IV Procedures And Contrast Flashcards
Contrast agent may help with ?
- Improve the sensitivity and specificity of the clinical diagnosis.
- Differentiate anatomical structures on the images
- Help to define abnormalities on the images.
Any tissue that is perfused, or penetrated, by contrast agent becomes?
More dense
Has an increased ability to attenuate x-ray photons
Correlates with a higher CT number
Will appear brighter on the image
Contrast media that is administered by IV, the tissues that are perfused by the substance include:
Blood vessels
Vascular lesions
Abdominal organs
How to opacity the distal GI tract
Oral agents administered rectally
For a virtual colonoscopy study, what is administered rectally?
Air or CO2
It is ____ in the contrast compounds that is responsible for the increased ability to attenuate x-ray photons.
Iodine
Osmolality is the
Concentration of molecular particles in solution
LOCM has what range of osmolality
500 to 850 mOsm/kg
HOCM has what range of osmolality
1,300 to 1,600 mOsm/kg
Blood has what osmolality
285 mOsm/kg
In general IV contrast agents are ____ (hyper or hypo-osmolar) solutions, or _____ (hyper- or hypo-tonic), compared to blood plasma.
Hyperosmolar
Hypertonic
Hypertonic solutions will cause
A net movement of water from within the tissues, into the vascular space.
This can cause dehydration.
Why is it important to ensure the patient is well hydrated before and after the exam?
Because the contrast media is hypertonic
Viscocity
A measure of the thickness of a liquid, related to the frictional forces of the molecules of the substance as they flow past each other.
A contrast agent will have a high viscocity if it’s…..
Molecular particles are large
What is the significance of contrast with high viscocity ?
- A patient’s tolerance of the force of the injection
2. The kidneys have more difficulty clearing larger molecules from the blood.
Name 11 minor reactions that do not require treatment
Nausea, vomiting, chills, warmth, sweating, minor hives, metallic taste, itching, shaking, headaches, dizziness
Moderate reactions, that may require treatment and close observation, but typically not hospitalization 6
- Moderate hives
- Facial edema
- Change in pulse rate
- Hypo- or hypertension
- Wheezing
- Bronchospasm or laryngospasm
Some scientists group the mechanisms that cause contrast reactions, into 2 categories called:
Chemotoxic
Idiosyncratic
Chemotoxic reaction mechanisms are those that can be directly attributed to factors including:
- Physiological properties
- Total volume injected
- Rate of injection
Osmosis
Is the process in which the contrast particle draw water toward them and away from body tissue or cells
The rapid movement of fluid through osmosis. Into the blood vessels is believed to be contributed to?
- Pain associated with vessel dilation
- Flushing
- Changes to red blood cells
- Vascular endothelium damage
- Vomiting
- Nausea
- Dehydration
How can you reduce the viscosity of contrast?
Warming it
A high concentration of iodine in the contrast agent leads to
- Higher osmolality
2. Higher viscosity
Idiosyncratic reaction mechanisms can be caused by
Anything other than the properties of he contrast agent, the amount injected, or the injection rate.
Adverse reactions that are allergic in nature, means?
The patient’s physiology has trouble tolerating the introduction of a foreign substance. Their body will release histamine
Histamine acts by
- Constricting smooth muscles and venules
- Accelerating heart rate
- Lowering blood pressure
- Increasing gastric and mucous secretions
What happens when an excessive amount of histamine is released in he body?
- The vascular system becomes overloaded and histamine passes into th surrounding tissues.
- Believed to be responsible for reactions such as hypotension and hives
In order to prevent histamine reactions, you can
Pre-medicate with anti-histamine or steroids.
A precaution is?
A condition that would warrant a medical decision as to whether the benefits of the exam outweigh the risks posed to the patient.
A contraindication is
A condition that would preclude a patient from having a study performed in a given manner.
Contraindication to contrast includes
A known hypersensitivity to the compounds (medical history)
Extra caution should be taken with patients with the following precautions
- Liver or kidney disease
- Thyrotoxicosis
3.myelomatosis - Diabetes
- Anuria
- Multiple myeloma
- Sickle cell disease
- Pheochromocytoma
- Hyperthyroidism
10 asthma - Hay fever
- Food allergies
- Congestive heart disease
In normal patients, how long dose it take for 50% of the injected dose is recovered in the urine?
2 hours
In patients with severe renal impairment, how long dose it take for 50% of the injected dose is recovered in the urine?
16 to 84 hours.
Generally patients taking metformin, should not take it after IV contrast, because ?
To prevent lactic acidosis
Metformin should be resumed only after?
Kidney function has been reassessed and determined to be normal.
Patients that take metformin and have renal dysfunction should?
Not take metformin and follow-up renal function tests should be performed until metformin can be taken safely.
Advantages of power-injectors
- Consistent, reproducible flow rate.
- Precise volume and dose control.
- Optimum contrast enhancement is achieved with higher injection rates
- Rates allowed up to 5 or6 ml/sec
What type of needle is not used with a power injector?
Butterfly needle
And
Standard PICC lines (peripherally inserted central catheter)
Specially-labeled Power Piccs may be used with a power injector up to what rate?
5ml/sec
Routine exams use what injection rates
2 to 4 ml/sec
CTA exams use what injection rates
4 to 5 ml/sec
Injection rates are determined by
- Type of scan
- Volume of media
- IV gauge/pressure capacity
- Condition of patient
Why is the cephalic vein less desirable to use for IV contrast?
- It’s tortuous route makes it more likely to be impeded when the arm is raised
Why is the basilic vein more desirable to use for IV contrast?
- It has a more direct route to the axillary vein
2. Because of the anastomosis between the basilic and cephalic veins, the basilic vein remains more stationary.
How to distend the vein
Apply tourniquet
Patient pump hand
Slap vein
Apply heat
Slapping the vein briskly will
Double its size, due to reflex vasodilation
Using a saline flush, with a dal-head power injector, increases ____ and decreases ____
Increases the contrast boils and can decrease both contrast usage and radiation dose to the patient.
What venipuncture and contrast administration details should be recorded in the patient records?
The injection site Number of venipuncture attempts Gauge of the catheter Amount of contrast Concentration of contrast Rate of contrast injection
If ______ of contrast media is injected into soft tissue, surgical consult is recommended
Over 100 ml
Venous air emboli appear, how on images?
As dark bubbles o air in the most anterior aspects of contrast filled vessels and heart chambers.
Signs and symptoms of larger air emboli include
SOB Chest pain Hypotension Paralysis Seizures
Small to medium air emboli usually
Don’t need treatment
Close observation
Documentation of occurrence
Larger air emboli require
Placing patient in the left lateral decubitus position.
Head angled down 30 to 40 degrees.
100% oxygen administered
What does the required treatment, for larger air emboli do?
Allows air bubbles to rise to the apex of the right ventricle and prevents them from entering the pulmonary vascular system.
If the scan is started too late?
The organs and lesions will both enhance.
The 3 phases of tissue enhancement
- Bolus phase
- Non-equilibrium phase
- Equilibrium phase
The amount of time that each phase take is directly related to?
The injection rate
The volume of injection
The velocity of the blood flow
What happens following the injection?
The contrast bolus:
1. Travels through the veins, to the right side of heart.
- Passes through lungs
- Into the left side of heart
- Into the arterial system, starting with the aorta.
- Ultimately returns to the heart, via the veins. At this point the contrast bolus is moderately dispersed.
The bolus phase of enhancement begins
Just after the contrast is injected.
The bolus phase is defined by
A significant density difference between the abdominal aorta and the inferior vena cava.
During the bolus phase, the bolus moves
Through the arteries and away from the heart. It is at this time that CTA images are optimal in quality.
The non-equilibrium phase is characterized by
A 10-30 HU density difference between the abdominal aorta and the inferior vena cava.
During the non-equilibrium phase, the bolus starts to
Disperse into the capillaries, then into the veins.
As a result, the density difference between the abdominal aorta and the IVC decreases.
It is typically during the non-equilibrium phase that we obtain the best
Differentiation of structures in the soft tissues.
The equilibrium phase is characterized by
A density difference of less than 10 HU between the abdominal aorta and the IVC.
During the equilibrium phases, the contrast agent’s concentration in the veins
Becomes similar to the concentration in the arteries.
During the equilibrium phase, soft tissue structures’ differentiation
Becomes diminished .
The liver is the only organ with a dual blood supply
80% from the portal vein
20% from the hepatic artery
When the contrast perfuses the liver, the enhancement occurs from
Each of the 2 sources at different times.
The hepatic arterial phase occurs around
20 to 40 seconds are the start of injection.
The portal venous phase occurs approximately
60 to 90 seconds after the start of the injection
Most tumors in the liver are ___ vascular than the liver and will most obvious during?
Less vascular
Portal venous phase
A smaller set of hepatic tumors are more vascular than the liver, and can be seen when?
During the hepatic arterial phase.
CTA examinations require precise timing to ensure
That the contrast media passes though the desired vessels during the exact time that the scan is done.
Brain scan for what diseases, require delayed scans?
MS
Metastatic lesions
AIDS-related abnormalities
Abdomen scan for what diseases, require delayed scans?
Cholangiosarcoma
Fibrolamellar carcinoma
Adrenal tumors
Pelvic scan for what diseases, require delayed scans?
Cancer of the probate, ovaries, or uterus
Why do you need to factor in a delay after the start of injection, prior to using a helical scan?
If a helical scan was started immediately after the injection, many of the images would be acquired during the bolus phase.
With a delay, the helical scan can be completed during the non-equilibrium phase.
Why do you need to factor in a delay after the start of injection, for Multi-row detector scanners, versus a single-row detector scanner?
This is so the scan does not finish before the contras media has passed through the tissue of interest.
If a patient what 2 conditions,using the standard delay times would not work.
Poor cardiac output
Or
Patient is in shock
How is a test bolus used?
A test bolus is given before the actual scan is done.
With this morbid, several slices are collected at the same slice position over a short period of time to monitor the arrival of the contrast.
On all of the images a ROI is drawn over the enhancing vessel.
Scanner software can then calculate he arrival time of the contrast.
After the test is completed, the actual injection and scan are performed, using the delay time that was determined.
Many scanners are equipped with _____ that senses how long it takes for a boys of contrast to reach the region of interest
Automated software
The pacification caused by oral contrast is needed in order to
- Reduce the risk of misdiagnosing fluid-filled bowel, as an abscess or tumor.
- Helps to visualize if a lesion is exterior to the bowel or if it is infiltrating the bowel.
2 categories of oral contrast media
- Barium sulfate
2. Iodinated
In an effort to visualize the gastric wall thickness and detect gastric tumors, some physicians elect to
- Distend the stomach with air or gas.
In such cases, glucagon can be given to inhibit gastric peristalsis.
- After consuming oral contrast, a pt swallows a final dose of water. This keeps he gastric contents from being opacified.
In cases of genera abdominal pain, ____ may be used as an oral contrast agent.
Water
Since the barium solution’s high density causes sever streak artifacts in CT, what is used?
Barium sulfate solutions containing a 1 to 3% barium suspension
Characteristics of barium sulfate
Inert
Insoluble substance
Passes through GI unchanged
The most frequent adverse reactions to BaSO4 is
Diarrhea
Abdominal cramping
Rare adverse reactions to BaSO4 are
Colon impact ion Barium granuloma Barium appendicitis Intestinal perforation Peritonitis
Allergic reactions to barium sulfate are more likely in patients
Who are atopic and those with previous history of allergic symptoms.
Atopic
denoting a form of allergy in which a hypersensitivity reaction such as dermatitis or asthma may occur in a part of the body not in contact with the allergen.
Contraindications to using barium sulfate solutions include
- Colon obstruction or perforation
- Tracheosophageal fistula
- Obstructing lesions of the small intestine
- Pyloric stenosis
- Hypersensitive to barium sulfate
For an abdominal study most patient drink ___ of barium sulfate ____ prior to exam
750ml
1 hour
For an abdominal and pelvic study most patient drink ___ of barium sulfate ____ prior to exam
1,500 ml
2 hours
How to prepare the patient that is getting barium via rectum
1 warmed to body temperature
2. Patient should be rolled 360 degrees, to coat al surfaces
To evaluate Crohn’s disease and for CT enterography
There is a very low concentration of barium sulfate
2,000ml consumed 90 minutes prior to exam
Concentration of iodinated oral contrast is
6 to 9 mg of iodine per ml
Iodinated oral contrast agents are used when
Barium sulfate agents are contraindicated
Iodinated agents are absorbed by the GI tract, by what percent?
0.1 to 0.5% absorption occurs
Disadvantage of iodinated oral agents
Significant dilution of the agent occurs due to the movement of water into the bowel.
Opacification of the distal bowel may be difficult.
Water soluble iodinated contrast pass through the GI tract in ____ hours.
2
Having the patient NPO for _____ prior to the exam will help to improve opacification in the distal bowel.
Minimum of 4 hours.
Contraindications to iodinated oral contrast is similar to the IV, except for
If there is a risk of aspiration. Do not use
Aspiration of iodinated agents can result in
Severe pulmonary edema
Common reactions to iodinated oral agents are similar to those of barium sulfate agents:
Mild diarrhea
Abdominal pain
Flatulence
Procedures for Post-Myelographic CT
- Elevate head: reduces risk of headache and seizures.
- Confirm density of contrast media: if scan is more than 4 hours after injection, the density will be reduced too much.
- Ensure that the contrast has not separated from the CSF: Either roll the patient before the scan of by scanning the patient in a prone position.
