Background and Aims Ketamine is an effective treatment for both acute and chronic postoperative pain. Some evidence suggests analgesics may be effective in patients with a higher baseline risk of pain.1Therefore, we aimed to identify whether ketamine is more effective at reducing the incidence of chronic postsurgical pain (3 to 6 months) in patients on chronic opioid treatment.
Methods We conducted a systematic review of online databases (MEDLINE, Embase and CENTRAL) and unpublished studies. We included 23 studies of which 3 included patients on chronic opioid treatment. Only one study noted that majority of patients were on opioids (Hayes 2004)
Results Ketamine reduced the incidence of chronic pain in patients not on opioids (OR 0.55; 95% CI 0.38 to 0.80; I2=40%) but not in studies that included patients on chronic opioids (OR 1.04; 95% CI 0.52 to 2.09; I2=40%). However, this difference was not significant on subgroup analysis (p=0.12). There was no evidence of publication bias (p=0.49).The certainty of evidence was low due to problems with risk of bias and imprecision.
Conclusions No studies have been conducted in exclusively chronic opioid patients and therefore this warrants further trials into this important area of pain research.
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