Most professional rotorcraft pilots will concerntrate or specialise in a certain type of operation.....Be that EMS, Offshore, Police, Long Lining etc.
The depths of capacity will deepen once that pilot has reached a certain level of role specific knowledge and experience. However there are the hard rules that govern us all...and these have been written with safety as the essence.
There are many aspects that govern each and ever flight.....Weather, PUS, Fuel, FDTL etc......and of course client pressure.
The health of any passenger [Patient] is just one of the aspects that must be considered...just one of many.
There are certain rules that can be challenged, and if justified, then acted against, the guidelines for this action is outlined in Jeppesen Air Traffic Control, AU-1101 [Mercy Flights]. Part of this "Mercy Fight" declaration is that the PIC must be convinced that the non compliance with any rule can be substainiated in a Court of Law. Therefore he must "Test" the sincerity of the medical request, and be positive that it is legitamate, and his/her decision is defendable.
The only decision regarding the actual flight belongs with you...and you alone.