Clinical evaluation of two adult oxygenator systems in terms of mortality and major adverse events

PURPOSE

The primary aim of this study was to examine the effects of two oxygenator systems on major adverse events and mortality.

METHODS

A total of 181 consecutive patients undergoing coronary artery bypass grafting in our clinic were retrospectively analyzed. The patients were divided into two groups according to the oxygenator used: Group M, in which a Medtronic Affinity (Medtronic Operational Headquarters, Minneapolis, MN, USA) oxygenator was used, and Group S, in which a Sorin Inspire (Sorin Group Italia, Mirandola, Italy) oxygenator was used.

RESULTS

Group S consisted of 89 patients, whereas Group M included 92 patients. No statistically significant differences were found between the two groups in terms of age (p = .112), weight (p = .465), body surface area (p = .956), or gender (p = .484). There was no statistically significant difference in hemorrhage on the first or second postoperative day (p = .318 and p = .455, respectively). No statistically significant differences were observed in terms of red blood cell (p = .468), fresh frozen plasma (p = .116), or platelet concentrate transfusion (p = .212). Infections, wound complications, and delayed sternal closure were significantly more common in Group M (p = .006, p = .023, and p = .019, respectively). Extracorporeal membrane oxygenators and intra-aortic balloon pumps were required significantly more frequently in Group S (p = .025 and p = .013, respectively). Major adverse events occurred in 16 (18%) patients in Group S and 14 (15.2%) patients in Group M (p = .382). Mortality was observed in six (6.7%) patients in Group S and three (3.3%) patients in Group M (p = .232). No statistically significant difference was found between the two groups in terms of length of hospital stay (p = .451).

CONCLUSION

The clinical outcomes of the two oxygenator systems, including mortality, major adverse events, hemorrhage, erythrocyte and platelet transfusions, and length of hospital stay, were similar.

To Purge or Not to Purge

To remove gaseous microemboli (GME) using an oxygenator with an integrated arterial filter, it is recommended by some manufacturers to purge the oxygenator as an additional safety feature while on bypass. In this in vitro study, we evaluated whether purging of oxygenators with an integrated arterial filter is efficient in reducing GME. Five different types of commercially available contemporary oxygenators with an integrated arterial filter based on progressive filter filtration (1), cascade filtration (1), screen filtration (2), or self-venting (1) were tested for their efficiency in removing GME while keeping the purge line open or closed. A bubble counter was used for pre- and post-oxygenator GME signaling, from which the filter efficiency was computed. Freshly drawn heparinized porcine blood was used at blood flow rates of 3 and 5 L/min. Three units of each oxygenator were tested with its specific reservoir at a fixed volume level of 1,500 mL. GME load was introduced into the venous line at 1,000 mL air/min. Measurements started as soon as GME were detected by the pre-oxygenator probe and then continued for 1 minute. There was no statistically significant difference in filter efficiency between the purged and non-purged groups for specific oxygenators. At a blood flow of 3 L/min, the average filter efficiency stayed approximately invariable when comparing the non-purged and purged groups, where 89.1-88.2% indicated the largest difference between the groups. At a blood flow rate of 5 L/min, the filter efficiency changed in one screen filter group from an average of 55.7% in the non-purged group to 42.4% in the purged group. Other filter efficiencies at the blood flow rate of 5 L/min for non-purged compared with purged groups were, respectively, 98.0 vs. 98.0% (screen filtration), 88.6 vs. 85.8% (self-venting filtration), 82.8 vs. 75.5% (progressive filter filtration), and 65.4 vs. 65.1% (cascade filtration). Based on these results, purging while confronted with continuous GME challenge did not result in an increased filter efficiency.

Pumping O2 with no N2: An Overview of Hollow Fiber Membrane Oxygenators with Integrated Arterial Filters

The advancement of cardiac surgery benefits from the continual technological progress of cardiopulmonary bypass (CPB). Every improvement in the CPB technology requires further clinical and laboratory tests to prove its safety and effectiveness before it can be widely used in clinical practice. In order to reduce the priming volume and eliminate a separate arterial filter in the CPB circuit, several manufacturers developed novel hollow-fiber membrane oxygenators with integrated arterial filters (IAF). Clinical and experimental studies demonstrated that an oxygenator with IAF could reduce total priming volume, blood donor exposure and gaseous microemboli delivery to the patient. It can be easily set up and managed, simplifying the CPB circuit without sacrificing safety. An oxygenator with IAF is expected to be more beneficial to the patients with low body weight and when using a minimized extracorporeal circulation system. The aim of this review manuscript was to discuss briefly the concept of integration, the current oxygenators with IAF, and the in-vitro / in-vivo performance of the oxygenators with IAF.

The scientific evidence of arterial line filtration in cardiopulmonary bypass

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.