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

•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

•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

• 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

• 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

• Improved patient safety• Improved patient retention• Increased referral• Improved patient compliance• Greater profitability• Reduced risk of malpractice suits

• 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• Language• Power struggles• Misreading of body language• Fuzzy transmission• Receiver distortion

• 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

•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

•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

•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

• 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 – 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▫Contaminated environment▫Therapeutic regimen ( chemo ) ▫Contaminated equipment▫Contamination during a procedure

•About 10% of patients contract this type of infection

•The most common in the hospital or clinic surroundings

• Infections contracted in acute care

•They are increased by several factors▫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

•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 )▫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

•Parenteral ( any other than by mouth )▫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 – 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• 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• 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

• 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• 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– 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• 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• 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– 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– 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– 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

– 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, A = Anemia, B = Bone lesions hypercalcemia

• 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 contrast-

enhanced 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

• 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

• 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

• 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