Contrast Review And Medicines 8.2.24 Flashcards
Why we use contrast?
- Differentiate anatomy
- Differentiate pathology/ abnormalities
- may provide information on function
What is the Path of IV contrast?
- Peripheral vein
- Deep vein
- Right heart
- Pulmonary arterial tree
- Left heart
- Systemic arterial vessels
- Visceral enhancements
- Venous drainage
- Excretion and recirculation
What is Positive contrast?
How does it appear on images?
Bright on CT
- iodinated as very good at absorbing x-rays
- IV administration unless specific indications for oral contrast
What is Negative contrast?
How does it appear on images?
Dark on CT
- Gas eg in CT colonography
- water - sometimes referred to as neutral contrast
What are the differences between high and low Osmolality of contrast agents?
High osmolar - ionic - not used IV anymore
Low osmolar - non-ionic monomer
ISO-osmolar - Non-ionic dimer
What are some of the Risks of giving CT contrast?
= Extravasation - contrast leeks out of cannulated vein
= Allergic type reaction
- previous reaction
- usually quickly after administering
- mild, moderate or severe
= Acute kidney injury
- related to renal function
- eGFR requested prior to contrast
What are the methods of Timing Contrast delivery?
- Timing bolus
- Fluoroscopic timing (bolus tracking)
- fixed timings
- Aterial
-portal venous
- delayed phases
What does MRI contrast contain?
Gadolinium based
- Gadolinium is toxic and can’t be excreted so is bound to other molecules
- linear or macrocyclic chelating agent
How does MRI contrast Work?
= shortening the T1 decay - increases the image brightness in T1W imaging
= shortens T2 - reduces T2 signal, therefore not used in T2w imaging
= too much contrast - T2 properties overwhelm T1 properties and signal is lost
How do we Time the administration of MR contrast?
What are some of the phases they are looking for within organs?
Angiography - blood pool perfusion of the vessel of interest
~Test bonus
~ Bolus tracking
~Time resolved MRA
First-pass organ, perfusion
Early post contrast
Delayed imaging options, e.g. Urography, liver, cardiac
What does PGD stand for and what is it?
Patient group directive -a legal framework, some registered health professionals to supply or administer specific medicines to predefined group of patients without having to see a prescriber.
What are the common Routes of administration?
Oral
IV - syringe or pump
IM
What is Analgesia?
Where does it affect?
Pain relief
No sedated
It can be local or systemic
Systemic = whole body
Local = just a small site
What can Sedation be?
Variable levels
Anxiolytic to general anaesthetic
Anxiolytic is a drug to reduce anxiety
What is the most common Local anaesthetic?
What are they used for?
How are they administered?
Lidocaine - most common
- usually by injection into the skin surface deeper structures
- Often used for biopsy sites
- Interventional line access
- Dental anaesthesia
Can cause be used to treat certain cardiac arrhythmias, so it’s not injected into vessel in this context.
Can be combined with adrenaline or epi to prolong action via vasoconstriction
Would be administered directly by the individual performing the procedure
Many other types of method of administering local anaesthetic, e.g. nerve, blocks, regional blocks topical
What are examples of Systemic analgesia?
Opioids - fentanyl - rapid action, short half life and few side effects
Non-opioids
- NSAIDS
- Paracetamol
- Entonox
What are common Sedatives?
How are they administered?
Benzodiazepines - anxiolytic and amnesiac properties
Most common = midazolam in hospital setting and for uncomfortable procedures
Many oral prescribed options, e.g. diazepam temazepam when only light sedation is required. Occasionally used for anxiety, e.g. MRI claustrophobia
Administered by sedation/medical teams, not responsibility of radiographers
What are the common Anaesthetic drugs?
Who administers them?
Propofol - GA - Infusion and used only by anaesthetic teams
Ketamine - Lots of side effects - only given by dedicated teams
What are the Bowel prep medications?
What effect do they have on the colon?
What effect dot hey have on the images?
Sodium Picosulphate
- picolax
- citrafleet
- citramag
Laxative increases motility of the colon
Ensure clear: of faecal residue prior to colonic investigations, e.g. CT colonography , contrast, enema, or conventional colonography
Positive or contrast is something sometimes used in CT colon to tag vehicle matter, allowing it to be digitally subtracted .
What is Busscopan?
Buscopan - antimuscarinic
Used as an antispasmodic in bowel imaging
US uses glucagon
What are the Side effects of Buscopan?
Blurred vision so wait before driving
Constipation
Dry mouth
Palpitations / increased HR
Urinary retention
How long should pt wait after scan?
30 min
What is Glucagon?
-Has been used as an anti-peristaltic in gi studies
-More in the USA
-Hyperglycaemic action
-Not as effective as Buscopan
-Not as well tollerated as Buscopan
-More expensive than Buscopan
What is Mannitol used for?
What are the effects of mannitol?
Used in all contrast, agent for small, bowel imaging MRI and CT
Distends , the small bow, allowing visualisation of the wall, more effective than water
Similar imaging appearances to water. Neutral contrast agent in CT
Hyperosmolar - draws water into the bowel lumen
Diarrhoea
Bowel Spasms
Flatulence
Many uses in medicine
What are Beta blockers used for?
What do the affect?
What are the common beta blockers?
What are the contraindications?
What should we do during administration?
Used in cardiac CT examinations to improve image quality
Reduces heart rate ( negative chronological effect)
Reduces heart contractibility (negative inotropic effect)
Affects the beta receptors
- beta 1 = heart
- beta 2 = airways and arteries
Usually metoprolol
- cardio-selective (beta 1) is after in asthma
- short half life is injection
Avoid/caution in asthma, severe aortic, stenosis, certain Brady arrhythmias, and acute heart failure
ECG monitoring during IV administration .
What is Adenosine used for?
Used in myocardial stress, perfusion images (MRI and NM)
Given as weight-based infusion (not bonus) with ECG monitoring
Very short, half-life life
Acts as a vasodilator
Diseased coronary artery cannot dilate differential perfusion can be seen within the Myocardium
Uncomfortable symptoms during infusion
Contraindicated in asthma
Blocked by caffeine - abstain prior to study
Regadenoson - adenosine analogue (used more in NM)
- Given fixed Dose
- Fewer side-effects
- Reversible with amitriptyline
What is Dobutamine?
What are the effects of dobutamine?
Why do we use it?
-Used in Cardiac imaging (CMR, NM, echo)
- Beta one agonist
- Positive inotropic effect ( increase in contractibility )
-Used as an alternative to a vasodilator agent or exercise
-Increases blood perfusion requirements so can evaluate ischaemia perfusion imaging
-Can evaluate wall motion - ischaemic myocardium cannot function as well so creates a wall motion abnormality
What are Diuretics used for?
What is a common diuretic?
- Flurosomine - drug of choice
- Increases urine production
-Improves urinary excretion of contrast to visualise renal tract - Used in MRI and CT urography which have largely superseded intravenous urography (IVU)
- Also, used in NM
- Can accentuate appearance of renal tract obstruction
What are some of the Emergency drugs?
~ adrenaline - 1 in 1000 for IM Anaphylaxis - IV 1 in 10 000 for Cardiac arrest
~ amiodarone - anti-arrhythmic
~ Atropine - increases HR
~ salbutamol - opens airways - blue inhalers
~ Amiophylline - counteracts adenosine - opens airways
~ Flumazenil
~ naloxone - reverses narcotic overdoses
~ steroids
~ anti-histamines
