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.