Table 1 The characteristics of the included studies
Study | Country | Design | Group | Anaesthetic type | Surgical procedure | Grade of ASA | Age range (years) | Control | Anaesthesia depth monitoring | Strategy of DEX | Cognitive problem | Assessment |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Wu et al. [18] | China | 2-arm RCT | DEX48 Control 48 | General anaesthesia | Endoscopic sinus surgery | ASA I–II | 20–30 | NS | BIS | Load dose 0.5 μg kg − 1 over 10 min, followed by maintenance dose 0.2 ug /kg/ h | POD | NI |
Shi et al. [16] | China | 2-arm RCT | 53/53 | General anaesthesia | Thoracoscopic lobectomy with OLV | II -III |  ≥ 65 | NS | BIS | 0.5 µg/kg/h DEX intravenously from anaesthesia induction until chest closure | POD/POCD | CAM/comprehensive test scale |
Tang et al. [15] | China | 3-arm RCT | 80/40 | General anaesthesia | Hepatic lobectomy | II ~ III | 60 ~ 80 | NS | BIS | After anaesthesia induction, dexmedetomidine [0.3 μg/(kg·h)] in the Dex1 group, and dexmedetomidine [0.6 μg/(kg·h)] in the Dex2 group were infused until the end of operation | POD/POCD | CAM/MMSE |
Cheng et al. [20] | China | 2-arm RCT | 23/22 | General anaesthesia + modified intercostal nerve block | Single-port thoracoscopic surgery | II -III | 18–75 | NS | NI | An initial loading dose (0.4 μg/kg) was given for 15 min before the induction of anaesthesia, followed by a maintenance infusion of 0.4 μg/kg/h that was stopped 30 min before the end of surgery | POD | NI |
Mishina et al. [30] | Japan | 2-arm RCT | 99/97 | Local anaesthesia | Inguinal hernia repair | NI | 20–85 | midazolam | OAA/S | NI | POD | NI |
Hu et al. [22] | China | 2-arm RCT | 77/75 | General anaesthesia | Open transthoracic oesophagectomy | I–III | 60–80 | NS | BIS | A loading dose of dexmedetomidine, 0.4 ml /kg, bolus was administered over 15 min immediately prior to induction of anaesthesia, followed by a maintenance dexmedetomidine infusion of 0.1 ml/ kg/h until 1 h before the anticipated end of surgery | POD | CAM |
Liu et al. [26] | China | 4-arm RCT | 99/98 | General anaesthesia | Total hip joint or knee joint or shoulder joint replacement surgery | II–III | 65–80 | NS | BIS | A continuous infusion of DEX at 0.2–0.4 µg/kg/h, without an initial dose, was administered throughout the duration of the surgery | POD | CAM |
Lu et al. [27] | China | 2-arm RCT | 344/331 | General anaesthesia | Elective abdominal surgery | ASA I–III | 60 +  | NS | BIS | A loading dose of 0.5 μg/kg over 15 min followed by a maintenance dose of 0.2 μg/kg per hour) | POD | CAM |
Liu et al. [25] | China | 2-arm RCT | 60/60 | General anaesthesia | Oral and maxillofacial surgery | I–II | 65 +  | NS | BIS | At a dosage of 0.5 μg/kg for 10 min before anaesthesia induction, followed by continuous infusion at a rate of 0.4 μg/kg/h until half an hour before the end of surgery | POD | CAM |
Wu et al. [33] | China | 2-arm RCT | 30/30 | General anaesthesia | Thoracoscopic surgery | I–III | NI | NS | BIS | Receiving 0.5 μg/kg/h DEX infusion throughout surgery | POD | NI |
Zhang et al. [35] | China | 2-arm RCT | DEX120 Control 120 | Subarachnoid block/Combined spinal–epidural anaesthesia/General anaesthesia | Hip fracture | I–III | 65–90 | NS | NR | (0.5 mg/kg/h) 30 min before the start of anaesthesia,and 0.3 mg/kg/h during the operation | POD | CAM |
Xin et al. [34] | China | 2-arm RCT | DEX30 Control 30 | General anaesthesia | Laparoscopic cholecystectomy | II or III | 65 +  | NS | BIS | As a loading dose, 0.5 μg/kg dexmedetomidine was administered over 10 min before anaesthesia induction, which was then administered as a continuous intravenous infusion at a dose of 0.4 μg/kg/h until 30 min before the end of surgery | POD | 3D-CAM |
Mei et al. [28] | China | 2-arm RCT | DEX148 Control 148 | Lumbosacral plexus plus T12 paravertebral block | Hip arthroplasty | I–IV | 65 +  | propofol | BIS | Loading dose of DEX0.8–1 μg/kg in 15–20 min and followed by a continuous infusion (0.1–0.5 μg/ kg/h) | POD | CAM |
Kim et al. [19] | Korean | 2-arm RCT | 60/60 | General anaesthesia | Thoracoscopic lung resection surgery | I–III | 18–75 | NS | BIS | A fixed rate of 0.5 μg/kg/h until the end of the surgery | POD | CAM |
Tang et al. [32] | China | 2-arm RCT | 54/52 | General anaesthesia | Interventional embolisation | I to IV | 18–70 | NS | BIS | A loading dose of DEX (1.0 μg/kg) was administered for 15 min and then changed to a continuous infusion at 0.3 μg/kg/hand the infusion of DEX was stopped approximately 10 min before the end of surgery | POD | CAM-S |
Chen et al. [20] | China | 2-arm RCT | 80/80 | General anaesthesia | Elective cranial surgery | I–III | 20 +  | NS | BIS | An infusion of dexmedetomidine (0.5 μg /kg/ h) was started immediately before the induction of anaesthesia and was maintained throughout the surgery | POD | ICDSC |
Shin et al. [31] | Korean | 2-arm RCT | 366/366 | Spinal anaesthesia | Lower limb surgery | I–II | 65 +  | propofol | OAA/S | 1 μg/kg dexmedetomidine was administered for more than 10 min as the loading dose, followed by continuous administration at 0.1 to 0.5 µg kg/ h | POD | CAM |
Li et al. [24] | China | 2-arm RCT | 309/310 | General anaesthesia | Major non-cardiac surgery | I–III | 60 +  | NS | BIS | A loading dose of dexmedetomidine 0⋅6 μg/kg 10 min before induction of anaesthesia followed by a continuous infusion (0⋅5 μg/ kg/ h) until 1 h before the end of surgery | POD | CAM |
Mei et al. [29] | China | 2-arm RCT | DEX183 Control 183 | Spinal anaesthesia | Knee arthroplasty | I–IV | 65 +  | propofol | BIS | Loading dose of DEX0.8–1 μg/kg in 15–20 min and followed by a continuous infusion (0.1–0.5 μg/ kg/h) | POD | CAM |
Lee et al. [23] | Korean | 3-arm RCT | 95/109 | General anaesthesia | Laparoscopic major non-cardiac surgery | I to III | 60 +  | NS | BIS | received a dexmedetomidine 1 μg/kg bolus followed by 0.2–0.7 μg/kg/h infusion from induction of anaesthesia to the end of surgery | POD | CAM |
Li et al. [37] | China | 3-arm RCT | DEX55 Control 109 | Combined spinal-epidural anaesthesia | Hip or knee replacement | I–III | 65 +  | Propofol/midazolam | BIS | NR | POCD | The neuropsychological test battery |
Chawdhary et al. [36] | India | 2-arm RCT | 40/40 | General anaesthesia | non-cardiac surgery | I–III | 55 +  | PROPOFOL | BIS | dexmedetomidine 0.5–0.7 µg/kg/h | POCD | neuropsychological tests |
Mohamed et al. 1. [17] | Egypt | 2-arm RCT | 25/25 | General anaesthesia | Abdominal surgery | I to III | 60 +  | NS | GE Entropy | at a dose of 0.4 μg/kg/h | POCD | Stroop colour word interference test |
Mohamed et al. 2. [17] | Egypt | 2-arm RCT | 25/25 | General anaesthesia | Abdominal surgery | I to III | 60 +  | NS | GE Entropy | at a dose of 0.4 μg/kg/h | POCD | MoCA |
Nag et al. [38] | India | 2-arm RCT | 60/60 | Spinal anaesthesia | Hip surgery | I–III | 60–75 | NS | NI | Dexmedetomidine injection at a dose of 1 mcg/kg over 10 min, after Spinal Anaesthesia and before start of surgery, followed by a continuous infusion at a rate of 0.4 mcg/kg/h until the end of surgery | POCD | MoCA |