Week 2: Patient Prep and Contrast Agents Flashcards
Why are laboratory values important
if patient is candidate for iodinated contrast
What laboratory values show info about patients kidney functions?
serum creatinine, BUN, eGFR
Normal range of Serum Creatinine
Canada: 50-90 umol/L for female
70-120 for male
American- 0.6-1.7 mg/dl
Normal Range of BUN
7-25 mg/dL
Normal Range of eGFR
above 60ml/min/1.73m
What goes eGRF measure
how much blood passes through kidneys per minute
What provied information about bloods coagulation ability
Prothrombin PT
Partial Thromboplastin time PTT
Platelet Count
Typical Range of PT
11-14 seconds
Typical Range of PTT
25-35 seconds
Typical Platete Count
150,00- 400,000 platekets per mm3
What blood thinners should we pay attention to
Warfarin, Coumadin, Heparin, Plavix, aspirin
Normal range of oral temperature
36.0 - 38.0 C
Average adult pulse
60-100 bpm
Average childs pulse
95-110 bpm
Average infants pulse
100-160 bpm
Adult normal respiration rate
14-20
adolescent youth normal respiration rate
18-22
a child’s normal respiration rate
22-28
Infancts normal respiration rate
30 or greater
Healthy adults BP range
120/80 mmHG
Why are iodinated Contrast agents good
-safe
-water solvable
-easy to administer
-easily distributed/ eliminated by body
Why do IV agents show large attenuation difference between structures
-different tissues enhance differently
-shows different in normal vs abnormal tissue
What is Osmolality
-number of particles in solution per unit liquid as compared with blood
-major factor in non-allergic reactions
High-osmolality compared to blood (HOCM)
7 time blood osmolaity
Isomolar agents compared to blood (IOCM)
same compared to blood (290 most/Kg H20
Low-osmolality compared to blood (LOCM)
2 times compared to blood
What affects viscosity
-brand
-temperature
-concentration of CM
What is viscosity
thickness or friction of luid as it flows
What does viscosity affect when injection
injectability of CM through small-bore IV catheters/needles
Ionic agents contain
molecules that will form ions in solutions
Non-ionic agents contain
molecueles that dont disassociate
How are iodinated agents cleared from the body
not metabolized but excreted almost fully by kidneys
How long does it take for iodinated agents to clear
half life in patients 2 hours (eject 50%)
Side Effect Symptoms and Signs
- Warmth
- Feeling of urination
- Funny taste (metallic)
- Few hives
- Minor itchiness
- Oral contrast may cause diarrhea
How is CM dose determined
by iodine concentration and volume delivered
Adverse Reaction Symptoms and Signs
- Major hives
- Breathing problems
- Swelling of face, throat or tongue
- LOC (loss of consciousness)
Chemotoxic reactions
Result from the physiochemical properties of CM, dose & speed of injection
Idiosyncratic reactions
- All other reactions, largely unpredictable
- often within an hour
- mimic allergic reactions but are rarely because of an allergy
Mild idiosyncratic reaction
short duration and self limiting
Moderate idiosyncratic reaction
no immediately life threatening but an progress to
Severe idiosyncratic reaction
potentially or immediately life threatening
What can renal function be estimated using
-glomerular filtration rate GFR
-Effective renal Plasma flow ERPF
-Serum Creatine SeCR as index of GFR : fast and inexpensive
-estimated glomerular filtration rate (eGFR): gaining more attention, potentially better marker of CIN risk
- SeCR and eGFR most commonly used
What are risk factors for idiosyncratic reaction
-previous CM reaction
-asthma
- history of allergies to food/drugs
- NOT risk factor: seafood allergy
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
- any condition or disease affecting the kidneys
- sometimes used synonymously with renal impairment
Contrast Induced Nephropathy (CIN)
- IV contrast media that affects kidney function
- Progressive rise in SeCr within 24 hrs & typically nonoliguric (high urine output)
- CM can result in significant nephrotoxic effects in high-risk patients for nephropathy.
Postcontrast acute kidney injury (PC-AKI)
an acute impairment of renal function that occurs within 48 hours of intravascular administration of contrast material.
What are CIN risk factors
-eGfr less than 30
-history of DM and recent IV CM
-Large volume of CM
-History of congestive heart failure
How to prevent CIN
-identify patients at high risk
-use LCOM or IOCM
-ensure patient hydration
-minimize CM volume
-allow 48 between CM procedures
-discontinue nephrotoxic medication before procedure
Metformin Therapy
-CM can result in CIN, patient taking metformin who go into renal dysfunction can have an accumulation of lactic acidosis
- if eGFR less than 60 metformin should be temporarily discontinued after CM and can be resumed after 48 hours
Can a patient on dialysis receive CM?
- If dialysis is temporarily DO NOT give CM to patient
- if the patient is on end-stage renal failure CM can be given and can continue their routine dialysis schedule
CM effect on thyroid function
- normal thyroid = no effect
- hypothyroidism = insignificant effect
- hyperthyroidism = CM may precipitate thyroid storm (thyroid hormone reaches dangerously high level, life threatening)
What pulmonary effects can CM cause
-bronchospasm
-pulmonary arterial hypertension
-pulmonary edema
- to reduce risk use LOCM
Patients at an increased risk for pulmonary effects have a history of
-pulmonary hypertension
-bronchial asthma
-heart failure
What affect does CM have on the CNS
- can provoke seizures in patients who have disease that disrupts blood-brain barrier
- control or reduce risk of seizure by administering 5-10 mg of diazepam 30 minutes before CM
Delayed Reactions to CM
- reactions that occur 1hr to 1 week after CM
- skin reactions primarily (red spots, hives, welts or bumps)
- salivary glad swelling possible (more common in patients who have under gone chemotherapy)
Gastrointestinal CM
- help to distinguish loops of bowel from cyst, abscess, or neoplasm
- oral CM: used for most abdomen and pelvis CT (use Ba-sulfate or more commonly iodinated water-soluble solution)
- Rectal CM: useful for some indications. includes air, Ba-sulfate or 1-3% iodinated water-soluble solution
Barium Sulfate Solutions
- DO NOT use if bowel perforation suspected because that could lead to peritonitis and risk of death
-Most commonly used are positive agents that contain a 1% to 3% barium sulfate suspension (BaSO4) formulated to resist settling - in general the higher the dose the better the bowel pacification (typically used minimum of 500 mL diluted barium sulfate given 45 min-2hrs before exam)(additional 200mL can be given just before scanning the stomach and the small bowel)
low HU oral contrast
- resembles water on image
- o.1% brim sulfate solution
- measures 15-30 HU
- advantages: improved bowel distention (compared to water), faster transit than standard CM barium, more effective visualization of both bowel wall and mucosa
Iodinated Agents for Oral Administration
- HOCM and LOCM: positive agents, can be diluted and administered orally. stimulate peristalsis and cause diarrhea
- 2-5% solution normally used, 1000-1500 mL over 1-3 hrs immediately before scan to descend stomach and small intestine
Water as CM
- Sometimes used in place of a positive agent
- It does not obscure mucosal surface
- Transits rapidly
- Distends the bowel poorly
Air and Carbon Dioxide as CM
- Produces very high negative contrast
- Administered rectally
- Particularly useful in CT colonography/ Virtual colonoscopy
- Both room air and CO2 provide reliable colonic distention (CO2 is better tolerated by most patients)
Intrathecal CM
iodinated contrast agents injected into the intrathecal
space surrounding the spinal cord
