Not really, no. At least not a standard buckle belt as, once you pass out, the pressure applied by the belt would be released. In theory, if you had a hole in exactly the right position and were able to get the pin/prong inserted into the hole before passing out, then it may be possible but not without risk.
I do have a belt with a different type of buckle:
This buckle locks into place as the belt start to loosen. However, even this would require additional pressure to be applied before it would lock into position, and also requires further tightening in order to unlock.
One alternative to the ratchet strap is a tourniquet. Check pages 223-224 of Five Last Acts (available for download in the List of Resources - link in my signature).