5. Clinical Features
Majority: signs and symptoms begin suddenly,
often within 60 minutes of exposure
biphasic phenomenon
3-20% of patients
caused by a second phase of mediator release,
peaking 4-8 hours after the initial exposure and
exhibiting itself clinically 3-4 hours after the initial
clinical manifestations have cleared
late-phase allergic reaction
primarily mediated by the release of newly generated
cysteinyl leukotrienes, the former slow-reacting
substance of anaphylaxis
11. Disposition and Follow-Up
Admission/Discharge
Admission to hospital is rare
All unstable patients with anaphylaxis refractory
to treatment or where airway interventions were
required should be admitted to the intensive
care unit.
Patients who receive epinephrine should be
observed in the ED, but the duration of
observation is based on experience rather than
clear evidence.
12. Disposition and Follow-Up
Admission/Discharge
If patients remain symptom free after
appropriate treatment following 4 hours of
observation, the patient can be safely
discharged home.
prolonged observation periods should be
considered in patients with a past history of
severe reaction and those using -blockers
15. Urticaria
Treatment of urticarial reactions is generally
supportive and symptomatic, with attempts to
identify and remove the offending agent.
Antihistamines, with or without corticosteroids,
are usually sufficient, although epinephrine can
be considered in severe or refractory cases.
The addition of a histamine-2 receptor blocker,
such as ranitidine, may also be useful in more
severe, chronic, or unresponsive cases.
16. Angioedema
Angioedema of the tongue, lips, and face has
the potential for airway obstruction.
Management is supportive, with special
attention to the airway, which can become
occluded rapidly and unpredictably.
Epinephrine, antihistamines, and steroids are
often still used, but benefits have not been
clearly demonstrated.
17. Angioedema
Patients with mild swelling and no evidence of
airway obstruction can be observed in the ED
and discharged if swelling diminishes.
Patients with moderate to severe swelling,
dysphagia, or respiratory distress are best
admitted for close observation.