To compare the sedative effects of dexmedetomidine and propofol in critically ill adults undergoing mechanical ventilation in the prehospital setting. The effects of two drugs on hemodynamic parameters were evaluated, and the correlation between bispectral index(BIS)and Ramsay sedation score(RSS)was observed.

Sixty hemodynamically stable patients requiring sedation and mechanical ventilation in the prehospital setting were prospectively randomized into two groups. Group A received a loading dose of dexmedetomidine(1 μg/kg)for more than 10 min, followed by a maintenance infusion of 0.5 μg·kg^-1·h^-1 (0.2~0.7 μg·kg^-1·h^-1). Group B was given a loading dose of propofol(1 mg/kg)for more than 5 min, followed by a maintenance infusion of 2 mg·kg^-1·h^-1(1~3 mg·kg^-1·h^-1). All patients were treated with fentanyl 1 μg/kg before the study drug. Hemodynamic parameters were monitored at the emergency scene and on admission, and their sedation level(using RSS and BIS) was monitored. Ramsay scores were compared with BIS mean values.

The dexmedetomidine group had a significant decrease in heart rate during sedation, while the propofol group had a decrease in mean arterial pressure(MAP)during sedation. There was a good correlation between Ramsay score and BIS value.

Dexmedetomidine can reduce heart rate and propofol can transiently affect mean arterial pressure. Both drugs are able to achieve adequate sedation, and there is a good correlation between Ramsay scores and BIS values. BIS surveillance is supported in assessing the applicability of sedation monitoring in prehospital emergency tracheal intubated patients with severe disease.