Perioperative Anaphylaxis - Recognition and Epinephrine First

Key Points

• Perioperative anaphylaxis may lack visible hives.
• Sudden hypotension and bronchospasm after a new exposure should trigger immediate concern.
• Epinephrine is first-line treatment.
• Large-volume crystalloid may be required because of vasodilation and capillary leak.
• Antihistamines and steroids are adjuncts, not resuscitation drugs.
• Document the exact exposure timeline for later allergy testing.
• Acute and baseline tryptase support diagnostic investigation but never delay treatment.
• Future anesthesia should avoid suspected agents until formal evaluation is complete.

Algorithm

1. Recognize sudden hypotension, bronchospasm, airway edema, or collapse and call for help.
2. Stop suspected trigger exposures and give 100% oxygen.
3. Give epinephrine promptly using monitored IV titration by experienced anesthesia clinicians or IM dosing when appropriate.
4. Give rapid IV crystalloid and repeat epinephrine or start infusion for persistent shock.
5. Treat persistent bronchospasm with inhaled beta agonist and manage airway edema.
6. Obtain timed tryptase samples after immediate stabilization.
7. Observe or admit according to severity.
8. Refer for perioperative allergy investigation with complete drug and exposure record.

Clinical Synopsis & Reasoning

Anaphylaxis under anesthesia can be difficult to recognize because the patient cannot report itching, throat tightness, or dizziness and the surgical drapes hide skin findings. Sudden unexplained hypotension, tachycardia or bradycardia, bronchospasm, increased airway pressure, desaturation, urticaria, flushing, or cardiovascular collapse should raise suspicion. Skin signs can be absent, particularly in severe shock.

Review the timeline of every drug and exposure immediately before deterioration. Common triggers vary by country and include prophylactic antibiotics, neuromuscular blocking agents, chlorhexidine, latex, colloids, dyes, and other perioperative medications. Rule out other immediate causes such as hemorrhage, high neuraxial block, tension pneumothorax, venous air embolism, myocardial event, or mechanical ventilation problem, but do not delay epinephrine when anaphylaxis is strongly suspected.

Turn off or discontinue suspected infusions and remove relevant exposure when possible. Call for additional anesthesia and surgical help. Give 100% oxygen and secure the airway if not already controlled. Capnography and airway pressures help distinguish bronchospasm from circuit obstruction. Hypotension can be profound because of vasodilation and capillary leak, requiring both epinephrine and rapid IV crystalloid.

Treatment Strategy & Disposition

Epinephrine is first-line treatment. In the anesthetized patient with IV access and continuous monitoring, small titrated IV epinephrine boluses may be used by experienced anesthesia clinicians for hypotension, while severe cardiovascular collapse requires larger resuscitative dosing or infusion according to crisis protocols. Outside such a monitored IV setting, IM epinephrine remains the safer standard. Repeated dosing and an infusion may be required.

Administer rapid isotonic crystalloid because intravascular volume can fall dramatically. Treat persistent bronchospasm with inhaled beta-agonists after epinephrine. H1 antihistamines and corticosteroids are adjuncts for cutaneous or later symptoms and should not delay resuscitation. For refractory shock, use an epinephrine infusion and consider additional vasopressors under expert management. Patients taking beta blockers may respond poorly to catecholamines; glucagon can be considered in refractory cases.

Obtain serum tryptase samples after stabilization according to local timing protocol, typically including an early acute sample and a later baseline sample. Do not let blood sampling delay treatment. Admit patients with severe reactions for appropriate monitoring. Refer every suspected perioperative anaphylaxis case for specialist allergy investigation with a complete anesthesia record, exact timing of exposures, and list of agents to avoid until testing clarifies the culprit.

Epidemiology / Risk Factors

• Antibiotics and neuromuscular blocking drugs are frequent perioperative triggers.
• Chlorhexidine has become increasingly recognized as a cause.
• Perioperative anaphylaxis is uncommon but can cause rapid cardiovascular collapse.
• Previous uneventful exposure does not exclude IgE-mediated reaction on re-exposure.

Investigations

Common Triggers

Pharmacology

Prognosis / Complications

• Prompt epinephrine and circulatory support usually produce recovery.
• Delayed recognition increases risk of hypoxic brain injury and cardiac arrest.
• Correct culprit identification reduces risk during future anesthesia.
• Many patients labeled broadly 'allergic to anesthesia' can later receive safe targeted alternatives after specialist testing.

Patient Education / Counseling

• Tell the patient that the suspected reaction requires formal allergy investigation.
• Provide written names of all possible culprit exposures and safe medications used afterward when known.
• Advise the patient to show the allergy report before future surgery.
• Explain that a negative skin rash does not make the event less serious.
• Medical-alert identification may be useful once the culprit is confirmed.

Notes

The diagnostic work continues after the crisis. A nonspecific chart label such as "anesthetic allergy" can unnecessarily restrict future care and still fail to identify the actual culprit. The allergy referral should receive the full anesthesia chart, antibiotic timing, skin preparations, devices, and all administered drugs.

Crisis handbooks are valuable because severe anaphylaxis creates high cognitive load. Teams should know where the local anaphylaxis algorithm and epinephrine infusion instructions are before an event occurs.

References

1. Association of Anaesthetists Quick Reference Handbook: Anaphylaxis — Link
2. Association of Anaesthetists Quick Reference Handbook — Link