CT Intravenous Contrast

Aka: CT Intravenous Contrast, Water-Soluble Iodinated Intravenous Contrast, Nonionic Iodinated Intravenous Contrast, Non-ionic contrast media, Low-Osmolality Contrast Media, LOMC, Intravenous Contrast, Anaphylactoid Reaction to Radiocontrast, Pretreatment of Contrast-Induced Anaphylactoid Reaction, Contrast Media Allergy, Contrast Media Reaction, Iodinated Contrast Dye, Iodixanol, Visipaque, Iopamidol, Isovue, Iopromide, Ultravist, Ioversol, Optiray

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II. Preparations

  1. See Radiographic Contrast Media (includes Oral Contrast and Gadolinium IV contrast for MRI)
  2. CT Intravenous Contrast is typically with Iodinated, Nonionic, Low-Osmolality Contrast Media (LOMC)
    1. Iodixanol (Visipaque)
    2. Iopamidol (Isovue)
    3. Iopromide (Ultravist)
    4. Ioversol (Optiray)

III. Contraindications: IV Contrast

  1. See Metformin under prevention below
  2. Pregnancy (relative contraindication)
    1. ACR recommends non-ionic, low osmolality iodinated agents if IV contrast is used
    2. Decision to use contrast (and for that matter CT)
      1. Based on clinical judgment that imaging IV benefits out-weigh risks
    3. Theoretical concern for fetal Thyroid conditions related to iodinated contrast
      1. Iodinated contrast crosses placenta
      2. No Teratogenicity has been found in animals with nonionic, low osmolality agents
  3. Radioactive Iodine-treated Thyroid disease (e.g. Graves Disease)
    1. Iodinated contrast competes for binding at Thyroid Gland with I-131 (results in ineffective treatment)
    2. Avoid iodinated contrast for 2 months following I-131 treatment
    3. Consult with endocrinlogy
  4. Serum Creatinine >1.5 to 2.0 mg/dl
  5. Serious IV contrast reaction history (e.g. Anaphylaxis)
    1. Mild to moderate reactions
      1. May be considered for IV Contrast use
      2. Use Pretreatment of Contrast-Induced Anaphylactoid Reaction described below
    2. Severe Reaction
      1. Do not use IV contrast if history of severe reaction

IV. Risk Factors: Contrast Reaction

  1. Most significant risks
    1. History of contrast-related anaphylactoid reaction
    2. Asthma, Allergic Rhinitis or atopy
    3. Ionic and/or high osmolality Intravenous Contrast media (older agents)
      1. Same major reaction (e.g. Anaphylaxis) rate for ionic vs nonionic agents
        1. Reaction Incidence: 1 per 170,000 administrations
      2. Mild to moderate reactions are more common with ionic agents and with high osmolality agents
      3. Most U.S. centers use non-ionic, low osolality Intravenous Contrast
  2. Other associated risks
    1. Older patient age
      1. >65 years old: 35 fatalities per million injections
      2. <65 years old: 4.5 fatalities per million injections
      3. Children have the lowest Incidence of IV contrast agent reactions
        1. Mild reaction rate for nonionic, low osmolality agents: 0.18%
    2. Renal Insufficiency
    3. Female gender
    4. Medication allergy or Food Allergy
    5. Comorbid conditions such as cardiovascular disease
    6. Concurrent Nephrotoxic Drugs such as NSAIDS
    7. Multiple drug allergies (especially if any prior medication-induced Anaphylaxis)

V. Risk Factors: Agents that do not increase contrast reaction (debunking myths)

  1. Seafood and shellfish do not increase the risk of Radiocontrast Material reaction
    1. The allergens in seafood and shellfish are tropomyosins and parvalbumin, not Iodine
  2. Iodine, as an integral component to Thyroid Physiology
    1. Iodine is not an allergen and does not increase the risk of Radiocontrast Material
    2. Schabelman (2010) J Emerg Med 39(5): 701-7 [PubMed]

VI. Adverse Effects

  1. Anaphylactoid Reaction
    1. Immediate reaction to small dose (does not require presensitization)
      1. Contrast with Anaphylaxis which is IgE mediated and requires allergen presensitization
    2. Emergency management (see Anaphylaxis)
      1. ABC Management
      2. Epinephrine 0.3 to 0.5 mg SQ q10-20 minutes
      3. Methylprednisolone 50 mg IV (for bronchospasm)
  2. Delayed reaction
    1. Constitutional symptoms occur >30 min post-contrast
    2. Management: Supportive
  3. Acute Tubular Necrosis (Acute Renal Failure)
    1. See Intravenous Contrast Related Acute Renal Failure
    2. Occurs more often if Acute Renal Failure Risk
  4. Local toxicity from extravasated Contrast Material (chemotoxic reactions)
    1. Apply ice to area and elevate
    2. Reaction worse with ionic contrast agents
      1. High osmolality agents (Hypaque, Conray)
      2. Ioxaglate meglumine (Hexabrix)
    3. Consider infusing contrast more slowly on future scans

VII. Prevention

  1. See Intravenous Contrast Related Acute Renal Failure
  2. See Pretreatment of Contrast-Induced Anaphylactoid Reaction below
  3. Use nonionic low osmolality agents (typically standard in United States)
  4. Avoid concurrent use of Nephrotoxic Drugs
  5. Avoid Intravenous Contrast when Serum Creatinine >1.5 to 2.0 (guidelines vary per institution)
  6. Stop Glucophage (Metformin) for 48 hours after contrast
    1. Theoretical risk of severe Lactic Acidosis
    2. May resume Glucophage in 48 hours without additional testing unless indicated below
    3. Indications for Serum Creatinine prior to restarting Glucophage
      1. Known renal dysfunction
      2. Increased risk of renal dysfunction following Intravenous Contrast exposure (e.g. CHF, Sepsis, ischemia)
  7. Consider N-Acetylcysteine before Intravenous Contrast
    1. See Intravenous Contrast Related Acute Renal Failure
  8. Hydrate before and after procedure
    1. Consider Normal Saline
    2. See Intravenous Contrast Related Acute Renal Failure

VIII. Management: Pretreatment of Contrast-Induced Anaphylactoid Reaction

  1. Indicated for prior radiocontrast reaction (mild to moderate)
    1. Do not give IV contrast if prior severe reactions (Anaphylaxis, cardiopulmonary collapse)
    2. Do not delay contrast for pretreatment in the evaluation acute, life-threatening conditions
  2. Efficacy
    1. Corticosteroids reduce the risk of mild reactions (hives) and respiratory symptoms
    2. Corticosteroids do not reduce the risk of anaphylactoid reactions (albeit rare)
    3. Most significant way to reduce reaction risk is to use nonionic, low-osmolality Contrast Material
    4. Tramer (2006) BMJ 333(7570):675 [PubMed]
    5. Wolf (1991) Invest Radiol 26(5): 404-10 [PubMed]
  3. Corticosteroid protocol (either agent below)
    1. Methyl-Prednisolone (medrol) 32 mg at 12 and 2 hours before
    2. Prednisone 50 mg at 13, 7 and 1 hour pre-contrast
  4. Antihistamines given also, 1 hour pre-contrast
    1. Diphenhydramine 50 mg IV/IM/PO at one hour pre-contrast and
    2. Consider Cimetidine or Ranitidine 1 hour pre-contrast

IX. References

  1. Swaminathan and Rezaie in Herbert (2014) EM:Rap 14(10): 1-2
  2. Maddox (2002) Am Fam Physician 66(7):1229-34 [PubMed]
  3. Greenberger (1991) J Allergy Clin Immunol 87:867-72 [PubMed]
  4. Rawson (2013) Am Fam Physician 88(5):312-6 [PubMed]

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