Anaphylactoid shock induced by radiographic contrast material
C. Initiate venoarterial extracorporeal membrane oxygenation
In the present case, the patient—an allergist and a coauthor of this article—developed acute shock during PCI that was unresponsive to volume resuscitation and vasopressors, suggesting distributive pathophysiology. After excluding procedure-related causes such as stent thrombosis, coronary dissection or perforation, and retroperitoneal hemorrhage (not applicable to this case given transradial access), radiographic contrast material (RCM)–induced anaphylactoid shock should be considered with initiation of empirical treatment.
Anaphylaxis is a systemic allergic response involving the release of mediators from mast cells and basophils that leads to a spectrum of clinical manifestations ranging from mild urticaria to circulatory collapse with cardiac arrest. Notably, this was the patient’s first exposure to RCM; thus, the allergic reaction was classified as non–IgE mediated (ie, anaphylactoid).1 Common symptoms such as urticaria may present within a few minutes of exposure, whereas severe manifestations including angioedema with respiratory failure or cardiac arrest are seen in 0.01% to 0.04% of patients, with death occurring in approximately 1 per 100 000 exposures. Fatal reactions usually occur within 5 minutes of exposure and rarely after 20.2