Presentation on theme: "Contrast Media Reactions & Pharmacology of Angiographic Procedures Bontrager Chapter 17 Contrast media creates positive or negative contrast Ingested Retrograde."— Presentation transcript:
Contrast Media Reactions & Pharmacology of Angiographic Procedures Bontrager 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)
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. Products that 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 of the 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 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 waters in grayish-black, lustrous plates or granules. A halogen (group VII elements including fluorine, bromine, and chlorine), iodine readily binds to salt
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 H20H20
The Osmotic Effect 1. As contrast is injected osmolality increases 2. Blood entering the capillary bed is hypertonic 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 times more Higher viscosity Nonionic contrast substitutes noniodine parts of the benzoic ring with a nonionizing side chain. Osmolality of plasma = 300 millimoles/kg “ “ nonionics = 750 “ “ “ ionics =
Nonionic, low-osmolality contrast agents (LOACs) Quickly became popular in the late 1980s Nonionics do not dissociate. Fewer particles means lower osmolality than ionics. The cost is significantly greater, but comes with the promise of fewer contrast reactions. From Patient Care in Radiography, 5 th 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 = constriction decrease in impulses = dilation Urticaria or hives result from bug bites (single), from allergic reactions they range from scattered 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, 10 th cranial. Known as 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, inactivity sluggishness
Contrast Reaction Treatments 1. Vasomotor (“normal”) * feeling warm, flushed * nausea * mild urticaria Treatment: Reassurance, monitoring, Diphenhydramine (Benadryl) for hives. Benadryl is an antihistimine used for anaphylactic reactions. Patients with a known sensitivity may be administered Benadryl before the procedure
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) O 2 Corticosteroids Steroids = sex hormones Cortico = from cortex of adrenal gland (or synthetic) Treats inflammation, asthma dermatitis. Agonists = drugs that mimic the bodies regulatory functions. Beta agonists treat COPD, asthma. Beta z stimulate bronchodilation 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 O 2 Sodium Bicarbonate Diazepam (Valium) IV Atropine for bradycardia Sodium Bicarb for metabolic 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 mg/ml serum BUN 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.