When his fever spiked, he thought someone was setting him on fire. When orderlies slid him into an MRI, he thought he was being fed into an oven. Frequent catheter changes seemed like sexual abuse. Dialysis? He thought someone was taking blood out of a dead woman’s body and injecting it into his veins.The horrifying, violent hallucinations plagued David Jones, now 39, during a six-week stay in the intensive care unit at Chicago’s Northwestern Memorial Hospital — and for months after he was discharged. He thought he was going crazy and felt very alone.He wasn’t.