The next room has six guards in it. The first two are an easy target so just crouch down, sneak up behind them (they'll be right in front of you) and do a double take down. Climb up to a vantage point. At this point, you'll have two enemies wondering around and two in a room in the corner with the doctor. After you get rid of the two outside, one of the two in the room will come out. To get the first two, you can either drop down and sneak up behind him for a silent takedown or you can wait for him to walk under a vantage and do a takedown from there. It shouldn't be a problem to do either because they are fairly far apart. Once they are gone, move to the vantage attached to the room and just wait for the guy in the room to come out. He'll go right under it and you can do an inverted takedown. Swing over to one of the other vantages and you can do a glide kick on the last guy through the window. Just make sure to finish him while he's on the ground. Go over and hit A to free the doctor.