The medevac pilot not wanting to climb to 2000 feet could be related to the patient. I know our crews where I work, if the patient is on a balloon pump, they try to stay within 1000 feet of sending hospital (where the balloon pump is "installed"). It is my understanding that the higher altitude changes are possible, but the balloon pump machine will sound an alarm and the med crew may have to either re-program the balloon pressure or something along those lines (not a medical professional myself).
Balloon pump is a helium balloon inserted thru a leg artery and run up into the aorta to help the heart pump blood after a cardiac event or heart surgery.