Positive skin tests in late reactions to radiographic contrast media

In the last few years delayed reactions several hours after the injection of radiographic and contrast materials (PRC) have been described with increasing frequency. The authors report two observations on patients with delayed reactions in whom intradermoreactions (IDR) and patch tests to a series of ionic and non ionic PRC were studied. After angiography by the venous route in patient n degree 1 a biphasic reaction with an immediate reaction (dyspnea, loss of consciousness) and delayed macro-papular rash appeared, whilst patient n degree 2 developed a generalised sensation of heat, persistent pain at the site of injection immediately and a generalised macro-papular reaction after 24 hours. The skin tests revealed positive delayed reactions of 24 hours and 48 hours by IDR and patch tests to only some PRC with common chains in their structures. The positive skin tests are in favour of immunological reactions and may help in diagnosis of allergy in the patients.     

Allergy to iodinated contrast media

Iodinated contrast media are responsible for immediate or delayed adverse reactions. Because of the wide use of these products, one must consider them as drugs. The delay and nature of the undesirable events must be carefully recorded because in some selected cases, a true allergic mechanism can be proved. Cutaneous skin tests identify the culprit drug and find safe alternative for the patient.     

Anaphylactoid reactions and late skin reactions to iodinated contrast media: present state of the question--idea development]

PURPOSE: Adverse reactions to iodinated contrast media (ICM) share various mechanisms. Anaphylactoid reactions are among the most serious reactions when they are characterized by the elevation of seric tryptase. Pretreatment with corticosteroids and anti-H1 or the use of non-ionic contrast media do not prevent anaphylaxis. Late skin reactions could be mostly related to delayed hypersensitivity. Previous reactions to contrast media, cardiovascular disorders, beta-blockers, asthma, and atopy are risk factors. Female gender and age increase the severity. CURRENT KNOWLEDGE AND KEY POINTS: Anaphylaxis can be demonstrated by intradermal tests and the identification of specific IgEs. Delayed hypersensitivity is shown by the results of epicutaneous tests and the immunohistology of the skin. FUTURE PROSPECTS AND PROJECTS: Allergologic tests are advised in the case of previous reactions. In case of emergency, gadopentetate dimeglumine can be alternatively used. The other risk factors lead to the combination of pretreatment and use of non-ionic monomeric contrast media. Immediate hypersensitivity to iodinated media might increase in the near future with the use of divalent molecules.     

Magnetic resonance imaging of myocardial infarction using gadolinium-based contrast agent.

OBJECTIVES: To evaluate myocardial infarcts using a segmented inversion-recovery prepared gradient echo sequence on a 1.5 Tesla MR scanner after injection of a gadolinium-based contrast agent. METHODS: Fourteen patients were prospectively offered a cardiac MR exam between November 2003 and February 2004. Six patients had a history of anterior wall MI, six had a history of inferior wall MI and two patients had MI of undetermined location. RESULTS: Delayed enhancement indicating the presence of scarring was visualized in all fourteen patients. The scarring was transmural in ten patients and non-transmural in four patients. CONCLUSION: Delayed enhancement of infarcted areas in the myocardium after injection of gadolinium-based contrast agent represents scarring and adequate resolution exists to distinguish transmural from non-transmural scarring. This technique is useful in determining viability of infarcted myocardium, may detect infarcts missed by SPECT and may help in the selection of patients for implantation of defibrillators.     

Anaphylactoid reactions to radiocontrast media

Adverse reactions to contrast material are a concern because iodinated contrast materials are commonly used drugs. The risk for adverse reaction is 4% to 12% with ionic contrast materials and 1% to 3% with nonionic contrast materials. The risk for severe adverse reaction is 0.16% with ionic contrast materials and 0.03% with nonionic contrast materials. The death rate, one to three per 100,000 contrast administrations, is similar for both ionic and nonionic agents. More than 90% of adverse reactions with nonionic contrast materials are anaphylactoid. The types of severe reactions seen with nonionic contrast administration were initially predominantly anaphylactoid. With the advent of helical CT angiography, the reactions are now predominantly attributable to cardiopulmonary decompensation. With the widespread use of nonionic contrast materials, adverse reactions are now seen less frequently. Skills involved in evaluating and treating adverse reactions are not as frequently used. Periodic reviews and updates of specific treatment plans for various reactions with the physicians and staff who use contrast material are very important to ensure optimal preparedness. The key to successful treatment is preparation and early intervention.     

Anaphylactoid reactions to radiocontrast media.

As the role for diagnostic and therapeutic contrast-enhanced imaging increases, review of the epidemiology, mechanisms, risk factors, and pretreatment for radiocontrast-mediated anaphylactoid reactions becomes more and more pertinent. Ongoing research has failed to elucidate the precise mechanisms of both early and late reactions, though the current data point to a multifactorial pathogenesis. The risk of reactions has decreased over time as contrast media have evolved from ionic, high-osmolality to nonionic, low-osmolality formulations; however, the expense of the low-osmolality agents limit their universal use. Today, 1-12% of patients exhibit adverse responses ranging from mild to severe, with individual risk depending on the type of contrast administered and certain baseline patient characteristics. For those high-risk patients who must receive contrast, effective pretreatment guidelines have been established.     

Systemic anaphylactoid reactions to lodinated contrast media during cardiac catheterization procedures: Guidelines for prevention,diagnosis, and treatment

This report represents the first guidelines for prevention, diagnosis, and treatment of anaphylactoid reactions to contrast media occurring specifically during cardiac catheterization. The incidence of contrast media complications in the catheterization laboratory is 0.23% with 1 death per 55,000. Anaphylactoid reactions are nonimmune mediated, but histamine release and other mediators produce a clinical presentation indistinguishable from anaphylaxis. In patients with known previous reactions, pretreatment with steroids and diphenhydramine and the use of nonionic contrast media have significantly reduced the potential of recurrent reaction. Minor reactions such as limited urticaria may be watched for progression or treatment with diphenhydramine, whereas more serious reactions such as angioedema or laryngeal edema require airway stability and ephinephrine administration. Shock should be vigorously treated simultaneously with intravenous epinephrine and large volumes of normal saline. If the patient can be stabilized, the study should be completed as histamine, leukotrienes, and other vasoactive products should be relatively depleted.     

Skin manifestations of drug reactions

Dermatologic manifestations of adverse drug reactions are commonly encountered in both hospital-based and ambulatory medical practice. Diagnosis is confounded by the myriad clinical presentations associated with cutaneous drug eruptions. Some presentations are highly characteristic, while others are not as straightforward, and may simulate other primary dermatoses. In many cases, patients are utilizing several medications and an obvious temporal relationship to a specific drug is not always apparent or expressed by the patient during disclosure of his or her medical history. A thorough medication history and a high index of suspicion are very important components in the diagnosis of drug eruptions.     

New pharmacological protocols to prevent or reduce contrast media nephropathy

Contrast media associated acute renal failure represents the third cause of in-hospital renal function deterioration after decreased renal perfusion and post-operative renal insufficiency. Although generally benign, this complication shows a mortality rate ranging from 3.8% to 64%, depending on the increase of creatinine concentration. The mechanism by which contrast-induced renal failure occurs is not well understood. Contrast agent-associated nephrotoxicity appears to be a result of direct contrast induced renal tubular epithelial cell toxicity and renal medullary ischemia. Furthermore, a key mechanism seems to be alteration in renal dynamics, probably caused by imbalances between vasodilator and vasoconstrictor factors, including the activities of nitric oxide, prostaglandins, endothelin and reactive oxygen species. Recommendations to prevent contrast-associated nephrotoxicity are: 1) periprocedural hydration, 2) use of a low osmolality contrast, and 3) limiting the amount of contrast agent. Recently, considerable interest has resulted from the preliminary positive data on the effectiveness of prophylactic administration of antioxidant compounds (such as acetylcysteine and ascorbic acid) and fenoldopam.     

Transient small bowel angioedema due to intravenous iodinated contrast media

Three cases of transient proximal small bowel angioedema induced by intravenous administration of nonionic iodinated contrast media (CM) are presented. Computed tomography (CT) images in the venous phase displayed the proximal small bowel with circumferential thickening of the wall including the duodenum and proximal segment of the jejunum. The bowel wall was normal in non-enhanced images, and normal or inconspicuous in arterial phase enhanced images. In one of the three cases, the bowel wall was thickened in venous phase but disappeared in the 40 s delayed phase images. No filling defect was seen in the lumen of the superior mesenteric artery and vein. No peritoneal effusion or mesentery abnormality was found. Each of these patients reported only mild abdominal discomfort and recovered without specific treatment within a short time. Only one patient suffered mild diarrhea after scanning which had resolved by the following day. The transient anaphylactic small bowel angioedema due to intravenous iodinated contrast media was easily diagnosed based on its characteristic CT findings and clinical symptoms. Differential diagnosis may include inflammatory and ischemic bowel disease, as well as neoplasms. A three-phase CT protocol and good understanding of this disorder are fundamentally important in the diagnosis of this condition. The supposed etiology behind the transient anaphylactic reaction to intravenous administration of iodinated CM in small bowel is similar to other CM-induced hypersensitive immediate reactions. The predilection location of transient anaphylactic bowel angioedema is the small intestine, particularly the proximal segment. A speculated cause may be the richer supply of vessels in the small intestine, ample mucous folds and loose connective tissue in the duodenum and the jejunum.