Due to the increased likelihood of allergic
reactions in atopic patients, it is important that a complete history
of known and suspected allergies as well as allergic-like symptoms,
e.g., rhinitis, bronchial asthma, eczema and urticaria, be obtained
prior to any medical procedure utilizing these products. A mild allergic
reaction would most likely include generalized pruritus, erythema
or urticaria. Such reactions will generally respond to an antihistamine
such as 50 mg of diphenhydramine, or its equivalent. In the rarer,
more serious reactions, laryngeal edema, bronchospasm or hypotension
could develop. Severe reactions which may require emergency measures
are often characterized by peripheral vasodilation, hypotension, reflex
tachycardia, dyspnea, agitation, confusion and cyanosis progressing
to unconsciousness. Treatment should be initiated immediately with
0.3 to 0.5 mL of 1:1000 epinephrine subcutaneously. If bronchospasm
predominates, 0.25 to 0.50 grams of intravenous aminophylline should
be given slowly. Appropriate vasopressors might be required. Adrenocorticosteroids,
even if given intravenously, exert no significant effect on the acute
allergic reactions for a few hours. The administration of these agents
should not be regarded as emergency measures for the treatment of
allergic reactions. All levels of allergic reactions are extremely
rare with this product. Apprehensive patients may develop weakness,
pallor, tinnitus, diaphoresis and bradycardia following the administration
of any diagnostic agent. Such reactions are usually non-allergic in
nature and are best treated by having the patient lie flat for an
additional 10 to 30 minutes under observation.