Nocturnal administration of dexmedetomidine (0.2-1.0 mcg/kg/h) during the first night after surgery. Dexmedetomidine infusion, not preceded by a bolus administration, will be started at 0.4 mcg/kg/h in the intervention group at 8 p.m. the day of surgery. Dexmedetomidine infusion will be titrated every 30 minutes with 0.1 mcg/kg/h steps until a RASS of -1 to -3 (drowsy, light to moderate sedation) is reached. The infusion will be discontinued at 6 a.m. the next morning.

To assess general fatigue a fatigue questionnaire, the Chalder fatigue questionnaire, will be taken on day 1, day 3, day 5 and day 28 postoperatively and be compared to the preoperative value. The questionnaire consists of 11 items that assess both physical and mental aspects of fatigue. Respondents rate each item ranging from 0 to 3, the scores are then totaled to provide a measure of overall fatigue, a higher score meaning more severe fatigue.

The EQ-5D is used for measuring health-related quality of life. EQ-5D provides a simple descriptive profile and a single index value for health status, both can be used to assess the overall health. The descriptive profile consists of five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each dimension has 5 levels of severity: no problems, slight problems, moderate problems, severe problems, or not able. Respondents select the level that best describes their current health status. The EQ-5D also includes a visual analog scale (VAS) where respondents rate their current health status on a scale from 0 to 100, with 0 being the worst imaginable health state and 100 being the best imaginable health state. The EQ-5D questionnaire will be taken preoperatively and on day 28 postoperatively.

To assess subjective sleep quality over a one-month time interval the Pittsburgh Sleep Quality Index (PSQI) will be used. The PSQI consists of 19 items that assess different components of sleep, including sleep latency, sleep duration, sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction due to poor sleep quality. Each item is rated on a scale from 0 to 3, with higher scores indicating worse sleep quality. The scores from all 19 items are summed to provide a total score ranging from 0 tot 21, with higher scores indicating poorer sleep quality. The questionnaire will be filled in two times: 3 days before surgery and 28 days after surgery.

To assess fatigue in detail, the fatigue visual analog scale (VAS) will be taken on day 1, day 3, day 5 and day 28 postoperatively and be compared to the preoperative value. The VAS is a tool to measure the severity of fatigue subjectively experienced by individuals. It involves a simple assessment where respondents score their fatigue on a series of questions, with 0 representing "no fatigue" and 10 representing "worst possible fatigue".

The Richards-Campbell Sleep Questionnaire (RCSQ) will be taken on day 1 to evaluate the subjective quality of the first night after surgery. The RCSQ consists of a series of questions (five items) that ask individuals to rate various aspects of their sleep experience. Respondents rate each item on a visual analog scale, higher scores indicating worse sleep quality.

To assess postoperative delirium the 3 minute confusion assessment method (3D-CAM) questionnaire will be done on day 1, day 3 and day 5 postoperatively. The 3D-CAM consists of a structured interview and cognitive testing. Based on the patient's responses and performance, it is determined whether delirium is present or not.

To assess postoperative cognitive impairment the Telephone Interview for Cognitive Status (TICS-40) will be done preoperatively and on day 28 postoperatively, this interview is a valid alternative for the Mini-Mental State Examination with the advantage that it does not have to be administered face-to-face. The TICS-40 is compromised of 9 items that result in a maximum score of 40, with higher scores indicating better cognitive function.

Quality of Recovery Score (QoR-15 score) is a patient-reported outcome measurement which will be used to assess the early postoperative health status of the patient after surgery and anesthesia, i.e. the quality of recovery. The score is arbitrary and ranges from 0 to 150, the higher the score the better the quality of recovery. The QoR-15 will be assessed on day 3 and day 5 (if the patient is still in the hospital) as compared to preoperatively.

Postoperative muscle strength (upper extremity) will be assessed by comparing the handgrip strength of the dominant hand, measured on day 1, day 3 and day 5 following surgery as compared to the preoperative value. The test will only be performed if the patient is still in the hospital.

Postoperative muscle strength (lower extremity) and physical ability will be assessed by the Timed Up and Go (TUG) test, on day 3 and day 5 following surgery as compared to the preoperative value. The test will only be performed if the patient is still in the hospital.

Electroencephalographic (EEG) readings will be conducted during the first postoperative night (when administering study medication) to asses sleep architecture.