Dialysis Flashcards
Hemodialysis
Many changes over the ensuing years an increase in the efficacy and biocompatibility of HD membranes
Change in dialysis that has impacted pharmacotherapy immensely
What is hemodialysis
perfusion of blood and physiologic solution on opposite sides of a semi-permeable membrane
Diffusion down a concentration gradient from the blood into dialysate
Faster for small solutes, slower for larger solutes
Dialysis clearance
Diffusion is the function of the components of dialysis
membrane composition and surface area: longer the higher surface area
Higher blood flow rate more diffusive clearance
Number of times dialyzer has been used
Convection
if > 1 L/treatment, conductive clearance must be considers
Drug removal efficiency
MW
WATER
PROTEIN BINDING: less likely going to be cleared
Vd
Membranes
smaller pores
Conventional: cellulose
Semi-synthetic
Larger pores
synthetic
Molecular weight
as molecular weight increases, drug clearance decreases
Low influx
MW> 500-800 no effective removal
MW<500 blood flow dependent clearance
High influx
MW 500-1500 significant clearance
MW less than 500 higher Cl than convection
Water solubility
poorly water soluble drugs:limit transport into dialysate
Protein binding
limits dialytic removal. as protein binding increases dialytic clearance decreases
Vd
drugs with large volume of distribution will have limited removal
Plasma dialysis clearance
square root of 113/MW of drug times fu
Hemodialysis PK
given three days a week
In AKI, HD maybe more frequent to account for fluid overload
Concentrations and dialysis
Ktotal= Kd + Ke
Kd=Cld/V
How do we determine removal and subsequent dosing?
Dose=(Ctarget-Cend dialysis) x Vd
