By Dr. Jeff Nichol/For the Journal   Fourth in a series. I offered to help Placitas pet parents with their poisoning problem and, well, they took me up on it. The next morning, Gretel, a big hound I already knew, lumbered listlessly through the door. I almost didn't recognize her. Her gums were pale; her respiratory rate increased. A quick check of her blood showed a serious. but not-yet life-threatening. anemia. She'd been allowed to roam loose. This dog was going to make it – if we moved fast enough. I gave the antidote for diphacinone poisoning, vitamin K1, by...