CONTRAST MEDIA

CONTRAST MEDIA

A. Negative contrast agent

1. Most commonly used agent is air

2. Requires fewer x-rays and produces a higher density

on the image

3. Air may be used in combination with a positive contrast

agent on double-contrast studies

4. Most common examination performed using a negative

contrast agent is a routine chest radiograph

B. Positive contrast agents

1. Examples

a. Iodine (atomic number 53)

b. Barium (atomic number 56)

2. Relatively high atomic numbers

a. Result in greater attenuation of x-rays

b. Provide lower density on radiograph

c. Provide an increase in contrast between structure

to be visualized and surrounding structures

C. Barium

1. Administered to patient in the form of barium sulfate,

an inert salt

2. For upper GI series and esophagogram, barium is

most palatable when mixed with very cold water

3. For barium enema, barium powder is mixed with

water at a temperature of approximately 100° F

4. For some studies of esophagus, barium sulfate paste,

which is much thicker and more difficult to swallow,

may be administered

5. Barium tends to absorb water

6. Patients must be given careful instructions regarding

fluid intake after barium studies so that the barium

does not cause an impaction

7. Barium sulfate escaping into the peritoneal cavity can

cause peritonitis

D. Aqueous iodine compounds

1. Used for contrast studies of GI tract

2. Used when barium could be a surgical contaminant

a. Perforated ulcers

b. Ruptured appendix

3. Aqueous iodine compounds may also be used in

patients at high risk for impactions

4. These compounds may cause significant dehydration

E. Iodinated contrast media

1. Ionic contrast agents

a. Salts of organic iodine compounds

b. Composed of positively and negatively charged

ions

2. Nonionic contrast agents

a. Similar to ionic contrast agents

b. Do not ionize into separate positive and negative

charges, which affords their primary advantage

over ionic contrast agents

c. Provide far lower incidence of contrast agent

reactions

3. Contraindications to use of iodinated contrast

media

a. Previous sensitivity to contrast agents

b. Known sensitivity to iodine

4. Both ionic and nonionic contrast agents are iodinated

(i.e., both contain various concentrations of iodine—

nonionic does not mean noniodinated) 

History and Patient Care Preceding Injection

of Iodinated Contrast Media

A. Determine history of allergies or previous hypersensitivity

to contrast media

B. Determine extent of patient’s medical problems, including

medications being taken

C. Review possible reactions to contrast medium being

used; determine the presence of contraindications

D. Verify pertinent laboratory values (blood urea nitrogen

(BUN), creatinine, and glomerular filtration rate) per

department and contrast agent protocol

E. Verify appropriate dosage related to patient weight and

age

F. Know the location of all emergency equipment

G. Obtain informed consent from patient per department

protocol

H. Carefully observe and evaluate the patient, noting color

of skin, tone and pitch of voice, and presence of apprehension

or anxiety, so that changes from these baseline

observations may be noted after injection

Patient Care Following Injection of Iodinated

Contrast Media

A. Continue conversation with patient

1. Encourage patient to speak

2. Laryngeal swelling as a contrast agent reaction first

manifests as a change in the tone and pitch of the

patient’s voice

B. Continue to observe the patient for early signs of urticaria,

profuse sweating, or extreme anxiety

C. If patient becomes overanxious, take patient’s pulse to

determine whether tachycardia is present

D. If patient becomes faint, immediately check respirations,

pulse, and blood pressure, and observe for signs of cyanosis

E. Be aware of the location of a physician in the event of an

emergency, such as a contrast agent reaction

F. Remain with the patient (except when at the control

panel to make exposures)

1. Patient should never be left alone after injection or at

any time during the procedure

2. Although most contrast media reactions are noticeable

and may even be violent, others are more difficult

to observe

a. A patient who appears to be resting comfortably

or sleeping may have experienced cardiac

arrest

3. Summon help immediately on observing the onset of

a contrast agent reaction

a. Although a calm response is required to avoid

alarming the patient, urgency is important because

a mild contrast agent reaction may quickly accelerate

into a more serious reaction

Reactions

A. Overdose: May occur in infants or adults who have renal,

cardiac, or hepatic failure

B. Anaphylactic reactions: Flushing, hives, nausea

C. Cardiovascular reactions: Hypotension, tachycardia, cardiac

arrest

D. Psychogenic factors: May be caused by patient anxiety or

suggested by the possible reactions described during the

informed consent process

E. Other symptoms of contrast agent reactions

1. Nausea and vomiting

2. Sneezing

3. Sensation of heat

4. Itching

5. Hoarseness (or change in pitch of voice during

conversation)

6. Coughing

7. Urticaria

8. Dyspnea

9. Loss of consciousness

10. Convulsions

11. Cardiac arrest

12. Paralysis

13. Any change in level of orientation

F. Complications may occur at site of injection

1. Local irritation may occur if contrast material

extravasates

2. Phlebitis may occur in the vein in which contrast

material was injected