When Safety Barriers Fail: Paracetamol-Induced Anaphylaxis Under General Anesthesia Despite Multiple Allergy Warnings.

Intravenous paracetamol-induced anaphylaxis is uncommon but can be life-threatening during general anesthesia. The principal lesson of this case, however, was not the allergic reaction itself but the failure of multiple perioperative safety barriers that allowed the administration of a suspected allergen. We report the case of a 50-year-old woman who developed circulatory collapse, with systolic blood pressure decreasing from approximately 100 mmHg to 60 mmHg before becoming unmeasurable, approximately five minutes after inadvertent intravenous paracetamol administration during breast surgery under general anesthesia. Paracetamol had been identified preoperatively as a suspected allergen, documented by multiple healthcare professionals, recorded on handwritten anesthesia documents, and displayed prominently in the operating room. However, this information was not transformed into shared situational awareness or effective team action. The attending locum anesthesiologist was unable to access the electronic medical record (EMR) before anesthesia induction, and intravenous paracetamol remained available in the operating room despite institutional policy requiring removal or clear identification of suspected allergenic drugs. Prompt treatment with epinephrine, fluid resuscitation, vasopressors, and adjunctive anti-allergic medications resulted in complete recovery without neurological sequelae. Elevated serum histamine and β-tryptase concentrations, together with postoperative skin prick testing, supported intravenous paracetamol as the most likely trigger of perioperative anaphylaxis. Institutional review identified interacting human and system factors rather than a single individual error. Major contributing factors included incomplete allergy alert registration, ineffective multidisciplinary communication, failure of the WHO Surgical Safety Checklist to establish shared situational awareness, incomplete implementation of fail-safe drug management, and excessive reliance on digital information systems. Corrective actions included mandatory multidisciplinary allergy verification, physical removal or segregation of suspected allergenic drugs before patient entry into the operating room, and reinforcement of checklist-based communication. This case demonstrates that digital technologies can support patient safety but cannot replace effective teamwork, shared situational awareness, or fail-safe system design. Sustainable perioperative safety requires systems that anticipate inevitable human error and prevent those errors from reaching the patient.