MSDN - Drug dosing in RRT and hemodialysis & peritoneal
dialysis Exam 4 Questions with 100% Correct Answers
what is diffusion?
movement of solute down a concentration gradient through the pores of the dialysis membrane, i.e.
from an area of higher concentration (blood) to one of lower concentration. Most efficient for
removal of small molecular weight drugs.
What is convection?
removal of plasma water from the blood compartment by ultrafiltration due to a pressure difference
across the membrane. Most efficient at removal of larger MW drugs
drug specific factors affecting drug removal during dialysis
molecular weight
protein binding
volume of distribution
pore size
membrane surface area
ultrafiltration coefficient
blood flow
dialysate flow
duration of dialysis
how does MW affect drug removal during dialysis
large molecules less likely to diffuse due to limitations of membrane pore size and less contact with
membrane pores
how does protein binding affect drug removal during dialysis
highly protein bound drugs not substantially removed due to large size of protein relative to pores of
the membrane
how does volume of distribution affect drug removal during dialysis?
relates to drug exposure to the dialyzer
-larger Vd indicates extensive tissue binding and less free drug in the plasma compartment to be
dialyzed
how does membrane pore size affect drug removal during dialysis?
large pore size more conducive to removal of larger MW solutes compared to conventional
membranes
, how does membrane surface affect drug removal during dialysis?
larger surface area provides more contact sites for solute removal and may lead to increased increase
how does ultrafiltration coefficient effect drug removal during dialysis?
KUF is the volume of fluid per hour transferred across the membrane per mm Hg of transmembrane
pressure (TMP)
how does blood flow affect drug removal during dialysis?
increases in blood flow rates generally increase clearance of small molecules by maintaining the
concentration gradient
how does dialysate flow affect drug removal during dialysis?
increases in dialysate flow increase diffusion by maintaining a concentration gradient between
dialysate and blood.
dialysate flow rates are typically between 500-800 mL/min for intermittent procedures
how does duration of dialysis affect drug removal during dialysis?
longer procedures allow more time for drug contact with membrane or filter
higher values of Vd, protein binding, and MW = __________clearance
lower
higher values of process specific factors (membrane pore size, time, membrane surface, etc) =
____________ clearance
higher
elimination by hemodialysis is ____ order
1st
what is the redistribution phenomenon ?
-occurs when dialysis removes drugs from the plasma compartment at a rate exceeding movement
from tissue to plasma- equilibrium between the plasma and tissue compartment does not occur
during the dialysis procedure
-results in a rebound of plasma drug concentration for drugs that distribute in the tissue
compartment when the dialysis procedure is stopped
supplemental doses generally required when Cld >_________ of total clearance
25-30%
dosing in RRT is dependent on the modality and ___________
duration
strategies for rational drug dosing during renal replacement therapy
-administer drugs with significant dialysis clearance post hemodialysis or give a supplemental dose if
practical
dialysis Exam 4 Questions with 100% Correct Answers
what is diffusion?
movement of solute down a concentration gradient through the pores of the dialysis membrane, i.e.
from an area of higher concentration (blood) to one of lower concentration. Most efficient for
removal of small molecular weight drugs.
What is convection?
removal of plasma water from the blood compartment by ultrafiltration due to a pressure difference
across the membrane. Most efficient at removal of larger MW drugs
drug specific factors affecting drug removal during dialysis
molecular weight
protein binding
volume of distribution
pore size
membrane surface area
ultrafiltration coefficient
blood flow
dialysate flow
duration of dialysis
how does MW affect drug removal during dialysis
large molecules less likely to diffuse due to limitations of membrane pore size and less contact with
membrane pores
how does protein binding affect drug removal during dialysis
highly protein bound drugs not substantially removed due to large size of protein relative to pores of
the membrane
how does volume of distribution affect drug removal during dialysis?
relates to drug exposure to the dialyzer
-larger Vd indicates extensive tissue binding and less free drug in the plasma compartment to be
dialyzed
how does membrane pore size affect drug removal during dialysis?
large pore size more conducive to removal of larger MW solutes compared to conventional
membranes
, how does membrane surface affect drug removal during dialysis?
larger surface area provides more contact sites for solute removal and may lead to increased increase
how does ultrafiltration coefficient effect drug removal during dialysis?
KUF is the volume of fluid per hour transferred across the membrane per mm Hg of transmembrane
pressure (TMP)
how does blood flow affect drug removal during dialysis?
increases in blood flow rates generally increase clearance of small molecules by maintaining the
concentration gradient
how does dialysate flow affect drug removal during dialysis?
increases in dialysate flow increase diffusion by maintaining a concentration gradient between
dialysate and blood.
dialysate flow rates are typically between 500-800 mL/min for intermittent procedures
how does duration of dialysis affect drug removal during dialysis?
longer procedures allow more time for drug contact with membrane or filter
higher values of Vd, protein binding, and MW = __________clearance
lower
higher values of process specific factors (membrane pore size, time, membrane surface, etc) =
____________ clearance
higher
elimination by hemodialysis is ____ order
1st
what is the redistribution phenomenon ?
-occurs when dialysis removes drugs from the plasma compartment at a rate exceeding movement
from tissue to plasma- equilibrium between the plasma and tissue compartment does not occur
during the dialysis procedure
-results in a rebound of plasma drug concentration for drugs that distribute in the tissue
compartment when the dialysis procedure is stopped
supplemental doses generally required when Cld >_________ of total clearance
25-30%
dosing in RRT is dependent on the modality and ___________
duration
strategies for rational drug dosing during renal replacement therapy
-administer drugs with significant dialysis clearance post hemodialysis or give a supplemental dose if
practical
