Some editions of the game (3rd and 4th) try to solve this problem by allowing characters to make a save against such an effect each round. It might not be a bad idea, but it also lessens the power of ghouls, plus there is a lot of extra rolls involved.
Justin over The Alexandrian offers a different solution: he proposes that these attacks deal ability damage instead, both extending the generally ablative nature of combat to such situations and maintaining their seriousness (1d6 or 2d6 temporary damage to an ability may not be lethal, but a couple others have a great chance of debilitating your character; thanks to dice rolling, it varies a lot). My problem with this variant is that one is required to keep several totals of damage: one for HP and possibly one for each ability.
In -C's On the Non-player Character, social combat is resolved through regular attacks dealing subdual damage and checking its total against the target's HP to determine whether it has a minor, major, or no effect on the target.
This system could be used for paralysis (or actually any other "save-or-die" effect). A successful attack and a failed saving throw would result in the accumulation of subdual damage (probably 1d8 for B/X and 1d6 for 0e types of games); the minor effect could be along the lines of the shaken condition (-2 to attack rolls), while the major effect would be ye olde paralysis. If neither effect would be triggered, the paralysis damage would convert to standard non-lethal damage, as usual.
Also, one could eliminate the need for a saving throw by penalising such attacks with -4 as other types of non-lethal attacks; the target's AC could be (10 - 1/2 HD - Con modifier). This way, ghouls would have the option of attacking regularly or trying to paralyse the characters, if different types of attacks are your thing.