Low Versus High Pressure Suction Drainage After Total Knee Arthroplasty

In the experimental group the drainage catheter was connected to a modified DRENOFAST® system. This system consisted of a sterile plastic bottle with a holding capacity of 600 mL of fluid and a negative pressure of 700mmHg. It was hermetically closed and had two connections. The DRENOFAST® modification consisted of establishing an open connection between the bottle and a wall vacuum source (normally used to administer oxygen) placed next to the patient's bed. The 50 mmHg constant negative pressure of the bottle was maintained by the wall vacuum source and verified by flow meter. Duration: Drains were removed after bleeding had ceased (48-72h).

In order to mask the type of intervention from the patient and the investigators, both drainage systems had two drain catheters. One catheter allowed the blood to flow from the wound to the bottle. The second catheter connected the bottle to the vacuum source. In the experimental arm the second catheter was open, while in the control group it was closed. So that the system used could not be distinguished, the connection of the second catheter to the bottle was covered with opaque adhesive tape.Drains were removed after bleeding had ceased.