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					CONTRAST
PURPOSE:
  Enables differences in anatomic tissues to be visualized

    Higher atomic number= absorb more x-ray protons
    Bone: calcium high atomic number
    Soft tissue: decreased absorption


•   Instilling contrast changes absorption characteristics of the area…alters subject
    contrast and density differences


•   Enhancing density differences within an area will improve visibility

CONTRAST MEDIA
Diagnostic agent in:
    –   Body orifice
    –   Vascular system
    –   Joints
    –   Ducts

NEGATIVE CONTRAST AGENTS
Radiolucent
  Appear dark (increased density)
  Low atomic number
  Gas…air…crystals…carbon dioxide
  Double contrast studies:
        Stomach
        Large intestine
        Arthrography: knee, shoulder, wrist, hip
  Adverse reaction: Air emboli

POSITIVE CONTRAST AGENTS
Radiopaque= iodinated/barium
  Appear light (decreased density)
  High atomic number
  Barium: BaSO4 Suspension
       Atomic #56
       Compound: 1 barium atom, 1 sulfur, 4 O2
       Clumps…comes out of suspension in
               large intestine due to absorption of water
       Tell pts to drink lots of water

Barium Complications Adverse reactions
Barium NOT water soluble
Not absorbed by the body

Perforation trauma i.e. BE
       Extravasation into abdominal cavity
       Can cause peritonitis
       Surgery to remove

Diverticulitis and colitis cause inflammation and degradation of colon. Colon can rupture.

Vaginal rupture: misplacement of the catheter



•   IODINATED CONTRAST AGENTS

TYPES OF IODINATED CONTRAST AGENTS:
Adverse Reactions of Oil Based Agents:

Anaphylactic shock

Reactions associated with specific exams
   Ex.: reduction of pulmonary function with bronchoscopy

Rare

OSMOLARITY:

Homeostasis: body’s ability to maintain a stable internal condition.

Osmolality

•   a measure of the total number of particles in solution per kg of H2O.

•   the key to understanding IV contrast differences

The characteristic of contrast media MOST responsible for adverse reactions.
HIGH OSMOLAR
   High osmolar agents ( hypertonic) contain more solutes than there are in the cells.
   These solutions draw fluid out of the patient’s tissues...into the bloodstream where it is
     excreted by the kidneys.
   Water inside the cells follow its concentration gradient and leave the cell.
   Solutions of this type are given to patients who have edema because of fluid retention.
   High osmolar contrast agents draw fluid out of the cells and cause dehydration.
   Hypaque 60, Cysto Conray,

LOW OSMOLAR
    –   Low osmolar agents (hypotonic) contain fewer solutes (more water) than the cell.
    –   These solutions are infused slowly into a dehydrated patient to rehydrate.


    –   Low osmolar contrast agents also draw fluid out of the cells but to a lesser degree.
    –   Omnipaque, Isoview, Optiray.

Effects of Osmolality
Increase in osmotic vascular pressure
•   pressure in blood vessels that allows fluid to be pulled from tissues into blood vessels
•   increase can cause fluid overload
    –   Patients with renal failure
    –   Patients with cardiac problems - altered pumping ability
    –   shortness of breath
    –   crackles in lungs
    –   decrease in O2 saturations
    –   anxiety and tachynpnea
    –   wet cough
    –   sweating

Effects of Osmolality
Vasodilation
•   relaxing and widening of blood vessels


•   increase due to extra fluid in vessels


•   Flushing


•   Hypotension


•   pain or pressure with contrast injection



Effects of Osmolality
Calcium binding in cells & tissues
•   calcium regulates electrical & muscle stability in heart


•   Increase osmolarity increases calcium binding


•   Therefore, can cause heart irregularities
         • arrhythmias
        • bradycardia
Effects of Osmolality
Rigidity of red blood cells
•   RBCs need space to move through blood vessels


•   With an increase in osmalarity, RBCs
    – must “squeeze” by increase in particles in solution
    – are less likely to slide though capillaries
    – become stiff and rigid

•   Rigid RBCs can block vessels.


•   Major organ affected = kidneys



VISCOSITY

Two Types of Water Soluble Iodinated Contrast Agents



         Ionic and Non-ionic

Water soluble contrast agents are used for:


    – Vascular studies
    – Urology studies
    – GI work when perforation is suspected
Physical Properties
Ionic and Non-ionic Agents

Water soluble agents are derived from the 6-carbon Benzene Ring.

Both contain iodine

IONIC CONTRAST MEDIA
Iodine Atomic # 53 = radiopaque
Ionic = dissociate into 2 molecular particles in blood plama
1 particle = negative = anion

1 particle = positive = cation
ANION six-carbon bonded hexagon called benzene ring
negatively charged

CATION= positively charged attaches to acid group
Ionic Contrast
           3:2 compound
           the anion and the cation dissociates

    therefore, for every 3 iodine particles for contrast, you get 2 particles that attribute to
     OSMOLARITY.

Non-Ionic Contrast Agents
•   Also derived from the benzene ring
•   Also contains 3 iodine atoms/molecule
•   BUT, does NOT contain an acid group and therefore, does NOT dissociate.
•   Decrease many side effects of ionics
•   Lower-osmolality contrast
•   Hexabrix molecule= too big to have osmotic effects
•   Therefore, considered “non-ionic”
•   Considered a 3:1 compound

•   Lower osmolarity and therefore, fewer reactions

CONSIDERATIONS

•   Adverse reactions associated with ionic contrast are decreased with nonionics.

•   Attributed to lower osmolality of nonionic media.

•   Nonionics cost 2-3 x more than ionics

•   Criteria for nonionics
     –   Reactions to contrast in the past
     –   Asthma or allergies
     –   Cardiac problems
     –   Patients undergoing CT procedures

DRUG INTERACTIONS
GLUCOPHAGE:
Medication to control glucose in Type II diabetes (NIDDM) Adult onset.
Medication must be DISCONTINUED 48 hours prior to contrast exam and
RESUMED after 48 hours post contrast.
Time must be given for the body to clear the contrast prior to resuming medication.
Levels of medication could accumulate if renal failure occurs due to contrast. Combination
   cause shut down of the excretory system.
If the medication cannot be excreted lactic acidosis can result. The blood becomes acetic
   and can be a fatal condition.

RADIN PREP:
Used in patients who have had a contrast reaction in the past.
Patient is unlikely to have a reaction to a non-ionic contrast agent.
MEDICATION ERRORS:
Hypaque in subaracnoid space as in a myelogram may produce convulsions and be fatal.

Check your patient for recent examinations with contrast agents. Especially ER patients.


•   i.e. Special procedures, C.T. scans, IVP...


•   Patient can only tolerate 300-400 cc of contrast per day.


•   Also check when doing a repeat study. Give the system a chance to clear contrast.

TYPES OF REACTIONS:

•   CHEMOTOXIC: Result from the properties of the contrast material, dose and speed of
    injection.


• IDIOSYNCRATIC: All other reactions.
Anaphylactic Reactions:
Not correct terminology...true anaphylactic shock is an exaggerated hypersensitivity
  reaction to an antigen that was previously encountered by the body’s immune system.

The reaction to contrast is Anaphylactic-like...it is independent of dose or concentration of
  contrast. (Pseudoallergic)
Anaphylactic Reactions:
The etiology is unknown.

You can’t have an allergic reaction to iodine.

The body does not produce an antigen against a substance that it needs.
Adverse/Allergic Reactions

•   Unpredictable
     –   70% occur within 5 min. of injection
     –   16% occur after 5 min.
     –   145 occur after 15 min.


•   Mild: “nuisance” symptoms - not life-threatening
•   Moderate
     –   more severe than mild
     –   generally affects lungs and airway


•  Severe: life threatening involving cardiac system
Mild Reactions

•   nausea/vomiting


•   flush sensation


•   heat/pain


•   Hives


• sneezing
Moderate Reactions
•   Wheezing


•   Hoarseness


•   periorbital swelling


•   swelling of lips


•   difficulty swallowing


•   nasal stuffiness

Severe Reactions

•   Hypotension


•   Seizures


•   Tachycardia/Bradycardia


•   Anaphylactic shock


•   Coma
RENAL EFFECTS

•   High osmolar = arteries of kidney to expand

• Arterial expansion = release of vasoconstrictors = constriction of renal arteries
Result:

•   dilation the constriction of renal arteries = diminished blood supply to kidney

•   Osmotic diuresis = increased secretion of urine = dehydration

LAB VALUES- indications of renal disease
BUN= BLOOD UREA NITROGEN
primarily used, along with the creatinine test, to evaluate kidney function under a wide
   range of circumstances and to monitor patients with acute or chronic kidney dysfunction
   or failure.
Increased levels suggest impaired kidney function.
This may be due to acute or chronic kidney disease, damage, or failure.
It may also be due to a condition that results in decreased blood flow to the kidneys, such
   as congestive heart failure, shock, stress, recent heart attack, or severe burns, to
   conditions that cause obstruction of urine flow, or to dehydration.

LAB VALUES- indications of renal disease
CREATININE (waste product of metabolism)
Increased creatinine levels in the blood suggest diseases or conditions that affect kidney
   function.
These can include: damage to or swelling of blood vessels in the kidneys (glomerulonephritis)
   caused by, for example, infection or autoimmune diseases; bacterial infection of the
   kidneys (pyelonephritis); death of cells in the kidneys’ small tubes (acute tubular
   necrosis) caused, for example, by drugs or toxins; prostate disease, kidney stone, or
   other causes of urinary tract obstruction; or reduced blood flow to the kidney due to
   shock, dehydration, congestive heart failure, atherosclerosis, or complications of
   diabetes.
Creatinine can also increase temporarily as a result of muscle injury.
• Normal creatinine = .9 - 1.4 mg/deciliter

Notify Radiologist as soon as the patient exhibits any sign of reaction

				
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