Regulation of acute phase response after cardiopulmonary bypass by immunomodulation

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.

Perioperative Levels of Tumor Necrosis Factor-α Correlate With Outcomes in Children and Adults With Tetralogy of Fallot Undergoing Corrective Surgery

Background:

Previous studies reporting on tumor necrosis factor-α (TNF-α) as a marker of inflammatory response (IR) in patients with congenital heart disease were limited by small sample size and variability in diagnosis. We report perioperative changes in TNF-α levels and their correlation with preoperative factors and clinical outcomes in a large homogenous group of patients with tetralogy of Fallot (TOF) undergoing definitive repair at a tertiary care center.

Methods:

A total of 167 patients were divided into four groups on the basis of age. Group 1 included infants less than 1 year, group 2 included children between 1 and 12 years, group 3 included adolescents between 12 and 18 years, and group 4 included adults more than 18 years of age. Serum TNF-α levels were measured at three time points and correlated with perioperative variables.

Results:

The baseline TNF-α level correlated with patients’ nutritional status and degree of cyanosis in all four groups. The magnitude of IR in the postcardiopulmonary bypass (post-CPB) period as measured by TNF-α level was much higher and correlated more consistently with adverse clinical outcomes in the younger age group (groups 1 and 2). On multivariable analysis; age at operation, preoperative degree of hypoxemia and TNF-α levels were found to be independent predictors of clinical outcomes.

Conclusion:

We demonstrated a rise in serum TNF-α levels in patients with TOF undergoing definitive repair on CPB, which correlated with preoperative severity of cyanosis, nutritional status, and adverse clinical outcomes. The TNF-α levels may be monitored to identify cyanotic patients at an increased risk of exhibiting augmented IR to CPB.

Cytokine secretion after cardiac surgery and its relationship to postoperative fever

A relationship between the inflammatory response to cardiopulmonary bypass (CPB) and fever after coronary artery bypass graft surgery (CABG) is assumed, but has not been studied. Therefore, we sought to assess the temporal pattern of cytokines' elevation and its association with post-CABG fever. In 355 primary elective CABG patients, serum cytokines (TNF-alpha, IL-1ra, IL-1beta, IL-6, and IL-8) were measured before surgery, at cessation of CPB and 2.5, 4.5, 24, and 48 h post-CPB. Fever was defined as a temperature >38 degrees C. TNF-alpha, IL-1beta and IL-8 peaked within the first 2.5 h after bypass, returning to near normal levels by 24h and increasing again by 48 h. IL-6 peaked early after bypass and remained elevated at 48 h. IL-1ra was elevated early, before returning to baseline by 24 h. Postoperative fever developed in 27% of patients. Increased IL-6 levels and male gender were significant predictors of fever (C-index=0.68; p=0.0003). No other cytokine showed a significant association with fever development. Of note is the previously undescribed bimodal pattern of cytokines' secretion after CABG. The association of fever with IL-6 levels suggests inflammatory mediation.

Tumor necrosis factor and clinical and metabolic courses after cardiac surgery in children

OBJECTIVE

This study was undertaken to determine the relationship between plasma tumor necrosis factor concentrations and hemodynamic and metabolic parameters during the postoperative clinical course in children undergoing cardiac surgery.

METHODS

Tumor necrosis factor levels of 10 consecutive children undergoing surgery for repair of congenital heart defects were analyzed in blood samples drawn at predetermined time points during surgery and up to 24 hours thereafter. Clinical data were collected at these times for correlation to tumor necrosis factor levels.

RESULTS

All the patients survived. Tumor necrosis factor was detected in all 10 children. Tumor necrosis factor levels declined after induction of general anesthesia (201 +/- 65 pg/mL) steadily decreasing during surgery, reaching 80 +/- 50 pg/mL at 24 hours after the operation. Tumor necrosis factor levels were found to be inversely correlated with mean blood pressure values and indicators of acidosis (bicarbonate levels and base excess, P <.03). They were not correlated with the durations of cardiopulmonary bypass and aortic crossclamping.

CONCLUSIONS

Tumor necrosis factor released into the circulation during and after pediatric cardiac surgery under cardiopulmonary bypass may be related to the hemodynamic and acid-base changes observed after cardiac surgery. Elucidation of the relationship between tumor necrosis factor and patient outcome in high-risk patients awaits further studies.

Interferon-gamma modifies cytokine release in vitro by monocytes from surgical patients

BACKGROUND

Treatment with interferon-gamma (IFN-gamma), a key mediator for adequate forward-regulatory monocyte immune capability, has been advocated to overcome posttraumatic mononuclear leukocyte paralysis. Conversely, IFN-gamma also is a potent proinflammatory mediator contributing to capillary leakage in sepsis-driven organ failure. The objective of this investigation was to further define the potential of IFN-gamma as a modifier of monocyte activity before and after injury.

METHODS

Whole blood samples from 19 patients (7 female and 12 male patients; age, 68 +/- 5 years) before and after cardiac surgery with extracorporeal circulation were incubated under continuous rotation with lipopolysaccharide for 12 hours in the presence or absence of human recombinant IFN-gamma. Pro- and anti-inflammatory cytokines were determined in the plasma.

RESULTS

Lipopolysaccharide-induced release of tumor necrosis factor-alpha, interleukin (IL)-6, IL-12, and IL-1Ra, and prostaglandin E2 was clearly augmented with IFN-gamma most strikingly postoperatively (p < 0.05). There was no effect on IL-1beta, neopterin, and soluble tumor necrosis factor-R release.

CONCLUSION

Thus there is a wide spectrum of IFN-gamma activity on monocyte activation including anti-inflammatory properties. Since cellular preactivation facilitates monocyte reactivity toward IFN-gamma, we conclude that exogenous administration should be effective but must be carried out with great caution in patients with profound inflammation.

Induction of acute-phase reactive substances during open-heart surgery and efficacy of ulinastatin. Inhibiting cytokines and postoperative organ injury

OBJECTIVE

A systemic inflammatory response after open-heart surgery using cardiopulmonary bypass may be responsible for postoperative organ dysfunction. Ulinastatin, a protease inhibitor, plays an important role in host defense under periods of stress.

METHODS

We studied the efficacy of ulinastatin on changes in acute-phase reactive substances during and after open-heart surgery. Patients undergoing open-heart surgery were divided into an ulinastatin group (Group U) and a control group (Group C). In Group U, we introduced 600,000 units of ulinastatin into a priming solution for cardiopulmonary bypass, 300,000 units into a cardiopulmonary bypass circuit at the removal of aortic cross-clamping, and 300,000 units a day for 5 days following surgery.

RESULTS

Immediately after cardiopulmonary bypass, alpha 1-antitrypsin levels decreased significantly in both groups, and increased significantly on the second day after surgery. Ulinastatin levels decreased after cardiopulmonary bypass in Group C. Significantly high levels of ulinastatin were obtained in Group U. Interleukin-6, interleukin-8, and polymorphonuclear elastase were markedly induced, and high levels of plasma concentration continued for several days after surgery. At all sample points, these concentrations in Group U tended to be lower than those in Group C. A significantly positive correlation was seen between the maximum levels of interleukin-8 and polymorphonuclear elastase, but these cytokine and polymorphonuclear elastase levels did not correlate with parameters such as the duration of anesthesia, surgery, cardiopulmonary bypass, or aortic cross-clamping.

CONCLUSIONS

Our study suggests that high-dose ulinastatin administration to maintain a sufficient concentration of circulating protease inhibitors may suppress overinduction of cytokines and polymorphonuclear elastase in open-heart surgery.

Mechanisms of the systemic inflammatory response

The purpose of inflammation is to combat various agents that may injure the tissues. Conditions such as CPB can often cause systemic inflammation and dysfunction of major organs. Pulmonary, renal, myocardial and intestinal function may suffer various degrees of impairment during and after cardiac surgery. Although changes in major organs usually remain clinically insignificant, severe organ failure is not uncommon. The process of systemic inflammation proceeds through activation of serum proteins, activation of leucocytes and endothelial cells, secretion of cytokines, leucocyte-endothelial cell interaction, leucocyte extravasation and tissue damage. Several anti-inflammatory strategies have already been used, some of which have given promising results pertaining to further reduction in the rate of the inflammation-related complications in cardiac surgical patients.

Effect of low-dose methyl prednisolone on serum cytokine levels following extracorporeal circulation

The systemic inflammatory response to cardiopulmonary bypass (CPB) is associated with increased production of cytokines. This systemic inflammatory response characterized by the activation of interleukin-6 (IL-6) and interleukin-8 (IL-8) during and after CPB is well documented. A prospective, randomized, double-blind study was performed so as to understand the effects of low-dose methyl prednisolone sodium succinate (MPSS) on the circulating levels of serum cytokines and clinical outcome. Twenty patients were randomly divided into two groups on the basis of the administration of low-dose (1 mg/kg) MPSS (n = 10) and placebo (n = 10) into the pump prime solution. All patients were scheduled to undergo a primary elective coronary artery bypass grafting operation. Patients receiving concurrent corticosteroids, salicylates, dipyridamol or anticoagulants were excluded from the study. Other exclusion criteria were concurrent chronic obstructive pulmonary disease, chronic renal failure, insulin-dependent diabetes, congestive cardiac failure, peptic ulcer history, prior cardiac operations, recent (in a one-month period) myocardial infarction and steroid dependency. Mild systemic hypothermia (30-32 degrees C, rectal) was assured during the CPB. Four blood samples were drawn from the radial artery catheter immediately before starting CPB (T1), following protamine administration (T2) and at 24 (T3) and 48 h (T4) after completion of CPB. In each sample, creatine kinase-myocardial band (CK-MB), white blood cell (WBC), IL-6 and IL-8 levels were measured. IL-6 and IL-8 concentrations were measured by enzyme immunoassay and enzyme-linked immunoabsorbant assay methods. Serum IL-6 T2 and serum IL-6 T3 levels were significantly higher than IL-6 T1 levels in both groups (p < 0.001) and (p < 0.01), and there was no significant elevation in serum IL-8 levels in either group. Serum IL-6 levels were significantly higher in the placebo group than in the MPSS group at T3 (p < 0.009). There was no significant difference in CK-MB T1 levels between the groups. Although there was no significant difference between CK-MB T1 and T2 levels in the MPSS group, the CK-MB T2 and CK-MB T3 levels were significantly higher than T1 levels in the placebo group (p < 0.001) and (p < 0.05). There was significant elevation of WBC levels at T2 and T3 in both groups without notable difference between the groups (p < 0.05). This study has shown that low-dose MPSS suppresses CPB-induced inflammatory response. Further clinical studies (on larger and higher risk groups) may reveal more information on relations between morbidity and cytokine levels which may have some predictive value on clinical outcome following CPB.

'High dose' aprotinin and heparin-coated circuits: clinical efficacy and inflammatory response

Heparin-coated cardiopulmonary bypass circuits reduce the inflammatory response to cardiopulmonary bypass circuit, improve biocompatibility and may protect the postoperative hemostasic mechanisms in routine coronary bypass operations. 'High-dose' aprotinin reduces bloodloss, transfusion needs, and re-explorations as a result of bleeding, and may have an additional role in reducing the inflammatory response of the body to cardiopulmonary bypass circuit. It has not been established, however, if the addition of a heparin-coated circuit to the intraoperative administration of 'high dose' aprotinin further reduces the whole-body inflammatory response to cardiopulmonary bypass circuit and improves the postoperative clinical course of the patients who are undergoing coronary surgery. Thirty patients undergoing primary elective coronary artery bypass grafting were studied. All the patients received, intraoperatively, the serine-protease inhibitor aprotinin according to the 'Hammersmith' protocol and full heparin dose. Patients were randomly allocated to be treated either with a circuit completely coated with surface-bound heparin (n = 15) or with an uncoated, but otherwise identical, circuit (n = 15). Differences in the clinical course of the two groups of patients, as well as differences in the behavior of hematological and inflammatory (interleukin-6 (IL-6) and C-reactive protein) factors before, during and after bypass, were analyzed. There were no significant differences between the two groups in terms of bleeding and transfusional requirements, the time spent on a ventilator, or in duration of stay in the intensive care unit (ICU). In all patients, a significant increase in the total white blood cell count, neutrophils, serum IL-6 and C-reactive protein occurred in relation to cardiopulmonary bypass. This was not influenced by heparin precoating of the circuit. In addition, there was an increase in the monocyte count during follow-up, and there was a trend towards higher monocyte counts in the patients who were treated with heparin-coated circuits. These results suggest that the addition of a heparin-coated circuit to the intraoperative 'high-dose' aprotinin therapy probably had little influence on the clinical course and on the time-course of the inflammatory parameters of the adult patients undergoing primary coronary surgery with a full heparinization protocol.

Cytokine release during long-term extracorporeal circulation in an experimental model

The objective of this study was to determine the degree of leukocyte activation, as measured by cytokine release, in circulating blood during experimental extracorporeal circulation. Complete in vitro extracorporeal membrane oxygenation (ECMO) circuits were used, and 9 experiments were performed. Whole blood stored at 37 degrees C was used as the control. Blood samples were withdrawn before the start of perfusion and at 24 h of perfusion. Statistically significant releases of interleukin (IL)-1beta, IL-8, and IL-1 receptor antagonist were observed in the perfusion circuits compared to both the control blood and baseline values. Also, increases in plasma tumor necrosis factor (TNF)alpha and IL-6 were seen after 24 h of perfusion although these changes did not reach statistical significance. These results indicate that extracorporeal circulation induced leukocyte activation and cytokine release. These reactions might, as an additional trauma, deteriorate the situation in an already severely ill patient. A search for methods to counteract this untoward activation seems warranted.

Expression of soluble endothelial adhesion molecules in clinical cardiopulmonary bypass

Soluble endothelial adhesion molecule expression in clinical cardiopulmonary bypass (CPB) was investigated. Neutrophil-mediated endothelial injury plays an important role in CPB-induced organ dysfunction. The adhesion of neutrophil to the endothelium is central to this process. It has been well documented that CPB induces neutrophil activation and changes in neutrophil adhesion molecule expression, but the effect of CPB on endothelial cell activation is not known. This study was designed to measure soluble endothelial adhesion molecules during CPB. We made serial measurements (by specific enzyme-linked immunoabsorbent assay) of plasma levels of the soluble endothelial adhesion molecules, ICAM-1 and E-selectin in patients undergoing routine CPB (n = 7) and in a control group (thoracotomy, n = 3). The results show an initial significant decrease during CPB followed by an increase in plasma E-selectin from 29.3 +/- 5.1 ng/ml (mean +/- SEM) prebypass to 34.0 +/- 5.4 ng/ml at 48 h postbypass. Likewise, plasma ICAM-1 significantly decreased during CPB and then increased from 246.3 +/- 38.0 ng/ml before bypass to 324.8 +/- 25.0 ng/ml and 355.0 +/- 23.0 ng/ml at 24 and 48 h after bypass, respectively. The rise in levels is statistically significant (p < 0.05). This study shows a decrease in circulating ICAM-1 and soluble E-selectin during CPB and an increase in their levels at 48 h after CPB.

The balance of pro- and anti-inflammatory cytokines in cardiac surgery

Homeostatic control of the balance of pro- and anti-inflammatory cytokines is important for the maintenance of health. Cardiac surgery, with its intense pro-inflammatory stimulus, constitutes a major challenge to the patient's ability to maintain this balance. Pre- and intraoperative factors influencing the maintenance of cytokine balance are discussed.

The inflammatory response and extracorporeal circulation

Defining the cause of organ and tissue dysfunction associated with the use of perfusion systems will produce methods of prevention or treatment and improve patient outcome. The problem is the plethora of triggers, effectors, and mediators in this process, which can now be measured. Each new measureable compound becomes another biochemical "smoking gun" without physiological data to show any relevance to the human problem. This review critically compares and contrasts the role of certain, largely novel, initiation, amplification, and cytotoxic mechanisms in the inflammatory response of the myocardium and pulmonary systems after a period of cardiopulmonary bypass. The available evidence strongly points to the process being different for each of these tissue beds. These data suggest that ensuring normal lung and heart functions after surgery will require separate therapeutic strategies.

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.

"Low-dose" aprotinin modifies hemostasis but not proinflammatory cytokine release

BACKGROUND

Cytokines are implicated in the pathogenesis of the "whole-body inflammatory response" that may complicate the period after cardiopulmonary bypass (CPB). Low-Dose aprotinin in the pump during CPB has been shown to improve postoperative hemostasis and platelet preservation. We tested the hypothesis that low-dose aprotinin influences the inflammatory reaction (in terms of cytokine release) after CPB.

METHODS

In a prospective, randomized study, 36 patients undergoing elective coronary artery bypass grafting were investigated. Nineteen patients received low-dose aprotinin (2 x 10(6) KIU (280 mg] in the pump), and a control group of 19 did not. Complement activation, cytokine production, leukocyte elastase release. D-dimer level, full blood count, postoperative blood loss, and transfusion requirements were analyzed before, during, and after after CPB.

RESULTS

Interleukin-1 beta was not detected in either group, whereas traces of tumor necrosis factor-alpha were infrequently observed. Plasma elastase, interleukin-6, interleukin-8, and neutrophil count increased (p < 0.001) during and after CPB compared with the baseline levels, reaching a peak at 2 hours after protamine administration in both groups before returning toward baseline at 24 hours. Proinflammatory cytokine markers did not differ significantly (p > 0.1) between the groups throughout the study period. The C5b-9 level increased (p < 0.001) in both groups perioperatively, reaching its peak 15 minutes after protamine. Twenty-four-hour postoperative blood loss was significantly (p < 0.001) reduced in the aprotinin group in association with markedly reduced D-dimer levels (p < 0.001). Patients in the aprotinin group also received significantly less banked blood postoperatively than the control group (p < 0.01).

CONCLUSIONS

Low-dose aprotinin fails to modify proinflammatory cytokine release, yet confers hemostatic improvement through reduced fibrinolysis in patients undergoing routine coronary artery bypass grafting.

The influence of surgery on cytokines in patients with intra-abdominal sepsis

The cytokine cascade which is triggered by severe sepsis may contribute to progressive organ dysfunction and death from sepsis. This cascade may be accentuated by surgery for sepsis and pre-treatment with cytokine blockers could possibly ameliorate the response. This prospective controlled study determined the effect of surgery in 11 haemodynamically stable patients undergoing laparotomy for intra-abdominal sepsis. Serum levels of endotoxin, IL-1, IL-6, IL-8 and TNF-alpha were determined; blood cultures, features of systemic inflammatory response, and organ dysfunction were monitored over the peri-operative period. There was considerable variation in the serum cytokine levels. The preoperative IL-6 levels were significantly elevated in the septic patients and a threefold increase in IL-6 levels occurred in both groups postoperatively. An increase in TNF-alpha did not achieve significance because of high levels in control patients with cancer. Cytokine release which occurs during abdominal surgery is increased in patients with intra-abdominal sepsis.

Immunomodulation: an important concept in modern anaesthesia

This review summarises evidence for immunomodulatory effect of drugs administered peri-operatively. The clinical significance of the balance of pro- and anti-inflammatory cytokines may be seen in certain disease states, for example, meningococcal meningitis and Lyme arthritis. This balance may be altered peri-operatively. Traditionally, these changes are considered to be due to the stress response of surgery, the response to cardiopulmonary bypass, or endotoxaemia. This review presents in vitro evidence suggesting that drugs modulating this cytokine balance include non-steroidal anti-inflammatory agents, phosphodiesterase inhibitors and opioids, acting through effects on intracellular cyclic nucleotide messenger systems. An important consequence of the pro-inflammatory cytokine activity is increased adhesion of neutrophils. Aspects of this process may be inhibited by avoiding low blood flow states, by reducing adhesion molecule expression (for example by use of pentoxifylline), or by use of negatively charged anions such as heparin. Neutrophil activity is generally depressed by intravenous anaesthetic induction agents, but is enhanced by opioids. Natural killer cell activity, which is involved in immunity against tumour cells and virally infected cells is transiently depressed by volatile anaesthetic agents and opioids. In contrast catecholamines enhance natural killer cell activity. Whereas decrease in immunoglobulin levels occur peri-operatively, this is not thought to be as a result of drugs at clinically used concentrations but rather due to haemodilution.

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.

The role of cytokines in cardiac surgery

Cytokines are a large and rapidly expanding group of polypeptides produced by many different cell types. Increasing interest has been focused on the role of cytokines as mediators of metabolic, immunological and endocrine responses to surgery. The cytokine response in patients undergoing cardiac surgery during cardiopulmonary bypass (CPB) is fairly well-defined and dominated by the proinflammatory cytokines IL-6, TNF alpha and IL-8 and the antiinflammatory cytokine IL-10. Little is known about the cytokine response in patients who develop postoperative complications but CPB with mechanical trauma and blood contact to artificial membranes is definitely an unphysiological state and may contribute to an uncontrollable response similar to that of patients with multiorgan failure and septic shock.

RETRACTED: Hypothermic versus normothermic cardiopulmonary bypass: influence on circulating adhesion molecules

OBJECTIVE

Cardiopulmonary bypass (CPB) may result in a whole-body inflammatory response with the risk of subsequent development of organ failure. Leukocyte-endothelial binding followed by neutrophil migration appear to play a central role. This process is markedly influenced by adhesion molecules. Whether plasma levels of circulating adhesion molecules are beneficially influenced by hypothermic CPB was studied in patients undergoing either hypothermic or normothermic CPB.

DESIGN

Prospective, randomized study.

SETTING

Single-Institutional, clinical investigation in a cardiac anesthesia department of a university hospital.

PARTICIPANTS

30 patients scheduled for elective aortocoronary artery bypass grafting.

INTERVENTIONS

The patients were prospectively and randomly divided into two groups: group 1 underwent hypothermic CPB (rectal temperature 27 to 28 degrees C; n = 15) and group 2 normothermic CPB (rectal temperature > 36 degrees C; n = 15).

MEASUREMENTS AND MAIN RESULTS

Plasma levels of circulating (soluble) adhesion molecules (endothelial leukocyte adhesion molecules [sELAM-1], vascular cell adhesion molecule-1 [sVCAM-1], intercellular adhesion molecule-1 [sICAM-1], and granule membrane protein 140 [sGMP-140]) were measured from arterial blood samples using enzyme-linked immunosorbent assays (ELISA) after induction of anesthesia (= baseline values), after weaning from bypass, at the end of surgery, 5 hours after the end of CPB, and on the morning of the first postoperative day. Mean rectal temperature of group 1 was 27.2 +/- 0.4 degrees C and 36.7 +/- 0.4 degrees C in group 2. In both groups, plasma levels of sELAM-1 were significantly higher than baseline only 5 hours after CPB. sICAM-1 increased until the first postoperative day (group 1: +35%; group 2: +37%) without, however, exceeding the normal range. sVCAM-1 plasma levels increased after CPB (group 1: +56%; group 2: +40%). At the end of surgery and 5 hours after CPB, sGMP-140 plasma levels were significantly higher in the hypothermic (increase from 301 +/- 34 to 582 +/- 57 ng/mL) than in the normothermic patients (increase from 310 +/- 45 to 480 +/- 32 ng/mL). On the first postoperative day, both groups showed similar, significantly elevated plasma levels of sGMP-140.

CONCLUSIONS

Plasma levels of circulating adhesion molecules sELAM-1, sICAM-1, and sVCAM-1 did not differ between hypothermic and normothermic CPB, indicating no differences in endothelial activation between the two groups. Only sGMP-140 plasma levels were increased more after hypothermic CPB. Additional influences of hypothermia on the coagulation system might have contributed to the higher sGMP-140 plasma levels of these patients. The definite role of circulating adhesion molecules in cardiac surgery patients remains to be elucidated.

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.

Steroid inhibition of cytokine-mediated vasodilation after warm heart surgery

BACKGROUND

Peripheral vasodilation, a potentially adverse effect of warm heart surgery, may be mediated by the perioperative release of cytokines. Corticosteroids may abolish cytokine production and vasodilation. We investigated cytokine production and its inhibition by steroids in patients undergoing elective coronary bypass surgery.

METHODS AND RESULTS

Twenty-five patients undergoing coronary bypass surgery with normothermic cardiopulmonary bypass received either preoperative steroid (Solumedrol 250 mg IV, n = 16) or no steroid (n = 9, control group). Blood samples were obtained serially for 24 hours and assayed for interleukin-6 (IL-6), tumor necrosis factor (TNF), and interleukin-8 (IL-8). In the control patients, the IL-6, TNF, and IL-8 levels were elevated postoperatively and peaked between 3 and 6 hours after surgery (IL-6, 1330 +/- 295 [mean +/- SEM] pg/mL; TNF, 18.4 +/- 9.8 pg/mL; and IL-8, 150 +/- 51 pg/mL). Cytokine release was abolished in patients receiving preoperative corticosteroid (IL-6, 75 +/- 38 pg/mL; TNF, 2.6 +/- 0.5 pg/mL; and IL-8, 33 +/- 6.7 pg/mL; P < .05). Patients receiving steroid premedication had higher arterial pressure, lower cardiac index, and higher systemic vascular resistance, indicating less vasodilation.

CONCLUSIONS

Our findings demonstrate that cytokine production occurs after normothermic cardiopulmonary bypass. Preoperative administration of steroids abolishes cytokine release and vasodilation.

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.

Ca(2+)-independent nitric oxide synthase activity in human lung after cardiopulmonary bypass

BACKGROUND

Because surgery involving cardiopulmonary bypass induces a systemic inflammatory response, the effect of cardiopulmonary bypass on nitric oxide (NO) generation was investigated in human lung tissue.

METHODS

Nitric oxide synthase (NOS) activity was measured by the conversion of 14C-L-arginine to 14C-L-citrulline in tissue biopsy samples obtained before and after cardiopulmonary bypass.

RESULTS

The Ca(2+)-independent production of NO found before cardiopulmonary bypass was extremely low (1.5 (0.5) pmol citrulline/mg/min), but was increased after the bypass operation (23.6 (11) pmol/mg/min).

CONCLUSIONS

Ca(2+)-independent NOS activity was detected in human lung after cardiopulmonary bypass. This finding may provide an important insight into the pathogenesis of the tissue damage and acute phase response observed after such surgery.

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.

Circulating adhesion molecules in cardiac operations: influence of high-dose aprotinin

Cardiac operations using cardiopulmonary bypass (CPB) are associated with a systemic inflammatory response most likely attributable to the release of various inflammatory mediators and activation of complement or coagulation cascade. In addition, (circulating) adhesion molecules, such as endothelial leukocyte adhesion molecule (ELAM-1), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1), appear to be of central importance in the CPB-related inflammatory process. In this situation, antiproteases, such as aprotinin, may help to prevent damage of endothelial integrity. In a prospective study, 40 consecutive patients undergoing elective cardiac operation were randomly divided into two groups (with 20 patients in each group): in group 1 "high-dose" aprotinin was used (2 million IU of aprotinin before CPB, 500,000 IU/h until end of operation, 2 million IU added to the prime) (with aprotinin), and in group 2 no aprotinin was given (without aprotinin). Circulating adhesion molecules (cICAM-1, cELAM-1, and cVCAM-1) were measured from arterial blood samples using ELISA after induction of anesthesia (baseline), during CPB, at the end of the operation, 5 hours after CPB, and on the first postoperative day. The two groups were comparable concerning their biometric profile and CPB data. Baseline values of circulating adhesion molecules were within normal range and similar in both groups. During CPB, hemodilution resulted in a decrease in all circulating adhesion molecules. On the first postoperative day, cICAM-1 (with aprotinin, 215 +/- 32 ng/mL; without aprotinin, 230 +/- 40 ng/mL) and cELAM-1 (with aprotinin, 28 +/- 6 ng/mL; without aprotinin, 31 +/- 6 ng/mL) returned to baseline values.(ABSTRACT TRUNCATED AT 250 WORDS)