Abstract
BACKGROUND: Moderate to severe postoperative pain is common among patients following thoracotomy and serves as a risk factor for developing chronic post-thoracotomy pain (CPTP). This randomized controlled trial evaluated the effects of pre-emptively administered ketamine compared to placebo and standard care on both acute postoperative pain and CPTP. METHODS: Two hundred patients were enrolled in this prospective, randomized trial. The presence and severity of pain were assessed before surgery, first 6 hours after surgery, on postoperative days (PODs) 1-8, 30, and 90. For documentation of neuropathic pain, the Leeds Assessment Score for Neuropathic Symptoms and Signs (LANSS) was used pre- and postoperatively. The incidence and severity of CPTP was assessed by a telephone survey, the self-assessment LANSS (S-LANSS) 30 and 90 days after surgery. RESULTS: There was significant difference in numeric rating scale (NRS) pain scores when coughing in the first 6 hours after surgery, with less pain in the ketamine group. No difference was seen in NRS pain scores at rest and coughing between the ketamine and placebo group on PODs 1-8. There was no difference in the opioid consumption between the two groups. Thirty-four (18.7%) of the patients had a S-LANSS score ≥12 30 days following surgery, 12 (12.8%) in the ketamine group vs. 22 (25%) in the placebo group (P=0.001). Thirty-three (18.2%) of all patients had a S-LANSS score ≥12 90 days following surgery 8 (8.5%) in the ketamine group vs. 25 (28.4%) in the placebo group (P<0.001). CONCLUSIONS: In summary, pre-emptive ketamine does not reduce opioid consumption and NRS scores after thoracotomy but more importantly it lowers significantly the incidence of chronic postoperative pain, especially neuropathic pain. TRIAL REGISTRATION: The study was registered at ClinicalTrials.gov (NCT03105765).