Background and Goal of Study:Chronic Postsurgical Pain(CPSP) can be characterized as pain persisting for at least 3 months after surgery which was not present before surgery and localized to the surgical site.
CPSP frequently is diagnosed after thoracic surgery and the occurrence after minimally invasive cardiac surgery (MICS) is well documented. Increased post-operative pain and sympathetic tone are some of the many factors contributing to the development of CPSP and the use of regional anesthesia techniques such
as thoracic paravertebral block (TPVB) have been suggested to reduce the risk of CPSP. We hypothesized that continuous TPVB may reduce the occurrence rate of CPSP after MICS.
Materials and Methods:After institutional review board approval, we performed a retrospective record based review of all patients who underwent MICS at our center between March 2011 and October 2016. The occurrence of CPSP was defined as the presence of pain after at least 3-months post MICS after ruling out other possible causes of pain. A total of 91 patients were included for analysis. Patients were  grouped to either, the general anesthesia group (GA group; n=20) or the continuous TPVB group (n=71). Data collection included; patient characteristics, length of surgery, and postoperative analgesic consumption. Due to the imbalance in group size and potential bias related factors such as female sex, age, and length of surgery, we matched between groups with a 1:1 ratio using a propensity score based method. The matching yielded a final cohort of a total of 38 patients with 19 patients from each group. Values were compared using Student’s t-test for continuous variables and chi-square test for categorical variables, p<0.05 was considered statistically significant.
Results and Discussion:CPSP occurred in a total of 28(30.8%) cases. After matching the rate of CPSP was 47.4% (n=9) for the GA group was and 26.3% (n=5) for theTPVB group. The occurrence CPSP did not significantly differ between groups (Odds ratio 2.5, 95%confidence interval 0.65 - 10.0, p=0.18). Postoperative morphine consumption was significantly reduced between the GA group and TPVB group, 10.4±1.4 and 6.7±1.4 mg, respectively (p=0.035). There were no  complications related to the use of TPVB.
Conclusion(s):While the use of TPVB significantly reduce the need for postoperative analgesia with opioids, the use of TPVB did not reduced the occurrence of CPSP in patients undergoing MICS.

04 / Continuous thoracic paravertebral block for postoperative pain management in patients undergoing minimally invasive cardiac surgery and the occurrence of chronic postsurgical pain: a propensity-score-matched analysis