If you were a doctor and someone were in jeopardy and you heard "is there a doctor here" would you respond or ignore? If you responded what are the worst-case consequences if your help doesn't help?

You took a oath to save lives so you would do your best and accept the results of your efforts. The worst  would be if the person died or became a vegetable because of your efforts.

I would respond definitely.  If I were to guess, I'd say with the exception of special circumstances, the majority of doctors would respond to someone in an emergency situation.  After all, they take the Hippocratic Oath which, in part, says, "I will remember that I remain a member of society, with special obligations to all my fellow human beings, those sound of mind and body as well as the infirm."  I think we all know what the worst case scenario is if a doctor fails to help a patient.  

Thank you for your reply PC! :)