First Clinical Experience With the Air Purge Control and Electrical Remote-controlled Tubing Clamp in Mini Bypass

Air removal capacity of two different minimal invasive ECC systems: an in vitro comparison

Minimally invasive extracorporeal circulation systems are developed to decrease the deleterious effects of cardiopulmonary bypass. For instance, prime volume and foreign surface area are decreased in these systems. However, because of the lack of a venous reservoir in minimized systems, air handling properties of these minimally invasive extracorporeal circulation systems may be decreased as compared to conventional cardiopulmonary bypass systems. The aim of this in vitro study is to compare the air handling properties of two complete minimized cardiopulmonary bypass systems of two manufacturers, of which one system is provided with the air purge control. In an in vitro study, two minimally invasive extracorporeal circulation systems, Inspire Min.I manufactured by Sorin Group Italia, Mirandola, Italy (LivaNova, London, United Kingdom) and minimized extracorporeal circulation manufactured by Maquet, Rastatt, Germany (Getinge, Germany), were challenged with two types of air challenges; a bolus air challenge and a gaseous microemboli challenge. The air removal characteristics of the venous bubble traps and of the complete minimally invasive extracorporeal circulation systems were assessed by measuring the gaseous microemboli volume and number downstream of the venous bubble traps in the arterial line with a bubble counter. No significant differences were observed in air reduction between the venous bubble traps of Getinge (venous bubble traps) and LivaNova (Inspire venous bubble traps 8 in conjunction with the air purge control). Similarly, no significant differences were observed in volume and number of gaseous microemboli in the arterial line of both complete minimally invasive extracorporeal circulation systems. However, the gaseous microemboli load of the Inspire Min.I system was marginally lower after both the bolus air and the gaseous microemboli challenges. Both minimally invasive extracorporeal circulation systems assessed in this study, the LivaNova Inspire Min.I and the Getinge minimized extracorporeal circulation, showed comparable air removal properties, after both bolus and gaseous microemboli air challenges. Besides, air purge control automatic air removal system provided with the LivaNova Inspire Min.I. system may enhance patient's safety with the use of a minimally invasive extracorporeal circulation system. We consider both systems equally safe for clinical use.

Reduction in blood product usage associated with routine use of mini bypass systems in extracorporeal circulation

Objective: The objective of this study is to investigate the hypothesis that a reduced prime extracorporeal circulation (ECC) system and ensuing reduction in patient hemodilution can affect blood product use. Methods: We performed a prospective, randomized study from a group of 60 consecutive coronary artery bypass graft (CABG) patients, comparing blood product usage and postoperative bleeding in 30 mini bypass systems (n = 30) to 30 conventional systems (n = 30). The patient demographics in terms of patient weight, height, age, preoperative hemoglobin, preoperative hematocrit, BSA, ejection fraction, and NYHA were not statistically significant. Results: Blood product use, including fresh frozen plasma (FFP) and homolgous blood transfusions was tracked through the operating theater and into the intensive care unit. In the mini bypass group, while no homologous blood transfusions were given in the OR, 27% of the patients received at least one unit of homolgous blood. In the control group, 43% of the patients received at least one unit of blood in the OR or in the ICU and there was a stastistically-significant 38% reduction in homologous blood product use (p = 0.05). For the patients who received homologous blood, there was also a significant reduction in transfused volume (0.53±0.90 units blood mini bypass vs 1.3±1.93 units conventional, p <0.05). In terms of FFP, there was also a stastistically significant difference between the two groups (0 units transfused in mini bypass group vs 3 patients receiving one unit FFP in the control group, p<0.001). Cumulative postoperative bleeding during the ICU stay was also evaluated, yielding a significant reduction (365±495 ml mini bypass vs 825± 975 ml conventional, p <0.05). Conclusion: Mini bypass reduces on-pump hemodilution and, therefore, donor blood usage in routine CABG patients as compared to conventional ECC circuits and can reduce postoperative bleeding as compared to a traditional system. The mini bypass system is safe in routine clinical use and can manage easily the same number of anastomoses as a traditional system and should be considered a favorable alternative to conventional ECC in all revascularization cases. Perfusion (2007) 22, 9-14.

Healthcare failure mode effect analysis of a miniaturized extracorporeal bypass circuit

BACKGROUND

The introduction of new and more advanced technology in healthcare occurs with an increasing speed. Therefore, more attention is needed for safety evaluation of new devices or techniques from an end-user perspective, especially when (inter-) national perfusion safety standards are lacking. A recently increased awareness of the safety risks as a consequence of technical or human error has provoked interest in optimisation of perfusion methodology and devices. To prevent or reduce the severity or likelihood of failures of new technology, 'failure mode effect analysis' is a proven proactive technique. When it is used as a qualitative analysis for possible hazards in patient treatment associated with the use of medical devices, it's called healthcare failure mode effect analysis (hFMEA).

METHODS

To evaluate the safety of the Extra Corporeal Circulation Optimized (ECCO, Sorin Group, Mirandola, Italy) miniaturized bypass circuit, hFMEA was used. A multi disciplinary team that consisted of two clinical perfusionists, a clinical physicist, a clinical physicist trainee and a technician has performed this analysis.

RESULTS

The hFMEA demonstrated that failure of the bubble sensor for the electric remote clamping system on the arterial line (Figure 1), activated by air passing the venous bubble trap, had the highest risk score of all failure modes. This has led to the implementation of an extra low-level sensor in the system to prevent air passing through into the centrifugal pump. The hFMEA has also indicated that extra individual simulation training is needed for handling critical failures during the use of the miniature bypass system.

CONCLUSION

Early identification of possible technology failures in any process or device can avoid adverse patient outcomes. The technique of hFMEA is a valuable tool in evaluating the use of high-risk apparatus, such as an extracorporeal bypass system, in patient treatment in order to increase patient safety.

Can minimized cardiopulmonary bypass systems be safer?

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.

Can a mini-bypass circuit improve perfusion in cardiac surgery compared to conventional cardiopulmonary bypass?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether the 'mini-bypass technique' can give a reduction in complications after cardiac surgery compared to the conventional cardiopulmonary bypass circuit. Altogether 144 papers were found using the reported search, of which 14 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We conclude that 10 out of these 14 studies show reduced hemodilution, 7 show reduced red blood cell transfusion, 2 show reduced fresh frozen plasma use (one showing increased use), and 2 show reduced platelet use. Three studies show reduced postoperative blood loss, but one shows increased blood loss. Three studies show better renal function. Four studies show a better cardiac index and 2 show shorter intensive care unit stay. One study found an increased minute volume and reduced oxygenation for one hour post-mini-bypass. Six studies find significantly reduced inflammatory markers, and 5 measure superior myocardial protection. There are several anecdotal references to a 'learning curve' with this technique but no significant morbidity with complications arising from this were found. Mini-bypass seems to be a promising technique with many documented benefits in studies reporting as many as 1000 patients undergoing this technique.