Exit the station to enter the bus stand(within station premises) and board any bus going towards Thiruvottiyur/Ennore(101, 1A, 1B, 1C, 1G etc) and you can get down at Royapuram Police Station/Kalmandapam bus stop and walk to the hospital from there. Of these 5 buses, 1A has the best frequency but you will surely get one of the buses within 5 minutes..