There are lots of LMWHs, and they work on factor Xa and IIa. There's a nice chart on Wikepedia (I know, but it's not important enough to me to chase the link) about the different ratios that they work in. Which is interesting really - I thought they were all pretty similar, but it turns out they are not.
Protamine is used to reverse bleeding from heparin, but also works for the LMWHs.
50mg in 5ml (solution).
Administer by slow IV injection over no greater than 1ml/minute (i.e. 50mg over 5 minutes).
Watch the blood pressure trace closely during administration and slow rate of infusion if the blood pressure drops.
Side effects include anaphylaxis, urticaria and bradycardia.
Protamine provides about 60% neutralisation
Our haematologist said give 1mg per mg of Clexane - another source suggests varying the amount depending on when the Clexane was given.