Can any body help me how to use Siemens900c in anesthesia and pl tell me what are the accesories to be purchased with the machine

You need to change two things. You will need to either connect the anesthesia circuit to the ventilator or buy the anesthesia manifold that allows you to connect the Siemens vaporizors.

You will need to purchase the gas evac kit from Siemens. Look for used equipment on the internet or check with Siemens in Sweeden. A local Siemens person should connect you with Sweeden.

Here is a link to somebody with spare parts for Servo Anesthesia.

http://www.agiannidis-medizintechnik.com/gebrauchtgesamt.htm