S3C27 - Anaphylaxis, Acute Allergic Reaction, and Angioedema

Question 1

Anaphylaxis defn

Answer 1

• a serious allergic rxn that is rapid in onset and may cause death
• Clinical Criteria:

1. Acute onset (mins-hrs) with skin or mucosal involvement (hives, pruritus, flushing, swollen lips/tongue/uvula) associated with one of the following:
   
   • respiratory compromise (SOB, wheeze, stridor)
   • hypotension
   • organ dysfunction (hypotonia, syncope, incontinence)
2. 2 or more of the following that occur rapidly after exposure to a likely allergen:
   
   • skin or mucosal involvement
   • respiratory compromise
   • reduced BP
   • persistent GI Sx (cramps, vomiting)
3. Anaphylaxis should be suspected in any pt exposed to a known allergen and develop hypotension

-anaphylaxis refers to IgE and non-IgE mediated reactions

Question 2

Anaphylaxis: biphasic phenomenon

Answer 2

• occurs in 3-20% of pts
• peaks at 4-8h after initial exposure

Question 3

Anaphylaxis: DDx

Answer 3

• vasovagal
• myocardial ischemia
• arrhythmias
• status asthmaticus
• seizure
• epiglottitis
• hereditary angioedema
• FB obstruction
• carcinoid
• mastocytosis
• vocal cord dysfxn

Question 4

Anaphylaxis: treatment

Answer 4

First-Line:

• EPINEPHRINE - mixed alpha1 and beta2 agonist
  
  • alpha1 reduces mucosal edema and increases vasoconstriciton (BP)
  • beta2 provides bronchodilation
  • if no cardiovascular compromise then IM epi 0.3-0.5mg of 1:1000 q5-10min
  • epipen = 0.3 / epipen junior = 0.15mg (<30kg)
  • if cardiovascular compromise or refractory to IM tx then give IV infusion: 0.1mg IV of 1:10,000 over 5-10mins
• IV fluids - 1-2L bolus
• Oxygen - sats >90
• Airway - examine and act on this very early on
• decontamination - remove stinger, do not do gastric lavage for food allergen

Second Line:

• corticosertoids - all pts should receive steroids
  
  • methylprednisolone 80-125mg IV
    
    • 2mg/kg in children
  • hydrocortisone 250-500 mg IV
• antihistamines - histamine-1 blocker
  
  • diphenhydramine 25-50mg IV
  • can also give histamine2 blocker such as ranitidien or cimetidine
• asthma meds - ventolin
  
  • also atrovent and magnesium sulfate
• glucagon - use for anaphylactic pts who are on a BB and refractory to fluids and epi
  
  • dose: 1mg IV q5 mins until hypotension resolves followed by infusion of 5-16mcg/min

Question 5

Anaphylaxis: disposition

Answer 5

• if epi used - monitor for 2-4h
• d/c meds;
• benadryl Po for several days
• prednisone 40-60PO for several days
• epipen

Question 6

Urticaria

Answer 6

• hives
• cutaneous rxn marked by pruritic, erythremic wheals of varying size, fleeting
• erythema multiforme: targe skin lesions
• Tx: antihistamines and corticosteroids
• if refractory or severe, may consider epi
• addition of H2 blockers (ranitidine) may be useful if severe, chronic, unresponsive
• cold compresses

Question 7

Angiodedema

Answer 7

-Causes:

• ACEi (0.1-0.7% of pts taking ACEi)
• most cases mild and transient
• not useful: corticosteroids, antihistamines, epi
• mild swelling, no airway obstruction - observe in ED then d/c if swelling diminishes
• moderate swelling, dysphagia, resp distress –> admit for observation
• hereditary angioedema
• complement pathway defect - low levels of C1 esterase inhibitor or dysfunctional C1 esterase inhibitor with low levels of C4 b/w attacks
• episodes last from hours to days
• minor trauma can ppt the rxn
• epi, steroids, antihistamines are ineffective
• prophylaxis: androgens
• tx: C1 esterase inhibitor replacement, FFP

Question 8

Allergic Drug Rxns

Answer 8

• usually requires the drug to be protein-bound
• PCN accounts for 90% of drug rxns
• cross-reactivity with cephalosporins is 7%
• pts with anaphyl. to PCN should not rcv cephalo.