Complement activation during cardiopulmonary bypass

We researched complement activation of fifteen patients who had open heart surgery and on ten patients who had closed heart surgery. Our results showed that the complement system was partially activated by the anaesthesia and partially by tissue damage. This activation was aggravated when plasma contacted the pump-oxygenator system, continued in the intensive-care unit and became normal in the 24th hour after the operation. Complement activation occurred both via the alternative and classical pathways but the alternative pathway was activated more than the classical with increase in bypass time. Pulmonary sequestration of leucocytes which occurred due to the complement activation and the complement derived inflammatory mediators could have contributed to the pathogenesis of the post-pump syndrome.     

Complement activation and lung permeability during cardiopulmonary bypass

Pulmonary dysfunction after cardiopulmonary bypass has been attributed to the damaging effects of complement activation on the lung. To further explore this phenomenon, we measured plasma levels of activated complement components (radioimmunoassay), assessed neutrophil n-formyl-methionyl-leucyl-phenylalanine (FMLP) receptor status (radioligand saturation binding assay), and quantified pulmonary epithelial permeability as radioaerosol lung clearance of technetium 99m-labeled diethylenetriamine pentaacetic acid in a series of 8 patients undergoing cardiopulmonary bypass. Significant elevations of plasma C3adesArg, C4adesArg, and C5adesArg levels were seen just after CPB, indicating activation of both the classic and alternate complement pathways. Neutrophil activation was evident as increased expression of neutrophil FMLP surface receptors after bypass. Despite the presence of complement and neutrophil activation, increased pulmonary epithelial permeability was not seen. These data support the hypothesis that complement and neutrophil activation during cardiopulmonary bypass is not associated with acute lung injury, at least not pulmonary epithelial injury. One can therefore infer that increased pulmonary epithelial permeability in patients at high risk for and experiencing sepsis-induced and trauma-induced adult respiratory distress syndrome may be due to factors other than complement and neutrophil activation.     

Peripheral blood monocyte activation during coronary artery bypass grafting with or without cardiopulmonary bypass

OBJECTIVE: The aim of this prospective, randomized study was to investigate the impact of coronary artery bypass grafting (CABG) on peripheral monocytes and to evaluate the additional effect of cardiopulmonary bypass (CPB). DESIGN: Twenty patients admitted for elective CABG were randomized to either on-pump (ONCAB, n = 9) or off-pump (OFFCAB, n = 11) surgery and blood samples were drawn before, during and 24 h after the operation. The total number of monocytes and the proportion of the more mature CD16+/CD14+ monocytes were measured. Expression of activation markers (CD11b, CD35 and CD62L) and oxidative burst were determined using flow cytometry on both resting and in vitro stimulated cells. Serum concentrations of soluble CD14 and monocytes/macrophage chemotactic protein 1 (MCP-1) were analysed. RESULTS: During surgery there was a selective decrease in the proportion of CD16+/CD14+ monocytes compared to total monocytes. These had returned to preoperative values 24 h after surgery while the total number of monocytes had increased more than 100%. Intracellular production of oxygen free radical H2O2 was increased in the ONCAB group during surgery compared to OFFCAB. Monocyte expression and in vitro mobilization of complement receptors, CD11b and CD35, were similar in both study groups during and after surgery as was the expression of CD62L. Serum levels of MCP-1 decreased during surgery as did soluble CD14, both with increased levels again the day after surgery. CONCLUSION: It is concluded that the circulating monocyte population is activated during and as a consequence of CABG. There were few apparent additional effects of CPB found in this study. In this setting the inflammation caused by the surgery procedure per se probably surpasses the impact of the CPB on circulating blood monocytes.     

Peripheral blood monocyte activation during coronary artery bypass grafting with or without cardiopulmonary bypass

Objective. The aim of this prospective, randomized study was to investigate the impact of coronary artery bypass grafting (CABG) on peripheral monocytes and to evaluate the additional effect of cardiopulmonary bypass (CPB).

Design. Twenty patients admitted for elective CABG were randomized to either on-pump (ONCAB, n=9) or off-pump (OFFCAB, n=11) surgery and blood samples were drawn before, during and 24 h after the operation. The total number of monocytes and the proportion of the more mature CD16⁺/CD14⁺ monocytes were measured. Expression of activation markers (CD11b, CD35 and CD62L) and oxidative burst were determined using flow cytometry on both resting and in vitro stimulated cells. Serum concentrations of soluble CD14 and monocytes/macrophage chemotactic protein 1 (MCP-1) were analysed.

Results. During surgery there was a selective decrease in the proportion of CD16⁺/CD14⁺ monocytes compared to total monocytes. These had returned to preoperative values 24 h after surgery while the total number of monocytes had increased more than 100%. Intracellular production of oxygen free radical H₂O₂ was increased in the ONCAB group during surgery compared to OFFCAB. Monocyte expression and in vitro mobilization of complement receptors, CD11b and CD35, were similar in both study groups during and after surgery as was the expression of CD62L. Serum levels of MCP-1 decreased during surgery as did soluble CD14, both with increased levels again the day after surgery.

Conclusion. It is concluded that the circulating monocyte population is activated during and as a consequence of CABG. There were few apparent additional effects of CPB found in this study. In this setting the inflammation caused by the surgery procedure per se probably surpasses the impact of the CPB on circulating blood monocytes.     

Complement activation during cardiopulmonary bypass: mechanism and prevention

The mechanism of complement activation during cardiopulmonary bypass was studied for the prevention. In ten patients undergoing open-heart procedures, the serum levels of complement fractions (C3, C4, and C3 activator) were measured by a single radial immune diffusion method. In four of ten patients, the plasma levels of C3a, C4a, and C5a fractions were studied by the radioimmunoassay 2 antibodies method. The serum levels of C3, C4, and C3 activator decreased after cardiopulmonary bypass. The plasma levels of C3a, C4a, and C5a increased after bypass. The lower level of C3 activator shows that C3 activator was not excessively produced during cardiopulmonary bypass. Therefore it can be thought that much C4b2a from classical pathway as well as C3a over-production localizing extra-corporeal circuits and little inhibitors on alternative pathway resulted in increased complement activation. The prevention should be done from these etiologies.     

Complement activation before, during and after cardiopulmonary bypass

Plasma levels of the complement parent molecules C3, C4, and factor B and their split products, C3d, C4d, and Ba were measured in 12 patients undergoing cardiopulmonary bypass for coronary artery surgery. Alternative and common complement pathway activation, demonstrated by statistically significant rising levels of Ba (P less than 0.05), and C3d (P less than 0.05) and by elevated Ba:B (P less than 0.05) and C3d:C3 (P less than 0.05) ratios were found before the institution of cardiopulmonary bypass but following heparin administration suggesting that heparin may itself initiate alternative pathway activation. In addition, significant depletion of parent complement components and elevation of split product concentrations was seen during bypass suggesting classical and alternate pathway activation (P less than 0.01). This study clarifies the pathways of complement activation during bypass and presents evidence that heparin administration may initially activate the complement cascade.     

Complement activation during cardiopulmonary bypass. Comparison of bubble and membrane oxygenators

A prospective randomized trial involving 91 patients undergoing cardiopulmonary bypass compared the effects of bubble oxygenators (with and without methylprednisolone sodium succinate) and membrane oxygenators on complement activation and transpulmonary sequestration of leukocytes. Patients were divided as follows: Group I, 30 patients, bubble oxygenator; Group II, 31 patients, bubble oxygenator and methylprednisolone sodium succinate (30 mg/kg); Group III, 30 patients, membrane oxygenator. In Group I, C3a increased from 323 +/- 171 ng/ml during cardiopulmonary bypass to 1,564 +/- 785 ng/ml at 25 minutes after bypass (p less than 0.0001). A significant decrease in C3a was found in Groups II and III compared to Group I (p less than 0.0001). C5a did not change significantly during cardiopulmonary bypass in any group. Reestablishment of pulmonary circulation at the end of bypass produced significant transpulmonary leukocyte sequestration in Group I; the median cell difference was 1,700/microliter. Transpulmonary sequestration was significantly (p less than 0.0001) less in Group II (median cell difference = 200/microliter) and in Group III (median cell difference = 400/microliter) than in Group I. We conclude that cardiopulmonary bypass with a bubble oxygenator alone initiates significantly (p less than 0.0001) more C3a activation and leukocyte sequestration than when methylprednisolone sodium succinate (30 mg/kg) is given 20 minutes before the start of cardiopulmonary bypass with a bubble oxygenator or when a silicone membrane oxygenator is used.     

Corticosteroids during operations using cardiopulmonary bypass

Although corticosteroids have been used for more than 30 years in the context of extracorporeal circulation, there is an ongoing debate about the benefits of their routine application. Methylprednisolone was given as early as 1966 to reduce vasoconstriction during cardiopulmonary bypass (CPB) and to prevent low output syndrome thereafter. An explanation for these findings was recently published. Lipid mediators lead to vasoconstriction and inflammatory cytokine production during CPB. There is no doubt about the potential of corticosteroids to reduce inflammatory and enhance anti-inflammatory mediators, while their possible influence on clinical parameters and their side effects are controversial, as discussed in the literature. There have been contradictory results with respect to pulmonary oxygenation, while an increase in the patient's blood glucose levels, however clinically unimportant, could be demonstrated. The influence of other drugs affecting the inflammatory response has to be taken into account, leading to a patient-specific recommendation for the use of corticosteroids during operations requiring CPB.     

体外循环心内直视手术中胰岛素抵抗的研究

目的　探讨体外循环 (CPB)中胰岛素抵抗 (IR)情况。方法　心脏直视手术患者 2 6例 ,分别测定其麻醉前、CPB前、CPB 15min、开放升主动脉后 5min和停CPB 2 0min的血胰岛素、C肽、生长激素、皮质醇、血糖和红细胞压积 ,计算胰岛素血糖比 (I/G)和胰岛素敏感性指数 [1/ (I×G) ]。结果　胰岛素、C肽、生长激素、皮质醇、血糖在CPB中和CPB后浓度均显著高于CPB前 (P <0 .0 1)。1/ (I×G)体外循环前为 0 .0 2 3 0 ,转机后CPB 15min、开放升主动脉后 5min和停CPB 2 0min分别为0 .0 0 2 1、0 .0 0 2 6、0 .0 0 2 9,与体外循环前相比有显著下降 (P <0 .0 1)。I/G体外循环前为 1.37,转机后CPB 15min、开放升主动脉后 5min和停CPB 2 0min分别为 2 .0 9、1.85、1.91,与体外循环前相比明显升高 (P <0 .0 5 )。结论　CPB中应激激素和血糖浓度增加明显 ,CPB期间存在明显的IR ,并且这些变化随应激刺激的增强而加强。     

Platelet anesthesia with nitric oxide with or without eptifibatide during cardiopulmonary bypass in baboons

OBJECTIVE:This study tested the hypothesis that nitric oxide or nitric oxide and eptifibatide (Integrilin) reversibly inhibit platelet activation and consumption during cardiopulmonary bypass and rapidly restore platelet numbers and function after bypass. METHODS: Nitric oxide, a short-acting, reversible platelet inhibitor, was studied with and without eptifibatide, a short-acting, reversible glycoprotein IIb/IIIa inhibitor, in 21 baboons that underwent 60 minutes of normothermic cardiopulmonary bypass with peripheral cannulas. A control group, a group that received 80 ppm nitric oxide, and a group that received both nitric oxide and eptifibatide were studied. Blood samples were obtained at several time points to determine platelet count, aggregation in response to adenosine diphosphate, and levels of beta-thromboglobulin, prothrombin fragment 1.2, and thrombin-antithrombin complex. Template bleeding times were measured before and at 4 intervals after cardiopulmonary bypass. RESULTS: Both nitric oxide and the combination of the 2 drugs significantly attenuated platelet consumption, improved postbypass function, and reduced plasma beta-thromboglobulin release with respect to values in control animals. Both nitric oxide and the combination restored baseline bleeding times 55 minutes after cardiopulmonary bypass ended. No significant differences between nitric oxide and the combination were found for any measurement. CONCLUSION: Nitric oxide with or without eptifibatide protects platelets during cardiopulmonary bypass and accelerates restoration of normal bleeding times after operation in a baboon model. Although nitric oxide and eptifibatide reversibly inhibit platelets by different mechanisms, in the absence of a wound no synergistic effect was demonstrated.     

Inflammatory response after coronary revascularization with or without cardiopulmonary bypass

BACKGROUND: We sought to investigate the effect of multiple coronary artery bypass grafting (CABG) with or without cardiopulmonary bypass (CPB) on the perioperative inflammatory response. METHODS: Sixty patients undergoing CABG were randomly assigned to one of two groups: (A) on pump with conventional CPB and cardioplegic arrest, and (B) off pump on the beating heart. Serum samples were collected for estimation of neutrophil elastase, interleukin 8 (IL-8), C3a, and C5a preoperatively and at 1, 4, 12, and 24 hours postoperatively. Furthermore, white blood cell (WBC), neutrophil, and monocyte counts were carried out preoperatively and at 1, 12, 36 and 60 hours postoperatively. Overall incidence of infection and perioperative clinical outcome were also recorded. RESULTS: The groups were similar in terms of age, weight, gender ratio, extent of coronary disease, left ventricular function, and number of grafts per patient. Neutrophil elastase concentration peaked early after CPB in the on-pump group, with a decline with time. Repeated-measures analysis of variance between groups and comparisons at each time point (modified Bonferroni) showed elastase concentrations were significantly higher in the on-pump than the off-pump group (both p < 0.0001). IL-8 increased significantly after surgery in the on-pump group, with no decline during the observation period (p = 0.01 vs off pump). C3a and C5a rose early after surgery in both groups when compared with baseline values. Postoperative WBC, neutrophil, and monocyte counts were significantly higher in the on-pump than the off-pump group (p < 0.01). Finally, the incidence of postoperative overall infections was significantly higher in the on-pump group (p < 0.0001 vs off pump). CONCLUSIONS: CABG on the beating heart is associated with a significant reduction in inflammatory response and postoperative infection when compared with conventional revascularization with CPB and cardioplegic arrest.     

Activation of hemostasis after coronary artery bypass grafting with or without cardiopulmonary bypass

Activation of coagulation, fibrinolysis, and the vascular endothelium occurs after heart surgery with cardiopulmonary bypass (CPB), but the effects of eliminating CPB in patients undergoing coronary artery bypass grafting (CABG) are unknown. Therefore, we compared the hemostatic profiles of off-pump and on-pump CABG patients. Two groups of consecutive patients participating in a larger trial (the Octopus Trial) were randomly allocated to undergo CABG with (n = 20) or without (n = 20) CPB. Platelet numbers and plasma concentrations of P-selectin, prothrombin fragment 1.2 (F1.2), soluble fibrin, d-dimers, and von Willebrand factor (as a marker of endothelial cell activation) were measured and corrected for hemodilution. Compared with the on-pump CABG group, F1.2 and d-dimer levels were significantly lower (P = 0.004 and P = 0.03, respectively) in patients having CABG surgery performed off-pump. In the CPB group, F1.2 (median [interquartile range], 450% of baseline [233%-847%]) and d-dimer (538% [318%-1192%]) peaked in the immediate postoperative period and remained increased until Day 4, whereas in the off-pump group, F1.2 and d-dimer levels increased more gradually and peaked on Day 4 (342% [248%-515%] and 555% [387%-882%], respectively). In both groups, von Willebrand factor concentrations were increased until Day 4 (CPB, 308% [228%-405%]; off-pump, 288% [167%-334%]). Despite heparinization, CABG surgery with CPB was associated with excessive thrombin generation and fibrinolytic activity immediately after surgery. The off-pump group demonstrated a delayed postoperative response that became equal in magnitude to the CPB in the later (20-96 h) postoperative period.     

Prostacyclin in cardiopulmonary bypass operations

The effects of prostacyclin (PGI2) on postoperative blood loss and on the deposits which are known to form on filters in the bypass circuit were studied in patients undergoing operations with cardioopulmonary bypass. In this double-blind, randomized study, PGI2 or a placebo solution was administered to 56 patients undergoing elective cardiac operations. At the end of cardipulmonary bypass, the arterial line filter was removed from the circuit and blood losses were accurately recorded. There was no statistically significant difference in either the amount or the pattern of postbypass bleeding between the PGI2 and the control patients. However, the changes in weight of the arterial line filters and their electron microscopic appearances suggest that PGI2 can reduce the deposition of platelets and fibrin on the filter mesh, and in this role it may be of value in reducing visceral injury during cardiac operations.