Fig. 8. Various possibilities for combined spinal–epidural block failure caused by incorrect technique. (A ) Length of spinal needle is too short or epidural needle is not far enough into the epidural space. (B ) Spinal needle “tents” the dura without puncture (possibly greater risk with pencil-point needles). (C ) Epidural needle deviated from midline. (D ) Correct technique with successful dural puncture. (Reprinted with permission. 130)