Pharm

CT Intravenous Contrast

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 Reaction, Iodinated Contrast Dye, Iodixanol, Visipaque, Iopamidol, Isovue, Iopromide, Ultravist, Ioversol, Optiray

See Also

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)
1. Iodixanol (Visipaque)
2. Iopamidol (Isovue)
3. Iopromide (Ultravist)
4. Ioversol (Optiray)

Contraindications
IV Contrast

See Metformin under prevention below
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
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
Serum Creatinine >1.5 to 2.0 mg/dl (e.g. GFR <30 ml/min)
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

Risk Factors
Contrast Reaction

Most significant risks
1. History of prior contrast-related anaphylactoid reaction (highest risk)
2. Asthma, Allergic Rhinitis or atopy
3. Ionic and/or high osmolality Intravenous Contrast media (older agents)
  1. Original hyperosmolar agents had adverse effect rates as high as 15%
    1. Compare with current low osmolality adverse effect rates of 0.2 to 0.7%
  2. Same major reaction (e.g. Anaphylaxis) rate for ionic vs nonionic agents
    1. Reaction Incidence: 1 per 170,000 administrations
  3. Mild to moderate reactions are more common with ionic agents and with high osmolality agents
  4. Most U.S. centers use non-ionic, low osolality Intravenous Contrast
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)

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

Seafood and shellfish do not increase the risk of Radiocontrast Material reaction
1. The allergens in seafood and shellfish are Proteins (tropomyosins and parvalbumin), not Iodine
Povidone Iodine (Betadine) reactions are a Contact Dermatitis
1. Povidone Iodine Contact Dermatitis does NOT predispose to Radiocontrast Material reaction
Iodine is NOT an allergan
1. Do NOT add Iodine as an allergan in the EHR
2. Iodine is an integral component to Thyroid Physiology
3. Iodine is NOT an Antigen, as it is too small of a molecule to trigger an Antibody response
4. Iodide is added to most Table Salt, and patients typically do not have a Anaphylaxis to salt
5. Iodine does not increase the risk of Radiocontrast Material reaction
References
1. (2023) Presc Lett 30(7): 40
2. Schabelman (2010) J Emerg Med 39(5): 701-7 [PubMed]

Adverse Effects

Anaphylactoid Reaction
1. Immediate reaction to small dose (does not require pre-sensitization)
  1. Contrast with Anaphylaxis which is IgE mediated and requires allergen presensitization
  2. Histamine dependent response
  3. Associated with diffuse and Facial Edema, Dyspnea, Hypotension, laryngeal edema and Stridor, Wheezing, Hypoxia
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)
Delayed reaction
1. Constitutional symptoms occur >30 min post-contrast
2. Management: Supportive
Acute Tubular Necrosis (Acute Renal Failure)
1. See Intravenous Contrast Related Acute Renal Failure
2. Occurs more often if Acute Renal Failure Risk
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
Other associated symptoms
1. Nausea or Vomiting
2. Flushing, warmth or chills
3. Headaches
4. Dizziness
Physiologic Effects
1. Anxiety
2. Vasovagal Syncope
3. Inotropic effects
4. Neurologic effects

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 Metformin for 48 hours after contrast
1. Theoretical risk of severe Lactic Acidosis
2. May resume Metformin in 48 hours without additional testing unless indicated below
3. Indications for Serum Creatinine prior to restarting Metformin
  1. Known renal dysfunction
  2. Increased risk of renal dysfunction following Intravenous Contrast exposure (e.g. CHF, Sepsis, ischemia)
Consider N-Acetylcysteine before Intravenous Contrast
1. See Intravenous Contrast Related Acute Renal Failure
Hydrate before and after procedure
1. Consider Normal Saline
2. See Intravenous Contrast Related Acute Renal Failure

Management
Pretreatment of Contrast-Induced Anaphylactoid Reaction

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
Efficacy
1. Despite pretreatment, 12% of patients with prior reactions will have new reactions
  1. When reactions do occur despite pretreatment, they are typically either similar or less severe than prior
2. Corticosteroids reduce the risk of mild reactions (hives) and respiratory symptoms
3. Corticosteroids do not reduce the risk of anaphylactoid reactions (albeit rare)
4. Most significant way to reduce reaction risk is to use nonionic, low-osmolality Contrast Material
5. Tramer (2006) BMJ 333(7570):675 [PubMed]
6. Wolf (1991) Invest Radiol 26(5): 404-10 [PubMed]
Corticosteroid protocol (any of the agents below)
1. Methyl-Prednisolone (Medrol) 40 mg IV at 12 and 2 hours before
2. Prednisone 50 mg at 13, 7 and 1 hour pre-contrast
3. Hydrocortisone 200 mg IV every 4 hours
Antihistamines given also, 1 hour pre-contrast
1. Diphenhydramine 50 mg IV/IM/PO at one hour pre-contrast AND
2. Also consider H2 Blocker (e.g. Cimetidine, Famotidine or Ranitidine) 1 hour pre-contrast

References

LoVecchio (2023) Crit Dec Emerg Med 37(7): 32
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]