Experimental Assessment of the Drainage Capacity of Small Fluted Silastic Drains in Cardiovascular Surgery: Comparison with the Conventional Chest Tubes

Abstract

Background: Cardiac surgery requires the placement of drains in the mediastinum, pericardial space, and pleural spaces at the end of the procedure. Recently, small, flexible, fluted silicone drains have been widely used after cardiac surgery. Although preliminary reports suggest that small silastic drains are superior to conventional rigid large-bore chest tubes, there has been no experimental comparison of the drainage capacity of these drains under similar conditions. To compare the efficacy of smaller silastic drains and conventional chest tubes, a three-part in vitro and two-part in vivo experiment was performed. Methods: In the first part of the in vitro study, the drainage capacity of 19-F silicone drains and 28-F conventional tubes was tested under steady flow. Both tubes were placed in a water bath and drained at a pressure of 10mm Hg. In the second part of the in vitro study, the drainage pattern was also visualized. Finally, an anatomically identical apparatus, consisting of a silicone ventricle and a latex-rubber pericardium, was employed to simulate drainage under clinically similar conditions. In the in vivo study, 19-F and 24-F silicone drains and 28-F and 32-F conventional tubes were inserted into the hemithorax or pericardial space of 12 adult pigs. Blood was infused into both chest cavities or pericardial spaces, and the tubes were drained at 15cmH2O. Results: In the in vitro study, the drainage capacity of the conventional chest tubes was 7 times greater than that of the smaller silicone drains. However, in the in vivo pleural drainage test, the drainage capacity of the smaller silicone drains was greater than that of the conventional chest tubes. Additionally, in the in vivo pericardial drainage test, there was no difference in drainage capacity between the two types of tube. Furthermore, the flow visualization test revealed different drainage patterns in the two tubes and showed that the most effective portions were the most proximal slits of the silicone drain and the side holes of the conventional chest tube. However, in the in vitro pericardial model, there was no difference in drainage capacity between the two types of tube, as the slits or side holes were completely within the pericardial cavity. Conclusions: This experiment demonstrated that the smaller silastic chest drains have a sufficient drainage capacity that is almost identical and possibly superior to that of conventional chest tubes.