Are there any basic safety items one ought to carry, in case of getting bitten by a rattlesnake?

What I've been told before is that "the best rattlesnake safety device is a car key -- get to a hospital as soon as possible" and "don't panic, don't run, keep your heartrate down so that the venom doesn't circulate that far in your body before you get to the hospital." Is it even possibly to calmly and coolly hike back to your car when you've just been bitten by a rattlesnake?

What about a rag to tie off the affected area and cut of circulation there while you hike out? Good idea? Bad idea?

Joel