**Daugirdas ****mathematical**** formula ****to ****calculate:
**

**Kt/V**= -ln (R – 0.03) + [(4 – 3.5R) x (UF ÷ W)]

Where…

R= post HD BUN/preHD BUN

UF= UF volume in L

W= post dialysis weight in kg

*Online calculators and normograms are available to calculate Kt/V using formula above.*

**The quick and dirty method:**

- If the dialyzer’s clearance (K) is known (based on the packet insert provide by the manufacturer at a Qb of 400ml/min) and is 250 ml/min and the dialysis session time is 240 minutes (4 hours)
- then
**Kt**(dialysis dose)= 250 x 240 = 60,000ml or 60 liters

- then
- If the patient weighs 70kg. His TBW is 60% of 70kg
- then
**V**= 70 kg multiplied by .60 = 42 liters

- then
- So the ratio –
**K**multiplied by**t**to**V**, or**Kt/V**–- KT/V for this patient will be= 60/42 = 1.42

**Caveat:** *If this same patient has 3 kg of edema fluid (EDW of 70kg) then V = 60% (70kg)+ 100%(3kg)= 45L and not 42L. This is because edema fluid adds to the TBW in its entirety as urea distributes evenly across body water.*