Continuous Postoperative Pericardial Flushing After General Cardiac Surgery Procedures With the Haermonics Investigational Device: Study Protocol of the FLUID (FLUsh With Investigational Device) Trial

CPPF therapy

Prolonged or excessive bleeding after cardiac surgery can lead to a broad spectrum of secondary complications. One of the underlying causes is incomplete wound drainage, with subsequent accumulation of blood and clots in the pericardium. It has been demonstrated that this retained blood and clots lead to even more fibrinolytic activity in the mediastinum and pericardial space, and therefore may contribute to increased or prolonged bleeding. Based on this principle, the method of continuous postoperative pericardial flushing (CPPF) has been invented and further developed. The hypothesis is that CPPF therapy works by mechanical cleaning properties and by diminishing fibrinolysis and inflammation. The CPPF protocol includes the inflow of NaCl 0,9% flushing fluid into the pericardial cavity during the first postoperative hours in patients who underwent cardiac surgery. In this way, the blood and clot mixture can be diluted into a lower viscosity solution, thereby enhancing the evacuation of blood and clots from the pericardial space and preventing chest tube obstruction.

The Haermonics investigational device

Because CPPF therapy includes the dilution of the normal postoperative mediastinal chest tube drainage (MCTD), the clinical assessment of the exact amount of blood loss is more difficult. Yet, blood loss is an important factor in clinical decision making, namely the decision if the patient needs a surgical re-exploration for postoperative bleeding or not. Roughly, in patients who receive CPPF therapy, blood loss can be estimated by extracting the total inflow flushing volume from the total MCTD. This method was used in the experimental setting of the previous CPPF trails but is considered unsuitable for use in daily practice because of three reasons. First, the required registration of in- and outflow volume is labour intensive. Secondly, because this registration can only be done intermittently, which can be dangerous in case of a fast bleeding rate. Thirdly, blood loss calculation could potentially be inaccurate because sometimes, clinically insignificant, amounts of flushing fluid are retained or absorbed in the pericardial or pleural spaces, thereby making the blood loss calculation inaccurate.

The first commercial Haermonics device will have four essential functionalities that make CPPF therapy safe and feasible for daily clinical use. 1) Automatic monitoring of the outflow volume, 2) Quantification of the content of the outflow volume by means of real time and continuous haematocrit (hct) analysis of the MCTD, 3) Warming of the flushing fluid to body temperature and temperature measurements of the flushing fluid, and 4) Continuous intrapericardial pressure measurement. The investigational device that will be used in this study will have all these functionalities, but available data will not be used for clinical decision making yet.