European journal of pain : EJP
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Randomized Controlled Trial
Ketamine infusion for 96 hr after thoracotomy: Effects on acute and persistent pain.
Why is this significant?
This is the first randomised controlled trial looking at the impact of perioperative ketamine on persistent post-surgical (PPS) pain 1 year after thoracic surgery. Thoracotomy is associated with both severe and a high incidence (up to 50% at 6 months) chronic pain.
Ketamine has important analgesic properties through NMDA blockade, and has been long thought (hoped) that via this it may modify chronic post-surgical pain. Nonetheless, many studies have been unable to show a benefit for ketamine in reducing PPS pain.
What did they show?
Chumbley et al. ran ketamine infusions at 0.1 mg/kg/hour for 96 hours in patients undergoing thoracotomy, starting with a 0.1 mg/kg bolus 10 minutes before surgery. Patients also received either an epidural or paravertebral infusion for post-operative analgesia.
Although there were small differences in acute pain (notably the ketamine group used less PCA morphine) there was no difference in persistent post-surgical pain at 12 months.
Bottom-line
The evidence continues to mount against perioperative ketamine, suggesting it does not reduce persistent post-surgical pain, not-withstanding its acute analgesia benefits. Await results of the ROCKet trial (Reduction Of Chronic Post-surgical Pain with Ketamine) to provide greater clarity...
An afterthought
Notably, the researchers did demonstrate a dramatically lower incidence of PPS pain than for similar studies (27%, 18%, 13% at 3, 6, 12 months) across both the ketamine and placebo group. This suggests that either the study participants were not representative of the typical thoracotomy patient (unlikely), or other care associated with the study had a beneficial effect on reducing PPS – perhaps even via a Hawthorne-like effect.
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Observational Study
Spinal cord stimulation for chronic refractory pain: long-term effectiveness and safety data from a multicentre registry.
Spinal cord stimulation (SCS) is an established therapy for refractory neuropathic pain. To ascertain the balance between treatment benefits and risks, the French National Authority for Health requested a post-market registry for real-world evaluation of the long-term effectiveness and safety of the therapy. ⋯ This observational, prospective study in a real-life setting followed a large cohort of patients suffering from chronic pain and implanted with SCS devices in France. The study assessed the long-term effectiveness and safety of SCS therapy in a representative sample of implanting sites in France.
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Randomized Controlled Trial
The effect of total intravenous anaesthesia with propofol on postoperative pain after third molar surgery: a double blind randomized controlled trial.
Total intravenous anaesthesia (TIVA) with propofol may reduce pain after surgery compared with inhalational anaesthetic techniques. Whether propofol provides analgesic benefit may be influenced by the surgical procedure and anaesthetic/analgesic regime. Third molar surgery is a consistent and fairly standard surgical technique that provides a good model for postoperative pain. We investigated whether propofol TIVA or sevoflurane (SEVO) inhalational anaesthesia would produce better quality pain relief after third molar surgery. ⋯ Choice of general anaesthetic technique can affect postoperative analgesia. The results of this study suggest that propofol TIVA improves postoperative pain and patient satisfaction after third molar surgery compared to inhalational anaesthesia.
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Randomized Controlled Trial
Rewarded placebo analgesia: A new mechanism of placebo effects based on operant conditioning.
Placebo analgesia is explained by two learning processes: classical conditioning and observational learning. A third learning process, operant conditioning, has not previously been investigated as a mechanism of placebo effects. We aimed to induce placebo analgesia by operant conditioning. ⋯ According to the current placebo literature, placebo analgesia can be explained by two learning processes: classical conditioning and observational learning. A third learning process, operant conditioning, has not previously been investigated as a mechanism of placebo effects. Our study reveals that patients can learn placebo analgesia as a result of operant conditioning, suggesting that randomized controlled trials could be improved by controlling the reinforcement that might occur spontaneously when patients interact with, for example, medical personnel.
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Pain models are commonly used in drug development to demonstrate analgesic activity in healthy subjects and should therefore not cause long-term adverse effects. The ultraviolet B (UVB) model is a model for inflammatory pain in which three times the minimal erythema dose (3MED) is typically applied to induce sensitization. Based on reports of long-lasting postinflammatory hyperpigmentation (PIH) associated with 3MED, it was decided to investigate the prevalence of PIH among subjects who were previously exposed to 3MED at our research centre. In addition, re-evaluation of the UVB inflammation model using a reduced exposure paradigm (2MED) was performed in healthy subjects. ⋯ Postinflammatory hyperpigmentation is an unwanted long-term side effect associated with the UVB inflammation model using the 3× minimal erythema dose (3MED) paradigm. In contrast, using a 2MED paradigm results in hyperalgesia that is stable for 36 hr and has a lower risk of inducing postinflammatory hyperpigmentation.