Unconciousness is beyond messed up. My friend and I were fighting zeds and I accidently hit him with a baseball bat; he had no shock damage whatsoever, blood was good, etc, and he instantly went down. He had a helmet on as well, and I hit him in the chest and he instantly went unconcious.
Now here's the gamebreaking part, he couldn't be woken up. I used a Epen, he didn't wake up. I gave him saline. Didn't wake up. Keep in mind he's completely healthy anyways so Im pretty much wasting these items trying to wake him. Eventually I told him to try reconnecting, but when he did so he died.
tl;dr Unconciousness is bugged (sometimes?), you can't wake up from it. This happened to us once in EXP and happened again in stable today.