Leukocyte integrin expression in patients undergoing cardiopulmonary bypass

Effects of interventions targeting the systemic inflammatory response to cardiac surgery on clinical outcomes in adults

BACKGROUND

Organ injury is a common and severe complication of cardiac surgery that contributes to the majority of deaths. There are no effective treatment or prevention strategies. It has been suggested that innate immune system activation may have a causal role in organ injury. A wide range of organ protection interventions targeting the innate immune response have been evaluated in randomised controlled trials (RCTs) in adult cardiac surgery patients, with inconsistent results in terms of effectiveness.

OBJECTIVES

The aim of the review was to summarise the results of RCTs of organ protection interventions targeting the innate immune response in adult cardiac surgery. The review considered whether the interventions had a treatment effect on inflammation, important clinical outcomes, or both.

SEARCH METHODS

CENTRAL, MEDLINE, Embase, conference proceedings and two trial registers were searched on October 2022 together with reference checking to identify additional studies.

SELECTION CRITERIA

RCTs comparing organ protection interventions targeting the innate immune response versus placebo or no treatment in adult patients undergoing cardiac surgery where the treatment effect on innate immune activation and on clinical outcomes of interest were reported.

DATA COLLECTION AND ANALYSIS

Searches, study selection, quality assessment, and data extractions were performed independently by pairs of authors. The primary inflammation outcomes were peak IL-6 and IL-8 concentrations in blood post-surgery. The primary clinical outcome was in-hospital or 30-day mortality. Treatment effects were expressed as risk ratios (RR) and standardised mean difference (SMD) with 95% confidence intervals (CI). Meta-analyses were performed using random effects models, and heterogeneity was assessed using I2.

MAIN RESULTS

A total of 40,255 participants from 328 RCTs were included in the synthesis. The effects of treatments on IL-6 (SMD -0.77, 95% CI -0.97 to -0.58, I2 = 92%) and IL-8 (SMD -0.92, 95% CI -1.20 to -0.65, I2 = 91%) were unclear due to heterogeneity. Heterogeneity for inflammation outcomes persisted across multiple sensitivity and moderator analyses. The pooled treatment effect for in-hospital or 30-day mortality was RR 0.78, 95% CI 0.68 to 0.91, I2 = 0%, suggesting a significant clinical benefit. There was little or no treatment effect on mortality when analyses were restricted to studies at low risk of bias. Post hoc analyses failed to demonstrate consistent treatment effects on inflammation and clinical outcomes. Levels of certainty for pooled treatment effects on the primary outcomes were very low.

AUTHORS' CONCLUSIONS

A systematic review of RCTs of organ protection interventions targeting innate immune system activation did not resolve uncertainty as to the effectiveness of these treatments, or the role of innate immunity in organ injury following cardiac surgery.

Lung injury following cardiopulmonary bypass: a clinical update

INTRODUCTION

Cardiopulmonary bypass (CPB) is an integral component of cardiac surgery; however, one of its most critical complications is acute lung injury induced by multiple factors including systemic inflammatory response.

AREAS COVERED

The objective of this review is to investigate the multiple factors that can lead to CPB-induced lung injury. These include contact of blood components with the artificial surface of the CPB circuit, local and systemic inflammatory response syndrome (SIRS), lung ischemia/re-perfusion injury, arrest of ventilation, and circulating endotoxins. We also focus on possible interventions to curtail the negative impact of CPB, such as off-pump surgery, impregnation of the circuit with less biologically active substances, leukocyte depletion filters and ultrafiltration, and pharmacological agents such as steroids and aprotinin.

EXPERT OPINION

Although many aspects of CPB are proposed to contribute to lung injury, its overall role is still not clear. Multiple interventions have been introduced to reduce the risk of pulmonary dysfunction, with many of these interventions having shown promising results, significantly attenuating inflammatory mediators and improving post-operative outcome. However, since lung injury is multifactorial and affected by inextricably linked components, multiple interventions tackling each of them is required.

VLA-1 Binding to Collagen IV Controls Effector T Cell Suppression by Myeloid-Derived Suppressor Cells in the Splenic Red Pulp

Myeloid-derived suppressor cells (MDSCs) represent a major population controlling T cell immune responses. However, little is known about their molecular requirements for homing and T cell interaction to mediate suppression. Here, we investigated the functional role of the homing and collagen IV receptor VLA-1 (α1β1-integrin) on in vitro GM-CSF generated murine MDSCs from wild-type (WT) and CD49a/α1-integrin (Itga1^−/−) gene-deficient mice. Here, we found that effector (Teff) but not naive (Tn) CD4⁺ T cells express VLA-1 and monocytes further up-regulated their expression after culture in GM-CSF when they differentiated into the monocytic subset of resting MDSCs (R-MDSCs). Subsequent activation of R-MDSCs by LPS+IFN-γ (A-MDSCs) showed increased in vitro suppressor potential, which was independent of VLA-1. Surprisingly, VLA-1 deficiency did not influence A-MDSC motility or migration on collagen IV in vitro. However, interaction times of Itga1^−/− A-MDSCs with Teff were shorter than with WT A-MDSCs on collagen IV but not on fibronectin substrate in vitro. After injection, A-MDSCs homed to the splenic red pulp where they co-localized with Teff and showed immediate suppression already after 6 h as shown by inhibition of T cell proliferation and induction of apoptosis. Injection of A-MDSCs from Itga1^−/− mice showed equivalent homing into the spleen but a reduced suppressive effect. Interaction studies of A-MDSCs with Teff in the subcapsular red pulp with intravital two-photon microscopy revealed also here that MDSC motility and migration parameters were not altered by VLA-1 deficiency, but the interaction times with Teff were reduced. Together, our data point to a new role of VLA-1 adhesion to collagen IV as a prerequisite for extended contact times with Teff required for suppression.

Current Understanding of Leukocyte Phenotypic and Functional Modulation During Extracorporeal Membrane Oxygenation: A Narrative Review

A plethora of leukocyte modulations have been reported in critically ill patients. Critical illnesses such as acute respiratory distress syndrome and cardiogenic shock, which potentially require extracorporeal membrane oxygenation (ECMO) support, are associated with changes in leukocyte numbers, phenotype, and functions. The changes observed in these illnesses could be compounded by exposure of blood to the non-endothelialized surfaces and non-physiological conditions of ECMO. This can result in further leukocyte activation, increased platelet-leukocyte interplay, pro-inflammatory and pro-coagulant state, alongside features of immunosuppression. However, the effects of ECMO on leukocytes, in particular their phenotypic and functional signatures, remain largely overlooked, including whether these changes have attributable mortality and morbidity. The aim of our narrative review is to highlight the importance of studying leukocyte signatures to better understand the development of complications associated with ECMO. Increased knowledge and appreciation of their probable role in ECMO-related adverse events may assist in guiding the design and establishment of targeted preventative actions.

Expression of an Activated Form of Integrin β2 Chain CD18 in Cardiac Surgical Operations

Background: Myeloid cells are extensively activated in patients undergoing cardiosurgical operations. It is supposed that this activation is more profound in patients operated with cardiopulmonary bypass (CPB) („on-pump“) in comparison with patients operated without CPB („off-pump“). Aims: To evaluate changes in the expression of a novel activation marker expressed on myeloid cells recognized by MEM-148 antibody. Patients and Methods: The expression of MEM-148 positive myeloid cells was evaluated by flow cytometry in 40 patients who underwent coronary artery bypass surgery (CABG) randomly assigned to „on-pump“ or „off-pump“ technique. Results: The relative and absolute number of MEM-148 positive myeloid cells is significantly diminished during „on-pump“ surgery. A significant increase in their number in postoperative period in both „on-pump“ and „off-pump“ patients was found. There were no significant differencies between „on-pump“ and „off-pump“ patients. Conclusions: The very trauma of surgery seems to be more relevant in starting on activation of myeloid cells them CPB itself.

Effects of propofol and isoflurane on haemodynamics and the inflammatory response in cardiopulmonary bypass surgery

Cardiopulmonary bypass (CPB) causes reperfusion injury that when most severe is clinically manifested as a systemic inflammatory response syndrome. The anaesthetic propofol may have anti-inflammatory properties that may reduce such a response. We hypothesised differing effects of propofol and isoflurane on inflammatory markers in patients having CBR Forty patients undergoing elective CPB were randomised to receive either propofol or isoflurane for maintenance of anaesthesia. CRP, IL-6, IL-8, HIF-1α (ELISA), CD11 and CD18 expression (flow cytometry), and haemoxygenase (HO-1) promoter polymorphisms (PCR/electrophoresis) were measured before anaesthetic induction, 4 hours post-CPB, and 24 hours later. There were no differences in the 4 hours changes in CRP, IL-6, IL-8 or CD18 between the two groups, but those in the propofol group had higher HIF-1α (P = 0.016) and lower CD11 expression (P = 0.026). After 24 hours, compared to the isoflurane group, the propofol group had significantly lower levels of CRP (P < 0.001), IL-6 (P < 0.001) and IL-8 (P < 0.001), with higher levels CD11 (P = 0.009) and CD18 (P = 0.002) expression. After 24 hours, patients on propofol had increased expression of shorter HO-1 GT(n) repeats than patients on isoflurane (P = 0.001). Use of propofol in CPB is associated with a less adverse inflammatory profile than is isofluorane, and an increased up-regulation of HO-1. This supports the hypothesis that propofol has anti-inflammatory activity.

Unchanged plasma levels of the soluble urokinase plasminogen activator receptor in elective coronary artery bypass graft surgery patients and cardiopulmonary bypass use

OBJECTIVE AND DESIGN

The soluble urokinase plasminogen activator receptor (suPAR) has been recently recognized as a potential biological marker of various disease states, but the impact of a major surgical intervention on the suPAR level has not yet been established. The aim of our study was to investigate if the induction of a systemic inflammatory reaction in response to cardiopulmonary bypass would be accompanied by an increase in the plasma suPAR level.

METHODS AND SUBJECTS

Patients undergoing coronary artery bypass grafting under cardiopulmonary bypass (CPB) were added. Based on the baseline suPAR level, patients were divided into group 1 (suPAR within normal range) or group 2 (suPAR above range). Blood was collected before the induction of anesthesia and 6 and 24 hours after surgery. Plasma suPAR, IL-6, IL-8, TNF-α, troponin I, NT-proBNP, and NGAL were quantified to assess the impact of surgical trauma on these markers.

RESULTS

The baseline suPAR level was within the normal range in 31 patients (3.3 ng/mL), and elevated in 29 (5.1 ng/mL) (p<0.001). Baseline mediators of systemic inflammatory reaction concentrations (IL-6, TNF-α, and IL-8) and organ injury indices (troponin I, NT-proBNP, and NGAL) were low and increased after surgery in all patients (p<0.05). The surgery did not cause significant changes in the suPAR level either at 6 or 24 hours after, however the difference between groups observed at baseline remained substantial during the postoperative period.

CONCLUSIONS

There was no change in the suPAR level observed in patients subjected to elective cardiac coronary artery bypass surgery and CPB, despite activation of a systemic inflammatory reaction.

Expression of CD11b (MAC-1) and CD162 (PSGL-1) on monocytes is decreased under conditions of deep hypothermic circulatory arrest

Deep hypothermic circulatory arrest (DHCA) is a common technique used to protect vital organs during surgical interventions on the thoracic aorta or during surgery for complex congenital heart disease. Activated leukocytes are key mediators of inflammatory responses during ischemia. Intercellular crosstalk between leukocytes, platelets and endothelial cells is mediated by cell adhesion molecules. These molecules trigger complex cell-cell interaction mechanisms and initiate the release of proinflammatory molecules. One parameter that is known to have a significant impact on inflammatory cell activation and the production of proinflammatory markers is temperature. However, to the best of our knowledge, no data have yet been published on the effect of hypothermia on leukocyte surface markers during DHCA. Thus, the aim of the present study was to investigate the effect of hypothermia on the expression of cell adhesion molecules on monocytes under DHCA conditions in vitro. Blood samples collected from 11 healthy volunteers were incubated in a well-established model simulating circulatory arrest at 36°C and 18°C for 30 min. The expression of cluster of differentiation (CD) molecule 11B (CD11b), CD54 and CD162 on monocytes was measured as the mean fluorescence intensity (MFI) using flow cytometry. The expression level of CD11b on monocytes was significantly decreased following the incubation of the blood samples at 18°C compared with the level in blood samples incubated at 36°C (P<0.001). After 30 min of blood stasis in the circulatory arrest model, the expression level of CD162 on monocytes was significantly lower in the blood samples incubated at 18°C than in those incubated at 36°C (P<0.001). No association was identified between temperature and the surface expression of CD54 on monocytes following 30 min of stasis. These findings demonstrate that deep hypothermia decreases the expression of CD11b and CD162 on monocytes in an experimental setup simulating the conditions of DHCA. This may be the result of the inhibition of leukocyte-endothelial and leukocyte-platelet interactions, which may be a beneficial aspect of deep hypothermia that affects the inflammatory response and tissue damage during DHCA.

Cardiopulmonary bypass during cardiac surgery modulates systemic inflammation by affecting different steps of the leukocyte recruitment cascade

Background

It is known that the use of a cardiopulmonary bypass (CPB) during cardiac surgery leads to leukocyte activation and may, among other causes, induce organ dysfunction due to increased leukocyte recruitment into different organs. Leukocyte extravasation occurs in a cascade-like fashion, including capturing, rolling, adhesion, and transmigration. However, the molecular mechanisms of increased leukocyte recruitment caused by CPB are not known. This clinical study was undertaken in order to investigate which steps of the leukocyte recruitment cascade are affected by the systemic inflammation during CPB.

Methods

We investigated the effects of CPB on the different steps of the leukocyte recruitment cascade in whole blood from healthy volunteers (n = 9) and patients undergoing cardiac surgery with the use of cardiopulmonary bypass (n = 7) or in off-pump coronary artery bypass-technique (OPCAB, n = 9) by using flow chamber experiments, transmigration assays, and biochemical analysis.

Results

CPB abrogated selectin-induced slow leukocyte rolling on E-selectin/ICAM-1 and P-selectin/ICAM-1. In contrast, chemokine-induced arrest and transmigration was significantly increased by CPB. Mechanistically, the abolishment of slow leukocyte rolling was due to disturbances in intracellular signaling with reduced phosphorylation of phospholipase C (PLC) γ2, Akt, and p38 MAP kinase. Furthermore, CPB induced an elevated transmigration which was caused by upregulation of Mac-1 on neutrophils.

Conclusion

These data suggest that CPB abrogates selectin-mediated slow leukocyte rolling by disturbing intracellular signaling, but that the clinically observed increased leukocyte recruitment caused by CPB is due to increased chemokine-induced arrest and transmigration. A better understanding of the underlying molecular mechanisms causing systemic inflammation after CPB may aid in the development of new therapeutic approaches.

Anti-fibrinolytic use for minimising perioperative allogeneic blood transfusion

BACKGROUND

Concerns regarding the safety of transfused blood have led to the development of a range of interventions to minimise blood loss during major surgery. Anti-fibrinolytic drugs are widely used, particularly in cardiac surgery, and previous reviews have found them to be effective in reducing blood loss, the need for transfusion, and the need for re-operation due to continued or recurrent bleeding. In the last few years questions have been raised regarding the comparative performance of the drugs. The safety of the most popular agent, aprotinin, has been challenged, and it was withdrawn from world markets in May 2008 because of concerns that it increased the risk of cardiovascular complications and death.

OBJECTIVES

To assess the comparative effects of the anti-fibrinolytic drugs aprotinin, tranexamic acid (TXA), and epsilon aminocaproic acid (EACA) on blood loss during surgery, the need for red blood cell (RBC) transfusion, and adverse events, particularly vascular occlusion, renal dysfunction, and death.

SEARCH STRATEGY

We searched: the Cochrane Injuries Group's Specialised Register (July 2010), Cochrane Central Register of Controlled Trials (The Cochrane Library 2010, Issue 3), MEDLINE (Ovid SP) 1950 to July 2010, EMBASE (Ovid SP) 1980 to July 2010. References in identified trials and review articles were checked and trial authors were contacted to identify any additional studies. The searches were last updated in July 2010.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of anti-fibrinolytic drugs in adults scheduled for non-urgent surgery. Eligible trials compared anti-fibrinolytic drugs with placebo (or no treatment), or with each other.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. This version of the review includes a sensitivity analysis excluding trials authored by Prof. Joachim Boldt.

MAIN RESULTS

This review summarises data from 252 RCTs that recruited over 25,000 participants. Data from the head-to-head trials suggest an advantage of aprotinin over the lysine analogues TXA and EACA in terms of reducing perioperative blood loss, but the differences were small. Compared to control, aprotinin reduced the probability of requiring RBC transfusion by a relative 34% (relative risk [RR] 0.66, 95% confidence interval [CI] 0.60 to 0.72). The RR for RBC transfusion with TXA was 0.61 (95% CI 0.53 to 0.70) and was 0.81 (95% CI 0.67 to 0.99) with EACA. When the pooled estimates from the head-to-head trials of the two lysine analogues were combined and compared to aprotinin alone, aprotinin appeared more effective in reducing the need for RBC transfusion (RR 0.90; 95% CI 0.81 to 0.99).Aprotinin reduced the need for re-operation due to bleeding by a relative 54% (RR 0.46, 95% CI 0.34 to 0.62). This translates into an absolute risk reduction of 2% and a number needed-to-treat (NNT) of 50 (95% CI 33 to 100). A similar trend was seen with EACA (RR 0.32, 95% CI 0.11 to 0.99) but not TXA (RR 0.80, 95% CI 0.55 to 1.17). The blood transfusion data were heterogeneous and funnel plots indicate that trials of aprotinin and the lysine analogues may be subject to publication bias.When compared with no treatment aprotinin did not increase the risk of myocardial infarction (RR 0.87, 95% CI 0.69 to 1.11), stroke (RR 0.82, 95% CI 0.44 to 1.52), renal dysfunction (RR 1.10, 95% CI 0.79 to 1.54) or overall mortality (RR 0.81, 95% CI 0.63 to 1.06). Similar trends were seen with the lysine analogues, but data were sparse. These data conflict with the results of recently published non-randomised studies, which found increased risk of cardiovascular complications and death with aprotinin. There are concerns about the adequacy of reporting of uncommon events in the small clinical trials included in this review.When aprotinin was compared directly with either, or both, of the two lysine analogues it resulted in a significant increase in the risk of death (RR 1.39, 95% CI 1.02, 1.89), and a non-significant increase in the risk of myocardial infarction (RR 1.11 95% CI 0.82, 1.50). Most of the data contributing to this added risk came from a single study - the BART trial (2008).

AUTHORS' CONCLUSIONS

Anti-fibrinolytic drugs provide worthwhile reductions in blood loss and the receipt of allogeneic red cell transfusion. Aprotinin appears to be slightly more effective than the lysine analogues in reducing blood loss and the receipt of blood transfusion. However, head to head comparisons show a lower risk of death with lysine analogues when compared with aprotinin. The lysine analogues are effective in reducing blood loss during and after surgery, and appear to be free of serious adverse effects.

Anti-fibrinolytic use for minimising perioperative allogeneic blood transfusion

BACKGROUND

Concerns regarding the safety of transfused blood have led to the development of a range of interventions to minimise blood loss during major surgery. Anti-fibrinolytic drugs are widely used, particularly in cardiac surgery, and previous reviews have found them to be effective in reducing blood loss, the need for transfusion, and the need for re-operation due to continued or recurrent bleeding. In the last few years questions have been raised regarding the comparative performance of the drugs. The safety of the most popular agent, aprotinin, has been challenged, and it was withdrawn from world markets in May 2008 because of concerns that it increased the risk of cardiovascular complications and death.

OBJECTIVES

To assess the comparative effects of the anti-fibrinolytic drugs aprotinin, tranexamic acid (TXA), and epsilon aminocaproic acid (EACA) on blood loss during surgery, the need for red blood cell (RBC) transfusion, and adverse events, particularly vascular occlusion, renal dysfunction, and death.

SEARCH STRATEGY

We searched: the Cochrane Injuries Group's Specialised Register (July 2010), Cochrane Central Register of Controlled Trials (The Cochrane Library 2010, Issue 3), MEDLINE (Ovid SP) 1950 to July 2010, EMBASE (Ovid SP) 1980 to July 2010. References in identified trials and review articles were checked and trial authors were contacted to identify any additional studies. The searches were last updated in July 2010.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of anti-fibrinolytic drugs in adults scheduled for non-urgent surgery. Eligible trials compared anti-fibrinolytic drugs with placebo (or no treatment), or with each other.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data.

MAIN RESULTS

This review summarises data from 252 RCTs that recruited over 25,000 participants. Data from the head-to-head trials suggest an advantage of aprotinin over the lysine analogues TXA and EACA in terms of reducing perioperative blood loss, but the differences were small. Compared to control, aprotinin reduced the probability of requiring RBC transfusion by a relative 34% (relative risk [RR] 0.66, 95% confidence interval [CI] 0.60 to 0.72). The RR for RBC transfusion with TXA was 0.61 (95% CI 0.53 to 0.70) and was 0.81 (95% CI 0.67 to 0.99) with EACA. When the pooled estimates from the head-to-head trials of the two lysine analogues were combined and compared to aprotinin alone, aprotinin appeared more effective in reducing the need for RBC transfusion (RR 0.90; 95% CI 0.81 to 0.99).Aprotinin reduced the need for re-operation due to bleeding by a relative 54% (RR 0.46, 95% CI 0.34 to 0.62). This translates into an absolute risk reduction of 2% and a number needed-to-treat (NNT) of 50 (95% CI 33 to 100). A similar trend was seen with EACA (RR 0.32, 95% CI 0.11 to 0.99) but not TXA (RR 0.80, 95% CI 0.55 to 1.17). The blood transfusion data were heterogeneous and funnel plots indicate that trials of aprotinin and the lysine analogues may be subject to publication bias.When compared with no treatment aprotinin did not increase the risk of myocardial infarction (RR 0.87, 95% CI 0.69 to 1.11), stroke (RR 0.82, 95% CI 0.44 to 1.52), renal dysfunction (RR 1.10, 95% CI 0.79 to 1.54) or overall mortality (RR 0.81, 95% CI 0.63 to 1.06). Similar trends were seen with the lysine analogues, but data were sparse. These data conflict with the results of recently published non-randomised studies, which found increased risk of cardiovascular complications and death with aprotinin. There are concerns about the adequacy of reporting of uncommon events in the small clinical trials included in this review.When aprotinin was compared directly with either, or both, of the two lysine analogues it resulted in a significant increase in the risk of death (RR 1.39, 95% CI 1.02, 1.89), and a non-significant increase in the risk of myocardial infarction (RR 1.11 95% CI 0.82, 1.50). Most of the data contributing to this added risk came from a single study - the BART trial (2008).

AUTHORS' CONCLUSIONS

Anti-fibrinolytic drugs provide worthwhile reductions in blood loss and the receipt of allogeneic red cell transfusion. Aprotinin appears to be slightly more effective than the lysine analogues in reducing blood loss and the receipt of blood transfusion. However, head to head comparisons show a lower risk of death with lysine analogues when compared with aprotinin. The lysine analogues are effective in reducing blood loss during and after surgery, and appear to be free of serious adverse effects.

Simple surface sulfonation retards plasticiser migration and impacts upon blood/material contact activation processes

BACKGROUND

The use of Di-2-ethylhexyl phthalate (DEHP) plasticised polyvinyl chloride (DEHPPPVC) in medical devices persists despite evidence suggesting that DEHP migration can be harmful. Researchers have shown that a simple surface sulfonation process can retard the migration of DEHP, which may reduce the associated inflammatory response. The present study is designed to investigate the effects of surface sulfonation on DEHP migration and blood contact activation using in vitro and rodent models.

METHODS

The study was carried out in two phases: phase 1, in which the migration rate of DEHP from DEHPPPVC and sulfonated DEHP plasticised PVC (SDEHPPPVC) was measured; phase 2 of the study, in which the materials were incorporated into a rat recirculation biomaterial test model and blood samples taken to assess CD11b expression on neutrophils, IL-6 and Factor XIIa.

RESULTS

The initial DEHP concentration washed from the surface after storage was 37.19 +/- 1.17 mg/l in the PPVC group and 5.89 +/- 0.81 mg/l in the SPPVC group (p<0.0001). The post-wash migration rate was 3.07 +/- 0.32 mg/l/hour in the PPVC group compared to 0.46 +/- 0.038 mg/l/hour in the SPPVC group (p<0.0001). In phase 2 of the study, CD11b expression increased by 228.9% +/- 37% over the test period in the PPVC group compared to 118.3% +/- 46% in the SPPVC group (p<0.01). IL-6 levels rose from 3.1 +/- 1.4 pg/ml to 263 +/- 26 pg/ml in the PPVC group and 2.2 +/- 1.6 pg/ml to 161 +/- 29 pg/ml in the SPPVC group (p<0.01). Factor XIIa levels rose from 0.22 +/- 0.13 g/ml to 3.7 +/- 0.32 microg/ml and 0.28 +/- 0.09 to 2.71 +/- 0.21 microg/ml in the PPVC and SPPVC groups, respectively (p<0.05 at 90 minutes).

CONCLUSIONS

The simple sulfonation process significantly retards the migration of DEHP and is associated with the moderation of contact activation processes.

The safety of aprotinin and lysine-derived antifibrinolytic drugs in cardiac surgery: a meta-analysis

BACKGROUND

Because of recent concerns about the safety of aprotinin, we updated our 2007 Cochrane review that compared the relative benefits and risks of aprotinin and the lysine analogues tranexamic acid and epsilon aminocaproic acid.

METHODS

We searched electronic databases, including CENTRAL, MEDLINE, EMBASE, Google and Google Scholar for trials of antifibrinolytic drugs used in adults scheduled for cardiac surgery. Searches were updated to January 2008. By comparing aprotinin and the 2 lysine analogues to control, we derived indirect head-to-head comparisons of aprotinin to the other drugs. We derived direct estimates of risks and benefits by pooling estimates from head-to-head trials of aprotinin and tranexamic acid or epsilon aminocaproic acid.

RESULTS

For indirect estimates, we identified 49 trials involving 182 deaths among 7439 participants. The summary relative risk (RR) for death with aprotinin versus placebo was 0.93 (95% confidence interval [CI] 0.69-1.25). In the 19 trials that included tranexamic acid, there were 24 deaths among 1802 participants. The summary RR was 0.55 (95% CI 0.24-1.25). From the risk estimates derived for individual drugs, we calculated an indirect summary RR of death with use of aprotinin versus tranexamic acid of 1.69 (95% CI 0.70-4.10). To calculate direct estimates of death for aprotinin versus tranexamic acid, we identified 13 trials with 107 deaths among 3537 participants. The summary RR was 1.43 (95% CI 0.98-2.08). Among the 1840 participants, the calculated estimates of death for aprotinin compared directly to epsilon aminocaproic acid was 1.49 (95% CI 0.98-2.28). We found no evidence of an increased risk of myocardial infarction with use of aprotinin compared with the lysine analogues in either direct or indirect analyses. Compared with placebo or no treatment, all 3 drugs were effective in reducing the need for red blood cell transfusion. The RR of transfusion with use of aprotinin was 0.66 (95% CI 0.61-0.72). The RR of transfusion was 0.70 (95% CI 0.61-0.80) for tranexamic acid, and it was 0.75 (95% CI 0.58-0.96) for use of epsilon aminocaproic acid. Aprotinin was also effective in reducing the need for re-operation because of bleeding (RR 0.48, 95% CI 0.34-0.67).

INTERPRETATION

The risk of death tended to be consistently higher with use of aprotinin than with use of lysine analogues. Aprotinin had no clear advantages to offset these harms. Either tranexamic acid or epsilon aminocaproic acid should be recommended to prevent bleeding after cardiac surgery.

The inflammatory effect of cardiopulmonary bypass on leukocyte extravasation in vivo

OBJECTIVE

Extravascular trafficking of leukocytes into organs is thought to play a major role in the pathophysiologic mechanisms of the inflammatory response to cardiopulmonary bypass, yet leukocyte extravasation is difficult to study clinically. Here we have tested the hypothesis that leukocyte emigration into skin blisters can provide a way to monitor the inflammatory effect of cardiopulmonary bypass that allows testing of anti-inflammatory interventions (exemplified by aprotinin).

METHODS

Patients undergoing primary elective coronary artery bypass grafting (n = 14) were randomized into 2 equal groups to receive saline infusion during cardiopulmonary bypass (control group) or high-dose aprotinin. Experimental skin blisters (in duplicate) were induced on the forearm by means of topical application of the vesicant cantharidin, and blister fluid was sampled at 5 hours postoperatively. Inflammatory leukocyte subsets in blister fluid were analyzed by means of flow cytometry by using expression of CD11b and CD62L as a phenotypic marker of activation.

RESULTS

In the control group of patients, cardiopulmonary bypass surgery triggered a 381% increase in leukocyte extravasation into the skin compared with reference blisters carried out before surgical intervention, with neutrophil (P = .014), monocyte (P = .014), and eosinophil (P = .009) levels all statistically significantly increased. In the aprotinin group there was no statistically significant increase during cardiopulmonary bypass surgery in any inflammatory leukocyte subset. The activation phenotype of extravascular leukocytes was not significantly altered between surgical groups.

CONCLUSIONS

This study introduces the cantharidin blister technique as a powerful new research tool for analyzing the inflammatory effect of cardiopulmonary bypass in vivo. It has provided detailed molecular insight into the extravascular leukocyte population during cardiopulmonary bypass. Although aprotinin blocked cardiopulmonary bypass-dependent extravasation of leukocytes, there was no change in their CD11b/CD62L activation status. The cantharidin skin test thus represents a novel research tool for evaluating future anti-inflammatory interventions in cardiothoracic surgery.

Meta-analysis comparing the effectiveness and adverse outcomes of antifibrinolytic agents in cardiac surgery

BACKGROUND

Since the 1980s, antifibrinolytic therapies have assisted surgical teams in reducing the amount of blood loss. To date, however, serious questions remain regarding the safety and effectiveness of these agents.

METHODS AND RESULTS

We conducted a meta-analysis to compare aprotinin, epsilon-aminocaproic acid, and tranexamic acid with placebo and head to head on 8 clinical outcomes from 138 trials. Published randomized controlled trial data were collected from OVID/PubMed. Outcomes included total blood loss, transfusion of packed red blood cells, reexploration, mortality, stroke, myocardial infarction, dialysis-dependent renal failure, and renal dysfunction (0.5-mg/dL increase in creatinine from baseline). All agents were effective in significantly reducing blood loss by 226 to 348 mL and the proportion of patients transfused with packed red blood cells over placebo. Only high-dose aprotinin reduced the rate of reexploration (relative risk, 0.49; 95% CI, 0.33 to 0.73). There were no significant risks or benefits for any agent for mortality, stroke, myocardial infarction, or renal failure. However, high-dose aprotinin significantly increased the risk of renal dysfunction (relative risk, 1.47; 95% CI, 1.12 to 1.94), 12.9% versus 8.4%. Compared head to head, high-dose aprotinin demonstrated significant reduction in total blood loss over epsilon-aminocaproic acid (-184 mL; 95% CI, -256 to -112) and tranexamic acid (-195 mL; 95% CI, -286 to -105). There were no significant differences among any agent when compared head to head on other outcomes.

CONCLUSIONS

All antifibrinolytic agents were effective in reducing blood loss and transfusion. There were no significant risks or benefits for mortality, stroke, myocardial infarction, or renal failure. However, high-dose aprotinin was associated with a statistically significant increased risk of renal dysfunction.

Cardioprotective effect of aprotinin on myocardial ischemia/reperfusion injury during cardiopulmonary bypass

BACKGROUND

Aprotinin is a serine protease inhibitor used extensively in cardiac operations to reduce postoperative bleeding. It also has cardioprotective effects in ischemia/reperfusion injury. In this study, the effects of aprotinin on the release of cardiac markers were evaluated in patients who had good ventricular function and were undergoing coronary artery bypass grafting with cardiopulmonary bypass (CPB).

METHODS AND RESULTS

Eighty male patients with an ejection fraction >or=40%, were randomized into either an aprotinin (Group-I; n=40) or control (Group-II; n=40) group. Patients in the aprotinin group received the full Hammersmith doses of aprotinin (2 x 10(6) KIU pre-CPB, 2 x 10(6) KIU at pump prime, 500,000 KIU/h during CPB), whereas the patients in the control group received only saline solutions. Cardiac troponin-I (cTnI) levels were measured before surgery, immediately after surgery, and at postoperative 6(th), 12(th), 24(th) h and 5(th) day. Creatine kinase (CK)-MB measurements were performed at the same time except for the postoperative 5(th) day. Cardiac index (CI), mixed venous oxygen saturation and lactate dehydrogenase (LDH) measurements were also performed.

CONCLUSION

Although all patients were in reasonable condition, less myocardial enzyme leakage occurred on the aprotinin group, suggesting that aprotinin has a protective effect on the myocardium beyond that achieved with blood cardioplegia and systemic hypothermia. Because of aprotinin's effects on multiple targets of metabolism, its protective value might increase in more complicated cases.

Aprotinin and the protease-activated receptor 1 thrombin receptor: antithrombosis, inflammation, and stroke reduction

Cardiopulmonary bypass, although remaining an indispensable asset in cardiac surgery, especially in more complex and repeat operations, is associated with significant thrombin generation in the bypass circuit, leading to the activation of platelets, the coagulation system, an inflammatory response, and perioperative stroke. Recent clinical studies and meta-analyses of clinical trials in coronary artery bypass grafting surgery have confirmed that aprotinin not only reduces transfusion requirements in cardiac surgery but also confers significant protection against platelet dysfunction, activation of the systemic inflammatory response, and perioperative stroke when administered at the full (or "Hammersmith") dose. This article reviews research from several independent groups to propose a novel mechanism through which the antithrombotic, anti-inflammatory, and neuroprotective mechanism might be mediated, via protection of the high-affinity thrombin receptor protease-activated receptor 1 (PAR1).

Aprotinin improves cerebral protection: Evidence from a survival porcine model

OBJECTIVE

Aprotinin is a serine protease inhibitor used during cardiac surgery to reduce blood loss and preserve platelet function. It has also been shown to reduce leukocyte activation during and after cardiopulmonary bypass. The goal of the study was to test the hypothesis that aprotinin could reduce cerebral injury after low-flow cardiopulmonary bypass and deep hypothermic circulatory arrest.

METHODS

Sixteen piglets (mean weight, 13.6 +/- 1.3 kg) were randomly assigned to receive aprotinin or placebo (8 animals per group) before a 120-minute period of deep hypothermic circulatory arrest (15 degrees C) or 25 mL x kg(-1) x min(-1) low-flow cardiopulmonary bypass (25 degrees C or 34 degrees C). Piglets had a cranial window placed over the parietal cerebral cortex for direct examination of the microcirculation by means of intravital microscopy. Rhodamine-stained leukocytes were observed in postcapillary venules, with analysis for adhesion and rolling. Plasma was labeled with fluorescein isothiocyanate-dextran for assessment of functional capillary density. Neurologic and histologic scores were used as the primary outcome measures.

RESULTS

During rewarming, the mean number of both rolling and adherent leukocytes was significantly lower after aprotinin administration (P < .05). At 5 and 15 minutes of rewarming, functional capillary density recovered faster with aprotinin treatment (P < .05). Functional outcome (neurologic deficit score) on postoperative day 1 was significantly improved in aprotinin-treated piglets (P < .05).

CONCLUSIONS

Aprotinin reduces inflammation and improves neurologic outcome after a prolonged period of deep hypothermic circulatory arrest or low-flow cardiopulmonary bypass.

Cardiopulmonary bypass and renal injury

Renal dysfunction following cardiopulmonary bypass (CPB) is well recognized. The extent of perioperative renal impairment ranges from subclinical injury to established renal failure requiring dialysis. Its incidence varies considerably, depending on the definition and criteria used in the different studies. Acute renal failure (ARF) affects 1-5% of patients and remains a major cause of morbidity and mortality. Co-morbidities, including diabetes mellitus, impaired left ventricular function and advanced age, are recognized predisposing factors. The pathophysiology is multifactorial and is thought related to the systemic inflammatory response and renal hypoperfusion secondary to extracorporeal circulation. Non-pulsatile flow during CPB is thought to be an important aetiological factor, resulting in renal vasoconstriction and ischaemic renal injury. A theoretical reduction in the incidence and severity of postoperative renal impairment has been proposed by advocating the use of pulsatile flow during CPB, or eliminating CPB, especially in high-risk patients. The current evidence, however, is conflicting. Several large observational studies, including a large proportion of high-risk patients, have demonstrated a significant reduction in the frequency of renal failure in patients undergoing off-pump surgery. As older, sicker patients increasingly constitute the cardiac surgical population, the incidence of postoperative renal injury is likely to increase. Further studies addressing various renoprotective strategies in higher-risk patients are awaited.

Aprotinin to Improve Cerebral Outcome after Hypothermic Circulatory Arrest: A Study in a Surviving Porcine Model

BACKGROUND

Aprotinin is a serine protease inhibitor, which is usually used during cardiac surgery to reduce blood loss. There is evidence that aprotinin has neuroprotective effects during ischemia. We planned this study to evaluate its potential neuroprotective efficacy during hypothermic circulatory arrest (HCA).

METHODS

Twenty piglets with a median weight of 25.7 kg (interquartile range, 23.9-26.6) were randomly assigned to receive aprotinin or placebo prior to a 75-minute period of HCA at 18 degrees C. Brain microdialysis parameters and neurological and histological scores were the primary outcome measures.

RESULTS

Changes in brain metabolic parameters and histopathological findings were favorable in the aprotinin group. Brain lactate concentrations were significantly lower in the aprotinin group during the experiment (P = .02) along with blood lactate concentrations in the aprotinin group (P = .023). Brain glucose was significantly higher during the experiment (P = 0.02). Intracranial pressure tended to be higher in the control group. Two of 10 animals in the aprotinin group and 4 of 10 in the control group failed to reach full recovery on the seventh postoperative day. Four animals of 10 in the aprotinin group and 6 animals of 10 in the control group had brain infarction (P = .40).

CONCLUSIONS

The present data suggest that aprotinin mitigates cerebral damage and improves neurological outcome following a period of HCA.

Aprotinin decreases ischemic damage during coronary revascularization

BACKGROUND AND AIM

This study sought to determine whether the favorable anti-inflammatory effects of aprotinin might limit ischemic damage during the revascularization of ischemic myocardium.

METHODS

Twenty pigs underwent 90 minutes of coronary occlusion followed by 45 minutes of blood cardioplegic arrest and 180 minutes of reperfusion. Ten animals received a loading dose of aprotinin (40,000 kallikrein inhibiting units/kg) during the start of coronary occlusion followed by an infusion of 20,000 kallikrein inhibiting units/kg/hour. Ten other animals received no aprotinin. Summary statistics are expressed as the mean +/- standard error.

RESULTS

The aprotinin-treated animals required less cardioversions for ventricular arrhythmias (1.0 +/- 0.7 vs. 3.6 +/- 0.6; p < 0.001), accumulated less lung water (1.0 +/- 0.2% change vs. 6.2 +/- 0.9% change; p = 0.038), had more complete coronary relaxation to bradykinin (34.1 +/- 5.9% change vs. 9.2 +/- 3.5% change; p = 0.01), and had reduced infarct size (area necrosis/area risk = 20 +/- 1.1% vs. 39 +/- 1.2%; p = 0.003).

CONCLUSIONS

Aprotinin limits ischemic injury during acute coronary revascularization by decreasing ventricular arrhythmias and lung edema, preserving endothelial function, and minimizing myocardial necrosis.

Aprotinin inhibits proinflammatory activation of endothelial cells by thrombin through the protease-activated receptor 1

OBJECTIVE

Thrombin is generated in significant quantities during cardiopulmonary bypass and mediates adverse events, such as platelet aggregation and proinflammatory responses, through activation of the high-affinity thrombin receptor protease-activated receptor 1, which is expressed on platelets and endothelium. Thus antagonism of protease-activated receptor 1 might have broad therapeutic significance. Aprotinin, used clinically to reduce transfusion requirements and the inflammatory response to bypass, has been shown to inhibit protease-activated receptor 1 on platelets in vitro and in vivo. Here we have examined whether aprotinin inhibits endothelial protease-activated receptor 1 activation and resulting proinflammatory responses induced by thrombin.

METHODS

Protease-activated receptor 1 expression and function were examined in cultured human umbilical vein endothelial cells after treatment with alpha-thrombin at 0.02 to 0.15 U/mL in the presence or absence of aprotinin (200-1600 kallikrein inhibitory units/mL). Protease-activated receptor 1 activation was assessed by using an antibody, SPAN-12, which detects only the unactivated receptor, and thrombin-mediated calcium fluxes. Other thrombin-dependent inflammatory pathways investigated were phosphorylation of the p42/44 mitogen-activated protein kinase, upregulation of the early growth response 1 transcription factor, and production of the proinflammatory cytokine interleukin 6.

RESULTS

Pretreatment of cultured endothelial cells with aprotinin significantly spared protease-activated receptor 1 receptor cleavage (P < .0001) and abrogated calcium fluxes caused by thrombin. Aprotinin inhibited intracellular signaling through p42/44 mitogen-activated protein kinase (P < .05) and early growth response 1 transcription factor (P < .05), as well as interleukin 6 secretion caused by thrombin (P < .005).

CONCLUSIONS

This study demonstrates that endothelial cell activation by thrombin and downstream inflammatory responses can be inhibited by aprotinin in vitro through blockade of protease-activated receptor 1. Our results provide a new molecular basis to help explain the anti-inflammatory properties of aprotinin reported clinically.

Effect of aprotinin on the frequency of postoperative atrial fibrillation or flutter

PURPOSE

The relationship between adding aprotinin to standard care and the frequency of postoperative atrial fibrillation or flutter (POAF) in patients undergoing cardiothoracic surgery (CTS) with cardiopulmonary bypass (CPB) was studied.

METHODS

This was a retrospective cohort evaluation. All patients at a hospital who underwent CTS with CPB between October 1999 and October 2003 and who received aprotinin during surgery were included in the treatment group. Control patients were those who did not receive aprotinin; they were matched with treatment group patients for age, valvular surgery, history of atrial fibrillation or flutter, renal dysfunction, peripheral artery disease, smoking, angina, diabetes mellitus, congestive heart failure, previous CTS, sex, beta-blocker intolerance, and use of preoperative digoxin. The primary endpoint was POAF; secondary endpoints were perioperative transfusion use, length of stay (LOS), stroke, myocardial infarction, renal failure, graft occlusion, and death.

RESULTS

A total of 438 patients (219 per group) were evaluated. The patients' mean age was 68 years, 67% were men, and 74% had had valvular surgery. Patients who received aprotinin (mean +/- S.D. dose, 2.75 million +/- 1.24 million kallikrein-inhibiting units) did not have a significantly lower frequency of POAF than control patients (28% versus 27%, respectively [p = 0.92]), nor was there a significant difference in secondary endpoints.

CONCLUSION

Aprotinin therapy was not associated with a significant reduction in POAF in patients undergoing CTS with CPB. Perioperative transfusion use, LOS, stroke, myocardial infarction, renal failure, graft occlusion, and mortality also did not differ significantly between aprotinin and control groups.

Aprotinin improves kidney function and decreases tubular cell apoptosis and proapoptotic signaling after renal ischemia-reperfusion

OBJECTIVE

The purpose of the study was to determine the effects of aprotinin on (1) renal function, (2) apoptosis and apoptotic signaling, and (3) the inflammatory response of the kidney after ischemia-reperfusion injury.

METHODS

Male rats underwent a sham procedure or left renal ischemia for 1 hour. Rats were divided into three groups and received no reperfusion, reperfusion for 1 hour, or reperfusion for 24 hours. The animals undergoing ischemia received saline solution alone or aprotinin (60,000 kIU/kg). At the end of the experiment, a sample for serum creatinine was taken and the left kidney was harvested. The kidney was analyzed for expression of tumor necrosis factor alpha, interleukin 1beta, and interleukin 6 (enzyme-linked immunosorbent assay and reverse transcriptase-polymerase chain reaction) and activation of p38 mitogen-activated protein kinase, caspase 3, and caspase 8 (Western blot). The kidney was assessed for apoptosis with enzyme-linked immunosorbent assay and by terminal deoxynucleotidyl transferase biotin-deoxyuridine triphosphate nick-end labeling staining of tissue slides.

RESULTS

Aprotinin significantly decreased the rise in serum creatinine and apoptosis caused by ischemia-reperfusion. Aprotinin significantly reduced interleukin 1 and 6 messenger RNA production and showed a trend toward reducing tumor necrosis factor messenger RNA production after ischemia. Aprotinin also significantly reduced caspase 8 activation and showed a trend toward decreasing p38 mitogen-activated protein kinase activation after 1 hour of reperfusion.

CONCLUSION

These results suggest that aprotinin provides protection from renal ischemia-reperfusion injury. They also suggest that aprotinin may do so by affecting apoptotic signaling and inflammatory cytokine production. Aprotinin is a potential therapeutic measure in clinical situations where renal ischemia-reperfusion injury can be anticipated, provided adequate heparinization is possible.

CD11b may be a less satisfactory indicator for cardiac ischemia-reperfusion injury in coronary artery bypass graft surgery with cardiopulmonary bypass than cardiac troponin I

STUDY OBJECTIVE

To investigate whether CD11b on neutrophils can be used as a marker to predict myocardial ischemia-reperfusion injury for patients undergoing coronary artery bypass graft (CABG) surgery on cardiopulmonary bypass (CPB).

DESIGN

Prospective, observational study.

SETTING

University teaching hospital and university hospital laboratories.

PATIENTS

Twelve adults, physical status II and III (American Society of Anesthesiologists) patients scheduled for elective CABG surgery on CPB.

INTERVENTIONS

Anesthesia and surgical interventions were performed according to standard procedures. Coronary sinus was cannulated for retrograde cardioplegia perfusion and for coronary sinus blood sampling. The blood samples were collected from systemic and coronary venous sinus blood respectively at several time points before CPB, during CPB, and after declamping of the ascending aorta.

MEASUREMENTS AND MAIN RESULTS

CD11b expressions in systemic circulation blood increased significantly during CPB and maintained higher levels after cardiac reperfusion (P < .05); on the other hand, CD11b expressions in coronary sinus blood declined gradually and reached their lowest level at 5 minutes after aortic declamping. The differences in CD11b expressions between systemic circulatory blood and coronary sinus blood after cardiac reperfusion were significant (P < .05). Cardiac troponin I (cTnI) concentrations in both systemic circulatory blood and coronary sinus blood increased significantly after cardiac reperfusion (P < .05), and the concentrations of cTnI in coronary sinus blood increased much higher than the corresponding concentrations of cTnI at each time point (P < .05).

CONCLUSION

CD11b expression on neutrophils may not be a reliable predictor for myocardial ischemia-reperfusion injury in CABG surgery on CPB because of the possible sequestration of neutrophils in myocardium.

The systemic inflammatory response syndrome and cardiopulmonary bypass

Cardiac surgery using cardiopulmonary bypass (CPB) provokes a systemic inflammatory response. This is mainly triggered by contact activation of blood by artificial surfaces of the extracorporeal circuit. Although often remaining sub-clinical and resolving promptly at the end of CPB, in its most extreme form this inflammatory response may be associated with the development of the systemic inflammatory response syndrome (SIRS) that can often lead to major organ dysfunction (MODs) and death. Here, we review the pathophysiology behind the development of this "whole body" inflammatory response and some of the methods currently used to minimise it.

Effect of aprotinin on clinical outcomes in coronary artery bypass graft surgery: A systematic review and meta-analysis of randomized clinical trials

OBJECTIVE

Despite proven blood transfusion benefits, aprotinin may be underused in coronary artery bypass grafting. Reluctance to use aprotinin may stem from safety concerns. The current objective was to evaluate clinical outcomes (mortality, myocardial infarction, renal failure, stroke, atrial fibrillation) in patients undergoing coronary artery bypass grafting who receive aprotinin by performing a quantitative overview of published, randomized, controlled trials.

METHODS

MEDLINE, EMBASE, and PHARMLINE (1988-2001) and reference lists of relevant articles were searched for coronary artery bypass grafting studies. Criteria for data inclusion were as follows: (1) random allocation of study treatments, (2) placebo control, (3) enrollment only of patients undergoing coronary artery bypass grafting, (4) no combination with another experimental medication or device, and (5) prophylactic and continuous intraoperative use.

RESULTS

Data from 35 coronary artery bypass grafting trials (n = 3879) confirm that aprotinin reduces transfusion requirements (relative risk 0.61, 95% confidence interval 0.58-0.66) relative to placebo, with a 39% risk reduction. Aprotinin therapy was not associated with increased or decreased mortality (relative risk 0.96, 95% confidence interval 0.65-1.40), myocardial infarction (relative risk 0.85, 95% confidence interval 0.63-1.14), or renal failure (relative risk 1.01, 95% confidence interval 0.55-1.83) risk, but it was associated with a reduced risk of stroke (relative risk 0.53, 95% confidence interval 0.31-0.90) and a trend toward reduced atrial fibrillation (relative risk 0.90, 95% confidence interval 0.78-1.03).

CONCLUSIONS

Aprotinin reduces transfusion requirements. Concerns that aprotinin therapy is associated with increased mortality, myocardial infarction, or renal failure risk is not supported by data from published, randomized, placebo-controlled clinical trials. Evidence for a reduced risk of stroke and a tendency toward reduction of atrial fibrillation occurrence was observed in patients who received aprotinin.

Activation of complement and leukocyte receptors during on- and off pump coronary artery bypass surgery

OBJECTIVE

The aim of this prospective, randomised study was to investigate the influence of extracorporeal circulation on the inflammatory response, our hypothesis being that off pump coronary artery bypass grafting (OFFCAB) procedures would generate less activation than on pump procedures (ONCAB).

METHODS

Patients admitted for elective CABG were randomised to either ONCAB or OFFCAB surgery and blood samples were taken during and up to 24 h after the operation. We measured complement factors C5a and the terminal complement complex (TCC, C59-b), and the interleukins IL-6 and IL-8. Leukocytes were studied for cellular counts and adhesion molecules (CD11b, CD35 and CD62L) by flow cytometry. We included a combination of activity markers with different aspects of neutrophil function and combined these with in vitro activation.

RESULTS

The complement factors C5a and TCC showed a more rapid (P=0.02, P<0.001) and TCC a more profound (P<0.001) increase in the ONCAB group than in the OFFCAB group during the operation, after that there were no inter-group differences. Cellular markers, cell counts and interleukin levels were activated by surgery but with no difference between groups.

CONCLUSION

This prospective, randomised study showed less complement activation in low risk OFFCAB, compared to ONCAB patients.

Monocyte Fc gamma receptor expression in patients undergoing coronary artery bypass grafting

BACKGROUND

Cardiopulmonary bypass is associated with an inflammatory response with potential deleterious effects. The white cell subpopulation mostly investigated so far is the neutrophil. To date very little has been investigated regarding the role of the monocyte/macrophage. This study focuses on the expression of Fc gamma receptors I, II, and III by monocytes in patients undergoing cardiopulmonary bypass.

METHODS

We studied the surface expression of Fc gamma receptors I, II, and III by flow cytometry on gated monocyte subpopulations in the whole blood of adult patients undergoing elective coronary artery bypass grafting. Blood samples were drawn preoperatively and at 15 minutes, 1, 2, 4, 24, 48, and 72 hours, and 6 days postoperatively. A second group of patients undergoing lung resection surgery were studied in a similar fashion.

RESULTS

Neither Fc receptor I nor receptor II expression were significantly changed throughout the time points studied. Fc receptor III expression was reduced at 2 and 4 hours (p = 0.016 and 0.002) and increased at 24, 48, and 72 hours after commencement of CPB on a selected subpopulation (15%-35%) of monocytes (p = 0.004, < 0.001, and < 0.001, respectively). This expression returned to preoperative levels by the sixth postoperative day. There were no statistically significant changes in the lung resection group.

CONCLUSIONS

Our study demonstrated that cardiopulmonary bypass is associated with a biphasic Fc gamma receptor III expression on a subpopulation of peripheral blood monocytes up to 3 days postoperatively.

Hemoglobin Scavenger Receptor CD163 Mediates Interleukin-10 Release and Heme Oxygenase-1 Synthesis

The recently described hemoglobin scavenger receptor CD163 mediates the endocytosis of hemoglobin:haptoglobin (Hb:Hp) complexes and thereby counters Hb-induced oxidative tissue damage after hemolysis. Although CD163 has been indirectly associated with antiinflammatory and atheroprotective activity, no ligand-receptor-effector pathway has yet been described for this receptor. To understand the significance of CD163 and more clearly define downstream pathways linked to inflammatory resolution, we studied the expression and function of CD163 in human monocytes/macrophages using both in vitro and in vivo models. Differentiation of human blood monocytes into macrophages either by in vitro culture or in resolving cantharidin-induced skin blisters led to an equivalent increase (>15x) in CD163 expression. Elevated CD163 levels were also noted on circulating monocytes in cardiac surgical patients during the resolution phase of the systemic inflammatory response to cardiopulmonary bypass surgery. In each case, binding of Hb:Hp to CD163-bearing cells elicited potent interleukin-10 secretion, and this was inhibited by the anti-CD163 antibody RM3/1. Release of interleukin-10, in turn, induced heme oxygenase-1 stress protein synthesis via an autocrine mechanism. Such induction of heme oxygenase-1 was observed in vivo 24 to 48 hours after the onset of cardiopulmonary bypass surgery. These results identify novel antiinflammatory and cytoprotective effector pathways in human monocytes/macrophages related to Hb scavenging and metabolism, which may have relevance in atheroprotection, wound healing, and patient recovery postoperatively.

The effect of haemodilution on blood-biomaterial contact-mediated CD11b expression on neutrophils: ex vivo studies

Modern cardiopulmonary bypass (CPB) systems are getting smaller, both in terms of the exposed surface area of biomaterials and the priming volume. In a series of studies utilizing a rat recirculation model, we demonstrated that the magnitude of the inflammatory response seen under these conditions is proportional to the surface area of exposed material, a finding that supports the use of miniature systems in terms of moderating the inflammatory response. However, the second impact of miniature perfusion systems, the reduced priming volume with concomitant reduction in haemodilution, was not investigated with reference to inflammation. The present study was designed to determine whether this change in CPB haematocrit profile has any effect on the inflammatory response. In common with previous studies by this group, we employed the expression of the integrin CD11b on neutrophils as a marker of neutrophil activation, and hence the inflammatory response, in a rat recirculation biomaterial testing model, containing di-(2-ethyl-hexyl)-phthalate plasticized polyvinyl chloride of the type commonly employed in CPB circuits. The results demonstrated that neutrophil activation is influenced by haemodilution. We studied five groups of animals, each with different mean induced haematocrit: Group 1 (41.3 +/- 1.27%); Group 2 (30.93 +/- 2.85%); Group 3 (24.83 +/- 1.36%); Group 4 (20.60 +/- 3.47%); Group 5 (20.48 +/- 1.31%). Groups 1 and 5 animals were controls, neither of which underwent the period of recirculation. Rather, these controls were employed to isolate the noncontact effect of haemodilution on CD11b expression. We found that there were differences in per cent change in CD11b expression from start to end of the recirculation period between Group 1 (109.54 +/- 49.53%), Group 2 (189.1 +/- 18.68%), Group 3 (224.28 +/- 43.97), Group 4 (368.97 +/- 24.28%) and Group 5 (127 +/- 57.8%). There were intergroup statistically significant differences (p < 0.05). These results confirm that there is a relationship between haematocrit level and biomaterial contact-mediated activation of neutrophils. Furthermore, these studies confirm that haemodilution alone has no effect on neutrophil activation. One possible explanation for this outcome is that with higher levels of haemodilution, neutrophils have a greater opportunity to contact surface 'receptor' sites on the biomaterial, resulting in more neutrophil activation. Whatever the mechanism, these data tend to support the modern trend towards lower circuit surface area and higher haematocrit.

Inflammatory response of rat and human neutrophils exposed to di-(2-ethyl-hexyl)-phthalate-plasticized polyvinyl chloride

A series of in vitro studies were designed to determine whether di-(2-ethyl-hexyl)-phthalate (DEHP)-plasticized polyvinyl chloride (PVC) and DEHP itself initiated an inflammatory response in both human and rat blood. Additionally, the effect of methanol washing of the PVC on the inflammatory response was studied in both blood types. Blood from both species was exposed to first, no material; second, ground DEHP-plasticized PVC; third, methanol-washed ground DEHP-plasticized PVC; and fourth, known concentrations of DEHP. The expression of the integrin CD11b was employed as a marker of the inflammatory response. After 20 minutes' exposure to PVC, CD11b expression increased to 210 +/- 32% of baseline in human blood and to 238 +/- 21.7% in rodent blood. Both blood types showed an increase in CD11b expression with increasing concentrations of DEHP (214 +/- 40.8% of baseline levels in human blood and 237 +/- 14.5% in rodent blood at the highest concentration). Methanol washing resulted in a significant moderation in CD11b upregulation in both blood types; 117 +/- 27% of baseline in human and 150 +/- 14.7% in rodent. These results support the hypothesis that DEHP-plasticized PVC and DEHP itself are proinflammatory in blood from both species, and suggest that the rodent is an appropriate model for studies of this nature.

Aprotinin and preservation of myocardial function after ischemia-reperfusion injury

Ischemia-reperfusion injury, a complex process involving the generation and release of inflammatory cytokines, accumulation and infiltration of neutrophils and macrophages, release of oxygen free radicals, activation of proteases, and generation of nitric oxide (NO), may result in myocardial dysfunction and possible injury to other major organs. Aprotinin, a nonspecific serine protease inhibitor used to reduce the blood loss and transfusion requirements accompanying cardiac surgery, has dose-dependent effects on coagulation, fibrinolytic, and inflammatory variables. Data indicate that aprotinin may provide protection from ischemia-reperfusion injury. In myocardial tissue models of ischemia and reperfusion, aprotinin has been shown to reduce uptake of tumor necrosis factor-alpha (TNF-alpha), generation of NO, and accumulation of leukocytes. Improved myocardial function has been observed with aprotinin treatment in animal models of ischemia-reperfusion injury. In humans, data indicate that integrin expression associated with leukocyte transmigration as well as markers of myocardial damage are reduced in patients receiving aprotinin. Further, data suggest that patients who receive aprotinin may have a reduced need for inotropic support and a decreased incidence of postoperative atrial fibrillation. In all, review of this topic indicates that aprotinin may reduce aspects of ischemia-reperfusion injury and prospective clinical studies are needed to evaluate the impact of aprotinin on associated patient outcomes.

High-dose aprotinin reduces activation of hemostasis, allogeneic blood requirement, and duration of postoperative ventilation in pediatric cardiac surgery

BACKGROUND

Though multiple studies have affirmed the effectiveness of aprotinin in reducing blood loss in adult cardiac surgery, the possible benefit in pediatric cardiac surgery is controversial.

METHODS

In a double-blind, randomized, and placebo-controlled study, the efficacy of aprotinin in attenuating the hemostatic and inflammatory activation during cardiopulmonary bypass in 60 patients weighing less than 10 kg was investigated. Secondary endpoints were the influence of aprotinin on the reduction of blood loss and allogeneic blood requirement, as well as postoperative oxygenation and length of mechanical ventilation. Aprotinin was administered in a high-dose of 3 x 10(4) KIU/kg plus a bolus of 5 x 10(5) KIU (not weight adjusted) added to the pump prime.

RESULTS

Aprotinin plasma concentration at the end of cardiopulmonary bypass (CPB) was with 184 +/- 45 KIU/mL, within the targeted range of 200 KIU/mL. Coagulation and fibrinolysis were suppressed (F1.2 1 hour after CPB: 5.35 +/- 2.9 nmol/L vs 14.5 +/- 23.1 nmol/L; D-dimer 1 hour after CPB: 0.63 +/- 0.6 ng/mL vs 2.3 +/- 3.1 ng/mL; p < 0.05), inflammatory markers (interleukin [IL]-6, IL-8, IL-10) increased over time without significant differences between the groups, and only complement C3a activation was significantly attenuated at the end of CPB in the aprotinin group. Chest tube drainage was significantly reduced (24 hours: median 13.5 [IQR 12.2] mL/kg vs 19.4 [8.2] mL/kg; p < 0.05). All patients received one unit of packed cells to prime the heart lung machine. A second unit was needed significantly less often in the aprotinin group (13% vs 47%; p < 0.05). Postoperative oxygenation (pO2/FIO2 172 [IQR 128] mm Hg vs 127 [74]; p < 0.05) improved, and the time on ventilator was shorter in the aprotinin group (median 45 hours [IQR 94] vs 101 [IQR 74]; p < 0.05). No side effects were attributable to the use of aprotinin.

CONCLUSIONS

High-dose aprotinin effectively attenuated hemostatic activation and reduced blood loss and transfusion requirement in pediatric cardiac surgery. Postoperative ventilation was also shortened in the aprotinin group.

The effect of methanol washing of plasticized polyvinyl chloride on biomaterial-contact-mediated CD11b (mac-1) expression in a rat recirculation model

Our objective was to assess whether using a methanol wash to reduce the level of plasticizer present on the surface of medical-grade polyvinyl chloride (PVC) has a moderating effect on the expression of CD11b (mac-1) on neutrophils in rats undergoing recirculation. The study was carried out on 3 groups of 10 adult male Sprague-Dawley rats weighing between 350 and 450 g. In the 2 test groups, the animals were exposed to 48 cm(2) of di-(2-ethyl-hexyl)-phthalate (DEHP)-plasticized PVC in a parallel plate recirculating test cell through which blood was recirculated at 1.5 ml/min. In the first test group, the PVC was untreated; in the second test group, the PVC was washed in methanol to reduce the level of plasticizer on the surface. The test cell was connected to the right femoral circulation, and recirculation was established for a period of 60 min. Blood samples were taken at 0, 30, and 60 min for assessment of CD11b expression on neutrophils using flow cytometric analysis. In a third group of 10 control experiments, rats underwent the entire surgical procedure, but without recirculation through the test cell. There was statistically significant (p < 0.001) lower Cd11b expression on neutrophils in the blood of rats perfused through the cell containing methanol-washed PVC after 30 min and at 60 min. CD11b expression was significantly (p < 0.001) lower in the control group than in both test groups at both the 30 and 60 min time points and at the 60 min time point on comparison with the group where blood was perfused through methanol-washed PVC. These results demonstrate that the biomaterial-contact-mediated upregulation of CD11b may be significantly reduced by employing a methanol-washing technique on the plasticized PVC. Although this technique does not entirely eliminate the expression of CD11b on neutrophils, the difference is significant and suggests the role of the plasticizer in the development of this inappropriate inflammatory response.

The antithrombotic and antiinflammatory mechanisms of action of aprotinin

Aprotinin (Trasylol) is generally regarded to be an effective hemostatic agent that prevents blood loss and preserves platelet function during cardiac surgery procedures requiring cardiopulmonary bypass (CBP). However, its clinical use has been limited by the concern that such a potent hemostatic agent might be prothrombotic, particularly in relation to coronary vein graft occlusion. In this review we present a mechanism of action that challenges such a viewpoint and explains how aprotinin can be simultaneously hemostatic and antithrombotic. Aprotinin achieves these two apparently disparate properties by selectively blocking the proteolytically activated thrombin receptor on platelets, the protease-activated receptor 1 (PAR1), while leaving other mechanisms of platelet aggregation unaffected. We also review recent research leading to the discovery of novel antiinflammatory targets for aprotinin. A better understanding of its mechanisms of action has led to the conclusion that aprotinin is a remarkable drug with the capacity to correct many of the imbalances that develop in the coagulation system and the inflammatory system after CPB. Nonetheless, it has been clinically underused for fear of causing thrombotic complications, a fear that in light of recent evidence may be unfounded.

New antiinflammatory and platelet-preserving effects of aprotinin

The clinical benefit of aprotinin with respect to improved hemostasis, platelet function, and inflammatory response to cardiopulmonary bypass (CPB) surgery has been well documented, but these benefits have been overshadowed by the concern that such a potently hemostatic agent might also be prothrombotic. In this article, we discuss recent advances in the understanding of the basic mechanism of aprotinin that have led to the identification of new antiinflammatory targets and the discovery that aprotinin is, in fact, antithrombotic with respect to platelets. Its antithrombotic action is mediated by the selective blocking of the major thrombin receptor, the protease-activated receptor 1 (PAR1), but not other receptors of platelet activation (ie, collagen, adenosine diphosphate [ADP], or epinephrine receptors). The selective targeting of PAR1 enables aprotinin to protect platelets from unwanted activation by thrombin generated during CPB surgery (consistent with a role in platelet-preservation), while permitting the participation of platelets in the formation of hemostatic plugs at wound and suture sites, where collagen, ADP, and epinephrine are most likely to be expressed. Aprotinin therefore exerts a subtle hemostatic yet antithrombotic mechanism of action, which, when allied with its multitiered antiinflammatory effect, makes this drug a valuable companion to cardiac surgery.

Systemic inflammation and cardiac surgery: an update

Cardiac surgery with cardiopulmonary bypass (CPB) is associated with the development of a systemic inflammatory response that can often lead to dysfunction of major organs. The systemic inflammation can be assessed intra- and postoperatively by measuring concentrations of inflammatory mediators in plasma and tissues. These concentrations, however, do not always correlate with the degree of observed organ dysfunction. Various strategies have been used to reduce inflammatory phenomena in patients undergoing CPB. Cardiac surgery without CPB has been performed increasingly with satisfactory results over the past few years. Attenuation of systemic inflammation and improved outcome in high risk patients are potential benefits of this technique. The emergence and expanding performance of cardiac surgical procedures without the use of CPB has given us an excellent tool to investigate the relative importance of CPB as a cause of systemic inflammation. Aprotinin is a protease inhibitor which is used in cardiac surgical patients for its haemostatic effects. Aprotinin has anti-inflammatory properties, the nature of which have not been completely clarified. This article presents a summary of the published literature investigating inflammatory response and organ dysfunction in patients who have cardiac surgery without CPB. It also presents an overview of recent data on the anti-inflammatory action mechanisms of aprotinin.

Effect of aprotinin on endothelial cell activation

BACKGROUND

Cardiopulmonary bypass surgery is often accompanied by a systemic inflammatory response, which can lead to postoperative complications in high-risk patients. This is mediated in part through a systemic rise in inflammatory cytokine levels and the sequestration of leukocytes within organs. Aprotinin has previously been shown to exert an anti-inflammatory effect by preventing the capacity of leukocytes to transmigrate through vascular endothelium. Here we have focused on whether aprotinin has an effect on endothelial cell activation and adhesion molecule expression in response to tumor necrosis factor-alpha, particularly with reference to whether aprotinin inhibits tumor necrosis factor-stimulated neutrophil transendothelial migration.

METHODS AND RESULTS

Intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin expression was studied in tumor necrosis factor-alpha-activated human umbilical vein endothelial cells in the presence of aprotinin at 200, 800, and 1600 kIU/mL. Aprotinin inhibited tumor necrosis factor-alpha-stimulated expression of intercellular adhesion molecule-1 (P =.019 at 1600 kIU/mL) and vascular cell adhesion molecule-1 (P =.003 at 1600 kIU/mL) but not E-selectin. Similar results were obtained in the dermal microvascular endothelial cell line, HMEC-1, which exhibited diminished intercellular adhesion molecule-1 expression in the presence of aprotinin (P =.040 at 800 kIU/mL and P <.001 at 1600 kIU/mL). Aprotinin also significantly inhibited neutrophil transmigration across tumor necrosis factor-alpha-activated human umbilical vein endothelial cells (P =.046 at 1600 kIU/mL).

CONCLUSIONS

We have demonstrated that aprotinin inhibits intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, but not E-selectin, expression on tumor necrosis factor-alpha-activated endothelial cells and that transendothelial migration by neutrophils is also specifically suppressed under these conditions. Our results indicate that endothelial cells can be specifically targeted by aprotinin, therefore adding to our understanding of the anti-inflammatory mechanism of action of aprotinin during cardiopulmonary bypass.

The effect of circuit surface area on CD11b(mac-1) expression in a rat recirculation model

The aim of the study was to assess the effect of exposed surface area of diethylhexylphthalate plasticized polyvinylchloride (PVC) on the expression of the adhesion molecule CD11b(mac-1) on neutrophils and to determine whether there is any apparent advantage in the current trend in reducing circuit surface area in terms of neutrophil activation. The study was carried out using a parallel plate rodent recirculation biomaterial testing model on 4 groups of 10 adult male Sprague Dawley rats weighing between 350 and 450 g. One group comprised the control group in which there was no biomaterial exposure. In the remaining 3 groups, the animals were subjected to either high (48 cm2), intermediate (24 cm2), or low (12 cm2) biomaterial surface area exposure. The parallel plate test cell was connected to the right femoral circulation and recirculation initiated at a flow rate of 1.5 ml/min for a period of 60 min. Blood samples were taken at 0, 30, and 60 min for the assessment of CD11b expression. Cd11b was assessed using flow cytometric analysis on neutrophils. The results demonstrated that there was a surface area related effect in the upregulation of CD11b. The difference at the terminal sample point between the highest surface area group (293.95 +/- 18.57%) and the low surface area group (133.80 +/- 49.31%) was highly statistically significant (p < 0.001). These results demonstrate that there may be some gain in terms of reduced inflammatory response from reducing the exposed surface area of PVC in extracorporeal perfusion circuits.

Update on cardiopulmonary bypass

Investigations into cardiopulmonary bypass continue to refine knowledge and clinical practice. Recent investigations have emphasized neurological complications, introducing the possibility of genetic predisposition as a risk factor. Appropriate flows, pressures, and hematocrit levels during cardiopulmonary bypass continue to create controversy. Whereas previous debate has centered around appropriate temperature management, recent discussions consider the possibility that mild hypothermia after cardiopulmonary bypass might be neuroprotective. Meta-analyses and prospective investigations continue to suggest the virtual equivalence of aprotinin and lysine analogues in reducing bleeding and transfusion after cardiopulmonary bypass. Several recent studies identified the mechanisms and severity of the inflammatory response to cardiopulmonary bypass, as well as possible techniques for attenuating inflammation.

Role of aprotinin in the management of patients during and after cardiac surgery

Management of patients undergoing cardiac surgery has evolved in recent years as more is understood about the physiological changes and responses that occur during and after cardiopulmonary bypass (CPB). In particular, our understanding of the mechanisms involved in haemostasis and in the inflammatory response to bypass surgery, has allowed significant refinements in patient management. Improvements in the pharmacological conservation of blood loss have been striking, particularly with the development of the serine protease inhibitor, aprotinin (Trasylol, Bayer). Aprotinin represents a significant improvement, especially for patients at high risk, since it reduces the need for allogeneic and (sometimes scarce) blood products. However, in view of its cost, making an appropriate selection of patients most at risk of serious blood loss is a major consideration in the use of aprotinin. While its mechanisms of action are not well understood, the use of aprotinin also appears to reduce inflammatory response to CPB.

Inhibition of neutrophil L-selectin shedding: a potential anti-inflammatory effect of aprotinin

The cardiopulmonary bypass (CPB)-related inflammatory response involves leucocyte activation and increased leucocyte-endothelial cell interaction. L-selectin is an adhesion molecule expressed on the surface of leucocytes which participates in the initial rolling step of the leucocyte-endothelial cell adhesion cascade. L-selectin is proteolytically cleaved off the surface of leucocytes when they become activated, an event that is regarded as a marker of leucocyte activation. Aprotinin is a protease inhibitor that has been used in cardiac surgery as a haemostatic agent and also exhibits certain anti-inflammatory properties. In this study, peripheral venous blood from volunteers was pre-incubated with aprotinin at 200, 800 and 1600 kallikrein inhibiting units (kiu)/ml and stimulated with the chemoattractants N-formyl-methyl-leucyl-phenylalanine (fMLP) or platelet activating factor (PAF). Surface expression of L-selectin on neutrophils was measured using a monoclonal antibody and flow cytometry. The results demonstrate that aprotinin inhibits shedding of L-selectin in a dose-dependent fashion (p=0.0278 and 0.0005, respectively, at 800 and 1600 kiu/ml for fMLP-stimulated shedding; p=0.0017 and 0.0010, respectively, at 200 and 800 kiu/ml for PAF-stimulated shedding). This effect may be of significance with respect to the anti-inflammatory action of aprotinin in patients undergoing CPB.