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- Potentially lethal allergic reaction
- Rapid onset, from minutes to hours after exposure
- Generally requires a prior sensitization to antigen; can occur on first exposure due to cross-reactivity among drugs/products
- Pathophysiology: type I hypersensitivity reaction involving multiple organ systems
- IgE-mediated mast cell degranulation with release of stored histamine, proteases, proteoglycans, and platelet-activating factor (PAF); followed by production of proinflammatory prostaglandins and leukotrienes
- Histamine, prostaglandin, and leukotriene receptors elicit changes in vascular permeability and tone, bronchial smooth muscle contraction, and coagulability, and may produce angioedema, urticaria, bronchoconstriction, and DIC; PAF can further contribute to anticoagulation and constriction of bronchial smooth muscle
- Clinically indistinguishable from anaphylactoid reactions, that is, “pseudoanaphylaxis” (non-IgE-mediated, no prior sensitization, nonspecific histamine release)
- Incidence 1/3,500–20,000 anesthetic procedures; higher mortality rate in perioperative anaphylaxis than anaphylaxis in other settings
- Early signs often unrecognized and undertreated in anesthetized patients; cutaneous signs masked by surgical draping
- May be biphasic with recurrence of symptoms 8–10 and up to 72 hours after initial occurrence
- Requires immediate treatment and resuscitation
- Death from upper airway edema, bronchial obstruction, circulatory collapse
- Comorbidities with high risk of poor outcomes: asthma/COPD and CV disease
- Four grades:
Cutaneomucosal generalized signs: rash, urticaria
Moderate multivisceral involvement: hypotension, tachycardia, bronchial hyperreactivity
Severe, life-threatening multivisceral involvement: MI, severe bronchospasm
Cardiorespiratory arrest
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NB: Cutaneous signs can be delayed or absent.
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- Elicit risk factors for allergy to medications, latex, foods
- If patient had an anaphylactic reaction during a prior anesthetic:
- Prefer regional if possible
- If GA, avoid NMBAs and histamine-releasing medications (e.g., morphine); use propofol, inhalation agents; prefer non-histamine-releasing opioids (fentanyl, hydromorphone)
- No preoperative tests have been shown to reliably identify medications to avoid
- No benefit in premedicating ...