ICU · resuscitation

Acute Severe Anaphylaxis — Comprehensive Peri-Arrest Management

Also known as Anaphylaxis · Anaphylactic shock · Severe allergic reaction · Anaphylactoid reaction · Perioperative anaphylaxis · NMBA anaphylaxis · Drug anaphylaxis · Food anaphylaxis · Insect venom anaphylaxis · Tryptase

Acute severe anaphylaxis — a rapidly progressive, life-threatening systemic hypersensitivity reaction causing mast cell and basophil degranulation → release of histamine, tryptase, leukotrienes, prostaglandins → vasodilation (distributive shock), bronchoconstriction (bronchospasm), increased vascular permeability (angioedema, upper airway obstruction), and gastrointestinal symptoms. Triggers: drugs (1 — antibiotics, NSAIDs, neuromuscular blocking agents, chemotherapy), foods (peanut, tree nut, shellfish, egg, milk), insect venom (bee, wasp), radiocontrast media, latex, exercise, idiopathic. Clinical criteria (NIAID/FAAN): acute onset (minutes to hours) with involvement of skin/mucosa PLUS respiratory compromise AND/OR reduced BP/organ dysfunction. Brown's severity grading: grade 1 (mild — skin only), grade 2 (moderate — skin + respiratory/cardiovascular/GI), grade 3 (severe — hypoxia, hypotension, neurologic compromise). Management: (1) IM ADRENALINE 0.5 mg (anterolateral thigh — repeat every 5 min), (2) POSITIONING (supine + legs elevated — 'elevated legs save lives' — empty IVC syndrome is fatal), (3) HIGH-FLOW OXYGEN + IV FLUIDS (rapid bolus 20 mL/kg crystalloid — massive volume sequestration from capillary leak), (4) REFRACTORY: IV adrenaline infusion (0.05-0.5 mcg/kg/min), vasopressin, methylene blue (NO-mediated vasoplegia), glucagon (beta-blocked patients), (5) ADJUNCTS: H1 blocker (cetirizine), H2 blocker (ranitidine), corticosteroids (hydrocortisone 200 mg IV), nebulised salbutamol (bronchospasm), (6) POST-EVENT: serial tryptase (peak 1-2h, baseline at 24h — confirms mast cell degranulation), allergy referral, adrenaline auto-injector, trigger identification. Perioperative anaphylaxis: NMBA 1 trigger (rocuronium, suxamethonium), tryptase during event + at 24h baseline, allergy testing 4-6 weeks post-event.

high13 referencesUpdated 26 July 202615 min readSource-verified · Sept 2026

Checked against its sources on 3 Sept 2026

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IM ADRENALINE 0.5 mg (0.01 mg/kg of 1 in 1000, maximum initial dose 0.5 mg) into the anterolateral thigh is the FIRST-LINE treatment — IV adrenaline must only be used in certain specialist settings and only by those skilled and experienced in its use
POSITIONING is critical — supine with legs elevated; if respiratory distress is present, allow the patient to sit upright with legs extended and elevated — the position of comfort with lower extremities elevated is part of first-line care
REFRACTORY anaphylaxis (no recovery after IM adrenaline): give aggressive IV fluid resuscitation and an IV adrenaline infusion; second-line vasopressor options are noradrenaline, vasopressin, metaraminol or dopamine (preferred agent unknown); IV glucagon for patients on beta-blockers; methylene blue or extracorporeal life support as rescue therapy
Beta-blocked patients: most guidelines recommend IV GLUCAGON despite a lack of evidence — it acts independently of the beta-receptor
Perioperative anaphylaxis: the number-one trigger in the ninth French survey was NEUROMUSCULAR BLOCKING AGENTS (47.4 percent of cases; succinylcholine the most frequently incriminated at 60.6 percent of NMBA cases) — ahead of latex (20 percent) and antibiotics (18.1 percent) — refer to an allergy specialist; diagnosis rests on clinical history, skin tests and/or specific IgE assay
Serum mast-cell tryptase measured after onset is an adjunct to diagnosis and correlates with reaction severity — levels immediately to 1 hour and 2 to 4 hours after onset correlate inversely with the minimum systolic blood pressure
Biphasic reaction — recurrence after initial resolution — is reported in 0.4 to 20 percent of episodes; risk factors are severe initial symptoms (hypotension, hypoxia), delay in adrenaline, and needing more than one adrenaline dose; observe every patient for at least 4 hours after symptom resolution

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Practise this topic8 MCQs with explanations

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CICMFFICMEDIC

Red flags

IM ADRENALINE 0.5 mg (0.01 mg/kg of 1 in 1000, maximum initial dose 0.5 mg) into the anterolateral thigh is the FIRST-LINE treatment — IV adrenaline must only be used in certain specialist settings and only by those skilled and experienced in its use
POSITIONING is critical — supine with legs elevated; if respiratory distress is present, allow the patient to sit upright with legs extended and elevated — the position of comfort with lower extremities elevated is part of first-line care
REFRACTORY anaphylaxis (no recovery after IM adrenaline): give aggressive IV fluid resuscitation and an IV adrenaline infusion; second-line vasopressor options are noradrenaline, vasopressin, metaraminol or dopamine (preferred agent unknown); IV glucagon for patients on beta-blockers; methylene blue or extracorporeal life support as rescue therapy
Beta-blocked patients: most guidelines recommend IV GLUCAGON despite a lack of evidence — it acts independently of the beta-receptor
Perioperative anaphylaxis: the number-one trigger in the ninth French survey was NEUROMUSCULAR BLOCKING AGENTS (47.4 percent of cases; succinylcholine the most frequently incriminated at 60.6 percent of NMBA cases) — ahead of latex (20 percent) and antibiotics (18.1 percent) — refer to an allergy specialist; diagnosis rests on clinical history, skin tests and/or specific IgE assay
Serum mast-cell tryptase measured after onset is an adjunct to diagnosis and correlates with reaction severity — levels immediately to 1 hour and 2 to 4 hours after onset correlate inversely with the minimum systolic blood pressure
Biphasic reaction — recurrence after initial resolution — is reported in 0.4 to 20 percent of episodes; risk factors are severe initial symptoms (hypotension, hypoxia), delay in adrenaline, and needing more than one adrenaline dose; observe every patient for at least 4 hours after symptom resolution

Meet the patient

A 56-year-old man on the orthopaedic ward receives intravenous teicoplanin as surgical prophylaxis. Within two minutes he develops flushing, a burning sensation in his palms, abdominal cramping, and audible wheeze. By the time you reach the bedside his tongue is swelling, his BP is 64 over 40, and his SpO2 is 82 percent on high-flow oxygen. The nurse has drawn up hydrocortisone. You will hand her an adrenaline ampoule instead — and you will give it now, intramuscularly, into his anterolateral thigh.^[2]

The two questions that decide his next five minutes are the two that decide every anaphylaxis stem: is the airway about to obstruct? — intubate early, before the cords disappear — and has the circulation emptied into the periphery? — lie him flat with legs elevated, because sitting kills. Hold those two and everything else slots into place.^[4]

The one-line exam answer

Anaphylaxis is a rapidly progressive systemic hypersensitivity reaction — mast-cell and basophil degranulation releases histamine, tryptase, leukotrienes and prostaglandins, producing vasodilation with distributive shock, bronchoconstriction, angioedema with upper-airway obstruction, and gut symptoms. The first-line treatment is intramuscular adrenaline into the anterolateral thigh — 0.01 mg/kg of 1 in 1000 to a maximum initial dose of 0.5 mg in adults — repeated every 5 to 15 minutes for persistent anaphylaxis, with the patient supine and legs elevated, oxygen and airway support, and intravenous fluid resuscitation. Refractory disease escalates to an IV adrenaline infusion with aggressive fluid resuscitation, adding adjuncts as required — a second-line vasopressor (noradrenaline, vasopressin, metaraminol or dopamine), IV glucagon for the beta-blocked patient, and methylene blue or extracorporeal life support as rescue therapy. The ICU sees two classic scenarios — the perioperative patient (neuromuscular blocking agents are the leading trigger in the French national surveys) and the community/ED patient with food, venom or drug anaphylaxis — and the initial actions are identical: adrenaline, position, airway, fluids.

^[7]^[8]^[6]

References13Show

[1]Brown SG, Mullins RJ, Gold MS Anaphylaxis: diagnosis and management. Med J Aust, 2006.PMID 16948628
[2]Cardona V, et al. World allergy organization anaphylaxis guidance 2020. World Allergy Organ J, 2020.PMID 33204386
[3]Dong SW, Mertes PM, Petitpain N, et al. Hypersensitivity reactions during anesthesia. Results from the ninth French survey (2005-2007). Minerva Anestesiol, 2012.PMID 22441362
[4]Soar J, Pumphrey R, Cant A, et al. Emergency treatment of anaphylactic reactions--guidelines for healthcare providers. Resuscitation, 2008.PMID 18358585
[5]Francuzik W, Dölle S, Worm M Risk factors and treatment of refractory anaphylaxis - a review of case reports. Expert Rev Clin Immunol, 2018.PMID 29513116
[6]Pouessel G, Dribin TE, Tacquard C, et al. Management of Refractory Anaphylaxis: An Overview of Current Guidelines. Clin Exp Allergy, 2024.PMID 38866583
[7]Li LDX, Abrams EM, Lavine E, et al. CSACI position statement: transition recommendations on existing epinephrine autoinjectors. Allergy Asthma Clin Immunol, 2021.PMID 34903280
[8]Dribin TE, Sobolewski B, Campbell RL, et al. Anaphylaxis Clinical Care Pathway: Incorporating Intranasal Epinephrine (Adrenaline). J Allergy Clin Immunol Pract, 2026.PMID 42447993
[9]Giannetti MP Epidemiology, Risk Factors, and Management of Biphasic Anaphylaxis. Curr Allergy Asthma Rep, 2024.PMID 39259441
[10]Simons FE, Ardusso LR, Bilò MB, et al. World allergy organization guidelines for the assessment and management of anaphylaxis. World Allergy Organ J, 2011.PMID 23268454
[11]Nishio Y, Hara M, Oshita K, et al. Relationship between Tryptase and Hypotension in Anaphylaxis during Anesthesia. Kurume Med J, 2024.PMID 38763736
[12]Jeon J, Lee YJ, Lee SY Effect of icatibant on angiotensin-converting enzyme inhibitor-induced angioedema: A meta-analysis of randomized controlled trials. J Clin Pharm Ther, 2019.PMID 31290163
[13]Maurer M, Magerl M, Betschel S, et al. The international WAO/EAACI guideline for the management of hereditary angioedema-The 2021 revision and update. Allergy, 2022.PMID 35006617