Aw geez, I'm gonna be on heparin, Lovanox , maybe next month in anticipation of a new shoulder.
I consult for a company that refines and distributes heparin to pharmaceutical companies. The adulterant has been identified and the controls are in place to assure that it is not there. I know; I do the validation. Additionally, this company has eliminated China as a source for the raw material.
My wife had an operation last Spring and was on levenox (enoxaparin) for a couple weeks post-op (cervical fusion). This issue is not a problem at this time. There are several groups working on heparin from a bioengineering standpoint, so that their product would not originate from an animal (would use the pure enzymes in a factory setting).
Good luck on your operation.