Prehospital and In-Hospital Treatment with Adrenaline and Related Prognosis in Anaphylaxis Patients

Introduction: Although intramuscular adrenaline is the recommended first-line treatment for anaphylaxis, not all patients receive this treatment. The consequences in daily clinical practice are sparsely described. This study aimed to investigate the treatment administered to anaphylactic patients and the related prognosis. Methods: A retrospective register-based study of patients with anaphylaxis referred to the allergy centre, Odense University Hospital (2019-2021). Each patient's medical records were reviewed for contacts with the emergency departments and the prehospital emergency medical service in the Region of Southern Denmark. The World Allergy Organization (WAO) grading system was used to assess the severity of prehospital and in-hospital anaphylaxis. Furthermore, the treatment administered to the patients was registered. Results: In total, 315 patients were included. The prehospital system had contact with 256 of these patients (two were released prehospitally following treatment and 12 patients had insufficient data to assess anaphylaxis). Of the remaining 242 patients, 115 had anaphylaxis prehospitally (WAO grades 3-5); 59% (67/115) received adrenaline. Among the 67 patients who received prehospital adrenaline, 9 patients (13.4%; 95% CI: 6.3-24.0%) still had anaphylaxis at arrival at the emergency department. Of the 48 patients that were not treated with prehospital adrenaline, 17 patients (35.5%; 95% CI: 22.1-50.5) had anaphylaxis at the arrival to the emergency department. Among the 127 patients without prehospital anaphylaxis (WAO grades 0-2), 22 patients (18.2%; 95% CI: 11.8-26.2%) who did not receive prehospital adrenaline had anaphylaxis at arrival to the emergency department, while none of the 6 patients treated prehospitally with adrenaline had anaphylaxis. Conclusion: Omission of prehospital adrenaline in anaphylactic patients is associated with more severe anaphylactic symptoms at arrival to the hospital. Adrenaline treatment remains suboptimal since only half of the patients received prehospital adrenaline and only 1 out of 4 patients, with clinical signs of anaphylaxis, received adrenaline inside the hospital.