Prebypass filtration of cardiopulmonary bypass circuits: an outdated technique?

Abstract

Filtration of cardiopulmonary bypass (CPB) priming fluid before connection of the circuit to the patient was first accomplished by arterial line filtration. When dedicated prebypass filters (PBFs) with smaller pore sizes became available, a large number of particles could be found on the filter surface. In recent years, modern manufacturing methods for CPB circuit components were believed to be associated with a reduced number of particles found in components of extracorporeal circuits, making separate filtration of CPB priming solution unnecessary. Microemboli generated during the preparation and priming procedure of the CPB circuit may consist of either solid particles or gaseous emboli and may contribute to patient morbidity. Endotoxins found in infusion solutions and CPB priming solutions may trigger inflammatory responses when administered into the circulatory system. Filtration of crystalloid CPB priming solutions with a PBF consisting of a filter membrane with a pore size of 0.2 microm was found to effectively reduce the number of microemboli. Infusion filters with a filter pore size of 0.2 microm were found to reduce the endotoxin contamination in infusion solutions. Prebypass filtration with filters containing pores of 0.2 pm should be a necessity for contemporary perfusion practice.

Microemboli detection on extracorporeal bypass circuitsa

“…Similar difficulty was found in eliminating air until the position of the pre-bypass filter was adjusted to prevent entrained air from exiting the filter into the reservoir. So while Merkle 34 studied 0.2 micron pre-bypass filters and found that it reduced GME less than 5 microns during priming, such results assume that the bypass filter itself is properly de-aired. If not, the filter itself may be a source of air.…”

Cardiopulmonary Bypass

“…Several fi lters used within the extracorporeal circuit reduce the gaseous and particulate microemboli passed to the patient. During the priming process, a pre-bypass fi lter removes any debris that may be present from the manufacturing process as well as reduces contamination from the endotoxins found in priming solutions [51]. Because of its small pore size (0.2 μm), this fi lter is removed from the circuit before the addition of blood.…”

Handling ability of gaseous microemboli of two pediatric arterial filters in a simulated CPB model

“…Otherwise, GME and particles can become lodged in small vessels, resulting in the dysfunction of organs due to microembolisms. 2,4 –7…”

“…These filters include: a pre-bypass filter, a cardioplegia filter, a venous reservoir filter, a cardiotomy reservoir filter with de-foaming material, an arterial filter and some specially-designed filters, for example, a leukocyte-depletion filter, a blood transfusion filter and an aortic filter. 4,5,8,9 Of these, arterial filters are playing a crucial role in capturing arterial GME in the CPB circuit. In the United States, most pediatric CPB procedures are now done with the use of an arterial filter.…”

“…Otherwise, GME and particles can become lodged in small vessels, resulting in the dysfunction of organs due to microembolisms. 2,[4][5][6][7] In order to minimize the risk of foreign objects and GME from entering a patient's bloodstream, many filters are used in an attempt to trap the particles and GME before they can reach the patient. These filters include: a pre-bypass filter, a cardioplegia filter, a venous reservoir filter, a cardiotomy reservoir filter with de-foaming material, an arterial filter and some specially-designed filters, for example, a leukocyte-depletion filter, a blood transfusion filter and an aortic filter.…”