lec 4- contrast media 1 Flashcards
outline the steps to preparing the patient for a contrast procedure
- Patient pre-admission preparation
- Admission pre-preparation procedures
- The procedure
- Immediate post procedural care
- Post discharge care
why use contrast
- Contrast Media changes the attenuation of x-rays of a particular organ with respect to the surrounding tissues/organs.
- The contrast media increases the overall “contrast” of the x-ray image via attenuation properties
define contras medium/media
generic name given to substances that are administered to enhance the contrast of an x-ray via attenuation
define positive contrast
usually a high atomic number (e.g. iodine, barium), thereby absorbing a greater amount of x-Ry photons causing a more radiopaque image (increased attenuation)
define negative contrast
usually a low atomic number (e.g. H2O, air), thereby creating a radiolucent image, by not absorbing x-ray photons as much as surrounding tissues (lower attenuation)
define contrast pattern
each contrast media type (after administration) has a ‘normal’ appearance. Deviation from this helps in diagnosis of disease. Consequence: if you don’t mix the contrast well enough it may mimic a disease.
what are 3 types of contrast used and what examinations are they used for
Barium: GIT
Iodinated: vascular
Gastrografin: limited GIT studies for post-surgery
in a solution what is barium and when is it used
In Solution, barium is white crystalline substance that is in suspension in H2O It is odourless and opaque in appearance
- Extremely toxic in blood
- Barium is used in the GIT
- The osmolarity drops and makes it non-toxic for the GIT
how is barium excreted
The body uses large quantities of water available in the body to help excrete the barium
what happens if the patient doesn’t drink enough water after barium administration and what happens if they consume dehydrating substances
The barium comes out of suspension and sets inside the patients colon.
The consumption of dehydrating substances (e.g. alcohol or caffeine related drinks) can cause complications and hinder the body from eliminating the Barium. If the patient is dehydrated after the procedure, Barium can set and cause a Bowel obstruction.
what examinations use barium
Barium Enema
Small bowel Series
Barium swallow
Barium Meal
what is the preparation of barium in the upper GIT
generally fast for 12 hours before the time of examination. Keep hydrated (water/ clear fluids)
what is the preparation of barium in the lower GIT
Generally fast for 12 hours prior to the examination. Keep hydrated (water/ clear fluids).
Usually a cleansing preparation is used as well
list 5 adverse side effects of barium contrast media
Narrowing of the oesophagus (spasm): Shatzki’s Ring Dysphagia (difficulty swallowing) Spasm of GIT (usually localised) Hiatal hernia Aspiration pneumonia Granuloma formations (inflammation) Perforation Severe Cramping Diarrhoea Barium Impaction (constipation) Anaphylaxis: sweating/rash/tachycardia Bloating
What procedure is iodinated contrast media used for
vascular procedures
how is iodinated contrast eliminated from the body
kidneys filter the contrast through the blood
Drinking large amounts of water helps this process
list 5 mild adverse effects of iodinated contrast
Nausea Coughing fit and sneezing Vomiting Rash Headache Strange taste (most common) Hot flush feeling (most common) Localised swelling at site of injection (could be reaction or improper sited cannula) Red blotchy appearance - resulting from cannulising an artery or vein against it normal flow (retrograde)
list 1 moderate adverse effects of iodinated contrast
Palpitations/Tachycardia: rapid heart rate>100bpm
- Bradycardia: abnormally slow heart rate
- Wheezing/Asthma, Dyspnoea (difficulty breathing)
list 2 severe adverse effects of iodinated contrast
Convulsions
Life threatening cardiac arrhythmia
Cardiac arrest
Respiratory arrest
adverse effects of iodinated contrast
- Anaphylactic: systemic reaction in a susceptible individual upon exposure to a specific antigen. Non-Ionic substances are usually associated with Anaphylactic (Allergic) reactions
- Vasovagal Reaction: Sudden drop in blood pressure causing a momentary “blackout” or feeling very faint. This episode is transitory
what are the two main required blood tests needed when using contrast
creatinine creatinine clearance (eGFR)
what is creatinine and why is it important to measure when using contrast
Creatine is a molecule used in energy production in muscles and is the waste product of muscle metabolism
-Creatinine has been found to be a reliable indicator of kidney filtration function
how do we measure the eGFR
(140 - patient age) x (1 for men) (0.85 for women) / 72 x serum creatinine level (mg/DL)
what is a normal serum creatinine level for someone with 1 and 2 kidneys
Normal Serum Creatinine levels in blood are 0.5 to 1.5 mg/DL. A person with only one kidney may have a normal serum Creatinine level of 1.8 – 1.9 mg/DL.
what are the main things to consider when doing contrast studies for renal dialysis patients
The dialysis session should be straight after the radiology procedure
-If Dialysis is not due soon after the procedure, then filling the blood with iodine contrast media is often contraindicated as the blood will become toxic
what are the protocols surrounding breast feeding and contrast use
Current guidelines: It is safe to give contrast to breast feeding mothers
- Mothers are generally advised not to take iodine contrast. It secretes into the breast milk, and therefore the newborn ingests it
- Some research indicates that it is safe to breast feed, however, most radiology practices don’t (cautious)
what is gastrografin used for
Gastrografin is used for studying section of the GI tract. In particular post-surgical resection
Gastrografin is used to see if the surgical resection of the GI tract was successful and there are no leaks
Gastrografin is designed to provide a safe contrast media in the event there is a risk of extravasation (leakage out of contained area).
what is the post-surgical preparation of gastrografin
Nil by mouth
what is the preparation of gastrografin for patients who cannot tolerate barium
preparation is as for the barium study. However such a study will be limited in its scope due to the toxicity of vast quantities of contrast needed to image the whole bowel
what is osmolarity
the measure of solute concentration per unit VOLUME of solvent
what is osmolality
the measure of solute concentration per unit MASS of solvent
what does the number on the contrast bottle mean?
Tonicity
how does osmolarity relate to tonicity
- Solution (such as contrast) may be Iso-Osmolar (same concentration of blood) but varying tonicity
- The tonicity depends on the concentration of the cell plasma
what are the two ways we can use creatinine for
determining kidney function and an indicator of the amount of “particles” in the blood
what happens if the kidneys aren’t working properly? how does this affect contrast use?
Impurities are increasing in the blood: history of creatinine results are very useful
- Cells are struggling to keep up and begin to “Lyse” (rupture)
- Therefore we need to use a lower osmolarity for contrast so that we don’t add to the burden of the kidneys and increase the osmotic pressure (tonicity) on the blood which will destroy the blood cells by exacerbating the Lysing processes
what happens if we add contrast to the blood of the same concentration of the blood when the patient is in renal compromise/ failure?
We create a hypertonic solution in the blood and add to an already toxic situation
This can put the patient in renal failure from the over-burdened filtration needs of the blood on the kidneys
what is tonicity and what is it influenced by
The measure of osmotic pressure across a membrane.
Influenced by substances that cannot cross a membrane. However water can compensate for the difference in osmotic pressure.
