S(+)-ketamine for control of perioperative pain and prevention of Post Thoracotomy Pain Syndrome: a randomized, double-blind study

Background. Post-thoracotomy pain syndrome (PTPS) often complicates the long term outcome of patients; its appearance has been related to perioperative acute pain. The main goal of this study was to evaluate a possible role of S(+)-ketamine in the prevention of PTPS up to 6 months and secondarily its efficacy in the control of perioperative pain when added to thoracic epidural analgesia (TEA) and adjuvants. Methods. Sixty-six patients underwent thoracotomy under general anesthesia. A thoracic epidural catheter was placed for levobupivacaine and sufentanil administration. Thirty-three patients received an i.v. infusion of S(+)-ketamine (Group S(+)K) for 60 hours and 33 patients received iv. placebo (Group PLAC). Pain was evaluated by Numeric Rating Scale (NRS) during the whole study. All patients had supplementary doses of analgesics, as needed, to have NRS targeted to a value of <= 3 in the 1st and <3 in the following days. Neuropathic Pain Symptom Inventory (NPSI) was evaluated at 1, 3 and 6 months. Results. All patients had NRS <= 3 in the early postoperative period and NPSI was less or equal to 1 in the follow-up control for each group with no significant difference at three (P=0.67, OR 0.8 [IC95% 0.3-2.2]) and at six months (P=0.23, OR 1.9 [0.7-5.4]). Incidence of moderate PTPS was 24.6% at 3 and 21.1% at six months while severe PTPS was 6.6% at 3 and 1.8% at six months. No difference was detected in NRS and NPSI at 3 and 6 months between groups. Conclusion. S(+)-ketamine had no effects in respect to placebo in the prevention of PTPS at 3 and 6 months but hack a significant role in maintaining a NRS <= 3 in the early postoperative period. A tight control of perioperative pain seems to be associated with a low incidence of moderate and severe PTPS. (Minerva Anestesiol 2012;78:757-66)