Sno fell to the ground 18 minutes after coming on as a half-time substitute in Monday's game and was treated on the pitch for more than 10 minutes before finally coming round.
"He looked surprised to see all those people there," added Van der Dussen. "I don't think he realised what was going on but everyone was greatly relieved.
"The ambulance crew then took over and took him to hospital."
The Netherlands Under-21 player - who began his career with Feyenoord, before a loan spell with NAC Breda and two years with Celtic - spent most of the 2009/10 season on loan at Bristol City before returning to Amsterdam to push for a place in the Ajax first team.
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