Four years' experience with a miniaturized extracorporeal circulation system and its influence on clinical outcome

Feasibility of mitral valve surgery using minimal extracorporeal circulation

AIM

Using minimal extracorporeal circulation (MECC) in isolated coronary artery bypass grafting or aortic valve replacement has been proven to be safe, feasible and superior compared to standard cardiopulmonary bypass (CPB) in terms of postoperative complications, total hospital stay and blood product transfusions. This feasibility study evaluates the clinical outcomes of mitral valve surgery performed with MECC.

METHODS

From March 2006 to January 2011, seventy-five patients who underwent mitral valve surgery performed with MECC (n=75) in our institution were retrospectively evaluated. Demographic characteristics, operative data and clinical outcomes were collected in a prospectively designed database.

RESULTS

The mean age was 68.8 ± 10.2 years with a EuroSCORE of 7.0 ± 2.3. Thirty-seven patients had a moderate left ventricular function (with a range of 30-40%). All patients except two had severe mitral valve incompetence (MI). Surgery was successful in all procedures. The mean duration of surgery was 210 ± 44 min (range 118-356 min). The mean CPB time was 128 ± 30 (range 67-249) min. The cross-clamp time was 99 ± 26 (range 48-205) min. There were no intraoperative perfusion problems or airlocks reported. The mean intensive care unit (ICU) length of stay was two days. Subsequent analysis showed a first postoperative haemoglobin value of 9.4 g/dL ± 1.7. There were no peroperative neurological complications. One patient developed an ischaemic cerebrovascular accident (CVA) on the forth postoperative day due to inadequate anticoagulation. Other postoperative complications included eight patients with pneumonia, one superficial wound infection, temporary renal insufficiency in two patients and four patients needed re-exploration for excessive postoperative leakage. Overall in-hospital mortality was four percent.

CONCLUSION

Our results show, for the first time, that isolated or combined mitral valve surgery using MECC is feasible and safe.

Reduced 30-day mortality in men after elective coronary artery bypass surgery with minimized extracorporeal circulation-a propensity score analysis

Background

Impact of minimized extracorporeal circulation (MECC) for coronary surgery on mortality remains controversial and gender significantly influence outcome.

Methods

We analyzed 3,139 male patients undergoing elective coronary surgery between 01/2004 and 05/2009. Using propensity score matching after binary logistic regression, 1,005 patients (from 1,119 patients) undergoing surgery with MECC could be matched with 1,005 patients (from 2,020 patients) undergoing surgery with conventional extracorporeal circulation (CECC). Primary outcome was 30-day mortality.

Results

Unadjusted 30-day mortality was 2.7% in patients with CECC and 0.8% in those with MECC (mean difference -1.9%; p < 0.001). The adjusted mean difference (average treatment effect of the treated) after matching was -1.5% (95% confidence interval (CI) -2.6 to -0.4; p = 0.006). Postoperative hospital stay was shorter in patients operated with minimized systems (adjusted mean difference -0.8 days; 95% CI -1.46 to -0.09; p = 0.03) and incidence of postoperative neurocognitive dysfunction was also lower (adjusted mean difference -1.3%; 95% CI -2.2 to -0.4; p = 0.001). Chest tube drainage (adjusted mean difference +22 mL; 95% CI -47 to 91; p = 0.5) and risk for acute kidney injury, kidney injury and failure according to RIFLE criteria (adjusted mean difference -1.0%; 95% CI -2.5 to 0.6; p = 0.24) proved to be insignificant between both groups. Apart from reduced 30-day mortality, however, average treatment effects for intensive care unit stay, postoperative hospital stay, chest tube drainage and kidney injury did not significantly differ.

Conclusion

Using propensity score analysis, we observed an association between MECC and reduced 30-day mortality in men, but our results call for further analysis.

Gender's impact on outcome in coronary surgery with minimized extracorporeal circulation

BACKGROUND

The role of female gender in cardiac surgery is still controversial. We examined the impact of gender on mortality after coronary artery bypass grafting (CABG) with minimized extracorporeal circulation (MECC).

METHODS

Between January 2004 and May 2009, 1,662 patients (439 females, 1,223 males) underwent CABG with MECC at the University Medical Center Regensburg. Perioperative data were retrospectively analyzed; primary end point was in-hospital mortality.

RESULTS

At operation, women were older, had a higher prevalence of diabetes and impaired renal function, and underwent more often non-elective surgery. Unadjusted mortality was significantly lower for men and than for women (2.3 vs. 5.7%; p = 0.001). Risk-adjusted mortality rates were derived by stepwise logistic regression. The final model reduced the gender-related mortality gap from 147 to 32%. Goodness of fit and discriminatory performance (AUC = 0.83) were good. Female gender, however, could not be identified as an independent risk factor for adverse outcome (OR 1.6; 95% CI 0.8-3.4). Risk-adjusted mortality was calculated as 4.9% in females and 2.6% in males. Low body surface area (<1.66 m(2)) was associated with excess mortality in females.

CONCLUSIONS

Gender-related disparity in outcome still remains present after surgery with minimized extracorporeal circulation. However, female gender per se is not an independent risk factor for in-hospital mortality, but close attention should be paid on modifiable risk factors.

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.

J-shaped versus median sternotomy for aortic valve replacement with minimal extracorporeal circuit

OBJECTIVES

Minimal access aortic valve replacement (AVR) has been demonstrated to have beneficial effects over median sternotomy. Minimal extracorporeal circulation (MECC) has been shown to have less deleterious effects than conventional cardiopulmonary bypass. We describe for the first time AVR via upper J-shaped partial sternotomy compared to median sternotomy using MECC.

METHODS

Prospectively collected pre-operative, intra-operative, post-operative and follow-up data from 104 consecutive patients who underwent minimal access AVR were compared to 72 consecutive patients undergoing median sternotomy using MECC during the same period (January 2007 to December 2009).

RESULTS

No significant differences were found in patient's characteristics or intra-operative data with the exception of pre-existing pulmonary disease. The mean cardiopulmonary bypass (86 ± 18 min vs. 78 ± 15 min, p = 0.0079) and cross-clamp times (65 ± 13 min vs. 59 ± 12 min, p = 0.0013) were significantly shorter in the median sternotomy group. Mediastinal blood loss (397 ± 257 ml vs. 614 ± 339 ml, p < 0.0001) and ventilation time (8 ± 6.9 h vs. 11 ± 16.5 h, p = 0.0054) were significantly less in the minimal access group. No differences were seen in transfusion requirements, inotropic support, intensive care unit (ICU) stay, total hospital stay, post-operative haemoglobin drop, major events or mortality. Quality of life scores after discharge demonstrated less pain with a quicker recovery and return to daily activities in patients receiving J-shaped sternotomy.

CONCLUSIONS

Minimal access AVR using MECC is feasible and provides excellent clinical results. Less pain and quicker recovery was experienced among patients in this group.

Management of intraoperative fluid balance and blood conservation techniques in adult cardiac surgery

Blood transfusions are associated with adverse physiologic effects and increased cost, and therefore reduction of blood product use during surgery is a desirable goal for all patients. Cardiac surgery is a major consumer of donor blood products, especially when cardiopulmonary bypass (CPB) is used, because hematocrit drops precipitously during CPB due to blood loss and blood cell dilution. Advanced age, low preoperative red blood cell volume (preoperative anemia or small body size), preoperative antiplatelet or antithrombotic drugs, complex or re-operative procedures or emergency operations, and patient comorbidities were identified as important transfusion risk indicators in a report recently published by the Society of Cardiovascular Anesthesiologists. This report also identified several pre- and intraoperative interventions that may help reduce blood transfusions, including off-pump procedures, preoperative autologous blood donation, normovolemic hemodilution, and routine cell saver use.A multimodal approach to blood conservation, with high-risk patients receiving all available interventions, may help preserve vital organ perfusion and reduce blood product utilization. In addition, because positive intravenous fluid balance is a significant factor affecting hemodilution during cardiac surgery, especially when CPB is used, strategies aimed at limiting intraoperative fluid balance positiveness may also lead to reduced blood product utilization.This review discusses currently available techniques that can be used intraoperatively in an attempt to avoid or minimize fluid balance positiveness, to preserve the patient's own red blood cells, and to decrease blood product utilization during cardiac surgery.

Clinical Evaluation of the Air Removal Characteristics of an Oxygenator with Integrated Arterial Filter in a Minimized Extracorporeal Circuit

The use of minimized extracorporeal circuits (MECC) in cardiac surgery is an important measure to increase the biocompatibility of cardiopulmonary bypass during coronary artery bypass grafting (CABG). These circuits eliminate volume storage reservoirs and bubble traps to minimize the circuit. However, the reduction in volume may increase the risk of gaseous microemboli (GME). The MECC system as used by our group consists of a venous bubble trap, centrifugal pump, and an oxygenator. To further reduce the risk of introducing GME, an oxygenator with an integrated arterial filter was developed based on the concept of minimal volume and foreign surface. We studied the air removal characteristics of this oxygenator with and without integrated arterial filter. The quantity and volume of GME were measured with precision at both the inlet and outlet of the devices.

Our results showed that integration of an arterial filter into this oxygenator increased GME reducing capacity from 69.2% to 92%. Moreover, we were able to obtain data on the impact of an arterial filter on the exact size-distribution of GME entering the arterial line.

The present study demonstrates that an MECC system and oxygenator with integrated arterial filter significantly reduces the volume and size of GME. The use of an integrated arterial filter in an MECC system may protect the patient from the deleterious effects of CPB and may further improve patient safety.

A comparison of low vs conventional-dose heparin for minimal cardiopulmonary bypass in coronary artery bypass grafting surgery

The biocompatibility of minimal extracorporeal circuits has improved; however, anticoagulation is still required. We compared standard high-dose anticoagulation with a low-dose heparin regimen in a retrospective study of patients who underwent coronary bypass surgery using minimal cardiopulmonary bypass. One hundred patients who received 300 IU.kg(-1) heparin were compared with 68 patients who received heparin according to an individually adjusted activated coagulation time target of 300 s, resulting in a mean (SD) heparin dose of 145 (30) IU.kg(-1) . There were no thromboembolic events in either group; however, patients in the low-dose group had lower 24-hour mean (SD) postoperative blood loss than the conventional group (545 (61) vs 680 (88) ml, p=0.001) and a reduced rate of transfusion of allogeneic blood (15% patients transfused vs 32%, p=0.01). An individually tailored low-dose heparin regimen for minimal cardiopulmonary bypass is safe and may be associated with reduced bleeding and lower transfusion requirements.

Autotransfusion system or integrated automatic suction device in minimized extracorporeal circulation: influence on coagulation and inflammatory response

OBJECTIVE

To measure surrogate markers of coagulation activation as well as of the systemic inflammatory response in patients undergoing primary elective coronary artery bypass grafting (CABG) using either the so-called Smart suction device or a continuous autotransfusion system (C.A.T.S.®).

METHODS

Fifty-eight patients being operated with a miniaturized circuit (minimal extracorporeal circuit, MECC) were prospectively randomized to using a so-called Smart suction device or a routine continuous autotransfusion system (C.A.T.S.®) for collection of mediastinal shed blood. The coagulation response was measured by thrombin-antithrombin complex (TAT) and D-dimer. The inflammatory response was measured by Interleukin 6 (IL-6) and complement factor 3a (C3a) at three different time points, before surgery, 2h after surgery, as well as 18 h after surgery.

RESULTS

No serious adverse cardiovascular event was observed. Serum levels of TAT significantly differed between both groups 2h after surgery (Smart suction 16.12 ± 13.51 μg l⁻¹ vs C.A.T.S® 9.83 ± 7.81 μg l⁻¹, p = 0.040) and returned to baseline values after 18 h in both groups. Serum levels of D-dimer showed a corresponding pattern with a peak 2h after surgery (Smart suction 1115 ± 1231 ng ml⁻¹ vs C.A.T.S.® 507 ± 604 ng ml⁻¹, p = 0.025). IL-6 levels also significantly differed between both groups 2h after surgery (Smart suction 186 ± 306 pg ml⁻¹ vs C.A.T.S.® 82 ± 71 pg ml⁻¹, p = 0.072). No significant changes in serum levels of C3a over time could be observed.

CONCLUSIONS

Despite no differences in the clinical course of patients with either Smart suction or C.A.T.S.® being observed, surrogate markers of coagulation and inflammation seem to be less pronounced in patients where cardiotomy blood is not being directly reinfused. As such, C.A.T.S.® should be preferred in routine CABG, as long as no extensive volume substitution is anticipated.

Myocardial protection in patients undergoing coronary artery bypass grafting surgery using minimized extracorporeal circulation in combination with volatile anesthetic

The minimized extracorporeal circulation (ECC) is a safe alternative for coronary artery bypass grafting (CABG) and allows a reduction of the negative effects associated with conventional extracorporeal circulation. Experimental and clinical data indicate that the anesthetic regime might influence the ischemia-reperfusion injury in CABG surgery. The aim of our retrospective study was to investigate the cardioprotective effects of two different minimized ECC systems in combination with two different anesthetic concepts and to determine the impact on oxygen consumption during aortic cross-clamping (ACC). Data of 1,182 patients who underwent elective isolated CABG with minimized ECC from January 1, 2003, to December 31, 2008, were enrolled in a retrospective manner. Patients were allocated either to sevoflurane-based volatile anesthesia using PRECiSe system (SEVO group) or to propofol-based intravenous anesthesia using MECC system (PROP group). Postoperatively, the SEVO group showed lower concentrations of myocardial fraction of creatine kinase compared with the PROP group (p < 0.001). During the period of ACC, the values of systemic vascular resistance (SVR) were higher in SEVO group (p < 0.005). Also, the SEVO group showed lower oxygen consumption at each time point ACC (p < 0.0001). In conclusion, PRECiSe system using a microporous capillary oxygenator in combination with sevoflurane-based volatile anesthetic regimen seem to provide lower postoperative myocardial cell damage and to allow improved perfusion with higher SVRs and lower oxygen consumption during ACC.

Evaluation of closed cardiopulmonary bypass circuit for aortic valve replacement

Since 2005, we have used a novel technique based on the closed cardiopulmonary bypass system without cardiotomy suction (minimal cardiopulmonary bypass [mini-CPB]) for aortic valve replacement (AVR). In this study, we investigated the clinical advantages of this approach. We prospectively studied 32 patients who underwent isolated AVR using the mini-CPB (group M, n = 13) or conventional CPB (group C, n = 19). We compared the hemodilution ratio, serum interleukin (IL)-6 and IL-8 levels, and blood transfusion volume between the two groups. The characteristics, duration of CPB, and aortic cross-clamping time did not differ between the two groups. The hemodilution ratio was significantly lower in group M just after starting CPB (M vs. C: 14% +/- 2% vs. 25% +/- 3%, p = 0.0009). IL-6 levels increased significantly after surgery in both groups, but the postoperative levels were significantly lower in group M at 6 (84.9 +/- 24.9 pg/ml vs. 152 +/- 78 pg/ml, p = 0.042) and 12 (72.7 +/- 36.1 pg/ml vs. 123 +/- 49.6 pg/ml, p = 0.029) hours after CPB. There were no differences in IL-8 or blood transfusion volume after CPB. Mini-CPB offers an alternative to conventional CPB for AVR and has some advantages regarding hemodilution and serum IL-6 levels. However, it is unlikely to become the standard approach for AVR because there are no marked clinical advantages of mini-CPB.

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.

Miniaturized cardiopulmonary bypass improves short-term outcome in cardiac surgery: a meta-analysis of randomized controlled studies

OBJECTIVE

To investigate whether the use of miniaturized cardiopulmonary bypass translates into decreased morbidity and mortality in patients having cardiac surgery.

METHODS

We independently conducted a systematic review and meta-analysis of data pooled from existing trials listed in PubMed and conference proceedings. Sixteen studies were identified, including 1619 patients having cardiac surgery. Inclusion criteria were random allocation to treatment and comparison of a miniaturized cardiopulmonary bypass system versus conventional cardiac surgery. Exclusion criteria were duplicate publications, nonhuman experimental studies, and no outcome data. The end points were the rate of neurologic and myocardial damage and the number of patients transfused.

RESULTS

Miniaturized cardiopulmonary bypass was associated with significant reductions of neurologic damage (4/548 [0.7%] vs 19/555 [3.4%], odds ratio = 0.30 [0.12-0.73], P = .008), reduction in peak cardiac troponin (weighted mean difference = -0.15 ng/dL [-0.18, -0.11], P < .001), and in the number of transfused patients (55/552 [9.9%] vs 101/563 [17.9%], odds ratio = 0.42 [0.28-0.63], P < .001). No difference in mortality was noted (8/758 [1.0%] vs 14/771 [1.8%], odds ratio = 0.60 [0.26-1.39]).

CONCLUSIONS

Miniaturized cardiopulmonary bypass has beneficial effects resulting in decreased transfusion rate and cardiac and neurologic damage.

Mini ECC vs. conventional ECC: an examination of venous oxygen saturation, haemoglobin, haematocrit, flow, cardiac index and oxygen delivery

In our clinical daily routine, it is noticeable that lower cardiac indices are reached more often without negative consequences when using mini extracorporeal circulation (ECC) systems than when using open ECC systems. We evaluated haemoglobin concentration, haematocrit, blood flow, cardiac index (CI) and mixed-venous oxygen saturation (vSO2) in patients undergoing surgery using mini ECC (n=10 cases) and ECC (n=10 cases). This analysis shows that, with a mini ECC system, the range of oxygen delivery is equal to that achieved when using an open standard ECC system, despite a lower cardiac index. This phenomenon can be explained through a significant lower haemodilution and, therefore, a higher concentration of haemoglobin.

The influence of pre-operative risk on the number of circulating endothelial progenitor cells during cardiopulmonary bypass

BACKGROUND AIMS

The number of circulating endothelial progenitor cells (EPC) depends on cytokine release and is also associated with cardiovascular risk factors. During cardiopulmonary bypass (CPB) the endothelium is the first organ to be affected by mechanical and immunologic stimuli. We hypothesized that the magnitude of EPC mobilization by CPB correlates with the pre-operative cardiovascular morbidity profile.

METHODS

EPC were quantified in blood samples from 30 patients who underwent cardiac surgery by magnetic bead isolation and fluorescence-activated cell sorting (FACS) analysis, based on concomitant expression of CD34, CD133 and CD309. Patients were divided into two groups based on the European System for Cardiac Operative Risk Evaluation (EuroSCORE): low risk (LR) and high risk (HR). Ten healthy volunteers served as controls. Samples were obtained before the start of CPB and at 1 and 24 h post-operatively. Plasma samples were collected for determination of release levels of cytokines and growth factors.

RESULTS

All CPB patients showed a significantly reduced basal number of EPC compared with healthy individuals (LR 5.60 +/- 0.39/mL, HR 3.89 +/- 0.34/ mL, versus control 0.807 +/- 0.82/mL, P = 0.012 versus LR, P< 0.001 versus HR). CPB induced EPC release that peaked 1 h after surgery (pre-operative 4.79 +/- 0.32/mL, 1 h 57.49 +/- 5.31/mL, 24 h 6.67 +/- 1.05/mL, P< 0.001 pre-operative versus 1 h, P< 0.001 pre-operative versus 24 h) and was associated with the duration of CPB. However, EPC release was significantly attenuated in HR patients (33.09 +/- 3.58/mL versus 81.89 +/- 4.36/mL at 1 h after CPB, P < 0.0001) and inversely correlated with the pre-operative EuroSCORE. Serum granulocyte-colony-stimulating factor (G-CSF), stem cell factor (SCF) and vascular endothelial growth factor (VEGF) levels increased throughout the observation period and were also correlated with the EPC count.

CONCLUSIONS

Cardiovascular risk factors influence the mobilization of EPC from the bone marrow after stimulation by CPB. This could be secondary to impaired mobilization or the result of increased EPC turnover, and may have implications for future cell therapy strategies in cardiac surgical patients.

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.

Comparison of two different minimized extracorporeal circulation systems: hematological effects after coronary surgery

Cardiopulmonary bypass induces hemolysis and activation of inflammatory and coagulation systems as a result of a combination of mechanical trauma and biological mechanisms. The aim of our study was to evaluate the performance of two different minimized extracorporeal circulation (ECC) systems and to compare their influence on blood components. From January 2003 to December 2008, 1,218 patients underwent coronary artery bypass grafting with minimized ECC. The PRECiSe system (41%) consists of a microporous capillary membrane oxygenator (MO) and a diagonal pump (DeltaStream DP2). The MECC system (59%) is composed of a polymethylpentene MO with a plasma-tight diffusion membrane and a centrifugal pump (RotaFlow). Serial blood samples were taken preoperatively (T0), on arrival to intensive care unit (T1), 6 hours postoperatively (T2), and at discharge (T3). Demographic data, intraoperative, and technical parameters were similar in both groups. At T1 and T2, the platelet count in the PRECiSe group was significantly lower than that in the MECC group (p < 0.01). Furthermore, at T1, levels of lactate dehydrogenase were significantly higher in the PRECiSe group (p < 0.05). In addition, postoperative blood loss was significantly higher using the PRECiSe system (p < 0.05). In conclusion, cardiac surgery with the MECC system is associated with less postoperative bleeding and improved blood cell preservation.

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.

Perioperative Coagulopathy, Bleeding, and Hemostasis During Cardiac Surgery

Cardiac surgery patients use 10%-25% of the blood products transfused annually in the United States. The transfusion of red blood cells or blood products has been the subject of intense scrutiny over the past 10 years. Bleeding after cardiac surgery can be surgical or nonsurgical and lead to hemodynamic compromise and surgical reexploration. Because hemorrhage and blood product transfusions are associated with multiple negative outcomes, including increased mortality, it is prudent to understand the mechanisms responsible for nonsurgical bleeding. This review focuses on the physiology of the normal coagulation and fibrinolysis, risk factors associated with patients presenting for cardiac surgery, impairments of normal hemostasis associated with cardiac surgery and cardiopulmonary bypass (CPB), and potential interventions to reduce perioperative blood loss and blood transfusion.

The use of a mini bypass circuit for minimally invasive mitral valve surgery

Introduction: The purpose of the study is to clinically evaluate minimally invasive mitral valve surgeries (MIMVS) using a mini bypass circuit. The challenge to perfusion is to keep pace with MIMVS, with demonstrated improvements in perfusion-related technologies.

Methods: From October 28, 2005 to September 10, 2008, we retrospectively evaluated thirty-four elective cases which used the mini-circuit (Medtronic Resting Heart System®), with respect to safety, efficacy, cannulation technique, blood usage, resultant hemoglobin, length of ICU and hospital stay, and complications.

Conclusion: The Medtronic Resting Heart System® alleviates many factors, such as high shear stress, turbulence, air to blood interface and decreased oncotic pressure caused by hemodilution, providing more efficient perfusion to our MIMVS patients. We demonstrate, with minor circuit modifications and attention to venous air issues, that this mini-circuit can be used safely and effectively, while being associated with improvements in patient outcomes.

Aortic valve replacement with minimal extracorporeal circulation versus standard cardiopulmonary bypass

The purpose of this study was to evaluate the safety and the clinical outcomes of aortic valve replacement (AVR) performed with minimally invasive extracorporeal circulation (miniECC) technique vs. standard cardiopulmonary bypass (CPB). From February 2006 to December 2007 a total of 181 isolated AVR were performed, of these 53 patients were operated using minimal extracorporeal circulation system and 128 patients were operated using the standard CPB. Demographic characteristics and operative data were similar in both groups except for EuroSCORE (P<0.0001). Operative mortality (<30 days) was 3.8% for miniECC group and 4.7% for CPB group (P=ns). Patients in both groups showed similar postoperative chest tube drainage (432+/-325 ml vs. 460+/-331 ml, P=ns). The percentage of transfused patients was similar in both groups (37.7% vs. 43.8%, P=0.45). The number of transfused blood bank products was higher in patients with a body surface area >1.7 m(2) and who underwent traditional CPB in respect to miniECC system. Postoperatively renal injury, atrial fibrillation episodes, neurologic event rate, ICU and hospital stay length were similar in both groups. The miniECC is suitable for AVR providing good clinical results but the present results should not identify the miniECC system to be superior to the conventional CPB.

Beneficial effects of modern perfusion concepts in aortic valve and aortic root surgery

Minimized perfusion circuits (MPC) were found to reduce side effects of standard extracorporeal circulation (ECC). We evaluated the safety and efficacy of the ROCsafe™ MPC for aortic valve and aortic root surgery. One hundred and seventy patients were randomized for surgery using either MPC [n = 85, 30 female/55 male, mean age: 69.8 ± 11.8 years; aortic valve replacement (AVR): n = 40; AVR + coronary artery bypass graft (CABG): n = 31; David operation: n = 3; aortic root replacement (ARR): n = 11] or ECC [n = 85, 29 female/56 male, mean age: 67.7 ± 9.5 years; AVR: n = 39; AVR+CABG: n = 35, David operation: n = 2; ARR: n = 9]. Neurological status, length of ICU stay, C-reactive protein (CRP), blood count, transfusion requirements and bleeding volume were analyzed. The MPC system provided ultrasound-controlled de-airing. A small roller pump and a flexible reservoir were used for left ventricular venting. As a control, we used a standard ECC with cardiotomy suction and hard-shell reservoir. Cross-clamp time (MPC: 76.5 ± 29.5; ECC: 79.0 ± 34.0 min) and bypass time (MPC: 103.0 ± 37.9; ECC: 106.9 ± 44.9 min) were comparable between groups. Transfusion requirements (red blood cells: MPC: 1.5 ± 1.5 vs. ECC: 2.2 ± 2.1 units [p = 0.05], frozen plasma: MPC: 1.2 ± 1.8 vs. ECC: 1.9 ± 2.4 units [p = 0.03]), postoperative bleeding (MPC: 521 ± 283 vs. ECC: 615 ± 326 ml/24 h, p = 0.09) were lower using MPC. ICU stay was shorter with MPC (1.6 ± 1.6 days) compared to ECC (2.4 ± 2.8 days, p = 0.001). One stroke occurred in each group. The ROCsafe™ MPC provides safe circulatory support for a wide range of aortic valve surgeries. Transfusion requirements, postoperative bleeding and length of ICU stay were markedly reduced compared to standard extracorporeal perfusion.

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.

Minimal extracorporeal circulation: an alternative for on-pump and off-pump coronary revascularization

BACKGROUND

Coronary artery bypass surgery employing minimal extracorporeal circulation (MECC) was compared with standard extracorporeal circulation (ECC) and off-pump coronary artery bypass graft surgery (OPCABG) with regard to the perioperative course.

METHODS

From January 2004 to December 2007, 1,674 patients (n = 558 MECC, n = 558 ECC, n = 558 OPCABG) who underwent coronary bypass surgery were studied. The primary end point was in-hospital mortality; secondary end points were perioperative variables, intensive care, and in-hospital course.

RESULTS

Demographic data, comorbidity, and the European System for Cardiac Operative Risk Evaluation score (MECC 3.0%, ECC 3.5%, OPCABG 3.2%) were similar among the groups, but in-hospital mortality for elective and urgent/emergent patients was lower in the MECC and OPCABG groups (MECC 3.2%, OPCABG 3.7%, ECC 6.9%; p < 0.05). The number of distal anastomoses was lowest in the OPCABG group, but comparable for MECC and ECC patients. Postoperative ventilation time, release of creatinine kinase, catecholamine therapy, drainage loss, and transfusion requirements were lower in the MECC and OPCABG groups, whereas stay in the intensive care unit was shorter only in the latter (p < 0.05).

CONCLUSIONS

Minimal extracorporeal circulation is an easy and safe procedure for coronary artery bypass graft surgery. In selected patients, the advantages of MECC equal those of OPCABG. MECC should be considered as an alternative to OPCABG and standard ECC procedures.

Extracorporeal circulatory systems in the interhospital transfer of critically ill patients: experience of a single institution

BACKGROUND AND OBJECTIVES

Critically ill patients with acute circulatory failure cannot be moved to other institutions unless stabilized by mechanical support systems. Extracorporeal heart and lung assist systems are increasingly used as a bridge to end-organ recovery or transplantation, and as an ultimate rescue tool in cardiopulmonary resuscitation.

PATIENTS AND METHODS

From July 2001 to April 2008, we had 38 requests for extracorporeal support for interhospital transfer carried out by the air medical service. Respiratory failure was present in 29 patients, who were provided with pumpless extracorporeal lung assist (PECLA) or veno-venous extracorporeal membrane oxygenation (ECMO). Cardiac failure dominated in 9 patients, who underwent implantation of extracorporeal life support (ECLS). Underlying diseases were acute respiratory distress syndrome in 15 patients, pneumonia in 7, prior lung transplant status in 4, cardiogenic shock in 7, and septic shock in 4.

RESULTS

All assist systems were connected via peripheral vessels by the Seldinger technique. Transport was uneventful in all cases with no technical failures. On arrival at the specialized care hospital, two patients had leg ischemia and underwent relocation of the arterial cannula. After a mean (SD) support of 5.1 (3.0) days for PECLA, 3.5 (2.9) days for ECLS, and 7.3 (5.8) days for ECMO, 60%, 66%, and 66% of patients, respectively, could be successfully weaned from the systems. Discharge rates were 45% for PECLA, 44% for ECLS, and 56% for ECMO.

CONCLUSION

Our experience proves that minimized extracorporeal assist devices allow safe assistance of patients with isolated or combined heart and lung failure in need of interhospital transfer. Critically ill patients get a chance to reach a center of maximum medical care.

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.

The minimized extracorporeal circulation system causes less inflammation and organ damage

The minimized extracorporeal circulation system (MECC) is being used to reduce priming volume and blood/polymer contact during cardiac procedures. In this study, we evaluated the efficacy and potential advantages of the system in coronary artery bypass graft (CABG) patients. We included two groups of patients destined for CABG in a prospective, randomized study: Group A was operated on the usual pump (n = 30) while Group B was operated using the MECC (n = 50). Pre-operative demographics, intra-operative times and values as well as a series of post-operative outcome data (blood loss, transfusion requirements, ventilation time, ICU and hospital stay) were recorded. CK, CK-MB, troponin-T, IL-6 and IL-8 were measured. Pre-operative and post-operative lung function were assessed. In the MECC-operated group, patients developed less post-operative troponin-T (0.2 ± 0.3 vs. 0.5 ± 0.5 ng/mL, p=0.031) and less IL-8 (13.8 ± 5 vs. 22.5 ± 0.5 µg/L, p = 0.05). While blood loss was comparable in both groups, packed red blood cells and fresh frozen plasma were given less frequently in the MECC group (p = 0.015 resp. 0.022). The one-tailed Student’s t-test revealed shorter bypass time in the MECC group (74 ± 17 vs. 82 ± 24 min). There was no difference in ventilation and ICU-time (patients were not treated in a fast-track fashion). The FEV1 was better in the MECC group (relative values: 70.1 ± 18.2% vs. 61.1 ± 12.3%, p = 0.02). Utilization of the MECC may cause less cytokine (IL-8) liberation, owing to less blood/tubing contact, as well as less red blood cell and fresh frozen plasma demand. It may also be the circuit in patients with chronic obstructive pulmonary disease (COPD).