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Clinical Trial
. 2025 Jul 1;334(1):32-45.
doi: 10.1001/jama.2025.7200.

Dexmedetomidine- or Clonidine-Based Sedation Compared With Propofol in Critically Ill Patients: The A2B Randomized Clinical Trial

Timothy S Walsh  1 , Richard A Parker  2 , Leanne M Aitken  3 , Cathrine A McKenzie  4   5 , Lydia Emerson  3 , Julia Boyd  2 , Alix Macdonald  2 , Gayle Beveridge  2 , Annabel Giddings  2 , David Hope  6 , Sîan Irvine  2 , Sharon Tuck  2 , Nazir I Lone  1 , Kalliopi Kydonaki  7   8 , John Norrie  2 , David Brealey  9   10 , David Antcliffe  11 , Michael Reay  12 , Alan Williams  13 , Jeremy Bewley  14 , Benedict Creagh-Brown  15 , Daniel F McAuley  16 , Paul Dark  17 , Matt P Wise  18 , Anthony C Gordon  19 , Gavin D Perkins  20 , Michael C Reade  21 , Bronagh Blackwood  16 , Alasdair MacLullich  22 , Robert Glen  23 , Valerie J Page  24 , Christopher J Weir  2 ; A2B Trial Investigators
Collaborators, Affiliations
Clinical Trial

Dexmedetomidine- or Clonidine-Based Sedation Compared With Propofol in Critically Ill Patients: The A2B Randomized Clinical Trial

Timothy S Walsh et al. JAMA. .

Abstract

Importance: Whether α2-adrenergic receptor agonist-based sedation, compared with propofol-based sedation, reduces time to extubation in patients receiving mechanical ventilation in the intensive care unit (ICU) is uncertain.

Objective: To evaluate whether dexmedetomidine- or clonidine-based sedation reduces duration of mechanical ventilation compared with propofol-based sedation (usual care).

Design, setting, and participants: Pragmatic, open-label randomized clinical trial conducted at 41 ICUs in the UK including adults who were within 48 hours of starting mechanical ventilation, were receiving propofol plus an opioid for sedation and analgesia, and were expected to require mechanical ventilation for 48 hours or longer. The median time from intubation to randomization was 21.0 (IQR, 13.2-31.3) hours. Recruitment occurred from December 2018 to October 2023; the last follow-up occurred on December 10, 2023.

Interventions: The bedside algorithms used targeted a Richmond Agitation-Sedation Scale score of -2 to 1 (unless clinicians requested deeper sedation). The algorithms supported uptitration in the dexmedetomidine- and clonidine-based sedation intervention groups and supported downtitration for propofol-based sedation followed by sedation primarily with the allocated sedation (dexmedetomidine or clonidine). If required, supplemental use of propofol was permitted.

Main outcomes and measures: The primary outcome was time from randomization to successful extubation. The secondary outcomes included mortality, sedation quality, rates of delirium, and cardiovascular adverse events.

Results: Among the 1404 patients in the analysis population (mean age, 59.2 [SD, 14.9] years; 901 [64%] were male; and the mean APACHE II score was 20.3 [SD, 8.2]), the subdistribution hazard ratio (HR) for time to successful extubation was 1.09 (95% CI, 0.96-1.25; P = .20) for dexmedetomidine (n = 457) vs propofol (n = 471) and was 1.05 (95% CI, 0.95-1.17; P = .34) for clonidine (n = 476) vs propofol (n = 471). The median time from randomization to successful extubation was 136 (95% CI, 117-150) hours for dexmedetomidine, 146 (95% CI, 124-168) hours for clonidine, and 162 (95% CI, 136-170) hours for propofol. In the predefined subgroup analyses, there were no interactions with age, sepsis status, median Sequential Organ Failure Assessment score, or median delirium risk score. Among the secondary outcomes, agitation occurred at a higher rate with dexmedetomidine vs propofol (risk ratio [RR], 1.54 [95% CI, 1.21-1.97]) and with clonidine vs propofol (RR, 1.55 [95% CI, 1.22-1.97]). Compared with propofol, the rates of severe bradycardia (heart rate <50/min) were higher with dexmedetomidine (RR, 1.62 [95% CI, 1.36-1.93]) and clonidine (RR, 1.58 [95% CI, 1.33-1.88]). Compared with propofol, mortality was similar over 180 days for dexmedetomidine (HR, 0.98 [95% CI, 0.77-1.24]) and clonidine (HR, 1.04 [95% CI, 0.82-1.31]).

Conclusions and relevance: In critically ill patients, neither dexmedetomidine nor clonidine was superior to propofol in reducing time to successful extubation.

Trial registration: ClinicalTrials.gov Identifier: NCT03653832.

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Conflict of interest statement

Conflict of Interest Disclosures: Dr McKenzie reported receiving a senior clinical practitioner research award from the National Institute for Health and Care Research and receiving personal fees from Pharmaceutical Press for serving as editor in chief of Critical Illness. Dr Lone reported being the director of research and the intensive care society chair for the Scottish Intensive Care Society Audit Group, Public Health Scotland. Dr Norrie reported receiving grants from the University of Edinburgh and serving as chair of the National Institute for Health and Care Research funding committee. Dr Bewley reported serving as a consultant to Bayer PLC. Dr McAuley reported receiving personal fees for serving as a consultant to Bayer, GlaxoSmithKline, Boehringer Ingelheim, Novartis, Eli Lilly, Vir Biotechnology, Aptarion, Aviceda, and Direct Biologics; receiving grants from Wellcome Trust, Innovate UK, Medical Research Council, and the HSC Public Health Agency; having a patent for an anti-inflammatory treatment that was issued to Queen’s University Belfast; and serving as codirector of research for the Intensive Care Society and serving as program director for the National Institute for Health and Care Research/Medical Research Council. Dr Wise reported receiving personal fees from the National Institute for Health and Care Excellence and Diagnostics for the Real World. Dr Gordon reported receiving personal fees from AstraZeneca that were paid to his institution. No other disclosures were reported.

Comment in

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