I'm confident I'll be corrected.... and I cannot find a printed source. I asked a friend here who is a Hemotologist considered the regional expert on venom (snake and spiders, here. For what it is worth, here goes:

Aside from the above issue of whether or not to use suction to extract venom (mouth, Sawyer, or heated bottle) the actual issue is that none of these methods actually DO anything. Venom transports so rapidly that any remnant still extractable by suction at the bite site is irrelevant in seconds. One of the mysteries being investigated is that the venom seems to transit faster than one can explain by venous activity per se. So you can't "remove" it.

You can counter the effects with antivenom, and/or you can stabilize and medically support the patient. But if anyone can cite a good reference showing that any significant amount of venom can be removed by ANY form of suction, I'd like to read it.