Contrast Media Flashcards
What are the types of contrast media?
Positive and negative
What are types of positive contrast media (administration)?
Oral or IV
What are examples of positive contrast media?
- Iodine
- Barium
How do positive contrast media appear radiographically?
High density and white
What are types of negative contrast media (administration)?
CO2 or room air (rectal) or gas crystal
How does negative contrast media appear radiographically?
Low density and black
What is osmolality?
Number of particles in a solution per unit liquid
What is viscosity?
Thickness or friction of the fluid as it flows
What is iconicity?
Whether a solution contains molecules that form ions or not (aka ionic or non ionic)
What is clearance?
The body distributing and excreting the iodinated contrast through the kidneys
The body excretes contrast nearly exclusively by the kidneys via . . .
Glomerular filtration
What is the half life of contrast in a patient with normal renal function?
2 hours
What do LOCM and HOCM stand for?
LOCM = Low Osmolality Contrast Media
HOCM = High Osmolality Contrast Media
What type of IVs are used for venous access?
Indwelling catheter or CVC (if there is one)
What is the best vein to use for venous access?
Median cubital
What may need to be changed if a small vein is used to contrast?
Injection rate
What medical history may be gathered during pre injection interviews (aka contraindication)?
- Allergies
- Asthma
- Renal function
- Thyroid disease
- Pregnancy
- Diabetic (on metformin)
What lab work must be gathered and considered before contrast administration?
Creatinine and GFR
What basic information must be gathered during patient preparation(4)?
- Medical history
- Lab work
- Patient educating about exam and informed consent
- Documentation
What type of contrast can cause adverse reactions?
Iodinated contrast
What are the types of contrast adverse reactions(3)?
- Mild
- Moderate
- Severe
What are symptoms of a mild adverse reaction?
Cough, itching, hives, eye swelling, nasal congestion
What is the treatment for mild adverse reactions?
Over the counter antihistamines (ex: Benadryl)
What is the role of the tech during mild adverse reactions?
Monitor the patient and tell radiologist
What are symptoms of moderate adverse reactions?
Respiratory difficulty, pulse change, hyper or hypotension
What is the treatment for moderate adverse reactions?
IV Benadryl
What is the role of the tech for moderate adverse reactions?
Assess vitals, inform rad
*maintain IV access in case drug admin is required or out one back in!
What are symptoms of a severe adverse reaction?
Substantial respiratory distress, unresponsive, convulsions, cardiac arrest
What is the treatment of a severe adverse reaction?
CPR or oxygen or something
What is the role of the tech in a severe adverse reaction?
Call a code blue and alert the rad, be an extra set of hands but get out of the way
What do you do if a patient has had a previous contrast allergic reaction?
- Change the contrast agent (omnipaque or isovue)
- Premeditate the patient
How do you pre medicate the patient before an exam with a contrast allergy?
13 hrs before appt: 50mg or prednisone
7 hrs before appt: 50mg or prednisone
1 hr before appt: 50mg of prednisone + 50mg diphenhydramine/20mg cetirizine
What causes chemotoxic reactions?
Physicochemical properties of contrast media, dose, and speed of injection
What might happen if metformin is taken during exam and kidney function changes?
May cause lactic acidosis
What might happen if metformin is taken during exam and kidney function changes?
May cause lactic acidosis
What is CIN?
Contrast Induced Nephropathy
Toxicity to kidneys due to acute increases in SeCr
What is extravasation?
Leakage of blood or other fluid (i.e. contrast) into surrounding tissue causing inflammation
Ways to avoid extravasation
- Indwelling catheter with flexible cannula (18 to 20 gauge)
- Monitor injection site
- Keep contrast media warm
- Use LOCM
How do you treat extravasation?
- Stop injecting
- Notify rad
- Elevate + apply ice pack
What are complications of extravasation?
Ulceration, necrosis, compartment syndrome
What are the three phases of tissue enhancement?
- Bolus/arterial phase
- Non equilibrium phase
- Equilibrium phase
Bolus phase
Starts: ~20 sec after injection
Contrast starts in peripheral vein, through mediastinum, to and out of the aorta (appear bright)
*cortex of kidney enhanced
Nonequilibrium phase
Starts: ~60 to 80 sec after injection
Venous structures now appear opacified, liver parenchyma bright as well
Homogenous kidney enhancement (in tubules now)
Equilibrium phase
Starts: 2 min after Bolus phase
Highlights organ parenchyma, not vascular structures enhanced
Kidneys no longer enhanced
What factors affect enhancement quality?
- Patient weight
- Cardiac output
- Scan speed (delay increases = duration decreases)
