Minimizing Cardiopulmonary Bypass Attenuates Myocardial Damage After Cardiac Surgery

Impact of minimal invasive extracorporeal circulation on systemic inflammatory response - a randomized trial

BACKGROUND

Extracorporeal circulation causes a systemic inflammatory response, that may cause postoperative haemodynamic instability and end-organ dysfunction. This study aimed to investigate the impact of minimal invasive extracorporeal circulation (MiECC) on the systemic inflammatory response compared with conventional extracorporeal circulation (CECC).

METHODS

Patients undergoing coronary artery bypass grafting were randomized to MiECC (n = 30) and CECC (n = 30). Primary endpoint was tumor necrosis factor-α. Secondary endpoints were other biochemical markers of inflammation (IL1β, IL6 and IL8, C-reactive protein, leukocytes), and markers of inadequate tissue perfusion and tissue damage (lactate dehydrogenase, lactate and creatine kinase-MB). In addition, we registered signs of systemic inflammatory response syndrome, haemodynamic instability, atrial fibrillation, respiratory dysfunction, and infection.

RESULTS

Patients treated with MiECC showed significantly lower levels of tumor necrosis factor-α than CECC during and early after extracorporeal circulation (median: MiECC 3.4 pg/mL; CI 2.2-4.5 vs. CECC 4.6 pg/mL; CI 3.4-5.6; p = 0.01). Lower levels of creatine kinase-MB and lactate dehydrogenase suggested less tissue damage. However, we detected no other significant differences in any other markers of inflammation, tissue damage or in any of the clinical outcomes.

CONCLUSIONS

Lower levels of TNF-α after MiECC compared with CECC may reflect reduced inflammatory response, although other biochemical markers of inflammation were comparable. Our results suggest better end-organ protection with MiECC compared with CECC. Clinical parameters related to systemic inflammatory response were comparable in this study.

CLINICAL REGISTRATION NUMBER

NCT03216720.

Comparison of bubble removal performances of five membrane oxygenators with and without a pre-filter

When employing minimal invasive extracorporeal circulation (MiECC), the removal of bubbles in the circuit is important to prevent air embolism. We investigated the bubble removal performance of the FHP oxygenator with a pre-filter and compared it with that of four oxygenators, including the Fusion oxygenator, Quadrox oxygenator, Inspire oxygenator, and FX oxygenator. A closed test circuit filled with an aqueous glycerin solution was used. Air injection (10 mL) was performed prior to the oxygenator, and the number and volume of the bubbles were measured at the inlet and outlet of each oxygenator. At the inlet of the five oxygenators, there were no significant differences in the total number of bubbles detected. At the outlet, bubbles were classified into two groups according to the bubble size: ≥100 μm and <100 μm. Tests were performed at pump flow rates of 4 and 5 L/min. For bubbles ≥100 μm, which are considered clinically detrimental, the FHP was the lowest number and volume of bubbles at both pump flow rates compared to the other oxygenators. Regarding the bubbles <100 μm, the number of bubbles was higher in the FHP than those in others; however, the volume of bubbles was significantly lower at 4 L/min and tended to be lower at 5 L/min. The use of the FHP with the pre-filter removed more bubbles ≥100 μm in the circuit than that by the other oxygenators.

Conventional versus miniaturized cardiopulmonary bypass: A systematic review and meta-analysis

Objective

A meta-analysis of randomized controlled trials was performed to compare the effects of miniaturized extracorporeal circulation (MECC) and conventional extracorporeal circulation (CECC) on morbidity and mortality rates after cardiac surgery.

Methods

A comprehensive literature search was conducted using Ovid, PubMed, Medline, EMBASE, and the Cochrane databases. Randomized controlled trials from the year 2000 with n > 40 patients were considered. Key search terms included variations of "mini," "cardiopulmonary," "bypass," "extracorporeal," "perfusion," and "circuit." Studies were assessed for bias using the Cochrane Risk of Bias tool. The primary outcomes were postoperative mortality and stroke. Secondary outcomes included arrhythmia, myocardial infarction, renal failure, blood loss, and a composite outcome comprised of mortality, stroke, myocardial infarction and renal failure. Duration of intensive care unit, and hospital stay was also recorded.

Results

The 42 studies eligible for this study included a total of 2154 patients who underwent CECC and 2196 patients who underwent MECC. There were no significant differences in any preoperative or demographic characteristics. Compared with CECC, MECC did not reduce the incidence of mortality, stroke, myocardial infarction, and renal failure but did significantly decrease the composite of these outcomes (odds ratio, 0.64; 95% confidence interval [CI], 0.50-0.81; P = .0002). MECC was also associated with reductions in arrhythmia (odds ratio, 0.67; 95% CI, 0.54-0.83; P = .0003), blood loss (mean difference [MD], -96.37 mL; 95% CI, -152.70 to -40.05 mL; P = .0008), hospital stay (MD, -0.70 days; 95% CI, -1.21 to -0.20 days; P = .006), and intensive care unit stay (MD, -2.27 hours; 95% CI, -3.03 to -1.50 hours; P < .001).

Conclusions

MECC demonstrates clinical benefits compared with CECC. Further studies are required to perform a cost-utility analysis and to assess the long-term outcomes of MECC. These should use standardized definitions of endpoints such as mortality and renal failure to reduce inconsistency in outcome reporting.

Is there really a benefit of using minimized cardiopulmonary bypass in CABG? A retrospective propensity score-matched study with 5000 cases

The concept of minimized cardiopulmonary bypass targets at reduction of adverse effects triggered by extracorporeal circulation. In this study, benefits of minimized bypass in CABG were evaluated under particular consideration of patient body mass index and surgeon impact. From 2004 to 2014, 5164 patients underwent coronary bypass surgery (CABG). Conventional cardiopulmonary bypass (CCPB) was used in 2376 patients, minimized cardiopulmonary bypass (MCPB) in 2788 cases. Multivariate regression models were used in the entire cohort and in a propensity score-matched subgroup after expert CABG to figure out clinical differences such as mortality, postoperative renal function, and thromboembolic events. Overall mortality was 1.5% (n = 41) in the MCPB group and 3.5% (n = 82) in CCPB patients (p < 0.001). Postoperative renal failure and hemodialysis occurred in 2.6% (n = 72/MCPB) vs. 5.3% (n = 122/CCPB (p < 0.001). Multivariable regression revealed use of CCPB as risk factor for increased mortality (OR 2.01, p = 0.001), renal failure (OR 1.79, p < 0.001), and myocardial infarction (OR 1.98, p < 0.001) comparable to risk factors such as preoperative ventilation (OR 2.26, p = 0.048), diabetes mellitus (OR 1.68, p = 0.001), and cardiogenic shock (OR 3.81, p = 0.002). Body mass index had no effect on the analyzed outcome parameters (OR 0.92, p = 0.002). Propensity score-matching analysis of an expert CABG subgroup revealed CCPB as risk factor for mortality (OR 2.26, p = 0.004) and postoperative hemodialysis (OR 1.74, p = 0.017). Compared to conventional circuits, minimized bypass use in CABG is associated with lower mortality and less postoperative renal failure. A high body mass index is feasible and not a risk factor for MCPB surgery.

Type II Minimal-Invasive Extracorporeal Circuit for Aortic Valve Replacement: A Randomized Controlled Trial

Extracorporeal circulation triggers systemic inflammatory response and coagulation disorders which may lead to unfavorable clinical outcome. A type II minimally-invasive extracorporeal circuit (MiECC) is a closed system with markedly reduced artificial surface as compared to conventional extracorporeal circuits (CECC). The aim of this study was to investigate and compare inflammatory responses, complement activation and selected clinical end-points in isolated surgical aortic valve replacement (SAVR) performed with a type II MiECC circuit or a CECC. Fifty patients were prospectively randomized to MiECC or CECC perfusion regimen. Complement activation (sC5b-9), inflammation (IL-6, TNF-α, sCD40-ligand) and activation of the coagulation system (D-dimer, TAT-complex) were determined before operation, at 2 hours and 24 hours after surgery. Clinical end-points included perfusion time, transfusion of allogeneic blood products, postoperative bleeding, sepsis, new onset of atrial fibrillation, stroke and in-hospital mortality. Patient characteristics and baseline plasma markers were similar in both groups. Levels for sC5b-9, TNF-α, sCD40 ligand, TAT-complex and D-dimers were not significantly different between MiECC and CECC at 2 hours and 24 hours after surgery. The IL-6 plasma concentration was lower in the CECC group at 24 hours (P = 0.026, vs. MiECC). Comparisons of the baseline level to values at 2 hours and 24 hours, adjusted for the type of oxygenator and hemoglobin, showed a significantly lower sC5b-9 in MiECC at 2 hours (P = 0.013), but no difference at 24 hours (P=0.990). Compared with CECC, MiECC patients had a shorter perfusion time (P = 0.037) and less transfusion requirements (P = 0.04). In this selected cohort of SAVR patients, the type II MiECC was not inferior to CECC in terms of inflammatory response and complement activation. Thus, MiECC might be an alternative perfusion strategy to conventional.

Impact of minimally invasive extracorporeal circuits on octogenarians undergoing coronary artery bypass grafting. Have we been looking in the wrong direction?

OBJECTIVES

Minimally invasive extracorporeal circuits (MiECCs) aim at the preservation of physiologic reserves, the impact of which is expected to be most evident in patients in whom these are depleted. In this context, octogenarians present a subpopulation of specific interest.

METHODS

Based on the type of the utilized ECC, we performed a retrospective comparison between all octogenarians (n = 324) who received a primary coronary artery bypass in our institution from 2003 until 2010.

RESULTS

An MiECC was used in 52% of patients. Preoperative variables showed that the MiECC patients were older (83 ± 2 vs 82 ± 2 years; P = 0.001), had higher incidence of renal dysfunction (8% vs 3%; P = 0.04), moderately reduced left ventricular function (43 vs 33%; P = 0.07) and lower incidence of unstable angina (20% vs 28%; P = 0.06). To overcome these differences, a propensity score matching was performed and yielded 126 matched pairs of patients. The overall transfusion of packed red blood cells (2.3 ± 2.3 vs 3.4 ± 3.2 units per patint; P = <0.001), the rate of low cardiac output (0% vs 6%; P = 0.01) and the 30-day postoperative mortality (2.4% vs 9.5%; P = 0.02) were all in favour of the MiECC group in the matched patient population.

CONCLUSIONS

The MiECC concept has shown its benefits regarding both morbidity and mortality in this high-risk patient population. We believe that this beneficial effect finds its reason in a better preservation of physiologic reserves that are essential for a positive outcome in this patient group.

Cardiopulmonary Bypass with Low- Versus High-Priming Volume: Comparison of Inflammatory Responses in a Rat Model

A cardiopulmonary bypass (CPB) can preserve life. However, interactions between blood and large artificial surfaces might help to provoke a series of chain reactions during CPB that result in the formation and release of numerous powerful inflammatory mediators including hormones and autacoids. We postulated that small CPB circuits with reduced priming volumes and less surface areas that come into contact with blood would attenuate systemic inflammatory responses by reducing the levels of cytokines and organ tissue damage during CPB. Rats were assigned to groups that underwent CPB with a high priming volume (PV) of 15 ml and a surface area of 0.044 m or a low PV of 7 ml and a surface area of 0.034 m. We measured serum levels of cytokines and biochemical markers during CPB. Levels of proinflammatory cytokines and biochemical markers were significantly elevated in the group with a high PV, than low PV at 60 min, whereas none of these factors significantly differed between the groups at 120 min. These data suggested that in addition to blood being in contact with surfaces, the duration of CPB exposure is also an important factor for nonlinear time variances in damage caused by the systemic inflammatory response.

Use of minimal invasive extracorporeal circulation in cardiac surgery: principles, definitions and potential benefits. A position paper from the Minimal invasive Extra-Corporeal Technologies international Society (MiECTiS)

Minimal invasive extracorporeal circulation (MiECC) systems have initiated important efforts within science and technology to further improve the biocompatibility of cardiopulmonary bypass components to minimize the adverse effects and improve end-organ protection. The Minimal invasive Extra-Corporeal Technologies international Society was founded to create an international forum for the exchange of ideas on clinical application and research of minimal invasive extracorporeal circulation technology. The present work is a consensus document developed to standardize the terminology and the definition of minimal invasive extracorporeal circulation technology as well as to provide recommendations for the clinical practice. The goal of this manuscript is to promote the use of MiECC systems into clinical practice as a multidisciplinary strategy involving cardiac surgeons, anaesthesiologists and perfusionists.

Versatile minimized system--a step towards safe perfusion

A growing body of evidence indicates the superiority of minimized cardiopulmonary bypass (CPB) systems compared to conventional systems in terms of inflammatory reactions and transfusion requirements. Evident benefits of minimized CPB systems, however, do not come without consequences. Kinetic-assisted drainage, as used in these circuits, can result in severe fluctuations of venous line pressures and, consequently, fluctuation of the blood flow delivered to the patient. Furthermore, subatmospheric venous line pressures can cause gaseous microemboli. Another limitation is the absence of cardiotomy suction, which can lead to excessive blood loss via a cell saver. The most serious limitation of minimized circuits is that these circuits are very constrained in the case of complications or changing of the surgery plan. We developed a versatile minimized system (VMS) with a priming volume of about 600 ml. A compliance chamber in the venous line decreases peaks of pressure fluctuations. This chamber also acts as a bubble trap. Additionally, the open venous reservoir is connected parallel to the venous line and excluded from the circulation during an uncomplicated CPB. This reservoir can be included in the circulation via a roller pump and be used as a cardiotomy reservoir. The amount and rate of returned blood in the circulation is regulated by a movable level detector. Further, the circuit can easily be converted to an open system with vacuum-assisted venous drainage in the case of unexpected complications. The VMS combines the benefits of minimized circuits with the versatility and safety of a conventional CPB system. Perfusionists familiar with this system can secure an adequate and timely response at expected and unexpected intraoperative complications.

What We have Learned about Minimized Extracorporeal Circulation versus Conventional Extracorporeal Circulation: An Updated Meta-Analysis

Introduction

The benefits of minimized extracorporeal circulation (MECC) compared with conventional extracorporeal circulation (CECC) are still in debate.

Methods

PubMed, EMBASE and the Cochrane Library were searched until November 10, 2014. After quality assessment, we chose a fixed-effects model when the trials showed low heterogeneity, otherwise a random-effects model was used. We performed univariate meta-regression and sensitivity analysis to search for the potential sources of heterogeneity. Cumulative meta-analysis was performed to access the evolution of outcome over time.

Results

41 RCTs enrolling 3744 patients were included after independent article review by 2 authors. MECC significantly reduced atrial fibrillation (RR, 0.76; 95% CI, 0.66 to 0.89; P<0.001; I2 = 0%), and myocardial infarction (RR, 0.43; 95% CI, 0.26 to 0.71; P = 0.001; I2 = 0%). In addition, the results regarding chest tube drainage, transfusion rate, blood loss, red blood cell transfusion volume, and platelet count favored MECC as well.

Conclusions

MECC diminished morbidity of cardiovascular complications postoperatively, conserved blood cells, and reduced allogeneic blood transfusion.

Inflammation, oxidative stress and postoperative atrial fibrillation in cardiac surgery

Postoperative atrial fibrillation (POAF) is a common complication of cardiac surgery that occurs in up to 60% of patients. POAF is associated with increased risk of cardiovascular mortality, stroke and other arrhythmias that can impact on early and long term clinical outcomes and health economics. Many factors such as disease-induced cardiac remodelling, operative trauma, changes in atrial pressure and chemical stimulation and reflex sympathetic/parasympathetic activation have been implicated in the development of POAF. There is mounting evidence to support a major role for inflammation and oxidative stress in the pathogenesis of POAF. Both are consequences of using cardiopulmonary bypass and reperfusion following ischaemic cardioplegic arrest. Subsequently, several anti-inflammatory and antioxidant drugs have been tested in an attempt to reduce the incidence of POAF. However, prevention remains suboptimal and thus far none of the tested drugs has provided sufficient efficacy to be widely introduced in clinical practice. A better understanding of the cellular and molecular mechanisms responsible for the onset and persistence of POAF is needed to develop more effective prediction and interventions.

Impact of age on early outcome after coronary bypass graft surgery using minimized versus conventional extracorporeal circulation

Background

Objective of this study was to evaluate the impact of age on comparative early outcomes after coronary artery bypass graft surgery (CABG) with minimized (MECC) and conventional extracorporeal circulation (CECC).

Methods

A retrospective age-, gender- and operation-matched cohort analysis between January 2005 and December 2010 with a total of 2274 patients undergoing CABG with MECC (n = 1137; 50%) or CECC was performed. Patients were stratified into 4 groups according to age: <59 years, 60–69 years, 70–79 years, and 80 years of age or older. Outcomes were compared within each age group. Patients with preoperative dialysis were excluded from analysis. Primary endpoint was 30-day mortality.

Results

Patients treated with CECC had a significantly higher mean logistic EuroSCORE (6.3% vs. 5.0%; p < 0.001), a slightly lower rate of preoperative myocardial infarction (46% vs. 51%; p = 0.01) and a higher rate of impaired renal function (eGFR < 60 mL/min/1.73 m2: 24% vs. 20%; p = 0.01) compared to MECC-patients. Left internal mammary artery was significantly used more often in MECC patients (93% vs. 86%; p < 0.001). Cardiopulmonary bypass and aortic-cross clamping time were significantly lower in the MECC group (p < 0.001). Overall 30-day mortality was significantly higher in patients treated with CECC (4.4% vs. 2.2%; p = 0.002). Within the different age groups mortality rates were not significantly different except for patients aged 60–69 years (4.5% vs. 1.8%; p = 0.03). Postoperative requirement of renal replacement therapy (4% vs. 2.2%; p = 0.01), respiratory insufficiency (9.9% vs. 6.6%; P = 0.004) and incidence of low cardiac output syndrome (3% vs. 1.2%; p = 0.003) were significantly increased in patients with CECC. Multivariate analysis identified age (p = 0.005; 95% CI 1.01 to 1.08; OR 1.05) among other parameters as an independent risk factor, whereas conventional extracorporeal circulation itself did not present as an independent risk factor for 30-day mortality.

Conclusions

In this matched study sample early outcome was significantly better in patients with MECC compared to CECC, irrespective of age. Prior myocardial infarction estimated GFR < 60 mL and waiving the use of LIMA were independent risk factors for 30-day mortality, which were more present in the CECC group.

Metabolic derangement and cardiac injury early after reperfusion following intermittent cross-clamp fibrillation in patients undergoing coronary artery bypass graft surgery using conventional or miniaturized cardiopulmonary bypass

Myocardial ischemic stress and early reperfusion injury in patients undergoing coronary artery bypass grafting (CABG) operated on using intermittent cross-clamp fibrillation (ICCF) are not presently known. The role of mini-cardiopulmonary bypass (mCPB) versus conventional CPB (cCPB) during ICCF has not been investigated. These issues have been addressed as secondary objective of randomised controlled trial (ISRCTN30610605) comparing cCPB and mCPB. Twenty-six patients undergoing primary elective CABG using ICCF were randomised to either cCPB or mCPB. Paired left ventricular biopsies collected from 21 patients at the beginning and at the end of CPB were used to measure intracellular substrates (ATP and related compounds). Cardiac troponin T (cTnT) and CK-MB levels were measured in plasma collected from all patients preoperatively and after 1, 30, 60, 120, and 300 min after institution of CPB. ICCF was associated with significant ischemic stress as seen by fall in energy-rich phosphates early after reperfusion. There was also a fall in nicotinamide adenine dinucleotide (NAD(+)) indicating cardiomyocyte death which was confirmed by early release of cTnT and CK-MB during CPB. Ischemic stress and early myocardial injury were similar for cCPB and mCPB. However, the overall cardiac injury was significantly lower in the mCPB group as measured by cTnT (mean ± SEM: 96 ± 14 vs. 59 ± 8 µg/l, p = 0.02), but not with CK-MB. ICCF is associated with significant metabolic derangement and early myocardial injury. This early outcome was not affected by the CPB technique. However, the overall cardiac injury was lower for mCPB only when measured using cTnT.

Impact of closed minimal extracorporeal circulation on microvascular tissue perfusion during surgical aortic valve replacement: intravital imaging in a prospective randomized study

OBJECTIVES

Closed minimal extracorporeal circulation (MECC) systems currently do not represent the standard of surgical care for open-heart surgery. Yet, considering the beneficial results reported for coronary artery bypass graft (CABG) surgery, we used an MECC system in aortic valve replacement (AVR) and analysed the effects on intraoperative microvascular perfusion in comparison with conventional open extracorporeal circulation (CECC).

METHODS

In the current study, we analysed alterations in microvascular perfusion at 4 predefined time points (T1-T4) during surgical AVR utilizing orthogonal polarization spectral (OPS) imaging. Twenty patients were randomized for being operated on utilizing either MECC or CECC. Changes in functional capillary density (FCD, cm/cm(2)), mircovascular blood flow velocity (mm/s) and vessel diameter (μm) were analysed by a blinded investigator.

RESULTS

After the start of extracorporeal circulation and aortic cross-clamping (T2), both groups showed a significant drop in FCD, but with a significantly higher FCD in the MECC group (153.1 ± 15.0 cm/cm² in the CECC group vs 160.8 ± 12.2 cm/cm² in the MECC group, P = 0.034). During the late phase of the cardiopulmonary bypass (CPB) (T3), the FCD was still significantly depressed in both treatment groups (153.5 ± 14.6 cm/cm² in the CECC group, P <0.05 vs 'T1'; 159.5 ± 12.4 cm/cm² in the MECC group, P <0.05 versus 'T1'). After termination of CPB (T4), the FCD recovered in both groups to baseline values. Microvascular blood flow velocity tended to remain at a higher level in the MECC group, whereas haemodilution during CPB was significantly reduced in the MECC group.

CONCLUSIONS

The use of MECC in AVR did not affect procedural safety and, resulted in beneficial preservation of microvascular blood flow velocity and significantly reduced haemodilution during CPB. In contrast to CABG surgery, the use of MECC did not improve FCD during surgical AVR. Clinical advantages possibly resulting from attenuated haemodilution and preservation of microvascular blood flow velocity require further validation in larger patient cohorts.

Impact of minimized extracorporeal circulation on outcome in patients with preoperative anemia undergoing coronary artery bypass surgery

Preoperative anemia and low hematocrit during cardiopulmonary bypass have been associated with worse outcome in patients undergoing cardiac surgery. The minimized extracorporeal circulation (MECC) allows a reduction of the negative effects associated with conventional extracorporeal circulation (CECC). In this study, the impact of the MECC on outcome of anemic patients after coronary artery bypass grafting (CABG) was assessed. Between January 2004 and December 2011, 1,945 consecutive patients with preoperative anemia underwent isolated CABG using CECC (44.8%) or MECC (55.2%). The cutoff point for anemia was 13 g/dl for men and 12 g/dl for women. The postoperative creatine kinase and lactate levels were significantly lower in the MECC group (p < 0.001). There was no difference in postoperative blood loss between the groups. However, the intraoperative and postoperative transfusion requirements were significantly lower in the MECC group (p < 0.05). Furthermore, MECC patients had lower incidences of postoperative acute renal failure, and low cardiac output syndrome, shorter intensive care unit lengths of stay and reduced 30-day mortality (p < 0.05). In conclusion, a reduced postoperative mortality, lower transfusion requirements, and less renal and myocardial damage encourage the use of MECC for CABG, especially in the specific high-risk subgroup of patients with anemia.

Anti-inflammatory strategies to reduce acute kidney injury in cardiac surgery patients: a meta-analysis of randomized controlled trials

Acute kidney injury (AKI) after cardiac operations is a serious complication associated with postoperative mortality. Multiple factors contribute to AKI development, principally ischemia-reperfusion injury and inflammatory response. It is well proven that glucocorticoid administration, leukocyte filter application, and miniaturized extracorporeal circuits (MECC) modulate inflammatory response. We conducted a systematic review of randomized controlled trials (RCTs) in which one of these inflammatory system modulation strategies was used, with the aim to evaluate the effects on postoperative AKI. MEDLINE and Cochrane Library were screened through November 2011 for RCTs in which an inflammatory system modulation strategy was adopted. Included were trials that reported data about postoperative renal outcomes. Because AKI was defined by different criteria, including biochemical determinations, urine output, or dialysis requirement, we unified renal outcome as worsening renal function (WRF). We identified 14 trials for steroids administration (931 patients, WRF incidence [treatment vs. placebo]: 2.7% vs. 2.4%; OR: 1.13; 95% CI: 0.53-2.43; P = 0.79), 9 trials for MECC (947 patients, WRF incidence: 2.4% vs. 0.9%; OR: 0.47; 95% CI: 0.18-1.25; P = 0.13), 6 trials for leukocyte filters (374 patients, WRF incidence: 1.1% vs. 7.5%; OR: 0.18; 95% CI: 0.05-0.64; P = 0.008). Only leukocyte filters effectively reduced WRF incidence. Not all cardiopulmonary bypass-related anti-inflammatory strategies analyzed reduced renal damage after cardiac operations. In adult patients, probably other factors are predominant on inflammation in determining AKI, and only leukocyte filters were effective. Large multicenter RCTs are needed in order to better evaluate the role of inflammation in AKI development after cardiac operations.

Obstacles in haemocompatibility testing

ISO 10993-4 is an international standard describing the methods of testing of medical devices for interactions with blood for regulatory purpose. The complexity of blood responses to biomaterial surfaces and the variability of blood functions in different individuals and species pose difficulties in standardisation. Moreover, in vivo or in vitro testing, as well as the clinical relevance of certain findings, is still matter of debate. This review deals with the major remaining problems, including a brief explanation of surface interactions with blood, the current ISO 10993 requirements for testing, and the role of in vitro test models. The literature is reviewed on anticoagulation, shear rate, blood-air interfaces, incubation time, and the importance of evaluation of the surface area after blood contact. Two test categories deserve further attention: complement and platelet function, including the effects on platelets from adhesion proteins, venipuncture, and animal derived- blood. The material properties, hydrophilicity, and roughness, as well as reference materials, are discussed. Finally this review calls for completing the acceptance criteria in the ISO standard based on a panel of test results.

Minimal extracorporeal circulation reduces the incidence of postoperative major adverse events after elective coronary artery bypass grafting in high-risk patients. A single-institutional prospective randomized study

Coronary artery bypass grafting (CABG) using minimal extracorporeal circulation (MECC) has been associated with an improved short-term clinical outcome compared to conventional extracorporeal circulation (CECC). The aim of this study was to evaluate the impact of MECC compared to CECC on postoperative major adverse events in high-risk patients undergoing elective coronary revascularization procedures. Two hundred patients undergoing elective CABG were randomized into two groups. In Group A (n=100), MECC was used while Group B (n=100) included patients who were operated on CECC. The incidence of postoperative major adverse events (myocardial infarction, renal failure, stroke, death) was the primary end-point of the study. MECC was associated with a 77% relative risk reduction in the incidence of major adverse events compared to CECC (p=0.004). The rate of major adverse events occurring in the high-risk patient subgroup (preoperative left ventricular ejection fraction ≤40%, age >65 years, EuroSCORE II >5) operated on with MECC was significantly lower in comparison to their CECC counterparts. Based on our results, cardiac centres should be encouraged to use MECC as the standard circuit when performing elective coronary procedures, even in a high-risk population.

Are minimized perfusion circuits the better heart lung machines? Final results of a prospective randomized multicentre study

Introduction: Minimized perfusion circuits (MPCs), although aiming at minimizing the adverse effects of cardiopulmonary bypass, have not yet gained popularity. This can be attributed to concerns regarding their safety, as well as lack of sufficient evidence of their benefit.

Methods: Described is a randomized, multicentre study comparing the MPC - ROCsafeRX to standard cardiopulmonary bypass in patients undergoing elective coronary artery bypass grafting and/ or aortic valve replacement.

Results: Five hundred patients were included in the study (252 randomized to the ROCsafeRX group and 248 to standard cardiopulmonary bypass). Both groups were well matched for demographic characteristics and type of surgery. No operative mortality and no device-related complications were encountered.

Transfusion requirement (333 ± 603 vs. 587 ± 1010 ml; p=0.001), incidence of atrial fibrillation (16.3% vs. 24.2%; p=0.03) and the incidence of major adverse events (9.1% vs. 16.5%; p=0.02) were all in favour of the MPC group.

Conclusion: These results confirm both the safety and efficacy of the ROCsafeRX MPC for a large variety of cardiac patients. Minimized perfusion circuits should, therefore, play a greater role in daily practice so that as many patients as possible can benefit from their advantages.

Prospective, Randomized Study Comparing Two Different Minimized versus Conventional Cardiopulmonary Bypass Systems

Objective

Conventional cardiopulmonary bypass (CCPB) is a major trigger of inflammatory response. We aimed to assess the impact of two different minimized cardiopulmonary bypass systems (mini-CPB) with and without Bioline-coating compared with CCPB regarding organ function, inflammatory response, and early clinical outcome.

Methods

In a prospective, randomized study, 120 patients underwent elective coronary artery bypass grafting and were randomized into three groups: mini-CPB using a Bioline-coated (group A, n = 40) or an uncoated (group B, n = 40) circuit, or CCPB (group C, n = 40). Cytokines (interleukin-6, interleukin-8, and tumor necrosis factor-alpha), myocardial markers (creatine kinase [CK], CK-MB, and troponin-T), hematocrit, and platelet counts were measured up to 48 hours postoperatively. Early clinical outcome was assessed at 3 months postoperatively.

Results

Demographics, number of distal anastomoses, ventilation time, blood loss, intensive care unit, and hospital stay were comparable (P = not significant). Extracorporeal circulation and cross-clamp time were significantly longer in group A and B versus C (P < 0.005). No significant differences could be found in the release of interleukin-6, interleukin-8, and tumor necrosis factor-alpha among groups. Myocardial markers were significantly reduced in group A and B versus group C (P < 0.001). Hematocrit and platelet counts did not differ among the groups. No differences could be found in early clinical outcome up to 3 months.

Conclusions

This study showed significant better myocardial preservation with lower CK-MB and troponin-T levels in both mini-CPB groups. No significant differences could be found in terms of inflammation, hematologic effects, and early clinical outcome.

Mini extracorporeal circuit cardiopulmonary bypass system: a review

Improved knowledge of the pathophysiological processes experienced in response to cardiopulmonary bypass has led to new developments in extracorporeal technology and understanding. The use of mini extracorporeal circuits (MECC) is rapidly expanding in clinical practice. The mini extracorporeal circuit differs by a greatly reduced tubing length and the number of components when compared with current circuit designs. The MECC is believed to offer potential benefits to the surgical patient by reducing the systemic inflammatory response that remains strongly implicated in post-operative organ dysfunction. We present a review of the available literature and find the MECC to show an acceptable safety profile with a reduction in post-operative complications and transfusion requirements and no evidence of any negative impairment to the surgeon, anaesthetist or perfusionist. The observed post-bypass inflammatory response is seen to be lower after MECC bypass and this is of clear clinical benefit.

The inflammatory response to miniaturised extracorporeal circulation: a review of the literature

Conventional cardiopulmonary bypass can trigger a systemic inflammatory response syndrome similar to sepsis. Aetiological factors include surgical trauma, reperfusion injury, and, most importantly, contact of the blood with the synthetic surfaces of the heart-lung machine. Recently, a new cardiopulmonary bypass system, mini-extracorporeal circulation (MECC), has been developed and has shown promising early results in terms of reducing this inflammatory response. It has no venous reservoir, a reduced priming volume, and less blood-synthetic interface. This review focuses on the inflammatory and clinical outcomes of using MECC and compares these to conventional cardio-pulmonary bypass (CCPB). MECC has been shown to reduce postoperative cytokines levels and other markers of inflammation. In addition, MECC reduces organ damage, postoperative complications and the need for blood transfusion. MECC is a safe and viable perfusion option and in certain circumstances it is superior to CCPB.

Minimized extracorporeal circulation cannot prevent acute kidney injury but attenuates early renal dysfunction after coronary bypass grafting

We studied the impact of minimized extracorporeal circulation (MECC) on acute kidney injury (AKI) after coronary bypass grafting. A retrospective, observational study with 1,685 patients with MECC and 3,046 patients with conventional bypass was done. Primary outcome was AKI defined as a decline > or = 50% in estimated glomerular filtration rate (eGFR) within 48 hours after surgery. Secondary outcome was temporary dialysis. MECC exerts beneficial hemodynamic effects but does not prevent AKI. Fewer patients developed a decline in eGFR <60 mL/min/1.73 m(2) (MECC) compared with conventional extracorporeal circulation (ECC) (30.7% versus 45.5%, p < 0.001). The incidence of eGFR decrease by > or = 50% did not differ (1.8% versus 2.7%, p = 0.20). Temporary dialysis was required in 61 patients with ECC (2%) and in 16 patients with MECC (0.9%, p < 0.001). A preoperative eGFR <60 mL/min/1.73 m(2) increased in both groups the risk for mortality compared with patients with an eGFR >60 mL/min/1.73 m(2) (ECC: odds ratio 3.6, 95% confidence interval 2.6-4.9; MECC: odds ratio 4.9, 95% confidence interval 2.8-8.6). MECC is renoprotective in the early postoperative period but cannot prevent AKI. An impaired preoperative eGFR increases the risk for mortality irrespective of the cardiopulmonary bypass system used.

Outcome after coronary artery bypass surgery with miniaturized versus conventional cardiopulmonary bypass

We have reviewed the results of our experience with the use of miniaturized (Mini-CPB) versus conventional (C-CPB) cardiopulmonary bypass in coronary artery bypass surgery (CABG). This study included 365 patients who underwent CABG with C-CPB and 101 patients with Mini-CPB. In-hospital mortality was lower in the C-CPB group (1.4% vs. 3.0%, P = 0.38). A better, but not statistically significant, immediate outcome was observed in the C-CPB group as indicated by a shorter length of stay in the intensive care unit as well as a lower incidence of combined adverse end-point. However, this was probably due to significantly higher operative risk in the Mini-CPB group (logistic EuroSCORE: 8.5 ± 10.0 vs. 4.6 ± 7.1, P < 0.0001). Seventy-seven propensity score-matched pairs had similar immediate postoperative results after Mini-CPB and C-CPB (30-day mortality: 1.3% vs. 1.3%; stroke: 0% vs. 0%; intensive care unit stay ≥5 days: 6.5% vs. 9.1%; combined adverse events: 14.3% vs. 11.7%). Mini-CPB achieves similar results to C-CPB in patients undergoing isolated CABG. The potential efficacy of Mini-CPB is expected to be more evident in high-risk patients or in complex cardiac surgery requiring much longer cardiopulmonary perfusion.

The effect of hemodilution during normothermic cardiac surgery on renal physiology and function: a review

Although the definitions of renal dysfunction vary, loss of renal function is a common complication following cardiac surgery using cardiopulmonary bypass (CPB). When postoperative dialysis is required, mortality is approximately 50%. CPB-accompanied hemodilution is a major contributing factor to renal damage as it notably reduces oxygen delivery by reducing the oxygen transport capacity of the blood as well as disturbing the microcirculation. To minimize hypoxemic damage during CPB, lowering of body temperature is applied to reduce the patient’s metabolic rate. At present, however, temperature management during elective adult cardiac surgery is shifting from moderate hypothermia to normothermia. To determine whether the currently accepted levels of hemodilution during CPB can suffice the normothermic patient’s high oxygen demand, we focused this study on renal physiology and postoperative renal function. Hemodilution reduces the capillary density through a diminished capillary viscosity, thereby, redistributing blood from the renal medulla to the renal cortex. As the physiology of the renal medulla makes it a hypoxic environment, this part of the kidney appears to be especially at risk for hypoxic damage caused by a hemodilution-induced lowered oxygen transport and oxygen delivery. In addition, hemodilution is also likely to disturb the hormonal systems regulating renal blood distribution. Clinical studies, mostly of retrospective or observational nature, show that perioperative nadir hematocrit levels lower than approximately 24% are associated with an increased risk to develop postoperative renal failure. A better comprehension of the cause-and-effect relation between low perioperative hematocrits and loss of postoperative renal function may enable more effective renal protective strategies.

The effect of preprocessing stored red blood cells on neonates undergoing corrective cardiac surgery

This study compared the effect of unprocessed and processed packed red blood cells (PRBCs) with the continuous autotransfusion system (CATS) during neonate heart surgery. Sixteen neonatal patients undergoing cardiac surgery were randomly divided into two groups: unprocessed PRBC (C group, n = 8); processed PRBC (P group, n = 8). The CATS was employed perioperatively. Series laboratory and clinical parameters, including levels of hematocrit, blood potassium, blood glucose, blood lactate, acid-base, and total priming volume of PRBC, were used to compare the effect between the two groups. Before CPB, the hematocrit of processed PRBCs in P group was significantly higher than those in C group (p < 0.01), and the concentrations of potassium, blood glucose, and lactate of processed PRBCs in P group were significantly lower than those in C group (p < 0.01). At the beginning and the end of CPB, the hematocrit levels in P group were all higher than those in C group (p < 0.05); lactate levels in P group were significantly lower than those in C group at the beginning of CPB (p < 0.01), and lower than that of C group at the end of CPB (p < 0.05). The total priming of PRBCs in P group was significantly less than that in C group (p < 0.01). Perioperative processing with CATS provided a high-quality RBC concentration, decreased the total priming of PRBCs, providing increased high-quality blood salvage during neonatal CPB procedure.