Deposition of terminal C5b-9 complement complexes on erythrocytes and leukocytes during cardiopulmonary bypass

The impact of del Nido cardioplegia solution on blood morphology parameters

BACKGROUND

Crystalloid cardioplegic solutions are believed to reduce hemoglobin significantly and increase the transfusion rate. However, recent reports indicate that the del Nido cardioplegia may preserve blood morphology parameters.

METHODS

In "The del Nido versus cold blood cardioplegia in aortic valve Replacement" trial patients undergoing aortic valve replacement were randomized into the del Nido (DN) or cold blood cardioplegia (CB) group. For the subanalysis, patients who underwent blood transfusions were excluded from the study. Red blood cell (RBC) count, hemoglobin, white blood cell (WBC) count and platelet (PLT) count were measured before the surgery, 24-, 48-, and 96 hours postoperatively. Furthermore, percental variation in first-last measure was compared in groups. In addition, indexed normalized ratio (INR) and activated partial thromboplastin time (aPTT) were compared preoperatively and 24 hours after the surgery.

RESULTS

Eighteen (24%) patients from the del Nido group and 22 (29.3%) patients from the CB group received blood product transfusions (p = 0.560) and were excluded from further analysis. As such, 57 patients remained in DN group and 53 patients remained in CB group. No difference was found in RBC, hemoglobin, WBC, and platelet count in time intervals. Percental variation in first-last measure revealed higher fall in RBC (p = 0.0024) and hemoglobin (p = 0.0028) in the CB group. No difference was shown in preoperative and 24-hour postoperative INR and aPTT.

CONCLUSIONS

The del Nido cardioplegia does not decrease blood morphology parameters when compared to cold blood cardioplegia and may be used alternatively regardless of bleeding and coagulopathy risk.

Blood - Artificial Surface Interactions during Cardiopulmonary Bypass

Evaluation of the biocompatibility of four different types of oxygenator (bubble, membrane, hollow fibre and ‘hybrid’) was performed on 26 patients undergoing cardiopulmonary bypass during elective coronary surgery. More platelet derangement and an increased degree of hemolysis, revealed by higher plasmatic concentration of beta-thromboglobulin, platelet factor 4 and plasmatic free hemoglobin (p < 0.05), was seen when using the bubble oxygenator. Damage to blood cells was minimal with the membrane oxygenator while the ‘hybrid’ and the hollow fibre oxygenators proved to rank at an intermediate level. Complement activation at the beginning of the cardiopulmonary bypass occurred via the alternative pathway as demonstrated by C3adesarg increase (up to nine times) without a concomitant elevation of C4adesarg. Cardiopulmonary bypass complement activation was quantitatively similar with all the oxygenators. A further activation via the classical pathway occured in all the patients after protamine injection. Consistent differences as far as clinical and biological effects exist among the various commercially available cardiopulmonary bypass apparatus; our study provides guidelines for the evaluation and selection of devices which might reduce postoperative sequelae.

Reduced White Blood Cell Microrheology and Postoperative Complications Associated with Cardiopulmonary Bypass

The effect of cardiopulmonary bypass (CPB) trauma and damage to the white blood cells (WBC) was prospectively studied in relation to myocardial microcirculation and postoperative complications in 45 patients undergoing cor onary bypass operations for angina pectoris. The filtrability of a suspension of white cells in plasma (P-WFR) was analyzed during CPB and in the first week following coronary bypass operations for angina pectoris. The damage to white cells due to CPB reduced filtrability by about 40% (p < 0.05) and a reduced filtrability was noted even one week after successful surgery. In 25 patients the microflow in the myocardium was semiquantitatively assessed intraoperatively by laser Doppler flowmetry (LDF%), and there was a positive correlation be tween P-WFR and LDF% (r=0.84, p < 0.01). The most common complication requiring treatment was cardiac arrhythmias (atrial fibrillation or flutter 12/45, 27%). Myocardial infarction, 9%; A-V blocks, 4%; respiratory insuffi ciency, 4%; cerebrovascular accident, 2%, and infections, 4% were also noted. The trauma to the WBC during CPB appears to reduce myocardial microflow and could be a factor in triggering postoperative complications. Studies to pro tect the WBC or remove damaged WBC during and even after CPB would appear to be warranted.

Blood cell rheologic deterioration by complement activation during experimental prolonged perfusion with membrane oxygenation

In order to understand the microcirculatory disturbances during clinical ECMO, the relation of complement activation to blood cell rheologic parameters during prolonged perfusion with membrane oxygenation was studied in 10 experiments using fresh human donor blood. The perfusion set-up was a standard ECMO circuit without a patient. Blood rheologic parameters reflecting the fluidity of blood in the microcirculation were analysed by a St George's Filtrometer. Changes in complement fractions C3a and C5a were measured by the radio-immunoassay (RIA) technique and the TCC (terminal complement complex) by ELISA technique. Samples for complement activation and blood rheological analysis were taken at 24 hours for correlation. There were strong and significant correlations between red and white cell rheologic parameters with all complement fractions. These observations indicate that complement activation plays a significant role in the deterioration of blood rheology during extracorporeal circulation. Improvements in biocompatibility and blood protection are required if this technology is to be made safer.

Pathogenesis and mechanisms of antibody-mediated hemolysis

BACKGROUND

The clinical consequences of antibodies to red blood cells (RBCs) have been studied for a century. Most clinically relevant antibodies can be detected by sensitive in vitro assays. Several mechanisms of antibody-mediated hemolysis are well understood. Such hemolysis after transfusion is reliably avoided in a donor-recipient pair, if one individual is negative for the cognate antigen to which the other has the antibody.

STUDY DESIGN AND RESULTS

Mechanisms of antibody-mediated hemolysis were reviewed based on a presentation at the Strategies to Address Hemolytic Complications of Immune Globulin Infusions Workshop addressing intravenous immunoglobulin (IVIG) and ABO antibodies. The presented topics included the rates of intravascular and extravascular hemolysis; immunoglobulin (Ig)M and IgG isoagglutinins; auto- and alloantibodies; antibody specificity; A, B, A,B, and A1 antigens; A1 versus A2 phenotypes; monocytes-macrophages, other immune cells, and complement; monocyte monolayer assay; antibody-dependent cell-mediated cytotoxicity; and transfusion reactions due to ABO and other antibodies.

CONCLUSION

Several clinically relevant questions remained unresolved, and diagnostic tools were lacking to routinely and reliably predict the clinical consequences of RBC antibodies. Most hemolytic transfusion reactions associated with IVIG were due to ABO antibodies. Reducing the titers of such antibodies in IVIG may lower the frequency of this kind of adverse event. The only way to stop these events is to have no anti-A or anti-B in the IVIG products.

Clinically and/or Serologically Misleading Findings Surrounding Immune Haemolytic Anaemias

Autoimmune haemolytic anaemias (AIHAs) are well-characterized disorders. They can be differentiated from one another and from other non-immune haemolytic anaemias by clinical, laboratory and serological testing. However, several misleading clinical presentations and/or serological findings may result in misinterpretation, delay and/or misdiagnosis. Such failures are avoidable by adequate clinical and serological experience of the responsible physicians and serologists or, at least, by an optimised bidirectional communication. As long as this has not been achieved, unpleasant failures are to be expected. A true diagnosis of AIHA can neither be verified by clinical nor serological findings alone. Thus, a collective clinical and serological picture remains obligatory for fulfilling the criteria of optimal diagnosis and therapy. Ultimately, the majority of pioneer scientific and practical work in this field stems from scientists who were simultaneously involved in both the clinic and serology.

Plasma proteomic changes during hypothermic and normothermic cardiopulmonary bypass in aortic surgeries

Deep hypothermic circulatory arrest (DHCA) is a protective method against brain ischemia in aortic surgery. However, the possible effects of DHCA on the plasma proteins remain to be determined. In the present study, we used novel high-throughput technology to compare the plasma proteomes during DHCA (22°C) with selective cerebral perfusion (SCP, n=7) to those during normothermic cardiopulmonary bypass (CPB, n=7). Three plasma samples per patient were obtained during CPB: T1, prior to cooling; T2, during hypothermia; T3, after rewarming for the DHCA group and three corresponding points for the normothermic group. A proteomic analysis was performed using isobaric tag for relative and absolute quantification (iTRAQ) labeling tandem mass spectrometry to assess quantitative protein changes. In total, the analysis identified 262 proteins. The bioinformatics analysis revealed a significant upregulation of complement activation at T2 in normothermic CPB, which was suppressed in DHCA. These findings were confirmed by the changes of the terminal complement complex (SC5b-9) levels. At T3, however, the level of SC5b-9 showed a greater increase in DHCA compared to normothermic CPB, while 48 proteins were significantly downregulated in DHCA. The results demonstrated that DHCA and rewarming potentially exert a significant effect on the plasma proteome in patients undergoing aortic surgery.

Malarial anemia: digestive vacuole of Plasmodium falciparum mediates complement deposition on bystander cells to provoke hemophagocytosis

The digestive vacuole (DV) of Plasmodium falciparum, which is released into the bloodstream upon rupture of each parasitized red blood cell (RBC), was recently discovered to activate the alternative complement pathway. In the present work, we show that C3- and C5-convertases assembling on the parasitic organelle are able to provoke deposition of activated C3 and C5b-9 on non-infected bystander erythrocytes. Direct contact of DVs with cells is mandatory for the effect, and bystander complement deposition occurs focally, possibly at the sites of contact. Complement opsonization promotes protracted erythrophagocytosis by human macrophages, an effect that is magnified when ring-stage infected RBCs with reduced CD55 and CD59, or paroxysmal nocturnal hemoglobinuria (PNH)-RBCs lacking these complement inhibitors are employed as targets. Bystander attack can also directly induce lysis of PNH-RBCs. Direct evidence for complement activation and bystander attack mediated by DVs was obtained through immunohistochemical analyses of brain paraffin sections from autopsies of patients who had died of cerebral malaria. C3d and the assembled C5b-9 complex could be detected in all sections, colocalizing with and often extending locally beyond massive accumulations of DVs that were identified under polarized light. This is the first demonstration that a complement-activating particle can mediate opsonization of bystander cells to promote their antibody-independent phagocytosis. The phenomenon may act in concert with other pathomechanisms to promote the development of anemia in patients with severe malaria.

Membrane attack by complement: the assembly and biology of terminal complement complexes

Complement system activation plays an important role in both innate and acquired immunity. Activation of the complement and the subsequent formation of C5b-9 channels (the membrane attack complex) on the cell membranes lead to cell death. However, when the number of channels assembled on the surface of nucleated cells is limited, sublytic C5b-9 can induce cell cycle progression by activating signal transduction pathways and transcription factors and inhibiting apoptosis. This induction by C5b-9 is dependent upon the activation of the phosphatidylinositol 3-kinase/Akt/FOXO1 and ERK1 pathways in a Gi protein-dependent manner. C5b-9 induces sequential activation of CDK4 and CDK2, enabling the G1/S-phase transition and cellular proliferation. In addition, it induces RGC-32, a novel gene that plays a role in cell cycle activation by interacting with Akt and the cyclin B1-CDC2 complex. C5b-9 also inhibits apoptosis by inducing the phosphorylation of Bad and blocking the activation of FLIP, caspase-8, and Bid cleavage. Thus, sublytic C5b-9 plays an important role in cell activation, proliferation, and differentiation, thereby contributing to the maintenance of cell and tissue homeostasis.

Vitronectin in host pathogen interactions and antimicrobial therapeutic applications

Vitronectin (Vn) is a multifunctional glycoprotein profusely present in serum and bound to epithelial cell surfaces. It plays an important role in cell migration, tissue repair and regulation of membrane attack complex (MAC) formation. In the last decade the role of Vn has been extensively investigated in eukaryotic signalling and cell migration leading to the possibility of developing novel anticancer drugs. In parallel, several studies have suggested that pathogens utilize Vn in invasion of the host. Here we review the properties of Vn and its role in host-pathogen interactions that might be a future target for therapeutic intervention.

Donor survey to assess facial flushing during automated red cell collections and medication use

BACKGROUND

We conducted a donor survey to assess the occurrence of facial flushing and other symptoms during automated 2-U red cell collections (2RBC) and plateletpheresis (PLT) procedures and evaluated the possible association of the reactions with angiotensin-converting enzyme (ACE) inhibitors or with the collection technology.

METHODS

An online survey was developed using Zoomerang to capture details of the donors' experience and medication use after 2RBC or PLT donations in regional blood centers of the American Red Cross.

RESULTS

Between 12/16/09 and 4/19/10, 1,299 donors in five American Red Cross blood center regions completed an online survey (739 2RBC, 4.2% total registrations; 560 PLT, 2.3% total registrations). Facial flushing was reported by 29 donors, and was more likely associated with 2RBC than PLT procedures (3.0% vs. 1.3%, P = 0.03). Facial flushing with 2RBC donation was reported by eight of 72 (11%) donors on ACE inhibitors; and 14 of 667 (2%) donors who were not taking ACE inhibitors (P = 0.001). The incidence of facial flushing reactions with PLT donation was less than 2% whether donors reported ACEI inhibitor use or not. More than 95% of the donors reported their intent to donate again, regardless of symptoms.

CONCLUSION

Facial flushing was more often reported by 2RBC donors taking ACE inhibitors than other donors [11% vs. 2%; P = 0.001]; and was uncommon among PLT donors, irrespective of ACE inhibitor use (<2%). All blood donors should be informed of the potential for common, minor side effects of the collection procedure and the possible but rare occurrence of more medically serious complications.

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.

Differential effects of nitric oxide synthesis on pulmonary vascular function during lung ischemia-reperfusion injury

Lung ischemia-reperfusion (IR) injury causes alveolar, epithelial and endothelial cell dysfunction which often results in decreased alveolar perfusion, characteristic of an acute respiratory distress syndrome. Nitric oxide (NO) from endothelium-derived NO synthase (eNOS) helps maintain a low pulmonary vascular resistance. Paradoxically, during acute lung injury, overproduction of NO via inducible NO synthase (iNOS) and oxidative stress lead to reactive oxygen and nitrogen species (ROS and RNS) formation and vascular dysfunction. RNS potentiate vascular and cellular injury by oxidation, by decreasing NO bioavailability, and by regulating NOS isoforms. RNS potentiate their own production by uncoupling NO production through eNOS by oxidation and disruption of Akt-mediated phosphorylation of eNOS. This review focuses on effects of NO which cause vascular dysfunction in the unique environment of the lung and presents a hypothesis for interplay between eNOS and iNOS activation with implications for development of new strategies to treat vascular dysfunction associated with IR.

Perioperative blood transfusion and blood conservation in cardiac surgery: the Society of Thoracic Surgeons and The Society of Cardiovascular Anesthesiologists clinical practice guideline

BACKGROUND

A minority of patients having cardiac procedures (15% to 20%) consume more than 80% of the blood products transfused at operation. Blood must be viewed as a scarce resource that carries risks and benefits. A careful review of available evidence can provide guidelines to allocate this valuable resource and improve patient outcomes.

METHODS

We reviewed all available published evidence related to blood conservation during cardiac operations, including randomized controlled trials, published observational information, and case reports. Conventional methods identified the level of evidence available for each of the blood conservation interventions. After considering the level of evidence, recommendations were made regarding each intervention using the American Heart Association/American College of Cardiology classification scheme.

RESULTS

Review of published reports identified a high-risk profile associated with increased postoperative blood transfusion. Six variables stand out as important indicators of risk: (1) advanced age, (2) low preoperative red blood cell volume (preoperative anemia or small body size), (3) preoperative antiplatelet or antithrombotic drugs, (4) reoperative or complex procedures, (5) emergency operations, and (6) noncardiac patient comorbidities. Careful review revealed preoperative and perioperative interventions that are likely to reduce bleeding and postoperative blood transfusion. Preoperative interventions that are likely to reduce blood transfusion include identification of high-risk patients who should receive all available preoperative and perioperative blood conservation interventions and limitation of antithrombotic drugs. Perioperative blood conservation interventions include use of antifibrinolytic drugs, selective use of off-pump coronary artery bypass graft surgery, routine use of a cell-saving device, and implementation of appropriate transfusion indications. An important intervention is application of a multimodality blood conservation program that is institution based, accepted by all health care providers, and that involves well thought out transfusion algorithms to guide transfusion decisions.

CONCLUSIONS

Based on available evidence, institution-specific protocols should screen for high-risk patients, as blood conservation interventions are likely to be most productive for this high-risk subset. Available evidence-based blood conservation techniques include (1) drugs that increase preoperative blood volume (eg, erythropoietin) or decrease postoperative bleeding (eg, antifibrinolytics), (2) devices that conserve blood (eg, intraoperative blood salvage and blood sparing interventions), (3) interventions that protect the patient's own blood from the stress of operation (eg, autologous predonation and normovolemic hemodilution), (4) consensus, institution-specific blood transfusion algorithms supplemented with point-of-care testing, and most importantly, (5) a multimodality approach to blood conservation combining all of the above.

A new poly-2-methoxyethylacrylate-coated cardiopulmonary bypass circuit possesses superior platelet preservation and inflammatory suppression efficacy

BACKGROUND

Poly-2-methoxyethylacrylate (PMEA) is a new coating material, and several studies have revealed that PMEA-coated cardiopulmonary bypass (CPB) circuits have good biocompatibility. This study sought to compare this biocompatibility with those of heparin-coated and noncoated circuits.

METHODS

Forty-five patients undergoing coronary artery bypass grafting were randomly assigned to PMEA-coated (group P, n = 15), heparin-coated (group H, n = 15), or noncoated (group N, n = 15) circuit groups. Clinical data and the following markers were analyzed: (1) platelet preservation by number of platelets; (2) complement (C) activation by C3a and C4a levels; (3) inflammatory response by interleukin-6 (IL-6) and interleukin-8 (IL-8) levels.

RESULTS

Platelet numbers were significantly preserved in group P compared with groups N and H. Postoperative blood loss did not differ among the groups. During CPB, C3a values were significantly lower in group H (536 +/- 145 ng/mL) than in group P (1,458 +/- 433 ng/mL, p < 0.01) and group N (1,815 +/- 845 ng/mL, p < 0.01). The C4a values did not differ 60 minutes after CPB initiation among the groups. The IL-6 and IL-8 levels were significantly lower in group P and group H than in group N.

CONCLUSIONS

The PMEA coating was superior to heparin coating and noncoating in preserving platelets, and was equivalent to heparin coating in terms of the perioperative clinical course and inhibition of inflammatory cytokines, but slightly inferior in reducing complement activation.

Predictors for mortality after prolonged mechanical ventilation after cardiac surgery in children

PURPOSE

To identify early mortality-associated clinical risk factors preceding, during, and after cardiac surgery in children.

MATERIALS AND METHODS

Of the 722 children admitted to our pediatric intensive care unit (PICU) from January 1992 to January 1997 after repair of congenital heart defects, 70 required 48 hours or more of mechanical ventilation. Their clinical records were analyzed for perioperative predictors of mortality.

RESULTS

The children's ages were 3.6 +/- 4.1 years (range, 4 d-16 y). The overall mortality was 5.9%. Eleven of the 70 children (15.7%) who required mechanical ventilation for 48 hours or more did not survive compared with 30 of the 652 (4.6%) children ventilated for less than 48 hours. The preoperative predictors identified as being significantly associated with increased mortality were younger age (P <.05) and the presence of congestive heart failure (P <.01). The main cause of early postoperative mortality was multiorgan dysfunction (9 children, 81.8%), whereas septic complications also were responsible for late (< 1 wk postoperatively) death (the other 2 children, 17.2%).

CONCLUSIONS

Younger age and congestive heart failure were the main preoperative predictors of mortality. Multiorgan dysfunction and septic complication were predictive of an increased risk for death after cardiac surgery. These factors should be investigated in greater depth to assist in guiding aggressive therapeutic approaches for combating early signs of organ system dysfunction and infectious complications in these high-risk patients.

Inflammation After Cardiopulmonary Bypass: Therapy for the Postpump Syndrome

Cardiopulmonary bypass (CPB) is used in most, but not all, complex heart operations. CPB is associated with a systemic inflammatory response in adults and children. Many materials-dependent (exposure of blood to non- physiologic surfaces and conditions) and materials-in dependent (surgical trauma, ischemia-perfusion to the organs, changes in body temperature, and release of endotoxin) factors during CPB have been implicated in the etiology of this complex response. The mechanisms involved may include complement activation, release of cytokines, leukocyte activation with expression of ad hesion molecules, and production of various vasoactive and immunoactive substances. Postpump inflamma tion may lead to postoperative complications and may result in respiratory failure, renal dysfunction, bleeding disorders, neurologic dysfunction, altered liver func tion, and ultimately multiple organ failure. Significant efforts are being made to decrease the generation and effects of postpump inflammation. Interventions to this end have included avoiding CPB when possible, im proving the biocompatibility of the involved mechani cal devices, and administering medications that main tain cellular integrity. This article provides an overview of the etiology, pathophysiology, and treatment of postpump inflammation. Perhaps with additional in sight into this syndrome, CPB can be made a safer and more efficacious modality of cardiorespiratory support. Copyright© 2001 by W.B. Saunders Company.

Bradykinin production during donor plasmapheresis procedures

BACKGROUND AND OBJECTIVES

Extracorporeal circuits made of artificial substances may induce blood cells and humoral activation. Negatively charged surfaces may activate Factor XII and the prekallikrein-kinin cascade, resulting in bradykinin (BK) production. BK has been considered to be involved in severe hypotensive reactions occurring during therapeutic apheresis in patients taking angiotensin-converting enzyme (ACE) inhibitors or in those receiving platelet transfusion. In this study we investigated BK production during donor plasmapheresis procedures.

PATIENTS AND METHODS

Eighteen volunteer donors entered the study protocol. Nine of them were taking ACE inhibitors. Their blood pressure (BP) was monitored both pre- and post-apheresis, and BK determination was carried out using a competitive enzyme immunoassay (EIA), in plasma samples collected both during and at completion of the procedure. In addition, a limited number of thawed plasma units were checked for BK.

RESULTS

No side-effects were observed during the procedures. However, donors taking ACE inhibitors showed a higher variation of their systolic BP compared to those who were not taking ACE inhibitors, while diastolic BP percentage variations did not differ significantly between the two groups. The BK concentration was considerably higher in donors taking ACE inhibitors: 183 +/- 26 versus 82 +/- 6 ng/ml (P < 0.0001) after the first collection cycle and 142 +/- 20 versus 65 +/- 11 ng/ml (P < 0.0001) in the final samples. BK was also detected, at a lower concentration (15 ng/ml), in one out of four thawed plasma units obtained from donors taking ACE inhibitors and at 1 ng/ml in one out of two thawed plasma units from the control group.

CONCLUSION

Donors taking ACE inhibitors and undergoing plasmapheresis showed higher levels of BK compared to the control group. Furthermore, the detection of BK in plasma units after a freeze-thaw procedure might explain the sudden hypotensive reaction occurring during therapeutic plasma exchange when plasmapheresis units are adopted as substitution fluids. Further investigations are needed to assess the real clinical importance of the presence of BK in plasma units.

Treatment of sepsis in cardiac surgery: role of immunoglobulins

Cardiopulmonary bypass (CPB) is associated with an injury that may cause pathophysiological changes such as systemic inflammatory response syndrome, multiple organ dysfunction syndrome, and mediator-induced multiorgan failure. Systemic endotoxinaemia, release of proinflammatory cytokines, and interactions between neutrophils and endothelium have been reported to correlate with a high incidence of organ dysfunction, infection and sepsis following cardiac surgery. This review discusses the dysregulation of the immune response as a major reason for the higher susceptibility to infections following cardiac surgery, various treatment strategies to reduce CPB-induced inflammation, and especially the prophylactic use of immunoglobulins in cardiac surgery.

Intestinal tissue oxygenation and tumor necrosis factor-alpha release during systemic blood flow changes in pigs with left ventricular assist devices

We previously demonstrated that tumor necrosis factor-alpha (TNF-alpha) increased following a reduction in systemic blood flow to 60% or less of the original cardiac output using a left ventricular assist device (LVAD). The aim of this study was to investigate the effect of reducing systemic blood flow on tissue oxygenation in the gastrointestinal tract (GIT) and the consequences of this on TNF-alpha release. LVADs were implanted in 9 pigs. The aorta was clamped, and thus the LVAD flow represented the entire systemic blood flow. Plasma TNF-alpha of the superior mesenteric vein was measured at baseline and during systemic blood flow changes. Simultaneously, pH, lactate, oxygen delivery index (DO(2)I), oxygen consumption index (VO(2)I), and oxygen extraction (O(2)ER) in the GIT were measured. The pH decreased and the lactate level increased significantly (p < 0.05) at a systemic blood flow of 50% or less. The VO(2)I was positively correlated with DO(2)I. The O(2)ER increased significantly (p < 0.05) with reductions in systemic blood flow to 30% or less. There was a significant (p < 0.01) correlation between TNF-alpha and O(2)ER at levels higher than 55%. These data demonstrate that the GIT oxygenation is inadequate with a reduction in systemic blood flow to 50% and that GIT oxygenation becomes critical at a reduction of 30%. During LVAD weaning, careful attention must be given to the GIT. The pH and lactate may be good markers of the adequacy of tissue oxygenation in the GIT.

Free hemoglobin impairs cardiac function in neonatal rabbit hearts

BACKGROUND

Hemolysis caused by cardiopulmonary bypass causes renal dysfunction and other organ failure presumably by superoxide production catalyzed by iron derived from free hemoglobin (f-Hb). It might also impair cardiac function by the same mechanism, especially in the ischemia-reperfusion period and in neonates where serum antioxidant activity is lower than adults.

METHODS

We evaluated effects of f-Hb on cardiac function with or without ischemia and reperfusion using a newborn (7 days old) rabbit crystalloid-perfused Langendorff model. After baseline measurements, the hearts were divided into the following four groups (8 hearts per group): (1) those perfused with regular Krebs-Henseleit bicarbonate buffer, (2) those perfused 30 minutes with KH buffer containing 1 mg/mL of f-Hb obtained from osmotic hemolysis, (3) those subjected to 180 minutes of cold global ischemia with infusion of crystalloid cardioplegia and reperfused with Krebs-Henseleit buffer, and (4) those subjected to the same ischemia and reperfused with Krebs-Henseleit buffer containing 1 mg/mL of f-Hb. The left ventricular function (using conductance catheter and isovolumic balloon) and coronary flow were measured.

RESULTS

Free hemoglobin significantly impaired not only left ventricular function but also coronary flow even without ischemia (p < 0.05). When ischemia and reperfusion were involved, the group reperfused with f-Hb showed the worst left ventricular function and coronary flow among the groups.

CONCLUSIONS

This study shows that f-Hb directly impaired cardiac function and coronary flow in neonatal hearts especially in ischemia and reperfusion.

Complement activation in coronary artery bypass grafting patients without cardiopulmonary bypass: the role of tissue injury by surgical incision

STUDY OBJECTIVES

Complement activation is a trigger in inducing inflammation in patients who undergo coronary artery bypass grafting (CABG) and is usually thought to be induced by the use of cardiopulmonary bypass (CPB). In this study, we examined whether tissue injury caused by chest surgical incision per se contributes to complement activation in CABG patients.

DESIGN

Prospective study.

SETTING

Thorax center in university hospital.

PATIENTS

Twenty-two patients undergoing CABG without CPB were prospectively divided into two groups: a small chest incision via an anterolateral thoracotomy representing a minimized tissue injury (lateral group, n = 8), and a conventional median sternotomy representing a large tissue injury (median group, n = 14). Biochemical markers indicating complement activation as well as systemic inflammatory response were determined before, during, and after the operation.

MEASUREMENTS AND RESULTS

Plasma concentrations of complement 3a increased in both the lateral and median groups right after chest incision (p < 0.01 and p < 0.05, respectively) and by the end of operation increased only in the median group (p < 0.01). The terminal complement complex 5b-9 did not increase in the lateral group, but it did increase in the median group both after incision and by the end of the operation (p < 0.05 and p < 0.05, respectively). During surgery, complement 4a did not increase, suggesting that it is the alternative rather than the classic pathway that is involved in complement activation by tissue injury. Postoperatively, interleukin-6 production was greater in the median group (p < 0.01) than the lateral group (p < 0.05), suggesting a more pronounced inflammatory response to a larger chest incision.

CONCLUSIONS

Tissue injury caused by surgical incision contributes to complement activation in CABG patients who are operated on without CPB. A small anterolateral thoracotomy is associated with reduced complement activation in comparison with a median sternotomy.

Total complement inhibition: an effective strategy to limit ischemic injury during coronary revascularization on cardiopulmonary bypass

BACKGROUND

Activation of complement during revascularization of ischemic myocardium accentuates myocardial dysfunction. Soluble human complement receptor type 1 (sCR1) is a potent inhibitor of complement, as are heparin-bonded (HB) cardiopulmonary bypass (CPB) circuits. This study sought to determine whether total complement inhibition with the combination of sCR1 and HB-CPB limits damage during the revascularization of ischemic myocardium.

METHODS AND RESULTS

In 40 pigs, the second and third diagonal coronary arteries were occluded for 90 minutes, followed by 45 minutes of cardioplegic arrest and 180 minutes of reperfusion. In 10 pigs, sCR1 (10 mg/kg) was infused 5 minutes after the onset of coronary occlusion (sCR1), 10 received HB-CPB only (HB-CPB), 10 received sCR1 and HB-CPB (sCR1+HB), and 10 received neither sCR1 or HB-CPB (unmodified). Addition of sCR1 to the HB group resulted in less myocardial tissue acidosis (DeltapH = -0.72+/-0.03 for unmodified; -0.46+/-0.05 for HB; -0.18+/-0.04 for sCR1; -0.13+/-0.01 for sCR1+HB), better recovery of wall motion scores (4 = normal to -1 = dyskinesia; 1.67+/-0.17 for unmodified; 2.80+/-0.08 for HB; 3.35+/-0.10 for sCR1; 3.59+/-0.08 for sCR1+HB), less lung water accumulation (5.46+/-0.28% for unmodified; 2.39+/-0.34% for HB; 1.22+/-0.07% for sCR1; 1.24+/-0.13% for sCR1+HB), and smaller infarct size (area necrosis/area risk = 44.6+/-0.7% for unmodified; 33.2+/-1.9% for HB; 19.0+/-2.4% for sCR1; 20+/-1.0% for sCR1+HB) (P<0.05 versus unmodified; P<0.05 versus unmodified and HB groups).

CONCLUSIONS

Total complement inhibition with sCR1 and sCR1+HB circuits optimizes recovery during the revascularization of ischemic myocardium.

Nucleated red blood cells after cardiopulmonary bypass in infants and children: is there a relationship to the systemic inflammatory response syndrome?

In a retrospective case control study we aimed to evaluate whether infants and children with nucleated red blood cells (NRBCs) in their peripheral blood smears after cardiopulmonary bypass (CPB) had longer bypass times than controls without NRBCs. On review of a 3-year period, 58 children with NRBCs after CPB (and without NRBCs prior to CPB) were identified (cases). A random sample of 100 children without NRBCs after CPB over the same period served as controls. The median age (range) of the children with NRBCs and without NRBCs was 0.6 years (2 days to 20 years) and 1.4 years (2 days to 16 years), respectively (p = 0.03). The children with NRBCs had a significantly longer bypass time than the controls (mean, standard deviation (SD): 114 min, 50 vs 79 min, 46 min; p < 0.0001). For the patients with postoperative polychromasia alone, the mean CPB time (111 min, SD 46 min) was also significantly longer than the respective time in the controls (p < 0.001). Markers of organ dysfunction (renal failure, use of inotropic support, time of endotracheal intubation, stay in intensive care unit and stay in hospital) were significantly more frequent/longer in the NRBC group. Post-CPB release of NRBCs is associated with longer CPB time. This alteration may be part of the CPB-related systemic inflammatory response syndrome.

Leucocyte filtration during cardiopulmonary reperfusion in coronary artery bypass surgery

Postoperative organ dysfunction after cardiac operations has been related to the damaging effects of cardiopulmonary bypass (CPB). These complications are considered to be mediated partly by complement activation and subsequent activation of leucocytes due to the contact between blood and the large nonendothelial surfaces in the bypass circuit. Removal of leucocytes by filtration during the reperfusion period may potentially reduce the postoperative morbidity after CPB. Forty patients undergoing elective, primary coronary artery bypass grafting were randomized to initial identical bypass circuits until the aortic crossclamp was released. Then, the ordinary arterial line filter was closed and either a leucocyte depletion filter (n = 20), or a control filter (n = 20) was incorporated in the circuits during the reperfusion period of CPB. Blood samples were drawn at fixed intervals and analysed for white blood cell and platelet counts, plasma concentration of myeloperoxidase, C3-complement activation products, the terminal complement complex, and interleukins (IL)-6 and -8. The numbers of circulating white blood cells in the leucocyte-depleted group decreased during the reperfusion period from 5.5 (4.8-6.8) to 5.3 (4.4-6.2) x 10(9)/l, and increased in the control group from 6.5 (5.1-8.0) to 7.4 (5.7-9.0) x 10(9)/l. Two hours postoperatively the total white blood cell count in the leucocyte-depleted group was 14.7 (12.1-17.2) x 10(9)/l, and in the control group 17.6 (14.5-20.7) x 10(9)/l. The differences between the groups were statistical significant (p = 0.05). There were no statistically significant differences between the groups with regard to other test parameters or clinical data. We conclude that the use of leucocyte filters during the reperfusion period in elective coronary artery bypass surgery significantly reduced the number of circulating leucocytes, whereas no effects were seen for granulocyte activation measured as myeloperoxidase release, platelet counts, complement activation, or IL-6 and -8 release. The clinical benefit of leucocyte filters in routine or high risk patients remains to be demonstrated and is suggested to be dependent on both the efficacy and the biocompatibility of the filters.

Increased susceptibility to erythrocyte C5b-9 deposition and complement-mediated lysis in chronic renal failure

BACKGROUND

Decreased red blood cell survival contributes to the anemia of chronic renal failure patients. Because patients on chronic dialysis therapy are frequently exposed to excessive complement activation, we investigated the susceptibility of this patient population to erythrocyte C5b-9 deposition, complement-mediated lysis, and ghost formation.

METHODS

We developed a flow cytometric assay using antibodies to both glycophorin and the C5b-9 complex to detect C5b-9 deposition on intact erythrocytes and erythrocyte ghosts. Serum C5b-9 levels and C5b-9 deposition on erythrocyte ghosts were measured by enzyme-linked immunosorbent assay.

RESULTS

A significant increase in C5b-9 deposition on intact erythrocytes was demonstrated in patients with advanced chronic renal failure (2.2 +/- 0.5%) and in patients on chronic maintenance hemodialysis (2.3 +/- 0.4%) compared with normal volunteers (0.9 +/- 0.1%, P = 0.005 vs. chronic renal failure, P < 0.001 vs. chronic hemodialysis patients). There was also a significantly higher percentage of C5b-9-positive erythrocyte ghosts in patients with advanced chronic renal failure (20.6 +/- 5%) and in chronic hemodialysis patients (15.5 +/- 3.1%) compared with normal controls (2.6 +/- 0.9%, P < or = 0.001 vs. advanced chronic renal failure and chronic hemodialysis patients). Treatment of erythrocyte preparations with cobra venom factor, which activates the complement cascade, resulted in dramatic increases in the percentages of C5b-9-positive erythrocyte ghosts in patients with chronic renal failure (49.9 +/- 6.9%) and in chronic hemodialysis patients (45.0 +/- 4.2%) compared with normal volunteers (22.3 +/- 2.7%, P < 0.001 vs. chronic renal failure and chronic hemodialysis patients). Erythrocyte membrane expression of the complement regulatory proteins CD59 and CD55 did not significantly differ between normal controls and hemodialysis patients. Plasma C5b-9 levels after cobra venom factor stimulation were higher in chronic renal failure patients (538 micrograms/ml) compared with normal controls (345 micrograms/ml, P < 0.001).

CONCLUSIONS

Patients with chronic renal failure and on hemodialysis therapy are susceptible to erythrocyte C5b-9 deposition with subsequent lysis and ghost formation. Susceptibility to complement-mediated erythrocyte injury may contribute to the anemia of chronic renal disease.

Complement-mediated acute effects of liposome-encapsulated hemoglobin

Recent studies on liposome-encapsulated hemoglobin (LEH) have indicated that this potential blood substitute can activate the complement (C) system of rats, pigs and man. The reaction can involve both the classical and the alternative pathways, and is mediated, in part, by the binding of natural anti-lipid antibodies to the lipid membrane of liposomes. The significance of these discoveries lies in the fact that C activation appears to be the primary cause of the acute physiological, hematological and laboratory changes that have been observed previously in rats and pigs following the administration of LEH or liposomes, which changes include pulmonary vasoconstriction with decreased cardiac output. In light of the proposed use of LEH as an emergency blood substitute, the latter impairment of cardiopulmonary function may warrant particular circumspection as it could aggravate the clinical state of trauma patients who are prone to develop respiratory distress partly as a consequence of C activation by the injury. Our studies on rats and pigs suggest that the above acute side effects of LEH, including the cardiopulmonary distress, can be efficiently inhibited with soluble complement receptor type I, a specific inhibitor of C activation.

Presence of vitronectin and activated complement factor C9 on ventriculoperitoneal shunts and temporary ventricular drainage catheters

OBJECT

The pathogenesis of cerebrospinal fluid (CSF) shunt infection is characterized by staphylococcal adhesion to the polymeric surface of the shunt catheter. Proteins from the CSF--fibronectin, vitronectin, and fibrinogen--are adsorbed to the surface of the catheter immediately after insertion. These proteins can interfere with the biological systems of the host and mediate staphylococcal adhesion to the surface of the catheter. In the present study, the presence of fibronectin, vitronectin, and fibrinogen on CSF shunts and temporary ventricular drainage catheters is shown. The presence of fragments of fibrinogen is also examined.

METHODS

The authors used the following methods: binding radiolabeled antibodies to the catheter surface, immunoblotting of catheter eluates, and scanning force microscopy of immunogold bound to the catheter surface. The immunoblot showed that vitronectin was adsorbed in its native form and that fibronectin was degraded into small fragments. Furthermore, the study demonstrated that the level of vitronectin in CSF increased in patients with an impaired CSF-blood barrier. To study complement activation, an antibody that recognizes the neoepitope of activated complement factor C9 was used. The presence of activated complement factor C9 was shown on both temporary catheters and shunts.

CONCLUSIONS

Activation of complement close to the surface of an inserted catheter could contribute to the pathogenesis of CSF shunt infection.

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.

Measures to control blood activation during assisted circulation

Major improvements in heart assist devices have allowed prolonged mechanical circulatory support with successful subsequent weaning or heart transplantation. The contact of blood with biomaterials used in life-sustaining devices and numerous biomaterial-independent factors elicit a systemic inflammatory response, which involves activation of various plasma protein systems and blood cells. Prolonged mechanical circulatory support elicits a systemic inflammatory response and hemostatic perturbations similar to that reported during cardiopulmonary bypass. However, in the setting of prolonged assistance, time has a complex and ill-known influence on blood activation. Methods to reduce blood activation during prolonged assisted circulation are derived from cardiopulmonary bypass investigations. Improving the biocompatibility of artificial devices can be achieved either by biomaterial surface modifications, by inhibition of biologic cascades leading to blood activation, or by controlling end points of biologic cascades. However, the necessity to respect the integrity of the organism during prolonged assistance precludes most systemic interventions and limits the control of blood activation to the area of the device.

Complement activation in injured patients occurs immediately and is dependent on the severity of the trauma

In order to study the factors related to complement activation, the complement activation products C3bc and TCC were measured in plasma at admittance and during the stay in the intensive care unit in 108 consecutive patients with multiple injuries. These patients were admitted to the surgical department during a 4-month period. Complement activation occurred immediately after the trauma and correlated strongly with the Injury Severity Score and was inversely correlated to the Base Excess. Complement activation also correlated with the number of transfusions. Sepsis caused complement activation later during the stay in hospital. All seven patients developing the adult respiratory distress syndrome (ARDS) had increased complement activation, either on admission or later during the stay in the intensive care unit. Complement activation is known to contribute to organ damage following ischemia and reperfusion. Clinical studies have demonstrated the importance of early restoration of adequate circulation and the present demonstration of a strong negative correlation between complement activation and Base Excess indicates that early restoration of aerobic metabolism may reduce complement activation and the risk for organ dysfunction.

White blood cell counts and plasma C3a have synergistic predictive value in patients at risk for acute respiratory distress syndrome

OBJECTIVE

To investigate and select nonassociated variables with predictive value for acute respiratory distress syndrome (ARDS) in patients at risk.

DESIGN

Prospective, observational study.

SETTING

A university hospital intensive care unit.

PATIENTS

Twenty-four critically ill patients with different risk factors for ARDS.

INTERVENTIONS

Arterial and mixed venous blood, as well as urine samples, were collected. Invasive hemodynamic measurements were performed.

MEASUREMENTS AND MAIN RESULTS

Fifty-nine variables pertaining to the cardiorespiratory, hepatic, immunologic, and renal systems and including plasma complement activation products C3a and SC5b-9 and polymorphonuclear elastase, were determined every 6 hrs for 3 days in patients at risk for ARDS. Associations among variables were investigated and the predictive value of nonassociated variables for ARDS was determined. Patients who developed ARDS (n=8) had lower white blood cell counts at the time they entered the study (p=.006) and during the first 24 hrs thereafter (p=.032). Also, plasma C3a concentrations were markedly higher during the first 24 hrs in patients who developed ARDS (p=.006). Plasma C3a had better predictive value than did white blood cell counts for cutoff points set by discriminant analysis at 1075 ng/mL (1.075 x 10(-3) g/L) and 5700 cells/mL, respectively. The combination of both variables in a discriminant function improved the predictive value for ARDS.

CONCLUSIONS

The most notable and nonassociated alterations observed in patients who developed ARDS were lower white blood cell counts and higher plasma C3a concentrations compared with counts and concentrations in patients who did not develop ARDS. Plasma C3a concentrations showed better predictive value than white blood cell counts. The combination of white blood cell counts with plasma C3a concentrations synergistically improved the predictive value for ARDS. This combination may prove useful for identifying subpopulations at highest risk for ARDS and may contribute to make treatment at an early stage of the syndrome possible.

Cardiopulmonary bypass circuit treated with surface-modifying additives: a clinical evaluation of blood compatibility

BACKGROUND

The cardiopulmonary bypass (CPB) circuit induces blood activation and a systemic inflammatory response in cardiac surgical patients. The CPB circuit treated with surface-modifying additive (SMA) has been found to reduce blood activation by in vitro and ex vivo experiments. This study evaluates the surface thrombogenicity and complement activation of SMA circuits during clinical CPB.

METHODS

Twenty patients undergoing coronary artery bypass grafting were randomly divided into two groups. In the SMA group (n = 10), all blood-contacting surfaces in the CPB circuit were treated or coated with SMA, whereas in the control group (n = 10) patients were perfused with an identical circuit without treatment.

RESULTS

During CPB, platelet count and beta-thromboglobulin were found similar in both the SMA and the control groups. Prothrombin activation indicated by fragment F1 + 2 was found less in the SMA group (p < 0.05). After CPB, platelet deposition on the CPB circuit was significantly less (p < 0.05) in the SMA group than in the control group as assessed by the labeled monoclonal antibody against platelet glycoprotein IIIa. Complement activation identified by C3a and terminal complex C5b-9 did not differ between the two groups, but C4a generation was less in the SMA group (p < 0.05). Leukocyte activation identified by elastase and cytokine release indicated by interleukin-8 were found uniformly in both groups. Postoperatively, chest tube drainage, blood transfusion, duration of ventilatory support, as well as the intensive care unit and hospital stay were not significantly different between the two groups.

CONCLUSIONS

These preliminary clinical results suggest that SMA inhibits platelet interaction with the biomaterial surface of the CPB circuit. Complement activation assessed by the terminal complement complex is not influenced by SMA. The clinical benefit of this surface-modifying technique has yet to be assessed in a larger population of patients undergoing cardiac operations.

Immunological effects of therapeutic immunoadsorption with respect to biocompatibility

The activation of the complement system leading to generation of anaphylatoxins and the membrane attack complex depends on the chemical nature of the adsorptive system and the anticoagulation used. The method of the primary separation determines the presence of cell debris in the plasma as well as the extent of platelet activation. The particular role of anticoagulation and its properties to prevent/reduce complement activation on immunadsorption material is discussed and the combined use of citrate and heparin is proposed. The quality of the reinfused plasma--as discussed on the example of LDL-apheresis--is therefore influenced by the amount of the activated split products. This determines finally the extent of cellular activation during therapeutic immunadsorption when receptor-dependent activation of cells by C3a(desarg) and C5a(desarg) can occur.

Complement and contact activation during cardiovascular operations in infants

BACKGROUND

By comparing the results of cardiac operations with or without cardiopulmonary bypass (CPB) in infants in a prospective study, we sought to determine which part of the postoperative systemic inflammatory response was caused by CPB.

METHODS

Thirty-five patients were divided into two groups: 11 infants operated on without CPB and 24 infants operated on with CPB. Blood samples were drawn before, during, and after the operation. We assessed complement function and the concentrations or activities of C1q, C3, C4, C1 inhibitor, factor B, the activated split product C3a, and prekallikrein and factor XIIa of the contact system.

RESULTS

All of the patients exhibited a decrease of complement proteins. This was greater in infants who underwent CPB. A increase in C3a and factor XIIa and changes in prekallikrein activity occurred only in infants during CPB.

CONCLUSIONS

Complement activation occurs in all infants, but is significantly higher in the group with CPB. Contact activation only occurs in patients who undergo CPB. Thus, the inflammatory response is caused by the use of a CPB circuit and to a lesser degree by surgical procedures and anesthesia.

Results of extracorporeal membrane oxygenation in children with sepsis. The Extracorporeal Life Support Organization

BACKGROUND

Despite good results in neonates, extracorporeal membrane oxygenation (ECMO) is less well accepted in pediatric patients. Older children frequently undergo ECMO for severe bacterial, viral, or aspiration pneumonia and many have coexisting systemic sepsis. We reviewed data from a national registry to study the influence of sepsis on survival from ECMO.

METHODS

Six hundred fifty-five patients (aged 2 weeks to 17 years) with respiratory failure treated with ECMO were divided into two groups by the presence (n = 76) or absence (n = 579) of sepsis. Groups were compared by univariate analysis and by multivariate logistic regression that considered 10 additional pre-ECMO variables (age, sex, weight, arterial blood gas results, ventilator parameters, and renal failure).

RESULTS

By univariate analysis, survival was lower in septic children (36.8% versus 51.6%; p < 0.02). However, by multivariate analysis, sepsis was not an independent survival predictor (odds ratio, 0.578; 95% confidence interval, 0.288-1.162; p = 0.12). The ECMO complications predicted by the presence of sepsis included (1) seizures, (2) other neurologic complications, and (3) infection at other sites (all p < 0.05).

CONCLUSIONS

Systemic sepsis does not independently influence survival in pediatric ECMO. This therapy should not be withheld solely because of sepsis, although neurologic complications may occur more frequently.

Vitronectin-binding staphylococci enhance surface-associated complement activation

Coagulase-negative staphylococci are well recognized in medical device-associated infections. Complement activation is known to occur at the biomaterial surface, resulting in unspecific inflammation around the biomaterial. The human serum protein vitronectin (Vn), a potent inhibitor of complement activation by formation of an inactive terminal complement complex, adsorbs to biomaterial surfaces in contact with blood. In this report, we discuss the possibility that surface-immobilized Vn inhibits complement activation and the effect of Vn-binding staphylococci on complement activation on surfaces precoated with Vn. The extent of complement activation was measured with a rabbit anti-human C3c antibody and a mouse anti-human C9 antibody, raised against the neoepitope of C9. Our data show that Vn immobilized on a biomaterial surface retains its ability to inhibit complement activation. The additive complement activation-inhibitory effect of Vn on a heparinized surface is very small. In the presence of Vn-binding strain, Staphylococcus hemolyticus SM131, complement activation on a surface precoated with Vn occurred as it did in the absence of Vn precoating. For S. epidermidis 3380, which does not express binding of Vn, complement activation on a Vn-precoated surface was significantly decreased. The results could be repeated on heparinized surfaces. These data suggest that Vn adsorbed to a biomaterial surface may serve to protect against surface-associated complement activation. Furthermore, Vn-binding staphylococcal cells may enhance surface-associated complement activation by blocking the inhibitory effect of preadsorbed Vn.

Heparin coating with aprotinin reduces blood activation during coronary artery operations

BACKGROUND

This study was performed to evaluate whether the combination of heparin-coated extracorporeal circuits (ECC) and aprotinin treatment reduce blood activation during coronary artery operations.

METHODS

Sixty patients were prospectively divided into two groups (heparin-coated ECC and uncoated ECC groups), which were comparable in terms of age, sex, left ventricular function, preoperative aspirin use and consequent intraoperative aprotinin use, number of grafts, duration of aortic cross-clamping, and duration of cardiopulmonary bypass. Blood activation was assessed at different times during cardiopulmonary bypass by determination of complement activation (C3 and C4 activation products C3b/c and C4b/c and terminal complement complex), leukocyte activation (elastase), coagulation (scission peptide fibrinopeptide 1 + 2), and fibrinolysis (D-dimers).

RESULTS

Univariate analysis showed that heparin-coated ECC, under conditions of standard heparinization, did not reduce perioperative blood loss and need for transfusion. Heparin coating, however, reduced maximum values of C3b/c (446 +/- 212 nmol/L versus 632 +/- 264 nmol/L with uncoated ECC; p = 0.0037) and maximum C4b/c values (92 +/- 48 nmol/L versus 172 +/- 148 nmol/L with uncoated ECC; p = 0.0069). Levels of terminal complement complex, elastase, fibrinopeptide 1 + 2, and D-dimers were not significantly modified by the use of heparin-coated ECC. Multivariate analysis showed that the intergroup differences in maximum C3b/c and C4b/c values were more pronounced in women in part with high baseline values of C3b/c. We also found that aprotinin contributed to the reduction of maximum values of fibrinopeptide 1 + 2 and D-dimers, whereas heparin coating had no significant influence on these parameters.

CONCLUSIONS

We found no evidence of combined properties of heparin-coated ECC and aprotinin in reducing complement activation, coagulation, and fibrinolysis. We therefore recommend use of both together to achieve maximal reduction of blood activation during cardiopulmonary bypass for coronary artery operations.

Intraoperative autologous blood donation preserves red cell mass but does not decrease postoperative bleeding

BACKGROUND

Postoperative bleeding and transfusion remain a source of morbidity and cost after open heart operations. The benefit of the acute removal and reinfusion of fresh autologous blood around the time of cardiopulmonary bypass-a technique known as intraoperative autologous donation (IAD)-has not been universally accepted. We sought to more clearly evaluate the effects of IAD on allogeneic transfusion and postoperative bleeding by removing, preserving, and reinfusing a calculated maximum volume of fresh autologous whole blood.

METHODS

Ninety patients undergoing coronary artery bypass grafting or valvular operations were prospectively randomized to either have (IAD group) or not have (control group) calculated maximum volume IAD performed. Treatment was otherwise identical. Transfusion guidelines were uniformly applied to all patients.

RESULTS

An average volume of 1,540 +/- 302 mL of fresh autologous blood was removed and reinfused in the IAD group. Postoperative hematocrits were significantly greater at 12 and 24 hours postoperatively in the IAD group versus the control group despite a significant decrease in both the percentage of patients in whom allogeneic red blood cells were transfused (17% versus 52%; p < 0.01) and the number of red blood cell units transfused per patient per group (0.28 +/- 0.66 and 1.14 +/- 1.19 units; p < 0.01). Conversely, chest tube output, incidence of excessive postoperative bleeding, postoperative prothrombin time, and platelet and coagulation factor transfusion requirement did not differ between groups.

CONCLUSIONS

These results indicate that intraoperative autologous donation serves to preserve red blood cell mass. Its routine use in eligible patients is therefore justified. However, the removal and reinfusion of an individually calculated maximum volume of fresh autologous blood had no effect on postoperative bleeding or platelet and coagulation factor transfusion requirement. This lack of hemostatic effect belies the beliefs of many about the primary action of IAD, helps to delineate the optimal way in which to perform IAD, and carries implications regarding the use of allogeneic platelet and coagulation factors for the treatment of early postoperative bleeding.

Clinical outcome after coronary surgery with heparin-coated extracorporeal circuits for cardiopulmonary bypass

In this prospective randomized trial, we studied whether heparin-coated extracorporeal circuits (ECC), known to reduce complement activation, could improve the clinical outcome of 200 patients undergoing coronary artery surgery. Patients have been divided into two groups (heparin-coated ECC and uncoated ECC groups) which were similar in terms of age, gender, left ventricle function, preoperative aspirin use and consequent intraoperative aprotinin use, number of grafts, duration of aortic cross-clamping and cardiopulmonary bypass. Univariate analysis showed that heparin coating did not reduce significantly postoperative bleeding (640 +/- 311 versus 682 +/- 342 ml with uncoated ECC) nor the need for transfusion (19% of patients versus 25% with uncoated ECC). Adverse events, including all mortality and morbidity noticed during the five first postoperative days, occurred in 20 patients of the uncoated ECC group and in eight patients of the heparin-coated ECC group (p = 0.013). The most frequent complications were supraventricular arrhythmias that occurred in 13 patients of the uncoated ECC group and in four patients of the heparin-coated ECC group (p = 0.02). Multivariate analysis by stepwise logistic regression showed that only heparin coating of the ECC was shown as a significant predictive factor of adverse events reduction (p = 0.01; odds ratio = 0.34). These data suggest that heparin coating reduced postoperative complications in patients undergoing coronary artery surgery.

Centrifugal pump and heparin coating improves cardiopulmonary bypass biocompatibility

BACKGROUND

Centrifugal pumps are being used increasingly for short-term extracorporeal circulation purposes such as during heart operations. Whether the centrifugal pump improves the cardiopulmonary bypass biocompatibility has not been fully documented.

METHODS

A roller pump (n = 20) was compared in vivo with a centrifugal pump (n = 20) in groups of patients in which cardiopulmonary bypass circuits that were either totally heparin coated (Carmeda BioActive Surface; n = 20) or uncoated (n = 20) were used. We expected the heparin coating to attenuate blood activation, thus possibly making the comparison of the two pumps easier with respect to their different blood activation potentials. Samples of blood plasma, obtained during cardiopulmonary bypass from low-risk coronary artery bypass grafting patients, were analyzed for hemolysis (plasma haemoglobin), complement activation (C3bc and the terminal complement complex), a complement lytic inhibitor (vitronectin), coagulation activation (fibrinopeptide A), granulocyte activation (lactoferrin), and platelet activation (beta-thromboglobulin).

RESULTS

The concentrations of terminal complement complex, lactoferrin, and beta-thromboglobulin were significantly lower in association with heparin-coated surfaces. The concentration of plasma hemoglobin was significantly lower in association with the centrifugal pump. In uncoated circuits, the beta-thromboglobulin level was significantly higher in association with the roller pump than with the centrifugal pump, but this significant reduction in the beta-thromboglobulin level did not hold true for the heparin-coated circuit group.

CONCLUSIONS

A heparin-coated cardiopulmonary bypass surface reduces the blood activation potential during cardiopulmonary bypass, and the centrifugal pump causes less hemolysis than the roller pump.

Changes in platelet, granulocyte, and complement activation during cardiopulmonary bypass using heparin-coated equipment

The effects of heparin-coated cardiopulmonary bypass (CPB) systems on platelet, granulocyte, and complement activation were investigated during cardiopulmonary bypass. Thirty patients underwent coronary artery bypass surgery with a heparin-coated (Carmeda Bio-Active Surface, CBAS, Medtronic, U.S.A.) CPB system (HC group, n = 10), a heparin-coated oxygenator and uncoated CPB circuit (HO group, n = 10), or an uncoated system (UC group, n = 10). In the HO group, plasma C3a (1667 +/- 632 ng/ml) and C4a (1088 +/- 319 ng/ml) concentrations were significantly (p < 0.05) lower than in the UC group (2846 +/- 1045 ng/ml and 1494 +/- 480 ng/ml, respectively) 10 min after the administration of protamine, but there were no significant differences in the platelet or granulocyte counts. In the HC group, granulocyte elastase concentrations 120 min after the onset of CPB (365 +/- 177 micrograms/L) and 10 min after the administration of protamine (676 +/- 314 micrograms/L) were significantly (p < 0.05) lower than in the other 2 groups (820 +/- 341 and 893 +/- 303 micrograms/L and 1365 +/- 595 and 1,258 +/- 622 micrograms/L). In addition, the increase in the plasma C3a concentration in the HC group 60 (p < 0.05) and 120 min after the onset of CPB (p < 0.05) was significantly less than in the other 2 groups. The C3a and C4a concentrations 10 min after the administration of protamine were significantly (p < 0.005 and p < 0.05) less in the HC group than in the UC group. Platelet counts 10 min after the administration of protamine were significantly higher (p < 0.05) and plasma beta-thromboglobulin concentrations during CPB were significantly lower in the HC group than in the other 2 groups 5 (p < 0.05), 60, and 120 min (p < 0.005) after the onset of CPB. Postoperative blood loss during the first 12 h in the HC group was significantly (p < 0.05) less than that in the UC group. The heparin-coated oxygenator and uncoated CPB circuit reduced complement activation but demonstrated no significant effects on the platelet and granulocyte systems. However, the heparin-coated CPB circuit (with all components making blood contact) reduced platelet, granulocyte, and complement activation and significantly reduced postoperative blood loss. Therefore, heparin coating of CPB systems improves biocompatibility.

Heparin-coated circuits and aprotinin prime for coronary artery bypass grafting

BACKGROUND

The biocompatibility of an extracorporeal circuit is improved by heparin bonding onto its inner surface. To determine the effect of heparin-coated circuits for cardiopulmonary bypass with aprotinin prime on postoperative recovery and resource utilization, a prospective study was done in 102 patients undergoing coronary artery bypass grafting with full systemic heparinization.

METHODS

Patients were randomly allocated to be treated with either a heparin-coated circuit (n = 51) or an uncoated circuit (n = 51). Differences in blood loss, need for blood transfusion, morbidity, and intensive care stay were analyzed.

RESULTS

No differences in blood loss and need for blood transfusion were found between the groups. The relative risk for adverse events in the heparin-coated group was 0.29 (95% confidence interval ranging from 0.10 to 0.80). Adverse events included myocardial infarction (2 patients in the uncoated group versus 0 in the heparin-coated group), rethoracotomy for excessive bleeding (1 versus 2), rhythm disturbance (7 versus 2), respiratory insufficiency (4 versus 0), and neurologic dysfunction (2 versus 0). The lower incidence of adverse events in the heparin-coated group was associated with a shorter intensive care stay (median, 2 days; range, 2 to 5 days) compared with the uncoated group (median, 3 days; range, 2 to 19 days, p = 0.03). The cost savings of 1 day of intensive care stay counterbalanced the additional costs of heparin-coated circuits.

CONCLUSIONS

The use of heparin-coated circuits for cardiopulmonary bypass with aprotinin prime resulted in a significant reduction in mobidity in the early postoperative phase and a concomitant decrease in intensive care stay, resulting in important cost savings.

Specific complement inhibition with heparin-coated extracorporeal circuits

BACKGROUND

Although it is well established that heparin-coated extracorporeal circuits reduce complement activation during cardiac operations, little in vivo information is available on the reduction in alternative and classic pathway activation.

METHODS

In a prospective, randomized study involving patients undergoing coronary artery bypass grafting with standard full heparinization, we compared heparin-coated circuits (Duraflo II) (10 patients) with uncoated circuits (10 patients) and assessed the extent of initiation of complement activation by detecting iC3 (C3b-like C3) concentrations, classic pathway activation by C4b/c (C4b, iC4b, C4c) concentrations, terminal pathway activation by soluble C5b-9 concentrations, and C3 activation by C3a (C3a desArg) and C3b/c (C3b, iC3b, C3c) concentrations.

RESULTS

Heparin-coated extracorporeal circuits significantly reduced circulating complement activation product C3b/c and soluble C5b-9 concentrations at the end of cardiopulmonary bypass and after protamine sulfate administration compared with the uncoated circuits, but not iC3, C4b/c, or C3a concentrations.

CONCLUSIONS

Heparin-coated extracorporeal circuits reduce complement activation through the alternative complement pathway, probably at the C3 convertase level, and, consequently, the terminal pathway. C3b/c seems to be a more sensitive marker than C3a to assess complement activation during cardiac operations.