Does the FAA have specific Air Ambulance safety guidelines?
Check out this document published by the FAA which seems to be recent and some notes here on the same topics. The full rules can be found in the FAR at Part 135 Subpart L—Helicopter Air Ambulance Equipment, Operations, and Training Requirements

They are required to do a preflight risk analysis as per §135.617 but this is not really any different than what anyone should be doing before any flight however for them it is very specifically outlined. 


  (a) Each certificate holder conducting helicopter air ambulance operations must establish, and document in its operations manual, an
  FAA-approved preflight risk analysis that includes at least the
  following—
  
  (1) Flight considerations, to include obstacles and terrain along the
  planned route of flight, landing zone conditions, and fuel
  requirements;
  
  (2) Human factors, such as crew fatigue, life events, and other
  stressors;
  
  (3) Weather, including departure, en route, destination, and
  forecasted;
  
  (4) A procedure for determining whether another helicopter air
  ambulance operator has refused or rejected a flight request; and
  
  (5) Strategies and procedures for mitigating identified risks,
  including procedures for obtaining and documenting approval of the
  certificate holder's management personnel to release a flight when a
  risk exceeds a level predetermined by the certificate holder.
  
  (b) Each certificate holder must develop a preflight risk analysis
  worksheet to include, at a minimum, the items in paragraph (a) of this
  section.
  
  (c) Prior to the first leg of each helicopter air ambulance operation,
  the pilot in command must conduct a preflight risk analysis and
  complete the preflight risk analysis worksheet in accordance with the
  certificate holder's FAA-approved procedures. The pilot in command
  must sign the preflight risk analysis worksheet and specify the date
  and time it was completed.
  
  (d) The certificate holder must retain the original or a copy of each
  completed preflight risk analysis worksheet at a location specified in
  its operations manual for at least 90 days from the date of the
  operation.