Teruya Komatsu

The importance of pleural integrity for effective and safe thoracic paravertebral block: a retrospective comparative study on postoperative pain control by paravertebral block.

OBJECTIVES Recently, paravertebral block (PVB) has been reported to be an effective analgesic modality for post-thoracotomy pain, but there is no consensus on how thoracic PVB can be more effective. Our hypothesis that intact pleura has a significant impact on the analgesic effectiveness of thoracic PVB was evaluated. METHODS Data of patients who underwent general thoracic surgery [thoracotomy or video-assisted thoracic surgery (VATS)] and paravertebral catheterization at Nagara Medical Center between April 2010 and March 2013 were collected. To compare the frequency of non-steroidal anti-inflammatory drugs taken as well as the usage of rescue pain medications between patients with pleural disruption and those without, data were analysed after matching on propensity scores. Covariates for match estimation were age, sex, body mass index, American Society of Anesthesiologists score, diagnosis, operative details and local anaesthesia infused. RESULTS There were 278 patients who underwent general thoracic surgery and paravertebral catheterization. The propensity score-matching process created 78 matched patients with pleural disruption and those without. Based on the propensity score matching, a significant increase in the frequency of non-steroidal anti-inflammatory drugs taken on postoperative day 1 and in the usage of rescue drugs was observed in patients with pleural disruption. CONCLUSIONS According to our analysis, creating a sub-pleural space without pleural disruption is essential for quality thoracic PVB.

Development of a composite and vascularized tracheal scaffold in the omentum for in situ tissue engineering: a canine model

OBJECTIVES We herein report on development of a composite (synthetic and biological) tracheal scaffold with vascularized autologous connective tissue in the omentum, followed by in situ tissue engineering of the composite scaffold with the pedicled omentum. In this preliminary report, we focus on development and evaluation of the vascularized autologous connective tissue in the omentum. METHODS In animal experiment 1, a polypropylene framework as a synthetic component was placed in the omental sac for 3 weeks and another was placed in the pouch of Douglas as a control in five beagle dogs. In animal experiment 2, a polypropylene framework placed in the omental sac for 3 weeks was compared with a polypropylene framework coated with porcine atelocollagen, which was also placed in the omental sac in another five dogs, to investigate whether the coating of porcine atelocollagen contributes to development of more vascularized connective tissue. Macroscopic, radiological and histological evaluations were performed for developed autologous connective tissue on the frameworks, with a focus on its thickness and capillary vessels. RESULTS In animal experiment 1, the polypropylene framework in the omentum developed a composite tracheal scaffold with homogeneous and significantly thicker (2.6 ± 0.5 vs 1.2 ± 0.4 mm, P <0.0001) connective tissue in which more capillary vessels per 10-power field of view (3.5 ± 2.2 vs 0 ± 0, P = 0.015) were identified, compared with the control in the pouch of Douglas. In animal experiment 2, the omentum developed significantly thicker connective tissue on the polypropylene framework coated with porcine atelocollagen (3.6 ± 0.7 vs 2.2 ± 0.4 mm, P <0.0001) in which not significantly more capillary vessels were identified (3.5 ± 2.2 vs 5.0 ± 2.7, P = 0.12), compared with the framework that was not coated. CONCLUSIONS Placement of the polypropylene framework in the omental sac resulted in development of homogeneous and vascularized autologous connective tissue on the polypropylene framework for a composite tracheal scaffold. The framework coated with porcine atelocollagen did not show an additional benefit in inducing vascularization. This preliminary report will be followed by the long-term evaluations of in situ tissue engineering of the composite tracheal scaffold.

A synthetic bioabsorbable sheet may prevent postoperative intrapleural adhesions following thoracotomy: a canine model

OBJECTIVES Intrapleural adhesions following thoracotomy may be associated with prolonged operating time or a higher complication rate at reoperation. The aim of this experimental study was to investigate the anti-adhesion property of a bioabsorbable sheet following thoracotomy in a canine model. METHODS Ten adult beagle dogs underwent bilateral muscle-sparing thoracotomies with single ribs resected under general anaesthesia. A bioabsorbable sheet composed of poly-L-lactide copolymer (45 wt%) and ε-caprolactone (45 wt%) layered with polyglycolic acid (10 wt%) was sutured intrapleurally on the parietal pleura to cover the defect on the left, but not placed on the right side as a control. All the dogs were followed up with chest computed tomography until being sacrificed (6 months at the maximum). Thoracoscopic evaluations were performed at 1, 3 and 6 months for intrapleural adhesions at the thoracotomy site and absorption of the bioabsorbable sheet. The incidences of intrapleural adhesions were compared between the experimental side and the control side by the χ(2) test. Histological (macroscopic and microscopic) analyses of regenerated chest wall tissue were also performed at 1, 3 and 6 months. RESULTS All the dogs survived uneventfully until being sacrificed without any postoperative complications or significant radiological findings. The bioabsorbable sheet prevented intrapleural adhesions in all subjects. There were statistically significant differences in the incidence of intrapleural adhesions between the experimental side and the control side at the thoracotomy incision (0 vs 80%, P = 0.0014) at 1 month, (0 vs 66.7%, P = 0.014) at 3 months and (0 vs 75%, P = 0.028) at 6 months. The bioabsorbable sheet was found residual at 1, 3 and 6 months in all subjects. Histological analyses confirmed regenerated chest wall layers with significantly more capillary vessels at 1 month (P = 0.015), but not at 3 and 6 months (P = 0.84 and 0.41, respectively), in the regenerated mucosal and submucosal layers on the experimental side. CONCLUSIONS Our findings suggest that the bioabsorbable sheet may prevent intrapleural adhesions with parietal pleurae regenerated with more vascularization at 1 month following thoracotomy. No adverse findings were noted with the sheet.

Development of a novel tissue-engineered nitinol frame artificial trachea with native-like physical characteristics

Background Tracheal reconstruction is complicated by the short length to which a trachea can be resected. We previously developed a biocompatible polypropylene frame artificial trachea, but it lacked the strength and flexibility of the native trachea. In contrast, nitinol may provide these physical characteristics. We developed a novel nitinol frame artificial trachea and examined its biocompatibility and safety in canine models. Methods We constructed several nitinol frame prototypes and selected the frame that most closely reproduced the strength of the native canine trachea. This frame was used to create a collagen‐coated artificial trachea that was implanted into 5 adult beagle dogs. The artificial trachea was first implanted into the pedicled omentum and placed in the abdomen. Three weeks later, the omentum‐wrapped artificial trachea was moved into the thoracic cavity. The thoracic trachea was then partially resected and reconstructed using the artificial trachea. Follow‐up bronchoscopic evaluation was performed, and the artificial trachea was histologically examined after the dogs were sacrificed. Results Stenosis at the anastomosis sites was not observed in any dog. Survival for 18 months or longer was confirmed in all dogs but 1, which died after 9 months due to reasons unrelated to the artificial trachea. Histological examination confirmed respiratory epithelial regeneration on the artificial tracheas luminal surface. Severe foreign body reaction was not detected around the nitinol frame. Conclusions The novel nitinol artificial trachea reproduced the physical characteristics of the native trachea. We have confirmed cell engraftment, good biocompatibility, and survival of 18 months or longer for this artificial trachea in canine models.

Development of a socket-type rib coaptation device made of poly- L-lactide fibers: feasibility study in a canine model

Background Costal coaptation pins made of poly-L-lactide (PLA) are clinically available for fixing surgically divided ribs. However, the clinical results of such rib fixation have not been completely satisfactory. We aimed to develop a new rib coaptation socket system and explore its clinical applicability. Methods We surgically divided three consecutive ribs of each beagle dog, and rib coaptation sockets were implanted to stabilize each rib. Fifteen 3-dimensional (3D)-printed and 30 PLA fiber knitted sockets were implanted in five and ten dogs, respectively, to stabilize the artificially divided ribs. Mechanical analysis of the sockets and radiographical examination of costal fixation were performed to evaluate the effectiveness of the newly developed socket system for rib stabilization. Results All 15 ribs with 3D-printed sockets had displaced 1 month after the operation. Three ribs in one dog with implanted PLA fiber knitted sockets were displaced radiographically after 1 month, and the grade of displacement remained unchanged after 6 months. The remaining 27 ribs fixed with PLA fiber knitted sockets did not show any displacement. Conclusions The PLA fiber knitted rib coaptation socket system was sufficiently durable for the stabilization of divided ribs with biocompatibility. This promising finding can be applied for clinical stabilization of divided ribs.

Development of novel force-limiting grasping forceps with a simple mechanism

OBJECTIVES In endoscopic surgery, fragile tissues may be damaged by the application of excessive force. Thus, we developed novel endoscopic forceps with a simple force-limiting mechanism. METHODS The novel forceps were constructed with a leaf spring, and the spring thickness determines grasping pressure. We established an evaluation system (maximum score is 11 points) for lung tissue damage leading to complications. We tested the conventional forceps (186.8 kPa) and 3 novel spring forceps with the following thicknesses: 1.3 mm (53.0 kPa), 2.2 mm (187.7 kPa) and 2.8 mm (369.2 kPa). After grasping, peripheral canine lung tissues were microscopically examined for acute- and late-phase damages. RESULTS In the acute phase (20 sites), the novel forceps caused capillary congestion and haemorrhage in the subpleural tissue, whereas the conventional forceps caused deep tissue and pleural damages. In the late phase (30 sites), both forceps caused fibroblast formation and interstitial thickening, which progressed to the deeper tissues as grasping pressure increased. In the acute phase, the median scores were 2.0 and 6.0 for the novel and conventional forceps, respectively (P = 0.003). In the late phase, the median scores were 2.0, 2.5 and 5.0 for 1.3-, 2.2- and 2.8-mm thick forceps, respectively, and 5.0 for the conventional forceps (P < 0.001). In both phases, the novel forceps with grasping pressure set below 187.7 kPa (2.2 mm) caused significantly less lung tissue damage than the conventional forceps. CONCLUSIONS The novel endoscopic forceps are able to regulate the tissue-grasping pressure and induce less damage in lung tissues than conventional forceps.