Classic and atypical anaphylaxis presentations

anaphylaxis atypical anaphylaxis Jun 04, 2026

Perioperative anaphylaxis is one of the most time-critical emergencies encountered in perianaesthesia practice. While many of us are familiar with the “classic” signs, not every patient follows the expected pattern.

Classic anaphylaxis is caused by the rapid release of inflammatory mediators from mast cells and basophils. This can lead to widespread vasodilation, increased capillary permeability and bronchoconstriction. In the perioperative setting, symptoms often develop within minutes of exposure to the triggering agent. Common triggers include antibiotics, neuromuscular blocking agents, chlorhexidine and latex.

The challenge is that some patients present atypically. Skin changes such as urticaria or flushing may be absent, delayed, or hidden beneath drapes. In some cases, profound hypotension, bradycardia, cardiovascular collapse, or unexplained difficulty ventilating may be the only visible clues. Rarely, underlying conditions such as mastocytosis may contribute to unusual presentations.

🔹 Classic presentations often include hypotension, tachycardia, bronchospasm and skin manifestations.

🔹 Cutaneous signs may not always be present during severe reactions.

🔹 Sudden cardiovascular collapse without an obvious cause should raise suspicion for anaphylaxis.

🔹 Elevated mast cell tryptase can support diagnosis and guide further investigation.

🔹 Atypical presentations may warrant assessment for underlying mast cell disorders.

For perianaesthesia nurses, recognising that anaphylaxis does not always look "textbook" is essential. Early recognition, prompt escalation, administration of adrenaline as prescribed, aggressive fluid resuscitation and clear communication with the multidisciplinary team can significantly influence outcomes.

When the clinical picture does not fit neatly into expectations, trust your assessment. Sometimes the absence of classic signs is the very clue that something significant is occurring.

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References

Bridgman, D.E., Clarke, R.C., Sadleir, P.H.M., Stedmon, J.J. & Platt, P.R. (2013). Systemic Mastocytosis Presenting as Intraoperative Anaphylaxis with Atypical Features: A Report of Two Cases. Anaesthesia and Intensive Care.

Dewachter, P. & Savic, L. (2019). Perioperative Anaphylaxis: Pathophysiology, Clinical Presentation and Management. BJA Education.

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