Basically they are the same thing. Intesive care stems from the word Intensive Care Unit (ICU). Critical Care is used in the same fashion as Intensive care. Most medical people call it Critical Care. It seems like to me that Intensive care is used more to refer to a place, where as critical care is used more to refer to a job type. Just my opinion on it. Basically they are the same.
Just my .... I work in the "intensive care" unit, but I work under the "critical care" umbrella, which includes our step down unit, nicu, intermediate care, and a transition unit, which holds overflows from most floors, except icu.