Anaphylaxis - NYSORA

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Learning objectives

  • Recognize signs and symptoms of anaphylaxis
  • Define the grade and management of anaphylaxis

Definition and mechanisms

  • Anaphylaxis is a severe and potentially life-threatening allergic reaction that develops suddenly and requires immediate medical attention
  • The most common anaphylactic reactions are to foods, insect stings, medications, and latex
  • Tissues in different parts of the body release histamine and other substances and this causes the airways to tighten

Signs and symptoms

  • Sweating
  • Rash/hives
  • Nausea
  • Vomiting or diarrhea
  • Wheezing/shortness of breath due to airway constriction or swollen throat
  • Fainting with loss of consciousness
  • Angioedema
  • Hypotension
  • Tachycardia

Anaphylaxis grades

Grade IErythema
Grade IIErythema
BronchospasmModerate Hypotension
Grade IIIErythema
Severe BronchospasmLife-threatening Hypotension
Tachycardia or bradycardia with or without Intraoperative arrhythmias
Grade IVErythema
Respiratory arrestPeripartum cardiac arrest


anaphylaxis, culprit drug, trigger, maintain airway, epinephrine, fluids, grade of anaphylaxis, laboratory test, tryptase, histamine, transfer to ICU, allergist

Treatment of anaphylaxis grades

Intravenous epinephrineIntravenous fluids (crystalloids)
Grade IIStart with 20 μg bolus IV
Inadequate response after 2 minutes: escalate to 50 μg and repeat every 2 minutes
If no i.v. access: administer 300 μg i.m.
500 ml rapid bolus
Review response
Repeat as needed
Grade III50 μg bolus or 100 μg bolus IV if inadequate response to other vasopressors or bronchodilators
Inadequate response at 2 min: escalate to 200 μg and repeat every 2 minutes
1L rapid bolus
Review response
Repeat as needed up to 30 ml kg-1
Grade IV500 mcg IM/IV over 3 minutes followed by a continuous infusion (4-10 µg/min)
Repeat as per ALS guidelines
Suggest ECM if systolic <50 mmHg or endtidal CO2 <3 kPa (20 mmHg)
Refractory anaphylaxis: inadequate response >10 min after symptom onsetDouble epinephrine dose
If response after more than three boluses of epinephrine IV is inadequate, add epinephrine infusion 0.05–0.1 μg/kg/min

Hypotension - consider adding:
Vasopressin 1–2 IU with or without infusion 2 IU/h
Glucagon 1–2 mg (if on beta-adrenergic receptor blockers)
Norepinephrine infusion 0.05–0.5 μg/kg/min
Suggest ECLS: where available

Bronchospasm - add: inhaled or i.v. bronchodilators (β2-agonist such as salbutamol or albuterol)
ALS, advanced life support; ECLS, extracorporeal life support; ECM, external cardiac massage.

Suggested reading

  • Garvey LH, Dewachter P, Hepner DL, et al. Management of suspected immediate perioperative allergic reactions: an international overview and consensus recommendations. Br J Anaesth. 2019;123(1):e50-e64.
  • Dewachter P, Mouton-Faivre C, Emala CW. Anaphylaxis and anesthesia: controversies and new insights. Anesthesiology. 2009;111(5):1141-1150. 

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