Updated: Jan 25
Immediate hypersensitivity reactions, which may or may not be antigen-specific, can result in local reactions, such as urticaria, and systemic reactions characterized by sudden dyspnea or hypotension. Numerous agents can cause these reactions, such as vaccines, wormers, antibiotics, and anesthetics. Osmotically active or highly charged agents that stimulate mast-cell degranulation by cell membrane perturbation are associated with non-immunologically triggered anaphylactoid reactions. Anaphylaxis is mediated by IgG antibodies.
Therapy should limit, leukotriene, and platelet formation, moderate platelet degranulation, and the complement and coagulation cascades to improve tissue oxygenation and limit the chemoattraction of additional inflammatory cells. The allergen should be eliminated. Priorities are venous access and airway patency. Oxygen administration, cardiac monitoring, and large-volume fluid therapy are recommended. Epinephrine counteracts hypotension and reverses bronchoconstriction. Alpha-adrenergic agonists, such as phenylephrine, improve blood pressure and decrease edema.