I listened to a lady in one of the meetings talk about her husband who had a seizure after two days of not drinking. She got him to the hospital where he was kept for a couple of days--it wasn't a detox center but just part of the regular hospital. He still drinks heavily and she has come to Al-Anon to help herself gain some sanity.
One of the things that has been stressed to me is the importance of getting to know AA's who are long-timers in the program. And to call upon them should a situation arise in which the alcoholic relapses. The reasoning is that another alcoholic on a Twelfth Step call will know how to deal with someone who has relapsed. In cases where there are family members who are upset, it is good to indicate that as an Al-Anoner, you could ride along and offer E, S, and H to the family of the active alcoholic.
If there is a medical emergency such as the seizure, then timing will be essential. So a 911 call would be necessary but perhaps it could also be appropriate to get in touch with AA once the medical emergency is over and ask them to visit the alcoholic.
I've actually made a mental plan about what I will do should my alcoholic relapse. It's not an easy thing to contemplate but it's best to have a plan rather than a meltdown. It's a tough disease and there are no guarantees.