Organic Radiographic Iodinated Contrast Media: What Is It and How Do We Prevent Adverse Reactions?

Whenever we feel sick, especially with unexpected chest or abdominal pain, we go to a hospital to see a doctor. While at the hospital, a physician may administer a CT examination (PROVIDE DEFINITION), with contrast, to rule out severe organic or vessel disease. Contrast allows, most vascular diseases such as vascular malformations, aneurisms, vascular stenosis and/or emboli, and vessel ruptures to be shown more clearly and confidently. According to the enhancement intensity, radiologists can understand the blood supply of some lesions, enabling them to make an accurate diagnosis. Contrast media can help radiologists to differentiate vessel structures from normal or abnormal solid soft tissues. Iodinated contrast media (ICM) generally has an excellent safety record. Adverse effects from the intravascular administration of ICM are mostly mild and self-limited; reactions that occur from the extra vascular use of ICM are rare. Nonetheless, severe or life-threatening reactions can occur with both modes of administration. Adverse reactions to ICM are classified as idiosyncratic (provide definition) and non idiosyncratic.

Idiosyncratic reactions

Idiosyncratic reactions typically begin within 20 minutes of the ICM injection, independent of the dose that is administered. A severe idiosyncratic reaction can occur after an injection of less than 1 ml of a contrast agent. The symptoms of an anaphylactic reaction are classified as mild, moderate, and severe.

• Mild symptoms include hives and skin rash, the most commonly reported adverse reactions are pruritus, runny nose, nausea, brief retching and/or vomiting, diaphoresis, coughing, and dizziness. Patients with mild symptoms should be observed for the progression or evolution of a more severe reaction, which requires treatment.
• Moderate symptoms include persistent vomiting, diffuse urticaria, headache, facial edema, laryngeal edema, mild bronchial spasm or difficulty in breathing, palpitations, tachycardia, or bradycardia, hypertension, and abdominal cramps.
• Severe symptoms include life-threatening arrhythmias (i.e., ventricular tachycardia), hypotension, bronchial spasm, laryngeal edema, pulmonary edema, seizures, syncope, and death.

Non idiosyncratic reactions

Non idiosyncratic reactions include slower heart rate, hypotension, and abnormal vessel dilation or contraction, neuropathy, cardiovascular reactions, extravasation, and delayed reactions. Other no idiosyncratic reactions include sensations of warmth, a metallic taste in the mouth, and nausea and vomiting.

Some vasovagal reactions may be a result of coexisting circumstances such as emotions, apprehension, pain, and abdominal compression, rather than ICM administration.

Nephropathy

Contrast agent–related nephropathy is an elevation of the serum creatinine level that is more than 0.5 mg% or more than 50% of the baseline level at 1-3 days after the ICM injection. The elevation peaks by 3-7 days, and the creatinine level usually returns to baseline in 10-14 days. The incidence of contrast agent–related nephropathy in the general population is estimated to be 2-7%.

Cardiovascular reactions

ICM can cause hypotension and bradycardia. Vasovagal reactions, a direct negative inotropic effect on the myocardium, and peripheral vasodilatation probably contribute to these effects. The latter two may represent the actions of cardioactive and vasoactive substances that are released after an anaphylactic reaction to the ICM. This effect is generally self-limiting, but it can also be an indicator of a more severe, evolving reaction.

Extravasation

Extravasation of ICM into soft tissues during an injection can lead to tissue damage as a result of direct toxicity of the contrast agent or pressure effects, such as compartment syndrome.

Delayed reactions

Delayed reactions become apparent at least 30 minutes after but within 7 days of the ICM injection. These reactions are identified in as many as 14-30% of patients after the injection of ionic monomers and in 8-10% of patients after the injection of nonionic monomers.

Common delayed reactions include the development of flulike symptoms, such as fatigue, weakness, upper respiratory tract congestion, fevers, chills, nausea, vomiting, diarrhea, abdominal pain, pain in the injected extremity, rash, dizziness, and headache.

These signs and symptoms almost always resolve spontaneously. Usually little or no treatment is required.

Risk factors for adverse ICM reactions

• Allergy: with regard to specific risk factors, a history of a prior allergy-like reactions to contrast media is associated with an up to five times increased likelihood of the patient experiencing a subsequent reaction.
• Asthma: a history of asthma may indicate an increased likelihood of a contrast reaction.
• Renal insufficiency: over 60 years of age, a history of renal disease, including dialysis, kidney transplant, single kidney, renal cancer, and renal surgery, a history of hypertension requiring medical therapy, and a history of diabetes mellitus, metformin or metformin-containing drug combinations.
• Cardiac status: patients with significant cardiac disease may be at increased risk for contrast reactions. These include symptomatic patients and those with severe aortic stenosis, primary pulmonary hypertension, or severe but well-compensated cardiomyopathy.
• Anxiety: there is anecdotal evidence that severe adverse effects to contrast media or to procedures can be mitigated at least in part by reducing anxiety.

Prevention for adverse reactions to ICM

A pertinent patient medical history should be obtained, with the following taken under consideration: history of allergies, asthma, diabetes mellitus, renal insufficiency, and/or cardiac diseases, currently or recently used medicines, the possibility of pregnancy, and previous contrast agent administration. If the patient has had a reaction in the past, the nature of the reaction must be determined. Serum creatinine levels need to be determined as well.

With so many many risk factors, close attention must be paid before taking an examination with contrast media. Fortunately, the incidence of any adverse reaction to ICM is about 15%. Most of these reactions are mild and require no treatment. For others, prophylactic medications may be used before contrast administration to reduce the incidence rate of adverse reactions. Ultrasound or MRI can serve as alternatives for patients who are not suitable for ICM.

If you have any question regarding ICM, please talk to your radiologist.

References:

1． ACR Manual on Contrast Media. American College of Radiology. Version 9. 2013. ISBN: 978-1-55903-012-0

2． Delaney A, Carter A, Fisher M: The prevention of anaphylactoid reactions to iodinated radiological contrast media: a systematic review. BMC Medical Imaging 2006; 6:2.