Adults with ARF and within @ h of starting NIV were randomized to receive IV dexmedetomidine ( @ g/kg/h titrated every @ min to @ g/kg/h to maintain a Sedation-Agitation Scale -LSB- SAS -RSB- score of @ to @ ) or placebo in a double-blind fashion up to @ h , until NIV was stopped for @ h , or until intubation .