What is anaphylaxis?
A serious, rapid-onset allergic reaction involving ≥2 organ systems or hypotension after allergen exposure; can be life-threatening.
What causes the symptoms of anaphylaxis?
IgE-mediated mast cell degranulation → histamine and other mediators → vasodilation, bronchoconstriction, increased vascular permeability.
What are common triggers of anaphylaxis?
- Foods (peanuts, shellfish, eggs, milk)
- Insect stings
- Medications (penicillin, NSAIDs)
- Latex
What are the skin findings in anaphylaxis?
Urticaria, flushing, angioedema
What respiratory symptoms occur in anaphylaxis?
Wheezing, stridor, dyspnea, throat tightness
What cardiovascular findings occur in anaphylaxis?
Hypotension, tachycardia, syncope
What GI symptoms can be seen in anaphylaxis?
Nausea, vomiting, diarrhea, cramping
How is anaphylaxis diagnosed?
Clinical diagnosis; ≥2 organ systems involved after exposure OR hypotension after known allergen.
What is the first-line treatment for anaphylaxis?
IM epinephrine (0.3–0.5 mg IM)
(Thigh is more effective than deltoid)
What adjunctive medications are used in anaphylaxis treatment?
H1 blocker: Diphenhydramine
H2 blocker: Famotidine
Steroids: Methylprednisolone (reduce risk of biphasic reaction)
Bronchodilators: Albuterol (for bronchospasm)
Why are IV fluids important in anaphylaxis?
To treat distributive shock due to vasodilation and capillary leak; use isotonic crystalloids (e.g., 1–2 L NS bolus)
What drug can be used for anaphylaxis in patients on beta blockers?
Glucagon 1 mg IV bolus followed by infusion; it bypasses beta receptors to increase cAMP and improve hypotension.
How long should anaphylaxis patients be observed after treatment?
4–6 hours minimum; 24 hours if severe or biphasic risk
What prescription should all anaphylaxis patients receive on discharge?
Epinephrine auto-injector
What is a biphasic anaphylactic reaction?
Return of symptoms hours after initial resolution without further exposure.
What patient-reported symptoms should raise suspicion for anaphylaxis?
“My throat feels tight/itchy”
“My lips feel swollen”
“I feel like I’m going to pass out”
“I can’t catch my breath”
“I have a weird rash and I feel dizzy”
What is a differential diagnosis for anaphylaxis?
Vasovagal syncope – bradycardia, no rash
Septic shock – infection source, fever
Asthma exacerbation – no hypotension, isolated wheeze
Angioedema (non-anaphylactic) – slow onset, no urticaria/hypotension
Carcinoid syndrome – flushing, diarrhea, but not sudden-onset multi-system reaction
Panic attack – no rash, no hypotension
Food poisoning – GI only, no urticaria or respiratory compromise
What medications can be used to reduce the effects of angioedema caused by ACE-I or hereditary angioedema?
- Icatibant
- Ecallantide
- Fresh frozen plasma
Which medications can be added for refractory bronchoconstriction?
- Ipratroprium bromide 250mcg
- Magnesium 2g infused over 20 mins
