II. Preparations
- See Radiographic Contrast Media (includes Oral Contrast and Gadolinium IV contrast for MRI)
- CT Intravenous Contrast is typically with Iodinated, Nonionic, Low-Osmolality Contrast Media (LOMC)
- Iodixanol (Visipaque)
- Iopamidol (Isovue)
- Iopromide (Ultravist)
- Ioversol (Optiray)
III. Contraindications: IV Contrast
- See Metformin under prevention below
- Pregnancy (relative contraindication)
- ACR recommends non-ionic, low osmolality iodinated agents if IV contrast is used
- Decision to use contrast (and for that matter CT)
- Based on clinical judgment that imaging IV benefits out-weigh risks
- Theoretical concern for fetal Thyroid conditions related to iodinated contrast
- Iodinated contrast crosses placenta
- No Teratogenicity has been found in animals with nonionic, low osmolality agents
-
Radioactive Iodine-treated Thyroid disease (e.g. Graves Disease)
- Iodinated contrast competes for binding at Thyroid Gland with I-131 (results in ineffective treatment)
- Avoid iodinated contrast for 2 months following I-131 treatment
- Consult with endocrinlogy
- Serum Creatinine >1.5 to 2.0 mg/dl
- Serious IV contrast reaction history (e.g. Anaphylaxis)
- Mild to moderate reactions
- May be considered for IV Contrast use
- Use Pretreatment of Contrast-Induced Anaphylactoid Reaction described below
- Severe Reaction
- Do not use IV contrast if history of severe reaction
- Mild to moderate reactions
IV. Risk Factors: Contrast Reaction
- Most significant risks
- History of contrast-related anaphylactoid reaction
- Asthma, Allergic Rhinitis or atopy
- Ionic and/or high osmolality Intravenous Contrast media (older agents)
- Same major reaction (e.g. Anaphylaxis) rate for ionic vs nonionic agents
- Reaction Incidence: 1 per 170,000 administrations
- Mild to moderate reactions are more common with ionic agents and with high osmolality agents
- Most U.S. centers use non-ionic, low osolality Intravenous Contrast
- Same major reaction (e.g. Anaphylaxis) rate for ionic vs nonionic agents
- Other associated risks
- Older patient age
- >65 years old: 35 fatalities per million injections
- <65 years old: 4.5 fatalities per million injections
- Children have the lowest Incidence of IV contrast agent reactions
- Mild reaction rate for nonionic, low osmolality agents: 0.18%
- Renal Insufficiency
- Female gender
- Medication allergy or Food Allergy
- Comorbid conditions such as cardiovascular disease
- Concurrent Nephrotoxic Drugs such as NSAIDS
- Multiple drug allergies (especially if any prior medication-induced Anaphylaxis)
- Older patient age
V. Risk Factors: Agents that do not increase contrast reaction (debunking myths)
- Seafood and shellfish do not increase the risk of Radiocontrast Material reaction
- The allergens in seafood and shellfish are tropomyosins and parvalbumin, not Iodine
-
Iodine, as an integral component to Thyroid Physiology
- Iodine is not an allergen and does not increase the risk of Radiocontrast Material
- Schabelman (2010) J Emerg Med 39(5): 701-7 [PubMed]
VI. Adverse Effects
- Anaphylactoid Reaction
- Immediate reaction to small dose (does not require presensitization)
- Contrast with Anaphylaxis which is IgE mediated and requires allergen presensitization
- Emergency management (see Anaphylaxis)
- ABC Management
- Epinephrine 0.3 to 0.5 mg SQ q10-20 minutes
- Methylprednisolone 50 mg IV (for bronchospasm)
- Immediate reaction to small dose (does not require presensitization)
- Delayed reaction
- Constitutional symptoms occur >30 min post-contrast
- Management: Supportive
-
Acute Tubular Necrosis (Acute Renal Failure)
- See Intravenous Contrast Related Acute Renal Failure
- Occurs more often if Acute Renal Failure Risk
- Local toxicity from extravasated Contrast Material (chemotoxic reactions)
- Apply ice to area and elevate
- Reaction worse with ionic contrast agents
- High osmolality agents (Hypaque, Conray)
- Ioxaglate meglumine (Hexabrix)
- Consider infusing contrast more slowly on future scans
VII. Prevention
- See Intravenous Contrast Related Acute Renal Failure
- See Pretreatment of Contrast-Induced Anaphylactoid Reaction below
- Use nonionic low osmolality agents (typically standard in United States)
- Avoid concurrent use of Nephrotoxic Drugs
- Avoid Intravenous Contrast when Serum Creatinine >1.5 to 2.0 (guidelines vary per institution)
- Stop Glucophage (Metformin) for 48 hours after contrast
- Theoretical risk of severe Lactic Acidosis
- May resume Glucophage in 48 hours without additional testing unless indicated below
- Indications for Serum Creatinine prior to restarting Glucophage
- Known renal dysfunction
- Increased risk of renal dysfunction following Intravenous Contrast exposure (e.g. CHF, Sepsis, ischemia)
- Consider N-Acetylcysteine before Intravenous Contrast
- Hydrate before and after procedure
VIII. Management: Pretreatment of Contrast-Induced Anaphylactoid Reaction
- Indicated for prior radiocontrast reaction (mild to moderate)
- Do not give IV contrast if prior severe reactions (Anaphylaxis, cardiopulmonary collapse)
- Do not delay contrast for pretreatment in the evaluation acute, life-threatening conditions
- Efficacy
- Corticosteroids reduce the risk of mild reactions (hives) and respiratory symptoms
- Corticosteroids do not reduce the risk of anaphylactoid reactions (albeit rare)
- Most significant way to reduce reaction risk is to use nonionic, low-osmolality Contrast Material
- Tramer (2006) BMJ 333(7570):675 [PubMed]
- Wolf (1991) Invest Radiol 26(5): 404-10 [PubMed]
-
Corticosteroid protocol (either agent below)
- Methyl-Prednisolone (medrol) 32 mg at 12 and 2 hours before
- Prednisone 50 mg at 13, 7 and 1 hour pre-contrast
-
Antihistamines given also, 1 hour pre-contrast
- Diphenhydramine 50 mg IV/IM/PO at one hour pre-contrast and
- Consider Cimetidine or Ranitidine 1 hour pre-contrast
IX. References
- Swaminathan and Rezaie in Herbert (2014) EM:Rap 14(10): 1-2
- Maddox (2002) Am Fam Physician 66(7):1229-34 [PubMed]
- Greenberger (1991) J Allergy Clin Immunol 87:867-72 [PubMed]
- Rawson (2013) Am Fam Physician 88(5):312-6 [PubMed]