Systemic inflammatory responses to surgery with cardiopulmonary bypass

Impact of Different Cardiopulmonary Bypass Strategies on Renal Injury After Pediatric Heart Surgery

BACKGROUND

The purpose of this study is to compare the incidence and severity of acute kidney injury (AKI) after open heart surgery in neonates and infants for two different cardiopulmonary bypass (CPB) strategies.

METHODS

In all, 151 infants undergoing cardiac surgery were prospectively enrolled between June 2017 and June 2018 at two centers, one using conventional CPB (2.4 L · min^-1 · m^-2, 150 mL · kg^-1 · min^-1) with reduction of flow rates with moderate hypothermia and with a targeted hematocrit greater than 25% (center 1, n = 91), and the other using higher bypass flow rates (175 to 200 mL · kg^-1 · min^-1) and higher minimum hematocrit (greater than 32%) CPB (center 2, n = 60). The primary endpoint was the incidence of postoperative AKI as defined by Acute Kidney Injury Network criteria and risk factors associated with AKI.

RESULTS

Preoperative characteristics and complexity of surgery were comparable between centers. The overall incidence of early postoperative AKI was 10.6% (16 of 151), with 15.4% (14 of 91) in center 1 and 3.3% (2 of 60) in center 2 (P = .02). Mean lowest flow rates on CPB were 78 mL · kg^-1 · min^-1 vs 118 mL · kg^-1 · min^-1 and mean highest hematocrit on separation from CPB were 33% vs 43% at center 1 and 2, respectively (P < .001). Center 1 used less packed red blood cells but more fresh frozen plasma than center 2 (P = .001). By multivariate analysis, only lower flows on CPB (78 vs 96 mL · kg^-1 · min^-1, P = .043) and lower hematocrit at the end of CPB (33% vs 37%, P = .007) were associated with AKI.

CONCLUSIONS

In this contemporary comparative study, higher flow rates and higher hematocrit during cardiopulmonary bypass were associated with better preservation of renal function.

Failure to Launch: Targeting Inflammation in Acute Coronary Syndromes

The importance of inflammation and inflammatory pathways in atherosclerotic disease and acute coronary syndromes (ACS) is well established. The success of statin therapy rests not only on potently reducing levels of low-density lipoprotein cholesterol, but also on the many beneficial, pleiotropic effects statin therapy has on various inflammatory mechanisms in atherosclerotic disease, from reducing endothelial dysfunction to attenuating levels of serum C-reactive protein. Due to the growing awareness of the importance of inflammation in ACS, investigators have attempted to develop novel therapies against known markers of inflammation for several decades. Targeted pathways have ranged from inhibiting C5 cleavage with a high-affinity monoclonal antibody against C5 to inhibiting the activation of the p38 mitogen-activated protein kinase signaling cascades. In each of these instances, despite promising early preclinical and mechanistic studies and phase 2 trials suggesting a potential benefit in reducing post-MI complications or restenosis, these novel therapies have failed to show benefits during large, phase 3 clinical outcomes trials. This review discusses several examples of novel anti-inflammatory therapies that failed to show significant improvement on clinical outcomes when tested in large, randomized trials and highlights potential explanations for why targeted therapies against known markers of inflammation in ACS have failed to launch.

Comparison of Two Miniaturized Cardiopulmonary Bypass Systems Regarding Inflammatory Response

Cardiopulmonary bypass (CPB) is a known mediator of systemic inflammatory response. Extracorporeal circulations are undergoing continuous modifications and optimizations to achieve better results. Hence we aim to compare the inflammatory response associated with two recent miniature extracorporeal circulation systems during normothermic CPB. We measured plasma levels of cytokines including interleukin (IL)-1β, IL-6, IL-10, tumor necrosis factor-α, migration inhibitory factor (MIF), receptor for advanced glycation endproduct, and cluster of differentiation 40 ligand in 60 consecutive patients during the first 24 h after CPB. The patients were prospectively randomized to one of three trial groups: patients in group A were operated with the minimal extracorporeal circulation circuit (MECC, Maquet, Rastatt, Germany), group B operated with the extracorporeal circulation circuit optimized (ECC.O, Sorin, Italy), and group C operated with a conventional extracorporeal circuit (CECC, Maquet). Arterial blood samples were collected at intervals before, 30 min after initiation, and after termination of CPB. Further samples were collected 6 and 24 h after CPB. IL-10 levels were significantly raised in the CECC group as compared with either of the mini ECC-circuits with a peak concentration at 6 h postoperatively. Human MIF concentrations were significantly higher in the CECC group starting 30 min after CPB and peaking at the end of CPB. The overall reduction in cytokine concentrations in the mini-ECC groups correlated with a lower need for blood transfusion in MECC and a shorter mechanical ventilation time for ECC.O. Normothermic CPB using minimally invasive extracorporeal circulation circuits can reduce the inflammatory response as measured by cytokine levels, which may be beneficial for perioperative preservation of pulmonary function and hemostasis in low risk patients.

Postoperative Atrial Fibrillation following Open Cardiac Surgery: Predisposing Factors and Complications

INTRODUCTION

New-onset postoperative atrial fibrillation (POAF) is a common complication of cardiac surgery that has substantial effects on outcomes. The aim of this study is to analyze the risk factors in the pre, intra, and postoperative periods, and evaluate its impact on patients' outcome.

METHODS

In this prospective study, between March 2007 and February 2011, a total of 1254 patients with preoperative sinus rhythm who underwent open cardiac surgery were included of which 177 (13.6%) had developed POAF. Many clinical variables that are associated with the development of POAF, were evaluated.

RESULTS

The study population consisted of 1254 patients that 864 (68.9%) were male and 390 (31.1%) female, and average age was 55.1±15.7 years. POAF occurred in 171 (13.6%) of patients and most of them (68.4%) developed within the first two days after surgery. Multivariate logistic regression analysis was used to identify the following risk factors of POAF: Preoperative risk factors: age>50, smoking, Left ventricular hypertrophy, renal dysfunction, intraoperative risk factors: intraoperative inotrope use, valve surgery, atrial septal defect (ASD) surgery, bicaval cannulation, concomitant cardiac venting of pulmonary and aorta, longer cardiopulmonary time, longer cross-clamp time, postoperative use of inotropic agent after termination of cardiopulmonary bypass.

CONCLUSION

POAF is the most common arrhythmia after cardiac surgery and not only concerted effort should be performed to identify and to reduce the risk factors, but also effective treatment is necessary to prevent mortality and morbidity.

Complement activation and cardiac surgery: a novel target for improving outcomes

Complement activation and the resulting inflammatory response is an important potential mechanism for multisystem organ injury in cardiac surgery. Novel therapeutic strategies using complement inhibitors may hold promise for improving outcomes for cardiac surgical patients by attenuating complement activation or its biologically active effector molecules. Recent clinical trials evaluating complement inhibitors have provided important data to further delineate the impact of complement activation and its inhibition on clinical outcomes. In this review we examine the role of complement activation and its inhibition as a therapeutic approach in cardiac surgery.

Determinants of postoperative atrial fibrillation and associated resource utilization in cardiac surgery

INTRODUCTION AND OBJECTIVES

Atrial arrhythmias occur after cardiac surgery in 10-65% of patients. The most common postoperative arrhythmia is atrial fibrillation (AF).

METHODS

The Tehran Heart Center Cardiovascular Research database (of 15 580 patients) was used to identify all patients who developed any form of AF as a postoperative complication following their first cardiac surgery (e.g. for coronary artery bypass grafting [CABG], valve surgery or both), with and without cardiopulmonary bypass, between June 2002 and March 2008.

RESULTS

Of the 15 580 patients who underwent a first cardiac surgery, 11 435 (73.4%) were male and their mean age was 58.16+/-10.11 years. New-onset AF developed postoperatively in 1129 (7.2%). New-onset AF occurred most frequently in patients who were aged > or =60 years and who had no history of beta-blocker use. In addition, patients were more likely to develop new-onset AF if they had valve surgery alone (16.5%) or CABG plus valve surgery combined (9.6%), needed intra-aortic balloon counterpulsation (IABC), or had a long cardiopulmonary bypass time. Multivariate analysis identified the following predictors of postoperative AF: older age, history of renal failure, congestive heart disease, operation type, longer perfusion time, and use of IABC. The incidence of early readmission (4.4%) was significantly higher in patients with postoperative AF, as was the duration of hospitalization, both overall and postoperatively. The short-term postoperative mortality rate was 3.8%.

CONCLUSIONS

Atrial fibrillation frequently develops after cardiac surgery and is associated not only with increased morbidity and mortality, but also with increased use of health-care resources.

Impact of residency status on perfusion times and outcomes for coronary artery bypass graft surgery

BACKGROUND

A price of training residents in cardiothoracic surgery is often perceived to be a loss in intraoperative efficiencies, leading to prolonged cardiopulmonary bypass and perfusion time. Because these indicators are also thought to adversely affect operative outcome, we investigated the association between residency training status, perfusion times, and outcomes.

METHODS

Using the Society of Thoracic Surgeons (STS) National Cardiac Database, we studied 369,906 CABG patients undergoing isolated coronary artery bypass graft (CABG) procedures during January 2002 through June 2005. Participating institutions were stratified by residency versus nonresidency status and by perfusion time categories and analyzed for association with clinical outcomes.

RESULTS

Overall, 57 (10%) of 594 STS participants had a residency training program. Residency programs had longer mean cross-clamp and perfusion times than nonresidency programs, 73.10 versus 67.44 minutes and 104.75 versus 98.00 minutes, respectively (p < 0.0001 for both. Longer perfusion time was significantly associated with higher operative mortality at the patient level. Unadjusted mortality rates were, however, similar for patients at residency and nonresidency programs (2.30% versus 2.27%), with an adjusted odds ratio of 0.96 (95% confidence interval, 0.84 to 1.09). Although perfusion times have not changed significantly over time between residency and nonresidency programs, mortality rates have significantly improved over time at each.

CONCLUSIONS

Residency programs have longer CABG perfusion times than nonresidency cardiothoracic surgery programs, but these differences are minor. Adjusted procedural outcomes at residency training programs are similar to those at nonresidency centers; thus, patients do not appear to be adversely impacted by the time costs of surgical training.

Effect of pexelizumab in coronary artery bypass graft surgery with extended aortic cross-clamp time

BACKGROUND

Prolonged cross-clamp time during cardiac surgery increases the risk of postoperative mortality and myocardial injury. This subanalysis from the pexelizumab for reduction of infarction and mortality in coronary artery bypass grafting surgery (PRIMO-CABG) trial, a phase III double-blind, placebo-controlled study of 3,099 patients undergoing on-pump coronary artery bypass graft surgery with or without valve surgery, assessed the impact of pexelizumab, an investigational C5 complement inhibitor, on postoperative outcomes after prolonged aortic cross-clamp time.

METHODS

The composite endpoint of death or myocardial infarction through postoperative day 30 and death alone through days 30, 90, and 180 were examined in subpopulations of patients across different cross-clamp times.

RESULTS

After prolonged cross-clamping (> or = 90 minutes), death, or myocardial infarction through day 30 and death through days 30, 90, and 180 were significantly increased in the intent-to-treat population and were even higher in patients with two or more prespecified risk factors, compared with all patients cross-clamped less than 90 minutes. Pexelizumab significantly reduced the incidence of death or myocardial infarction through day 30, and significantly reduced the incidence of mortality through day 180, in patients with two or more risk factors that required prolonged cross-clamp time. Pexelizumab also significantly reduced perioperative myocardial injury in all patients requiring prolonged cross-clamp time.

CONCLUSIONS

In this retrospective, subgroup analysis, pexelizumab reduced postoperative morbidity and myocardial injury in patients with multiple risk factors who underwent prolonged cross-clamp time during coronary artery bypass surgery. The clinical benefit of pexelizumab may be related to the effect of complement inhibition in the presence of potential ischemic-reperfusion injury associated with prolonged aortic cross-clamp time.

Pexelizumab reduces death and myocardial infarction in higher risk cardiac surgical patients

BACKGROUND

Morbidity and mortality after coronary artery bypass graft surgery are directly related to specific preoperative risk factors. We assessed the influence of preoperative risk factors on the effect of pexelizumab, a C5 complement inhibitor, to reduce postoperative morbidity and mortality in this post hoc analysis of the Pexelizumab for Reduction in Myocardial Infarction and MOrtality in Coronary Artery Bypass Graft surgery (PRIMO-CABG) trial, a phase III double-blind, placebo-controlled study of 3,099 patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass.

METHODS

The composite endpoint of death or myocardial infarction or both through postoperative day 30 was examined in subpopulations of patients with pre-specified risk factors, which included diabetes mellitus, prior coronary artery bypass graft, urgent intervention, female sex, history of neurologic event, history of congestive heart failure, and two or more previous myocardial infarctions or a recent myocardial infarction. Stratified post hoc analyses were also performed on patients presenting with two or more and three or more of those risk factors.

RESULTS

Pexelizumab significantly reduced the incidence of the composite endpoint of death or myocardial infarction through postoperative day 30 by 28% in patients with two or more risk factors (p = 0.004) and 44% in patients with three or more risk factors (p < 0.001).

CONCLUSIONS

The C5 complement inhibitor, pexelizumab, reduced morbidity and mortality among high-risk patients undergoing coronary artery bypass grafting with cardiopulmonary bypass.

Modulation of systemic inflammatory response after cardiac surgery

Cardiac surgery and cardiopulmonary bypass initiate a systemic inflammatory response largely determined by blood contact with foreign surfaces and the activation of complement. It is generally accepted that cardiopulmonary bypass initiates a whole-body inflammatory reaction. The magnitude of this inflammatory reaction varies, but the persistence of any degree of inflammation may be considered potentially harmful to the cardiac patient. The development of strategies to control the inflammatory response following cardiac surgery is currently the focus of considerable research efforts. Diverse techniques including maintenance of hemodynamic stability, minimization of exposure to cardiopulmonary bypass circuitry, and pharmacologic and immunomodulatory agents have been examined in clinical studies. This article briefly reviews the current concepts of the systemic inflammatory response following cardiac surgery, and the various therapeutic strategies being used to modulate this response.

Preliminary Report of the Effects of Complement Suppression With Pexelizumab on Neurocognitive Decline After Coronary Artery Bypass Graft Surgery

Background and Purpose— Pharmacological modulation of complement activation recently has been postulated as a therapeutic target in the treatment of neurological injury. We hypothesized that pexelizumab, a humanized scFv monoclonal antibody directed against the C5 complement component, would limit deficits in patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass.

Methods— The Phase II Pexelizumab study was a 914-patient, double-blind, placebo-controlled, 65-center study of patients undergoing coronary artery bypass graft surgery. Patients were randomized to pexelizumab bolus, bolus plus infusion, or placebo. Neurological and neurocognitive functions were assessed as secondary endpoints at baseline and on postoperative days (POD) 4 and 30. Cognitive deficits were assessed with multivariable tests accounting for baseline cognition, age, diabetes, years of education, sex, elevated creatinine, history of myocardial infarction, neurological disorder or congestive heart failure, and cardiopulmonary bypass time.

Results— Pexelizumab had no statistically significant effect on the primary composite endpoint or on overall cognition. When domain specific effects were examined, a decline of at least 10% in the visuo-spatial domain was observed on POD 4 in 56% of patients receiving placebo compared with 40% receiving pexelizumab by bolus and infusion ( P =0.003). Similarly, on POD 30, a 10% decline was present in 21% of patients in the placebo group versus only 12% of the drug bolus plus infusion group ( P =0.016). No differences were seen between treatment groups in any of the other domains.

Conclusions— Pexelizumab administration for 24 hours perioperatively had no effect on global measures of cognition but may reduce dysfunction in the visuo-spatial domain.

Impact of pexelizumab, an anti-C5 complement antibody, on total mortality and adverse cardiovascular outcomes in cardiac surgical patients undergoing cardiopulmonary bypass

BACKGROUND

During cardiac surgery requiring cardiopulmonary bypass, pro-inflammatory complement pathways are activated by exposure of blood to bio-incompatible surfaces of the extracorporeal circuit and reperfusion of ischemic organs. Complement activation promotes the generation of additional inflammatory mediators thereby exacerbating tissue injury. We examined the safety and efficacy of a C5 complement inhibitor for attenuating inflammation-mediated cardiovascular dysfunction in cardiac surgical patients undergoing cardiopulmonary bypass.

METHODS

Pexelizumab (Alexion Pharmaceuticals, Inc, Cheshire, CT), a recombinant, single-chain, anti-C5 monoclonal antibody, was evaluated in a randomized, double-blinded, placebo-controlled, multicenter trial that involved 914 patients undergoing coronary artery bypass grafting with or without valve surgery requiring cardiopulmonary bypass.

RESULTS

Pexelizumab was administered intravenously as a bolus (2.0 mg/kg) or bolus plus infusion (2.0 mg/kg plus 0.05 mg/kg/h for 24 hours), and inhibited complement activation. There were no statistically significant differences between placebo-treated and pexelizumab-treated patients in the primary endpoint (composite of death, or new Q-wave, or non-Q-wave [myocardial-specific isoform of creatine kinase > 60 ng/mL] myocardial infarction, or left ventricular dysfunction, or new central nervous system deficit). However, post hoc analysis revealed a reduction in the composite of death or myocardial infarction (myocardial-specific isoform of creatine kinase >/= 100 ng/mL) for the isolated coronary artery bypass grafting, bolus plus infusion subgroup on POD 4 (p = 0.007) and on POD 30 (p = 0.004).

CONCLUSIONS

Pexelizumab had no statistically significant effect on the primary endpoint. However, the reduction in death or myocardial infarction (myocardial-specific isoform of creatine kinase >/= 100 ng/mL) as revealed in the post hoc analysis in the isolated coronary artery bypass grafting bolus plus infusion subpopulation, suggests that further investigation of anti-C5 therapy for ameliorating complement-mediated inflammation and myocardial injury is warranted.

Perioperative myocardial ischemia reperfusion injury

Myocardial I-R injury contributes to adverse cardiovascular outcomes after cardiac surgery. The pathogenesis of I-R injury is complex and involves the activation, coordination, and amplification of several systemic and local proinflammatory pathways (Fig. 4). Treatment and prevention of perioperative morbidity associated with myocardial I-R will ultimately require a multifocal approach. Combining preoperative risk stratification (co-morbidity and surgical complexity), minimizing initiating factors predisposing to SIRS, limiting ischemia duration, and administering appropriate immunotherapy directed toward systemic and local proinflammatory mediators of I-R injury, should all be considered. In addition, the role of the genetic-environmental interactions in the pathogenesis of cardiovascular disease is also being examined. Thus, in the near future, preoperative screening for polymorphisms of certain inflammatory and coagulation genes should inevitably help reduce morbidity by permitting the identification of high-risk cardiac surgical patients and introducing the opportunity for gene therapy or pharmacogenetic intervention [42,64].

The systemic inflammatory response to cardiopulmonary bypass

Although our understanding of the basic pathophysiology of systemic inflammatory response to CPB has significantly advanced in the last 2 decades, these experimentally derived ideas have yet to be fully integrated into clinical practice. Treatment of the systemic inflammatory response to CPB is also confounded by the fact that inhibition of inflammation might disrupt protective physiologic responses or result in immunosuppression. Although it is unlikely that no single therapeutic strategy will ever be sufficient in of itself to totally prevent CPB-associated morbidity, the combination of multiple pharmacologic and mechanical therapeutic strategies, each selectively targeted at different components of the inflammatory response, may eventually result in significantly improved clinical outcomes following cardiac surgery.

The effect of zero-balanced ultrafiltration during cardiopulmonary bypass on S100b release and cognitive function

Zero-balanced ultrafiltration (ZBUF) might reduce the systemic inflammatory response (SIRS) during cardiopulmonary bypass (CPB) by removing inflammatory mediators. The objective of this study was to determine the effect of ZBUF on postoperative serum S100b levels, a marker of neuronal injury. In addition, the possible effects of ZBUF on postoperative neurocognitive function were assessed. Sixty patients undergoing elective coronary bypass grafting were randomly assigned either to a control group or to a protocol group in which ZBUF was performed. Serum S100b levels were measured five minutes after intubation, at the end of bypass and eight and 20 hours after arrival at the intensive care unit (ICU). Cognitive function was assessed with neuropsychological tests on the day before the operation and the sixth day after surgery. The S100b level at 20 hours after arrival at the ICU was 0.27 g/L (SD 0.16) in the control and 0.25 g/L (SD 0.12) in the group with ZBUF. There were no statistical differences at any time between the two groups. S100b was not detectable in the ultrafiltrate, indicating that these results were not obscured by washout of S100b. Thirteen patients (52%) in the control group and 14 patients (56%) in the ZBUF group showed a cognitive deficit. In conclusion, ZBUF during CPB does not decrease the release of S100b. This result is not affected by washout. ZBUF did not reduce the incidence of early neurocognitive deficits. The role of SIRS in the development of cognitive dysfunction following CPB remains to be resolved.

Postcardiac surgery complications: association of acute renal dysfunction and atrial fibrillation

Postoperative creatinine increase is associated with adverse outcome after cardiac surgery. Although postoperative stroke and renal dysfunction are associated after cardiac surgery, suggesting a common systemic insult, a similar assessment of atrial fibrillation and renal dysfunction has not been performed. Therefore, we tested the hypothesis that patients with new-onset atrial fibrillation complicating coronary bypass surgery have a greater postoperative creatinine increase. Data were obtained for 453 elective coronary bypass surgery patients with no history of atrial fibrillation. Multivariate regression analyses of factors associated with peak fractional change in creatinine demonstrated a two-way interaction between age and atrial fibrillation (variable estimate, -1.1; P = 0.002). Similar results were obtained in a secondary multivariate model analyzing factors associated with peak postoperative creatinine (variable estimate, -0.01; P = 0.04). We confirmed our hypothesis that patients with new-onset atrial fibrillation are more likely to have acute renal dysfunction after cardiac surgery. The association of atrial fibrillation and creatinine increase diminishes with advancing age. These data are consistent with a common pathophysiology that contributes in an age-dependent fashion to the etiology of both acute renal dysfunction and atrial fibrillation after coronary bypass surgery.

IMPLICATIONS

We found an independent association between new-onset atrial fibrillation and postoperative creatinine increase that is influenced by age. The degree to which atrial fibrillation is associated with postoperative creatinine increase diminishes with advancing age. This interaction suggests that a common etiology for these two complications may be more important in younger patients.

Does aprotinin influence the inflammatory response to cardiopulmonary bypass in patients?

OBJECTIVES

Aprotinin has been shown to have anti-inflammatory properties, but its effects on the inflammatory reaction to cardiopulmonary bypass remain controversial. This prospective, randomized, double-blind study evaluated the influence of aprotinin on various blood markers of inflammation during and after cardiopulmonary bypass.

METHODS

Sixty male patients underwent coronary artery bypass grafting. The patients were randomized into 3 groups: a placebo group, a second group receiving 2,000,000 KIU of aprotinin followed by an infusion of 500,000 KIU/h and 2,000,000 KIU in the pump prime, and a third group receiving half this dosage. Measurements of tumor necrosis factor, interleukin 6, interleukin 8, interleukin 10, endotoxin, histamine, complement factors, prekallikrein, and prostaglandin D(2) were obtained at baseline, 30 minutes after study drug loading, 10 minutes after the beginning of cardiopulmonary bypass, before the end of bypass, 4 hours after bypass, and on the first and second postoperative days.

RESULTS

Aprotinin had no significant effect on any of these parameters. As expected, aprotinin reduced early blood loss in both treated groups.

CONCLUSIONS

These results indicate that aprotinin at doses currently used to reduce blood loss has no significant influence on the systemic inflammatory response during moderate hypothermic cardiopulmonary bypass in human subjects, as assessed by the mediators measured in this study.

Aprotinin and the systemic inflammatory response after cardiopulmonary bypass

Cardiopulmonary bypass is associated with a systemic inflammatory response, a spectrum of pathophysiologic changes ranging from mild organ dysfunction to multisystem organ failure. Complications include coagulation disorders (bleeding diathesis, hyperfibrinolysis) from platelet defects and plasmin activation, as well as pulmonary dysfunction from neutrophil sequestration and degranulation. Diverse injuries are a consequence of multiple inflammatory mediators (complement, kinins, kallikrein, cytokines). Both plasmin and kallikrein amplify the inflammatory response by activating components of the contact activation system. The full-Hammersmith (high dose) of aprotinin, a serine protease inhibitor approved for reducing blood loss and transfusion requirements in cardiopulmonary bypass, inhibits kallikrein and plasmin, resulting in suppression of multiple systems involved in the inflammatory response. Specifically, inhibition of factor XII, bradykinin, C5a, neutrophil integrin expression, elastase activity, and airway nitric oxide production are observed. Clinical correlates include reduced capillary leak, preserved systemic vascular resistance and blood pressure, and improved myocardial recovery following ischemia. Overall, evidence indicates that aprotinin attenuates the systemic inflammatory response associated with cardiopulmonary bypass.

Pharmacology and biological efficacy of a recombinant, humanized, single-chain antibody C5 complement inhibitor in patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) induces a systemic inflammatory response that causes substantial clinical morbidity. Activation of complement during CPB contributes significantly to this inflammatory process. We examined the capability of a novel therapeutic complement inhibitor to prevent pathological complement activation and tissue injury in patients undergoing CPB.

METHODS AND RESULTS

A humanized, recombinant, single-chain antibody specific for human C5, h5G1.1-scFv, was intravenously administered in 1 of 4 doses ranging from 0.2 to 2.0 mg/kg before CPB. h5G1.1-scFv was found to be safe and well tolerated. Pharmacokinetic analysis revealed a sustained half-life from 7.0 to 14.5 hours. Pharmacodynamic analysis demonstrated significant dose-dependent inhibition of complement hemolytic activity for up to 14 hours at 2 mg/kg. The generation of proinflammatory complement byproducts (sC5b-9) was effectively inhibited in a dose-dependent fashion. Leukocyte activation, as measured by surface expression of CD11b, was reduced (P<0.05) in patients who received 1 and 2 mg/kg. There was a 40% reduction in myocardial injury (creatine kinase-MB release, P=0.05) in patients who received 2 mg/kg. Sequential Mini-Mental State Examinations (MMSE) demonstrated an 80% reduction in new cognitive deficits (P<0.05) in patients treated with 2 mg/kg. Finally, there was a 1-U reduction in postoperative blood loss (P<0. 05) in patients who received 1 or 2 mg/kg.

CONCLUSIONS

A single-chain antibody specific for human C5 is a safe and effective inhibitor of pathological complement activation in patients undergoing CPB. In addition to significantly reducing sC5b-9 formation and leukocyte CD11b expression, C5 inhibition significantly attenuates postoperative myocardial injury, cognitive deficits, and blood loss. These data suggest that C5 inhibition may represent a novel therapeutic strategy for preventing complement-mediated inflammation and tissue injury.