Cytokine and lipid mediator blood concentrations after coronary artery surgery

Interleukin-6 in surgery, trauma, and critical care part II: clinical implications

A variety of cytokines play a role in the inflammatory response. Interleukin-6 (IL-6)-type cytokines are released in response to tissue injury or an inflammatory stimulus, and act locally and systemically to generate a variety of physiologic responses. Interleukin-6 concentrations are elevated after surgery, trauma, and critical illness. The magnitude of IL-6 elevation correlates with the extent of tissue trauma/injury severity. Furthermore, there is an association between IL-6 elevation and adverse outcome. Interleukin-6 levels can also be used to stratify patients for therapeutic intervention.

Interleukin-6 in surgery, trauma, and critical care part II: clinical implications

A variety of cytokines play a role in the inflammatory response. Interleukin-6 (IL-6)-type cytokines are released in response to tissue injury or an inflammatory stimulus, and act locally and systemically to generate a variety of physiologic responses. Interleukin-6 concentrations are elevated after surgery, trauma, and critical illness. The magnitude of IL-6 elevation correlates with the extent of tissue trauma/injury severity. Furthermore, there is an association between IL-6 elevation and adverse outcome. Interleukin-6 levels can also be used to stratify patients for therapeutic intervention.

Alterations in plasma soluble vascular endothelial growth factor receptor-1 (sFlt-1) concentrations during coronary artery bypass graft surgery: relationships with post-operative complications

Background

Plasma concentrations of sFlt-1, the soluble form of the vascular endothelial growth factor receptor (VEGF), markedly increase during coronary artery bypass graft (CABG) surgery with extracorporeal circulation (ECC). We investigated if plasma sFlt-1 values might be related to the occurrence of surgical complications after CABG.

Methods

Plasma samples were collected from the radial artery catheter before vascular cannulation and after opening the chest, at the end of ECC just before clamp release, after cross release, after weaning from ECC, at the 6^th and 24^th post-operative hour. Thirty one patients were investigated. The presence of cardiovascular, haematological and respiratory dysfunctions was prospectively assessed. Plasma sFlt-1 levels were measured with commercially ELISA kits.

Results

Among the 31 investigated patients, 15 had uneventful surgery. Patients with and without complications had similar pre-operative plasma sFlt-1 levels. Lowered plasma sFlt-1 levels were observed at the end of ECC in patients with haematological (p = 0.001, ANOVA) or cardiovascular (p = 0.006) impairments, but not with respiratory ones (p = 0.053), as compared to patients with uneventful surgery.

Conclusion

These results identify an association between specific post-CABG complication and the lower release of sFlt-1 during ECC. sFlt-1-induced VEGF neutralisation might, thus, be beneficial to reduce the development of post-operative adverse effects after CABG.

Release of soluble vascular endothelial growth factor receptor-1 (sFlt-1) during coronary artery bypass surgery

Background

This study was conducted to follow plasma concentrations of sFlt-1 and sKDR, two soluble forms of the vascular endothelial growth factor (VEGF) receptor in patients undergoing coronary artery bypass graft (CABG) surgery with extracorporeal circulation (ECC).

Methods

Plasma samples were obtained before, during and after surgery in 15 patients scheduled to undergo CABG. Levels of sFlt-1 and KDR levels were investigated using specific ELISA.

Results

A 75-fold increase of sFlt-1 was found during cardiac surgery, sFlt-1 levels returning to pre-operative values at the 6^th post-operative hour. In contrast sKDR levels did not change during surgery. The ECC-derived sFlt-1 was functional as judge by its inhibitory effect on the VEGF mitogenic response in human umbilical vein endothelial cells (HUVECs). Kinetic experiments revealed sFlt-1 release immediately after the beginning of ECC suggesting a proteolysis of its membrane form (mFlt-1) rather than an elevated transcription/translation process. Flow cytometry analysis highlighted no effect of ECC on the shedding of mFlt-1 on platelets and leukocytes suggesting vascular endothelial cell as a putative cell source for the ECC-derived sFlt-1.

Conclusion

sFlt-1 is released during CABG with ECC. It might be suggested that sFlt-1 production, by neutralizing VEGF and/or by inactivating membrane-bound Flt-1 and KDR receptors, might play a role in the occurrence of post-CABG complication.

Biocompatibility of Heparin-Coated Cardiopulmonary Bypass Circuits in Coronary Patients With Left Ventricular Dysfunction Is Superior to PMEA-Coated Circuits

BACKGROUND

Several coating techniques for extracorporeal circulation have been developed to diminish the systemic inflammatory response during cardiopulmonary bypass (CPB). The aim of this study was to evaluate the clinical effectiveness and biocompatibility of heparin-coated and poly-2-methoxyethylacrylate (PMEA)-coated CPB circuits on coronary patients with left ventricular systolic dysfunction.

METHODS

Thirty-six patients who underwent elective coronary artery bypass grafting were divided into two equal groups: group H (n = 18), heparin-coated; group P (n = 18), PMEA coated. Clinical outcomes, hematologic variables, cardiac enzymes, malondialdehyde (MDA), and acute phase inflammatory response (including myeloperoxidase (MPO), catalase, hsCRP, and IL-8) were analyzed perioperatively.

RESULTS

Demographic, CPB, and clinical outcome data were similar for both groups. Plasma fibrinogen, total protein, albumin, and platelet count decreased, neutrophil count, MDA, IL-8, MPO, and catalase levels increased during CPB. During CPB, MPO and catalase values were significantly higher in group P (p = 0.02 and p = 0.01) and postoperative MDA concentration was lower in group H (p = 0.03). Platelet counts were better preserved in group H during and after CPB but neutrophil count and IL-8 level did not differ between the groups. Postoperative total protein, albumin, and fibrinogen levels were higher in group H (p < 0.05). The postoperative first day levels of troponin-I, CK-MB, and CRP increased in both groups without any significant differences between the groups.

CONCLUSIONS

Heparin-coated circuit provided better suppression of perioperative inflammatory markers and exhibited more favorable effects on hematologic variables than PMEA-coated circuit.

Mechanical ventilation strategies and inflammatory responses to cardiac surgery: a prospective randomized clinical trial

OBJECTIVE

To examine whether postoperative mechanical ventilation with lower tidal volumes (V(T)) has protective effects on inflammatory responses induced by cardiopulmonary bypass (CPB) surgery in smokers and nonsmokers.

DESIGN AND SETTING

Prospective, randomized, controlled clinical trial in the intensive care unit of a university hospital.

PATIENTS AND PARTICIPANTS

We examined 44 patients (22 smokers, 22 nonsmokers) immediately after uncomplicated CPB surgery.

INTERVENTIONS

Ventilation was applied for 6 h with either V(T) of either 6 or 12 ml/kg ideal body weight.

MEASUREMENTS AND RESULTS

The time course of serum tumor necrosis factor (TNF) alpha, interleukin (IL) 6, and IL-8 determined 0, 2, 4, and 6 h after randomization did not differ significantly between the ventilatory strategies. By contrast, in bronchoalveolar lavage fluids sampled after 6 h only TNF-alpha levels were significantly higher in the high V(T) group than the low V(T) group (50+/-111 pg/ml vs. 1+/-7 pg/ml). IL-6 and IL-8 concentrations did not differ between groups. Subgroup analysis of patients with serum TNF-alpha level higher than 0 pg/ml after surgery revealed lower TNF-alpha serum levels during lower V(T) ventilation. All observed effects were small, independent of patients' history of smoking, and were not correlated with duration of ventilation and ICU stay.

CONCLUSIONS

Ventilation with lower V(T) had no or only minor effect on systemic and pulmonary inflammatory responses in patients with healthy lungs after uncomplicated CPB surgery. Our data do not suggest a clinical benefit of using low V(T) ventilation in these selected patients.