| Summary: | 博士 === 元智大學 === 機械工程學系 === 97 === Patients undergoing cardiac surgery often dread the upcoming pain after surgery. The pain associated with cardiac surgery requiring sternotomy or thoracotomy originates from skin incisions, fractured sternum or ribs, parietal pleura and costoverterbral joint injury. Infusion of local anesthetics in the wound is a simple and safe method of pain control. It has been tested in various site and proved to be effective in iliac crest harvest site, sternotomy of cardiac surgery, thoracotomy after lung surgery, and hysterectomy. The main purposes of this study were to assess the effect of local wound infusion of local anesthetics on pain control in the thoracotomy wound of patients undergoing minimally invasive cardiac surgery, to disclose the factors determining the pain-controlling effect of bupivacaine wound infusion, including the concentration of bupivacaine, infusion rate, and location of infusion. Besides of acute pain, we also investigate if different duration or timing of local anesthetics administration would modify the pattern of chronic wound pain, and to investigate the effect of bupivacaine local infusion at sternotomy after off-pump coronary bypass grafting surgery on postoperative inflammatory cytokine surge.
Patients who underwent coronary artery bypass grafting or cardiac valvular procedures via a minimally invasive thoracotomy were studied. Patients were enrolled and randomly allocated to two groups with different modalities of postoperative analgesia. In the first part, the thoracotomy wound infusion group received 0.15% bupivacaine infused continuously at 2 mL/h through a catheter embedded in the wound, as well as intravenous patient-controlled analgesia. The control group had patient-controlled analgesia alone with a sham thoracotomy wound infusion of normal saline. Verbal analog pain scores (0–10 points) and recovery profiles were investigated. There were 19 patients in each group for complete data analysis. In this controlled double-blind study, thoracotomy wound infusion and patient-controlled analgesia was superior to patient-controlled analgesia alone in reducing pain at 1, 3, and 90 days after minimally invasive cardiac surgery. Second, we used 0.375% and 0.5% of bupivacaine or 2 mL/hr and 5 mL/hr to the patients to assess the effect of concentration and rate. Among these patients, there was no significant difference in both demographic data and perioperative characteristics. Third, we collected ten patients’ data and analyzed bupivacaine concentration in plasma by HPLC. All of them had 0.375% bupivacaine infused at 2ml/hour after operation. There was an increased trend from 24 to 48 hours after the operation. Forth, we also evaluate the inflammatory reaction by analyzed IL-8 and IL-10 concentration in plasma via ELISA. These patients were divided into two groups: 0.375% bupivacaine infused at 5ml/hour and normal saline. Individual variance was caused significant difference among time points. However, the trend of bupivacaine group was higher than saline group in IL-8, but the IL-10 was similar.
In the future, we want to find out the optimal concentration and infusion rate of local anesthetics wound infiltration in cardiac surgery and compare the pain relief effect of other alternative procedures or drugs. Besides, the anti-inflammation and antimicrobial effect was also noted in the in-vitro study, we try to construct an animal model and using the continuous infusion of local anesthetics methods in this model which may be helpful in this study. If this animal model is proved effective, maybe we can promote the continuous local anesthetics infiltration methods in cardiac surgery not only in pain relief, but also in the prevention of wound infection which was a major complication of cardiac surgery.
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