I just had an interesting thing happen to me. Maybe it is a solution to getting "As A Scalpel". If anyone else can confirm my technique, this little trick might make this achievement much easier. If what happened to me was just a glitch, then I'll remove this solution, and apologize for getting anyone's hopes up.
I'm late in the game playing Ironman on Classic Difficulty. My map ended up being a bridge, and I had one person who has fully ranked up psionic abilities.
I had her move forward until a muton came into view, and she mind-controlled the muton (she had on Psi Armor) with a 100% chance. This muton was surrounded by his fellow aliens, and didn't last long.
The strange thing was that after this muton was mind controlled and killed by his comrades, the aliens no longer tried to kill any civilians. The civilians were running about to and from cover right in front of aliens and were not fired upon.
I finished the mission (with a few more mind controls and subsequent alien deaths) and got this achievement after only losing two civilians.
Final mission stats:
12 Aliens Killed -- Excellent rating
0 XCom Operatives Lost -- Excellent rating
16/18 Civilians Saved -- Excellent rating