The centre for control of body temperature lies in the brain. The brain senses body temperature and adjusts to keep it at constant level. There is apossibility that stroke
may have involved that area and so he is not able to regulate body temperature. Heavy sedation itself can cause unresponsiveness. Additionally large stroke develops brain swelling
in 48-72 hours and the rise in pressure due to this swelling can cause unresponsiveness. Since you said it was a massive stroke so keep fingers crossed and hope for the best.