You can channel healing energy in response to an attack that would knock you unconscious.
Benefit: When the damage from an attack or an effect would reduce you to 0 or fewer hit points, you can expend one use of channel energy (of a form that would heal you) or lay on hands as an immediate action to heal yourself. The healing affects only you, even if it would normally affect others.
Pathfinder Roleplaying Game: Advanced Class Guide © 2014, Paizo Inc.; Authors: Dennis Baker, Ross Byers, Jesse Benner, Savannah Broadway, Jason Bulmahn, Jim Groves, Tim Hitchcock, Tracy Hurley, Jonathan H. Keith, Will McCardell, Dale C. McCoy, Jr., Tom Phillips, Stephen Radney-MacFarland, Thomas M. Reid, Sean K Reynolds, Tork Shaw, Owen K.C. Stephens, and Russ Taylor.