Platelet and neutrophil activation in cardiopulmonary bypass

Monocytes to lymphocytes multiplying platelets ratio as an early indicator of acute kidney injury in cardiac surgery with cardiopulmonary bypass: a retrospective analysis

OBJECTIVE

The monocyte-to-lymphocyte multiplying platelets ratio (MLPR) is a novel systemic inflammatory marker, deriving from the monocyte-to-lymphocyte ratio (MLR). However, the link between MLPR and acute kidney injury following cardiac surgery (CSA-AKI) with cardiopulmonary bypass (CPB) has not been investigated yet. We comprehensively explored the potential linear and nonlinear relationship between MLPR or MLR and CSA-AKI.

METHODS

Data of patients who underwent cardiac surgery with CPB between December 2018 and April 2021 were retrospectively collected at Fuwai Hospital, Beijing, China. MLPR was defined as monocyte count (×109/L) × 1000/(lymphocyte count (×109/L) × platelets (×109/L)). MLR was defined as monocyte count (×109/L)/lymphocyte count (×109/L). Logistic regression and restricted cubic spline (RCS) were used for linear and nonlinear analysis. The primary outcome was postoperative AKI within 48 h of after cardiac surgery.

RESULTS

Of the 2420 patients screened, 2387 eligible patients were enrolled in the final analysis; the mean age was 54.7 years, and 1501 [62.9%] were men. The incidence of AKI was 25.8%. Logistic regression showed that MLPR (odds ratio [OR] = 1.31, 95% confidence interval [CI]: 1.16-1.48, p < .001) and MLR (OR = 3.06, 95% CI: 1.29-7.29, p = .012) were independent risk factors for AKI. Moreover, in the RCS model with adjustment for age (median: 56), female sex, and history of diabetes, a significant statistical difference was detected between preoperative MLPR, MLR, and AKI (p for non-linearity <.001). The subgroup analyses revealed similar results.

CONCLUSIONS

The study revealed a nonlinear relationship between MLPR and MLR with AKI. MLPR exhibited a J-shaped curve, and MLR showed a favorable S-shaped curve in relation to AKI. Particularly, MLPR emerges as a promising clinical composite index for early CSA-AKI prediction. These findings emphasize the significance of MLPR as a valuable tool in clinical practice for timely identification and management of CSA-AKI.

The impact of del Nido cardioplegia solution on blood morphology parameters

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Low-level light therapy reduces platelet destruction during extracorporeal circulation

Extracorporeal circulation causes many deleterious effects on blood cells. Low-level light therapy (LLLT) in the red/near-infrared spectral range is known for its cytoprotective properties but its use during cardiopulmonary bypass (CPB) has not yet been studied. We aimed to assess whether LLLT protects platelets during CPB. 24 pigs were connected to 1-hour-CPB and observed for the next 23 hours. In 12 animals, blood circulating through the oxygenator was treated with LLLT. Platelet count and function were monitored throughout the experiment. The decrease in platelet count was greater in the control group, especially during CPB and after 24 hours. In LLLT group CD62P expression remained quite stable up to the 12^th hour of the experiment, whereas in the control group it continuously decreased till the end of observation. Platelets in the control group were more prone to aggregation in the postoperative period than at the beginning of the experiment, whereas platelets in the LLLT group aggregated similarly or less intense. Limitation of platelet loss, pattern of aggregation and CD62P expression suggest that LLLT may stabilize platelet function during CPB and diminish the negative effects associated with the interaction of cells with an artificial surface.

Possibilities of Combined Surgical Treatment of Lung Tumours and Heart Diseases

The purpose of the study was a retrospective evaluation of the outcome of surgical therapy of lung cancer in patients where there was concomitant cardiac disease and who underwent a cardiac operation either because of ischemic heart disease or because of valvular disease. These patients were operated on at various time intervals (two to ten months) after their cardiac operation. Some patients had their lung cancer surgery after the cardiac operation because of the high risk of possible cardiac postoperative complications; in one patient the lung operation preceded the cardiac one.

Interaction of Activated Leukocytes with Polymeric Microspheres

Three types of polymeric particles with different surface wettabilities, i.e., poly(methylmethacrylate) (PMMA), poly(methylmethacrylate-hydroxyethylmethacrylate) (P(MMA/HEMA)) and poly(methylmethacrylate)/poly(vinyl alcohol) PMMA/PVAL with a diameter of 1.5 μm were produced in this study. These particles were incubated with blood samples obtained both from three patients undergoing cardiopulmonary bypass. In the blood samples taken before the bypass operations, there was considerable phagocytosis and/or adhesion of the PMMA particles, i.e., 14±4 particles per monocyte and 11±3 particles per neutrophil. While there was almost no phagocytosis and/or adhesion of the P(MMA/HEMA) and PMMA/PVAL particles. In the blood samples which were taken during bypass operations, phagocytosis and/or adhesion of PMMA microspheres increased significantly. The P(MMA/HEMA) and/or PMMA/PVAL particles adhered, or were even phagocytosed by the activated leukocytes in this case. Leukocytes activated during the bypass operations gradually returned to normal in about 24 h.

Activation of the Clotting System: Heparin-Coated versus Non Coated Systems for Extracorporeal Circulation

The purpose of this experimental study was to compare heparin-coated versus non-coated systems for extracorporeal membrane oxygenation (ECMO), to investigate the dynamic course of clotting activation in both groups.

Methods.

Eight pigs weighing 19.7 (± 1.3) kg, each underwent ECMO for 24 hours. Two groups were formed: in group 1, heparin-coated circuits were used with low dose heparinization (10 IU/kg/hr), whereas in group 2 non-coated circuits with high dose heparinization (60 IU/kg/hr) were used. Coagulation was monitored by measuring prothrombin time, partial thromboplastin time, fibrinogen, antithrombin III (AT III) and specific markers of clotting activation (thrombin-antithrombin III complexes (TAT) and D-dimer). Furthermore, platelet count, hematocrit, activated clotting time (ACT), and plasma heparin concentration were determined regularly.

Results.

The dynamic course of the specific coagulation activation markers showed some differences: whereas TAT and D-dimer increased quickly in group 2, the increase in group 1 was delayed. Activation marker values tended to be lower in group 1 during the first six hours, after which no more differences between the groups were seen. After 24 hours of ECMO, TAT and D-dimer had nearly returned to baseline values. Platelets showed a continuous decrease throughout the experiment, which was very similar in both groups.

Conclusions.

The heparin coated system showed a distinct delay in clotting activation during the first six hours of ECMO. After six hours there were no more differences between the groups.

Strategies and Techniques for Neuroprotection in Coronary Artery Surgery

Patients undergoing coronary artery bypass grafting are at higher risk of neurologic events than demographi cally similar patients undergoing noncardiac surgery. Postoperative stroke has been shown to occur two to three times more frequently than in age-, gender-, and education-matched patients undergoing noncardiac vas cular or thoracic surgery. The incidence of more subtle brain syndromes, giving rise to symptoms of memory loss and cognitive deterioration as documented in up to 79% of coronary bypass patients, varies depending on whether prospective or retrospective data are analyzed, and whether or not serial cognitive testing is used, and is also significantly higher in coronary bypass patients. Various factors have been identified as causative in the genesis of perioperative neurologic injury in these pa tients. Although there is evidence that microgaseous and microparticulate emboli are instrumental in the production of postoperative cognitive impairment, the role of ascending aortic atherosclerosis is increasingly recognized as being the greatest single risk factor for postoperative stroke.

Adverse Central Nervous System Outcomes After Cardiopulmonary Bypass: A Beneficial Effect of Aprotinin?

This review considers the evidence for potential central nervous system benefits associated with use of anti- protease therapy for patients undergoing procedures involving cardiopulmonary bypass. Unfortunately, few randomized, controlled clinical trials have assessed the lysine analogue class of antifibrinolytics (ie, ∈-amino caproic acid, tranexamic acid) compared with the num ber investigating the efficacy of the enzyme-inactivator class of antifibrinolytic typified by the nonspecific serine protease inhibitors aprotinin and nafamostat.

Management and postoperative outcome in primary lung cancer and heart disease co-morbidity: a systematic review and meta-analysis

BACKGROUND

Co-morbidity of primary lung cancer (LC) and heart disease (HD), both requiring surgical therapy, characterizes a high risk group of patients necessitating prompt diagnosis and treatment. The aim of this study is the review of available evidence guiding the management of these patients.

METHODS

Postoperative outcome of patients operated for primary LC (first meta-analysis) and for both primary LC and HD co-morbidity (second meta-analysis), were studied. Parameters examined in both meta-analyses were thirty-day postoperative mortality, postoperative complications, three- and five-year survival probabilities. The last 36 years were reviewed by using the PubMed data base. Thirty-seven studies were qualified for both meta-analyses.

RESULTS

The pooled 30-day mortality percentages (%) were 4.16% [95% confidence interval (CI): 2.68-5.95] (first meta-analysis) and 5.26% (95% CI: 3.47-7.62) (second meta-analysis). Higher percentages of squamous histology and lobectomy, were significantly associated with increased (P=0.001) and decreased (P<0.001) thirty-day postoperative mortality, respectively (first meta-analysis). The pooled percentages for postoperative complications were 34.32% (95% CI: 24.59-44.75) (first meta-analysis) and 45.59% (95% CI: 35.62-55.74) (second meta-analysis). Higher percentages of squamous histology (P=0.001), lobectomy (P=0.002) and p-T1 or p-T2 (P=0.034) were associated with higher proportions of postoperative complications (second meta-analysis). The pooled three- and five- year survival probabilities were 68.25% (95% CI: 45.93-86.86) and 52.03% (95% CI: 34.71-69.11), respectively. Higher mean age (P=0.046) and percentage lobectomy (P=0.009) significantly reduced the five-year survival probability.

CONCLUSIONS

Lobectomy and age were both accompanied by reduced five-year survival rate. Also, combined aorto-coronary bypass grafting (CABG) with lobectomy for squamous pT1 or pT2 LC displayed a higher risk of postoperative complications. Moreover, medical decision between combined or staged surgery is suggested to be individualized based on adequacy of coronary arterial perfusion, age, patient's preoperative performance status (taking into account possible co-morbidities per patient), tumor's staging and extent of lung resection.

The effect of oxygenator membranes on blood: a comparison of two oxygenators in open-heart surgery

Open-heart surgery (OHS) requires cardiopulmonary bypass (CPB) in most patients. Membrane oxygenators are a critical component of the CPB system. Despite advancements in CPB technology, injury to blood components during CPB still occurs and may result in complications after surgery. The purpose of the present study was to evaluate the performance of the Medtronic Affinity NT® with Trillium coating and the Cobe Optima XP® oxygenators and compare their influence on blood components.

Two hundred and fifty-six male and female patients scheduled for urgent or elective cardiac surgery with CPB were randomly assigned to either the Affinity NT or the Optima XP oxygenators. Outcomes included platelets, hemoglobin, leukocyte counts, and O2 transfer, measured preoperatively and at 15, 45 and 75 min of CPB time. Blood loss was measured at six and 12 hours postoperatively. A modified intention-to-treat analysis was conducted.

The two groups were similar for age, sex, height, weight, body surface area, and blood components at baseline. There were no differences between the Affinity NT and Optima XP for any outcome measure, although a significant change with time was seen in platelets, hemoglobin, hematocrit and leukocytes, as well as O2transfer for both groups ( p <0.001). The Affinity NT oxygenator had a significantly lower difference in pressure across the membrane ( p <0.001) compared with the Optima XP.

In conclusion, the two oxygenators performed similarly with respect to their impact on blood components, O2transfer, and blood loss postoperatively during OHS with CPB. The Affinity NT had the smaller transmembrane pressure drop of the two.

Clinical evaluation of the LeukoGuard (LG-6) arterial line filter for routine open-heart surgery

Research has demonstrated that leucocyte depletion diminishes the deleterious effects that activated neutrophils have on the body following cardiopulmonary bypass (CPB). A clinical evaluation involving 36 patients (18 in each group) was conducted to compare the use of the Pall LG-6 (leucocyte-depleting) arterial line filter with the Pall EC PLUS filter for postoperative complications and lung function on routine open-heart cases. No differences were found between the groups for postoperative chest tube drainage, urine output, on bypass platelet drop, chest X-rays, blood usage and circulating elastase levels. Statistically significant differences were observed between immediately post-CPB pO 2 values and ventilator hours (EC PLUS = 13.3, LG-6 = 9.2). Many of the advantages of using leucocyte depletion that have been illustrated through experimental investigations were comparable to our clinical observations. We conclude that using the LG-6 leucocyte-depleting arterial line filter is a cost-effective method to reduce the complications known as 'postperfusion' syndrome.

Using Cone and Plate(let) Analyzer to Predict Bleeding in Cardiac Surgery

The cone and plate(let) analyzer is an established method for assessing platelet function. It evaluates adherence of platelets on an extracellular matrix, expressed as a percentage of surface coverage and the average size of the aggregates. The purpose of this study was to determine the applicability of the cone and plate(let) analyzer in monitoring platelet function and predicting postoperative bleeding. The relationship between postoperative bleeding, perioperative platelet function, and other parameters was studied. A significant decrease in surface coverage was detected upon establishment of cardiopulmonary bypass (from 6.9% ± 3.9% to 4.7% ± 1.7%) with a return to preoperative values at the end of surgery. Preoperative average size and surface coverage were the only parameters that significantly and linearly correlated with postoperative bleeding. Patients with an aggregate average size < 20 μm2 had a significantly higher incidence of severe bleeding (> 965 mL) than those with a size > 20 μm2 (44% vs. 0%), and a higher mean blood loss (908 ± 322 mL vs. 337 ± 78 mL). Similar results were obtained for surface coverage < 5%, indicating the predictive value of these parameters. Preoperative platelet function as evaluated by the cone and plate(let) analyzer is an independent risk factor determining postoperative bleeding.

Aggressive re-warming at 38.5 °C following deep hypothermia at 21 °C increases neutrophil membrane bound elastase activity and pro-inflammatory factor release

Background

Cardiopulmonary bypass (CPB) is often performed under hypothermic condition. The effects of hypothermia and re-warming on neutrophil activity are unclear. This study aimed to compare the effects of different hypothermia and re-warming regimens on neutrophil membrane bound elastase (MBE) activity and the release of pro-inflammatory factors from neutrophils.

Methods

Human neutrophils were exposed to different hypothermia and re-warming regimens. MBE activity and the release of interleukin (IL)-β1, IL-6, IL-8, and tumor necrosis factor (TNF)-α were measured.

Results

Neutrophil MBE activity was significantly reduced after 60-min moderate (28 °C) or deep (21 °C) hypothermic treatment. Compared with normothermic (37 °C) re-warming, aggressive re-warming (38.5°) for 120 min following deep hypothermia (21 °C) dramatically increased neutrophil MBE activity (P < 0.05). Co-incubation of neutrophils with platelet-rich plasma further increased MBE activity significantly under all the tested temperature regimens. IL-β1 release from neutrophils was significantly higher after deep hypothermia (21 °C) followed by normothermic (37 °C) re-warming than after moderate hypothermia (28 °C) followed by normothermic re-warming (P < 0.05). Aggressive re-warming (38.5°) following deep hypothermia significantly increased the release of IL-β1, IL-8, and TNF-α from neutrophil compared with moderate re-warming (37 °C) (all P < 0.05).

Conclusion

Aggressive re-warming following deep hypothermia may contribute to CPB-associated tissue injury by increasing neutrophil MBE activity and stimulating pro-inflammatory factor release, thus, should be avoided. The optimal hypothermic temperature of CPB should be determined based on patient clinical characteristics and surgery type.

Comparison of Coagulation Parameters, Anticoagulation, and Need for Transfusion in Patients on Interventional Lung Assist or Veno-Venous Extracorporeal Membrane Oxygenation

Clinical data on anticoagulation needs of modern extracorporeal membrane oxygenation (ECMO) and its impact on coagulation are scarce. Therefore, we analyzed coagulation-related parameters, need for transfusion, and management of anticoagulation in adult patients with severe acute respiratory failure during treatment with either pumpless interventional lung assist (iLA) or veno-venous ECMO (vv-ECMO). Sixty-three patients treated with iLA and 192 patients treated with vv-ECMO at Regensburg University Hospital between January 2005 and May 2011 were analyzed. Data related to anticoagulation, transfusion, and coagulation parameters were collected prospectively by the Regensburg ECMO registry. Except for a higher, sequential organ failure assessment (SOFA) score in the ECMO group (12 [9-15] vs. 11 [7-14], P = 0.007), a better oxygenation, and a lower dosage of vasopressors in the iLA patients, both groups had similar baseline characteristics. No difference was noted in terms of outcome and overall transfusion requirements. Factors of the plasmatic coagulation system were only marginally altered over time and did not differ between groups. Platelet counts in ECMO-treated patients, but not in those treated with iLA, dropped significantly during extracorporeal support. A more intense systemic anticoagulation with a mean activated partial thromboplastin time (aPTT) > 53 s led to a higher need for transfusions compared with the group with a mean aPTT < 53 s, whereas the average durability of membrane oxygenators was not affected. Need for red blood cell (RBC) transfusion was highest in patients with extrapulmonary sepsis (257 mL/day), and was significantly lower in primary pulmonary adult respiratory distress syndrome (ARDS) (102 mL/day). Overall, 110 (0-274) mL RBC was transfused in the ECMO group versus 146 (41-227) mL in the iLA group per day on support. The impact of modern iLA and ECMO systems on coagulation allows comparatively safe long-term treatment of adult patients with acute respiratory failure. A moderate systemic anticoagulation seems to be sufficient. Importantly, platelets are more affected by vv-ECMO compared with pumpless iLA.

Development and hemocompatibility testing of nitric oxide releasing polymers using a rabbit model of thrombogenicity

Hemocompatibility is the goal for any biomaterial contained in extracorporeal life supporting medical devices. The hallmarks for hemocompatibility include nonthrombogenicity, platelet preservation, and maintained platelet function. Both in vitro and in vivo assays testing for compatibility of the blood/biomaterial interface have been used over the last several decades to ascertain if the biomaterial used in medical tubing and devices will require systemic anticoagulation for viability. Over the last 50 years systemic anticoagulation with heparin has been the gold standard in maintaining effective extracorporeal life supporting. However, the biomaterial that maintains effective ECLS without the use of any systemic anticoagulant has remained elusive. In this review, the in vivo 4-h rabbit thrombogenicity model genesis will be described with emphasis on biomaterials that may require no systemic anticoagulation for extracorporeal life supporting longevity. These novel biomaterials may improve extracorporeal circulation hemocompatibility by preserving near resting physiology of the major blood components, the platelets and monocytes. The rabbit extracorporeal circulation model provides a complete assessment of biomaterial interactions with the intrinsic coagulation players, the circulating platelet and monocytes. This total picture of blood/biomaterial interaction suggests that this rabbit thrombogenicity model could provide a standardization for biomaterial hemocompatibility testing.

Hypothermic cardiopulmonary bypass as a determinant of late thrombocytopenia following cardiac operations in pediatric patients

BACKGROUND

Thrombocytopenia after cardiac operations is a common event in both adult and pediatric patients. Late thrombocytopenia (LTCP) is a less common event that is still without a well-recognized cause. This study explores the role of heparin-induced thrombocytopenia (HIT) and other factors (complexity of the operation, temperature management, and drug use) in determining LTCP.

METHODS

We conducted an observational study of 63 consecutive patients aged <36 months operated with or without cardiopulmonary bypass (CPB). LTCP was defined as a platelet count <100,000 cells/microl or <50% of the pre-operative count at any point in time between post-operative days 5 and 10. A diagnostic test for heparin-platelet factor 4 (PF4) antibodies was performed in patients with LTCP. Other pre- and post-operative factors were investigated for their association with LTCP.

RESULTS

LTCP occurred in 15 (24%) patients. No patient had positive heparin-PF4 antibodies. The lowest temperature on CPB was an independent predictor of LTCP, with a cut-off value at 29 degrees C (sensitivity 80%, specificity 70%). Other factors associated with LTCP were prolonged post-operative use of unfractionated heparin and milrinone. LTCP was associated with increased post-operative morbidity.

CONCLUSION

LTCP was related to a combination of factors (operation severity, degree of hypothermia during CPB, prolonged use of unfractionated heparin, and milrinone). The individual contribution of each factor seems difficult to establish. However, the degree of hypothermia during CPB and drug-associated effects were identified. HIT could be excluded in all cases.

Platelet Function Changes in Different Cardiac Surgery Subgroups as Evaluated with an Innovative Technology

Objectives

During cardiac surgery, platelets undergo substantial changes. The purpose of this study was to assess platelet function and compare these changes between different cardiac operations using an innovative technology.

Methods

Perioperative platelet function was evaluated by the Impact test [cone and plate(let) analyzer (CPA)]. The Impact test yields 2 parameters for platelet function: average size (AS, the mean size of the platelet aggregates) and surface coverage (SC, the percentage of the surface covered by the platelet aggregates), which correspond to platelet aggregation and adhesion. The study groups were compared for platelet function results in various surgery stages and correlation with bleeding.

Results

A significant decrease in surface coverage was detected on establishment of cardiopulmonary bypass, with an increase up to preoperative values at the end of the surgery in all groups. In contrast to operations performed on bypass, in patients operated without cardiopulmonary bypass, the postoperative AS and SC were higher than the preoperative values, 30.4 ± 8.1 μmol2 versus 23.3 ± 6.9 μmol2, P = 0.02 in AS, and 7.6 ± 3.6% versus 5.2 ± 1.8%, P = 0.04 in SC Preoperative AS and SC were the only parameters significantly (P = 0.01) and linearly (r = 0.6) related to postoperative bleeding.

Conclusions

Preoperative platelet function, as evaluated by the CPA, is an independent risk factor determining postoperative bleeding. The off-pump patients presented an increased platelet function at the end of surgery, a finding that can imply a higher risk of thrombosis. The impact test appears to be a useful tool to determine perioperative platelet function and help in prediction of postoperative bleeding.

[Neurological complications in cardiac surgery post-operative period]

The incidence of neurological complications after cardiac surgery continues to be elevated, although this is variable in the different studies published, fundamentally because of the different populations studied and the different definitions of neurological dysfunction. The etiology of these alterations is attributed to a multifactorial origin, aortic artherosclerosis, cerebral hypoperfusion and inflammatory phenomenon secondary to the technique. This review arises from the recognition of the personal, economic, and socio-health care repercussion entailed by these complications, with high rates of mortality and morbidity recorded, and it tries to give an objective view of the current literature on the subject. Having knowledge of the risk markers and understanding the pathogenesis is important to try to plan strategies that may minimize the appearance and development of these complications and contribute to the decrease of their serious consequences. The data and the experience obtained by our group are shown at the end of the review.

Platelet Function Changes as Monitored by Cone and Plate(let) Analyzer during Beating Heart Surgery

BACKGROUND

Off-pump coronary artery bypass (OPCAB) is believed to reduce cardiopulmonary bypass (CPB)-related complications, including platelet damage. A hypercoagulable state instead of coagulopathy has been reported following OPCAB surgeries due to CPB. Whether platelet function is changed when the injurious effect of CPB is eliminated was investigated.

METHODS

Platelet function was determined with the cone and plate(let) analyzer (CPA) method. The 2 parameters, average size (AS) and surface coverage (SC) of platelet aggregates, were measured with the CPA method to assess platelet aggregation and adhesion. These parameters were evaluated, and their values were compared at several stages of OPCAB surgery. The correlations of postoperative bleeding with platelet function at different stages of the surgery and with other factors, such as platelet count, hematocrit, and transfusions, were studied.

RESULTS

Both AS and SC increased during several stages of the operation, and postoperative values (mean +/- SD) were significantly higher than preoperative values (30.4 +/- 8.1 microm 2 versus 23.3 +/- 6.9 microm 2 for AS [ P =.02] and 7.6% +/- 3.6% versus 5.2% +/- 1.8% for SC [ P =.04]). The mean total bleeding volume was 875 micro 415 mL. Preoperative AS and SC were the only parameters significantly ( P =.01) and linearly ( r = 0.7) related to postoperative bleeding.

CONCLUSIONS

An increased platelet function, as determined by the CPA method, is found following OPCAB surgery. This phenomenon is probably at least partially responsible for the thrombogenic state after OPCAB surgery. Lack of platelet injury attributed to CPB may divert the system toward a more thrombogenic state. Preoperative platelet function, as evaluated by the CPA method, is an independent risk factor determining postoperative bleeding.

Beneficial effect of aspirin on renal function post-cardiopulmonary bypass

Urine thromboxane, plasma creatinine, and creatinine clearance were determined perioperatively in 20 patients undergoing coronary bypass surgery. Ten patients took aspirin until the day of surgery, and 10 discontinued aspirin at least one week before surgery. A significant increase in urine thromboxane following establishment of cardiopulmonary bypass was observed only in the control group. Plasma creatinine increased in the control group on the 1st postoperative day (from 81.9 +/- 13.2 to 97.6 +/- 13.2 micromol.L(-1), p = 0.02) and decreased next day to the preoperative level (82.7 +/- 9 micromol.L(-1), p = 0.03). In the aspirin group, creatinine remained unchanged on the 1st postoperative day (89.4 +/- 14.2 vs. 87.2 +/- 7.7 micromol.L(-1), p = 0.6), and increased significantly on the 2nd day (101.4 +/- 8.5 micromol.L(-1), p = 0.01). The aspirin group had higher creatinine levels (p < 0.0001) and lower creatinine clearance (60.2 +/- 16.5 vs. 82 +/- 25.7 mL.min(-1), p < 0.0001) than the control group on the 2nd postoperative day. A significant positive correlation was seen between urine thromboxane and creatinine on day 2 in both groups (r = 0.6). Aspirin administrated before coronary surgery may have a beneficial effect on renal function, probably mediated by its antiplatelet activity and thromboxane inhibition.

Exposure of procoagulant phospholipids on the surface of platelets in patients undergoing cardiopulmonary bypass using non-coated and heparin-coated extracorporeal circuits

Cardiopulmonary bypass (CPB) is associated with a generalized hemostatic defect, in which platelet dysfunction seems to play a central role. The present study was designed to elucidate whether the potential procoagulant activity of platelets, detected as annexin V binding, was altered during coronary bypass surgery, using non-coated and heparin-coated extracorporeal circuits. Thirty patients undergoing elective coronary artery bypass grafting were prospectively randomized using either a standard untreated extracorporeal circuit (n = 15) or a heparin-treated extracorporeal circuit (n=15). Besides measurement of the procoagulant phospholipid activity, the mediastinal blood loss after surgery, and the blood transfusion requirements were also monitored. CPB induced a decrease in the percentage of activated platelets in whole blood, manifest directly after start of CPB, which was significantly attenuated using a non-treated system. Postoperatively, the percentage of activated platelets recovered in both systems, reaching a point of significance 24 hours after the operation, compared to the values 2 hours after the operation. The differences among the groups for mediastinal blood loss during the first 2 and 24 postoperative hours coincided with the differences in procoagulant phospholipid activity. Furthermore, there was no statistical difference among the groups for blood transfusion requirements. The platelets in both groups showed a significantly lower ability to generate ionomycin-induced procoagulant activity after blood-material interaction when compared to the baseline values. These observations are compatible with the notion that during CPB, irrespective of the heparin coating, platelets become modestly activated.

Attenuation of neurologic injury during cardiac surgery

Neurologic injury after cardiac surgery can be divided into type I, including clinically apparent stroke, seizures stupor, or coma, and much more occurring type II injury, including intellectual deterioration, memory deficit, or seizures. Cerebral embolization is demonstrably etiologic in many such cases, and several new aortic cannulas are being introduced that are aimed at capturing or diverting potential cerebral emboli. No outcome data are yet available. Several potentially cerebroprotective pharmacologic therapies including thiopental, propofol, and nimodipine, have been assessed clinically but, generally, the results have been poor. Meta-analysis of the large North American aprotinin database of prospective, randomized, placebo-controlled clinical trials is suggestive of a cerebroprotective potential associated with high-dose aprotinin administration.

Veno-venous bypass in liver transplantation: heparin-coated perfusion circuits reduce the activation of humoral defense systems in an in vitro model

We studied the effects of bypass circuit surface heparinization on kallikrein-kinin, coagulation, fibrinolytic and complement activation in a closed model system for simulating veno-venous bypass (WBP) in orthotopic liver transplantation (OLT). The circuits were identical to those in routine use during clinical OLT in our institution. Fresh whole human blood diluted 1:2 with Ringer's acetate was circulated at a non-pulsatile flow (2 l/min) and at a constant temperature (37.5 degrees C) for 12 h. In 10 experiments, the entire inner surface of the circuits was coated with end-point attached heparin (HC). In the remaining 10, non-treated PVC tubing was used (NC). Components of the plasma kallikrein-kinin, coagulation, fibrinolytic and complement systems were analyzed using functional techniques (chromogenic peptide substrate assays) and enzyme immunoassays at baseline, 3 and 12 h. Significant activation of the initial (C3bc) and terminal (TCC) components of the complement system were found in both the NC and HC groups after 3 and 12 h: C3bc: NC: baseline = 4 (3.5-7.7), 3 h = 17.3* (12.5-27), 12h = 31* (17.7-63.6), HC: baseline = 4.9 (3.2-6.8), 3h = 9* (6-14.4), 12h = 13.7* (7.4-18.1). TCC: NC: baseline = 0.4 (0.2-0.6), 3h = 5*(0.8-11.9), 12 h: 13.1* (4.2-25.7). HC: baseline = 0.5 (0.1-0.6), 3 h = 0.6* (0.1-0.8), 12 h = 1.2* (0.3-2) AU/ml; median and range (*: p < 0.05). The C3bc and TCC concentrations were significantly higher in the NC group at 3 and 12 h, compared to the HC group: C3bc (NC vs. HC group): 3 h, p < 0.001; 12 h, p < 0.001. TCC (NC vs. HC group): 3h, p < 0.001; 12 h, p < 0.001. Significant increases in the values of thrombin-antithrombin complexes (p = 0.003), prothrombin fragment 1 + 2 (p = 0.006) and plasmin-alpha2-antiplasmin complexes (p = 0.016) were found in the non-coated group, but not in the heparin-coated group during the observation period, showing that the coagulation and fibrinolytic systems were activated in the non-coated circuits. We conclude that heparin-coating of the internal surface of the extracorporeal perfusion circuit used for WBP reduces activation of the plasma cascade systems in a closed venous system in vitro.

Effect of hemofiltrated whole blood pump priming on hemodynamics and respiratory function after the arterial switch operation in neonates

BACKGROUND

Primed blood might have some deleterious effects on neonates during cardiopulmonary bypass (CPB) due to unbalanced electrolytes and inflammatory mediators. We hemofiltrated pump-primed blood before CPB to reduce inflammatory mediators and to adjust pH and the concentrations of electrolytes. The current study investigated the effects of hemofiltrated whole blood priming on hemodynamics and respiratory function after CPB in neonates.

METHODS

Patients who underwent the arterial switch operation in the neonatal period for transposition of the great arteries with intact ventricular septum were chosen for this study. Seventeen patients underwent CPB with hemofiltrated blood priming (group HF) and 23 patients underwent CPB with nonhemofiltrated blood priming (group N). The concentrations of electrolytes and bradykinin and high molecular weight kininogen of the primed blood before and after hemofiltration were measured. At 4 hours after completion of CPB, the left ventricular percent fractional shortening, and the relation between the mean velocity of shortening and the end-systolic wall stress (stress velocity index), were measured by echocardiogram in 7 patients in group HF and 6 patients in group N. Alveolar--arterial oxygen tension difference (AaDO2) and respiratory index (AaDO2 divided by arterial oxygen tension) were measured at several points for 48 hours after CPB in all patients.

RESULTS

Hemofiltration of the primed blood maintained electrolytes within a physiologic level and significantly reduced the concentrations of bradykinin (5,649 +/- 1,353 pg/mL versus 510 +/- 35 pg/mL, p < 0.05) and high molecular weight kininogen (52.7% +/- 3.2% versus 40.1% +/- 3.0% of normal plasma value, p < 0.05). The percent of fractional shortening at 4 hours after completion of CPB was significantly higher in group HF (n = 7) than in group N (n = 6) (22.0% +/- 0.7% versus 16.0% +/- 0.4%, p < 0.01). There was also a trend toward better stress velocity index in group HF than in group N (0.81 +/- 0.81 versus -2.17 +/- 0.45, p = 0.09). AaDO2 and respiratory index were significantly lower in group HF than in group N for 48 hours after CPB, respectively (p < 0.05).

CONCLUSIONS

Hemofiltrated fresh whole blood used for CPB priming attenuated cardiac impairment at early reperfusion periods and reduced pulmonary dysfunction in neonates with transposition of the great arteries with intact ventricular septum. This therapeutic strategy may have an advantage in preventing lung and heart dysfunction in pediatric patients who need CPB priming with blood.

SMA circuits reduce platelet consumption and platelet factor release during cardiac surgery

BACKGROUND

Platelet count and function are particularly damaged by cardiopulmonary bypass (CPB). This study evaluated the effects of a novel CPB circuit in terms of platelet count and activation, and postoperative need for blood products.

METHODS

One hundred patients undergoing coronary grafting were randomized in two groups: control group (n = 50) and test group (n = 50, surface modifying additives circuit, SMA group). Blood samples were taken before, during, and after CPB. Postoperative blood loss, number of transfused blood products, and postoperative variables were recorded.

RESULTS

The platelet count decreased less in the SMA group compared to the control group (end of CPB: respectively, 165 +/- 9 x 10(3)/mm3 vs 137 +/- 8 x 10(3)/mm3; p < 0.01). This was paralleled by a reduction in beta-thromboglobulin plasma levels in the SMA group. There was a trend to decreased blood loss in the SMA group, but the difference was significant only in patients taking aspirin preoperatively (p < 0.05). In the SMA group nearly 50% less fresh frozen plasma and platelet units were administered (p < 0.01). No operative deaths were observed.

CONCLUSIONS

The use of circuits with surface additives is clinically safe, preserves platelet levels, and attenuates platelet activation. This may lead to a reduced need for blood products.

Pulmonary artery perfusion with protective solution reduces lung injury after cardiopulmonary bypass

BACKGROUND

The inflammatory response and higher temperature of lung tissue during cardiopulmonary bypass can result in lung injury. This study was to evaluate the protective effect of pulmonary perfusion with hypothermic antiinflammatory solution on lung function after cardiopulmonary bypass.

METHODS

Twelve adult mongrel dogs were randomly divided into two groups. The procedure was carried out through a midline sternotomy, cardiopulmonary bypass was established using cannulas placed in the ascending aorta, superior vena cava, and right atrium near the entrance of the inferior vena cava. After the ascending aorta was clamped and cardioplegic solution infused, the right lung was perfused through a cannula placed in the right pulmonary artery with 4 degrees C lactated Ringer's solution in the control group (n = 6) and with 4 degrees C protective solution in the antiinflammation group (n = 6). Antiinflammatory solution consisted of anisodamine, L-arginine, aprotinin, glucose-insulin-potassium, and phosphate buffer. Plasma malondialdehyde, white blood cell counts, and lung function were measured at different time point before and after cardiopulmonary bypass; lung biopsies were also taken.

RESULTS

Peak airway pressure increased dramatically in the control group after cardiopulmonary bypass when compared with the antiinflammation group at four different time points (24 +/- 1, 25 +/- 2, 26 +/- 2, 27 +/- 2 cm H2O versus 17 +/- 2, 18 +/- 1, 17 +/- 1, 18 +/- 1 cm H2O; all p < 0.01). Pulmonary vascular resistance increased significantly in the control group than in the antiinflammation group at 5 and 60 minutes after cardiopulmonary bypass (1,282 +/- 62 dynes x s x cm(-5) versus 845 +/- 86 dynes x s x cm(-5) and 1,269 +/- 124 dynes x s x cm(-5) versus 852 +/- 149 dynes x s x cm(-5), p < 0.05). Right pulmonary venous oxygen tension (PvO2) in the antiinflammation group was higher than in the control group at 60 minutes after cardiopulmonary bypass (628 +/- 33.3 mm Hg versus 393 +/- 85.9 mm Hg, p < 0.05). The ratio of white blood cells in the right atrial and the right pulmonary venous blood was lower in the antiinflammation group than in the control group at 5 minutes after the clamp was removed (p < 0.05). Malondialdehyde were lower in the antiinflammation group at 5 and 90 minutes after the clamp was removed (p < 0.01 and p < 0.05, respectively). Histologic examination revealed that the left lung from both groups had marked intraalveolar edema and abundant intraalveolar neutrophils, whereas the right lung in the control group showed moderate injury and the antiinflammation group had normal pulmonary parenchyma.

CONCLUSIONS

Pulmonary artery perfusion using hypothermic protective solution can reduce lung injury after cardiopulmonary bypass.

Coagulation and anticoagulation in extracorporeal membrane oxygenation

The hemostatic system poses a major problem in extracorporeal membrane oxygenation (ECMO). The foreign surface in the extracorporeal circuit activates platelets and the clotting system. To avoid loss of platelets and activation of the clotting system, anticoagulation is necessary. In addition, in many patients on ECMO, preexisting clotting disorders are present. Therefore, bleeding and/or thrombosis are frequent complications in ECMO patients that require specific treatment and may even necessitate termination of ECMO. Most ECMO centers use heparin for anticoagulation and the activated clotting time (ACT) for monitoring. Reduction of problems with hemostasis may be obtained with less thrombogenic surfaces, new anticoagulants with a short half-life, platelet inhibitors, protease inhibitors, or selective anticoagulation in the extracorporeal circuit. While there will probably never be a complete nonthrombogenic surface available and all anticoagulants will have some risk of bleeding, improvement can be obtained by a combination of measures including better surfaces, more sophisticated anticoagulation regimens, and close laboratory monitoring.

Heparin-Bonded Circuits Decrease Thromboembolic Complications and Improve Outcomes in Patients Undergoing Coronary Artery Bypass Graft Surgery

Two prospective, randomized studies were performed to definitively evaluate the safety and efficacy of heparin- bonded circuits in patients undergoing primary coro nary artery bypass graft surgery and to clarify the effect of anticoagulation protocol on clinical and neurologic outcomes. These studies showed that the use of heparin- bonded circuits with lower anticoagulation results in markedly improved clinical outcomes in patients under going primary coronary artery bypass graft surgery with a reduction in both clinical and microscopic throm boembolic risks. The mechanisms by which heparin- bonded circuits affect clinical and neurologic outcomes are explored.

Vascular endothelium viability and function after total cardiopulmonary bypass in neonatal piglets

Endothelium dysfunction with severe pulmonary hypertension may occur after total cardiopulmonary bypass (CPB) in infants as a result of a widespread inflammatory response. The aim of this study was to separate out the effects of lung ischemia-reperfusion from membrane oxygenator-induced activation of leukocytes on the function and viability of the pulmonary and systemic endothelia in neonatal piglets submitted to 90-min total CPB followed by 60-min reperfusion or in sham animals. Hemodynamics, gas exchange, endothelial-dependent relaxation in pulmonary and femoral arteries, and lung and skeletal muscle myeloperoxidase activity were assessed before, during, and after CPB, i.e., after reperfusion. Pulmonary and aortic endothelial cells and circulating leukocytes were harvested to assess reperfusion-induced changes in endothelial cells' viability and proliferation, and leukocyte-endothelial cell adhesion and cytotoxicity. Gas exchange worsened after reperfusion with pulmonary hypertension, increase in lung but not skeletal myeloperoxidase, and reduction of endothelial-dependent relaxation in pulmonary but not femoral arteries. After reperfusion, viabilities of pulmonary and aortic endothelial cells were reduced to 50%, endothelial cell growths were faster in pulmonary arteries than aorta, and leukocyte-pulmonary endothelial cell adhesion and cytotoxicity increased. These results suggest that in total CPB lung ischemia-reperfusion aggravates the inflammatory response and predisposes the lung endothelium to leukocyte-mediated injury.

Changes in leucocyte counts and soluble intercellular adhesion molecule-1 and E-selectin during cardiopulmonary bypass in children

A consequence of cardiopulmonary bypass (CPB) in young children is postoperative capillary leak and associated pulmonary dysfunction. Neutrophils sequester in the lungs and may contribute to functional endothelial damage. The endothelial adhesion molecules, E-selectin and intercellular adhesion molecule-1 (ICAM-1), mediate sequential steps in adhesion by binding to leucocyte ligands. Circulating forms of these proteins have been identified. We studied changes in the plasma concentrations of soluble E-selectin and soluble ICAM-1 using fixed phase immunoassays, and associated leucocyte counts in 10 paediatric patients undergoing CPB. Concentrations of soluble L-selectin and soluble ICAM-1 consistently fell during CPB from preoperative levels of 89 +/- 17 ng/ml (mean +/- 2SEM) and 218 + 61 ng/ml, respectively, to 39 +/- 7 ng/ml and 84 +/- 24 ng/ml, respectively at the beginning of maximum hypothermia. The haemodilution that occurred during CPB largely explained this fall, but not the more marked decrease in white cell counts that also occurred over this period (6.7 +/- 1.1 to 1.7 +/- 0.5 x 10(9)/l) which may reflect increased leucocyte sequestration. By 24 h postoperatively, levels of both soluble adhesion molecules approached preoperative concentrations, as did lymphocyte counts. In marked contrast, neutrophil counts rose appreciably towards the end of CPB, and continued to rise to a maximum of 10.9 +/- 3.1 x 10(9)/l during the immediate postoperative period and remained at these elevated levels 24 h later. Major consistent changes in circulating leucocyte numbers which occur early in cardiopulmonary bypass may reflect changes in adhesion to the endothelium and consequent sequestration. Alterations in the levels of soluble adhesion proteins may influence these processes.

Aprotinin complements heparin bonding in an in vitro model of cardiopulmonary bypass

The relative contribution of full-dose aprotinin, used with heparin-bonded surfaces, to contact activation during cardiopulmonary bypass was examined. In vitro Carmeda-bonded cardiopulmonary bypass circuits were perfused with whole blood anticoagulated with heparin (3.3 U/ml). Aprotinin (300 kIU/ml) was added to the circuits of one set of experiments. Samples were taken prior to perfusion and at 30, 60, 120 and 360 min. The activated coagulation time was extended in the aprotinin experiments, significantly at 30 min (P=0.003) and 120 min (P=0.001). Thrombin-antithrombin complexes and prothrombin fragment F1+2 were both higher in the non-aprotinin experiments at 120 min (P=0.02 each) and 360 min (P=0.005 and 0.001, respectively). Plasma leucocyte elastase was raised in the non-aprotinin experiments in comparison to the aprotinin experiments at each timepoint (30 min, P=0.04; 60 min, P=0.006; 120 min, P=0.001; 360 min, P=0.0001), as was interleukin-8 at 120 min (P=0.05) and 360 min (P=0.0001). No differences were found for the platelet activation marker P-selectin. Platelet and white blood cell counts fell significantly in the non-aprotinin experiments compared with the aprotinin experiments at 360 min (P=0.05 and 0.03, respectively). It would appear that the use of aprotinin has additional haemostatic beneficial effects to those found with heparin-bonded circuits in terms of effects on contact activation and inflammation.

A Comparison of Heparin and New Anticoagulants for Cardiopulmonary Bypass Surgery

Heparin is still the major anticoagulant of choice during CPB, but it may cause thrombocytopenia and severe bleeding in patients. In light of these complications, the devel opment of new anticoagulant drugs seemed to be necessary for these patients. Many experimental studies focused on r-hirudin, which presented a less hemorrhagic effect than heparin. How ever, neither antagonist has been shown to reverse this effect.

Intercellular adhesion molecule-1 regulation in the canine lung after cardiopulmonary bypass

OBJECTIVE(S)

Neutrophil sequestration in the lung after cardiopulmonary bypass has been shown to be dependent on the adhesion molecule CD18. Thus we sought to determine whether endothelial expression of intercellular adhesion molecule-1 (a ligand for CD18) in pulmonary capillaries mediates neutrophil adhesion in this setting.

METHODS

Seven adult mongrel dogs underwent 90 minutes of hypothermic cardiopulmonary bypass with 60 minutes of cardioplegic arrest. After warming, dogs were reperfused for up to 9 hours and lung biopsy specimens were obtained. Lung tissue was examined by Northern and Western blot analysis and by immunohistologic methods. Three sham-operated dogs served as time-matched controls.

RESULTS

Northern blots demonstrated increased expression of intercellular adhesion molecule-1 messenger ribonucleic acid within 5 minutes of cessation of bypass (or approximately 30 minutes after aortic crossclamp release), which persisted at 9 hours of recovery and was not present in controls. Western blots showed intercellular adhesion molecule-1 protein expression before bypass but a measurable increase in intercellular adhesion molecule-1 protein in four of seven dogs in the bypass group by the ninth hour of recovery. Pulmonary neutrophil accumulation 9 hours after cardiopulmonary bypass was greater in those dogs with an increased intercellular adhesion molecule-1 protein expression. Immunoelectron microscopy demonstrated the pulmonary capillary endothelium capable of increased intercellular adhesion molecule-1 protein expression at the 9-hour time point.

CONCLUSIONS

Cardiopulmonary bypass resulted in intercellular adhesion molecule-1 induction in the canine lung during recovery. An increased expression of intercellular adhesion molecule-1 protein in the lung was associated with an increased accumulation of neutrophils in affected animals. Thus intercellular adhesion molecule-1 expression may serve as a mechanism that predisposes the lungs to inflammatory cell-mediated injury postoperatively.

Neutrophil adhesion molecule expression during cardiopulmonary bypass: a comparative study of roller and centrifugal pumps

The purpose of this study was to determine whether adhesion molecules and markers of cell activation were preferentially increased on blood neutrophils during cardiopulmonary bypass (CPB) and whether such effects were influenced by the use of a roller pump or a centrifugal pump. Forty-six patients undergoing open heart surgery were randomly allocated into either the roller or centrifugal groups. Blood (1 ml volumes) was removed from arterial and venous lines immediately before and 1 h after the start of bypass. Whole blood samples were immunolabelled and flow cytometry used to measure the distribution and expression of the adhesion molecules CD11b, CD18, CD62L on neutrophils, monocytes and lymphocytes, in addition to CD64 on neutrophils and monocytes, and CD14 on monocytes. The expression of CD11b was significantly enhanced on neutrophils in arterial and venous samples from both the roller pump (mean 84% and 100% increase, respectively; p < 0.001) and centrifugal pump (mean 74% and 73% increase, respectively; p < 0.001) groups. Neutrophil L-selectin expression increased to a small but significant extent in arterial and venous samples from the centrifugal pump group (mean 16% increase; p < 0.001) and in venous samples from the roller pump group (mean 10% increase; p < 0.01). Neither the percentage of neutrophils bearing CD11b/CD18, CD62L and CD64, nor the expression of adhesion molecules on lymphocytes and monocytes were modified by 1 h of bypass. These results suggest that patients subjected to CPB with roller or centrifugal pumps are equally at risk to neutrophil activation that could lead to increased interaction of these cells with blood vessel walls.

Increased plasma concentrations of serum amyloid A: an indicator of the acute-phase response after cardiopulmonary bypass

OBJECTIVES

To assess the expression of mixed and hepatic venous serum amyloid A (SAA) concentrations and its relationship to plasma concentrations of C-reactive protein, interleukin-6 (IL-6), and endotoxin during and after cardiopulmonary bypass (CPB).

DESIGN

Prospective, consecutive sample with repeated measurements.

SETTING

Surgical intensive care unit (ICU) in a university hospital.

PATIENTS

Twenty patients who underwent elective coronary bypass grafting.

INTERVENTIONS

A radial artery catheter, pulmonary artery catheter, and right hepatic vein catheter were inserted. Blood samples were collected to determine the different mediators, lactate concentrations, and oxygen saturations.

MEASUREMENTS AND MAIN RESULTS

After induction of anesthesia, baseline values were obtained and the following parameters were determined 20 mins after onset of CPB, 20 mins after termination of CPB, at admission to the ICU, and 6, 8, 12, and 24 hrs later: hemodynamics, body core temperature, hepatic venous oxygen saturation, and mixed and hepatic venous lactate, endotoxin, interleukin (IL)-6, C-reactive protein (CRP), and SAA concentrations. Endotoxin and IL-6 plasma concentrations increased during CPB, peaked 6 hrs after admission to the ICU (endotoxin: 23.1 +/- 6.2 pg/mL; IL-6: 646 +/- 104 pg/mL), and decreased thereafter; SAA and CRP concentrations began to increase after 6 and 8 hrs, respectively, with the highest concentrations reached 24 hrs postoperatively (CRP: 14 +/- 3.6 mg/L; SAA: 668 +/- 114 micrograms/mL). Lactate concentrations began to increase 20 mins after CPB, and continued to increase until 12 hrs postoperatively. There were no significant differences between mixed and hepatic venous values of endotoxin, IL-6, CRP, SAA, and lactate (p < .05). Body core temperature, which was < 37.5 degrees C before surgery for all patients, increased 6 hrs after admission to the ICU and peaked 12 hrs postoperatively (38.3 +/- 1.1 degrees C). Hepatic venous oxygen saturation did not change. Correlations were obtained between IL-6 values and heart rate (r2 = .20; p < .005), and endotoxin concentrations and systemic vascular resistance (r2 = .18; p < .001). Body core temperature correlated significantly closer with SAA (r2 = .52; p < .0001) values than with IL-6 (r2 = .27; p < .0001) or CRP (r2 = .16; p < .001) values (p < .05).

CONCLUSIONS

SAA is an additional and sensitive marker of the acute-phase response following CPB; the increase in SAA concentrations parallels the temporary increase in body core temperature and is preceded by endotoxemia and IL-6 secretion.

Cell activation and thrombin generation in heparin bonded cardiopulmonary bypass circuits using a novel in vitro model

OBJECTIVE

It is generally agreed that when the blood contact surfaces of a cardiopulmonary bypass circuit are treated with a layer of heparin molecules the activation of the humoral pathways is attenuated. However, there is still debate as to whether heparin-bonded circuits reduce thrombin generation. This study aims to examine the effects of immobilized heparin on cell activation and thrombin generation in a novel, well controlled model of cardiopulmonary bypass.

METHODS

The model used consisted of a heparin-bonded and a non-bonded cardiopulmonary bypass circuit perfused in tandem with the same unit of fresh heparinized (3.3 U/ml) human blood for a period of 6 h. Samples were taken for analysis from the bag just prior to perfusion and at 30, 60, 120 and 360 min of perfusion. Whole blood was used to analyse platelet and white blood cell count, haematocrit and activated coagulation time. Plasma samples were prepared for batch analysis of the cell activation markers p-selectin, elastase and interleukin-8, and the thrombin generation markers thrombin-antithrombin and prothrombin fragment F1 + 2. A sample of tubing was taken from each circuit at the end of the perfusion and prepared for visualization by scanning electron microscopy.

RESULTS

Platelet counts were significantly reduced in the non-bonded circuits compared with the heparin-bonded circuits at 30 (22 versus 200 x 10(9)/L P < 0.01), 60 (26 versus 193 x 10(9)/L P < 0.01) and 120 min (28 versus 193 x 10(9)/L P < 0.01) as were white blood cell counts at 30(1.5 versus 2.7 x 10(9)/L P < 0.01), 60 (0.9 versus 2.4 x 10(9)/L P < 0.01), 120 (0.9 versus 1.8 x 10(9)/L P < 0.01) and 360 min (0.4 versus 0.9 x 10(9)/L P < 0.05). The concentration of p-selectin was found to be significantly higher in the non-bonded circuits than in the heparin-bonded circuits at 30 (37 versus 29 ng/ml P < 0.01), 60 (37 versus 28 ng/ml P < 0.01). 120 (42 versus 27 ng/ml P < 0.01) and at 360 min (72 versus 46 ng/ml P < 0.01). Elastase was elevated in the non-bonded circuits at 30 (570 versus 145 micrograms/l P < 0.01), 60 (646 versus 278 micrograms/l P < 0.01) and 120 min (613 versus 403 micrograms/l P < 0.05) and interleukin-8 at 120 (705 versus 520 pg/ml P < 0.05) and 360 min (11326 versus 9910 pg/ml P < 0.05). A similar picture was found for the thrombin generation markers. Thrombin-antithrombin complexes were raised in the non-bonded circuits compared with heparin-bonded circuits at 60 (24 versus 13 micrograms/l P < 0.05) and 120 min (46 versus 17 micrograms/l P < 0.05) as was prothrombin fragment F1 + 2 at 30 (1.1 versus 0.7 nmol/l P < 0.01), 60 (1.3 versus 0.7 nmol/l P < 0.01), 120 (1.8 versus 0.9 nmol/l P < 0.01) and 360 min (15.0 versus 13.6 nmol/l P < 0.05). Scanning electron microscopy revealed a greater amount of adherent material on the non-bonded surface relative to the heparin-bonded surface.

CONCLUSIONS

In a cardiopulmonary bypass circuit perfused with human blood the activation of platelets and white blood cells has been seen to be significantly reduced in the presence of a heparin-bonded surface. Thrombin generation due to contact activation of the intrinsic coagulation pathway is also reduced.

The inflammatory response to cardiopulmonary bypass

The inflammatory response to cardiopulmonary bypass is the product of a complex interplay of humoral and cellular components. Contact activation cascades, the complement system, and cytokines comprise the humoral elements and interact in such a way as to propagate their own cascades and to activate the cellular elements. Neutrophils and endothelial cells are the cellular components and become involved after their "activation" by the humoral mediators. Neutrophil-endothelial cell adherence is the initial step of the cellular inflammatory response and is promoted by the expression of specific adhesion molecules on the surfaces of both of these cells leading to the emigration of neutrophils into the extravascular space where they release toxins that damage surrounding tissues. The resulting organ dysfunction produces the clinical picture referred to as the "postperfusion syndrome." Strategies to attenuate this response include the administration of corticosteroids, aprotinin, and anticytokine monoclonal antibodies, as well as various modifications of the bypass circuit. The existence of multiple pathways to trigger this inflammatory response hampers efforts at its attenuation and leaves much investigation to be done as the quest to understand the body's inflammatory response to cardiopulmonary bypass continues.

Cardiopulmonary bypass and the inflammatory response: a role for serine protease inhibitors?

Cardiopulmonary bypass has been shown to activate various inflammatory cascades in the body, resulting in pathophysiological changes that may affect patient outcome after cardiac surgery. Many of these inflammatory cascades are enzyme mediated, involving serine proteases. This report reviews the mechanisms of bypass-mediated activation of the inflammatory cascades and outlines the role of serine protease inhibitors in ameliorating the consequences of the inflammatory response. Experimental data are reviewed on the action of aprotinin in inhibiting the intrinsic coagulation system and in limiting the contact activation of blood platelets and leukocytes. Also reviewed is the role of aprotinin in impacting the incidence of perioperative myocardial ischemia and the central nervous system dysfunction and stroke that are not infrequent complications of surgery with cardiopulmonary bypass.