contrast media Flashcards
subject contrast
the radiographic contrast caused by the difference in the composition of the patient’s body tissues
contrast media
diagnostic agents that are introduced into the body or injected into the vascular system, joints, and ducts to enhance subject contrast in anatomic areas where low subject contrast exists
types of contrast media
- radiolucent (negative) contrast agents
- radiopaque (positive) contrast agents
- specialty contrast agents
- radiolucent/negative contrast agents
composed of elements with low atomic numbers administered as: gas or carbon dioxide produce areas of increased density appears black or dark on radiograph
what is the most common negative contrast agent
room air
double contrast agents
when a negative contrast agent is combined with a positive contrast agent
types of negative contrast agents
gas, CO2, air
negative contrast agents must NEVER…..
be injected intravenously
serious/ fatal consequences can occur
- positive/ radiopaque contrast agents
composed of elements with a high atomic number
appears bright on a radiograph
more absorption of xray beam
examples of positive contrast agents
barium
iodine
soft tissue atomic number
7.4
barium atomic number
56
iodine atomic number
53
gadolinium
a positive contrast agent used in MRI
atomic number of 64
barium sulfate
inert powder composed of crystals that are used for examination of digestive system
barium sulfate is combined with what to form barium sulfate
oxygen and sulfate
what is the chemical formula for barium sulfate
BaSO4
a mixture of barium sulfate and water forms a
colloidal suspension not a solution
Barium sulfate never dissolves in what
water
flocculation
when the powder has a tendency to clump and come out of its suspension when in the body
what is used to prevent flocculation
stabilizing agents
ex: sodium carbonate or sodium citrate
enternal
within, or by way of the intestine or gastrointestinal tract
intrathecal
introduced into or occurring in the space under the arachnoid membrane of the spinal cord of the brain
(into subarachnoid space)
contraindications of barium sulfate
suspected perforation ( barium is not absorbed by body) if barium enters peritoneal cavity may need to be surgically removed
when patients have a history of suspected perforation, what should be used instead of barium sulfate
a water soluble iodine contrast agent
AKA gastrografin gastroview hypaque
Adverse reactions of barium sulfate
obstruction/constipation extravasation vaginal rupture hypervolemia allergic reactions sedated patients barium in appendix
obstruction/ constipation
pts. instructed to drink lots of water after barium sulfate
barium residue in the colon can dry and cause pt. to become constipated
bowel obstruction may occur if they don’t drink enough water
extravasation
leakage from a vessel into the tissue
happens if barium leaks from the GI tract into abdominal cavity
can lead to peritonitis
what patients are at risk for extravasation
pts. with diverticulitis or ulcerative colitis
vaginal rupture
rare complication
due to misplacement of catheter before lower GI exams.
female pts. should be asked if they can feel the tip in their rectum.
hypervolemia
blood disorder consisting of an increase in the volume of circulating blood
happens when water from the BE is shifted from colon into the circulatory system
what is added to barium sulfate to reduce the possibility of hypervolemia
table salt
allergic reactions
due to preservatives in the barium sulfate or latex in the BE catheter
sedated pts.
can cause aspiration because they are not conscious
barium in appendix
no directly related complications have resulted from this
iodinated contrast media are available as :
- oil based
2. water soluble
T or F
oil based contrast media is relatively limited in radiography
TRUE
what are oil based contrast media still possibly used for today?
lymphangiograms and bronchograms
oil based contrast media are not miscible with blood, therefore…..
should never be injected intravenously or interarterially
the fatty acid base of oil based contrast media are responsible for….
making the solution viscous and insoluble in water
T or F
oil based contrast media needs to be stored in a cool dark area
True
plastic syringes should not be used for injection of oil based contrast because
toxic substances from the plastic can dissolve into the media
MAIN disadvantage of oil based contrast media
they persist in the body because they are insoluble in water
adverse reactions of oil based contrast media
anaphylactoid (allergic like) reaction anaphylactic shock pooling of blood can cause shock, respiratory failure, death the more abrupt, the more severe
the most common cause of anaphylaxis are
medications, iodinated contrast agents, and insect venoms
water soluble contrast media
low toxicity
generally absorbed by the body and excreted wihtin 24 hours
2 types of water soluble contrast
- ionic iodinated contrast media
2. nonionic iodinated contrast media
ionic iodine contrast media
dissociate into 2 molecular particles in water or blood plasma
one has a negative charge and the other a positive charge
ionic iodine contrast media molecule
ANION PART
starts with six carbon bonded hexagon called a benzene ring
every other carbon site has an iodine atom which makes it triiodinated
of the 3 remaining carbon sites, one has a negatively charged acid group
the other 2 carbon sites are R2 and R3
purpose of R2 and R3
increase the solubility or excretion rate of the contrast by the body
ionic iodine contrast media molecule
CATION PART
salts
once injected, the cation separtaes from the anion and creates 2 separate ions in teh blood
the separtaion creates an increase in the blood plasma
osmolality
refers to the concentration or number of particles in the solution per kilogram of water and is directly related to the occurrence of adverse reactions
nonionic contrast media =
low osmolality
ionic contrast media =
high osmolality
True or False
ionic contrast agent may increase probability of a contrast media reaction
True
osmolality of blood plasma
300 osmol/kg
on average ionic iodinated contrast agents range from
1000 to 2400 osmol/kg
way higher than blood plasma
osmolality of nonionic iodinated contrast agents is around
750 osmol/kg
much closer to blood plasma
nonionic iodinated contrast media
developed to reduce the side effects of the ionic iodinated contrast media
these molecules do not separate in the solution
nonionic iodinated contrast media molecule
tri iodinated benzene ring
does NOT carry an acid group
hydroxyl groups surround the benzene rings (increase the solubility of the media in blood plasma)
T or F
warming contrast media reduces viscosity making it thin
TRUE
allergic like effects of water soluble iodinated contrast media
urticaria (hives)
wheeing and edema
bronchospasm
nausea/ vommiting
renal effects of water soluble iodinated contrast media
increased secretion of urine with dehydration
diminished blood supply to the kidneys
T or F
patients with elevated blood levels have a greater chance of experiencing an adverse contrast media
TRUE
normal cratinine levels for the adult are
0.6 to 1.5 mg/dl
BUN levels for an adult should range between
8 to 25 mg/100 mL
