NeighborhoodThreat
Bluelight Crew
I'd proceed with caution (in regards to mixing ketamine and tramadol) - check out the threads in PD about ketamine, I believe there is (or was) a combinations with ketamine thread...

If you can't find any information saying you shouldn't do it, I say still proceed with caution, and use lower than normal doses of both the ketamine and tramadol...I'm not a ketamine expert, but I remember reading people mentioning it killed pain (possibly had action at the mu-opioid receptor). Could cause an interaction with ketamine? Possibly.
Did you check out the threads in PD?