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

Pro-inflammatory cytokines in elective flap surgery

BACKGROUND

Surgical trauma releases inflammatory mediators such as pro-inflammatory cytokines. In this prospective, controlled, randomized trial we investigated the release of pro-inflammatory cytokines and monocyte/macrophage activation in patients scheduled for breast reconstruction after mastectomy. Patients were allocated to one of three surgical procedures, differing in complexity and in the need for implants used for reconstruction.

METHODS

Thirty mastectomized women underwent delayed breast reconstruction with the lateral thoracodorsal flap (LTD), the latissimus dorsi flap (LD), or the pedicled transverse rectus abdominis muscle flap (TRAM). Blood samples for TNF, IL-6, IL-8, neopterin, C-reactive protein (CRP), and leukocyte determination were drawn pre-operatively, 24 h, and 2 weeks post-operatively.

RESULTS

All groups had significantly elevated IL-6 levels 24 h after surgery. The levels were significantly higher in the TRAM group compared to the LTD and LD groups. IL-8 levels were increased in all groups 2 weeks after surgery (P < 0.05), the LTD (83 pg/mL) and LD (84 pg/mL) group having higher mean IL-8 levels than the TRAM patients (48 pg/mL) (ns). TNF and leukocyte counts were within the normal range. CRP levels were elevated in all groups one day after surgery (P < 0.05).

CONCLUSION

Flap procedures for breast reconstruction stimulate the pro-inflammatory response. IL-6 levels were highest in patients with TRAM operations, being the most extensive procedure studied, whereas the highest IL-8 levels were seen in women with a saline filled silicone implant suggesting immunomodulation by foreign material. Although all three investigated procedures are major operations in the field of plastic surgery, according to the inflammatory response to trauma they should be regarded as minor procedures.

Off-Pump Surgery Is Associated With Reduced Occurrence of Stroke and Other Morbidity as Compared With Traditional Coronary Artery Bypass Grafting

Background and Purpose— There is growing enthusiasm for coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB). Although deleterious effects of CPB are known, it remains to be proven that avoiding CPB will result in reduction in morbidity. We sought to determine whether off-pump surgery is associated with reduced occurrence of adverse outcomes as compared with CABG with CPB.

Methods— Studies were identified by searching the MEDLINE, EMBASE and the Cochrane Register 1980 to 2006 (February). We also searched the reference lists of randomized clinical trials (RCT) and reviews to look for additional studies. Study selection: RCTs comparing off-pump surgery to CABG with CPB. No restriction applied on the size of the trial or end point reports. Data extraction: 2 reviewers independently searched for studies, read abstracts and abstracted all data. Data synthesis: combined estimates were obtained using fixed or random effect meta-analyses. Relative risks and risk differences were calculated. Heterogeneity was assessed using χ 2 and I 2 values.

Results— There were 3996 patients enrolled in 41 RCTs (mean age 62, 22% female). No study reported information on race. Off-pump CABG was associated with a 50% reduction in the relative risk of stroke (95% CI, 7% to 73%), 30% reduction in atrial fibrillation (AF; 95% CI, 16% to 43%) and 48% reduction in wound infection (95% CI, 26% to 63%) with no heterogeneity among RCTs. This translated into avoidance of 10 strokes, 80 cases of AF and 40 infections per 1000 CABG. Fewer distal grafts were performed and there was evidence for >10 reinterventions per 1000 with off-pump CABG. Long-term follow-up is not yet reported in the trials.

Conclusions— Off-pump CABG is associated with reduced risk of stroke, AF and infections as compared with CABG with CPB. Evidence should be generalized taking into account RCT enrollment limitations, drawbacks related to training requirements, propensity to perform fewer grafts and likely reinterventions after off-pump surgery.

Functional renal outcome in on-pump and off-pump coronary revascularization: a propensity-based analysis

BACKGROUND

Since the advent of off-pump coronary artery bypass grafting (OPCAB), comparisons have been made between it and on-pump coronary artery bypass grafting. Some observe a lesser incidence of acute renal failure requiring renal replacement therapy with OPCAB whereas others do not. The objective was to compare the occurrence of renal adverse outcome between on-pump coronary artery bypass grafting and OPCAB. Renal adverse outcome was defined as minor (20% increase in serum creatinine from preoperative) or major (composite end point of postoperative serum creatinine >200 mumol/L or postoperative mechanical renal support).

METHODS

The study was based on 2,041 patients with no known preoperative renal disease having first-time isolated coronary artery bypass grafting of multiple coronary arteries between January 2001 and November 2003, at St. Mary's Hospital, Harefield Hospital, and Hammersmith Hospital, in West London; 1,224 patients had on-pump coronary artery bypass grafting and 817 patients had OPCAB. Selection bias for surgical technique was addressed by calculating the propensity score for each patient and using it as an independent variable for adjustment in the multivariate analysis. Univariate and multivariate ordered logistic regressions were used to identify factors associated with renal adverse outcome ordered as none, minor, and major.

RESULTS

The number of grafts was 3.22 +/- 0.82 for the on-pump coronary artery bypass grafting group and 3.35 +/- 0.95 for the OPCAB group. On-pump coronary artery bypass grafting and increasing age were found to be the strongest independent predictors (p < 0.001) of renal adverse outcome. Other independent predictors included hypertension (p = 0.005), diabetes (p = 0.032), and preoperative serum creatinine (p = 0.001). A left ventricular ejection fraction of 0.30 to 0.49 (p = 0.099) and an ejection fraction of 0.50 or greater (p < 0.001) were associated with decreased risk compared with patients with an ejection fraction of less than 0.30. Interestingly, the use of non-left internal mammary arterial conduits significantly decreased the likelihood of renal adverse outcome (p = 0.034).

CONCLUSIONS

The results of this propensity-based study show that the OPCAB technique may reduce the risk for minor and major renal adverse outcome after coronary artery bypass grafting.

Cellular inflammatory response and clinical outcome in cardiac surgery

PURPOSE

This review briefly summarizes recent advances in the understanding of the pathophysiology of the inflammatory response to cardiac surgery and its ties to clinical outcomes. Links between specific inflammatory mediators and vulnerable organs will be emphasized, along with genetic risk factors that render specific patients susceptible to these complications.

RECENT FINDINGS

Circulation of blood on the cardiopulmonary bypass circuit and the operative procedure itself provoke activation of circulating hematopoietic cells and vascular endothelial cells. These activated cells subsequently secrete mediators that amplify this inflammatory response and activated phagocytes undergo changes that facilitate their exit from the circulation into tissue, where they exacerbate organ complications of the procedure. Cardiac, renal and pulmonary dysfunction are among the most common complications of cardiac surgery and progress has been made in recent years demonstrating how the cellular inflammatory response is related to adverse outcomes in these organs. Accordingly, this review will focus on these three systems and the pathophysiology of their cardiac surgical complications.

SUMMARY

Advances in our understanding of the pathways by which inflammatory mediators contribute to host injury offers the promise of interventions that are tailored to specific risks and the possibility of preoperatively identifying those patients most likely to benefit.

Impact of off-pump coronary artery bypass surgery on postoperative bleeding: current best available evidence

Cardiopulmonary bypass (CPB) is a prerequisite for open-heart surgery, and is a procedure routinely used. CPB exposes blood to artificial surfaces, to mechanical trauma from the pump, to alterations in temperature, and to dilution with fluids, whole blood, plasma products, and drugs, and leads to the activation of platelets, coagulation, and fibrinolysis. Coagulopathy during cardiac surgery with CPB results in impairment in hemostasis and subsequently higher morbidity and mortality. Recent advances in surgical techniques and postoperative management have aimed at reducing postoperative morbidity and mortality. Off-pump coronary artery bypass (OPCAB) surgery is one such advance that attempts to avoid the deleterious effects of extracorporeal circulation by performing myocardial revascularization without CPB. Emerging evidence from several randomized controlled trials (RCTs) as well as large registries such as the Society of Thoracic Surgeons (STS) database suggests that OPCAB reduces the postoperative morbidity and mortality. This review article attempts to evaluate the current best available evidence from RCTs on the impact of OPCAB on postoperative bleeding and transfusion requirements.

Modulation of systemic inflammatory response after cardiac surgery

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

Cerebral Ischemic Injury and Cognitive Impairment After Off-Pump and On-Pump Coronary Artery Bypass Grafting Surgery

BACKGROUND

Off-pump coronary artery bypass grafting surgery reduces the intraoperative cerebral embolic load and may therefore cause less brain injury. The main aim of this study was to compare off-pump and on-pump surgery with regard to the frequency of new postoperative cerebral ischemic lesions and the prevalence of postoperative cognitive impairment. We also assessed whether preoperative cerebral ischemic injury predicts the risk for cognitive dysfunction after surgery.

METHODS

One hundred twenty patients with ischemic coronary artery disease were prospectively randomized to undergo off-pump or on-pump surgery. A detailed neuropsychological assessment and a cerebral magnetic resonance imaging examination were performed on the day before and at 3 months postoperatively. The neuropsychological assessment was repeated at 12 months.

RESULTS

There was no significant (p = 0.17) difference between off-pump (8.2%) and on-pump (17.3%) surgery with regard to new postoperative cerebral lesions. The prevalence of cognitive impairment after surgery was also similar in the two groups (3 months: off-pump 20.4%, on-pump 23.1%, p = 0.74; 12 months: off-pump 24.1%, on-pump 23.1%, p = 0.90). The degree of preoperative cerebral ischemic injury was significantly associated with cognitive dysfunction after on-pump (p = 0.02) but not after off-pump (p = 0.22) surgery. None of the patients with normal preoperative radiologic findings were found to have cognitive impairment at 3 months postoperatively (p = 0.04).

CONCLUSIONS

Long-term cognitive function and magnetic resonance imaging evidence of brain injury were similar after off-pump and on-pump coronary artery bypass grafting surgery. Preoperative cerebral magnetic resonance imaging can be used to predict the risk for cognitive dysfunction after coronary artery bypass grafting surgery.

Reduced intracellular oxygen radical production in whole blood leukocytes from COPD patients and asymptomatic smokers

RATIONALE AND OBJECTIVES

COPD is characterized by irreversible airflow obstruction. It has, however, become clear that COPD also is a systemic disease. In the present study, we sought to investigate its impact on different peripheral leukocyte subpopulations that are recognized as important effector cells in the lung tissue.

METHODS

We enrolled 20 patients with stable, moderate COPD (FEV1, 33 to 69%). Ten asymptomatic smokers and 10 nonsmokers served as control groups. Flow cytometry and whole blood analysis were used to minimize unwanted ex vivo modulation. Oxidative burst and adhesion molecule mobilization were analyzed on freshly drawn cells and after in vitro activation.

MEASUREMENTS AND MAIN RESULTS

We found reduced oxidative burst in neutrophils, monocytes, and eosinophils after in vitro stimulation with tumor necrosis factor (TNF) and the bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) in both COPD patients and asymptomatic smokers as compared to nonsmoking control subjects. Vascular involvement was determined as increased soluble intercellular adhesion molecule-1 (sICAM-1) in the COPD group. There were no differences in adhesion molecule expression among the three groups. However, in COPD patients who had smoked the same morning prior to blood sampling, we found a reduced ability to mobilize adhesion molecule CD11b after TNF plus fMLP activation in all investigated cell types. "Acute" smoking did not significantly alter respiratory burst measurements.

CONCLUSIONS

Both COPD patients and asymptomatic smokers have increased levels of sICAM-1 and a reduced intracellular oxidative burst in vitro, indicating a vascular endothelial activation and a possible state of refractoriness in circulating phagocytes in COPD. Although expression and mobilization of adhesion molecules were similar between groups, the acute smoke effect on CD11b points out the value of information on smoking behavior when analyzing function of peripheral inflammatory cells in a smoking population.

Off-Pump Coronary Artery Surgery for Reducing Mortality and Morbidity

OBJECTIVES

The purpose of this study was to assess the effects of off-pump coronary bypass surgery (OPCAB) on mortality and morbidity.

BACKGROUND

Despite its potential for reducing morbidity and mortality, OPCAB's role in clinical practice remains controversial.

METHODS

A meta-analysis of 37 randomized controlled trials (RCTs) (n = 3,449) and 22 risk-adjusted (logistic regression or propensity-score) observational studies (n = 293,617) was performed. Two reviewers performed literature searches (MEDLINE, EMBASE, PubMed, reference lists), quality assessment, and data extraction. Treatment effects were calculated as odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

In RCTs, OPCAB was associated with reduced atrial fibrillation (OR 0.59; 95% CI 0.46 to 0.77) and trends toward reduced 30-day mortality (OR 0.91 95% CI 0.45 to 1.83), stroke (OR 0.52; 95% CI 0.25 to 1.05), and myocardial infarction (OR 0.79; 95% CI 0.50 to 1.25). Observational studies showed OPCAB to be associated with reduced 30-day mortality (OR 0.72; 95% CI 0.66 to 0.78), stroke (OR 0.62; 95% CI 0.55 to 0.69), infarction (OR 0.66; 95% CI 0.50 to 0.88), and atrial fibrillation (OR 0.78; 95% CI 0.74 to 0.82). At one to two years, OPCAB was associated with trends toward reduced mortality, but also increased repeat revascularization (RCT: OR 1.75, 95% CI 0.78 to 3.94; Observational: OR 1.35, 95% CI 0.76 to 2.39).

CONCLUSIONS

Randomized controlled trials did not find, aside from atrial fibrillation, the statistically significant reductions in short-term mortality and morbidity demonstrated by observational studies. These discrepancies might be due to differing patient-selection and study methodology. Future studies must focus on improving research methodology, recruiting high-risk patients, and collecting long-term data.

Hemostasis in Off-Pump Compared to On-Pump Coronary Artery Bypass Grafting: A Prospective, Randomized Study

BACKGROUND

We hypothesized that off-pump coronary artery bypass grafting has less impact on the hemostatic systems than on-pump surgery.

METHODS

Thirty-one patients were randomized to on-pump or off-pump coronary artery bypass grafting. Factors of hemostasis as well as markers of endothelial activation were measured up to 24 hours after the operation: Fibrin D dimer, prothrombin fragment 1+2, alpha2-macroglobulin, protein C1 esterase inhibitor, fibronectin, and von Willebrand factor. Overall hemostasis potential, overall coagulation potential, and overall fibrinolysis potential were determined with a previously developed assay. We also measured platelet count before and after surgery.

RESULTS

Fibrin D dimer and prothrombin fragment 1+2 concentrations were lower during surgery in the off-pump group (p < 0.001). Four hours after admission to the intensive care unit, these differences were eliminated. alpha2-macroglobulin, protein C1 esterase inhibitor, fibronectin, and von Willebrand factor concentrations did not differ between groups (p = 0.59, p = 0.28, p = 0.22, and p = 0.69). Protein C1 esterase inhibitor and von Willebrand factor concentrations increased over time (p < 0.001) in both groups. Overall hemostasis potential and overall coagulation potential increased over time (p < 0.001), while overall fibrinolysis potential decreased (p < 0.001) with no difference between groups (p = 0.69, p = 0.91). Platelet count decreased on the first postoperative day (p < 0.001), but increased from the first to the third postoperative day (p = 0.004) in both groups without any inter group difference (p = 0.82).

CONCLUSIONS

There was a tendency toward less activation of coagulation and fibrinolysis in low-risk patients during elective off-pump coronary artery bypass surgery when compared with on-pump surgery.

Influence of cold ischemia time on complement activation, neopterin, and cytokine release in liver transplantation

OBJECTIVES

The aim of this study was to determine whether a cold ischemia time (CIT) of >12 hours influences the activation of complement as well as the plasma concentrations of neopterin, interleukin (IL)-6, or IL-8 in orthotopic liver transplantation (OLT).

PATIENTS AND METHODS

Eighteen consecutive patients undergoing OLT using a veno-venous bypass technique were divided into 2 groups: duration of CIT >12 hours (group 1; n = 11), and CIT <12 hours (group 2; n = 7). Blood samples were drawn preoperatively, 1 minute before, and 120 minutes after reperfusion.

RESULTS

Preoperatively, complement split products, neopterin, IL-6, and IL-8 levels did not differ between the groups. At 120 minutes after reperfusion, the concentrations of C3a, SC5b-9, neopterin, IL-6, and IL-8 were significantly increased in both groups compared with the preoperative values or the levels determined 1 minute before reperfusion (P < .05). Patients in group 1 showed significantly higher IL-8 levels at 120 minutes after reperfusion (P < .05).

CONCLUSION

Complement is activated and pro-inflammatory cytokines released after reperfusion in OLT using a veno-venous bypass technique, but only IL-8 plasma levels were influenced by the duration of CIT. Therefore, alterations following prolonged CIT seem to not be complement-mediated.