Goodman Games

When a thief uses a garrote successfully in a sneak attack (gaining a critical hit) I would expect that he has his opponent ensnared.
What does this mean for consecutive rounds? Are there any rules for this/how do you play this?
Is the thief allowed to make additional sneak attacks on that foe (resulting in critical hits if successful)?
A failure might mean that the opponent escaped from the garrote.

I wouldn't allow further backstabs -- the opponent is most definitely aware of the Thief's attack.

Starting the next round under grapple rules sounds reasonable. Hmmm, there's the ensnaring (low-damage) garrote in place, but the target's hands are free. So maybe the opponent could either 1) opposed Str to break free or 2) attack the Thief (between being garotted and the Thief's hands full, we can call that a wash). If the garotte stays put, perhaps something like drowning rules before passing out?

The way I read it, the garotte does 3d4 damage if the attack is a surprise, plus a critical hit roll if the attacker is a thief.

Consecutive rounds are not surprise, so I would rule the base 1 damage per round, assuming that the target is struggling to escape. However, remember that a thief can modify damage using their Luck Die, so second and subsequent rounds could have much higher damage. Also, Strength bonus or penalty applies (in my games, to a minimum of 1 damage).

Remembering that the average person will die due to 3d4 damage, that seems fair to me.