To anesthesiologists, have any zoloft (sertraline) taking patients ever had serotonin syndrome following a procedure?

Very rare: We see lots of patients on ssri's , I have never had a patient develop serotonin syndrome.

Theoretically yes: I have seen serotonin syndrome in a patient in the recovery room after general anesthesia. It occurred after receiving Meperidine (demerol). This medication is often given for pain or shivering after surgery, but can trigger serotonin syndrome in patients taking certain medications that act on serotonin. I would advise you to give your anesthesiologist a list of all the meds you take.