Study designs of evaluations included in the review
Randomised controlled double blind trials (RCTs) that evaluated extradural clonidine in the relief of post-operative pain were included if they had clearly defined objectives and adequate statistical analysis.
Specific interventions included in the review
Extradural clonidine, injected in the following ways, was studied: bolus injection alone, bolus followed by continuous infusion; bolus followed by patient-controlled analgesia infusion; bolus injection of a mixed solution followed by continuous solution; a mixed solution combining clonidine with fentanyl, local anaesthetics, two or more of these drugs, and continuous infusion of clonidine and morphine. Clonidine-bolus doses ranged from 75 to 800 micrograms, and from 1 to 8 micrograms/kg, and continuous infusions ranged from 0.3 to 2.0 micrograms/kg/hour and from 10 to 50 micrograms/hour. Administration was either intra-operatively, a few minutes after induction of anaesthesia, at the beginning of the surgical procedure, 30 minutes before the end of the surgical procedure, or post-operatively on arrival in the recovery room, 1-hour after surgery, or at the patients' first complaint of pain. Extra-dural catheters were inserted either thoracically or at the high and/or the low lumbar level. Additional analgesics were given via patient controlled analgesia, extradurally, intravenously, subcutaneously or intramuscularly and included morphine, pethidine, sufentanil, paracetamol, piritramide, ketoprofen and bupivicaine-fentanyl mixture. Control treatments were placebo; morphine; fentanyl; bupivicaine; bupivicaine plus morphine plus saline; IV clonidine; IV clonidine plus IV patient controlled analgesia; or extradural sufentanil.
Participants included in the review
Patients who were undergoing the following types of surgery were included: thoracotomy; orthopaedic (including menisectomy); rectal or colorectal; abdominal; Caesarean section; abdominal aorta; total hip replacement; abdominal hysterectomy; scoliosis repair; intestinal resection or re-anastomosis; pancreatic; and abdominal.
Outcomes assessed in the review
The following outcomes were assessed: side-effects including hypotension, bradycardia, and sedation; pain intensity assessed using visual analogue score (VAS) alone or in combination with verbal scale. VAS was assessed only at rest, at rest and at cough, at rest and after mobilization, and at rest, at cough and after mobilization.
How were decisions on the relevance of primary studies made?
Each study was reviewed independently by two assessors who graded the studies into one of four categories. Only those classified as grade 1 (RCT with clearly defined objectives and adequate statistical analysis) were included in the review.