"Not to be a smartazz, Greg, but what kind of fridge have you got, that requires ice packs to keep things colder?"
Cheri,
OK here is a smartazz answer anyway.
I don't have a fridge right now but as someone who has written some things about how to keep things cool/cold when there is no electricity (or gas in some cases) there are a few simple rules when you don't have electricity;
Don't open the thing up unless you need to - you will be surprised how many people open a fridge because they are bored.
Keep the thing filled, even if it is with ice packs or ice cubes. The mass of the stuff keeps the temp from rising quicker than an empty fridge, the ice packs/ice cubes are frozen mass and helps a lot.
Unplug the thing (this is for the home fridge) because when the electricy comes on, so does a nice surge and sometimes there is a brown out condition that will fry the compressor (this is what happened to my fridge in the truck).
Also not to be a smartazz, but the subject is defrosting (or warming) of the fridge while not driving, so back to it is simple things that count. these rules keep things cold for a few hours at a time - saving fuel.