Transcript patient care - Nuclear Medicine Review

PATIENT CARE
IN COMPUTED TOMOGRAPHY
Frank Cairo R.T. ( R ) ( CT ) ( MR )
DESCRIPTION
• THE FOLLOWING TOPICS WILL INFORM THE
TECHNOLOGIST ON THE IMPORTANCE OF
PATIENT CARE AND PATIENT SAFETY
OBJECTIVES
• To understand the three steps of an
examination. To understand the type of
consents and how they play a role in handling
patients. Types of infections. Contrast
administration, types, and risks.
Examination Initiation
• CT examinations must be initiated by a clinician with
appropriate credentials
– Before the examination begins the technologist must
review the clinician’s order and read all clinical data
provided. Any discrepancies between the written order,
the examination scheduled, or the examination the patient
thinks was ordered must be reconciled
THREE PARTS OF THE C.T. EXAM
• PRE EXAMINATION
• EXAMINATION
• POST EXAMINATION
PRE EXAMINATION
• PATIENT IDENTIFICATION
▫ Id all patients x2
▫ Check patient’s chart , script , and bracelet
▫ Talk to patient to see if they are aware and can consent to
the examination.
▫ Make sure the ID of the patient matches the script for the
examination
▫ Ask out patients first and last name, and date of birth
▫ Check patients skin for rashes
PRE EXAMINATION
• PATIENT SCREENING
▫ Screening form is used for patient history and safety
▫ Check form for the following conditions
 ALLERGIES, ASTHMA, DIABETIES, KIDNEY DISEASE, MULTIPLE
MYELOMA,CARDIAC HISTORY
▫ If scanning an inpatient check chart for conditions and lab
work
▫ Ask if a patient is PREGNANT
▫ Check lab work for blood values
▫ Ask about prior reaction to contrast
▫ Explain to patients the risks of contrast and answer any
questions they have
Diagnostic Information
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Many disease or conditions have similar findings on CT
images. A medical history can often aid in narrowing down,
or pinpointing exactly, the disease or condition from which
the patient suffers
Questions include
– Past surgeries
– Significant medical issues
– Current symptoms
PATIENT CONSENT
• THE THREE TYPES OF CONSENT
▫ Simple Consent – patient gives consent written or oral
▫ Implied Consent – when the patient is unable to give consent
due to their condition and a family member is not available (
emergency situations )
▫ Informed Consent – it is a written consent that the patient or
another legal person understands the procedure and all of its
possible outcomes. In establishments the radiologist, nurse , or
P.A. obtains this form. The technologist must recheck this form
before the exam
Benefits of Effective Communication
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Improved patient safety
Improved patient retention
Increased referral
Improved patient compliance
Greater profitability
Reduced risk of malpractice suits
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Improved examination quality
Better staff morale
Reduced staff turnover
Improved collections
Greater efficiency
Increased personal and
professional fulfillment of
radiology staff
The Communication Process
• The process of creating meaning
– You cannot really transmit meaning—only messages
– Meaning is interpreted by the person receiving the
message
– Many times the sender thinks the message is clear, but the
receiver hears something entirely different
• Estimates suggest that 40% to 60% of a message’s meaning is
lost in transmission
Barriers to Communication
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Language
Power struggles
Misreading of body language
Fuzzy transmission
Receiver distortion
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Assumptions
Preconceptions
Past experiences
Cultural differences
Nonverbal Communication
• Visual communication (body language)
– Eye contact
– Posture
• Tactile
– Use of touch to impart meaning
• Vocal
– Intonation of a person’s voice
Nonverbal Communication (cont’d)
• Time
• Space
– Intimate, personal, social, or public distance
– Variations in accepted norms owing to ethnicity,
age, and gender differences
• Objects
The Speaker’s Responsibilities
• Be audible
• Be aware that your listener may not have
understood you
• Be willing to ask questions of your listener to
see whether he or she understands you
The Listener’s Responsibilities
• Let the speaker know if he or she is inaudible
• Let the speaker know that you are attentive
• If the speaker’s message is unclear, let him or
her know that you need a point clarified (but
be tactful)
EXAMINATION PHASE
• Patient is explained the instructions he or she
need to follow during the exam
• Explain breath-hold
• Tell how the contrast will feel during the exam
• Let patient know that the table will move
during the exam
• Tell patient how long exam will take
• Reassure the patient that they are being
monitored at all times
POST EXAMINATION PHASE
• Explain to patient if there are any post exam
instructions to follow
• Take I.V. out and bandage patient
• Dismiss patient in a friendly and professional
manner
• Check patients for hives or skin rashes
INFECTION TRANSMISSION
• TYPE OF BACTERIUM, VIRUS OR PARASITE
• A HOST
• AN EXIT FROM THE HOST
• MEANS OF TRANSMISSION FROM THE HOST
• ENTRY TO THE NEW HOST
INFECTION TYPES
• Infections invade the body in steps or phases
▫ Incubation phase – pathogen lies dormant, then
symptoms start
▫ Prodromal phase – specific symptoms, host is highly
infectious
▫ Full disease stage – full blown and infectious
▫ Convalescent stage – lessening symptoms and recovery
INFECTION CONTROL
▫ Surgical Asepsis – before, during, and after a
procedure. Examples are biopsies, drainages,
catheterization, and NG tubes. Also removal of all
germs from equipment
▫ Medical Asepsis – working under sterile conditions
• Universal precautions are always followed. Hand
washing, gowns and masks may be used
• Betadine always better than alcohol
SURGICAL ASEPSIS
• Complete removal of all organisms from the equipment and
environment.
• Boiling item(s) for 12 minutes
• Dry heat for 1-6 hours at temperatures of 300+F
• Gases are used for electrical, plastic and rubber items (Freon
& Ethylene)
• Steam
• Chemicals
• Ionizing radiation (commercial)
• Non-ionizing radiation (microwaves and low-pressure steam)
INFECTION CONTROL
• Sterile Technique
– Sterile trays should be opened so that the first flap opens away from
surgeon.
– Sterile solutions should be opened without touching the inside of the lid
or opening of the container.
– Sterile gowns are not sterile in the back
– Sterile gloves must be kept above the waist.
– Masks must fit snug over the mouth and nose.
– When in the operating room or any sterile environment, always pass back
to back.
– Any sterile item touched by a non sterile person is no longer sterile and
must me either disposed or sent back to central supply for sterilization.
•
MEDICAL ASEPSIS
• Medical Asepsis
• Reducing the probability of infectious organisms being
transmitted to a susceptible individual by reducing the total
number of organisms (3 levels)
– Cleanliness: hand washing (minimally 15 seconds)
– Disinfection: destruction of pathogens by using chemical
materials
– Sterilization or surgical asepsis: treating objects with heat, gas or
chemicals to make them free of germs
NOSOCOMIAL INFECTIONS
• The most common in the hospital or clinic
surroundings
• Infections contracted in acute care
• They are increased by several factors
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Contaminated environment
Therapeutic regimen ( chemo )
Contaminated equipment
Contamination during a procedure
• About 10% of patients contract this type of
infection
MRSA
• MRSA is a resistant variation of the common bacterium
Staphylococcus aureus. It has evolved an ability to survive
treatment with beta-lactam antibiotics, including penicillin,
methicillin, and cephalosporins. MRSA is especially
troublesome in hospital-associated (nosocomial) infections. In
hospitals, patients with open wounds, invasive devices, and
weakened immune systems are at greater risk for infection
than the general public. Hospital staff who do not follow
proper sanitary procedures may transfer bacteria from patient
to patient.
UNIVERSAL PRECAUTIONS
• Universal precautions refers to the practice, in medicine, of
avoiding contact with patients' bodily fluids, by means of the
wearing of nonporous articles such as medical gloves, goggles,
and face shields. Medical instruments, especially scalpels and
hypodermic needles should be handled carefully and disposed
of properly in a sharps container. Pathogens fall into two
broad categories, bloodborne (carried in the body fluids) and
airborne. Standard universal precautions cover both types.
UNIVERSAL PRECAUTIONS
• Universal precautions should be practiced in any environment where
workers are exposed to bodily fluids, such as:
• Blood
• Semen
• Vaginal secretions
• Synovial fluid
• Amniotic fluid
• Cerebrospinal fluid
• Pleural fluid
• Peritoneal fluid
• Pericardial fluid
Injection Techniques
• Method of injecting iodinated CM will vary
according to
– Vascular access available
– Type of examination
– Specific clinical indication
Injection Parameters
• Parameters that may vary
– Whether the injection is performed by hand or
with the use of a mechanical injector
– Contrast volume
– Flow rate at which the contrast will be injected
– The delay between injection and scanning
– Whether a saline flush is used
Vascular Access
• Stable IV access is necessary for CM
administration
• Vascular access may consist of
– Standard indwelling peripheral catheter
– Central venous access devices (CVAD)
• Peripherally inserted central catheters
(PICC)
• Non-tunneled central venous catheters
• Tunneled central venous catheters
Starting a Peripheral IV
• Obtain basic consent
• Use aseptic technique
• Use an indwelling catheter set with a flexible plastic
cannula whenever a mechanical injector will be used
• Steps involved
– Assemble supplies
– Choose site
– Place the needle
– Secure site
Using an Established Indwelling Venous
Catheter
• Evaluate the site for appropriateness for CM injection
• Verify the patency of the line with a saline flush
• If other medications are running, hang an additional
bag of saline and connect it to an open port on the IV
tubing
• Turn off existing medication only long enough to
complete the injection
• Once the injection is completed, flush the line with
saline and restart medications at the identical
preexamination rate
Using a CVAD
• A CVAD is a venous catheter designed to
deliver medications and fluids directly into
the superior vena cava, inferior vena cava, or
right atrium
• There are several different kinds of CVADs
• Although CVADs are not optimal for contrast
administration, in some cases they are the
only option available
Peripherally Inserted Central Catheters
• A PICC is a long catheter that is inserted through
the large veins of the upper arm and advanced so
that its tip is located in the lower one third of the
SVC
• Many PICC lines cannot tolerate the pressure
required to inject CM at the high injection rates
typical of CT examinations that use mechanical
injectors
• In these cases it is recommended that a separate
IV be inserted for CM administration
Peripherally Inserted Central Catheters
(cont’d)
• When no other options exist and the PICC
must be used for CM injection the
– injection rate must be slowed
– injection should be performed by hand
bolus rather than by mechanical injector
• Specially designed PICCs (e.g., PowerPICC) can
be used for CM injections with rates up to
milliliters per second
– Produced in colors that make the readily
distinguishable from the traditional PICC
lines
Non-Tunneled and Tunneled CVCs
• Whenever possible, avoid using these CVCs by
starting a standard peripheral IV line
• When they are used for CM administration
follow your institution policy
• Never use a dialysis CVC for CM injection
BARD PURPLE POWER PICC
EXTRAVASATION
• Contrast under the skin is called infiltration
• Most facilities have a nurse monitoring the
injection part of the way
• Stop injection if patient infiltrates
• Apply pressure to area
• Elevate arm
• Apply cold pack
• Radiologist must check patient
• Document event
IV ADMINISTRATION
• Parenteral ( any other than by mouth )
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Subcutaneous
45 degree angle
Intradermal
15 degree angle
Intramuscular 90 degree angle
Intravenous
various angles to vein
• Needles have three parts
▫ Hub for connection
▫ Shaft or cannula in angiocaths
▫ Bevel
• All have a gauge, large # = small hole
OTHER METHODS OF
ADMINISTRATION
• Oral – by mouth
▫ Diluted barium
▫ diatrizoate meglumine ( water soluble iodinated )
• Rectal – air or barium
• Intrathecal – in subarachnoid space
▫ Keep head up
▫ Roll body to move contrast
ORAL CONTRAST
• It is also a positive contrast
• Displaces air and fluid in the bowel
• Radiologist can differentiate between a fluid filled bowel and
a abscess
• Can either be barium or iodinated
• 1000ml used for most studies over time
ORAL IN PEDIATRIC CASES
• Oral contrast is determined by age as of the
amount needed per patient:
– 0-6 months 40-60cc
– 6-18 months 120-160cc
– 3 years-12years 240-360cc
– 12 years and above 480cc +
CT BARIUM
Volumen
VOLUMEN INDICATIONS
• VoLumen’s low density (~15-30 HU) Permits bowel wall
visualization
• Helps delineate between intra-lumen, and soft tissue of
the bowel wall
• Can be used in conjunction with IV contrast
• Does not cause artifacts and streaking during volumetric
imaging
• Does not mask pathology
• Does not obscure vasculature and surrounding organs
• Used for Crohns , pancreatic cancer, and abd CTA
VOLUMEN
• Low HU oral barium sulfate suspension (VoLumen)
resembles water on CT images
– Just 0.1% barium sulfate solution
– Measures from 15 to 30 HU on an image
• Advantages of low HU oral contrast
– Improved bowel distention (compared with water)
– Faster transit than standard CT barium solutions
– More effective visualization of both the bowel wall
and the mucosa
BARIUM SULFATE
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Taken orally or can be used rectally
Not absorbed by the body
Less reactions
Better opacity in the distal bowel
Slow transit time
Most patients have to drink 900 – 1200 ml
For a abd/pel exam patients must start drinking 2 hours
before or the night before for distal bowel opacification
• Contraindicated for patients with perforation, fistula, or
obstruction
IODINATED ORAL CONTRAST
IODINATED ORAL CONTRAST
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Taken orally or can be used rectally
Fast transit time
Can thin out in the distal bowel
Can be mixed in any liquid
Mix about 20-30ml /1000ml( 32 oz ) of liquid
See the manufactures instructions
AIR AND INTRA-ARTICULAR
• Air is a negative contrast
• Can be used rectally or with fizzes orally
• It looks black
• Intra- Articular needle is placed under
fluoroscopy
TYPES OF IODINATED IV CONTRAST
• Iodinated contrast have properties of
– Osmolality
– Viscosity
• Types of IV contrast
– Ionic
– Non ionic
Both have a high atomic number so they
absorb radiation
• I.V. contrast is also described as positive
contrast
Water
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Sometimes used in place of a positive agent
It does not obscure mucosal surface
Transits rapidly
Distends the bowel poorly
TYPES OF IODINATED IV CONTRAST
• Iodinated contrast have properties of
– Osmolality
– Viscosity
• Types of IV contrast
– Ionic
– Non ionic
Both have a high atomic number so they
absorb radiation
• I.V. contrast is also described as positive
contrast
OSMOLALITY
• The number of particles of the contrast per kilogram of
solvent or water
• Contrast with lower concentration have lower osmolality
• Low osmolality yields less heat and pain at the point of
entry
OSMOLALITY
• Blood plasma has a 285mOsm/kg
• High osmolality contrast has about 4 to 8 times the osmolality
than blood ( 1200 mOsm/kg )
• Low osmolality contrast has 2 to 3 times the osmolality than
blood 900 mOsm/hg
• Because of blood having less osmolality than contrast we
describe contrast as hypertonic
• Hypertonic causes a movement of water into the vascular
space
OSMOLALITY
TYPES OF CONTRAST
– High Osmolality (Higher risk of complications)
• Diatrizoate sodium (Hypaque)
• Iothalamate meglumine (Conray)
– Low Osmolality (Lower risk of complications)
• Ioxaglate meglumine (Hexabrix)
• Iopamidol (Isovue)
• Iopromide (Ultravist)
• Ioversol (Optiray)
ISOSMOLAR CONTRAST
• Iodixanol ( visipaque )
• sodium and calcium levels at the same level of
the blood
• Very few reactions with patients at risk of
reactions and renal failure
VISCOSITY
• Viscosity is a property of friction
• It is how thick a fluid is
• Can cause vasoconstriction
• Warming the solution helps lower the viscosity
• Warm to body temperature
IONIC CONTRAST
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The contrast breaks apart in water
Breaks into a anion and a cation
Anion is iodine and the cation is salt
Referred to as High Osmolality Contrast Media
Raises the osmolality of blood serum
Blood serum is isotonic
Due to the amount of particles in the blood, water is
drawn in to the blood
• Blood volume is raised
• Increases osmotic pressure
IONIC CONTRAST
• Due to higher osmotic pressure the patient can have
several hemodynamic effects
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Hypervolemia
Vessel dilation
Possible shock
Vasoconstrictors from the kidney can narrow the renal
arteries
• Hypervolemia cause the heart to work harder
to pump the increased volume of blood
NON IONIC CONTRAST
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Does not separate in water
Causes no change in the blood plasma
No hypervolemia
Also known as Low Osmolality Contrast Media
Are more water soluble
Less chance for allergic reaction
CONTRAST PROPERTIES
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Most have a half-life of 10 -90 min
Kidneys excrete
Can get into breast milk
Has a peak blood level in 2 min post injection
Peak urine amount is in aprox 2 hours
After 24 hours more than 90% is excreted
Fills kidneys in 1 minute
Maximum filling in 5 – 15 min post injection
Does not cross the blood brain barrier
Dialysis can remove contrast from the blood
DOSE
• Dose
– Determined by iodine concentration and the
volume delivered
– When comparing doses, compare the total grams
of iodine delivered
DOSE
• Pediatric dose
– Most often based on the weight of the infant or
child
– The most common formula is 2 mL/kg
• Adult dose
– Typically, a uniform dose for each protocol
– However, weight-based dosing for adults has
advantages
Adverse Effects
• Iodinated CM is one of the most widely used
of all medications
• They are also one of the safest
• Fatal reactions are extremely rare in both
HOCM and LOCM
– Estimated at 0.001%
Adverse Effects (cont’d)
• Although rare, adverse reactions sometimes
occur
• It is impossible to predict which patient will
have an adverse reaction to IV-administered
CM
• Therefore, CT staff must be trained to respond
quickly
Adverse Effects (cont’d)
• The term “contrast reaction” is used in a
variety of different ways in relation to the
effects of iodinated CM
• In some instances, it describes all undesired
effects including the many subjective effects
(e.g., heat, metallic taste)
• In other instances, it describes the less
common, more serious side effects that may
require treatment or even be life threatening
Adverse Effects (cont’d)
• CM reactions can be broadly categorized as
either
– Chemotoxic reactions
• Result from the physiochemical properties of the CM,
the dose, and speed of injection
– Idiosyncratic reactions
• All other reactions
• In practice, it can be difficult to characterize
some reactions into one group or the other
Idiosyncratic Reactions
• The mechanisms by which idiosyncratic
reactions occur are not precisely understood
• The origin of these reactions is rarely, if ever,
“an allergy”
– True allergic reactions result in the production of
antibodies, which are not found after CM
reactions
– True allergies result in similar or more severe
adverse reactions with reexposure
• Research shows this is not true of CM reactions
Idiosyncratic Reactions (cont’d)
• Even though the underlying cause is likely
different, symptoms of idiosyncratic reactions
resemble allergic (or anaphylactic) reactions
and are, therefore, often called allergic-like or
anaphylactoid reactions
• Even though it is not completely accurate, the
term “contrast allergy” remains in common
use
CONTRAST REACTIONS
• Reactions can present in several ways
– Mild
– Moderate
– Severe
• Most reactions happen within the first 30
minutes post injection. Some can start as little
as 5 minutes
MILD REACTIONS
• Last a short time
• Can include the following
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Mild urticaria
Itching
Shaking
Coughing
• Observe the patient, these symptoms should all
go away
• Nausea is not a sign of an allergic reaction
MODERATE REACTIONS
• Can include the following
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Tachycardia or Bradycardia
Severe urticaria
Dyspnea
Hypertension or Hypotension
Wheezing
Facial edema
• These types of reactions need medical attention
and the patient must be monitored and observed
for at least 30 minutes after exam
MODERATE REACTIONS
• A radiologist, nurse, or PA must be informed to
treat patient
• Diphenydramine give P.O. or I.M. epinephrine is
used for a severe reaction
• Facial swelling epinephrine is used
• If a Vagal reactions occurs we trendelenburg
patient and give I.V. fluids
• Atropine can be given also for vagal reaction
• For pheochromocytoma – phentolamine 5mg IV
• For wheezing give O2 and bronchiolar dilator
inhaler. Can also give epinephrine
SEVERE REACTIONS
• Also called anaphylactic shock
• Symptoms can be
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Apnea
Dyspena
Laryngeal edema
Convulsions
Arrhythmia
Cardiac Arrest
• If this type of reaction should occur a code should
be called, if in a outpatient facility call 911 and
inform radiologist immediately
CONTRAINDICATIONS TO CONTRAST
• Risk Factors for Contrast Reaction
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Older patient age >65
Renal insufficiency
History of contrast-related anaphylactoid reaction
Asthma
Comorbid conditions such as cardiovascular disease
Concurrent NEPHROTOIXIC drugs such as NSAIDS
Diabetes
Multiple myeloma
• CRAB - C = Calcium (elevated), R = Renal failure,
B = Bone lesions
hypercalcemia
A = Anemia,
• The Radiologist will make the final decision on IV
contrast for patients with contraindications
CONTRAINDICATIONS TO CONTRAST
• Patient must be NPO 4 –6 hours before exam
• Diabetics must stop metformin 24 hours
before exam
• Must have blood checked 48 hours post exam
to check serum creatinine and renal function
• Asthma
CONTRAINDICATIONS
• metformin,should be stopped for 48 hours
following the intravascular administration of
contrast media and that the use of metformin
not be resumed until renal function has been
shown to be normal. The reasoning is that if
the contrast medium causes kidney failure and
the person continues to take metformin
(which is normally excreted by the kidneys),
there may be a toxic accumulation of
metformin, increasing the risk of lactic
acidosis, a dangerous complication.
Metformin Therapy
• CM can result in CIN. When renal dysfunction
occurs in patients taking metformin, the drug
can accumulate and result in lactic acidosis
– Although the incidence of occurrence is low, when
it does occur lactic acidosis is fatal in about 50% of
patients
• As a precaution, metformin should be
temporarily discontinued after CM
administration; it can be resumed after 2 days,
assuming kidney function is normal
Definition of CIN
• Contrast-induced nephropathy (CIN) is an
acute impairment of renal function that
occurs after the intravascular administration
of contrast material (for which alternative
causes have been excluded)
• Presentation
– Progressive rise in SeCr within 24 hours of CM
administration
– Typically nonoliguric
CIN Risk Factors
• Creatinine clearance less than 30-25 mL/min
• History of diabetes mellitus
• History of recent administration of iodinated
contrast agent
• Anticipated large volume of CM
• History of congestive heart failure
Methods of Preventing CIN
• Identify patients at high risk
– Patients with diabetes mellitus or other risk
factors should have a recent SeCr
• Use LOCM or IOCM
• Ensure adequate patient hydration
• Minimize CM volume
• Allow at least 48 hours between procedures
requiring CM
• Discontinue other nephrotoxic medications before
the procedure
Dialysis and CM
• Do not give CM to dialysis patients in whom it
is hoped that the dialysis is temporary
• CM may be given to patients on dialysis with
end-stage renal failure
– Patients on dialysis who undergo contrastenhanced CT may continue their routine dialysis
schedule
CM Effect on Thyroid Function
• No effect on patients with normal thyroid
function
• Insignificant effect on patients with
hypothyroidism
• When given to patients with hyperthyroidism
CM may precipitate thyroid storm
– This is a severe, life-threatening condition
resulting when thyroid hormone reaches a
dangerously high level
Pulmonary Effects
• CM may cause
– Bronchospasm
– Pulmonary arterial hypertension
– Pulmonary edema
• Patients at increased risk are those with a history of
pulmonary hypertension, bronchial asthma, or heart
failure
• The use of LOCM significantly reduces the risk
CM Effects on the Central Nervous
System
• The intravascular administration of CM has been
shown to provoke seizures in patients who have
diseases that disrupt the blood-brain barrier
• The risk of seizure can be substantially reduced
by a one-time oral dose of 5 to 10 mg of
diazepam, 30 minutes before CM administration
• Seizures that occur can also be controlled with
diazepam
Delayed Reactions
• Defined as reactions that occur between 1 hour and
1 week after CM injection
• Data on delayed reactions are difficult to accurately
collect
• Skin reactions account for the majority of true late
reactions
– Red spots or bumps, weltlike swelling, hives
• Salivary gland swelling (or iodide “mumps”)
• Patient receiving interleukin-2 may reexperience the
side effects of that medication after receiving CM
Renal Dysfunction Terminology
• Renal failure
– The inability of the kidneys to maintain homeostasis,
resulting in the accumulation of nitrogenous wastes
• Renal insufficiency
– Renal function is abnormal but capable of sustaining
essential bodily functions
• Nephropathy
– Denotes any condition or disease affecting the kidneys
– Sometimes used synonymously with renal impairment
PREMEDICATION
• The standard in most facilities for medical
premedication is
– Oral prednisone 50mg 24,12,2 hours before exam
– 50 mg Diphenhydramine PO
– 300 mg Cimetidine in some facilities
• blocks the action of histamine
• Always have patient hydrate before and after
examination
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CONTRAST ALLERGY PREMEDICATION GUIDELINE
If patient is allergic to contrast, scheduled to receive contrast, and has not received
premedications, give the following
– Methylprednisolone (Solu-medrol ®) 125 mg IV time one dose
– Diphenhydramine (Benadryl®) 50 mg IV time one dose
– Famotidine (Pepcid®) 20 mg IV time one dose
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If patient is allergic to contrast, scheduled to receive contrast, and has taken premedications
in advance, notify Radiologist of premedications taken. Recommended “13 hours in
advance of procedure pre-medication schedule” is as follows:
• Prednisone 50 mg p.o., 13 hours prior to procedure
Prednisone 50 mg p.o., 7 hours prior to procedure
• Prednisone 50 mg p.o., 1 hour prior to procedure
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Diphenhydramine (Benadryl®) 50 mg p.o., 1 hour prior to procedure
LABWORK AND VITALS
• Renal function tests
– Creatinine
• Male > 1.5
• Female > 1.3
– Blood Urea Nitrogen ( BUN )
• 7-18 mg/dl in adults
• 5-18 mg/dl in children
• Average accepted is 5- 25mg/dl not >30mg/dl
– Glomerular filtration rate ( GFR )
• > 90
stage 1 normal
• 60 to 89
stage 2 mild
• 30 to 59
stage 3 moderate
• 15 to 29
stage 4 severe
• < 15 or dialysis
kidney failure
CLOTTING FACTORS
• The levels are used in biopsy and abscess drainage
• All used for blood coagulation
• Lab blood tests
– Partial thromboplastin time ( PTT )
• 60-85 seconds
– Prothrombin time ( PT ) ( INR )
• 10-14 seconds 2 times more for patients on blood
thinners. Over 30 seconds out of safe limits
– Platelets
• Level should be 150,000 – 350,000/mm3
• Platelets make the clot, other chemicals lock the clot in
place
D-dimer blood test
• D-dimer indicates the presence of an
abnormally high level of fibrin degradation
products in your body. It tells your doctor that
there has been significant clot (thrombus)
formation and breakdown in the body, but it
does not tell the location or cause.
• D-dimer plus MDCT is used to evalulate
patient with a suspected PE
Assessment
• Technologists begin to assess the patient when
they first introduce themselves
– Note the patient’s breathing, skin coloration, and
overall health
• Visual and verbal contact with the patient should
be maintained throughout the examination
• Special monitoring devices are not generally
required for routine CT examinations performed
on stable patients
Vital Signs
• The best early indicators of a problem are a
change in vital signs
– Body temperature
– Pulse
– Respiration
– Blood pressure
Body Temperature
• Body temperature is taken by placing the
thermometer in the mouth, the ear (using a
tympanic infrared thermometer), the axilla, or
the rectum
• In the CT department, the thermometer is
most often an electronic, battery-operated
device with disposable protective sheaths
• Normal range of oral temperature is 36.0°C–
38.0°C
Pulse
• The alternate expansion and recoil of an artery
• In general, pulse can be felt wherever a
superficial artery can be held against firm tissue
Pulse (cont’d)
•
•
•
•
•
The patient’s blood pressure can impact the ease of palpability of a pulse
Average adult
– 60 to 100 beats per minute
Athletic adult
– 45 to 60 beats per minute
Children
– 95 to 110 beats per minute
Infants
– 100 to 160 beats per minute
Respirations
• Number of breaths a person takes per minute
• Typically measured when the patient is at rest
• Commonly accepted normal ranges are
– Adults: 14 to 20
– Adolescent youth: 18 to 22
– Children: 22 to 28
– Infants: 30 or greater
Blood Pressure
• Pressure exerted by circulating blood on the
walls of the vessels
• The systolic pressure is the peak pressure in
the arteries
– Occurs near the beginning of the cardiac cycle
• The diastolic arterial pressure is the lowest
pressure
– Occurs at the resting phase of the cardiac cycle
Blood Pressure (cont’d)
• Although there is a wide variation, a typical
value for a resting, healthy adult is 120 mm Hg
systolic and 80 mm Hg diastolic
– This is written as 120/80 mm Hg
– And spoken as “one twenty over eighty”
OXIMETRY
• Measures the oxygen saturation of a patient's
blood (as opposed to measuring oxygen
saturation directly through a blood sample)
and changes in blood volume in the skin.
Pulse oximeter
LEVELS
• A blood-oxygen monitor displays the
percentage of arterial hemoglobin in the
oxyhemoglobin configuration. Acceptable
normal ranges are from 95 to 100 percent,
although values down to 90% are common.
For a patient breathing room air, at not far
above sea level, an estimate of arterial pO2
can be made from the blood-oxygen monitor
SpO2 reading.
D-dimer blood test
• D-dimer indicates the presence of an
abnormally high level of fibrin degradation
products in your body. It tells your doctor that
there has been significant clot (thrombus)
formation and breakdown in the body, but it
does not tell the location or cause.
• D-dimer plus MDCT is used to evalulate
patient with a suspected PE
General Phases of Tissue
Enhancement
• The difference among phases is
predominantly determined by the rate at
which the contrast material is delivered and
the time that elapses from the start of the
injection and when scanning is initiated
– Bolus phase
– Nonequilibrium phase
– Equilibrium phase
Bolus Phase
• Immediately follows an IV bolus injection
• AVID of 30 or more HU
• Arterial structures are filled with CM; venous
structures not yet filled
Nonequilibrium Phase
• Follows the bolus phase; begins approximately 1
minute after the start of the injection
• AVID of 10 to 30 HU
• CM is still in arteries, but also in veins
Equilibrium Phase
• Last phase of tissue enhancement
• It can begin as early as 2 minutes after the bolus
phase
• AVID is less than 10 HU
• CM is mostly emptied from arteries, greatly
diluted in the veins, and has soaked the organ
parenchyma
Phases of Contrast Enhancement
• The exact timing of the start and end of each of
the three phases is affected by many factors,
including injection parameters and the condition
of the patient, particularly the patient’s cardiac
output
• Injection protocols are designed by first
determining the time window during when
contrast material is likely to first arrive in the
organ or vessel of interest and when most of the
contrast has vacated
Route of IV Contrast Media
• The route that IV CM takes follows a relatively
predictable sequence of vascular and organ
enhancement with various mixing processes
Typical Contrast Arrival Times
CM Injection for Routine Brain
• Notable exception to the general rules of CM
injection
• Injection rate is not important
• Scan delay is only important in that scans are
not performed too soon after injection
– CM must have time to cross the blood-brain
barrier
Methods of CM Delivery
• Drip infusion
– CM is allowed to drip in during a period of several minutes
– Scanning begins after most, or all, of the CM is in
– Can be used for routine brain scans, but not appropriate for other
examinations because all images are obtained in the equilibrium
phase
• Bolus
– Rapid injection of CM, either by hand or mechanical injector
Hand Bolus
• Variable flow rate because of syringe size,
contrast viscosity, IV catheter size, and
operator strength
• Results in inconsistent images that are not
readily reproducible
• Primarily used when injecting into standard
PICC and tunneled or non-tunneled central
venous catheters
Mechanical Injectors
• CT injectors may have a single head for affixing
the syringe or they may accommodate two
syringes
• Include a programmable pressure limit
• CM is administered at the selected rate(s), unless
the pressure reaches the maximum psi set
• Safety precautions must be strictly adhered to
– Prevent CM extravasation
– Prevent air embolism
Factors Affecting Contrast
Enhancement
• Pharmacokinetic factors
– Largely controllable
• Patient/equipment factors
– Largely outside the technologist’s control
Pharmacokinetic Factors
• CM characteristics (concentration, osmolality,
viscosity)
• CM volume
• CM flow rate
• CM flow duration
• Scan delay time
• Total scan time
CM Volume, Flow Duration, Flow Rate
• The rate at which contrast media is injected
and the volume of contrast used significantly
affect the time needed for the contrast to
reach peak enhancement
– More pronounced for aortic enhancement than
for hepatic enhancement
– Therefore, precise injection parameters,
particularly scan delay, are more important for CT
angiography than for routine body imaging
• Affected by scanner speed
Time-Density Curves
• Graphically depict the consequences of varying contrast dose and flow rate
CM Volume, Flow Duration, Flow Rate
(cont’d)
• For a constant volume and concentration of
CM, as flow rate is increased, there is a
decrease in the time to peak enhancement
– Hence, scan delay must be adjusted according to
flow rate
– Increasing the flow rate shortens the duration of
the injection
CM Volume, Flow Duration, Flow Rate
(cont’d)
• For CT angiography, the scan timing must be
precise
– Image acquisition that is too soon (i.e., scan delay
too short) will miss the contrast bolus
– Image acquisition that is too late may not provide
adequate opacification, particularly of small
vessels
• Manipulating the flow rate during an injection
can improve the likelihood of scanning during
optimal vascular enhancement
Patient and Equipment Factors
• Patient factors
– Cardiac output
– Weight
• Equipment factors
– Scanner speed
• Primarily determined by the number of detector rows
Automatic Injection Triggering
• Two methods exist for individualizing the scan
delay to adjust for patient factors
– Test bolus
– Bolus triggering
Test Bolus
• 10–20 mL of CM is injected and several trial
scans are taken to determine the length of
time from injection to peak contrast
enhancement in a target region
– Trial scans are done using very low mAs
– Begin from 8 to 15 seconds after the start of the
injection
– Scan delay is calculated using the formula:
Trial scan delay + 2 x image @ peak
enhancement + 3 sec
Bolus Triggering
• Uses the contrast bolus itself to initiate the
scan
• A series of low-radiation scans monitor the
progress of the contrast bolus
• Once adequate enhancement is seen the table
moves to the starting level and scanning
begins
• A drawback is that a technologist cannot stay
with the patient to monitor the injection site