Complement and neutrophil activation during cardiopulmonary bypass: a study in the complement-deficient dog

Heparin sensitivity and postoperative blood loss in patients undergoing cardiac surgery with cardiopulmonary bypass

BACKGROUND

Heparin-associated coagulation disorder is an important factor related to postoperative bleeding in patients undergoing cardiac surgery with cardiopulmonary bypass. Currently, the relationship between heparin sensitivity and postoperative bleeding is unknown.

OBJECTIVE

To investigate the relationship between individual heparin sensitivity and postoperative blood loss in patients undergoing cardiac surgery.

DESIGN

Prospective controlled study.

SETTING

Tertiary teaching hospital, Urumqi, Xinjiang, PR China. The study was conducted from January 2016 to August 2018.

PATIENTS

A total of 195 adult patients undergoing cardiac valve replacement surgery were included.

INTERVENTION

After initial heparin dosing (2.5 mg kg), patients were divided into three groups according to the whole blood activated clotting time (ACT): group A, insensitive group (ACT < 480 s); group B, sensitive group (480 s < ACT < 750 s); group C, hypersensitive group (ACT > 750 s).

MAIN OUTCOME MEASURES

First, intra-operative and 24-h postoperative blood loss. Second, antithrombin (AT) and factor X mRNA levels. Third, the plasma levels of AT-III and factor X. Fourth, heparin sensitivity index.

RESULTS

Blood loss was approximately 20 to 25% lower in group B than in groups A and C, which was statistically significant (P < 0.01). The AT-III mRNA levels increased from groups A to C and was positively associated with heparin sensitivity; the factor X mRNA levels changed in the opposite direction; a significant difference was observed between groups A and C (P < 0.05). The factor X plasma level showed the same trend as its mRNA. The AT-III plasma level was significantly lower in group B than in groups A and C (P < 0.05).

CONCLUSION

Postoperative blood loss is related to heparin sensitivity in patients undergoing cardiac surgery, and the moderately sensitive patients have the least postoperative bleeding. Individual variation in heparin sensitivity is related to the mRNA and plasma levels of AT-III and factor X.

TRIAL REGISTRATION

Registration number ChiCTR-RPC-17012259.

Effects of Unprocessed and Processed Cardiopulmonary Bypass Blood Retransfused into Patients after Cardiac Surgery

Background

The aim of this prospective study was to compare the effect of autologous unprocessed to processed residual cardiopulmonary bypass blood (CPB) on patients’ laboratory and clinical parameters and outcome.

Methods

20 patients undergoing elective coronary artery bypass surgery were randomized to receive either unprocessed CPB blood (control group) or processed CPB blood employing the Continuous AutoTransfusion System (CATS; Fresenius, Bad Homburg, Germany). We have shown that this method eliminated >93% of activated mediators. Serial laboratory parameters including complement activation, coagulation factors and the stimulation of IL-6 and IL-8 were compared with clinical side effects and patients’ outcome.

Results

Compared to control patients, retransfusion of unprocessed CBP blood significantly increased heparin, free plasma hemoglobin and D-Dimers. Postoperatively, three patients in the control group and two patients in the CATS group required prolonged mechanical ventilation or developed infections associated respectively with elevated C3a (desArg) or IL-6 concentration.

Conclusions

CATS-processing of CPB blood provided a high-quality red blood cell concentrate, resulting in a reduced load of retransfused activated mediators.

Qualitative Assessment of Blood Washing with the Continuous Autologous Transfusion System (CATS)

A number of different blood-processing methods can be used at the end of cardiopulmonary bypass (CPB) to improve the quality of autologous blood. They include centrifugation, hemofiltration and cell-washing. They differ in processing time required, cost of disposables and the quality of the processed autologous blood product. The newly developed continuous auto-transfusion system (CATS: Fresenius AG, Bad Homburg) uses a continuous cell-washing method. In a prospective study, the oxygenator blood of 10 patients was processed at the end of cardiac surgery with CATS and the quality of autologous blood before and after processing was compared. The processing volumes and the time required were recorded. The concentrations and elimination rates of blood parameters and waste products such as activated coagulation and complement products were measured. At the end of CPB a mean volume of 1,010 ± 174 ml diluted oxygenator blood was processed and concentrated to 310 ± 88 ml in 11.0 ± 2.2 mins. Cellular elements such as erythrocytes and leucocytes were mostly retained and their concentration showed a significant increase after processing (250% and 210% respectively; p < 0.01). Thus, the blood processing with CATS resulted in an excellent hemoconcentration (hematocrit 62 ± 3 vs. 24 ± 4% before processing) with a consistent reproducibility. On the other hand, the CATS concentrate showed a significant loss of autologous plasma proteins. Likewise, all water soluble elements such as waste products are significantly lower in concentration after processing and, if calculated by quantity, they show a high elimination rate (> 93%).

In conclusion, the continuous autologous transfusion system permits an automated, rapid and continuous processing of autologous blood yielding a standardised high quality erythrocyte concentrate.

Vasoplegia after heart transplantation: outcomes at 1 year

OBJECTIVES

Vasoplegia syndrome is a potentially life-threatening condition that can occur following cardiopulmonary bypass. Heart transplantation is a recognized risk factor for developing this vasodilatory state. The objective of this study was to determine the effects of vasoplegia syndrome on 1-year heart transplant outcomes.

METHODS

A retrospective review of orthotopic heart transplants at a single institution between November 2010 and December 2014 was performed. Of the 347 consecutive adult patients, 107 patients (30.8%) met criteria for vasoplegia syndrome. Preoperative factors and intraoperative variables were collected and compared between vasoplegia and non-vasoplegia cohorts. The incidence of postoperative complications, transplant rejection and patient survival within 1 year were evaluated.

RESULTS

Demographics and preoperative medication profiles were similar in both groups, while mechanical circulatory support device use was associated with vasoplegia syndrome (30.8% vs 20.0%; P = 0.039). Perioperative characteristics such as longer cardiopulmonary bypass [165.0 (interquartile range [IQR] 74) min vs 140.0 (IQR 42.7) min; P < 0.001] and increased blood product usage (24.7 ± 17.2 units vs 17.7 ± 14.3 units; P < 0.001) were associated with vasoplegia. Non-vasoplegia patients were more likely to be extubated [42.9 (IQR 37.3) h vs 66.8 (IQR 50.2) h; P < 0.001] and discharged earlier [10.0 (IQR 6) days vs 14.0 (IQR 11.5) days; P < 0.001]. One-year patient survival (92.0% vs 88.6%; P = 0.338) and any-treated rejection rates (82.7% vs 84.3%; P = 0.569) were not significantly different between groups.

CONCLUSIONS

Although vasoplegia syndrome was associated with an increase in perioperative morbidity, including greater mechanical ventilation time and hospital length of stay, no significant differences in survival or allograft rejection at 1 year was demonstrated.

Modified Ultrafiltration in Children

Pediatric cardiopulmonary bypass (CPB) results in increased total body water and capillary permeability. Ultrafiltration has been effective in removing this excess water. The con ventional method of ultrafiltration is restricted by the vol ume in the venous reservoir and therefore is inefficient in smaller children and neonates, whose blood volume is dis proportionately smaller than the circuit volume. Modified ultrafiltration, performed in the immediate post-CPB period, is more effective in these patients. Blood from the aorta is pumped through the ultrafilter, and warm concentrated blood is returned to the right atrium. This removes excess water from the patient and provides a method of salvaging volume from the circuit. Modified ultrafiltration results in consistent improvements in systolic blood pressure, cardiac index, and lung compliance, as well as a reduction in pul monary vascular resistance. Removal of various inflamma tory mediators, such as tumor necrosis factor a, interleu kin-6, and interieukin-8, has been reported after modified ultrafiltration. Other advantages include an increase in he matocrit, colloid osmotic pressure, and coagulation factors, resulting in decreased bleeding and a decreased need for transfusions. In the animal model, improvement in cerebral recovery after deep hypothermic circulatory arrest has been reported. The disadvantages of this technique include the risk of air entrapment, delay in heparin reversal, and poten tial for cooling.

Challenges of cardiopulmonary bypass-a review of the veterinary literature

Cardiopulmonary bypass (CPB) has been used in veterinary medicine in experimental surgery and to address congenital and acquired diseases. We review the veterinary literature and expose common challenges of CPB in dogs and cats. Specifically, we describe the most specific elements of this technique in veterinary patients. The variety in animal size has made it difficult to standardize cannulation techniques, oxygenators, and priming volumes and solutions. The fact that one of the most common cardiovascular disorders, mitral valve disease, occurs predominantly in small dogs has limited the use of bypass in these patients because of the need for small, low prime oxygenators and pumps that have been unavailable until recently. Coagulation, hemostasis, and blood product availability have also represented important factors in the way CPB has developed over the years. The cost and the challenges in operating the bypass machine have represented substantial limitations in its broader use.

Simultaneously performed off-pump coronary artery bypass grafting and colectomy: a case report

This is written so as to report the case of a 71-year-old male with a diagnosis of sigmoid adenocarcinoma accompanied by severe coronary artery disease and unstable angina, which was subject to simultaneous surgical treatment. The patient initially underwent an off-pump coronary artery revascularization in order to avoid the complications of cardiopulmonary bypass, providing the opportunity of a colectomy at the same time with the use of safe surgical means. Our case suggests that performing an off-pump bypass procedure prior to cancer surgery can be an appropriate course of action in carefully selected cases.

Simultaneous off-pump coronary artery bypass graft and nephrectomy

We report the one-stage surgical management of a 68-year-old patient with renal cell carcinoma and serious hematuria combined with coronary artery disease and unstable angina. After the accomplishment of coronary revascularization without cardiopulmonary bypass, we proceeded to nephrectomy and resection of the renal tumor at the same time. The patient's postoperative course was uneventful, and at 17 months of follow-up, the patient showed no signs of recurrence. To the best of our knowledge, such a case has never been reported before in the literature.

Understanding the inflammatory response to cardiac surgery

The systemic inflammatory response to cardiac surgery is common, and resultant impairment of multiple organ function is generally mild or subclinical due to physiological reserve within organ systems. Unfortunately, the changing profile of patients referred for surgery suggests that the systemic inflammatory response may prominently influence surgical outcome in the future. Older, co-morbid patients with more limited physiological reserve are being referred for complex lengthy procedures, and paediatric surgery has witnessed a shift to earlier complex primary correction or palliation involving long cardiopulmonary bypass times or a period of suboptimal organ perfusion using circulatory arrest or low flow cardiopulmonary bypass. Unique to cardiac surgery is the predictability of the inflammatory response, but prophylactic therapies have not translated into clinical benefit, which the preconditioning phenomenon may address.

Inflammation, proinflammatory mediators and myocardial ischemia-reperfusion Injury

Ischemic myocardium must be reperfused to terminate the ischemic event; otherwise the entire myocardium involved in the area at risk will not survive. However, there is a cost to reperfusion that may offset the intended clinical benefits of minimizing infarct size, postischemic endothelial and microvascular damage, blood flow defects, and contractile dysfunction. There are many contributors to this reperfusion injury. Targeting only one factor in the complex web of reperfusion injury is not effective because the untargeted mechanisms induce injury. An integrated strategy of reducing reperfusion injury in the catheterization laboratory involves controlling both the conditions and the composition of the reperfusate. Mechanical interventions such as gradually restoring blood flow or applying postconditioning may be used independently in or conjunction with various cardioprotective pharmaceuticals in an integrated strategy of reperfusion therapeutics to reduce postischemic injury.

Leukocyte Filter Enhances Neutrophil Activation during Combined Aortic Valve and Coronary Artery Bypass Surgery

OBJECTIVE

Cardiopulmonary bypass-induced systemic inflammatory reaction involving the expression of neutrophil surface adhesion molecules is the main mechanism leading to myocardial ischemia-reperfusion injury as well as multiorgan dysfunction. Patients undergoing prolonged cardiopulmonary bypass are especially at risk in this regard. The aim of this prospective, randomized study was to evaluate the impact of continuous leukocyte filtration on the perioperative expression of neutrophil adhesion molecules along with the markers of systemic inflammation during combined coronary artery revascularization and aortic valve surgery due to aortic stenosis.

PATIENT AND METHODS

Twenty patients scheduled for combined coronary artery revascularization and aortic valve surgery due to aortic stenosis were randomized to undergo cardiopulmonary bypass with or without a leukocyte filter (LeukoGuard LG6). The expression of neutrophil adhesion molecules and proinflammatory cytokine response were measured.

RESULTS

The use of the leukocyte filter significantly increased neutrophil CD11b expression (Pg = .003) compared to the control group, which was followed by a faster rise in interleukin-6 levels 5 minutes (median, 125 versus 34 pg/mL) and 2 hours after cardiopulmonary bypass (median, 158 versus 92 pg/mL, Pt x g < .001), respectively. No marked differences in terms of levels of CD11a, CD62L, cardiac troponin-I, or oxyhemodynamics were observed.

CONCLUSIONS

The observed increased neutrophil activation and enhanced inflammatory response do not support the use of continuous leukofiltration in patients undergoing prolonged cardiopulmonary bypass.

The merits of in vitro versus in vivo modeling in investigation of the immune system

Immunity is vital for determining self and for the recognition and swift eradication of foreign antigens without harming the host. Innate immunity developed in metazoan, multi-cellular organisms under overwhelming selection pressure of invasive microbes and, although imperfect, has performed admirably to enable the evolution of higher eukaryotes. Adaptive immunity developed within an existing innate immune system to more effectively eradicate foreign antigens, whether from pathogens, malignant cells, or microbial toxins, such that repeated stimulations with foreign antigens are more efficiently excluded. Investigation of the immune system requires both in vivo and in vitro experimentation, not only because of the inherent complexity of immunity and the required pertinence of using higher mammals to not falsely disrupt the immune system, but also to use isolates of the specific cellular and humoral components to determine function, signal transduction, and a possible role of these constituents without the complexity and redundancy of immunity in intact animals. The hypotheses of well-designed in vitro experiments must also be tested in intact in vivo models to determine relevance and to discard artifactual findings secondary to the in vitro environment. The following review outlines the basic constituents and functions of both adaptive and innate immunity to demonstrate the importance of both in vivo and in vitro investigation of immunity in our attempt to define host defense and to decrease morbidity and mortality in humans.

Biomaterial-associated thrombosis: roles of coagulation factors, complement, platelets and leukocytes

Our failure to produce truly non-thrombogenic materials may reflect a failure to fully understand the mechanisms of biomaterial-associated thrombosis. The community has focused on minimizing coagulation or minimizing platelet adhesion and activation. We have infrequently considered the interactions between the two although we are generally familiar with these interactions. However, we have rarely considered in the context of biomaterial-associated thrombosis the other major players in blood: complement and leukocytes. Biomaterials are known agonists of complement and leukocyte activation, but this is frequently studied only in the context of inflammation. For us, thrombosis is a special case of inflammation. Here we summarize current perspectives on all four of these components in thrombosis and with biomaterials and cardiovascular devices. We also briefly highlight a few features of biomaterial-associated thrombosis that are not often considered in the biomaterials literature: The importance of tissue factor and the extrinsic coagulation system. Complement activation as a prelude to platelet activation and its role in thrombosis. The role of leukocytes in thrombin formation. The differing time scales of these contributions.

Neutrophil depletion reduces myocardial reperfusion morbidity

BACKGROUND

We tested the hypothesis that depletion of neutrophil leukocytes from the cardioplegic and the initial myocardial reperfusion perfusates reduces clinical indices of reperfusion injury in patients undergoing elective coronary artery bypass.

METHODS

We studied 160 consecutive patients who underwent standard coronary revascularization with cardiopulmonary bypass. Patients with recent myocardial infarction or coronary angioplasty were excluded. Cold blood cardioplegia was used. Just before aortic unclamping, the hearts were perfused retrograde with 250 mL of normothermic cardioplegic solution and 750 mL of blood (pump perfusate). Patients were randomly assigned to two groups. In 80 patients (treated), neutrophils and platelets were removed from all cardiac perfusate during aortic crossclamping with leukocyte filtration. In the remaining 80 patients (control group), leukocyte filtration was not used.

RESULTS

There was no significant difference between groups in age, sex, severity of disease, and number of bypass grafts implanted. Treated patients showed lower prevalence of low cardiac index and reperfusion ventricular fibrillation and lower levels of creatinine kinase MB isoenzyme and troponin I early postoperatively (p < 0.05).

CONCLUSIONS

Neutrophil-filtered blood cardioplegia/reperfusion significantly reduced clinical and biochemical indices of myocardial reperfusion injury after elective coronary revascularization with cardiopulmonary bypass.

A rise of MMP-2 and MMP-9 in bronchoalveolar lavage fluid is associated with acute lung injury after cardiopulmonary bypass in a swine model

Postoperative acute lung injury (ALI) contributes to the morbidity and mortality following cardiopulmonary bypass (CPB). To determine whether the presence of matrix metalloproteinases (MMPs) is associated with ALI after CPB, MMP-2 and MMP-9 activities in bronchoalveolar lavage fluid (BALF) were compared with parameters indicating impaired gas exchange. In a prospective study, 17 minipigs were subjected to CPB for 60 min. Before and at five and 180 min after CPB, MMP-2 and MMP-9 were assayed in BALF and the arterial-alveolar gradient of oxygen tension (AaDO2), the pulmonary capillary wedge pressure (PCWP) and the water content of lung tissue samples (Wt) were evaluated and compared with baseline values. MMP-2 and MMP-9 increased significantly 5 minutes (2.1- and 6.2-fold, respectively) and 180 minutes (3.4- and 14.3-fold, respectively) post-CPB. AaDO2 and Wt, but not PCWP, increased significantly 180 minutes after CPB and only AaDO2, but not PCWP or Wt, was significantly correlated with MMP-2 (r = 0.66, p = 0.006) and MMP-9 (r = 0.62, p = 0.01). In conclusion, high levels of MMP-2 and MMP-9 in the pulmonary compartment are associated with ALI after CPB.

Pulmonary dysfunction after cardiac surgery

Postoperative lung injury is one of the most frequent complications of cardiac surgery that impacts significantly on health-care expenditures and largely has been believed to result from the use of cardiopulmonary bypass (CPB). However, recent comparative studies between conventional and off-pump coronary artery bypass grafting have indicated that CPB itself may not be the major contributor to the development of postoperative pulmonary dysfunction. In our study, we review the associated physiologic, biochemical, and histologic changes, with particular reference to the current understanding of underlying mechanisms. Intraoperative modifications aiming at limiting lung injury are discussed. The potential benefits of maintaining ventilation and pulmonary artery perfusion during CPB warrant further investigation.

What really is blood compatibility?

The criteria for nonthrombogenicity are classically defined as long clotting times and minimal platelet deposition. The inability to point to unequivocal progress in the development of truly nonthrombogenic materials, highlights the inadequacy if not actually invalidity of these criteria. Our approach is to define nonthrombogenicity in terms of: (1) a thrombin production rate constant, kp < 10(-4) cm s(-1); (2) low platelet consumption and low degree of platelet activation (e.g., microparticle formation); (3) perhaps some platelet spreading; and (4) low complement and leukocyte activation. Only when the target becomes clear, will it be possible to identify clear strategies for producing the materials we need.

Flow cytometric evaluation of material-induced platelet and complement activation

Flow cytometry is used to characterize the activation state of platelets and leukocytes within whole blood after contact for 4 h at 37 degrees C with various materials under conditions of low shear. The contact involved adding heparinized whole blood to small diameter tubes that were connected to two arms extending from a rocking platform. For all surfaces (polyethylene, polypropylene, Silastic, PVA hydrogel) tested there was strong evidence of platelet activation in the bulk blood: platelet-derived microparticles. P-selectin expression and platelet-leukocyte aggregates. Only contact with PVA hydrogel surfaces led to dramatic increases in CD11b up-regulation on monocytes and neutrophils that was inhibited by complement inhibition (sCRI). Flow cytometry was also used to evaluate the effectiveness of various agents to inhibit material-induced complement activation. The assay involved incubating 10 microm polystyrene beads for 1 h with serum at 37 degrees C before isolating the beads so as to label them with a monoclonal antibody against a neoantigen on SC5b-9. The beads were then identified by flow cytometry and the fluorescence associated with their SC5b-9 level recorded. The ability of C1-INH, pentamidine and benzamidine to moderately inhibit SC5b-9 levels suggests a role for classical complement activation in material-induced complement activation.

Animal models of inherited complement deficiency

The initial description of murine strains deficient in complement component C5 has been followed by the recognition in a range of animal species of a variety of natural complement component deficiencies, many of which have been characterized at the molecular level. The use of such species in inflammatory and infectious experimental models has led to significant progress in understanding the role of specific complement factors (and pathways) in disease pathogenesis. Deficiencies of early complement factors are characterized by impairment of immune response, possibly due to defective processing of immune complexes. Complete (but not partial) deficiency of the central component C3 predisposes affected animals to significant risk of infection and renal disease. Studies in species deficient in the terminal pathway component C6 are particularly relevant for investigating the pathogenetic role of the terminal membrane attack complex (MAC), implicating it as a causative agent in diverse inflammatory insults such as reperfusion injury, glomerular damage, and xenograft hyperacute rejection. Further investigations in such naturally deficient strains, added to results derived from studies in knockout animals, are likely to expand our understanding of the role of the activated complement system in experimental inflammatory disease, with significant potential implications for the treatment of human disease.

Individualized heparin and protamine management in infants and children undergoing cardiac operations

BACKGROUND

Measurements of activated coagulation time do not correlate with plasma concentration of heparin. This study investigated the effects of a patient-specific method to manage anticoagulation and its reversal in pediatric patients undergoing cardiopulmonary bypass.

METHODS

Infants and children were randomly assigned to receive either a standard dose of heparin (300 IU/kg; group C, n = 13) or an individualized dose, calculated by an in vitro heparin dose-response test (group HC, n = 13). Protamine dose was based on a 1 mg/l mg ratio of total administered heparin for patients in group C and of the residual heparin concentration in group HC.

RESULTS

Administered heparin was significantly higher and total protamine dose was significantly reduced in the HC group (both p < or = 0.001). There was less thrombin generation (p = 0.02) and fibrinolysis (p = 0.05) in group HC. Blood loss and requirement for transfusion of blood and fresh frozen plasma were also lower in group HC (all p < or =0.05).

CONCLUSIONS

An individualized management of anticoagulation and its reversal results in less activation of the coagulation cascade, less fibrinolysis, and reduced blood loss and need for transfusions. Further studies are warranted to better define the clinical impact of these findings.

The side-effects of cardiopulmonary bypass on the lungs: changes in bronchoalveolar lavage fluids

Although technical refinements have improved the safety of cardiac operations, postoperative dysfunction of lung and other organs occurs frequently after cardiopulmonary bypass (CPB). The aim of the present study was to search the aetiopathogenesis of pulmonary complications due to CBP. Ten patients with stable coronary artery disease, undergoing coronary artery bypass grafting (CABG) surgery, were included in the study. Forty bronchoalveolar lavage (BAL) fluid samplings were performed in the 10 patients. Samples were obtained at the following time periods: (1) preoperatively; (2) at the end of the first hour after anaesthetic induction; (3) at the conclusion of 30 min of crossclamp on CPB; and (4) at the conclusion of 20 h after the end of CPB, postoperatively. Cell contents of bronchoalveolar lavage fluid, alveolar macrophage viability, eosinophil cationic protein (ECP) levels and myeloperoxidase (MPO) concentrations were analysed in each bronchoalveolar lavage fluids. While the percentage of preoperative macrophages was 85.90% and the percentage of preoperative neutrophils was 2.40%, they were 77.00% and 11.30% in the postoperative samples, respectively. Mean alveolar macrophage viability was 96.20% preoperatively and 90.40% in the postoperative period. Preoperative eosinophil cationic protein mean concentration was < 2 microg/l and mean response value (RV) was 28.80. Preoperative mean myeloperoxidase concentration was 7.66 ng/ml. Postoperative eosinophil cationic protein mean response value was 63.40 and mean myeloperoxidase concentration was 59.25 ng/ml. There were significant differences between third and final samples with regard to both neutrophil percentages (p = 0.028) and MPO levels (p = 0.005). While the preoperative mean PaO2 value was 89.39 mmHg and mean SaO2 value was 97.12%, they were calculated in the postoperative arterial blood specimens of patients, without inhaling O2, as 65.31 mmHg and 93.84%. These changes between blood gas analyses reflect the impairment of the lungs (p = 0.009 and p = 0.007, respectively). Neither alveolar macrophage viability nor ECP levels changed significantly between consecutive periods. However, when the results of the first and fourth samples were compared, we saw the cumulative effects of CPB, in that alveolar macrophages lost their viability and ECP mean RVs rose. These changes were statistically significant (p = 0.027 and p = 0.013, respectively). However, postoperative ECP levels were not like those found in a patient with asthma. Also, changes between alveolar macrophage percentages (p = 0.028), between neutrophil percentages (p = 0.036) and between MPO concentrations (p = 0.005) were statistically significant. Again, changes in neutrophil percentages between first and final samples correlated with changes in MPO levels between same periods (r = 0.657, p = 0.039).

Recombinant human complement C5a receptor antagonist reduces infarct size after surgical revascularization

OBJECTIVES

This study tested the hypothesis that a recombinant human C5a antagonist, CGS 32359, attenuates neutrophil activation and reduces infarct size in a porcine model of surgical revascularization.

METHODS

CGS 32359 (0.16-16 micromol/L) dose-dependently inhibited superoxide production by human C5a-activated porcine neutrophils (18 +/- 3.7 vs 1.6 +/- 0.5 nmol/5 min/5 x 10(6) neutrophils; P <.05) and reduced neutrophil adherence to coronary endothelium from 194 +/- 9 to 43 +/- 6 neutrophils/mm(2) (P <.05). The left anterior descending coronary artery was occluded for 50 minutes, after which saline solution (n = 8), mannitol-buffer vehicle (n = 9, 102 mg/kg bolus, 102 mg. kg(-1). h(-1)), or CGS 32359 (CGS, n = 7, 60 mg/kg bolus, 60 mg. kg(-1). h(-1)) was infused. After ischemia, 1-hour arrest was achieved by means of multidose hypothermic (4 degrees C) blood cardioplegia, followed by 2.5 hours of off-bypass reperfusion. The ligature on the left anterior descending artery was released before the second infusion of cardioplegic solution.

RESULTS

Area at risk was similar in all groups (saline solution, 27% +/- 2%; mannitol-buffer vehicle, 26% +/- 2%; CGS, 26% +/- 2% left ventricular mass). Infarct size (area necrosis/area at risk) was significantly reduced by CGS (18% +/- 6%, P <.05) versus saline solution (52% +/- 3%) and mannitol-buffer vehicle (60% +/- 4%). Postischemic systolic shortening (sonomicrometry) in the area at risk was significantly improved with CGS (0.8% +/- 0.9%) compared with saline solution (-3.7% +/- 1.1%) and mannitol-buffer vehicle (-6.4% +/- 1.0%). Myeloperoxidase activity from accumulated neutrophils was less in the ischemic zone of CGS (0.014 +/- 0.002 U/100 mg tissue; P <.05) than mannitol-buffer vehicle (0.133 +/- 0.012 U/100 mg tissue).

CONCLUSIONS

We conclude that the recombinant human C5a receptor antagonist CGS 32359 inhibits surgical ischemia-reperfusion injury after coronary occlusion.

Clinical role of blood heparin level monitoring during open heart surgery

Protamine has been used for neutralizing heparin and its dosage is decided by the initial fixed dose of heparin. Adequate protamine neutralization is very important to reduce complications. To attenuate excess reactions, in particular, whole blood heparin concentration during and after cardiopulmonary bypass was measured using Hepcon, and the efficacy of optimal protamine dose in open heart surgery was evaluated. Twenty patients were randomly divided into two comparable groups, P and C. In the C group, heparin was neutralized with an initial fixed dose of protamine, 1.67 mg protamine per milligram total heparin (n = 8). In the P group, protamine dose was determined for residual heparin concentration (n = 12). In the P group, blood heparin concentrations at 60 minutes after the establishment of cardiopulmonary bypass, just after cardiopulmonary bypass and first protamine administration were 2.35 +/- 0.14, 2.31 +/- 0.17 and 0.13 +/- 0.08 U/ml, respectively. Concentrations reached zero with the second protamine administration. The requirement of transfusion (659 +/- 224 vs. 1559 +/- 323 ml, p = 0.0314), pulmonary vascular resistance index just after the protamine administration (190 +/- 22 vs. 286 +/- 18 dyne.s.cm-5.m2, p = 0.0137) and the IL-8 levels (just after protamine: 26.9 +/- 5.1 vs. 43.5 +/- 5.9 pg/ml, p = 0.0499, 12 hours after cardiopulmonary bypass: 37.1 +/- 12.1 vs. 86.8 +/- 20.0, p = 0.0435) in the P group were significantly lower than those in the C group. These data suggested that heparin level monitoring in whole blood may be useful to determine the optimal dose of protamine resulting in the decrease of a requirement of blood components in open heart surgery and attenuating in transient pulmonary hypertension and excess protamine-induced inflammatory reactions.

Lung injury and acute respiratory distress syndrome after cardiopulmonary bypass

Cardiopulmonary bypass is often followed by pulmonary dysfunction as assessed by measuring the alveolar-arterial oxygenation gradient, intrapulmonary shunt, degree of pulmonary edema, pulmonary compliance, and pulmonary vascular resistance. It is also regarded as a risk factor for development of acute respiratory distress syndrome. On the other hand, cardiopulmonary bypass is associated with a whole body inflammatory response, which involves activation of complement, leukocytes, and endothelial cells with secretion of cytokines, proteases, arachidonic acid metabolites, and oxygen free radicals. Leukocyte adhesion to microvascular endothelium, leukocyte extravasation, and tissue damage are the final steps. Although the inflammatory response to cardiopulmonary bypass often remains at subclinical levels, it can also lead to major organ dysfunction and multiple organ failure. This review article summarizes the recent literature on the molecular and cellular mechanisms involved in the phenomenon of pulmonary dysfunction after cardiopulmonary bypass. It also summarizes reports on the prevalence and mortality of acute respiratory distress syndrome after cardiac surgery.

Mechanisms of the systemic inflammatory response

The purpose of inflammation is to combat various agents that may injure the tissues. Conditions such as CPB can often cause systemic inflammation and dysfunction of major organs. Pulmonary, renal, myocardial and intestinal function may suffer various degrees of impairment during and after cardiac surgery. Although changes in major organs usually remain clinically insignificant, severe organ failure is not uncommon. The process of systemic inflammation proceeds through activation of serum proteins, activation of leucocytes and endothelial cells, secretion of cytokines, leucocyte-endothelial cell interaction, leucocyte extravasation and tissue damage. Several anti-inflammatory strategies have already been used, some of which have given promising results pertaining to further reduction in the rate of the inflammation-related complications in cardiac surgical patients.

Anti-C5a monoclonal antibody reduces cardiopulmonary bypass and cardioplegia-induced coronary endothelial dysfunction

OBJECTIVE

Because C5a induces tissue injury by activating polymorphonuclear leukocytes, the hypothesis was that inhibition of C5a activity would reduce cardioplegia-related injury.

METHODS

Pigs were placed on cardiopulmonary bypass. The hearts were arrested for 1 hour with hyperkalemic cardioplegia. Pigs were then separated from bypass, and the hearts were reperfused for 2 hours. Anti-porcine C5a monoclonal antibody (1.6 mg/kg, intravenously; n = 6) was administered 20 minutes before the onset of cardiopulmonary bypass. Six pigs received saline solution vehicle. Reactivity of coronary arterioles was studied in vitro with videomicroscopy. Microvessels from uninstrumented pigs served as controls for vascular studies.

RESULTS

Endothelium-dependent relaxation to adenosine diphosphate (percent relaxation of precontraction) was reduced after cardioplegic reperfusion (63% +/- 14% vs 77% +/- 10% in control at 10 micromol/L; P =.01). This impairment in endothelium-dependent relaxation was improved with anti-porcine C5a monoclonal antibody (80% +/- 22%; P =.01 vs saline solution), as was the impaired endothelium-dependent relaxation to clonidine (64% +/- 12% control; 26% +/- 17% saline solution; 55% +/- 24% anti-porcine C5a monoclonal antibody at 10 micromol/L; P =.01 saline solution vs control or anti-porcine C5a monoclonal antibody). Myeloperoxidase activity was significantly decreased (0.2 +/- 0.2 units/g protein; P =.04) in the anti-porcine C5a monoclonal antibody group compared with 5.2 +/- 2.7 in the saline solution group. CH50 2 hours after bypass was not statistically different (0.57 +/- 0.41 unit and 0.65 +/- 0.41 unit, respectively) between the anti-porcine C5a monoclonal antibody and saline solution groups. Despite less myocardial polymorphonuclear leukocyte infiltration after C5a inhibition, maximum rate of rise of left ventricular pressure, percent segmental shortening, and blood flow through the left anterior descending coronary artery were similar in the anti-porcine C5a monoclonal antibody and saline solution groups.

CONCLUSIONS

Inhibition of C5a limits neutrophil-mediated impairment of endothelium-dependent relaxation after cardiopulmonary bypass and cardioplegic reperfusion, but it has no effect on short-term myocardial functional preservation.

Effects of cardiopulmonary bypass on leukocyte and endothelial adhesion molecules

During the inflammatory response, triggered by cardiopulmonary bypass, interaction between activated leukocytes, platelets, and endothelial cells is mediated through the expression of three main groups of adhesion molecules: the selectins, the integrins, and the immunoglobulin superfamily. The selectins, which mediate the initial rolling of the leukocyte on the endothelium, are divided in three subgroups: L-selectin is expressed on all three leukocyte types, P-selectin is expressed on platelets and endothelial cells, and E-selectin is only expressed on endothelial cells. Integrins can be found on most cell types, consist of an alpha and a beta subunit and mediate firm adhesion of the leukocyte and migration into the tissues. They are classified into subgroups according to the type of their beta subunit. Immunoglobulins such as ICAM-1 and VCAM-1 are expressed mainly on endothelium and act as ligands for certain integrins. This review article summarizes the existing, and rapidly expanding, literature concerning the effects of cardiopulmonary bypass on the expression of leukocyte and endothelial adhesion molecules. Deeper understanding of the, behavior and the role of adhesion molecules during cardiopulmonary bypass may facilitate effective intervention in the inflammatory response process and suppression of its adverse effects.

Expression of soluble endothelial adhesion molecules in clinical cardiopulmonary bypass

Soluble endothelial adhesion molecule expression in clinical cardiopulmonary bypass (CPB) was investigated. Neutrophil-mediated endothelial injury plays an important role in CPB-induced organ dysfunction. The adhesion of neutrophil to the endothelium is central to this process. It has been well documented that CPB induces neutrophil activation and changes in neutrophil adhesion molecule expression, but the effect of CPB on endothelial cell activation is not known. This study was designed to measure soluble endothelial adhesion molecules during CPB. We made serial measurements (by specific enzyme-linked immunoabsorbent assay) of plasma levels of the soluble endothelial adhesion molecules, ICAM-1 and E-selectin in patients undergoing routine CPB (n = 7) and in a control group (thoracotomy, n = 3). The results show an initial significant decrease during CPB followed by an increase in plasma E-selectin from 29.3 +/- 5.1 ng/ml (mean +/- SEM) prebypass to 34.0 +/- 5.4 ng/ml at 48 h postbypass. Likewise, plasma ICAM-1 significantly decreased during CPB and then increased from 246.3 +/- 38.0 ng/ml before bypass to 324.8 +/- 25.0 ng/ml and 355.0 +/- 23.0 ng/ml at 24 and 48 h after bypass, respectively. The rise in levels is statistically significant (p < 0.05). This study shows a decrease in circulating ICAM-1 and soluble E-selectin during CPB and an increase in their levels at 48 h after CPB.

Effect of soluble complement receptor type 1 on reperfusion edema and neutrophil migration after lung allotransplantation in swine

OBJECTIVE

Soluble complement receptor type 1 inhibits complement activation by blocking C3 and C5 convertases of the classical and alternative pathways. We evaluated the effect of soluble complement receptor type 1 on lung allograft reperfusion injury.

METHODS

Left lung transplantation was performed in 13 weight-matched pigs (25 to 31 kg) after prolonged preservation (20 hours at 1 degree C). One hour after reperfusion the recipient contralateral right lung was excluded to assess graft function only. Complement activity and C3a levels were measured after reperfusion and at the end of the assessment. Extravascular lung water index, intrathoracic blood volume, and cardiac output were assessed during a 5-hour observation period. Gas exchange and hemodynamics were monitored. At the end of the 5-hour assessment period, myeloperoxidase assay and bronchoalveolar lavage were performed to assess neutrophil migration, and C5b-9 (membrane attack complex) deposits in the allograft were detected by immunohistochemistry. Two groups were studied. In group II (n = 6) recipient animals were treated with soluble complement receptor type 1 (15 mg/kg) 15 minutes before reperfusion. Group I (n = 7) served as the control group.

RESULTS

Serum complement activity was completely inhibited in group II. In contrast to group I, C5b-9 complexes were not detected in group II allograft tissue samples. C3a was reduced to normal levels in group II (p = 0.00005). Extravascular lung water index was higher in group I animals throughout the assessment period (p = 0.035). No significant difference in allograft myeloperoxidase activity (p = 0.10) and polymorphonuclear leukocyte count of the bronchoalveolar lavage fluid (p = 0.057) was detected.

CONCLUSION

Inhibition of the complement system by soluble complement receptor type 1 blocks local complement activation in the allograft and reduces posttransplantation reperfusion edema but does not improve hemodynamic parameters.

Solution structure of Compstatin, a potent complement inhibitor

The third component of complement, C3, plays a central role in activation of the classical, alternative, and lectin pathways of complement activation. Recently, we have identified a 13-residue cyclic peptide (named Compstatin) that specifically binds to C3 and inhibits complement activation. To investigate the topology and the contribution of each critical residue to the binding of Compstatin to C3, we have now determined the solution structure using 2D NMR techniques; we have also synthesized substitution analogues and used these to study the structure-function relationships involved. Finally, we have generated an ensemble of a family of solution structures of the peptide with a hybrid distance geometry-restrained simulated-annealing methodology, using distance, dihedral angle, and 3J(NH-Halpha)-coupling constant restraints. The Compstatin structure contained a type I beta-turn comprising the segment Gln5-Asp6-Trp7-Gly8. Preference for packing of the hydrophobic side chains of Val3, Val4, and Trp7 was observed. The generated structure was also analyzed for consistency using NMR parameters such as NOE connectivity patterns, 3J(NH-Halpha)-coupling constants, and chemical shifts. Analysis of Ala substitution analogues suggested that Val3, Gln5, Asp6, Trp7, and Gly8 contribute significantly to the inhibitory activity of the peptide. Substitution of Gly8 caused a 100-fold decrease in inhibitory potency. In contrast, substitution of Val4, His9, His10, and Arg11 resulted in minimal change in the activity. These findings indicate that specific side-chain interactions and the beta-turn are critical for preservation of the conformational stability of Compstatin and they might be significant for maintaining the functional activity of Compstatin.

A flow cytometric immunoassay to quantify adsorption of complement activation products (iC3b, C3d, SC5b-9) on artificial surfaces

Crosslinked agarose microspheres and various polystyrene microspheres were analyzed for complement components after incubation with serum at 37 degrees C for times up to 2 h. Quantification involved direct flow cytometric analysis of the beads after the bound complement proteins were indirectly fluorescently tagged by use of a monoclonal antibody against a complement protein: C5b-9, iC3b, C3d, C4d, Bb, C3a, and C1q. Calibration with fluorescein microbead standards demonstrated that the membrane attack complex (SC5b-9) was surface bound on all surfaces and that the surface concentration gradually increased to levels as high as 0.5 micrograms/cm2. Further, the surface bound represented a substantial percentage of the total generated. The iC3b level on polystyrene beads rapidly reached 0.09 micrograms/cm2 and the C3d levels were an order of magnitude less. On agarose beads the iC3b levels continually rose to 0.17 micrograms/cm2 and, as before, the C3d levels were substantially lower. The surface concentration of C4d and Bb on both surfaces were significant but less than 1.0 ng/cm2. There was minimal evidence of C3a and C1q adsorption for any surface. Use of amino-polystyrene beads moderately reduced the level of bound iC3b, C3d, and SC5b-9, whereas carboxylated beads reduced the levels by almost a factor of two. The appreciable amounts of iC3b and SC5b-9 consistently noted on the artificial surfaces tested in this paper suggests that for these two activation products in vitro analysis of material induced complement activation should also include surface analysis.

Inflammatory response to cardiopulmonary bypass: mechanisms involved and possible therapeutic strategies

BACKGROUND

Recent study of the inflammatory reactions occurring during and after cardiopulmonary bypass (CPB) has improved our understanding of the involvement of the inflammatory cascade in perioperative injury. However, the exact mechanisms of this complex response remain to be fully determined.

METHODS

Literature on the inflammatory response to CPB was reviewed to define current knowledge on the possible pathways and mediators involved, and to discuss recent developments of therapeutic interventions aimed at attenuating the inflammatory response to CPB.

RESULTS

CPB has been shown to induce complement activation, endotoxin release, leukocyte activation, the expression of adhesion molecules, and the release of many inflammatory mediators including oxygen-free radicals, arachidonic acid metabolites, cytokines, platelet-activating factor, nitric oxide, and endothelins. Therapies aimed at interfering with the inflammatory response include the administration of pharmacologic agents such as corticosteroids, aprotinin, and antioxidants, as well as modification of techniques and equipment by the use of heparin-coated CPB circuits, intraoperative leukocyte depletion, and ultrafiltration.

CONCLUSIONS

Improved understanding of the inflammatory reactions to CPB can lead to improved patient outcome by enabling the development of novel therapies aimed at limiting this response.

A human urinary protease inhibitor (ulinastatin) inhibits neutrophil extracellular release of elastase during cardiopulmonary bypass

OBJECTIVES

To determine the benefits of a human urinary protease inhibitor (ulinastatin) on postoperative pulmonary dysfunction associated with neutrophil activation during cardiopulmonary bypass.

DESIGN

A prospective, randomized, clinical study.

SETTING

The study was performed at Keio University Hospital, Tokyo.

PARTICIPANTS

Eighteen adult patients scheduled for primary cardiac surgery.

INTERVENTIONS

The patients were randomly assigned either to the control group (n = 8) or to the group (n = 10) receiving ulinastatin (600,000 U in total).

MEASUREMENTS AND MAIN RESULTS

Human neutrophil ability to release elastase in response to N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) in vitro was measured before and after cardiopulmonary bypass, together with plasma levels of neutrophil elastase complex, interleukin-B, and C3a. Intrapulmonary shunt fraction was then calculated. Neutrophil elastase release in response to fMLP significantly increased in the control group, but remained unchanged in the ulinastatin group. In addition, ulinastatin minimized the increase of plasma neutrophil elastase, independently of the production of interleukin-B or C3a. Simultaneously, ulinastatin ameliorated the increase of intrapulmonary shunt, which was correlated with extracellular elastase release.

CONCLUSIONS

Ulinastatin attenuated the elevation of fMLP-induced elastase release, which was associated with the deterioration of gas exchange during cardiopulmonary bypass. The administration of this agent has a potential to lessen the risk of postperfusion lung injury.

Neutrophil expression of CD11b/CD18 and IL-8 secretion during normothermic cardiopulmonary bypass

OBJECTIVE

To assess blood polymorphonuclear neutrophil (PMN) activation status during normothermic cardiopulmonary bypass (CPB), the expression of the PMN adhesion molecule CD11b/CD18 was measured. Basal state as well as ex vivo capacity of PMN to be stimulated by a bacterial peptide (FMLP) were investigated. Because interleukin-8 (IL-8) is known to induce CD11b/CD18 expression in vitro in PMN, IL-8 plasma levels were concomitantly measured.

DESIGN

Prospective study.

SETTING

University hospital.

PARTICIPANTS

Thirteen patients scheduled for cardiac surgery.

INTERVENTIONS

Systemic arterial and pulmonary arterial blood samples were withdrawn at the same moment during the first 4 hours after the onset of CPB.

MEASUREMENTS AND MAIN RESULTS

Twenty minutes after the onset of CPB, basal expression of PMN CD11b/CD18 was upregulated, whereas IL-8 plasma levels remained unchanged. The increase in PMN CD11b expression was maintained until the fourth hour after the onset of CPB. At this time, elevation of IL-8 plasma levels was maximal. No differences were found between pulmonary and systemic arterial IL-8 plasma levels, even after aortic unclamping. The capacity of PMN to be stimulated ex vivo by FMLP remained normal.

CONCLUSIONS

Normothermic CPB induced a fast increase in CD11b expression, which appeared to be similar to that observed during hypothermia. IL-8 was probably not related to the very early CD11b upregulation, but could be involved in pulmonary PMN sequestration during pulmonary reperfusion and contribute to the maintained expression of PMN CD11b. Although partially activated, PMNs maintain a normal capacity to respond to a further FMLP stimulation and thus to bacterial infection.

The inflammatory response and extracorporeal circulation

Defining the cause of organ and tissue dysfunction associated with the use of perfusion systems will produce methods of prevention or treatment and improve patient outcome. The problem is the plethora of triggers, effectors, and mediators in this process, which can now be measured. Each new measureable compound becomes another biochemical "smoking gun" without physiological data to show any relevance to the human problem. This review critically compares and contrasts the role of certain, largely novel, initiation, amplification, and cytotoxic mechanisms in the inflammatory response of the myocardium and pulmonary systems after a period of cardiopulmonary bypass. The available evidence strongly points to the process being different for each of these tissue beds. These data suggest that ensuring normal lung and heart functions after surgery will require separate therapeutic strategies.

Endothelial cell injury in cardiovascular surgery: the systemic inflammatory response

Many of the components currently used to perform cardiovascular operations lead to systemic insults that result from cardiopulmonary bypass circuit-induced contact activation, circulatory shock, and resuscitation, and a syndrome similar to endotoxemia. Experimental observations have demonstrated that these events have profound effects on activating endothelial cells to recruit neutrophils from the circulation. Once adherent to the endothelium, neutrophils release cytotoxic proteases and oxygen-derived free radicals, which are responsible for much of the end-organ damage seen after cardiovascular operations. Recently the cellular and molecular mechanisms of endothelial cell activation have become increasingly understood. It is conceivable that once the molecular mechanisms of endothelial cell activation are better defined, therapies will be developed allowing the selective or collective inhibition of vascular endothelial activation during the perioperative period.

Material-induced up-regulation of leukocyte CD11b during whole blood contact: material differences and a role for complement

Material-induced thrombogenicity is in part a consequence of leukocyte activation. To evaluate and compare material-induced platelet damage, we have expanded our in vitro flow cytometric immunoassay to include assessment of leukocyte activation. We have used a very simple system whereby fresh, heparinized whole blood contacts materials for 1 h at 37 degrees C under low shear. Unlike other tests that focus on adherent leukocytes, this assay evaluates the leukocytes in the whole blood drained from the tube (1.57 mm internal diameter, 25 cm length) after material contact. We demonstrate that whole blood contact with a polyvinyl alcohol (PVA) hydrogel surface leads to a twofold up-regulation in CD11b surface expression of all monocytes and neutrophils. The activation is metal-ion dependent and highly material dependent in that blood contact with polyethylene and Silastic surface leads to minimal activation. The shedding of L-selection as a marker of leukocyte activation was found to be unsuitable in our assay given it ease of shedding in resting heparinized whole blood. Further, plasma levels of complement components Bb and sC5b-9 (ELISA assays) were significantly elevated only after blood contact with PVA hydrogel surfaces (9.4 micrograms/mL sC5b-9 and 9.6 micrograms/mL Bb). Use of recombinant soluble human CR1 (sCR1) to inhibit the action of the C3 and C5 convertases completely inhibited sC5b-9 levels in whole blood after contact with PVA hydrogel surfaces and inhibited CD11b up-regulation by over 70%, suggesting that material-induced leukocyte activation is partially mediated by C5a production.

Effects of inhibition of complement activation using recombinant soluble complement receptor 1 on neutrophil CD11b/CD18 and L-selectin expression and release of interleukin-8 and elastase in simulated cardiopulmonary bypass

The inflammatory response to cardiopulmonary bypass includes activation of complement and induction of several neutrophil activation pathways. A recombinant soluble form of complement receptor 1 was used as a specific inhibitor of complement activation in simulated cardiopulmonary bypass circuits. Substantial complement activation was observed in these circuits with progressive accumulation of both plasma C3a and terminal complement complex. Soluble complement receptor 1 resulted in a significant reduction in C3a levels (p < 0.01) but did not inhibit terminal complement complex generation. A marked rise in neutrophil CD11b/CD18 expression, simultaneous loss of L-selectin expression, and a progressive accumulation of plasma elastase-alpha 1-antitrypsin occurred and were not affected by soluble complement receptor. However, generation of interleukin-8 in the circuits was inhibited (p < 0.05) by pretreatment with soluble complement receptor. These data suggest that changes in neutrophil activation seen during cardiopulmonary bypass may not be induced directly by anaphylatoxin generation.

Attenuation of cardiopulmonary bypass-derived inflammatory reactions reduces myocardial reperfusion injury in cardiac operations

In cardiac operations endopeptidase (protease) inhibitor may be beneficial in reducing myocardial injury when administered in the cardiopulmonary bypass prime. Nafamostat mesilate was evaluated in 20 patients who underwent coronary artery bypass grafting. The patients were divided into a control group (n = 10) and a nafamostat group (n = 10). Nafamostat (2 mg/kg per hour) was continuously given during cardiopulmonary bypass in the nafamostat group. The age, number of grafts, cardiopulmonary bypass time, and aortic crossclamp time were similar between groups. In the control group, neither tumor necrosis factor-alpha nor interleukin-1 levels showed any significant change during cardiopulmonary bypass, whereas interleukin-6 and interleukin-8 levels, percent expression of adhesion molecule (CD18) on neutrophils, and CH50 assay results increased significantly during cardiopulmonary bypass. As compared with the control group, the nafamostat group showed significantly lower levels of interleukin-6 (123 +/- 57 versus 40 +/- 22 pg/ml, respectively) and interleukin-8 (96 +/- 13 versus 66 +/- 14 pg/ml, respectively). The nafamostat group showed a significantly lower difference of CH50 assay results and malondialdehyde levels between coronary sinus blood and arterial blood and peak values of creatine kinase MB (43 +/- 12 IU/L versus 19 +/- 6 IU/L) during the postoperative course compared with findings in the control group. These results demonstrated that inflammatory reactions induced by cardiopulmonary bypass had adverse effects on myocardial recovery after aortic crossclamping and that nafamostat mesilate given during cardiopulmonary bypass appeared to reduce myocardial reperfusion injury by attenuating such inflammatory reactions. Attenuation of inflammatory reactions of cardiopulmonary bypass should be considered in the strategy of myocardial protection.

Hypothermia during cardiopulmonary bypass delays but does not prevent neutrophil-endothelial cell adhesion. A clinical study

BACKGROUND

An accurate evaluation of warm heart surgery cannot be limited to the assessment of the myocardial effects of warm blood cardioplegia but should also address the effects of systemic normothermia on the inflammatory response to cardiopulmonary bypass. A major component of this response is the endothelial adhesion of neutrophils, because it is linked to the release of cytotoxic compounds. This study was designed (1) to characterize the bypass-induced changes in the expression of neutrophil adhesion molecules (L-selectin and beta 2-integrins) and (2) to assess the influence of bypass temperature on these changes.

METHODS AND RESULTS

Twenty case-matched patients undergoing open-heart procedures were divided into two equal groups according to the core temperature during cardiopulmonary bypass: warm (33.4 +/- 0.3 degrees C) or cold (27.1 +/- 0.4 degrees C, P < .0001 versus warm). Arterial blood samples were collected before, during, and 30 minutes after bypass and processed for the expression of L-selectin and beta 2-integrins (CD11a, CD11b, and CD11c) with flow cytometry. Warm bypass was associated with an early and sustained upregulation of CD11b. In contrast, hypothermia resulted in a strikingly less pronounced CD11b upregulation during bypass. However, CD11b expression sharply increased thereafter so that 30 minutes after bypass, it was no longer significantly different between the two groups. Changes in CD11c expression grossly paralleled those described for CD11b. Neither CD11a nor L-selectin changed significantly from baseline values in either group.

CONCLUSIONS

Clinical cardiopulmonary bypass is associated with a marked upregulation of the neutrophil CD11b and CD11c integrins. Hypothermia delays but does not prevent the increased expression of these adhesion molecules, which could consequently represent logical targets for interventions designed to blunt the neutrophil-mediated component of bypass-induced inflammatory tissue damage.

Influence of temperature on neutrophil trafficking during clinical cardiopulmonary bypass

BACKGROUND

The adhesion of neutrophils to endothelial cells and their subsequent transendothelial migration play a major role in inflammatory damage elicited by cardiopulmonary bypass (CPB) because these events are linked to the release of cytotoxic proteases and oxidants. However, the patterns of neutrophil trafficking in relation to systemic temperature during clinical CPB have not yet been characterized.

METHODS AND RESULTS

Twenty case-matched patients undergoing warm (31.8 +/- 0.4 degrees C) or cold (26.3 +/- 0.5 degrees C, P < .0001 versus warm) bypass were studied. Blood samples were simultaneously collected from the right and left atria before, at the end of, and 30 minutes after CPB. Plasma levels of C3a, P- and E-selectins, elastase, and interleukin-8 were determined by immunoassays. The results demonstrate: (1) a rise in C3a, reflecting complement activation, (2) a fall in soluble E-selectin consistent with an increased adhesiveness of activated neutrophils, (3) a rise in soluble P-selectin expected to enhance endothelial adhesion of these neutrophils, (4) a rise in elastase, suggesting an adhesion-triggered neutrophil degranulation, and finally (5) a rise in interleukin-8 that is likely to promote transendothelial migration of adherent neutrophils. All of these changes occurred in the two groups of patients and were significant compared with prebypass values. However, in none of the groups was there a significant difference between right and left atrial values for any of the markers. The single difference between cold and warm bypass patients was a significant reduction of elastase release in the cold group (P < .001 versus the warm group).

CONCLUSIONS

Clinical CPB is associated with biological changes suggesting the occurrence of neutrophil trafficking. Hypothermia provides only partial protection through a reduced release of elastase. Overall, these results reinforce the rationale for the development of therapeutic strategies targeted at blunting the neutrophil-mediated component of bypass-induced inflammatory damage.

Blockade of C5a and C5b-9 generation inhibits leukocyte and platelet activation during extracorporeal circulation

Complement activation contributes to the systemic inflammatory response induced by cardiopulmonary bypass. At the cellular level, cardiopulmonary bypass activates leukocytes and platelets; however the contribution of early (3a) versus late (C5a, soluble C5b-9) complement components to this activation is unclear. We used a model of simulated extracorporeal circulation that activates complement (C3a, C5a, and C5b-9 formation), platelets (increased percentages of P-selectin-positive platelets and leukocyte-platelet conjugates), and neutrophils (upregulated CD11b expression). to specifically target complement activation in this model, we added a blocking mAb directed at the human C5 complement component and assessed its effect on complement and cellular activation. Compared with a control mAB, the anti-human C5 mAb profoundly inhibited C5a and soluble C5b-9 generation and serum complement hemolytic activity but had no effect on C3a generation. Additionally, the anti-human C5 mAb significantly inhibited neutrophil CD11b upregulation and abolished the increase in P-selectin-positive platelets and leukocyte-platelet conjugate formation compared to experiments performed with the control mAb. This suggests that the terminal components C5a and C5b-9, but not C3a, directly contribute to platelet and neutrophil activation during extracorporeal circulation. Furthermore, these data identify the C5 component as a site for therapeutic intervention in cardiopulmonary bypass.