Sedate means to be calm, but if a doctor sedates you it means you've been administered a tranquilizing drug. Most surgeries require some form of sedation, but to be sedate in day-to-day life means composed, quiet, and serene. Not necessarily unconscious.
To be sedate when dining with the Queen means that you behaved with dignity and solemnity. To be sedated when dining with the Queen means that you were face down in the bread pudding and drooling onto the tablecloth. The medical sense of the word is to be tranquilized, either to calm your nerves after a shock or in preparation for surgery. Socially, to be sedate is to be serene, quiet, and composed.