Diferencia entre revisiones de «Anaphylaxis»
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==Background== | ==Background== | ||
* | *'''Acute, life-threatening, systemic allergic reaction''' involving multiple organ systems | ||
*IgE-mediated (type I hypersensitivity) in most cases; can also be non-IgE mediated (anaphylactoid) | |||
*'''Biphasic reaction''' occurs in '''5-20%''' of cases (recurrence 1-72 hours after initial reaction, usually within 8-10 hours)<ref>Lee S, et al. Biphasic anaphylaxis: review of incidence, clinical predictors, and observation recommendations. ''Immunol Allergy Clin North Am''. 2015;35(2):313-326. PMID 25841553</ref> | |||
*Epinephrine is the ONLY first-line treatment — delays in administration increase mortality | |||
===Common Triggers=== | |||
*Foods (most common overall): peanuts, tree nuts, shellfish, fish, milk, eggs, wheat, soy | |||
*Medications: antibiotics (penicillin, cephalosporins), NSAIDs, neuromuscular blocking agents | |||
*Insect stings: Hymenoptera (bees, wasps, hornets, fire ants) | |||
*Latex | |||
*'''Exercise-induced anaphylaxis''' (sometimes food-dependent) | |||
*Idiopathic (~20% — no identifiable trigger) | |||
==Clinical Features== | ==Clinical Features== | ||
*Onset: minutes to hours after exposure (usually within 30 minutes) | |||
*Skin/mucosal (90%): urticaria, flushing, angioedema, pruritus | |||
* | *Respiratory (70%): laryngeal edema, stridor, bronchospasm, wheezing, dyspnea | ||
*Cardiovascular (45%): [[hypotension]], [[tachycardia]], distributive [[shock]], syncope, cardiac arrest | |||
*GI (45%): nausea, vomiting, abdominal cramps, diarrhea | |||
*Respiratory | *'''Neurologic''': anxiety, dizziness, altered mental status | ||
* | *'''Anaphylaxis can occur WITHOUT skin findings''' (~10-20% of cases) | ||
* | |||
* | |||
* | |||
=== | ===Diagnostic Criteria (Any ONE of Three)=== | ||
*Criterion 1: Acute onset with skin/mucosal involvement AND respiratory compromise OR hypotension | |||
* | *Criterion 2: Two or more systems involved rapidly after likely allergen: skin, respiratory, cardiovascular, GI | ||
*Criterion 3: Hypotension after exposure to known allergen (SBP <90 or >30% decrease from baseline) | |||
* | |||
==Differential Diagnosis== | ==Differential Diagnosis== | ||
*[[Angioedema]] (hereditary or ACE-inhibitor — no urticaria) | |||
*Vasovagal syncope (bradycardia; no urticaria/wheezing) | |||
*[[Asthma]] exacerbation | |||
*[[Urticaria]] alone (without systemic involvement) | |||
*Carcinoid syndrome, mastocytosis, scombroid fish poisoning | |||
*[[Anxiety]] / panic attack | |||
*[[Vocal cord dysfunction]] | |||
==Evaluation== | |||
*'''Anaphylaxis is a clinical diagnosis''' — do NOT delay treatment for labs | |||
*Serum tryptase: elevated supports diagnosis (draw within 1-3 hours of onset) | |||
**Normal tryptase does NOT exclude anaphylaxis | |||
**Useful for postmortem diagnosis and distinguishing from other causes | |||
*Monitor: continuous ECG, pulse oximetry, blood pressure | |||
*Consider: CBC, BMP, troponin (Kounis syndrome — allergic MI) | |||
== | ==Management== | ||
===Epinephrine (Cornerstone of Treatment)=== | |||
*Epinephrine 0.3-0.5 mg (1:1,000) IM in anterolateral thigh (vastus lateralis) | |||
=== | **Pediatric: 0.01 mg/kg (max 0.3 mg) IM | ||
* | **Repeat every 5-15 minutes as needed | ||
** | **'''Do NOT delay''' — there are NO absolute contraindications to epinephrine in anaphylaxis | ||
** | *If refractory or in shock: | ||
**Epinephrine infusion: 0.1-0.5 mcg/kg/min IV (mix 1 mg in 250 mL NS = 4 mcg/mL) | |||
**IV epinephrine bolus (only for cardiac arrest or refractory shock): 0.1 mg of 1:10,000 IV | |||
* | *IM > SC (faster absorption; SC absorption unreliable in shock) | ||
** | |||
** | |||
* | |||
=== | ===Adjunctive Therapies=== | ||
* | *IV fluids: aggressive NS bolus (1-2L in adults; 20 mL/kg in children) — distributive shock with massive third-spacing | ||
* | *Albuterol 2.5-5 mg nebulized for bronchospasm (does not replace epinephrine) | ||
** | *'''H1 antihistamine''': diphenhydramine 25-50 mg IV (treats urticaria/pruritus; does NOT treat life-threatening features) | ||
** | *H2 antihistamine: famotidine 20 mg IV (adjunctive) | ||
* | *Corticosteroids: methylprednisolone 125 mg IV or prednisone 1 mg/kg PO | ||
**Theoretical benefit in preventing biphasic reaction (limited evidence) | |||
**'''Do NOT rely on steroids as primary treatment''' (slow onset: 4-6 hours) | |||
*Glucagon 1-5 mg IV for patients on beta-blockers (resistant to epinephrine) | |||
== | ===Refractory Anaphylaxis=== | ||
*Epinephrine infusion + aggressive volume resuscitation | |||
*Vasopressin 1-2 units IV bolus for refractory hypotension | |||
*Glucagon for beta-blocker use | |||
*Consider methylene blue 1-2 mg/kg IV for refractory vasoplegia | |||
*Secure airway early if airway edema progressing (may require surgical airway) | |||
==Disposition== | ==Disposition== | ||
*Observe minimum 4-6 hours after last dose of epinephrine (biphasic reaction monitoring) | |||
* | *Extended observation (8-24 hours) if: | ||
**Severe initial reaction (hypotension, intubation) | |||
**History of biphasic reactions | |||
* | **Delayed presentation | ||
* | **Poor access to medical care | ||
* | *Discharge with: | ||
**Epinephrine auto-injector prescription (EpiPen or equivalent) — prescribe 2 devices | |||
**Antihistamine (diphenhydramine or cetirizine) for 3 days | |||
**Prednisone 40-60 mg PO daily × 3-5 days | |||
**Allergist referral | |||
**'''Written anaphylaxis action plan''' | |||
**Strict avoidance of trigger | |||
**'''Return precautions''': return immediately if symptoms recur | |||
==See Also== | ==See Also== | ||
*[[Angioedema]] | *[[Angioedema]] | ||
*[[Urticaria]] | |||
*[[Asthma]] | |||
*[[Shock]] | |||
*[[Epinephrine]] | |||
==References== | ==References== | ||
<references/> | <references/> | ||
*Lieberman P, et al. Anaphylaxis — a practice parameter update 2015. ''Ann Allergy Asthma Immunol''. 2015;115(5):341-384. PMID 26505932 | |||
*Cardona V, et al. World Allergy Organization anaphylaxis guidance 2020. ''World Allergy Organ J''. 2020;13(10):100472. PMID 33204386 | |||
*Simons FER, et al. World Allergy Organization guidelines for the assessment and management of anaphylaxis. ''World Allergy Organ J''. 2011;4(2):13-37. PMID 23268454 | |||
*Shaker MS, et al. Anaphylaxis — a 2020 practice parameter update. ''J Allergy Clin Immunol''. 2020;145(4):1082-1123. PMID 32001253 | |||
[[Category:Allergy and Immunology]] | |||
[[Category:Critical Care]] | [[Category:Critical Care]] | ||
Revisión actual - 09:23 22 mar 2026
Background
- Acute, life-threatening, systemic allergic reaction involving multiple organ systems
- IgE-mediated (type I hypersensitivity) in most cases; can also be non-IgE mediated (anaphylactoid)
- Biphasic reaction occurs in 5-20% of cases (recurrence 1-72 hours after initial reaction, usually within 8-10 hours)[1]
- Epinephrine is the ONLY first-line treatment — delays in administration increase mortality
Common Triggers
- Foods (most common overall): peanuts, tree nuts, shellfish, fish, milk, eggs, wheat, soy
- Medications: antibiotics (penicillin, cephalosporins), NSAIDs, neuromuscular blocking agents
- Insect stings: Hymenoptera (bees, wasps, hornets, fire ants)
- Latex
- Exercise-induced anaphylaxis (sometimes food-dependent)
- Idiopathic (~20% — no identifiable trigger)
Clinical Features
- Onset: minutes to hours after exposure (usually within 30 minutes)
- Skin/mucosal (90%): urticaria, flushing, angioedema, pruritus
- Respiratory (70%): laryngeal edema, stridor, bronchospasm, wheezing, dyspnea
- Cardiovascular (45%): hypotension, tachycardia, distributive shock, syncope, cardiac arrest
- GI (45%): nausea, vomiting, abdominal cramps, diarrhea
- Neurologic: anxiety, dizziness, altered mental status
- Anaphylaxis can occur WITHOUT skin findings (~10-20% of cases)
Diagnostic Criteria (Any ONE of Three)
- Criterion 1: Acute onset with skin/mucosal involvement AND respiratory compromise OR hypotension
- Criterion 2: Two or more systems involved rapidly after likely allergen: skin, respiratory, cardiovascular, GI
- Criterion 3: Hypotension after exposure to known allergen (SBP <90 or >30% decrease from baseline)
Differential Diagnosis
- Angioedema (hereditary or ACE-inhibitor — no urticaria)
- Vasovagal syncope (bradycardia; no urticaria/wheezing)
- Asthma exacerbation
- Urticaria alone (without systemic involvement)
- Carcinoid syndrome, mastocytosis, scombroid fish poisoning
- Anxiety / panic attack
- Vocal cord dysfunction
Evaluation
- Anaphylaxis is a clinical diagnosis — do NOT delay treatment for labs
- Serum tryptase: elevated supports diagnosis (draw within 1-3 hours of onset)
- Normal tryptase does NOT exclude anaphylaxis
- Useful for postmortem diagnosis and distinguishing from other causes
- Monitor: continuous ECG, pulse oximetry, blood pressure
- Consider: CBC, BMP, troponin (Kounis syndrome — allergic MI)
Management
Epinephrine (Cornerstone of Treatment)
- Epinephrine 0.3-0.5 mg (1:1,000) IM in anterolateral thigh (vastus lateralis)
- Pediatric: 0.01 mg/kg (max 0.3 mg) IM
- Repeat every 5-15 minutes as needed
- Do NOT delay — there are NO absolute contraindications to epinephrine in anaphylaxis
- If refractory or in shock:
- Epinephrine infusion: 0.1-0.5 mcg/kg/min IV (mix 1 mg in 250 mL NS = 4 mcg/mL)
- IV epinephrine bolus (only for cardiac arrest or refractory shock): 0.1 mg of 1:10,000 IV
- IM > SC (faster absorption; SC absorption unreliable in shock)
Adjunctive Therapies
- IV fluids: aggressive NS bolus (1-2L in adults; 20 mL/kg in children) — distributive shock with massive third-spacing
- Albuterol 2.5-5 mg nebulized for bronchospasm (does not replace epinephrine)
- H1 antihistamine: diphenhydramine 25-50 mg IV (treats urticaria/pruritus; does NOT treat life-threatening features)
- H2 antihistamine: famotidine 20 mg IV (adjunctive)
- Corticosteroids: methylprednisolone 125 mg IV or prednisone 1 mg/kg PO
- Theoretical benefit in preventing biphasic reaction (limited evidence)
- Do NOT rely on steroids as primary treatment (slow onset: 4-6 hours)
- Glucagon 1-5 mg IV for patients on beta-blockers (resistant to epinephrine)
Refractory Anaphylaxis
- Epinephrine infusion + aggressive volume resuscitation
- Vasopressin 1-2 units IV bolus for refractory hypotension
- Glucagon for beta-blocker use
- Consider methylene blue 1-2 mg/kg IV for refractory vasoplegia
- Secure airway early if airway edema progressing (may require surgical airway)
Disposition
- Observe minimum 4-6 hours after last dose of epinephrine (biphasic reaction monitoring)
- Extended observation (8-24 hours) if:
- Severe initial reaction (hypotension, intubation)
- History of biphasic reactions
- Delayed presentation
- Poor access to medical care
- Discharge with:
- Epinephrine auto-injector prescription (EpiPen or equivalent) — prescribe 2 devices
- Antihistamine (diphenhydramine or cetirizine) for 3 days
- Prednisone 40-60 mg PO daily × 3-5 days
- Allergist referral
- Written anaphylaxis action plan
- Strict avoidance of trigger
- Return precautions: return immediately if symptoms recur
See Also
References
- ↑ Lee S, et al. Biphasic anaphylaxis: review of incidence, clinical predictors, and observation recommendations. Immunol Allergy Clin North Am. 2015;35(2):313-326. PMID 25841553
- Lieberman P, et al. Anaphylaxis — a practice parameter update 2015. Ann Allergy Asthma Immunol. 2015;115(5):341-384. PMID 26505932
- Cardona V, et al. World Allergy Organization anaphylaxis guidance 2020. World Allergy Organ J. 2020;13(10):100472. PMID 33204386
- Simons FER, et al. World Allergy Organization guidelines for the assessment and management of anaphylaxis. World Allergy Organ J. 2011;4(2):13-37. PMID 23268454
- Shaker MS, et al. Anaphylaxis — a 2020 practice parameter update. J Allergy Clin Immunol. 2020;145(4):1082-1123. PMID 32001253
