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Acute Pain | Chronic Pain | General

Extradural clonidine for postoperative pain

Clinical bottom line:

Extradural clonidine appears to be effective alone and in combination with other analgesics for postoperative pain. Trials are not similar enough to allow an estimate of either degree of efficacy or guidelines on dose and administration regimen.


Clonidine for pain relief

Clonidine is an alpha-2 adrenoceptor agonist used primarily as an anti-hypertensive. The antinociceptive properties of clonidine have led to its use in pain relief, for which it is administered often in conjunction with local anaesthetic and/or opioids.

Systematic review

Armand S, Langlade A, Boutros A, Lobjoit K, Monrigal C, Ramboatiana R, Rauss A, Bonnet F. Meta-analysis of the efficacy of extradural clonidine to relieve postoperative pain: an impossible task. British Journal of Anaesthesia 1998; 81:126-134

Inclusion criteria were randomised controlled double blind trials of extradural clonidine for postoperative pain; appropriate statistical analysis; pain outcomes.

Reviewers based their conclusions on authors' conclusions from original reports. Adverse effects data were extracted from each trial.

Findings

Sixteen trials met inclusion criteria. Methods of administration were bolus injection with or without continuous infusion or patient-controlled analgesia. A number of trials had either mixed bolus solutions or mixed infusion solutions, including fentanyl, local anaesthetic and morphine. Administration was intraoperative and postoperative. Doses varied, and trial designs were different. Catheters were inserted either thoracically or at lumbar level. A range of additional analgesics were allowed.

Reviewers concluded that it was not possible to answer the question of efficacy from these trials because they were not sufficiently similar. The following summary is based on the reviewers précis of analgesic efficacy for each trial (efficacy is measured using either visual analogue ratings of pain, or verbal pain scores or analgesic consumption):

Two of three trials found clonidine to be more effective than placebo (2 µg/kg in orthopaedic and rectal surgery; 800 µg bolus + 20 µg/h and 400 µg bolus + 10 µg/h in caesarean section). The third trial of clonidine was no different to placebo (3 µg/kg in thoracic surgery).

In six of eight trials clonidine plus combination drug was more effective than combination drug alone (various doses, time of administration and surgical interventions).

In three of five trials clonidine plus combination drug was more effective than clonidine alone (various doses, time of administration and surgical interventions).

Adverse effects

Reviewers stated that hypotension, bradycardia and sedation were the main side effects reported. It is unclear whether there were any differences in occurrence of side effects in active or control groups.

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