There were suggestions at one time with the service I was with to limit the pilots knowledge (and this came from the medical side of the service) of why we were going - in practical terms it just doesn't work.
The aircrew had to load the gear, plan for patient and a hundred other things that were useful or required to get the job done. They mostly have a good idea from the way everyone is acting anyway.
In the end we what did what every sensible team should do - communicate everything we knew with everybody and we then left it with the pilot to decide on the final aviation decision.
But you have to look at this subject with real practical true-life eyes. We all, whether an ivory-tower-ite likes it or not, allow the patient at the other end to affect do some degree our decision making. If we didn't we'd stay home every time.
But the reality is if its a sick kid or young multi-trauma we all see the risks as less and the need as greater (and that applies to captains too!)