2025 FSA Podium and Poster Abstracts

Introduction: Anaphylaxis is a life-threatening hypersensitivity reaction that may rapidly occur after exposure to certain medications, including antibiotics. Ceftriaxone, a third generation cephalosporin, is an antibiotic widely used in clinical practice and for preoperative antibiotic prophylaxis. Following penicillin, cephalosporins are the beta-lactam antibiotics most commonly associated with IgE-mediated reactions. Sensitization to cephalosporins has been linked to prior exposure to shared determinants with penicillin, as well as to specific cephalosporin haptens. Anaphylaxis following a second exposure to cephalosporins is exceedingly rare. Thus, the risk of anaphylaxis upon re-exposure is often underestimated in patients with no previous allergic reaction. This case describes a patient who experienced anaphylactic shock following second exposure to ceftriaxone as a preoperative antibiotic.

Methods/Case Report: A 30-year-old female with no past medical history presented via EMS as an outside hospital transfer for further neurosurgery evaluation. Prior to her admission, she had a 2 day history of altered mental status and somnolence. At the outside hospital, a CT brain was obtained showing severe hydrocephalus secondary to an arachnoid cyst. An external ventricular drain was placed before hospital transfer. Upon arrival, she underwent additional surgical intervention for endoscopic creation of a ventriculostomy. 

Induction was uneventful. However, during antibiotic (vancomycin and ceftriaxone) administration, the patient became hypotensive, requiring 1200mcg of phenylephrine and 1U of vasopressin before a phenylephrine infusion was started. The lowest blood pressure recorded during this period was 79/58. The patient recovered postoperatively without additional vasopressin and no cutaneous findings were noted. 

Seven days later, the patient returned for ventriculoperitoneal shunt placement. Induction was uneventful. However, upon ceftriaxone administration, the patient became profoundly hypotensive (BP 56/41) and cutaneous changes were noticed. The patient had a rash on her torso, back, neck, groin, and leg areas. At this time, the patient was given a fluid bolus, diphenhydramine, famotidine, and vasopressor support (norepinephrine drip). A blood sample was obtained and sent for serum tryptase. Auscultation of the lungs did not reveal wheezing and there was no change in peak inspiratory pressure. It should be noted that these changes occurred before vancomycin administration, therefore excluding vancomycin as the offending agent. Intraoperatively, the patient was weaned off of vasopressor support after intervention and was extubated without complications. She was transported to the neurosurgical intensive care unit for post-operative monitoring and was discharged days later.

Conclusion: Anaphylaxis after second exposure to ceftriaxone is extremely rare, but can be fatal. This patient may have had a missed anaphylactic reaction during her previous anesthetic encounter with ceftriaxone. Additionally, while serum tryptase can help diagnose anaphylaxis, the patient’s normal tryptase level (7.8, reference normal <11) lacked a baseline tryptase for comparison, and a normal level does not exclude anaphylaxis. 

Only one other case of anaphylaxis after second exposure to ceftriaxone has been reported. This case highlights the importance of recognizing the potential for delayed or second-time hypersensitivity reactions, even in patients with prior, seemingly uneventful exposures.