Well this is a question of ethics. Basically this is where you are on the scale between: "Would you stop if your partner gets unresponsive? Most ppl would I guess.

Would you stop when your partner gets goosebumps? Most ppl won't."

And

"Would you play with an intoxicated partner?"

Here they stated that the sub was extremely vulnerable. When you are vulnerable you are suggestable. If you are very vulnerable you are very suggestable. And if you are suggestable you may don't use your safe word even if you want to. This is also a part of consent. When you start a session you are consenting to a degree to this. (This is Position agnostic btw)

If someone gets extremely vulnerable unexpectedly during a session you get to the spectrum above. If you play without consent with intoxicated ppl this will not matter for you, but also you are already kinda a bad person.

On the spectrum above you have different states of ecstasy at the highest discribed (assuming they are physically fine) they are unable to revoke their consent. In fact they will get more and more unable to revoke their consent. And this is also fine because to a degree they consented to it.

When you stop to respond or are unable to safeword you are into CNC territory. If you have direct or indirect consent that's fine. I will not advocate against CNC play because, like the situation in the op, it is hot for a lot of ppl. For example with my wife I would also keep going if they are unresponsive because I know their limits pretty well and we discussed it.

The OP does not mention consent. To the contrary it even suggests that they are still in a starting phase and thatneither they not their sub did expect this situation.