31 years old male with history of weakness all forlimbs with more in lower limbs for 1 week with altered voice change and diplopia present. Power all forlimbs 5/5 tone5/5 plantar down going and reflexs absent.

Sensation normal  On investigation CSF normal with protein 48 MRI brain and spine normal, NCV near normal  Suspecting GBS Put on ivig day 2,  But no response yet. What to do next?