Contrast media delayed reactions

Numerous positive delayed skin tests in patients with contrast medium-induced non-immediate skin reactions have been reported when the patients were tested with the culprit contrast medium [summarized in 1]. In a large European multicenter study, 37% of patients with non-immediate reactions were positive in delayed IDEs and/or patch tests [13]. The majority of the patients also reacted to the culprit contrast medium and also to other, structurally similar RCM. Notably, in more than 30% of those skin test-positive patients a RCM had been administered for the first time. Thus, there is a lack of a sensitization phase. Again it may be hypothesized that these previously non-exposed patients may have already been sensitized. Different patterns of RCM cross-reactivity indicate that several chemical entities could be involved. No positive skin tests have been obtained with other contrast medium excipients, such as ethylenediaminetetraacetic acid (EDTA), and only rarely patients have been found to react to inorganic iodide. 

Delayed reactions are generally benign, but not always. In a Japanese study, the incidence of delayed reactions was investigated in 6764 patients who received the low-osmolar non-ionic contrast medium iohexol intravenously (33). Delayed reactions (rash, pruritus, nausea, vomiting, fever, headache, and others) occurred in 192 patients (2.8%). There were no severe delayed reactions. A history of allergy and hay fever were risk factors for delayed adverse reactions. 

The authors attributed these events to a severe delayed reaction to the contrast medium, manifesting as prolonged hypotension. 

Hearing disturbances attributable to contrast agents are extremely rare. The hearing loss in this patient developed more than 1 hour after the injection of iohexol, without any evidence of other causes. The authors suggested that the hearing disturbance might have been attributable to cochlear impairment caused by a delayed allergic reaction or chemical toxicity of the contrast medium. 

The authors suggested that the skin manifestations had been due to graft-versus-host disease triggered by the contrast medium and not a type-IV immunological reaction. Skin biopsy in one of the patients showed typical features of graft-versus-host disease. In addition, the reactions in these patients lasted for longer than one would expect in simple delayed reactions with skin manifestations, which usually resolve within 7-10 days. 

Munechika H, Hiramatsu Y, Kudo S, Sugimura K, Hamada C, Yamaguchi K, Katayama H. Delayed adverse reactions to nonionic contrast medium (iohexol) in IV use multicentric study. Acad Radiol 2002 9(Suppl 1) S69-71. 

Erdmann S, Roos T, Merk HF, Grussendorf-Conen Eli, Rubben A, Dahl T. Delayed hypersensitivity reaction to the non-ionic contrast medium ioversol. H G Z Hautkr 2000 75 169-71. 

Evidence that immediate reactions to a contrast medium is IgE antibody mediated is based largely on skin test results with or without tryptase measurements and very occasionally serum IgE and basophil activation tests. Delayed reactions mainly manifest as exan-thematons skin eruptions. They are mediated by antigen-specific effector T cells with as yet poorly defined cytokine involvement. 

Small particles of coke made in the process circulate in a fluidized state between the vessels and are the heat transfer medium. Thus the process requires no high-temperature preheat furnace. Fluid coking is carried out at essentially atmospheric pressure and temperatures in excess of 485°C (900°F) with residence times on the order of 15-30 seconds. The longer residence time is in direct contrast to the delayed coking process, in which the eoking reactions are allowed to proceed to completion. This is evident... 

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