chapter 12 contrast agents Flashcards
to distinguish adjacent tissues on a CT image the tissues must have different
densities (attenuation)
CT has 2 main contrast enhancements
intravscular and gastrointestinal
when the contrast agent is of higher density it is refereed to as
positive agent
when the contrast agent is of a lower density
negative agent
contrast has an atomic number of
53
2 tissues must differ by at least ___Hounsfield units to be visibly iffernt on a Ct scan
10
most intravascular drugs are nearly
isotonic
isotonic
have nearly the same number of particles in a solution per unit liquid of blood
osmolaity
refers to the number of particles in solution ,per unit liquid, as compared to blood
high osmolaity
have seven times the osmolaity of blood
low osmolaity
have 2 times the osmolaity of blood
the osmolaity of blood plasma is
290 mOsm/kg water
viscosity
is a physical property that may be described as the thickness or friction of the fluid
half life on contrast
2 hours
contrast does not metabolize and is excreted by the body nearly exclusively by the kidneys through
glomerular filtration
the most common formula for calculating the dose og contrast for peds
2mL/kg
less than ___ of the dose of contrast agent given to the mother is excreted into breast milk
1%
contrast reactions can be broadly categorized as
chemotoxic or idoiosyncratic
when steroid premedication is used it must be given _____before contrast
6 hours
chemotoxic
reactions that stem from the contrast pharamacologic properties
the overall kidney function is described as
clearance
clearance
the volume of plasma that is cleared of a specific substance in a given time
normal adult GFR
120 mL/ min
normal ERPF
500 ml/min
creatinine
by product of muscle protein metabolism generated by the body at a fairly steady rate and excreted entirely by urine
renal failure
the inability of the kidneys to filter waste from the blood
renal insufficiency
when renal function is abnormal but capable of sustaining essential bodily function
nephropathy
any condition or disease affecting the kidneys
anuric ( absence of urine formation)
urine output is less than 50 mL for 24 hours
oliguric (diminished urine formation)
urine output is less than 500 ml for 24 hours
nonoliguric ( normal output of urine )
500 to 6,000 ml for 24 hours
polyuric
urine output in greater than 6,000 mL
