Arterial Filter Bypass Loop: What Occurs in this Area during Cardiopulmonary Bypass and Are There Potential Patient Implications

The arterial filter is an integral part of bypass circuitry. When introduced, manufacturers suggested a bypass loop for retrograde priming and de-airing, and for uninterrupted blood flow in case of malfunction. Practice has shown antegrade priming and de-airing is possible. This questions the necessity of the loop and presents the question—what occurs in the loop during bypass? After obtaining Human Research Ethics Board approval, eight consecutive patients (n = 8) were chosen for this study. Exclusive exclusion criterion was receiving any transfusions during cardiopulmonary bypass, as this could possibly influence results. The choice of patient numbers was based simply on proof of concept. Investigation involved isolation and collection of loop contents after cardiopulmonary bypass was completed. Testing included complete blood count, prothrombin time, international normalized ratio, partial thromboplastin time, activated clotting time, plasma free hemoglobin, slide photography with analysis for platelet clumping, and debris detection. One perfusionist collected samples, providing uniform collection and isolation technique. Regular blood samples were collected from the bypass circuitry, and from patients’ pre-operative blood work. Analysis of data revealed that platelet counts in the bypass loops were statistically lower than control. Evidence of platelet clumping was present in 3 of 8 bypass loop samples, representing 37.5% of the study population. There was no clumping detected in any of the controls. In patients where platelet clumping was present, a positive correlation was noted between mean bypass time and size of platelet clumps. Prothrombin time and international normalized ratio results were immeasurable. Hemoglobin levels were higher in the loop samples. There was no evidence of debris or fibrin monomer present in any of the samples analyzed. The study results indicate that during “normal” cardiopulmonary bypass with an arterial filter bypass loop, platelet aggregates can accumulate in the loop, therefore opening the arterial bypass loop in any case may subject the patient to micro/macro emboli

Clinical Evaluation of the Sorin Synthesis™ Oxygenator With Integrated Arterial Filter

The use of arterial line filters has long been a standard of practice in the field of cardiopulmonary bypass. Sorin Biomedica has designed an adult hollow-fiber oxygenator that not only incorporates their Mimesys® biomimicry coating technology but also has a 40-micron arterial filter as an integrated component of this unique membrane oxygenator. We did a prospective, randomized clinical trial of 54 Synthesis® coated oxygenators and compared them with 54 uncoated Monolyth Pro® oxygenators, the latter of which incorporated an external arterial line filter with a standard bypass loop There were few statistically significant differences found between the Synthesis® group and the Monolyth group with regard to pressure differentials, hemodynamic resistance, and platelet drop. The Synthesis® oxygenator did require less priming volume, but the amount was not significant. Platelet counts with the Phosphorylcholine coated Synthesis oxygenators, using crystalloid perfusates, was similar to our previously published data on platelet protection and Albumin perfusates. We conclude that the Sorin Synthesis® oxygenator appears to have better flow characteristics than the Monolyth oxygenator, with the potential for lower priming volumes. The most clinically significant benefit comes from the elimination of the arterial filter bypass loop and the avoidance of inverting the arterial filter during priming

Evaluation of Mimesys® Phosphorylcholine (PC)-Coated Oxygenators during Cardiopulmonary Bypass in Adults

A new generation of coating extracorporeal circuitry with biocompatible polymers has entered the North American perfusion market. This new biomimetic coating process uses synthetic phosphorylcholine (PC) containing polymers to bond covalently to the surface of the Sorin Monolyth® oxygenator, under the brand name of Mimesys®. In part one of a three-part investigation, 160 Mimesys®-coated oxygenators were randomly evaluated against 36 uncoated oxygenators for blood flow, hemodynamic resistance, and pressure differentials. In part two, retrospective analysis of platelet data collected in this study was compared with platelet data collected from a previous investigation using uncoated Monolyth oxygenators with albumin and crystalloid perfusates. Part three examined the risk-adjusted oxygenators, compared with 71 case-matched patients treated with uncoated oxygenators. There was no difference found in the Mimesys-coated group, when compared to the control group, with regard to pressure differentials or hemodynamic resistance. However, we conclude that platelet protection with PC-coated Monolyth’s using crystalloid perfusates, was similar to platelet protection with albumin perfusates, and significantly better than uncoated Monolyths® using crystalloid perfusates