House didn't realise how much he cared for her until he saw she really was hurt. It burned him and as much as House wanted to call her back, he couldn't. He could never be good for her. Kytana was so much more than him, she just couldn't see it. She knew nothing about the asshole he was.
House looked down and closed his eyes as he waited to hear the door shut. And once he did, he made sure that his blood carried enough morphine to take him into the deepest of slumbers.