Demonstration and Operative Influence of Low Prime Volume Closed Pump

Various improvements have been made in cardiopulmonary bypass (CPB) in the past few decades. We designed a new type of CPB to reduce the secretion of systemic inflammatory markers. We used a low prime volume pump (LPVP), completely closed CPB circuit and examined coagulant factors and inflammatory cytokines. In this study, we demonstrate the efficacy of LPVP using molecular biological data. Fourteen patients were randomized prospectively into two groups: Group L patients underwent LPVP ( n = 8) and Group N patients underwent normal prime volume CPB ( n = 6). We measured thrombin-antithrombin III complex (TAT), complement factor (C3a), and interleukin (IL)-10 levels at four time points. TAT (66.1 ± 15.1 ng·mL−1), C3a (1895 ± 282 ng·mL−1) and IL-10 (486 ± 114 pg·mL−1) levels in Group N were significantly higher than in Group L (TAT, 19.5 ± 4.4 ng·mL−1; IL-10, 105 ± 24.6 pg·mL−1; C3a, 1349 ± 369 ng·mL−1) immediately following CPB. LPVP demonstrated a lower systemic inflammatory response compared to normal prime volume CPB, as assessed using a molecular biological approach.

Postoperative Cognitive Dysfunction After Cardiac Surgery

Prolonged postoperative cognitive dysfunction (POCD) is reported to occur frequently after cardiac surgery. However, it is rarely assessed in routine clinical practice and receives little attention. Although the cerebral consequences of cardiopulmonary bypass have been measured clinically, insights into the resulting molecular and pathologic events within the brain have only begun to be investigated. POCD is likely to impair quality of life and constitutes a large burden on society when elderly patients prematurely lose their independence. Numerous studies have reported that neurocognitive deficit is associated with heightened mortality, increased length of hospital stay, and discharge to a nursing home. This is linked with a tremendous demand for health-care resources. Because of the magnitude of the clinical problem, serious consideration must be directed toward understanding its etiology and the development of neuroprotective strategies. Clearly identifying the mechanisms of POCD is challenging. The purpose of this review is to discuss recent developments in our understanding of the pathophysiologic mechanisms, prevention, and treatments that have been designed to ameliorate brain dysfunction after cardiac surgery.

Artificial surface-induced cytokine synthesis: effect of heparin coating and complement inhibition

BACKGROUND

Contact between blood and artificial surfaces induces an inflammatory response including activation of leukocytes and platelets, as well as complement and other plasma cascade systems. In the present study we investigated the roles of complement and surface modification in polyvinylchloride-induced cytokine production.

METHODS

Human whole blood was incubated in rotating loops of polyvinylchloride or heparin-coated polyvinylchloride tubing for 4 hours. Plasma concentrations of the cytokines tumor necrosis factor alpha, interleukin (IL) 1 beta, IL-6, IL-8, IL-10, and monocyte chemoattractant protein 1 (MCP-1) were quantified.

RESULTS

Polyvinylchloride induced a substantial increase in IL-8 and MCP-1, which was abolished by cycloheximide, indicating that they were synthesized during incubation. Interleukin 8 synthesis was completely complement-dependent since it was abolished by neutralizing antibodies to factor D and complement factor 5, as well as by a complement factor 5a receptor antagonist. Monocyte chemoattractant protein 1 synthesis was reduced by approximately half the amount by the complement inhibitors. Heparin-coated polyvinylchloride efficiently prevented synthesis of both IL-8 and MCP-1. Addition of recombinant human complement factor 5a to blood incubated in heparin-coated polyvinylchloride restored IL-8 and MCP-1 production completely and partly, respectively. In contrast to IL-8 and MCP-1, tumor necrosis factor alpha, IL-1 beta, interleukin 6 and IL-10 increased only marginally. A minor but significant increase in IL-1 beta was complement-dependent, whereas a similar increase in IL-10 was completely prevented by heparin-coated polyvinylchloride. No significant changes were observed for tumor necrosis factor alpha and IL-6.

CONCLUSIONS

Polyvinylchloride induced a marked increase in IL-8 and MCP-1, in contrast to a marginal increase in tumor necrosis factor alpha, IL-1 beta, IL-6, and IL-10. The increase in IL-8 and MCP-1 was prevented by heparin-coated polyvinylchloride. Interleukin 8 production was totally complement-dependent and mediated by complement factor 5a.

Heparin-coated cardiopulmonary bypass circuits: current status

Heparin-coated circuits have been subjected to vigorous testing, both experimentally and clinically, for the past decade. When the functions of heparin are preserved on the surface, the heparinized surface plays multiple roles in attenuating the systemic inflammatory response. These include the ability to attenuate contact activation, coagulation activation, complement activation and, directly or indirectly, platelet and leukocyte activation. The heparinized surface also renders the cardiopulmonary bypass (CPB) circuits hydrophilic and protein resistant and augments lipoprotein binding. The multifunctional nature of the heparinized surface contributes to the overall biocompatibility of the surface. Clinically, heparin-coated circuits become most effective in reducing systemic inflammatory response and in improving morbidity, mortality, and other patient outcome related parameters when material-independent blood activation is controlled or minimized through a global biocompatibility strategy. Techniques involved in the global biocompatibility strategy are readily available and are being effectively and safely practiced at several centers. With the global biocompatibility strategy, outstanding and reproducible results have been routinely achieved with conventional CPB techniques. Alternative revascularization procedures should equal or surpass conventional CPB, using best clinically proven strategies with respect to patient outcome and long-term graft patency.