Alpha-2 agonists were supposed to allow lighter sedation and earlier extubation. In the first trial to compare all three agents head to head, neither beat propofol, and both brought more agitation and bradycardia.
The medians look shorter for the alpha-2 arms, but the confidence intervals overlap and neither hazard ratio excludes no difference. Successful extubation = extubation followed by 48 hours without mechanical ventilation.
| Outcome vs propofol | Dexmedetomidine | Clonidine |
|---|---|---|
| Agitation | RR 1.54 (1.21–1.97) | RR 1.55 (1.22–1.97) |
| Severe bradycardia (HR <50) | RR 1.62 (1.36–1.93) | RR 1.58 (1.33–1.88) |
| Delirium, ICU stay, mortality | No significant differences | |
The alpha-2 arms weren't pure. Patients randomized to dexmedetomidine or clonidine still received propofol on more than 75% of ventilator days, at lower doses. The trial tested alpha-2-based sedation with propofol as backup, not alpha-2 agonists alone.
Open-label and pragmatic. Sedation was titrated by algorithm in UK ICUs; patients were expected to need at least 48 hours of ventilation.
This fits the earlier evidence: SPICE III found early dexmedetomidine didn't reduce mortality (see spice-iii-dexmedetomidine). Dexmedetomidine's niche remains specific situations, such as agitation during weaning or avoiding respiratory depression, rather than routine primary sedation.
Propofol stays the default primary sedative for ventilated adults, with light sedation targets. Reach for dexmedetomidine for a reason, and watch heart rate: severe bradycardia was about 60% more common.