DRUG CLASSIFICATIONS, CHEMISTRY, & PHARMACOLOGY OF CONTRAST AGENTS Flashcards
These are high-density pharmacologic agents used to visualize low-contrast tissues in the body, such as the vasculature, kidneys, gastrointestinal (GI) tract, and biliary tree.
RADIOPAQUE CONTRAST AGENTS
(ROCM)
MOST FREQUENTLY PRESCRIBED ROCM
Iodine
barium
atomic number 53
IODINE
atomic number 56
BARIUM
MOST FREQUENTLY PRESCRIBED ROCM
LOW-KILOVOLTAGE (below 80 kVp)
HIGHER KILOVOLTAGE (above 90 kVp)
usually selected to produce high-contrast radiographs of the blood vessels or genitourinary tract.
LOW-KILOVOLTAGE (below 80 kVp)
used in GI examinations not only to reveal the presence of the organ, but also to penetrate the contrast media to see the walls and inner structures.
HIGHER KILOVOLTAGE (above 90 kVp)
are available in parenteral and enteral, ionic and nonionic, and high-osmolality and low-osmolality forms. With the exception of barium, used for roentgenography are derivatives of triiodinated benzoic acid
ROCM
It is the movement of water across semipermeable membrane.
OSMOSIS
It controls the distribution and movement of water between body compartments. It is also the number of milliosmoles per kilogram of water (mOsm/kg), or the concentration of molecules per weight of water.
OSMOLALITY
It is the number of milliosmoles per liter of solution (mOsm/L), or the concentration of molecules per volume of solution.
Sometimes the difference between the two measurements is insignificant.
OSMOLARITY
Used to add density to vascular structures. Increased density of the media alters the attenuation of x-rays passing through the area, thus enhancing the anatomic image on the radiographic film.
INTRAVASCULAR RADIOPAQUE CM
Diagnostic effects of intravascular radiopaque contrast media (ROCM) are a function of the iodine contained within them. Adverse effects elicited by ROCM depend at least partially on their serum or tissue iodine concentration and osmolality and their calcium-chelating, anticoagulant, and immune system-stimulating abilities.
IODINATED RADIOPAQUE CM
Must be within the range of 280 to 370 mg/ml for a normal x-ray film to reflect the vascular lumen.
For computed tomography (CT) or digital subtraction angiography (DSA), the serum iodine Concentration needs only to be between 2 and 8 mg/ml.
SERUM IODINE CONCENTRATION
An estimated one of every 20,000 to 40,000 patients receiving ROCM dies as a result of these adverse effects.
Although the odds of death appear low, they become very real if it happens to you or your patient. Thus, it is paramount that the technologist understand adverse effects so that proper actions can be instituted as rapidly as possible.
ADVERSE PHARMACODYNAMICS
• Various physiologic effects.
• Intravascular administration of ROCM will cause a transient rise in intravascular osmotic pressure.
• These effects will cause fluid extraction from red blood cells (RBCs),endothelium, and theextravascular space.
OSMOLALITY EFFECTS
• These receptors cause the autonomic nervous system to slow down the heart rate (bradycardia) and produce a drop in aortic pressure.
• patient may faint or lose consciousness which ahs been referred to as a vasovagal reaction
BARORECEPTORS & CHEMORECEPTORS
ROCM can chelate (bind to) calcium cardiovascular system after injection.
CHELATION EFFECTS
May be one pharmacodynamic mechanism by which adverse heart rhythms, such as pulseless electrical activity (PEA), cardiac arrest, and sudden death, occur in a minority of patients receiving intravascular ROCM.
CALCIUM CHELATION
CHELATION EFFECTS
PULSELESS ELECTRICAL ACTIVITY (PEA)
CARDIAC ARREST
A heart rhythm disturbance characterized by electrical impulses without cardiac contraction. The heart monitor shows electrical activity, but the heart is not pumping.
PULSELESS ELECTRICAL ACTIVITY (PEA)
The heart has ceased to pump blood effectively to maintain life
CARDIAC ARREST
This can theoretically result in bleeding and bruising episodes. Low-osmolality ROCM do not appear to produce anticoagulant effects.
ANTICOAGULATION EFFECTS
The immune system is highly complex and consists of various components, including physical barriers and biochemical defenses.
• The biochemical defenses are thought to have a role in the immediately life-threatening reaction mimicking an anaphylactic reaction that can occur with ROCM.
IMMUNE SYSTEM-LIKE EFFECTS
• A life-threatening, systemic hypersensitivity reaction.
• Patients suffering anaphylaxis may exhibit any combination of nausea, vomiting, diarrhea, hives, rash, flushing, cyanosis, pallor, lightheadedness, unconsciousness, seizures, stridor, wheezing, respiratory distress, bronchospasm, & etc.
ANAPHYLAXIS (type I hypersensitivity reaction)
ROCM are responsible for approximately 10% of all acute renal failure (ARF) events and are the third most common cause of hospital-acquired ARF.
RENAL DYSFUNCTION
Urine output does not exceed 400 ml/day in these patients. The renal failure may not be reversible, and the serum creatinine does not normalize.
OLIGURIC ARF
• New agent for treating hypertensive emergencies
• This medication has potent vasodilatory effects through stimulation of the dopamine-1 receptor.
FENOLDOPAM
Available as a 10% or 20% (100 or 200 mg/ml) respiratory nebulization solution and as an IV form.
ACETYLCYSTEINE
Effects of sodium bicarbonate IV solution possible prophylactic strategy against development of renal failure secondary to ROCM.
SODIUM BICARBONATE
• Occurs in patients who have decompensated thyrotoxicosis, a condition in which the body becomes unable to tolerate thyroid hormones.
• Signs and symptoms of thyroid storm include fever, tachycardia (rapid heart rate), diaphoresis (sweating), agitation, nervousness, and emotional instability
THYROID STORM
Include nausea, vomiting, flushing with a generalized feeling of warmth, rhinitis, lacrimation, sneezing, itching, rash, angioedema, generalized edema, cramps, excessive salivation, salivary gland swelling, diaphoresis, retching and choking, metallic taste in mouth, decreased white blood cells, chills, fever,and disseminated intravascular coagulation (DIC).
GENERAL ADVERSE REACTIONS
Vasovagal reactions,hypotension,
hypertension, syncope,tachycardia, pallor,chest pain, and cardiac arrest.
CARDIOVASCULAR EVENTS
Dizziness, paresthesias, drowsiness, weakness, thirst, headache, and seizures.
CNS ADVERSE EFFECTS
General gastric pain, nausea, vomiting, sialorrhea (excessive salivation), xerostomia (too little salivation), and dysgeusia (bad taste in mouth).
GASTROINTESTINAL ADVERSE EFFECTS
Adverse effects that may be seen after the use of the ferumoxide compounds (iron compounds), such as ferumoxtran-10 (Combidex), iron oxide (Clariscan), and ferumoxytol, include hypotension if infused too rapidly; it is recommended not to exceed 25 to 30 ml/hr.
FERUMOXIDE COMPOUNDS
Adverse effects from the manganese compounds, such as mangafodipir trisodium (Teslascan), may include chest pain and “mare forceful heartbeat,” peripheral vasodilation (flushing), headache, dizziness, lightheadedness, (flushing), nausea dyspepsia,vomiting, and abdominal pain.
MANGANESE COMPOUNDS
Adverse effects include QT prolongation on the electrocardiogram in up to 30% of patients administered perflutren. Dizziness, ventricular dysrhythmias, and chest pain occur infrequently with either octafluoropropane albumin microspheres or perflutren.
ULTRASOUND MICROBUBBLE AGENT ADVERSE REACTIONS
has been reported in numerous patients receiving the albumin microsphere octafluoropropane.
Anaphylaxis
The imaging technologist should use a screening method that includes the assessment of patient medical history and current renal function status
SCREENING
Box 7-1 QUESTIONS TO BE ANSWERED BEFORE ADMINISTRATION OF ROCM
- History of allergies to medications?
- History of intolerance to iodine?
- History of adverse reactions to radiopaque contrast media?
- History of asthma or breathing difficulties?
- History of cardiac disease?
a. Congestive failure
b. Cardiac dysrhythmias
c. Hypertension
d. Hypotension - History of renal disease?
.Chronic renal failure a b. Acute renal failure
c. Current blood urea nitrogen (BUN) concentration (renal function test)
d. Current serum creatinine concentration (renal function test) - Current medications?
- History of diabetes?
- History of sickle cell anemia (in black patients)?
- History of multiple myeloma?
- Is the patient pregnant (females)?
- Current central nervous system trauma?
IV drug may be required to improve visualization in vascular bed or a to Counteract severe adverse effects that may result from ROCM.
DRUG-DRUG INTERACTIONS
• May occur between ROCM and these adjunct drugs.
• Chemical incompatibilities that produce insoluble precipitates can theoretically lead to occlusion of IV catheters and chemically induced embolism that can occlude small vessels in its path.
DRUG-DRUG INTERACTIONS
In the GI tract, barium sulfate produces an insoluble precipitate with calcium to form barium fecaliths effects
BARIUM SULFATE
of barium sulfate into the lungs generally does not cause harm, provided the amount aspirated is small
Aspiration
Can cause both gastrointestinal (GI) and respiratory adverse.
ENTERAL BARIUM SULFATE
Six rights of drug
the right drug
the right patient
the right time
the right location
the right documentation
The drug ordered is appropriate for the patient.
THE RIGHT DRUG
Medication is given to the intended patient
THE RIGHT PATIENT
Give the medication at the right time ordered according to agency policy.
THE RIGHT TIME
Give the medication by the ordered route.
THE RIGHT LOCATION
Document medication administrattion after giving it, not before
THE RIGHT DOCUMENTATION
