case volume - what does it mean?

Hello,

I am translating an article about the income of anesthesia providers in the US and am not sure what "case volume" means in the following context:
Revenue derived from clinical practice depends on patient insurance demographics ( also known as "payer mix"), case volume, and average anesthesia units.

Does it mean "number of patients" or "number of procedures" performed? S , for example one patient could require 2 o 3 procedures at a time ( e.g. two peripheral blocks).
Thanks for your help, English is not my mother tongue

Allda