也就是死马当作活马医嘛：clutch at straws
参考解释：
http://idioms.thefreedictionary.com/clutch+at+straws
1. to try any method, even those that are not likely to succeed, because you are in such a bad situation. He's hoping that this new treatment will help him but I think he's clutching at straws. (usually in continuous tenses)
2. to try to find reasons to feel hopeful about a situation when there is no real cause for hope. She thinks he might still be interested because he calls her now and then but I think she's clutching at straws. (usually in continuous tenses)