Successful restoration of cell-mediated immune response after cardiopulmonary bypass by immunomodulation

Effects of cardiopulmonary bypass on the development of lymphopenia and sepsis after cardiac surgery in children with congenital cardiopathy

The objective of the present study was to investigate whether lymphopenia occurring after heart surgery with cardiopulmonary bypass (CPB) is related to apoptosis and or sepsis in children. The design was a prospective cohort study in a third level care hospital in Mexico City. In total, 68 children (31 girls and 37 boys) with congenital cardiopathy who needed corrective cardiac surgery with or without CPB were included. The samples were obtained from central blood before, immediately after and 24 h after surgery. Complete blood counts and lymphocyte apoptosis were analyzed. Systemic inflammatory response syndrome (SIRS), sepsis and the type of microorganism were recorded. A total of 53 patients received CPB and 15 did not. Lymphocyte count decreased after surgery in both groups (P<0.001). However, neutrophil count increased markedly in both groups. Apoptosis of B (CD19⁺) lymphocytes was higher in the non-CPB group (14, 2 and 21% before, immediately after and 24 h after surgery, respectively) than the CPB group (0, 2 and 3%, respectively), but apoptosis of cytotoxic T lymphocytes (CD8⁺) was higher in the CPB group (5, 4 and 3% before, immediately after and 24 h after surgery, respectively) than in the non-CPB group (2, 3 and 2%, respectively). However, the extent of apoptosis of T and B lymphocytes after surgery did not differ between groups. The CPB group had more complications than the non-CPB group [38 (71.7%) vs. 9 (60.0%)]. In conclusion, the decrease in lymphocyte count may be related to apoptosis of cytotoxic T lymphocytes in children receiving cardiac surgery with CPB and to apoptosis of B lymphocytes in those not receiving CPB. The decreased lymphocyte counts in both groups suggested that CPB is not the main cause of this decrease. Children who received CPB during surgery had more complications, such as sepsis and cardiogenic shock than did those who did not receive CPB.

Blocking interleukin-1 in sepsis

Interleukin-1 (IL-1) is a polypeptide which possesses a broad spectrum of biological activities, many of which are associated with disease. It has been studied for its ability to induce fever, sleep and anorexia, elevate prostaglandins and nitric oxide, stimulate the release of pituitary hormones, elevate hepatic acute phase proteins, increase gene expression for other cytokines and augment the proliferation of T and B lymphocytes. In addition, IL-1 increases the synthesis of collagenases and decreases the synthesis of proteoglycans, resulting in joint destruction. More recently, IL-1 has been shown to induce hypotension and upregulate endothelial cell adhesion molecules, both important parameters of the septic shock syndrome. IL-1 also possesses host defense properties. For example, pretreatment with IL-1 non-specifically reduces lethality to bacterial and fungal infections, even in the absence of circulating neutrophils. IL-1 has been given to humans in clinical trials; as increasing doses are given, IL-1 is toxic, producing gastrointestinal disturbances and hypotension. It appears that low doses of exogenously administered IL-1 may prove useful as a therapy. On the other hand, blocking the toxic effects of IL-1 may be necessary in the treatment of certain diseases. IL-1 receptor blockade has been studied in human disease including sepsis. Similar to other studies using corticosteroids, antibodies to tumor necrosis factor, bradykinin antagonists and inhibitors of platelet activating factor, clear-cut beneficial effects of IL-1 receptor blockade have not matched those demonstrated in animals.

Interferon-γ counteracts reduced endotoxin responsiveness of whole blood following trauma and cardiopulmonary bypass

Accidental as well as surgical trauma has been reported to cause reduced endotoxin responsiveness of blood in terms of cytokine production. In this study, the effect of interferon-γ (IFN-γ) on tumour necrosis factor-α (TNF-α)-producing capacity of whole blood after severe trauma and cardiac surgery was investigated. Blood samples of severely injured patients were collected at the first day after trauma and of cardiac surgery patients before, 4 h and 2 days after cardiopulmonary bypass (CPB). The blood samples were incubated with INF-γ (0—100 U/ml) for 20 h and subsequently lipopolysaccharide (LPS)-induced TNF-α production was determined. Compared to healthy donors, LPS-induced TNF-α production was significantly reduced in blood cultures of trauma patients on day 1 after trauma and 4 h after CPB. Pre-incubation with IFN-γ in vitro increased endotoxin-induced TNF-α production in volunteers' and all patients' blood specimens in a dose-dependent manner. IFN-γ prompted an elevation of cytokine synthesis in CPB patients' blood which equalled that of volunteers, whereas it caused a lower rise in TNF-α production in blood of multiply injured patients, reaching levels of untreated donors only after incubation with 100 U/ml IFN-γ. These experiments show that hyporesponsiveness of whole blood induced by trauma or cardiac surgery with CPB is not irreversible, but can be counteracted by the immunostimulant IFN-γ. IFN-γ, therefore, could be applied clinically in trauma patients or after cardiac surgery to prevent or to resolve infection complications.

Leucocyte depleting filters and cardiothoracic surgery

Leucocyte filtration technology is now beginning to be used in cardiothoracic surgery. The leucocyte depletion of banked homologous blood has been shown to reduce its immunosuppressive effects, along with a range of other benefits. Use of such a blood product appears to be an attractive option during cardiopulmonary bypass (CPB) as this procedure is recognized as causing immune disturbance and long-term immunosuppression.

White-cell removal filters also appear to have a novel application in the reduction of neutrophil-mediated damage associated with CPB procedures. A strong database from animal work has been recently supplemented by human data that shows clinical benefits from autologous white-cell removal by filtration.

Pharmacological Prevention of the Deleterious Effects of Cardiopulmonary Bypass

Indomethacin is a known immune modulator that inhibits cyclooxygenase. Studies indicate that ketoconazole, a selective lipoxygenase and thromboxane A2 synthetase inhibitor, can prevent activation of the inflammatory cascade by inhibition of proinflammatory mediators. This study was designed to determine if ketoconazole or indomethacin could reduce the adverse effects of extracorporeal circulation. As a double-blind prospective study, 76 patients were randomized into 3 groups according to preoperative medication: indomethacin, ketoconazole, and placebo groups, with 25, 26, and 25 patients, respectively. Four types of parameters were evaluated preoperatively and up to 24 hr after cardiac surgery in all patients: inflammatory (complement C3 and C4, C-reactive protein, immunoglobulins); hematologic; coagulation; and physiologic (blood loss, fluid and blood components received, weight gain, and duration of ventilation). Statistical analyses showed similar patient profiles in each group. Complement C4 decreased in all groups postoperatively, but significantly less in the indomethacin group ( p < 0.01). Ketoconazole reduced postoperative bleeding ( p < 0.0001) as well as the incidence of re-operation for bleeding ( p = 0.05). It was concluded that indomethacin decreases complement (specifically C4) consumption during cardiopulmonary bypass, and ketoconazole may reduce postoperative bleeding by limiting coagulation abnormalities in cardiac surgery patients.

Tuberculous pericardial effusion after coronary artery bypass graft

We describe a case of a recurrent pericardial effusion after coronary artery bypass grafting. This was initially considered to be due to post-pericardiotomy syndrome, but was later treated empirically as tuberculosis. After definitive surgery for this condition, pericardial histology and immunohistochemistry confirmed the diagnosis of tubercular pericarditis. At 4-months follow-up, while continuing anti-tuberculous therapy and corticosteroids, the patient showed consistent improvement without further recurrence of his pericardial effusion. Local reactivation of tuberculosis after pericardiotomy has not been previously reported and merits careful consideration in population groups in which tuberculosis is highly endemic.

Prostaglandin el attenuates impairment of cellular immunity after cardiopulmonary bypass

OBJECTIVE

It is well documented that cardiopulmonary bypass (CPB) severely impairs cellular immunity. The objective of this study was to investigate the effect of prostaglandin E1 (PGE1) on cellular immunity after CPB.

METHODS

Patients who underwent elective cardiac surgery were randomly divided into the PGE1 group (n=12) and the control group (n=12). In the PGE1 group, PGE1 was administered at 20 ng/kg/min from just after the induction of anesthesia to the end of surgery. Peripheral blood mononuclear cells (PBMCs) were taken before anesthesia and on postoperative days 1, 3 and 7 (POD 1, POD 3 and POD 7). Proliferation responses of T cells to phytohemagglutinin (PHA) and pure protein derivative (PPD) antigen were measured as indicators of cellular immunity.

RESULTS

PGE1 significantly attenuated the impairment of both PHA and PPD response after cardiac surgery on POD 1 (PHA response, 30 +/- 21% vs. 53 +/- 32%, control vs. PGE, p=0.048; PPD response, 18 +/- 21% vs. 39 +/- 27%, control vs. PGE, p=0.046). The reduced glutathione content of PBMCs in the control group was significantly decreased on POD 1.

CONCLUSION

PGE1 attenuated the impairment of cellular immunity after cardiac surgery with CPB by reducing oxidative stress on PBMCs.

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.

The immunomodulatory actions of E-type prostaglandins

Prostaglandins (PGs) have been recognised as modulators of immune responses. This has been proved by both in vitro studies and from observations in animals and humans. Administration of prostaglandins for therapeutic purposes, however, has been hampered by their limited bioavailability and their pleiotropic effects, with resultant toxicological profile. Despite this, some success has been demonstrated in the clinic for the control of graft rejection, especially when used as part of a broader immunosuppressant regimen. Full realisation of the therapeutic potential of prostaglandins will depend on a better understanding of their mechanism of action at the cellular level. Recently, it has been appreciated that prostaglandins do not merely inhibit T-cell function, but appear to modulate the profile of lymphocyte sub-populations through regulation of cytokine synthesis and release. Recent efforts have also begun to focus on identifying prostaglandin receptor subtypes important for immune regulation and offer a means, together with targeted delivery, of utilising the immunosuppressant/anti-inflammatory effects of E-type prostaglandins in a safe and effective manner.

COX-2 Inhibitors at The 8th International Conference of the Inflammation Research Association

An intensive search is underway for novel selective inhibitors of cyclo-oxygenase (COX)-2. These compounds promise to be potent anti-inflammatory agents with little gastrointestinal intolerance. Meloxicam, with some selectivity for COX-2, is already marketed, and at least two companies are carrying out clinical studies with selective inhibitors. A variety of potential successor compounds were presented at the 8th International Conference of the Inflammation Research Association (IRA) in Hershey, PA on 27-31 October 1996.

In vivo inhibition of neutrophil activity by a FAS (CD95) stimulating module: arterial in-line application in a porcine cardiac surgery model

OBJECTIVE

Cardiac surgery with cardiopulmonary bypass is associated with aberrant neutrophil activation and potentially severe pathogenic sequelae. This experimental study was done to evaluate a leukocyte inhibition module that rapidly inactivates neutrophils through CD95 stimulation.

METHODS

German landrace pigs (4 groups, each n = 5) underwent cardiac surgery without cardiopulmonary bypass (group I), with cardiopulmonary bypass (group II), with cardiopulmonary bypass plus a leukocyte filter (group III), and with cardiopulmonary bypass plus a leukocyte inhibition module (group IV). The leukocyte filter or leukocyte inhibition module was introduced into the arterial line of the heart-lung machine.

RESULTS

Leukocyte counts were decreased by up to 43% in group IV compared with values in group II (P =.023). In group IV, but not in groups I to III, no delay in spontaneous neutrophil apoptosis was observed after annexin V-propidium iodide staining. Late apoptotic (11.7%) or necrotic neutrophils (9.3%) were detected in 2 animals (group IV). Tumor necrosis factor alpha serum levels increased over time in groups I to III (>2-fold) but remained at baseline levels in group IV (P <.05). Interleukin 8-mediated chemotactic neutrophil transmigration activity increased over time in groups I to III but was totally abrogated in group IV at any time point. The perioperative increase of creatine kinase and creatine kinase MB levels was lower in groups III (1.5-fold and 1.3-fold, respectively) and IV (1.2-fold and 1.5-fold, respectively) compared with values in group II (both 1.9-fold).

CONCLUSIONS

The leukocyte inhibition module downregulated cardiopulmonary bypass-related neutrophil activity and thus might be beneficial in cardiac surgery and other clinical settings with unappreciated neutrophil activation.

Surgical trauma: hyperinflammation versus immunosuppression?

BACKGROUND

Experimental and clinical studies have brought evidence that surgical trauma markedly affects the immune system, including both the specific and the non-specific immune response.

MATERIALS AND METHODS

This report reviews the present knowledge on the mechanisms of surgical trauma-induced immune dysfunction and outlines experimental and clinical approaches to find effective treatment strategies.

RESULTS

Major surgical trauma induces an early hyperinflammatory response, which is characterized by (1) pro-inflammatory tumour necrosis factor alpha (TNF), interleukin (IL)-1, and IL-6 cytokine release and (2) neutrophil activation and microvascular adherence, as well as (3) uncontrolled polymorphonuclear (PMN) and macrophage oxidative burst. The massive and continuous IL-6 release induces an acute phase response, but, more importantly, also accounts for the up-regulation of major anti-inflammatory mediators, such as prostaglandin (PG) E2, IL-10 and transforming growth factor (TGF)-ss. This results in surgical, trauma-induced, immunosuppression, as indicated by (1) monocyte deactivation, reflected by the lack of monocytic TNF- production upon lipopolysaccharide (LPS) stimulation, and (2) a shift of the Th1/Th2 ratio towards a Th2-dominated cytokine pattern. The imbalance between pro-inflammatory and anti-inflammatory cytokines and immuno-competent cells determines the phenotype of disease and should help the physician to compose the therapeutic strategy. In fact, recent clinical studies have shown that both the initial uncontrolled hyperinflammation and the continued cell-mediated immunosuppression represent primary targets to counteract post-surgery immune dysfunction. The balance between inflammatory and anti-inflammatory forces may be restored by interferon gamma (IFN-gamma) to counteract monocyte deactivation; the anti-inflammatory PGE2 may be inhibited by indomethacin to attenuate immunosuppression; or the initial hyperinflammation may be targeted by administration of anti-inflammatory substances, such as granulocyte colony-stimulating factor (G-CSF), hydoxyethyl starch, or pentoxifylline.

CONCLUSIONS

When drawing up the therapeutic regimen the physician should not consider hyperinflammation versus immunosuppression, but hyperinflammation and immunosuppression, aiming at restoring an appropriate mediator- and immune cell-associated balance.

Amplifying cancer vaccine responses by modifying pathogenic gene programs in tumor cells

Immunosuppressive factors, such as vascular endothelial growth factor, transforming growth factor-beta, prostaglandin E2, interleukin (IL)-10, and IL-6, are made frequently by cancer cells. These factors, along with others, can inhibit the development and function of tumor-reactive effector T cells and the clinical results of cancer vaccines. Production of these factors by tumor cells is associated with disease progression and may represent an active immune surveillance escape mechanism. However, a number of factors appear to be made directly in response to signaling molecules, such as RAS, AKT, and signal transducer and activator of transcription 3, which are activated as a result of genetic events that occur during oncogenesis. Methods to overcome the negative effects of immunosuppressive factors, which are "hard wired" into gene programs of cancer cells, might then improve the results of cancer vaccines. For example, specific blocking antibodies, which recognize such factors, or kinase inhibitors, which block the signaling pathways that lead to their production, could potentially be used as vaccine adjuvants. The effects of immunosuppressive factors may also be "turned off" by cytokines with tumor suppressor properties. The enhanced clinical and immunological effects of melanoma vaccines observed after the administration of high doses of interferon-alpha2b provide a "proof of principle" in human patients, that agents which counter the gene programs of cancer cells, causing them to intrinsically resist tumor-reactive T cells, may improve significantly the efficacy of cancer vaccines.

Incidence and outcome of radial artery infections following cardiac surgery

BACKGROUND

Radial artery infections secondary to catheterization for blood pressure monitoring are rare but potentially serious complications. The objective of the study was to evaluate the incidence, the risk factors and the evolution of radial artery infections following cardiac surgery.

METHODS

A retrospective review of 8300 patients undergoing cardiac surgery between 1998 and 2002 at the Montreal Heart Institute (MHI) was undertaken. All patients with superficial radial artery infections, infected radial artery pseudoaneurysms, and arterial catheter-related bacteremia were considered using prospective global surveillance of all nosocomial infections over the study period by an infection control nurse.

RESULTS

Thirteen patients with radial infections were encountered (0.2%) with bacteremia occurring in 9 patients (0.15%). Five patients developed infected radial artery pseudoaneurysms (0.05%) and 5 patients developed subsequent sternal wound infections. Two patients died in their early postoperative evolution. Mean patient age was 67 years old and mean duration of cannulation was 5.8 days. Only 1 patient had diabetes. Seven of 13 patients were positive for Staphylococcus aureus (54%). All patients had undergone cardiopulmonary bypass (CPB) for various procedures. All superficial infections responded well to antibiotic therapy. Early surgical intervention is essential in cases of infected radial artery pseudoaneurysms.

CONCLUSIONS

The postoperative state and cardiopulmonary bypass put patients at risk for infectious complications. Strict systematic changing of arterial lines on a timely basis is unwarranted in our opinion. A high suspicion index, aggressive surgical treatment of bacterial arteritis and appropriate intravenous antibiotics are essential to improve the prognosis.

Immune responses and prediction of major infection in patients undergoing transhiatal or transthoracic esophagectomy for cancer

OBJECTIVE

To investigate alterations in immune responses after transhiatal versus transthoracic esophageal resection and to evaluate the role of preoperative immune functions in predicting postoperative infectious complications.

SUMMARY BACKGROUND DATA

Impaired immune defense is associated with a decreased resistance to infection. Patients undergoing esophageal resection via a transhiatal or transthoracic approach are prone to develop infectious complications. There are no randomized data on immune responses after two major surgical interventions.

METHODS

The study group consisted of 20 patients who were randomly allocated to a limited transhiatal or extended transthoracic esophagectomy for cancer. Blood samples were taken before the operation and at regular intervals thereafter from day 1 to day 10. Monocyte and T-helper type 1 (Th1) and type 2 (Th2) lymphocyte functions were assessed in stimulated whole blood cultures.

RESULTS

Both surgical groups had severely depressed in vitro production of interleukin (IL)-12, IL-10, interferon-gamma, IL-2, IL-4, and IL-13 on postoperative day 1. Depression of Th2-type cytokine production was more profound after transthoracic than after transhiatal esophagectomy (IL-4, P=.005; IL-13,P=.007). Postoperative reduction in Th1-type cytokine production was similar between the two groups (interferon-gamma, P=.40; IL-2, P=.06). Irrespective of the surgical approach, patients who developed major infectious complications after surgery presented with a diminished T-cell cytokine production before the operation compared to those who had a relatively uneventful recovery (IL-4, P=.045; interferon-gamma, P=.064). In regression analysis, the occurrence of postoperative major infection was best predicted by increased duration of anesthesia ( P<.0001) and low preoperative interferon-gamma production ( P=.006).

CONCLUSIONS

Both transhiatal and transthoracic esophagectomy induced severely depressed monocyte and T-lymphocyte cytokine production. The extent of the surgical procedure had a differential immunosuppressive impact on Th2-type but not on Th1-type cell activity, indicating that the two Th pathways were downregulated through distinct mechanisms. Preoperative interferon-gamma determination would be useful to anticipate the occurrence of postoperative major infectious complications.

Survival benefit of cardiopulmonary bypass support in bilateral lung transplantation for emphysema patients

BACKGROUND

This study is designed to examine a possible association of cardiopulmonary bypass (CPB) support and outcome of lung transplantation in a well-balanced group of emphysema patients.

METHODS

We performed a retrospective analysis of 62 consecutive primary bilateral lung transplantations for emphysema. Risk factors for their possible association with patient survival were analyzed by multivariate logistic regression.

RESULTS

The use of CPB support was associated with improved survival (odds ratio=0.25; P=0.038). The actuarial survival at 1 year was 97% for patients treated with CPB and 77% for patients treated without CPB support. In 28 patients (45%), 2 human leukocyte antigen (HLA)-DR mismatches between donor and recipient occurred, whereas 34 patients had 0 or 1 HLA-DR mismatches. The use of CPB support in the group with two HLA-DR mismatches was associated with improved survival (odds ratio=0.06; P=0.020). This association was not present in the group with 0 or 1 HLA-DR mismatches.

CONCLUSIONS

These results demonstrate a significant survival benefit of CPB support during bilateral lung transplantation in emphysema patients. The difference in survival benefit of CPB support between the patients with 0 or 1 HLA-DR mismatches and the patients with 2 HLA-DR mismatches indicates that the immunosuppressive effect of CPB support might be responsible for this survival benefit. The underlying immunological mechanism might be important in the future treatment of organ transplantation.

Newborn patients exhibit an unusual pattern of interleukin 10 and interferon gamma serum levels in response to cardiac surgery

OBJECTIVE

The aim of this study was to determine the clinical significance of serum levels of interleukin 10 and interferon gamma in pediatric patients undergoing cardiopulmonary bypass.

METHODS

We divided the patients into 2 groups: 8 neonates and 19 non-newborn children. Interleukin 10 and interferon gamma serum levels were quantified before sternotomy, at admission to the pediatric intensive care unit (30 minutes postoperatively), 24 hours after the onset of the operation, and 3 days after the operation.

RESULTS

Newborn patients displayed significantly greater amounts of serum interleukin 10 than older children, not only in regard to the peak level achieved but also at every postoperative time point analyzed. In contrast, no significant changes in interferon gamma serum levels were observed in neonates at any time point, whereas non-newborn pediatric patients showed a significant increase in interferon gamma serum concentrations immediately after the operation. This unusual pattern of cytokine response in newborn patients was not associated with modifications in cortisol serum levels. Furthermore, although neonates had significantly different surgical and clinical variables than did the non-newborn pediatric patients, the variation in interleukin 10 production in neonates could not be accounted for by differences in the magnitude of surgical injury. In the group of neonates, there were significant positive correlations between peak interleukin 10 serum levels and both partial pressure of arterial oxygen/fraction of inspired oxygen ratio and postoperative body weight gain.

CONCLUSIONS

Newborn patients undergoing cardiopulmonary bypass exhibit a distinctive biologic response pattern characterized by high levels of serum interleukin 10 without changes in serum interferon gamma. This cytokine imbalance could have potential clinical implications.

The effects of aprotinin and steroids on generation of cytokines during coronary artery surgery

OBJECTIVE

To compare the efficacy of aprotinin and methylprednisolone in reducing cardiopulmonary bypass (CPB)-induced cytokine release, to evaluate the effect of myocardial cytokine release on systemic cytokine levels, and to determine the influence of cytokine release on perioperative and postoperative hemodynamics.

DESIGN

Prospective, randomized clinical trial.

SETTING

University teaching hospital and clinics.

PARTICIPANTS

Thirty patients undergoing elective coronary artery bypass graft surgery.

INTERVENTION

Patients were randomly allocated into groups treated with aprotinin (n = 10) or methylprednisolone (n = 10) or into an untreated control group (n = 10). Aprotinin-treated patients received aprotinin as a high-dose regimen (6 x 10(6) KIU), and methylprednisolone-treated patients received methylprednisolone (30 mg/kg intravenously) before CPB.

MEASUREMENTS AND MAIN RESULTS

Patients were analyzed for hemodynamic changes and alveolar-arterial PO2 difference (AaDO2) until the first postoperative day. Plasma levels of proinflammatory cytokines (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, IL-6, and IL-8) were measured in peripheral arterial blood immediately before the induction of anesthesia, 5 minutes before CPB, 3 minutes after the start of CPB, 2 minutes after the release of the aortic cross-clamp, 1 hour after CPB, 6 hours after CPB, and 24 hours after CPB; and in coronary sinus blood immediately before CPB and 2 minutes after the release of the aortic cross-clamp. The hemodynamic parameters did not differ among the groups throughout the study. After CPB, AaDO2 significantly increased (p < 0.05) in all groups. A significant decrease in AaDO2 was observed in aprotinin-treated patients at 24 hours after CPB compared with the other groups (p < 0.05). TNF-alpha level from peripheral arterial blood significantly increased in control patients 1 hour after CPB (p < 0.01) and did not significantly increase in methylprednisolone-treated patients throughout the study. In all groups, IL-6 levels increased after the release of the aortic cross-clamp and reached peak values 6 hours after CPB. At 6 hours after CPB, the increase in IL-6 levels in methylprednisolone-treated patients was significantly less compared with levels measured in control patients and aprotinin-treated patients (p < 0.001). In control patients, IL-8 levels significantly increased 2 minutes after the release of the aortic cross-clamp (p < 0.05), and peak values were observed 1 hour after CPB (p < 0.01). IL-8 levels in control patients were significantly higher compared with patients treated with aprotinin and patients treated with methylprednisolone 1 hour after CPB (p < 0.05).

CONCLUSION

This study showed that methylprednisolone suppresses TNF-alpha, IL-6, and IL-8 release; however, aprotinin attenuates IL-8 release alone. Methylprednisolone does not produce any additional positive hemodynamic and pulmonary effects. An improved postoperative AaDO2 was observed with the use of aprotinin.

Changes in T-cell receptor subsets after cardiac surgery in children

T cells are divided into two subsets, alphabeta and gammadelta, according to the T-cell receptor (TCR) expressed. Recent findings indicate that gammadelta T cells serve as the first defense against microbial pathogens, and represent a link between innate and acquired immunity. We conducted a study to investigate the changes in circulating TCR subsets after cardiac surgery in children. Blood samples from 24 children who underwent cardiac surgery with cardiopulmonary bypass (CPB) were collected serially to analyze TCR subsets by flow cytometry. The alphabeta T cells reached a nadir on postoperative day (POD) 1, but recovered to pre-CPB levels on POD 3. On the other hand, the gammadelta T cells decreased after CPB and did not recover to pre-CPB levels even after POD 7. The alphabeta/gammadelta T-cell ratio was increased after POD 3. In children, gammadelta T cells recover more slowly than alphabeta T cells after cardiac surgery. These changes in TCR subsets may contribute to postoperative immunosuppression.

Cytokines and pediatric open heart surgery with cardiopulmonary bypass

It is well known that, subsequent to cardiopulmonary bypass, and particularly in children, an inflammatory response within the body can often result in a characteristic syndrome. Recently, it has been suggested that this phenomenon is due to a systemic inflammatory response, with significant involvement of cytokines. With this in mind, we investigated the behavior of tumour necrosis factor-alpha and interleukin-6 during the operative and in the immediate postoperative period in a group of children submitted to open heart surgery. We investigated any possible relation between the levels of these cytokines in the serum and the length of cardiopulmonary bypass, with the serum levels of lactate, and with the extent of use of inotropic drugs in postoperative period. The cytokines were measured in samples withdrawn after induction of anesthesia, after 10 minutes of cardiopulmonary bypass, after re-establishment of circulation, and then 2 and 24 hours after the end of cardiopulmonary bypass. The levels of tumour necrosis factor-alpha and interleukin-6 increased between the beginning and at two hours of the end of cardiopulmonary bypass. There was no correlation between the levels of these cytokines in the serum and the length of cardiopulmonary bypass, although there was a positive relation between levels of interleukin-6 and lactate in samples withdrawn at two hours of the end of bypass, and the measured levels of the cytokines correlated with the extent of inotropic drugs employed in the postoperative period.

The effect of clonidine pretreatment on the perioperative proinflammatory cytokines, cortisol, and ACTH responses in patients undergoing total abdominal hysterectomy

We investigated the hypothesis that oral clonidine premedication would decrease the release of proinflammatory cytokines interleukin (IL)-6, IL-1beta, and tumor necrosis factor-alpha, and stress hormones cortisol and adrenocorticotropic hormone (ACTH), in patients who underwent total abdominal hysterectomy. Twenty patients were randomly assigned to one of two groups: the control group received no premedication, whereas the treatment group received clonidine 0.15 mg oral dose 90 min before surgery. Venous blood samples were obtained at preinduction time and immediately, 1, and 3 h after the start of surgery. IL-6 increased significantly at 3 h, and cortisol and ACTH at 1 and 3 h after the start of surgery compared with the baseline values within both groups. IL-1beta levels decreased at all times compared with the baseline value in the control group. In the comparison study between the control group and the clonidine group, there was a significant decrease in IL-6 level 3 h after the start of surgery and IL-1beta at preinduction time in the clonidine group, whereas there were no changes in tumor necrosis factor-alpha, cortisol, and ACTH levels. These results show that clonidine modulates the IL-6 response related to surgical stress.

IMPLICATIONS

We assessed the effect of the alpha(2)-adrenoreceptor agonist clonidine on the immunoendocrine activity during the perioperative period. Clonidine 0.15 mg given as oral premedication resulted in the reduced Interleukin-6 production in response to total abdominal hysterectomy.

The preoperative administration of lentinan ameliorated the impairment of natural killer activity after cardiopulmonary bypass

The aim of this study was to determine whether the preoperative administration of lentinan, which is used clinically to activate T cell function in cancer patients, prevents the impairment of lymphocyte function after cardiopulmonary bypass (CPB). A total of 25 adults undergoing coronary artery bypass grafting were enrolled in this study. Lentinan (2 mg) was given to 10 randomly selected patients 7 d before surgery, while the other 15 patients were considered as a control. The white blood cell count, percentage of lymphocytes, subsets of lymphocytes, and natural killer cell activity were measured preoperatively, immediately after CPB and 1, 3, and 6 d after surgery. The white blood cell counts and the percentage of lymphocytes were not significantly different between the two groups; however, the percentage of CD4-positive cells in the lentinan group recovered to normal more rapidly than in the control group. Although natural killer cell activity was impaired in the control group after CPB, it maintained a nearly normal level in the lentinan group. The preoperative administration of lentinan for patients undergoing CPB ameliorated the impairment of natural killer activity and promoted the rapid recovery of CD4-positive cells.

Cimetidine reduces impairment of cellular immunity after cardiac operations with cardiopulmonary bypass

OBJECTIVE

Depressive effects of cardiopulmonary bypass on cell-mediated immune responses may lead to postoperative infectious complications. We previously reported that cimetidine reduced postbypass depression of the cytotoxic activity of natural killer cells. This study evaluated cimetidine as an agent to preserve cellular immunity after cardiac operations.

METHODS

In a prospective randomized study, 20 patients were divided into two groups of equal size. Cimetidine-group patients received 400 mg of cimetidine intravenously before bypass and a 33 mg/hr intravenous infusion of cimetidine after the operation, continuing until the fifth postoperative day. Control-group patients received conventional perioperative therapy. Lymphocyte subsets, natural killer cell activity, percentage of CD56+CD16+ (percentage of natural killer cells), and percentage of CD11b+CD8+ (percentage of suppressor T lymphocytes) were measured perioperatively.

RESULTS

Although temporary postoperative reductions in percentages of CD3+, CD4+, and CD56+CD16+ cells were observed in both groups, CD8+ percentages on postoperative day 1 and CD11b+CD8+ percentages on postoperative days 1 and 3 in the cimetidine group were significantly lower compared with those in the control group (p = 0.01,p = 0.004, andp = 0.02, respectively). Temporary postoperative reduction of natural killer cell activity was also observed in both groups, but the natural killer cell activity on postoperative day 1 in the cimetidine group (17.1%) was significantly higher (p = 0.02) than that in the control group (8.20%).

CONCLUSIONS

Cimetidine counteracts depressive effects of cardiopulmonary bypass on cell-mediated immunity and may possibly reduce postoperative susceptibility to infection.

Interleukin-1, interleukin-1 receptors and interleukin-1 receptor antagonist

IL-1 (IL-1 alpha or IL-1 beta) is the prototypic "multifunctional" cytokine. Unlike the lymphocyte and colony stimulating growth factors, IL-1 affects nearly every cell type, and often in concert with other cytokines or small mediator molecules. Although some lymphocyte and colony stimulating growth factors may be therapeutically useful, IL-1 is a highly inflammatory cytokine and the margin between clinical benefit and unacceptable toxicity in humans is exceedingly narrow. In contrast, agents that reduce the production and/or activity of IL-1 are likely to have an impact on clinical medicine. In support of this concept, there is growing evidence that the production and activity of IL-1, particularly IL-1 beta, are tightly regulated events as if nature has placed specific "road blocks" to reduce the response to IL-1 during disease. In addition to controlling gene expression, synthesis and secretion, this regulation extends to surface receptors, soluble receptors and a receptor antagonist. Investigators have studied how production of the different members of the IL-1 family is controlled, the various biological activities of IL-1, the distinct and various functions of the IL-1 receptor (IL-1R) family and the complexity of intracellular signaling. Mice deficient in IL-1 beta, IL-1 beta converting enzyme (ICE) and IL-1R type I have also been studied. Humans have been injected with IL-1 (either IL-1 alpha or IL-1 beta) for enhancing bone marrow recovery and for cancer treatment. The IL-1 specific receptor antagonist (IL-1Ra) has also been tested in clinical trials.

Thymopentin and splenopentin as immunomodulators. Current status

Splenopentin (SP-5, Arg-Lys-Glu-Val-Tyr) and thymopentin (TP-5, Arg-Lys-Asp-Val-Tyr) are synthetic immunomodulating peptides corresponding to the region 32-34 of a splenic product called splenin (SP) and the thymic hormone thymopoietin (TP), respectively. TP was originally isolated as a 5-kDa (49-amino acids) protein from bovine thymus while studying effects of the thymic extracts on neuromuscular transmission and was subsequently observed to affect T cell differentiation and function. TP I and II are two closely related polypeptides isolated from bovine thymus. A radioimmunoassay for TP revealed a crossreaction with a product found in spleen and lymph node. This product, named splenin, differs from TP only in position 34, aspartic acid for bovine TP and glutamic acid for bovine splenin and it was called TP III as well. Synthetic pentapeptides (TP-5) and (SP-5), reproduce the biological activities of TP and SP, respectively. It is now evident that various forms of TPs were created by proteolytic cleavage of larger proteins during isolation. cDNA clones have been isolated for three alternatively spliced mRNAs that encodes three distinct human T cell TPs. The immunomodulatory properties of TP, SP, TP-5, SP-5 and some of their synthetic analogs reported in the literature have been briefly reviewed.

Alterations of the cytokine network in patients undergoing cardiopulmonary bypass

Cardiovascular surgery using extracorporeal circulation causes a systemic inflammatory response which often results in severe organ dysfunction and increased postoperative mortality. Advances in knowledge about the interactions of cytokines involved in the response to cardiopulmonary bypass (CPB) may improve the outcome of patients undergoing cardiac surgery. The purpose of our study was to investigate the fluctuations in cytokine production, during and after CPB. In 24 patients undergoing elective coronary artery bypass grafting, plasma levels of interleukins IL-2, IL-6, IL-10 and IL-12, soluble IL-2-receptor (sIL-2R), and transforming growth factor-beta (TGF-beta) were measured at eight time points before, during and after CPB, using a standardized enzyme-linked immunosorbant assay technique. There was a significant increase in plasma levels of IL-10, IL-6 and TGF-beta after weaning off CPB. The IL-2 plasma levels decreased after the onset of CPB until 24 h postoperatively (p < 0.05). Concentrations of sIL-2R decreased 20 min after the start of CPB until the end of the operation (p < 0.05). In the postoperative course, sIL-2R levels increased, with peak values 48 h after the end of the surgical procedure. The IL-12 levels decreased after weaning off CPB (p < 0.05) until 6 h postoperatively. The results of our study demonstrate an intraoperative-predominant immunosuppression, followed by an early postoperative immunological activation, combined with a distinct acute phase response.

Interindividual variations in cytokine levels following cardiopulmonary bypass

Cardiopulmonary bypass (CPB) is associated with an inflammatory response, mainly caused by the trauma of surgery, contact of blood with the artificial surface of the circuit, and reperfusion injury, resulting in increased capillary permeability, respiratory distress, low cardiac output, and multiorgan failure. The inflammatory reaction includes an activation of the humoral and cellular immune system with enhanced release of cytokines. The present study focused on the effect of CPB on the time course of pro- and anti-inflammatory cytokines. In 20 patients undergoing coronary artery bypass grafting, the plasma concentration of interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta, IL-2, IL-4, IL-6, IL-8, and IL-10 was investigated pre-, intra-, and postoperatively by enzyme-linked immunosorbent assay technique. With the exception of IFN-gamma, all the other cytokines could be detected in the patients plasma. However, neither TNF-alpha nor IL-1 beta and IL-2 revealed significant changes in concentration during the investigated time period. In contrast, IL-6 and IL-8 levels peaked early postoperatively, reaching median concentrations of 430 pg/ml (221 pg per ml/558 pg per ml; lower/upper quartiles, respectively) and approximately 12 pg/ml (0/17 pg/ml; lower/upper quartiles, respectively). IL-4 and IL-10, respectively, revealed maximal concentrations of approximately 2 pg/ml (0/39 pg/ml; lower/upper quartiles, respectively) and 208 pg/ml (76 pg per ml/380 pg per ml; lower/upper quartiles, respectively) immediately after protamine administration, preceding the maximal concentration of IL-6. The degree of the observed modulation of cytokine patterns during and after CPB seemed to be patient-dependent, since large interindividual variations in cytokine levels were observed, not only preoperatively, but especially during and following CPB. However, IL-6 and IL-10 showed the least interindividual variations, suggesting that these cytokines may give reliable information regarding modulation of the immune response following CPB and its consequences for the patient's outcome.

A study of the effects of extracorporeal circulation on the immunologic system of humans

OBJECTIVES

The objectives of this study were to quantify the immunosuppressive effects of cardiopulmonary bypass (CPB) and to identify mechanisms responsible for the postoperative immunosuppression of patients undergoing cardiac surgery.

DESIGN

A prospective study from 20 consecutive patients.

SETTING

The same team operated on all patients in a major teaching hospital, and the immunologic tests were performed in the hospital's hematology laboratory.

PARTICIPANTS

Twenty patients were studied who had consented to participate in the study.

INTERVENTIONS

All patients underwent valve replacement under general anesthesia.

MEASUREMENT AND MAIN RESULTS

The changes in the white blood cell count (WBC), in the B, T, T4, T8 lymphocytes, the concentrations of C-reactive protein (CRP), a1-antitrypsin (A1AT), a2-macroglobulin (A2MG), C3, C4 immunoglobulin A (IgA), IgM, IgG, Kappa (K), and lambda (L) chains were studied. The postoperative immune response was expressed with (1) increased mean axillary temperature (37.5 degrees +/- 0.62 degrees) in the first postoperative 24 hours; (2) increase of WBC (p < 0.001) and T8 (p < 0.01); (3) reduction of C3 (p = 0.01) and A2MG (p < 0.01); (4) reduction of IgA (p < 0.001) and IgG, K, L chains (p < 0.01); and (5) reduction of T (p < 0.01) and T4 (p < 0.01). In the first 24 hours postoperatively, B cells were increased (81%) together with CRP (p < 0.01) and A1AT.

CONCLUSIONS

The observed immune alterations were mostly of no immunologic origin and were related to hemodilution and inflammation together with an immunosuppressive effect of trauma and stress.

Impact of left ventricular dysfunction on cytokines, hemodynamics, and outcome in bypass grafting

BACKGROUND

Although patients with reduced left ventricular ejection fraction undergoing cardiac operation experience a higher rate of perioperative complications, the contribution of proinflammatory cytokines released during extracorporeal circulation is not well defined.

METHODS

We compared arterial and mixed venous levels of interleukin-6, tumor necrosis factor-alpha, soluble interleukin-2 receptor, and interleukin-2 at 10 points in time (24 hours before until 48 hours after extracorporeal circulation) in 21 patients with an ejection fraction of less than 0.45 (study group) to 15 patients with an ejection fraction of more than 0.55 (control group) undergoing elective coronary artery bypass grafting. The study and control group differed with regard to left ventricular ejection fraction (0.37 +/- 0.05 versus 0.66 +/- 0.11, p < 0.05) and reperfusion time (35 +/- 42 minutes versus 18 +/- 4 minutes, p = 0.07), but not age, sex, vessel involvement, number of grafts performed, cross-clamp time, extracorporeal circulation time, core temperature, and duration of ventilation.

RESULTS

Six patients in the study group required mechanical support and 1 died. There were no complications in the control group. In the study group, there were higher preoperative interleukin-2 and tumor necrosis factor-alpha levels and a higher maximum cytokine response to extracorporeal circulation for interleukin-2, soluble interleukin-2 receptor, interleukin-6, and tumor necrosis factor-alpha (all p < 0.05). Interleukin-6 correlated with duration of extracorporeal circulation, dose of norepinephrine and epinephrine support, pulmonary capillary wedge pressure, mean pulmonary arterial pressure, right atrial pressure, heart rate, cardiac index, and inversely with systemic vascular resistance. Interleukin-6 was highest in patients with complications. Arterial and venous cytokine levels correlated closely.

CONCLUSIONS

Preoperative left ventricular dysfunction is associated with a higher degree of proinflammatory cytokine release during elective coronary artery bypass grafting. This response is associated with impaired hemodynamics and a higher incidence of perioperative complications.

Aprotinin diminishes inflammatory processes

Many of the recent reports concerning cytokine levels in cardiopulmonary bypass have documented changes in the levels of these trauma indicators. In the present report, we also document their levels but in the presence of Aprotinin. Aprotinin is a protease inhibitor used not only to diminish bleeding, but also to diminish elements of the diffuse inflammatory response associated with this type of surgery. We report in plasma obtained from 20 patients that initially interleukin-8 (IL-8) levels (53.4 +/- 7 pg/ml) plasma to 185.5 +/- 30 pg/ml) increased 20 min from the start of surgery. This is followed by IL-6 (5.3 +/- 1.1 to 200 +/- 50 pg/ml) peaking 15 h post surgery. These levels return to normal by day 3 postop. IL-1 beta and tumour necrosis factor (TNF) levels remained at baseline for the observation period. Associated with these changes in cytokine levels is the activity state of immunocytes (granulocytes and monocytes) noted by conformational changes obtained from computer-assisted microscopy. The cells exhibited an ameboid conformation and became mobile (67%), peaking at 120 min after surgery began and returned to a more rounded conformation with only 6% exhibiting the ameboid conformation by day three. In in-vitro experiments, where immunocytes not exposed to cardiopulmonary bypass were exposed to plasma obtained from patients having undergone this surgery, their activity level rose to 65%. In the same experiment, when Aprotinin was added to the cell-plasma mixture, the level of activation dramatically dropped to 25%. Thus, aprotinin was found at high doses to lower cytokine and cellular activation associated with the acute inflammatory responses of cardiopulmonary bypass, suggesting that this may be initiated by hyperstimulated immunocytes.

Enzymatic cleavage of thymopoietin oligopeptides by pancreatic and intestinal brush-border enzymes

The intestinal enzymatic degradation of the immunomodulating peptides thymotrinan (TP3), thymocartin (TP4), and thymopentin (TP5), three oligopeptides derived from the naturally occurring thymus hormone thymopoietin, was investigated to evaluate their potential for peroral drug delivery. In the presence of brush-border membrane vesicles, crude pancreas extract and everted rings from duodenum, jejunum, ileum, and colon, all peptides were shown to be degraded both by pancreatic enzymes and brush-border aminopeptidases. Degradation clearances (Cldeg) of TP3, TP4, and TP5 were calculated for a quantitative comparison of peptide stability. In the presence of crude pancreas extract, there was a rapid degradation of TP5 (Cldeg 17.9 ml/min) in comparison with TP3 and TP4 (Cldeg 0.95 and 0.56 ml/min, respectively, at 0.2 mM peptide concentration) caused by the cleavage of the C-terminal tyrosine by carboxypeptidase A, whereas TP3 and TP4 underwent hydrolysis by aminopeptidase N. In the presence of brush-border membrane vesicles, the degradation clearances were 3.9, 3.1, and 2.4 ml/min at 0.2 mM concentrations of TP4, TP5, and TP3, respectively. The clearance of all peptides was lowered with increasing peptide concentrations, indicating saturable degradation processes. The degradation of the thymopoietin oligopeptides in the presence of brush-border membrane enzymes was exclusively catalyzed by aminopeptidase N. The degradation of all peptides was highly dependent on the intestinal segment, with the lowest degradation clearance observed in the colon.

Heparin bonding of bypass circuits reduces cytokine release during cardiopulmonary bypass

BACKGROUND

Heparin bonding of the cardiopulmonary bypass (CPB) pump circuit decreases complement activation and fibrinolysis. It is not known whether inflammatory cytokines produced during CPB can also be modulated by the more biocompatible heparin-coated circuit.

METHODS

This initial study evaluated the impact of heparin-bonded CPB circuits on production of the cytokines interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-a), IL-6, and IL-8 in adults undergoing complex cardiac operations with prolonged CPB. Twenty patients had blood samples drawn immediately before and at hourly intervals after the start of CPB using either a conventional oxygenator and circuit (n = 14) or a covalently bonded heparin oxygenator and circuit (n = 6). Levels of IL-1, TNF-a, IL-6, and IL-8 were measured in all serum samples using a "sandwich" enzyme-linked immunosorbent assay.

RESULTS

The levels of IL-6 and IL-8 increased in a time-dependent fashion in both groups, but the response was significantly less over time in the heparin-bonded group (p < 0.05) for both IL-6 and IL-8. Levels of IL-1 and TNF-a were not significantly elevated with lengthening bypass interval in either group.

CONCLUSIONS

These data indicate that the use of heparin-coated bypass pump circuits results in lower serum levels of the inflammatory cytokines IL-6 and IL-8 than standard circuits. Biocompatible materials that decrease the inflammatory response to CPB may ultimately reduce the morbidity associated with cardiac operations.

Gut mucosal ischemia during normothermic cardiopulmonary bypass results from blood flow redistribution and increased oxygen demand

Impaired gut mucosal perfusion has been reported during cardiopulmonary bypass. To better define the adequacy of gut blood flow and oxygenation during cardiopulmonary bypass, we measured overall gut blood flow and ileal mucosal flow and their relationship to mucosal pH, mesenteric oxygen delivery and oxygen consumption in immature pigs (n = 8). Normothermic, noncross-clamped, right atrium-to-aorta cardiopulmonary bypass was maintained at 100 ml/kg per minute for 120 minutes. Animals were instrumented with an ultrasonic Doppler flow probe on the superior mesenteric artery, a mucosal laser Doppler flow probe in the ileum, and pH tonometers in the stomach, ileum, and rectum. Radioactive microspheres were injected before and at 5, 60, and 120 minutes of cardiopulmonary bypass for tissue blood flow measurements. Overall gut blood flow significantly increased during cardiopulmonary bypass as evidenced by increases in superior mesenteric arterial flow to 134.1% +/- 8.0%, 137.1% +/- 7.5%, 130.3% +/- 11.2%, and 130.2% +/- 12.7% of baseline values at 30, 60, 90, and 120 minutes of bypass, respectively. Conversely, ileal mucosal blood flow significantly decreased to 53.6% +/- 6.4%, 49.5% +/- 6.8%, 58.9% +/- 11.6%, and 47.8% +/- 10.0% of baseline values, respectively. Blood flow measured with microspheres was significantly increased to proximal portions of the gut, duodenum and jejunum, during cardiopulmonary bypass, whereas blood flow to distal portions, ileum and colon, was unchanged. Gut mucosal pH decreased progressively during cardiopulmonary bypass and paralleled the decrease in ileal mucosal blood flow. Mesenteric oxygen delivery decreased significantly from 67.0 +/- 10.0 ml/min per square meter at baseline to 42.4 +/- 4.6, 44.9 +/- 3.5, 46.0 +/- 3.6, and 42.9 +/- 3.9 ml/min per square meter at 30, 60, 90, and 120 minutes of bypass. Despite the decrease in mesenteric oxygen delivery, mesenteric oxygen consumption increased progressively from 10.8 +/- 1.4 ml/min per square meter at baseline to 13.4 +/- 1.2, 15.9 +/- 1.2, 16.7 +/- 1.4, and 16.6 +/- 1.54 ml/min per square meter, respectively. We conclude that gut mucosal ischemia during normothermic cardiopulmonary bypass results from a combination of redistribution of blood flow away from mucosa and an increased oxygen demand.

Blood anesthesia for cardiopulmonary bypass

Cardiopulmonary bypass (CPB) causes bleeding and thrombotic complications, fluid retention and temporary dysfunction of every organ system. This morbidity of CPB is primarily do to activation of blood proteins and cells by contact with nonendothelial cell surfaces of the wound and biomaterials of the extracorporeal perfusion circuit. CPB is not possible without heparin, yet heparin is not an ideal anticoagulant and does not prevent activation of at least five plasma protein systems and five blood cells. Stimulation of these blood elements produces over 25 vasoactive substances that alter vascular tone, capillary permeability, and cardiac myocyte contractility. In addition, CPB produces showers of microemboli that pass filters to obstruct arterioles and precapillaries to produce necrosis of widely dispersed, small groups of cells. Attempts to develop nonthrombogenic synthetic materials have failed; only the endothelial cell is nonthrombogenic and achieves this property by active metabolic processes. Although some biomaterials are less thrombogenic than others, all activate blood elements to initiate clotting and the body's defense reaction. The concept of "blood anesthesia" envisions the use of reversible inhibitors of key blood reactions to temporarily prevent activation of blood elements during CPB. If the initial reactions of blood with nonendothelial surfaces are blocked, production of many vasoactive substances and microemboli by CPB is suppressed. This conserves blood elements that are normally consumed during CPB and makes them available after the inhibitor is reversed. Effective, reversible inhibitors of platelets are entering clinical trials; reversible inhibitors of other key blood relations are being developed and tested at a rapid rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiopulmonary bypass with adequate flow and perfusion pressures prevents endotoxaemia and pathologic cytokine production

Endotoxin and cytokine inflammatory mediators comprise the afferent and efferent limbs of the 'acute phase response'. During cardiopulmonary bypass (CPB) there may be gut translocation of endotoxin and contact activation of lymphocytes. It has been hypothesized that the haemodynamic instability encountered following CPB is caused by the 'acute phase response'. In this study we attempted to quantify the acute phase response in patients undergoing open-heart surgery and determine the influence of these cytokines on perioperative morbidity. Four perioperative blood samples were drawn from 20 consecutive patients undergoing coronary artery bypass grafting (CABG). These samples were assayed for endotoxin and four cytokines. In all cases the cardiac index was maintained > 2.4 l/min/m2 during nonpulsatile normothermic bypass (37 degrees C) and > 1.8 l/min/m2 during nonpulsatile hypothermic bypass (28 degrees C), and the perfusion pressure > 60 mmHg. Endotoxin was not detected in any of the test samples despite positive nonpatient controls. Interleukin 6 (IL-6) and tumour necrosis factor (TNF) were not detected despite an assay sensitivity of 80 and 10 pg/ml, respectively. TNF was detectable with an assay sensitivity of 0.5 pg/ml although there were no significant differences within the group. Interleukin 1 (IL-1) was detected (range = 0.98 - 9.09 ng/ml) in patients and again there were no trends within the group. The platelet activating factor (PAF) values peaked at crossclamp release (1.3 ng/ml versus a baseline of 0.2 ng/ml); however, there was no significant difference within the study.