Why death row inmate Christa Pike didn't die after two shots of a lethal drug

Tennessee officials were unable to put murderer Christa Pike to death after two doses of pentobarbital, and her lawyers say she is in a critical condition. Pike was 18 when she tortured and killed schoolmate Colleen Slemmer in 1995, and her clemency plea citing childhood trauma was rejected. But why was Christa Pike still breathing after being given the supposedly lethal injections? A medical expert says her veins fell apart and the drug burned her arm. What happens next?