Although the majority of the patients receiving dexmedetomidine required rescue sedations with thiamylal , the respiratory disturbance index ( RDI ) defined as the total number of sleep-disordered breathing events divided by the recording time ( 10.4 5.1 vs. 18.2 8.1 events/h ; P < 0.0001 ) and movement index defined as the number of body movement events per hour ( 7.6 6.1 vs. 11.0 5.5 events/h ; P = 0.0098 ) were both significantly lower in the dexmedetomidine arm than in the thiamylal arm .