Contrast Media Reactions & Pharmacology of Angiographic ProceduresBontrager Chapter 17

Contrast media creates positive or negative contrast

Ingested Retrograde Intrathecal Parentaeral

UGI, Esoph, SBFT, OCG

BaE, ERCP, Hysterosalpingiogram, Cystogram

Myelogram, Arthrogram

IVU, Veonogram, Arteriogram

Iodine

Iodine: atomic number 53.

Essential for nutrition, abundant in thyroid.

Principle ingredient in the surgical scrub, betadine

Non-metallic, commonly found in salt water swamps or brackish waters,in grayish-black, lustrous plates or granules.

A halogen (group VII elements including fluorine, bromine, and chlorine), iodine readily binds to salt.

Original “ionic” iodine contrasts were bound to sodium or meglumine salt. When injected, the molecule begins to disassociate, releasing ionic particles (+ cation and - anion) at a concentration 4 to 8 times higher than the particle content of blood (Osmolality).

127 53

Characteristics of Ionic Contrast

Iodine concentration determines the radiopacity of the agent. Measured in %weight/volume. Ranges from 10 to 82, dependent on its use. Many products include the concentration of iodine salts in the brand name: Renografin-60, Hexabrix 76, Isovue-200 (20%). See appendix L in Patient Care in Radiography.

Water soluable. Unlike barium in suspension, iodine preparations must mix with blood.

Stable in solution. The iodine molecule must remain in solution. Productsthat do not meet this requirement are packages as a solute, and solvent.

Low viscosity. The thickness of an agent significantly affects the ease in which a bolus is injected, and the rate of drip infusion.

Low toxicity. Any preparation not natural to the body is toxic to some degree, as are natural substances given in excess. The goal of contrast media is to keep adverse reactions to a minimum.

Low osmolality. The number of particles in solution is the chief factor of toxicity.

Chemical Composition

Chemical composition of ionic contrast media

Six sided Benzyl ring: Tri-iodinated Benzoic acid

Benzoic acid. White crystiline acid in benzoin (from the resin ofthe kincense tree, also found in cranberries). Used as a preservative and binding agent in food medicine, and perfume.

I

I

I

Iodine

Iodine: atomic number 53. 3 x denser than bone, 5 x denser than soft tissue

Essential for nutrition, abundant in thyroid.

Principle ingredient in the surgical scrub, betadine

Non-metallic, commonly found in salt water swamps or brackish watersin grayish-black, lustrous plates or granules.

A halogen (group VII elements including fluorine, bromine, and chlorine), iodine readily binds to salt.

127 53

Six sided Benzyl ring of ionic contrast: Tri-iodinated Benzoic acid

“Ionic” iodine contrasts are bound to sodium, calcium, magnesium, or meglumine salts.

The concentration of ionic contrast refers to the amount of salt in solution

When injected, the molecule begins to dissociate, releasing ionic particles (+ cation and - anion) at a concentration 4 to 8 (3-10) times higher than the particle content of blood

Terms: Osmolality, Isotonic, Hypertonic, Chemotoxicity, Osmotoxicity.

Normal capillary action(Balance of blood and osmotic pressure)

arteriole venule

BP>OP OP>BP

*

** *

**

= RBC = proteins

H20H20

The Osmotic Effect

1. As contrastis injectedosmolalityincreases

2. Blood entering the capillary bed ishypertonic to the fluid in the surrounding tissues.

3. Extravascular fluid crosses the semi-permeable membrane of the capillary to achieve isotonicity, causing hypervolemia

4. Fluid drawn from RBCs causes sickling.

5. Epithelial cells lining the intimal wall are similarly effected, and can lead to inflammation and thrombophlebitis

6. Flexibility of vessels walls allow vasodilation to accomodate hypervolemia.

Ionic versus Nonionic Contrast

Ionics: Dissociate into + and – particles High osmolality (2-8 x) Disrupts electrolyte balance

Nonionics: Do not dissociate 2 x blood plasma Electrolyte balance maintained Costs 10-20 times more Higher viscosity

Nonionic contrast substitutes noniodine parts of the benzoic ring witha nonionizing side chain.

Osmolality of plasma = 300 millimoles/kg “ “ nonionics = 750 “ “ “ ionics = 1000-2400

Nonionic, low-osmolality contrast agents (LOACs)Quickly became popular in the late 1980s

Nonionics do not dissociate. Fewer particles means lower osmolalitythan ionics. The cost is significantly greater, but comes with the promise of fewer contrast reactions.

From Patient Care in Radiography,5th edition. pg.269.

Contrast Reactions

Classified as Mild, Moderate, Severe and Fatal

1. Vasomotor (mild or “normal”) * feeling warm, flushed * pallor * nausea * mild urticaria * anxiety * syncope (preceded by dizziness, lightheadedness)

4 Types of reactions

1. Vasomotor reactions: result from the actions of nerves that innervate vessel walls.

increase in impulses = constrictiondecrease in impulses = dilation

Urticaria or hives result frombug bites (single), from allergic reactions they range fromscattered to giant.

Contrast Reactions

Classified as Mild, Moderate, Severe and Fatal

2. Anaphylactic (true allergic reaction) * can resemble vasomotor * can escalate * Edema (larynx) laryngospasm * Asthma like signs * Moderate to severe urticaria (giant hives) * Angioedema * Hypotension * Tachycardia

4 Types of reactions

2. Anaphylactic reactions: Sudden release of immunilogic mediators (antibodies from previous exposures) starts a cascade effect, Not dose related

* vasodilation* permeability of capillaries* Smooth muscle spasm* urticaria

Contrast Reactions

3. Vasovagal reactions (severe) * Interference with cardiac conduction * Dysrhythmia * Hypotension * Absent pulse * Convulsions

Vagus, 10th

cranial. Knownas the “wandering nerve.”

4 Types of reactions

Contrast Reactions

Classified as Mild, Moderate, Severe and Fatal

4. Acute renal failure * Anuria * Torpor * Disorientation

4 Types of reactions

Apathy, inactivitysluggishness

Contrast Reaction Treatments

1. Vasomotor (“normal”) * feeling warm, flushed * nausea * mild urticaria

Treatment: Reassurance, monitoring,

Diphenhydramine (Benadryl) for hives.Benadryl is an antihistimine used foranaphylactic reactions.

Patients with a known sensitivity may be administered Benadryl before theprocedure

Contrast Reaction Treatments

2. Anaphylactic (true allergic reaction) * can resemble vasomotor * can escalate * Edema (larynx) * Asthma like signs * Giant Hives * Hypotension, tachycardia

Treatment: Epinephrine (IV best) beta z agonist when epi fails Benadryl Tagamet/Zantac IV fluid (rapid) O2 Corticosteroids

Steroids = sex hormonesCortico = from cortex of adrenal gland (or synthetic)

Treats inflammation, asthmadermatitis.

Agonists = drugs that mimicthe bodies regulatory functions.

Beta agonists treat COPD, asthma. Beta z stimulatebronchodilation

Epinephrine for bronchospasm.Vasodilator for hypotension

Contrast Reaction Treatments

3. Vagal reactions * Interference with cardiac conduction * Dysrhythmia * Bradycardia * Hypotension * Absent pulse * Convulsions

Treatment: Epinephrine IV Atropine IV Lidocaine IV O2 Sodium Bicarbonate Diazepam (Valium) IV

Atropine for bradycardia

Sodium Bicarb formetabolic acidosis

Valium for spasm, convulsions,anxiexty

Contrast Reaction Treatments

4. Acute renal failure * Anuria * Torpor * Disorientation

Conservative to aggressive treatment

What two labs tests measure renal function?

Creatinine .6-1.5 mg/ml serumBUN 8-20 mg/ml serum

Preparing to inject

* Stock should be rotated, lots not mixed

* Inspect vial before drawing up. Assure correct media, check color, expiration date, flaws in glass.

* Do not swab rubber stoppers of unopened vials.

* Patient history and allergies * Previous injection of contrast without problem does not preclude a reaction

* Previous reactions do not guarantee subsequent reactions, but are deemed high risk

* Do not discard vials until after the case

Contraindications:

Glucophage – med for diabetes mellitus. When combined with contrast increases the risk of renal failure. Recommended to be withheld 48 hrs prior to and following contrast administration

Multiple myeloma - Malignancy of bone that leads to renal failure, and increases the risk of contrast reactions.

Azotemia (uremia)- High levels of nitrogen waste in blood. Laboratory tests BUN (blood urea nitrogen) should be 8 – 25 mg/100 ml. Another test for nitrogen waste, Creatinine levels, should be .6 to 1.5 mg/dl.

Contraindications continued:

Hypersensitivity to iodine Anuria – no excretion of urine Severe renal disease or failure

Congestive heart disease (CHF)

Sickle cell anemia Pheochromocytoma – tumor of the kidney

In certain cases, an IVU may be performed despite contraindications. Patients should be well hydrated to lessen the risks.