Impacts of Low-Dose Dexmedetomidine on Sleep Quality in Mechanically Ventilated ICU Patients
Impacts of Low-Dose Dexmedetomidine on Sleep Quality in Mechanically Ventilated ICU Patients
Sleep disturbances frequently occur in intensive care unit (ICU) patients undergoing
 mechanical ventilation. In a previous study, sedative dose dexmedetomidine (median 0.6
 microgram/kg/h) improved sleep quality in mechanically ventilated patients. However, for
 mechanically ventilated patients, light sedation is better than deep sedation for the
 outcomes, which is manifested as shortened length of ICU stay, shortened duration of
 mechanical ventilation, and decreased mortality. In a recent study of the investigators,
 non-sedative low-dose dexmedetomidine (0.1 microgram/kg/h) improved sleep quality in
 non-mechanically ventilated elderly patients admitted to the ICU after surgery. The
 investigators hypothesize that, in mechanically ventilated patients who are admitted to the
 ICU after surgery, low-dose dexmedetomidine may also improve sleep quality.
Sleep is severely disturbed in mechanically ventilated ICU patients, especially those after
 surgery. Polysomnographic studies performed in these patients demonstrated a severe increase
 in sleep fragmentation, prolonged N1 and N2 sleep, reduced N3 and REM sleep, and an abnormal
 distribution of sleep because almost half of the total sleep time occurred during the
 daytime. Patients reported little or no sleep, poor sleep quality, frequent awakening, and
 daytime sleep.

 Many factors are responsible for sleep disturbance in postoperative ICU patients with
 mechanical ventilation, these include the severity of surgical stress and illness, ICU
 environment, mechanical ventilation, pain, sedatives and analgesics, and various other
 therapy. Sleep disturbances produce harmful effects on postoperative outcomes. It is
 associated with increased prevalence of delirium, cardiac events and worse functional
 recovery. Moreover, patients with sleep disturbances are more sensitive to pain.

 Unlike other sedative agents, dexmedetomidine exerts its sedative effects through an
 endogenous sleep-promoting pathway and produces a N2 sleep-like state. In mechanically
 ventilated ICU patients, nighttime infusion of sedative dose of dexmedetomidine (median 0.6
 microgram/kg/h) preserved the day-night cycle of sleep and improved the sleep architecture by
 increasing sleep efficiency and stage N2 sleep.

 Studies showed that, in mechanically ventilated patients, light sedation is better than deep
 sedation for patients' outcomes, including shortened duration of ventilation and length of
 ICU stay, and decreased mortality. Some studies even showed that no sedation (analgesia only)
 is better than sedation. In a recent study of non mechanical ventilated elderly patients who
 were admitted to the ICU after surgery, non-sedative low-dose dexmedetomidine infusion (at a
 rate of 0.1 microgram/kg/h during the night on the day of surgery) increased the percentage
 of stage N2 sleep (and decreased the percentage of N1 sleep), prolonged the total sleep time,
 increased the sleep efficiency, and improved the subjective sleep quality.

 The investigators hypothesize that, in mechanically ventilated patients who were admitted to
 the ICU after surgery, low-dose dexmedetomidine infusion may also improve sleep quality.
Inclusion Criteria:

 -  aged 18 years or older;

 -  admitted to the ICU after surgery;

 -  with an expected duration of mechanical ventilation of more than 12 hours (admitted
 before 21:00 on the day of surgery and extubated after 06:00 on the first day after
 surgery).

 Exclusion Criteria:

 -  refused to participate;

 -  aged less than 18 years;

 -  pregnant;

 -  preoperative history of schizophrenia, epilepsy, parkinsonism, or myasthenia gravis;

 -  inability to communicate in the preoperative period (coma, profound dementia, or
 language barrier);

 -  brain injury or neurosurgery;

 -  known preoperative left ventricular ejection fraction less than 30%, sick sinus
 syndrome, severe sinus bradycardia (<50 beats per min), or second degree or greater
 atrioventricular block without pacemaker, systolic blood pressure less than 90 mmHg
 despite continuous infusions of vasopressors before the start of study drugs infusion;

 -  serious hepatic dysfunction (Child-Pugh class C);

 -  serious renal dysfunction (undergoing dialysis before surgery);

 -  less likelihood to survive for more than 24 hours;

 -  preoperative history of sleep disorders (requirement of hypnotics/sedatives during the
 last month) or history of obstructive sleep apnea syndrome (diagnosed with obstructive
 sleep apnea);

 -  allergy to the study drugs;

 -  other conditions that are considered unsuitable for study participation.