Anaphylaxis

1
Anaphylaxis

• Jack L-M Mutnick, MD
• University of Minnesota
• PGY-3

2
Terminology

• Anaphylaxis versus Anaphylactoid Reaction
• Anaphylaxis - Allergic, IgE-mediated, immediate
  hypersensitivity reaction to protein substances
• Anaphylactoid - Clinically indistinguishable, but
  ARE NOT IgE-mediated
• Presentation and management are virtually
  identical however hypotension and CV events are
  less common in Anaphylactoid reactions

3
Etiology

• 1. Insect stings/bites ? yellow jackets, wasps,
  hymenoptra, kissing bugs and imported fire ants
• 2. Foods ? peanuts, tree nuts, fish, seafood,
  berries, eggs
• 3. Drugs ? beta-lactams, NSAIDs, antineoplastic
  agents
• 4. Immunotherapy Injections
• 5. Radiocontrast Media
• 6. Latex

4
Food, Drugs

• Food allergy is highest in young children, but
  new food allergies can develop in adults,
  including the elderly
• Previous exposure to a suspect drug is required
  for IgE formation, but anaphylactoid reactions
  can occur upon first administration.
• Penicillins Most Common Cephalosporins also
  commonly-implicated ASA/NSAIDs 2nd most
  commonly implicated

5
Radiocontrast Media

• RCM causes anaphylactoid reactions that can be
  clinically indistinguishable from anaphylaxis
  however, there is no evidence for an immunologic
  mechanism
• Adverse reactions to conventional high osmolarity
  RCM is about 5-8
• Moderate reactions 1 (severe vomiting, diffuse
  urticaria, or angioedema)
• Life-threatening reactions lt 0.1

6
Diagnosis

• Diagnosis is clinical, and is supported by the
  following
• Acute onset of typical S/S
• Development of Sxs within minutes to a few hours
  after exposure to an agent known to provoke
  anaphylaxis
• Exclusion of other conditions that can mimic
  anaphylaxis

7
Clinical Findings

• Urticaria (hives) and angioedema ? occur in 88
  of patients. Often occur after period of
  generalized pruritus, flushing and a sense of
  impending doom
• Respiratory wheezing, SOB, or laryngeal edema
• Failure from airflow obstruction, cardiogenic or
  non-cardiogenic pulmonary edema, or ARDS
• CVS shock occurs in 30 of cases
• CV collapse from hypovolemia (increased vasc
  permeability and loss of up to 50 of blood
  volume), alterations in PVR, and myocardial
  depression
• GI nausea, vomiting, diarrhea, and abdominal or
  uterine cramping

8
Biphasic Reactions

• 1 20 may experience recurrence of Sxs after a
  period of recovery
• Most cases occur one to eight hours after initial
  presentation, but isolated reports with Sxs up
  to 72 hours later
• Thorough Lit Review found no distinguishing
  features of the 10 response to predict the
  occurrence of a 20 response but more common when
  the trigger was an oral ingestion

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Acute Management

• Due to the potentially life-threatening nature of
  anaphylaxis, prompt treatment is required!!
• 1. The first and most important therapy is
  epinephrine, IM or IV.
• There are NO ABSOLUTE CONTRAINDICATIONS to epi in
  the setting of anaphylaxis
• Give 0.3-0.5mg IM of 11000, preferably in
  ant/lat thigh, can repeat q3-5 prn if Sxs are
  severe prepare IV Epi
• 1b. Assess airway for impending obstruction ?
  intubation
• Can be difficult, so cricothyrotomy may be
  necessary
• 2. Rapid infusion of NS, 1-2 liters massive
  fluid shifts with severe loss of intravascular
  volume can occur

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Acute Management (cont)

• 3. IV Epi with severe Sxs and poor response to
  IM
• 0.1mL of 11000 dilution in 10cc NS ? 110,000.
  Run at 1-2 mL/min
• 4. Oxygen 100 O2
• 5. Albuterol Nebs
• 6. Anti-Histamines H1 blocker Benadryl 25-50mg
  IV, H2 blocker Ranitidine 50mg IV
• 7. Corticosteroids Not helpful in the treatment
  of acute anaphylaxis. However, efficacious in
  preventing late phase reactions in other
  IgE-mediated disease, so given with the goal of
  preventing or ameliorating biphasic reactions.
  Solumedrol 125mg IV or Decadron 20mg IV

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Other Critical Components

• Two large bore peripheral IVs
• If possible, the inciting agent should be removed
• Continuous hemodynamic and pulse-ox monitoring
• If patient tolerates, place in recumbent position
  with LE elevated to maximize perfusion of vital
  organs

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Observation after Anaphylaxis

• No consensus regarding optimal amount of time to
  observe after successful treatment
• Mild to Moderate severity 8 hours might be
  sufficient, but up to 20 may experience
  recurrent Sxs, so clinical judgment is
  imperative
• All patients should be informed upon discharge
  that recurrent Sxs are possible for up to three
  days