However , intercostal nerve injury seems to be the most important pathogenic factor .
Chronic pain complaints after thoracic surgery represent a significant clinical problem in 25 - 60 % of patients .
Results from thoracic and other surgical procedures suggest multiple pathogenic mechanisms that include pre- , intra- , and postoperative factors .
This review attempts to analyse the methodology and systematic s of the studies on the  post-thoracotomy pain syndrome ( PTPS ) after lung cancer surgery in adults , in order to clarify the relative role of possible pathogenic factors and to define future strategies for prevention .
Low-dose Intravenous Ketamine Potentiates Epidural Analgesia after Thoracotomy
Background : Ketamine potentiates intravenous or epidural morphine analgesia . The authors hypothesized that very-low-dose ketamine infusion reduces acute and long-term postthoracotomy pain . Methods : Forty-nine patients scheduled to undergo open thoracotomy were r and omly assigned to receive one of two anesthesia regimens : continuous epidural infusion of ropivacaine and morphine , along with intravenous infusion of ketamine ( 0.05 mg · kg−1 · h−1 [ approximately 3 mg/h ] , ketamine group , n = 24 ) or placebo ( saline , control group , n = 25 ) . Epidural analgesia was continued for 2 days after surgery , and infusion of ketamine or placebo was continued for 3 days . Pain was assessed at 6 , 12 , 24 , and 48 h after surgery . Patients were asked about their pain , abnormal sensation on the wound , and inconvenience in daily life at 7 days and 1 , 3 , and 6 months after surgery . Results : The visual analog scale scores for pain at rest and on coughing 24 and 48 h after thoracotomy were lower in the ketamine group than in the control group ( pain at rest , 9 ± 11 vs. 25 ± 20 and 9 ± 11 vs. 18 ± 13 ; pain on coughing , 26 ± 16 vs. 50 ± 17 and 30 ± 18 vs. 43 ± 18 , mean ± SD ; P = 0.002 and P = 0.01 , P < 0.0001 and P = 0.02 , respectively ) . The numerical rating scale scores for baseline pain 1 and 3 months after thoracotomy were significantly lower in the ketamine group ( 0.5 [ 0–4 ] vs. 2 [ 0–5 ] and 0 [ 0–5 ] vs. 1.5 [ 0–6 ] , median [ range ] , respectively ; P = 0.02 ) . Three months after surgery , a higher number of control patients were taking pain medication ( 2 vs. 9 ; P = 0.03 ) . Conclusions : Very-low-dose ketamine ( 0.05 mg · kg−1 · h−1 ) potentiated morphine-ropivacaine analgesia and reduced postthoracotomy pain
However , intercostal nerve injury seems to be the most important pathogenic factor .
Chronic pain complaints after thoracic surgery represent a significant clinical problem in 25 - 60 % of patients .
Results from thoracic and other surgical procedures suggest multiple pathogenic mechanisms that include pre- , intra- , and postoperative factors .
This review attempts to analyse the methodology and systematic s of the studies on the  post-thoracotomy pain syndrome ( PTPS ) after lung cancer surgery in adults , in order to clarify the relative role of possible pathogenic factors and to define future strategies for prevention .