Well, if you are doing hand-held, then yes, you will probably need a higher ISO in order to keep the shutter speed high enough to avoid hand shake.
However, correct night photography, using a tripod, removes hand shake out of the equation, so there is no need to have a quick shutter speed. The camera is on a tripod, so you can leave the shutter open for 30 seconds, a minute, 10 minutes, etc.. whatever is needed to get proper exposure.
The higher the ISO is, the more noise that is introduced into the image. The best night shots that you see, are generally shot with as low of an ISO setting as possible.