Initial Resistance of Carina Anastomoses with Increasing Tensile Stress: An ex vivo Model Comparing Different Suture Techniques

Abstract

Background: After resection of the carina with a length of more than 4 cm, anastomoses often need to be performed under tension despite maximum mobilization. If the patient cannot be extubated, the anastomosis remains under continued stress. Anastomoses of the carina can be constructed using various suture techniques, including single interrupted sutures, back wall running but front wall single interrupted sutures, and complete running suture. This experimental study was designed to determine the most tensile stress-resistant anastomotic suture technique. Materials and Methods: Isolated preparations of tracheobronchial trees were recovered from freshly slaughtered pigs. Resection of the carina was carried out in preparation of the experiments. After blind randomization, anastomoses (n = 15 per group) between the distal trachea and the proximal left main bronchus were performed with PDS 4-0 employing three different suture techniques: (1) single interrupted sutures, (2) back wall running but front wall single interrupted sutures (= mixed technique), and (3) complete running suture. The anastomotic specimen was fixed onto a specially constructed device. The tracheal end was intubated with a tube (CH 8.0) and connected to a respirator. Different weights were attached to the distal end of the preparation via a clamp and guide rollers. Airtightness was investigated at the following tensile loads: 0, 500, 1,000 and 1,500 g. Intrabronchial pressure was increased in 5-mbar steps. In an underwater trial, we analyzed whether anastomoses were airtight at a maximum intrabronchial ventilation pressure of 70 mbar. Results: At an intrabronchial pressure of 25 mbar without tensile stress, all anastomoses were initially airtight. In tensionless anastomoses at 70 mbar, 100% of single interrupted and continuous sutures were airtight, as compared to 80% of sutures in mixed technique. At 70 mbar and tensile loads of 1,500 g, 80% of single interrupted sutures, 60% of sutures in mixed technique and 53% of the running sutures remained competent. Conclusion: If tracheal anastomoses can be performed without tension, the suture technique is not important. With increased tension, anastomoses performed in single interrupted suture technique were clearly superior. Thus, in situations, where high tensile stress is to be expected, single interrupted sutures should be preferred.