Effects of Perioperative Systemic Ketamine on Development of Long-term Neuropathic Pain After Thoracotomy

Lung surgery under thoracotomy is known to induce long-term pain which can be considered as neuropathic in many patients concerned \[1,2\]. The suspected origin of neuropathy is a direct traumatism of intercostal nerve(s) \[3\]. Among the possible preventive treatments that can be administered during the initial aggression, ketamine \[4,5\] appears as the easiest to use, as it is already commonly administered intra and postoperatively for improvement of analgesia \[6\]. This study compares two groups of patients undergoing thoracotomy for partial pneumonectomy, one receiving intravenous ketamine since the beginning of procedure and then during 48 hours, the other receiving inactive normal saline (placebo). The study is prospective, randomized, and double-blinded. The primary endpoint is to reduce chronic pain (on visual analogue scale) at the 4th month after surgery with ketamine. The objective is to obtain a mean value under 20/100 in the ketamine group, considering that the expected mean value for the control group is 38/100 (based on personal observations). The secondary endpoints are lower scores of neuropathic pain in the ketamine group, assessed by the NPSI questionnaire \[7\]. The impact of treatment on quality of life, assessed by a questionnaire (SF-36), is also studied. The data collected by clinical and psychophysical examination performed on all patients at the 4th month after surgery will be also considered for analysis, in order to understand better the features of post-thoracotomy neuropathic pain.