Contrast Agents Flashcards
why is contrast used
it alters the appearance of the tissues of interest to enhance clinically relevant information
- physiological functions/performance
- vasculature
- assist in defining borders between normal and abnormal structures/processes
improves diagnostic confidence in
- pathology
- inflammation
- infection
- measurements such as relative perfusion/function
common agent used in MRI
gadolinium (Gd)
generally considered safe with low risk of adverse effects
patient consent
must sign a consent from stating the risks associated with Gd administration
contains risks
- survey on allergies and previous use
- pregnancy risk
- medical condition
- patient must have the opportunity to ask questions
2 different contrast agents and their pharmacokinetics options
Gadolinium based
- extracellular fluid
- hepatobiliary
iron based
- intravascular
mild/moderate reaction from agents
hives
rash
itchiness
coughing
temporary nausea
acute adverse reactions
difficulty breathing, heart racing, anaphylaxis
contraindications for contrast use
previous severe reaction
renal failure
pregnancy
patients at highest risk of negative outcome
previous reaction to a Gd chelate
previous reaction to iodinated contrast
previous reaction to other medical or non medical substances
have asthma
are pregnant
are lactating
are patients with end-stage, severe and possibly moderate renal failure
precautions for pregnant, previous reaction to Gd chelate and or patients with end stage, severe and moderate renal failure
seek possibility of alternate non contrast solution or alternate imaging modality
rare that this risk would outweigh benefit
precautions for previous reaction to other medical or non medical substances, asthma, and allergies
monitor closely for any adverse reaction as increased chance of immediate hypersensitivity reactions such as itching/hives within one hour
will not guarantee that they will have adverse reaction, however, some patients are reactive to almost any basic injections/medication
precautions for breast feeding
informed consent that the trace amount that may be present has not presented evidence of harm to a baby
is okay to proceed with Gd if required for diagnosis in the MRI scan
has the option of expressing and discarding milk prior to breast feeding again after 24 hours is the advice for concerned mothers who want full precautions
When does arterial phase occur?
35 to 40 seconds
When does hepatic or portal phase occur?
70 to 80 seconds
What affects the flow rate of contrast?
Volume of contrast administered, patients weight, larger volumes of contrast = faster flow
What is extravasation?
The leakage of an intravenous drug from the vein to the surrounding tissues, severe injuries over 100ml
