Angioedema

The life-threatening anaphylactic response of a sensitized human appears within minutes after administration of specific antigen and is manifested by respiratory distress often followed by vascular collapse or by shock without antecedent respiratory difficulty. Cutaneous manifestations exemplified by pruritus and urticaria with or without angioedema are characteristic of such systemic anaphylactic reactions. Gastrointestinal manifestations include nausea, vomiting, crampy abdominal pain, and diarrhea.

The angioedema resulting in death by mechanical obstruction occurs in the epiglottis and larynx, but the process is also evident in the hypopharynx and to some extent in the trachea; on microscopic examination there is wide separation of the collagen fibers and the glandular elements; vascular congestion and eosinophilic infiltration are also present.

Ancillary agents such as the antihistamine diphenhydramine, 50 to 100 mg intramuscularly or intravenously, and aminophylline, 0.25 to 0.5 g intravenously, are appropriate for urticaria-angioedema and bronchospasm, respectively. Intravenous glucocorticoids are not effective for the acute event but may alleviate later recurrence of bronchospasm, hypotension, or urticaria. Furthermore, in a syndrome termed idiopathic anaphylaxis with recurrent angioedema of the upper airways, glucocorticoid administration may be beneficial by reducing the frequency of attacks and/or the severity of episodes.