Table 1 Description of the characteristics of the included randomized controlled trials

Duffett et al., 2014

Mechanically ventilated children 1 month to 18 years old

n = 25 Clonidine 5 μg/kg enteral (max 200 μg) q6h

Adjunctive (Midazolam, morphine equivalents)

n = 25 Placebo

Level of sedation (COMFORT or State Behavioural scales), dose of sedative agents (midazolam and morphine equivalents), duration of mechanical ventilation, length of PICU/hospital stay, adverse events

Farasatinasab et a.l, 2015

Mechanically ventilated adults

n = 30 Clonidine 0.1–0.2 mg enteral q8h

Adjunctive (Midazolam, morphine equivalents, propofol)

n = 25 Placebo

Level of sedation (Ramsay Sedation Score), dose of sedative agents (midazolam and morphine equivalents), total amount of sedation used, adverse events

Hünseler et al., 2014

Mechanically ventilated newborns and children 0 days to 2 years old. The newborn subgroup was excluded in data analysis

n = 105 Clonidine 1 μg/kg/hr infusion

Adjunctive (Midazolam, fentanyl, thiopentone prn)

n = 114 Placebo

Level of sedation (Hartwig and COMFORT scores), dose of sedative agents (fentanyl and midazolam), duration of mechanical ventilation, length of ICU stay, mortality

Rubino et al., 2009

Mechanically ventilated adults who had undergone surgical correction of acute type A aortic dissection

n = 15 Clonidine 0.5 μg/kg intravenous bolus, then 1–2 μg/kg /hr infusion

Adjunctive (Fentanyl, propofol)

n = 15 Placebo

Incidence of delirium, severity of delirium (Delirium Detection Score), duration of weaning, length of ICU stay

Spies et al., 1996

Mechanically ventilated post-trauma surgery adults who were alcohol-dependent

n = 54 Clonidine 0.3 mg intravenous bolus, then up to 0.88 μg/kg/hr infusion and flunitrazepam 4 mg intravenous bolus, then up to 19 μg/kg/hr infusion

Adjunctive (Flunitrazepam)

(1) n = 50 Chlormethiazole 375 mg intravenous bolus, then up to 8.2 mg/kg/hr infusion and haloperidol 20 mg intravenous, then up to 53 μg/kg/hr infusion. (2) n = 55 Flunitrazepam 6 mg intravenous bolus, then up to 28 μg/kg/hr infusion and haloperidol 20 mg intravenous bolus, then up to 87 μg/kg/hr infusion

Length of ICU stay, incidence of alcohol withdrawal syndrome (revised clinical institute withdrawal assessment for alcohol scale), adverse events

Srivastava et al., 2014

Mechanically ventilated adults

n = 35 Clonidine 1–2 μg/kg/hr infusion

Stand-alone

n = 35 Dexmedetomidine 0.7 μg/kg intravenous bolus, then 0.2–0.7 μg/kg/hr infusion

Level of sedation (Ramsay sedation score), dose of sedative agents (diazepam, dexmedetomidine, fentanyl), hemodynamic changes, adverse events

Wolf et al., 2014

Mechanically ventilated children age 30 days to 15 years

n = 61 Clonidine 3 μg/kg intravenous bolus, then 0–3 μg /kg/hr infusion

Adjunctive (Midazolam, morphine)

n = 59 Midazolam 200 μg/kg intravenous bolus, then 0–20 μg/kg/hr infusion

Level of sedation (COMFORT score), time spent adequately sedated, duration of sedation, adverse events, length of ICU/hospital stay, ICU mortality

Molon et al., 2007

Mechanically ventilated children (age criteria unspecified)

n = 31 Clonidine 5 μg/kg intravenous q8h

Adjunctive (Midazolam, morphine)

n = 38 Placebo

Dose of sedatives (midazolam and morphine), duration of sedation, incidence of withdrawal syndrome (Finnegan score)