Oh, and every now and then the severed vas defrens tube can get caught in the scrotal stitching. You'll realize this predicament when you try to stand and you feel a tugging in your intestinal area. This happened to a friend of mine. He went back to see the doc. Doc examines him, says stand up, face away and hold onto the door frame. A quick, from behind, tug on the old sack and all was well. After several minutes of recovery my friend said, "why didn't you tell me you were going to do that?" Of course the doc told him, "If I'd told you, you wouldn't have let me do it!"
But that's probably even more rare than not enough anesthesia. I wouldn't worry about that.