Low dose dexmedetomidine for the prophylaxis of perioperative ICU delirium—how much evidence is enough?

Few clinical trials in critical care medicine suggest clinicians should do something most would not have previously considered. The recently published randomised, placebo-controlled, 2-hospital blinded study of low dose, non-titrated dexmedetomidine in 700 elective surgical patients >65 years old admitted to an intensive care unit in the immediate postoperative period (1) is such a trial. Su et al. showed dexmedetomidine 0.1 mcg/kg/hr (a very low dose, well below that used for sedation in most patients) from the time of ICU admission to 8 am on the first postoperative day was associated with a reduction in the incidence of postoperative delirium of >50% (from 23% to 9%, P<0.0001), along with universally congruent benefit in secondary outcomes such as subjective sleep quality and pain, daily prevalence of delirium on days 1–3, time to extubation (in the approximately 50% of patients who were intubated at the time of randomisation), and length of ICU stay, all without any observable increase in bradycardia or hypotension, adverse effects related to dexmedetomidine at higher doses.