lec 4- contrast media 1

Question 1

outline the steps to preparing the patient for a contrast procedure

Answer 1

• Patient pre-admission preparation
• Admission pre-preparation procedures
• The procedure
• Immediate post procedural care
• Post discharge care

Question 2

why use contrast

Answer 2

• 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

Question 3

define contras medium/media

Answer 3

generic name given to substances that are administered to enhance the contrast of an x-ray via attenuation

Question 4

define positive contrast

Answer 4

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)

Question 5

define negative contrast

Answer 5

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)

Question 6

define contrast pattern

Answer 6

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.

Question 7

what are 3 types of contrast used and what examinations are they used for

Answer 7

Barium: GIT
Iodinated: vascular
Gastrografin: limited GIT studies for post-surgery

Question 8

in a solution what is barium and when is it used

Answer 8

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

Question 9

how is barium excreted

Answer 9

The body uses large quantities of water available in the body to help excrete the barium

Question 10

what happens if the patient doesn’t drink enough water after barium administration and what happens if they consume dehydrating substances

Answer 10

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.

Question 11

what examinations use barium

Answer 11

Barium Enema
Small bowel Series
Barium swallow
Barium Meal

Question 12

what is the preparation of barium in the upper GIT

Answer 12

generally fast for 12 hours before the time of examination. Keep hydrated (water/ clear fluids)

Question 13

what is the preparation of barium in the lower GIT

Answer 13

Generally fast for 12 hours prior to the examination. Keep hydrated (water/ clear fluids).

Usually a cleansing preparation is used as well

Question 14

list 5 adverse side effects of barium contrast media

Answer 14

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

Question 15

What procedure is iodinated contrast media used for

Answer 15

vascular procedures

Question 16

how is iodinated contrast eliminated from the body

Answer 16

kidneys filter the contrast through the blood

Drinking large amounts of water helps this process

Question 17

list 5 mild adverse effects of iodinated contrast

Answer 17

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)

Question 18

list 1 moderate adverse effects of iodinated contrast

Answer 18

Palpitations/Tachycardia: rapid heart rate>100bpm

• Bradycardia: abnormally slow heart rate
• Wheezing/Asthma, Dyspnoea (difficulty breathing)

Question 19

list 2 severe adverse effects of iodinated contrast

Answer 19

Convulsions
Life threatening cardiac arrhythmia
Cardiac arrest
Respiratory arrest

Question 20

adverse effects of iodinated contrast

Answer 20

• 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

Question 21

what are the two main required blood tests needed when using contrast

Answer 21

creatinine
creatinine clearance (eGFR)

Question 22

what is creatinine and why is it important to measure when using contrast

Answer 22

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

Question 23

how do we measure the eGFR

Answer 23

(140 - patient age) x (1 for men) (0.85 for women) / 72 x serum creatinine level (mg/DL)

Question 24

what is a normal serum creatinine level for someone with 1 and 2 kidneys

Answer 24

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.

Question 25

what are the main things to consider when doing contrast studies for renal dialysis patients

Answer 25

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

Question 26

what are the protocols surrounding breast feeding and contrast use

Answer 26

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)

Question 27

what is gastrografin used for

Answer 27

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).

Question 28

what is the post-surgical preparation of gastrografin

Answer 28

Nil by mouth

Question 29

what is the preparation of gastrografin for patients who cannot tolerate barium

Answer 29

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

Question 30

what is osmolarity

Answer 30

the measure of solute concentration per unit VOLUME of solvent

Question 31

what is osmolality

Answer 31

the measure of solute concentration per unit MASS of solvent

Question 32

what does the number on the contrast bottle mean?

Answer 32

Tonicity

Question 33

how does osmolarity relate to tonicity

Answer 33

- 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

Question 34

what are the two ways we can use creatinine for

Answer 34

determining kidney function and an indicator of the amount of “particles” in the blood

Question 35

what happens if the kidneys aren't working properly? how does this affect contrast use?

Answer 35

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

Question 36

what happens if we add contrast to the blood of the same concentration of the blood when the patient is in renal compromise/ failure?

Answer 36

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

Question 37

what is tonicity and what is it influenced by

Answer 37

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.