How long would a sleep med stay in a childs system would it give me enough time to take him to a dr. to draw blood and find out if this is happening?

Don't drug: Unless your child is under what we call deep sedation or general anesthesia, no med is going to make him oblivious to the fact you are sticking a needle in his arm. As soon as tourniquet goes on, he or she is going to wake up and put up whatever fight they would put up unmedicated. You are really only trying to make yourself feel better. Tell yourself this is for their well-being, and then do it.