Iodinated Contrast Media (Part 2) Flashcards

Question

Non-Ionic Contrast Agents

Answer 1

Advantages: Reduced osmolarity Better tolerated Fewer reactions Reduced discomfort Less tissue damage Less dilution Wider clinical application

Answer 2

Thickness or resistance to flow Affected by: The concentration The size of the molecules The temperature of the contrast agent Ionic/Non-ionic dimers are more viscous than their monomeric counterpart. Viscosity will affect the rate of injection.

Answer 3

Water soluble so can be administered intravenously or ingested

Answer 4

What other imaging examinations make use of iodinated contrast agents? Name at least three.

Answer 5

Intravenously contrast is excreted via kidneys by glomerular filtration. Excretion rate will depend on plasma volume and GFR (Glomerular Filtration Rate). GFR will determine kidney function – cannot be directly measured so this is estimated based on creatinine level, age, race and gender (eGFR).

Answer 6

Creatinine – chemical waste product formed from the breakdown of protein and muscle. Excreted by the kidneys so high levels of blood creatinine indicates renal impairment. Creatinine and eGFR are indicators of kidney function. Prior to IV contrast administration, patients need to have creatinine and eGFR blood tests done.

Answer 7

Hypersensitivity to iodine Previous reaction to contrast media Asthma or significant allergy history Heart/lung conditions High blood pressure Renal impairment >70 years of age Allergies to seafood/shellfish is NOT a risk factor Whilst there is iodine in shellfish, the allergy is due to the certain proteins such as tropomyosins not to iodine itself.

Answer 8

Diabetes (use of Metformin) Metformin is used in type 2 diabetes to decrease the amount of glucose produced by the liver and to increase the body’s response to insulin. In patients with renal failure, the renal clearance of metformin is decreased and there is an associated risk of lactic acidosis. Metformin needs to be stopped prior to IV contrast administration. Impaired thyroid function (hyperthyroidism: overactive thyroid) A typical dose of 100ml iodinated contrast medium increases free iodide in the body and can overwhelm physiologic thyroid hormone regulation in susceptible individuals.

Answer 9

Despite improvements in iodinated contrast agents, adverse reactions still occur. Range from mild reactions (majority) to life threatening emergencies (rare). Reactions can be immediate (up to 1hr post administration of contrast) or delayed (from 1hr to 7 days). Any reactions need to be documented and recorded under the patients record for future reference.

Answer 10

Some patients may experience a “metallic” taste after the intravenous injection of a contrast agent. Taste dysfunction, or a “metallic” taste, can occur because the contrast agent can stimulate taste receptors in taste cells. A warm flush feeling at the injection site, head/neck and pelvic areas is also common. Iodine is a vasodilator so large blood vessels will have an even larger volume of blood creating a warm sensation. Higher rates of injections (more than 3ml/s) generally exacerbate the intensity of these reactions/feelings.

Answer 11

Leakage of intravenously administered contrast media from the normal intravascular compartment into surrounding soft tissues Complication rather than a reaction. Patient can experience pain, swelling, tightness, redness depending on the volume extravasated. Administration of contrast/examination will need to be stopped immediately. Follow protocol for dealing with extravasation.

Answer 12

Follow departmental protocol for administration of all contrast agents and dealing with reactions. Use the least amount of contrast agent required for the examination (body weight based). Patient should be well hydrated prior administration of IV contrast. Patients should not be left alone following administration of contrast media. Know the location of the resuscitation medication and equipment. The IV cannula used for the administration of contrast media should be left in situ for ≥ 15 minutes post injection.

Answer 13

Ideal Qualities of a Contrast Agent Excellent x-ray absorption characteristics at the x-ray energies used in diagnostic imaging Chemical and thermal stability High solubility and low viscosity Non-antigenic (does not illicit an immune response) and low toxicity Does not affect physiological homeostasis Low/Iso-osmolar for minimal osmotic effects Low renal load and effective excretion Readily available and inexpensive