Purpose: The aim of this study was to investigate the filtration efficacy of a 38-µm 1-layer screen filter based on Doppler registrations and video recordings of gaseous microbubbles (GME) observed in a microscope.
Methods: The relative filtration efficacy (RFE) was calculated from 20 (n = 20) sequential bursts of air introduced into the Plasmodex® primed test circuit.
Results: The main findings indicate that the RFE decreased (p = 0.00), with increasing flow rates (100-300 mL/min) through the filter screen. This reaction was most accentuated for GME below the size of 100 µm, where counts of GME paradoxically increased after filtration, indicating GME fragmentation. For GME sized between 100-250 µm, the RFE was constantly >60%, independently of the flow rate level. The video recording documenting the GME interactions with the screen filter confirmed the experimental findings.
Conslusions: The 38-µm 1-layer screen filter investigated in this experimental setup was unable to trap gaseous microbubbles effectively, especially for GME below 100 µm in size and in conjunction with high flow rates.
Background: The indication for arterial line filtration (ALF) is to inhibit embolisation during cardiopulmonary bypass. Filtration methods have developed from depth filters to screen filters and from a stand-alone component to an integral part of the oxygenator. For many years, ALF has been a standard adopted by a majority of cardiac centres worldwide. The following review aims to summarize the available evidence in support for ALF and report on its current practice in Europe. Method: The principles and application of ALF in Europe was investigated using a survey conducted in 2014. The scientific evidence for ALF was examined by performing a systematic literature search in six different databases, using the following search terms: Cardiopulmonary bypass AND filters AND arterial. The primary endpoint was protection against cerebral injury verified by the degree of cerebral embolisation or cognitive tests. The secondary endpoint was improvement of the clinical outcome verified elsewise. Only randomised clinical trials were considered. Results: The response rate was 31% (n=112). The great majority (88.5%) of respondents were using ALF, following more than 10 years of experience. Integrated arterial filtration was used by 55%. Of respondents not using ALF, fifty-four percent considered starting using integrated arterial filtration. The systematic literature database search returned 180 unique publications where 82 were specifically addressing ALF in cardiopulmonary bypass. Only four out of the 82 identified publications fulfilled our inclusion criteria. Of these, three were more than 20 years old and based on the use of bubble oxygenation. Conclusion: ALF is a standard implemented in a majority of cardiopulmonary bypass procedures in Europe. The level of scientific evidence available in support of current arterial line filtration methods in cardiopulmonary bypass is, however, poor. Large, well-designed, randomised trials are warranted.