Introduction
Anaphylaxis, a form of hypersensitive reaction, can be life-threatening at any age and in either sex. A biphasic reaction is defined as the recurrence of anaphylactic symptoms without re-exposure to the allergen within 72 hours of resolution of the initial reaction.1 Biphasic reactions reportedly occur in 4.6% of patients with anaphylaxis.1Current anaphylaxis guidelines therefore recommend continuous observation for several hours or longer after resolution of the initial reaction.2–5 In these guidelines, intramuscular injection of adrenaline is the recommended first-line treatment, glucocorticoids, histamine-1 receptor blockers, and beta 2-adrenergic receptor stimulants being second-line treatments.2–5 However, there is limited available evidence for the effects of second-line treatments on symptoms and rates of biphasic reactions in patients with anaphylaxis.
Glucocorticoids inhibit inflammatory responses by suppressing the function of mast cells and are thought to prevent biphasic reactions in patients with anaphylaxis.6 Recent retrospective cohort studies have failed to show any preventive effects of glucocorticoids on biphasic reactions.7,8However, the cohorts of these studies included patients with various types of allergy, including mild to moderate anaphylaxis. Given that glucocorticoids can ameliorate allergic inflammatory responses, it is possible that they prevent biphasic reactions, especially in patients with severe anaphylaxis.
Therefore, in this retrospective observational study using a national inpatient database in Japan, we aimed to examine the effect of glucocorticoids on rates of biphasic reactions in patients with severe anaphylaxis treated with adrenaline.