Slight revision...
Rapid Blood Drain (Ex): A greater vampire can rapidly suck blood from a living victim with its fangs by making a successful grapple check. If it pins the foe, it drains blood, dealing 1d4 points of Strength, Dexterity, and Constitution drain each round the pin is maintained. On each such successful attack, the greater vampire gains 5 temporary hit points.
This rapid blood drain may cause additional effects. The victim is allowed a Fortitude save against these additional effects (the save DC is Charisma-based). These effects are cumulative and stack (where possible) for the greater types of vampires. For example, a victim that fails a save against an arch-prince's rapid blood drain would be dazed, exhausted staggered, and nauseated (but not fatigued, since exhausted is a greater form of fatigue).
Lord: dazed for 1 round
Arch-lord: fatigued
Princeling: exhausted
Prince: staggered for 1d6 rounds
Arch-Prince: nauseated for 1d6 rounds