Basics
Description
- Immunologic or physiologic reactions to iodinated contrast media (CM) administered for intravenous (IV) studies including computed tomography CT scans, hysterosalpingograms, and certain urographic and cardiac studies.
- Reaction timing can be acute or delayed (1)[C].
- Acute reactions can be allergic-like (also known as anaphylactoid or idiosyncratic) or physiologic (also known as chemotoxic) (1)[C].
- Acute reactions are categorized as mild, moderate, or severe (2)[A].
- A breakthrough reaction refers to a reaction that occurs in a patient who has been premedicated for such reactions(2)[A].
- Delayed reactions occur from 1 hour to 1 week after iodinated CM administration (3)[A].
- Contrast-induced nephropathy (CIN) is a sudden decrease in renal function following IV iodinated CM administration without another known cause for renal insult (4)[A].
- Magnetic resonance imaging (MRI) CM is not included in this chapter.
Epidemiology
- High-osmolality contrast media (HOCM) has associated acute adverse events in 5-15% of cases. It is rarely or ever used now because of its side effects (1)[C].
- Low-osmolality contrast media (LOCM) has associated acute adverse events incidence reported between 0.2 and 0.7% in three different studies reviewed by the American College of Radiology (ACR) Committee Manual (Cochran et al., Mortele et al., Wang et al.). Serious acute adverse events are rare (0.04% per Katayama et al.) (1)[C].
- CIN incidence is difficult to assess because there is no standard definition for diagnosing CIN and the criteria used in different studies vary.
Etiology and Pathophysiology
- The pathogenesis of allergic-like reactions is not known, with several possible mechanisms resulting in immunologic mediator activation. Most are not associated with increased immunoglobulin E (IgE) (and therefore are not true allergic reactions). Allergic-like reactions are not dose or concentration dependent (1)[C],(2)[A].
- The pathogenesis of physiologic reactions is probably the result of the iodinated CM physiologic properties (i.e., osmolality, molecular binding, or chemotoxicity). Physiologic reactions are dose and concentration dependent (1)[C],(2)[A].
- The pathogenesis of CIN is not well understood at this time, but several factors have been suggested.
Risk Factors
- Prior iodinated CM reaction
- History of asthma, atopy, or allergy (attention to significant allergic reactions); cardiovascular (CV) disease; and anxiety
- For CIN: renal insufficiency/disease, diabetes mellitus, dehydration, CV disease, diuretic use, advanced age, hypertension, hyperuricemia, and multiple doses of IV contrast in less than 24 hours
- Metformin (risk of lactic acidosis)
- Contraindicated with myasthenia gravis
- "Package inserts suggest necessary precautions for known or suspected pheochromocytoma, thyrotoxicosis, dysproteinemias (such as multiple myeloma), or sickle cell disease" (1)[C].
- An allergy to shellfish itself is not associated with an increased risk of iodinated CM allergic-like reaction 2)[A],(4)[A].
General Prevention
- For patients with risk factors for CIN (including age >60 years, history of renal disease, treated hypertension, diabetes mellitus, and patients taking metformin or metformin-containing drugs), precontrast administration of serum creatinine and glomerular filtration rate (GFR) measurements should be obtained for further risk stratification (1)[C].
- Consult radiology for patients with GFR below 60 mL/min to evaluate need for CIN prevention steps/strategies (which may include PO or IV hydration, decreasing contrast dose, or alternative imaging depending on the level of risk).
- Consult radiology for patients taking metformin regarding the need for temporary discontinuation of medication and renal function follow-up.
- For prevention of allergic-like reactions, a frequently used elective premedication regimen is prednisone 50 mg PO at 13 hours, 7 hours, and 1 hour prior to radiographic contrast media (RCM) injection plus diphenhydramine 50 mg IV/IM/PO 1 hour prior to RCM injection. If the patient cannot take PO, hydrocortisone 200 mg IV may be substituted for oral prednisone (1)[C].
- For patients with allergic-like reaction history, consider changing the type of iodinated CM used.
- Assess alternative imaging modalities.
- Avoid HOCM.
Diagnosis
History
- Prior reaction to iodinated CM
- Other risk factors present
- Signs/symptoms with onset following iodinated CM injection
Physical Exam
- Vital signs (RR, HR, and BP)
- Observation of presenting signs/symptoms including speech and voice (for signs of airway compromise)
- For allergic-like reactions, variety of signs and symptoms may include (but not limited to) urticaria and pruritus, edema, wheezing, bronchospasm, or anaphylactic shock (1)[C].
- For physiologic reactions, variety of signs and symptoms include (but not limited to) nausea, vomiting, flushing, warmth/chills, headache, vasovagal reaction, arrhythmia, convulsions, seizures, and hypertensive emergency 1)[C].
- Severe allergic-like or physiologic reaction can lead to pulmonary edema or cardiac arrest (1)[C],2)[A],3)[A].
Differential Diagnosis
The presenting signs and symptoms following contrast administration suggest the diagnosis.
Diagnostic Tests & Interpretation
Initial Tests (lab, imaging)
For CIN, serum creatinine and GFR
Test Interpretation
For CIN, there are currently no standard criteria for diagnosis.
Treatment
General Measures
- Treatment considerations depend on the type of reaction (i.e., allergic-like, physiologic, CIN), presenting signs and symptoms, severity of reaction as well as the patient's preexisting medical conditions.
- For mild reactions, observation may be the only intervention required.
- For severe reactions, always use the resuscitation ABCs (airway, breathing, circulation) and call the appropriate emergency response team or 911.
Medication
- For detailed treatment guidelines by symptom and severity, please see the ACR Committee on Drugs and Contrast Media, "ACR Manual on Contrast Media," Table 5 available online.
- Generally, for mild allergic-like reactions: diphenhydramine 25-50 mg PO/IM/IV (1)[C]
- Generally, for moderate allergic-like reactions: epinephrine 0.3 mg IM (0.3 mL of 1:1,000 dilution) (1)[C]
- Generally, for severe allergic-like reactions: epinephrine 1-3 mL IV of 1:10,000 dilution administered by slow infusion into a running IV saline infusion (1)[C].
- For bronchospasm, may add albuterol inhaler 2 puffs (90 Îĵg per puff) totalling 180 Îĵg. This can be repeated (1)[C].
- For physiologic reactions, supportive treatment based on presentation
- For CIN: IV hydration and nephrology consultation. Monitor renal function.
Ongoing Care
Follow-up Recommendations
Continue supportive care as necessary based on the patient's symptoms and clinical condition.
References
1.American College of Radiology Committee on Drugs and Contrast Media. ACR Manual on Contrast Media. Version 9. Reston, VA: American College of Radiology. http://www.acr.org/quality-safety/resources/contrast-manual. Accessed April 28, 2014.2.Schopp JG, Iyer RS, Wang CL, et al. Allergic reactions to iodinated contrast media: premedication considerations in patients at risk. Emerg Radiol. 2013;20(4):299-306.
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3.Namasivayam S, Kalra MK, Torres WE, et al. Adverse reactions to intravenous iodinated contrast media: a primer for radiologists. Emerg Radiol. 2006;12(5):210-215.
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4.Bettmann MA. Frequently asked questions: iodinated contrast agents. Radiographics. 2004;24(Suppl 1):S3-S10.
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Codes
ICD09
- 995.27 Other drug allergy
- 580.89 Acute glomerulonephritis with other specified pathological lesion in kidney
ICD10
- Z91.041 Radiographic dye allergy status
- N14.1 Nephropathy induced by oth drug/meds/biol subst
SNOMED
- 293637006 contrast media allergy (disorder)
- 26367008 Radiographic contrast agent nephropathy (disorder)
Clinical Pearls
- Iodinated CM (particularly LOCM) is a safe and effective tool for imaging patients. However, it is not without risks. These risks can be life threatening in rare instances.
- Proper evaluation and preparation of the patient prior to iodinated CM administration can reduce the risk for adverse reactions.
- When uncertain, ordering clinicians should consult radiology (or the appropriate clinical service performing the contrast study) to have questions answered before the patient receives iodinated CM.