PLEX volume

 Q: How the "Plasma volume" can be calculated in a patient?

Answer: 

The formula to estimate the plasma volume in an adult patient is: 

 Estimated plasma volume (in liters) = 0.07 x weight (kg) x (1 - hematocrit)

Clinical significance: When patient requires "plasma Exchange" (PLEX) for any reason, it is important to be aware of patient's plasma volume. It is not recommended to exchange more than 1-1.5 L of plasma in one session. This is for two reasons. First, initial 1 to 1.5 plasma volumes removes the largest concentration of the targeted substance. Second, patient may not be able to tolerate PLEX beyond this volume.

#hematology

References:

1. Kaplan AA. A simple and accurate method for prescribing plasma exchange. ASAIO Trans 1990; 36:M597. 

2. A Compendium of Transfusion Practice Guidelines, 3rd ed, Fridey JL, Marcus L (Eds), American Red Cross, 2017.