see also: [[Adrenaline]], [[Angioedema]], [[Tryptase (Mast cell)]], [[marine ingestions|scrombroid]], [[Non-IgE Food allergy]], [[Rash#DRESS|DRESS rash]] >[!Key Points] > - Adrenaline dose: 500mcg IM repeat. IM adrenaline at 3-5 min intervals, dependeing on response; can start infusion if needed > - adrenaline infusion **0.1mcg/kg/min** (eg "dirty bag" would be 7ml/min (420mL/H) for 70kg adult) > - [[#paediatric dose]]: 10 mcg/kg up to 500mcg ![[Pasted image 20230307205535.png]] # Definition ## WHO definition "a severe, life-threatening generalised or systemic hypersensitivity reaction" - usually rapid onset with involvement of **more than one body system** - delayed onset hypotension alone may occasionally be the only feature - may be subclassified as - allergic - mediated by IgE, IgG or immune complexes - non-allergic ([[anaphylactoid]]) - allergic anaphylaxis mediated by IgE antibodies is referred to as IgE-mediated anaphylaxis The current **ASCIA** (Australasian Society of Clinical Immunology and Allergy) definition of anaphylaxis is as follows: > Any acute onset illness with typical ==skin features== (urticarial rash or erythema/flushing, and/or angioedema) > > PLUS > > Involvement of respiratory and/or cardiovascular and/or persistent severe gastrointestinal symptoms > > OR > > Any acute onset of ==hypotension or bronchospasm== or upper airway obstruction where anaphylaxis is considered possible, even if typical skin features are _not_ present. * ***The mainstay in the treatment of severe anaphylaxis is the prompt use of [[Adrenaline|adrenaline]], which can be lifesaving.** * Withholding adrenaline due to misplaced concerns of possible adverse effects can result in deterioration and death of the patient. * Adrenaline must be used at the first suspicion of anaphylaxis. It is safe and effective. # Causes - foods - eg [[#Peanut allergy|peanuts]], egg - medications - eg [[#Penicillin allergy and cephalosporin cross-reactivity|penicillin]], NSAIDs, opiates, IV conrast - plants (pollens) - latex # Risks - *Severe reactions in children more commonly result in resp symptoms than hypotension* - age >35 and previous severe reaction main risk factors for *hypotension and death* in adults # Clinical features * most anaphylaxis to insect bite occur within 1 hour * most anaphylaxis to food within 6 hours ## suspect anaphylaxis if any one is present: 1. Difficult/noisy breathing 2. Swelling of tongue 3. Swelling/tightness in throat 4. Difficulty talking and/or hoarse voice 5. Wheeze or persistent cough 6. Persistent dizziness or collapse 7. Pale and floppy (young children) 8. Vomiting and/or abdominal pain for insect stings/bites ## clincal features by system * skin * rash present in >95% of cases * absence of skin features does not exclude anaphylaxis * itchiness and redness in palms common early * generalised erythrodermic reaciton * urticaria * airway/mucous membranes * angioedema of tongue and oropharynx * throat/chest tightness * conjunctival injection * CVS * **hypotension** --> can be rapid and dramatic, causing collapse * cardiac arrest * GIT * nausea and vomiting * abdominal cramping # Severity - Mild - skin and sucutaneous tissue only - feeling crappy - periorbital oedema, angioedema without airway compromise - Moderate - sensation of dysponea / bronchospasm (wheezing) - pre-syncope - GIT upset - laryngeal oedema, aponea, drooling - Severe - hypotension (SBP < 90), collapse - arrhythmia - ALOC # Biphasic reactions * older data estimated to occur following 3-20% of anaphylactic reacitons * recent ED data suggests clinically significant delayed reactions occur in * 0.4 - 1.4 % of cases of anaphylaxis * 0.1% of cases of allergy **90% occur within 4 hours following the initial reaction** * most are not life threatening and do not require major changes in therapy * delayed reactions following discharge are **rare and slow in onset** # DDx - aortic dissection - Asthma - PE - toxic shock syndrome - bradykinin reactions # Noteworthy agents ## Peanut allergy ## Penicillin allergy and cephalosporin cross-reactivity ## Opiate and "morphine" allergy ## Chlorhexidine allergy ## Latex allergy # Investigations * no routine ix needed * can use other Ix to exclude alternative diagnoses * no definitive test to confirm diagnosis of anaphylaxis, so dx ultimately clnical ## Serum mast cell tryptase - levels ries with episodes of anaphylaxis - however, its sensitivity as a biomarker for anaphylaxis is not good (~70%) - sensitivity and specificity increased if serial measurements performed - ideally blood sample **immediatly** after event, and a second taken at 1-2 hours - vital to record both time of anaphylactic event and the time of the blood sample # Management ## Initial treatment 1. immediatly address any ABC issues 2. lie the patient flat or let them sit up iff more comfortable 1. left lateral position in pregnant patients 3. remove allergen 4. administer O2 ## Adrenaline note: * adrenaline 1:1000 is 1mg per mL * adrenaline 1:10,000 is 1mg in 10 mL (100mcg/mL) **IM preferred over IV boluses** due to risks of cardiac arrest IV ### paediatric dose 10 mcg/kg up to 500mcg | Age | weight (kg) | Vol adrenaline 1:1000 IM | | --- | --- | --- | | <1 | <7.5 | 0.1 mL| | 1-2 | 10 | 0.1 mL | | 2-3 | 15 | 0.15 mL | | 4-6 | 20 | 0.2 mL | |7-10 | 30 | 0.3 mL | |10-12 | 40 | 0.4mL | | >12 | >50 | 0.5 mL | > management of anaphylaxis in **pregnant women** is the same as for non-pregnant women, and adrenaline should not be withhold for fear of causing reduced placental perfusion ### Further adrenaline treatment * repeat IM adrenaline at 3-5 min intervals, dependeing on response * if still noresponse or transient responses, start **adrenaline infusion** > adrenaline infusion **0.1mcg/kg/min** (eg "dirty bag" would be 7ml/min (420mL/H) for 70kg adult) ## Fluid resusicitaiton * important adjunt to adrenaline adminisration ## Bronchospasm * adrenaline or salbutamol by nebulizer * note that bronchodilators will not relieve uppper airway obstuction, hypotension, or shock ## Laryngeal/ upper airway oedema * nebulised dose same for adults and kids * do not delay intubation if upper airway obstruction is progressive ## Additional treatments ### antihistamines * no good evidence ofr antihistamines in anaphylaxis, and may be detrimental (hypotension) * best use is for distressing skin manifestations in mild allergic reactions * can consider ranitidine 1mg/kg or famotidine 0.4mg/kg IV ### steroids * Efficacy is uncertain * may prevent delayed or protracted reactions * **hydrocortisone 100-250mg IV** or **dexamethasone** 10mg IV * consider 2 day course of mred 1mg/kg to max of 50mg after a severe reaction or rx with marked wheeze ### adunctive vasopressors * occasional cases are resistant in patients taking beta-blocking drugs * consider noradrenaline infusion * consider glucagon 1-2mg IV if taking beta blockers ### intubation * avoid thiopentone, midazolam, or profol (can exacerbate hypotension) # Disposition - **Observe for 4 hours** - home with epi-pen #Allergy/anaphylaxis # Related Questions ## airway obstruction - 6Q: [CICO](x-devonthink-item://2F267333-5FEC-47E5-83D1-CC05B23EB91A?page=13) -- [Answer](x-devonthink-item://C6CAC39D-CAE8-4F76-9C45-689A0464D936?page=9) - 7Q: [Partial Upper Airway Obstruction](x-devonthink-item://7061D1B4-0AB9-4963-B3B0-23BDD975B2CD?page=18) -- [Answer](x-devonthink-item://3F30C77E-E23E-4200-89FE-48A41618E0C2?page=12) ## anaphylaxis - 8Q: [Anaphylaxis](x-devonthink-item://7FCD3940-4BB4-45FE-86A6-E5707E82D5B5?page=4) -- [Answer](x-devonthink-item://3263A68A-96A6-43EC-985B-43260C3509BF?page=1) - 9Q: [Paediatric Anaphylaxis](x-devonthink-item://662C8511-01CD-4659-B57D-5A01CF74D69B?page=18) -- [Answer](x-devonthink-item://79A95C0A-634E-4B38-9131-78949F63D56F?page=17) - 10Q: [Anaphylaxis](x-devonthink-item://A077BF03-A063-4A6D-9330-67795A4B931D?page=2) -- [Answer](x-devonthink-item://C6B02ACE-5059-45D1-81CD-F99A8A13A863?page=1) ## angioedema - 11Q: [Tongue Swelling](x-devonthink-item://5DC0999B-D537-4002-86AF-FD7B54B45E2E?page=36) -- [Answer](x-devonthink-item://406AF611-5CD4-4B3B-9795-327E8F4E3626?page=15) ## ards - 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56Q: [Deteriorating Infant](x-devonthink-item://6092BF31-E542-4019-8E17-0C628DD3B0F1?page=13) -- [Answer](x-devonthink-item://E15CEB64-C6A5-4A7D-84B4-E7D1DC667B0E?page=8) ## rash - 61Q: [18 month old with rash](x-devonthink-item://09493372-578D-4C97-972A-EEC617B38B53?page=10) -- [Answer](x-devonthink-item://A0D348CE-FCD4-4ECD-BE21-6CA73F6DE8CD?page=4) - 62Q: [Painful rash](x-devonthink-item://80040649-2DDB-4266-9A7C-4DE4E6DD4AE6?page=9) -- [Answer](x-devonthink-item://C96EDD2F-137A-43E5-80EE-5F42C5971D55?page=13) - 63Q: [Measles](x-devonthink-item://1A2C485F-D4AD-4821-AFF2-452BA753717F?page=52) -- [Answer](x-devonthink-item://FD716379-1A77-4B5B-B257-1154995ECA6E?page=33) - 64Q: [Rash](x-devonthink-item://F0498813-9350-484C-AD5B-6FF7C3AE9015?page=12) -- [Answer](x-devonthink-item://A491A3F6-FD6D-492F-BCBE-7F7BAE101EDF?page=9) - 65Q: [Rash](x-devonthink-item://5DC0999B-D537-4002-86AF-FD7B54B45E2E?page=23) -- [Answer](x-devonthink-item://406AF611-5CD4-4B3B-9795-327E8F4E3626?page=8) - 66Q: [Child with Rash](x-devonthink-item://7FCD3940-4BB4-45FE-86A6-E5707E82D5B5?page=25) -- [Answer](x-devonthink-item://3263A68A-96A6-43EC-985B-43260C3509BF?page=8) - 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