In a article about the social media value for healthcare conferences Audan from Symplur explaines some great measurements and poses some great questions.
In the comments he answers to my comment with some extra angles on the setting.
It is truly an incredibly achievement to create such a social media impact even without available of WiFi!
Putting TEDxMaastricht into perspective with another conference with a similar record social media impact, #himss12, can bring additional insights into the magnitude of the value.
#himss12 had similar record peak tweet volume day of about 6,500 as did #TEDxMaastricht. But they had around 37,000 physical attendees, vs your 900!
In other words, with 40 times fewer physical participants, you managed to accomplish comparable healthcare social media impact.