Can minimized cardiopulmonary bypass systems be safer?

Abstract

Although a growing body of evidence indicates superiority of minimized cardiopulmonary bypass (mCPB) systems over conventional CPB systems, limited venous return can result in severe fluctuations of venous line pressure which can result in gaseous emboli. In this study, we investigated the influence of sub-atmospheric pressures and volume buffer capacity added to the venous line on the generation of gaseous emboli in the mCPB circuit. Two different mCPB systems (MEC - Maquet, n=7 and ECC.O - Sorin, n=8) and a conventional closed cardiopulmonary bypass (cCPB) system (n=12) were clinically evaluated. In the search for a way to increase volume buffer capacity of mCPB systems, we additionally evaluated the 'Better Bladder' (BB) in a mock circulation by simulating, repeatedly, decreased venous return while measuring pressure and gaseous embolic activity. Arterial gaseous emboli activity during clinical perfusion with a cCPB system was the lowest in comparison to the mCPB systems (312±465 versus 311±421 with MEC and 1,966±1,782 with ECC.O, counts per 10 minute time interval, respectively; p=0.03). The average volume per bubble in the arterial line was the highest in cases with cCPB (12.5±8.3 nL versus 8.0±4.2 nL with MEC and 4.6±4.8 nL with ECC.O; p=0.04 for both). Significant cross-correlation was obtained at various time offsets from 0 to +35 s between sub-atmospheric pressure in the venous line and gaseous emboli activity in both the venous and arterial lines. The in vitro data showed that incorporation of the BB dampens fluctuations of venous line pressure by approximately 30% and decreases gaseous emboli by up to 85%. In conclusion, fluctuations of sub-atmospheric venous line pressure during kinetic-assisted drainage are related to gaseous emboli. Volume buffer capacity added to the venous line can effectively dampen pressure fluctuations resulting from abrupt changes in venous return and, therefore, can help to increase the safety of minimized cardiopulmonary bypass by reducing gaseous microemboli formation resulting from degassing.

Platelet Function During Hypothermia in Experimental Mock Circulation

“…Mock circulation loops (MCLs) are used to mimic the vascular system in the development and improvement of cardiovascular devices (e.g., ventricular assist devices and heart valves) . They are designed from simple nonpulsatile loops to high‐tech systems imitating normal and pathologic human circulation.…”

The bypass plan

“…There is an increased risk of MAE with VAVD but it is probably underappreciated that even systems not utilizing VAVD can be at an increased risk for MAE as manufacturers have redesigned their venous reservoirs to allow them to be sealed [133].Proper understanding of drainage techniques and careful consideration of the pitfalls of each modality are essential to prevent neurologic complications due to air transmission in cardiac surgery patients [122,123,132]. Augmented return allows for the use of smaller diameter cannulae and venous tubing, may decrease circuit prime volume and limit hemodilution and transfusion, may improve venous drainage, cardiac decompression and visualization at the surgical field, and allow for minimally invasive surgical techniques.…”

“…Roller pump, kinetic, and vacuum-assisted venous drainage have been reported, each with unique considerations for cardiopulmonary bypass [119][120][121][122][123][124][125][126][127][128][129][130][131][132][133]. Venous return is visually monitored through out the bypass run and quantified by changes in the venous reservoir level.…”

“…A sealed reservoir with a single vent port has the ability to become pressurized. A negative pressure relief valve may also be used on the reservoir as an additional safety mea sure to prevent pressure values greater than −100 mmHg [122]. The venous system in effect becomes the path of least resistance for the pressure gradient that develops.…”

The Hidden Limitations in “Advertising” a Novel Synchronized Cardiac Assist Device

“…A lack of blood volume available for drainage during pump acceleration results in severely low venous line pressure. This leads to a "de novo" formation of gas bubbles due to degassing (12)(13)(14).…”