User blog comment:Xilinoc/Ch. 679 - THE END/@comment-28850184-20160626054720/@comment-893506-20160626060705

Blut Vene (thanks for asking, we're here to help) usually only appears in a defensive situation, and while I do admit it is possible it could react to this, it doesn't seem very likely. During Yhwach's first invasion of the Soul Society, it was used to stop him from inflicting a critical (and very likely fatal) wound on Ichigo. And other Quincies have also used it to repel other attacks that would have injured them.

Yhwach made it clear that he's basically going to take back the Quincy power Ichigo has within him. So, while Blut Vene may be used to try on stop it, it doesn't seem very likely that this is the case. Still, it's too soon to say, and we'll have to wait until the release of the next chapter(s).