Albuterol does have the effect of lowering potassium.  While one treatment can lower potassium in your system, it's usually by an insignificant amount.  However, if you are using a lot of Ventolin throughout the course of a day, it can have the effect of lowering potassium.  It's generally not something that's considered significant, however.  I have never heard of a physician not prescribing an asthma rescue medicine due to it's potassium lowering effect.  However, it's something to consider if you have other medical problems.  It may also be a good idea to eat a banana or two if you use Ventolin a lot, because bananas are a good source of potassium.  Maybe that's why I crave a banana for breakfast every day because I used to use Ventolin a lot.  Anyway, here is a good article written by a good friend of mine that answers your question in more detail if you're interested.  I actually wrote a post on the subject myself but it's location presently eludes me.