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We have no specific trope for characters following their hippocratic oath, but you might try Honor Before Reason or some of the Healing and Curing Tropes (we do have trope for characters following their hippocratic oath when in trouble: Inconvenient Hippocratic Oath but it doesn't seem to fit here, so).
Might be Turn the Other Cheek. Also it sounds like Dr. Murphy might have recognized that the guy had a medical condition if he suddenly lost consciousness, so maybe he recognized that the attacker might not have been in a sound frame of mind to begin with.

A man attacked Dr. Murphy in a bar, and suddenly lost consciousness. Despite no longer being employed by the hospital, Dr. Murphy does his best to help the attacker, including attempting to inform others what his medical issue is (his failure Makes Sense in Context).