Intravascular Contrast Media

Question 1

List some non ionic LOCM

Answer 1

Non ionic monomers:

Iopamidol (Niopam, Iopamiron, Isovue, Solutrast)

Iohexol (Omnipaque)

Iopromide (Niopam, Iopamiron)

Iomeprol (Iomeron)

Ioversol (Optiray)

Question 2

What determines toxicity of contrast

Answer 2

Osmolarity
Ionic charge
Chemical structure
Lipophilicity

Question 3

What is the criteria for CIN - contrast induced nephropathy

Answer 3

Urine output < 0.5 ml/kg/hr for 6 hrs or increase in serum creatinine > 25 micromoles/L within 48 hrs and or increase in serum creat > 50% baseline within a week

• rises within 24 hrs, peaks by 2-3 dys then returns to baseline by 3-7 dys

Question 4

For how long does contrast preclude radioiodine treatment of thyroid cancer and radioiodine imaging

Answer 4

2 months.

Question 5

Categorize contrast reactions

Answer 5

Mild - N/V, urticaria

Moderate - Mild bronchospasm, vasovagal reaction, tachycardia, diffuse erythema

Severe - CVS collapse. moderate or severe bronchospasm, laryngeal edema, LOC, seizures

Question 6

How common is death cause by contrast agents

Answer 6

1.1 to 1.2 per million

Question 7

What precautions to take for patients at increase risk of anaphylactic (IgE negative) contrast reaction

Answer 7

1. Consider other test
2. If necessary:

• use non ionic LOCM or different agent than first used
• close supervision
• leave cannula in and observe for 30 min
• Ensure emergency drugs ready
• premedication not supported by data. Antihistamines associated with increased incidence of flushing

Question 8

Can contrast be given in

1. Pregnancy
2. Lactation
3. Thyrotoxicosis

Answer 8

1. If clinically situation dictates
2. No special precaution (only 0.5% of dose receive by mother reaches breast milk) - considered safe

Question 9

Name examples of MRI contrast

Answer 9

Paramagnetic - gadolinium - -shorten T1 relaxation time

Ferromagnetic - larger albumin coated magnetite - retain magnetism when applied field is removed - particle aggregation risk cell function - unsafe as contrast

Superparamagnetic - particles of iron oxide - abrupt changes in local magnetic field - rapid proton rephrasing and reduced T2 relaxation time - black on T2 - provides GI contrast

Question 10

Describe structure of GAD and how administered

Answer 10

Toxic heavy metal (157 mass number) 7 unpaired electrons. Stable complex with large organic molecules

Administered IV or oral

Three forms

1. Extra cellular - dose 0.1 mmol/kg to 0.2 mmol/kg
   a DTPA, Magnevist
   b Omniscan
   c PeoHance
2. Liver

Multihance

3. Blood pool agents

Vasovist, Gadofosvesettrisodium

Question 11

Contrast agents in ultrasound must be about 3-5 micrometers in diameter (size of a RBC). What type of contrast do they provide and what are clinical applications?

Answer 11

Pure IV contrast. Gas diffuses after 5 min

• identify solid lesions
• assist Us guided IR procedures
• voiding - detect reflux in children (here in bladder)
• disease activity in IBD

Examples - Levovist, SonoVue