Despite at least 90 trials comparing sedative regimens,17
in general, no sedative drug is clearly
superior to all others. Sedatives that are commonly used in the ICU are the benzodiazepines
midazolam and lorazepam (and to a lesser extent,
diazepam), the short-acting intravenous anesthetic
agent propofol, and dexmedetomidine.12
Remifentanil, an opioid, is also used as a sole
agent because of its sedative effects. Benzodiazepines
act through γ-aminobutyric acid type A
(GABAa) receptors, as in part does propofol,
whereas dexmedetomidine is an α2-adrenoceptor
agonist, and remifentanil is a μ-opioid receptor
agonist (Table 1). Marked differences in prescribing
patterns among countries suggest that the
choice of agent is determined more by tradition
and familiarity than by evidence-based practice.