The nurse dresses Joe's wounds, and Joe feels comforted by her presence.
Joe knows that the rat is a dream and tries to think of ways of preventing nightmares about it. He recalls how as a kid, he would wake himself up from a bad dream by yelling while still inside the dream, but he doesn't have that option now—he doesn't even have the option of opening his eyes.
Joe resolves not to think about the rat when he feels himself drifting asleep, but he doesn't have any indicators of when he even feels sleepy: he can't yawn, or stretch, or blink, or even really know that he's tired.
Joe thinks about how in his current state he can't even always tell when he is awake and when he's asleep: daydreams and real dreams melt together. He decides that he needs to concentrate on being awake and not think about the past. His mind is, after all, the only tool he has left.