Choice of sedation of critically ill patients is a core element of intensive care practice. The alpha 2 agonists for sedation to produce better outcomes from critical illness (A2B) trial tested the effectiveness of two alpha agonist sedatives versus propofol in reducing time on mechanical ventilation in 38 intensive care units in the United Kingdom. To evaluate both how this complex trial was implemented and how this may have influenced trial outcomes, an understanding of the contextual and practice variation across multiple sites was required.
