In this March 2, 2010 photo, U.S. Army Task Force Pegasus flight medic Sgt. Nathaniel Dabney closes the door of a medevac helicopter in preparation for takeoff, after loading aboard a wounded U.S. Marine, during an ongoing firefight, in Helmand province, Afghanistan. (AP Photo/Brennan Linsley)AP - The number of U.S. troops killed in Afghanistan has roughly doubled in the first three months of 2010 compared to the same period last year as Washington has added tens of thousands of additional soldiers to reverse the Taliban's momentum.