Quite honestly I've never had the situation arise that I had to intervene. Anytime one of them got a less than perfect hold on the rat, before the rat could really do any damage, it was dead. Realistically in most cases the constriction is so quick and so completely overwhelming to the rat's system that they just aren't doing much biting and chewing on a snake. You tend to see more problems when a snake isn't hunting a rodent and the rodent is improperly left in the enclosure live for extended periods of time, without food, etc. and goes after the snake or if the rodent is far, far too big for the snake so the snake can't get good and fast control of it.