That's a common occurrence unfortunately. But, the medical community is well aware of this problem.
Moving him to Intensive Care does not necessarily mean they are out of options. They are monitoring him closely.
If he's got some sort of resistant bacterial infection-they are probably going to want to use various different meds/combinations of meds to try and knock it out. All meds have side effects so the person needs to be watched closely for this reason too.
Prayers being said for president George H.W.Bush for a speedy recovery and for more time here on earth to be with his family, or, if his time is done here- for a peaceful transition home to the house of our Lord Jesus Christ, and comfort for his family- Amen