Are there any common ingredients in epidual in childbirth & local anaesthesia in dental work that may induce syncope, fever, or heart palpitations?

Yes (dental): Not at all sure about epidurals used in childbirth but many dental local anesthetics have Epinephrine (adrenaline) to prolong the anesthetic effect. This can definitely cause palpitations depending on your sensitivity to it. Syncope is usually due to anxiety associated with the injection so not technically ingredient related. I'm not aware of any ingredients in dental preparations that cause fever.

Epinephrine: Epinephrine (adrenaline) can produce heart palpitations. Epi is common in most dental anesthetics, though if you had a reaction to it it would only last a few minutes while you were in the dental chair.

Local anesthetic : Yes, Epinephrine is usually used in both.

Epinephrine: The only agent that i can think of is epinephrine. Some of the agents used in local anesthetics can cause some of these symptoms, but would be present in epidurals, not in dental anesthesia. Talk to your anesthesiologist about your concerns.