 0.2 mg or 0.2 mL; the dose ceiling is 0.5 mg or 0.5 mL. Use an appropriate graduated syringe and inject into the anterolateral thigh, not subcutaneously. Do not dilute the IM dose and do not confuse it with cardiac-arrest concentrations. Palpitations, tremor, pallor, anxiety and headache can follow a correct dose; serious arrhythmia, hypertensive crisis or pulmonary oedema is more strongly associated with overdose or inappropriate intravenous bolus administration. There is no absolute contraindication to IM adrenaline in life-threatening anaphylaxis. If beta-blockade contributes to refractory shock, critical-care teams may consider glucagon with monitoring for vomiting and hyperglycaemia. Oxygen, balanced or normal saline, inhaled beta-2 agonist and other adjuncts are prescribed against a specific physiological problem. At Indian immunisation sites, store ampoules protected from light and excessive heat, check clarity and expiry, maintain syringes, needles, airway supplies and transport contacts, and have the medical officer certify kits at least quarterly. Discharge prescribing should reflect specialist assessment and local availability: if an adrenaline auto-injector is indicated, teach activation, thigh placement, immediate emergency contact and the need to carry devices; never imply that possessing a device makes hospital assessment unnecessary.
When to Refer
Any current airway swelling, stridor, severe bronchospasm, hypoxaemia, hypotension, collapse, altered consciousness or need for adrenaline warrants emergency transfer to a facility capable of resuscitation and observation. Escalate immediately when two correctly delivered IM doses have not stabilised the patient, when repeated fluid is required, or when an IV adrenaline infusion, intubation, obstetric support or paediatric critical care may be needed. After emergency treatment, offer referral to an age-appropriate allergy service so the likely trigger, cross-reactivity, avoidance plan and need for supervised testing or immunotherapy can be evaluated. Refer drug reactions with exact generic name, brand, formulation, route and chronology rather than an unhelpful class-wide label. Perioperative cases need anaesthetic and allergy collaboration; insect-venom reactions may require consideration of venom immunotherapy; suspected mast-cell disease merits specialist investigation. A pregnant patient needs obstetric involvement because maternal oxygenation and perfusion determine fetal wellbeing. Every severe or serious post-immunisation event must follow the applicable AEFI reporting, investigation and transfer pathway, including product, batch, session site and treatment details. Geographic remoteness, unreliable supervision after discharge or poor access to emergency return lowers the threshold for longer observation or admission. Referral is not complete until the receiving team has a verbal handover plus written dose times, response, co-exposures and outstanding risks.
Red Flags
Treat hoarseness, stridor, tongue swelling, inability to speak, silent chest, cyanosis, oxygen desaturation, persistent wheeze, hypotension, rapidly worsening tachycardia, confusion, collapse or cardiac arrest as immediately life-threatening. A patient can have fatal anaphylaxis without urticaria, so the absence of skin signs is never reassuring when airway, breathing or circulation failure follows a plausible trigger. Deterioration after apparent improvement may represent a biphasic reaction; renewed symptoms require fresh ABC assessment and adrenaline when diagnostic criteria are again met, not reflex antihistamine alone. Continued gut absorption, a depot injection or a long-acting preparation may prolong risk. More than two IM doses, severe asthma, marked respiratory compromise, previous biphasic reaction, late-night presentation, pregnancy, limited ability to recognise recurrence or distance from emergency care argue for prolonged monitored observation. Medication hazards are themselves red flags: subcutaneous injection, an underdose, dilution delay, the wrong concentration, or an unmonitored IV bolus can cause avoidable harm. At an immunisation session, missing or expired adrenaline, no dose chart, absent transport plan or failure to report a severe event is a systems emergency. Do not let blood sampling, cannulation, paperwork or searching for an antihistamine precede the first IM dose in a clinically convincing case.
Indian Clinical Context
India’s national AEFI system separates temporal association from causation and requires serious and severe events to be reported, investigated and assessed through designated committees. Each fixed, outreach or mobile vaccination session should have an anaphylaxis kit containing in-date adrenaline and the equipment specified by the programme, with emergency numbers and a pre-agreed receiving facility. Frontline staff need recurrent simulation because recognition, dose calculation and transfer occur under pressure. The ANM operational pathway authorises initial IM adrenaline and urgent referral; the medical officer must prepare to repeat adrenaline and provide airway, oxygen, fluids and observation. Record the vaccine, manufacturer, batch, diluent, route, site, session time, symptom onset, all dose times and outcome in the beneficiary and AEFI records, including SAFE-VAC/U-WIN processes when applicable. Outside vaccination, limited auto-injector availability and affordability mean discharge plans must be realistic: written recognition instructions, accessible adrenaline where lawfully prescribed, family training and a mapped emergency facility matter more than importing a foreign template. Rural distance, ambulance delay, heat-sensitive stock management and referral capacity should inform observation decisions. National documents may differ from international recommendations in role-specific field instructions and observation duration; staff must follow the current MoHFW or state protocol while escalating clinically. Public communication should be factual and compassionate: report the event promptly, avoid premature causal claims, and explain that surveillance is a safety mechanism rather than evidence that vaccination caused the illness.
NMC Competency Mapping
This topic integrates emergency medicine, pharmacology, paediatrics, internal medicine, anaesthesiology and community medicine. A learner should be able to identify anaphylaxis clinically; distinguish it from syncope, panic, asthma and non-histaminergic angioedema; perform an ABC assessment; position the patient; select the correct adrenaline concentration, dose, route and site; reassess after treatment; and initiate oxygen, fluid, monitoring and referral. Pharmacology outcomes include adrenergic receptor effects, why intramuscular thigh delivery is preferred, adverse effects, concentration errors and the limited place of antihistamines and corticosteroids. Community-medicine outcomes include safe immunisation-session preparation, cold-chain and kit checks, AEFI classification, reporting, investigation and risk communication. Paediatric and obstetric adaptations require weight-based dosing and safe positioning. Assessment should use an observable simulation rather than recall alone: recognise a deteriorating scenario, calculate and draw up adrenaline, state the repeat interval, communicate with the team, activate transport and document the event. The learner must also explain that an AEFI is not synonymous with vaccine causation and that diagnosis remains clinical. Exact competency codes should be confirmed against the locally implemented NMC CBME curriculum and departmental logbook before publication; this draft does not invent a code where edition-specific indexing may differ.
Key Exam Pearls for NEET PG
The first-line drug is adrenaline, delivered intramuscularly into the mid-anterolateral thigh. The healthcare dose is 0.01 mg/kg of 1 mg/mL solution to a maximum of 0.5 mg, repeated after about 5 minutes when life-threatening airway, breathing or circulation features persist. Remember the concentration-volume equivalence: at 1 mg/mL, 0.2 mg occupies 0.2 mL. Skin signs are supportive but not obligatory. A faint favours pallor, bradycardia and rapid recovery supine; anaphylaxis favours progressive respiratory or circulatory compromise. Serum tryptase may support later evaluation but neither rules out the condition when normal nor delays treatment. Intravenous adrenaline bolus is not routine anaphylaxis care and can cause lethal dosing errors; refractory shock calls for expert, monitored infusion. Antihistamines treat skin symptoms after stabilisation, not airway obstruction or shock, and corticosteroids do not replace adrenaline. Positioning matters: keep the shocked patient flat, avoid sudden standing, and use left lateral tilt in pregnancy. AEFI means any untoward event after immunisation and does not establish causality. For service questions, every Indian vaccination session requires a working anaphylaxis kit, trained staff, transport linkage, documentation and reporting. Disposition is risk-based: reaction severity, adrenaline requirement, asthma, continuing allergen absorption, supervision and access to care determine observation.
Frequently Asked Questions
Should adrenaline be withheld in an older patient with coronary artery disease?
No. Life-threatening anaphylaxis has no absolute contraindication to correctly dosed intramuscular adrenaline. Give it in the anterolateral thigh while monitoring closely and treating hypoxia and shock. The greater avoidable cardiovascular danger is delayed treatment or an intravenous dosing error; obtain senior and critical-care support early.
Can anaphylaxis be diagnosed when there is no urticaria or facial swelling?
Yes. Severe airway, breathing or circulatory compromise can occur without visible skin findings. Use the timing, plausible exposure and objective physiological abnormalities. Treat a convincing emergency promptly, then investigate alternative diagnoses in parallel. A normal tryptase later also cannot by itself exclude the clinical diagnosis.
What should an Indian vaccinator do after suspected post-vaccination anaphylaxis?
Follow the current role-specific MoHFW protocol: call for help, give authorised intramuscular adrenaline without delay, position and support the patient, activate transfer, record dose and time, and notify the medical officer. Preserve product and batch details and complete serious or severe AEFI reporting without prematurely assigning causation.
Why are antihistamines and steroids not enough for anaphylactic shock?
They do not rapidly reverse laryngeal oedema, bronchospasm and vasodilatory shock. Intramuscular adrenaline provides the essential alpha- and beta-adrenergic effects. An antihistamine may later reduce persistent skin symptoms, while routine steroids have no role as a substitute for immediate adrenaline and physiological resuscitation.
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