You certainly couldn't call Vampire Gordon's death a clean one. There was no nicely honed machete in Sam's hands.

Dean's favorite knife lay loose on the floor, dusty perhaps but undeniably free of possible bloodstains.

Sam worked in the dark, driven by rage and the gleam of Gordon's teeth. The blood poured from his nose. He didn't even know where his empty hands found the wire.

In the end the barbed wire functioned as an excellent garrote. Ignoring the slashes to his hands Sam gloried in his anger and squeezed and squeezed until Gordon's head was rolling on the floor.