Hemodialysis Flashcards
Hemodialysis
-perfusion of blood and physiologic solution on opposite sides of a semi-permeable membrane
-solutes move from blood into dialysate (convection, diffusion)
Diffusion
-movement down a conc gradient
-fast for small solutes
-slow for Large
Convection
-ultrafiltration drags dissolved solutes across membrane if pores are large enough
Dialysis Clearance
-diffusion: membrane comp, blood and dialysate flow rate, duration, number of times
-Convection: if >1L/treatment, connective Cl must be considered
-drug removal efficiency: MW, water solubility, protein binding, Vd
Hemodialysis membranes
-smaller pores: conventional or semi-synthetic
-Larger pores: synthetic
With increased MW
-drug Cl decreases
-Cl dependent on blood
Synthetic or high flux
-500-1500: significant Cl
-<500: higher Cl than conventional
-blood and body surface dependent
Factors that decrease dialysis removal
-poorly water soluble drugs
-protein binding
-large Vd
Dialytic Cl
-ClHD,b A/V
-ClHD recovery
Hemodialysis PK
-MWF or TRS for outpatient w ESRD
-newer, slower, longer, more freq refiments
-homehemodialysis
-In AKI, HD maybe more freq to account for fluid overload
Time Course of Drug Concentrations and Dialysis
Dose = (Ctarget - Cdialysis)Vd
Dosing in HD
-for drugs with NTI
-TDM should be employed
-doses should generally be given after hemodialysis to minimize additional removal
CRRT
-used in AKI, when hemodynamic stability is important
-blood flows down one side of membrane
-water and solutes pass across membrane
-replace fluid electrolytes w replacement solution
Dialysis
-diffusive removal, movement down a conc gradient
-fast for small solutes, slower for larger solutes
Hemofiltration
-convective removal, based on pressure gradient, drags dissolved solutes across the membrane
