Dialysis

Question 1

Hemodialysis

Answer 1

Many changes over the ensuing years an increase in the efficacy and biocompatibility of HD membranes

Change in dialysis that has impacted pharmacotherapy immensely

Question 2

What is hemodialysis

Answer 2

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

Question 3

Dialysis clearance

Answer 3

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

Question 4

Convection

Answer 4

if > 1 L/treatment, conductive clearance must be considers

Question 5

Drug removal efficiency

Answer 5

MW

WATER

PROTEIN BINDING: less likely going to be cleared

Vd

Question 6

Membranes

Answer 6

smaller pores
Conventional: cellulose
Semi-synthetic

Larger pores
synthetic

Question 7

Molecular weight

Answer 7

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

Question 8

Water solubility

Answer 8

poorly water soluble drugs:limit transport into dialysate

Question 9

Protein binding

Answer 9

limits dialytic removal. as protein binding increases dialytic clearance decreases

Question 10

Vd

Answer 10

drugs with large volume of distribution will have limited removal

Question 11

Plasma dialysis clearance

Answer 11

square root of 113/MW of drug times fu

Question 12

Hemodialysis PK

Answer 12

given three days a week

In AKI, HD maybe more frequent to account for fluid overload

Question 13

Concentrations and dialysis

Answer 13

Ktotal= Kd + Ke

Kd=Cld/V

Question 14

How do we determine removal and subsequent dosing?

Answer 14

Dose=(Ctarget-Cend dialysis) x Vd