Contrast media adverse reactions

Extravasation of barium sulfate iato the peritoneal cavity through a perforated GI tract can produce serious adverse reactions. When a perforation is suspected, the use of a water-soluble iodinated contrast medium is iadicated. In this case, oral or rectal administration of sodium or meglumine-sodium salts of diatrizoic acid (6) and oral use ofiohexol (11) are the preferred procedures. 

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. 

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. 

The use of premedication with steroids and Hi and Hg histamine receptor blockers can significantly reduce the adverse reactions to high osmolality contrast media. There are suggestions to extend their use to modify even the reactions to low osmolality contrast media. Pretesting of contrast media reactors by injecting 1 mL of the nonionic contrast medium has also been reported (539). 

There were adverse events in 241 patients (2.7%), and the incidence was significantly higher with iomeprol (3.9%) and iopromide (3.5%), in patients aged 59 years or less (4.5%) compared with those 60 years and over (1.9%), during the first period of the study (3.5%) compared with the last period (2.3%), in those with a past history of adverse reactions to contrast media (11%) and in patients receiving a contrast medium for first... 

A curious seasonal variation in the occurrence of late adverse skin reactions has been reported from Finland. In a study of a possible relationship between sun exposure and late reactions in 4,875 adults who had received an iodinated contrast medium, a 3-month (April to June) peak in the incidence of reactions was seen. This period included 35 % of all events and most of the reactions occurred on sun-exposed areas of the body, leading the authors to conclude that a possible explanation for the observations was the photosensitizing effect of the contrast media. 

In the absence of easy-to-perform and reliable assays for the detection of contrast media-reactive IgE antibodies in patients sera, some other less direct but arguably more biologically and clinically relevant test procedures have occasionally been employed. With both the basophil activation and Prausnitz-Kustner (P-K) tests, the interaction between allergen (contrast medium) and IgE antibodies takes place at the basophil (or mast cell) surface, thus mimicking the in vivo situation. However, for different reasons, neither test has become, nor is likely to soon become, a routinely and widely applied procedure for the diagnosis of adverse reactions to contrast media or any other drug (see below). 

As always, a meticulously recorded and studied history is desirable, but additional clinical and laboratory tests can contribute greatly to an accurate diagnosis and help to identify the mechanism(s) of the reaction. Skin tests, detection, and quantitation of released mediators and serum IgE antibodies may all contribute to establishing a more precise diagnosis of an adverse response to an iodinated contrast medium. 

From at least the early 1980s, studies relevant to the possibility of monitoring contrast media-induced histamine release either directly or indirectly via measurement of urinary methy Ihistamine have been pursued. Although concentrations of histamine and its metabolite have been shown to increase in some patients who had an adverse reaction to a contrast medium, diagnostic tests for these mediators have not often been used and it was not until an assay for tryptase (see Sect. 4.5.1) became widely available that routine measurement... 

Adverse reactions that occur after contrast media injection typically occur within 20 min of the injection. An acute adverse reaction is an adverse reaction that occurs within 1 h of injection. Acute reactions are classified as being of mild, moderate, and severe intensity. Types of reactions include mild symptoms such as nausea and itching and severe reactions such as hypotensive shock and convulsions. A late adverse reaction to contrast medium is defined as a reaction that occurs at 1 h to 1 week after injection. Maculopapular rashes, erythema, and pruritus are the most common types of late reactions. A very late adverse reaction is a reaction that occurs at more than 1 week after contrast injection this includes reactions such as thyrotoxicosis. 

Adverse reactions are extremely rare in pediatric practice. However, preventive measures should be taken, and any reactions that do occur should be managed in collaboration with anesthesiologists. Adverse events justify the presence of at least two persons during any examination with contrast medium injection (one to take care of the patient and one to call the anesthesiologist). 

Aldehyde purity can be of critical importance some of the reactions of fluorinated aldehydes are adversely affected by the presence of small amounts of precursor acid chloride or aldehyde hydrate. For example, some of the catalysts used for polymerization (vide infraf are effectively deactivated by small amounts (0.1-0.5%) of aldehyde hydrate. We have not examined medium effects in the silane/acid chloride reaction, but the high reactivity of the fluorinated aldehydes can lead to unexpected results. For example, fluorinated aldehydes and acid chlorides condense rapidly in THF to afford esters of the form RfC(0)0CHCIR f. In contrast, this reaction is very slow in CHCI3. Fortunately, esters of this type are usually not significant products under our preferred reduction conditions. The aldehydes described here are quite reactive and can undergo spontaneous... 

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