Hypothermia during cardiopulmonary bypass delays but does not prevent neutrophil-endothelial cell adhesion. A clinical study

Strategies to attenuate maladaptive inflammatory response associated with cardiopulmonary bypass

Cardiopulmonary bypass (CPB) initiates an intense inflammatory response due to various factors: conversion from pulsatile to laminar flow, cold cardioplegia, surgical trauma, endotoxemia, ischemia-reperfusion injury, oxidative stress, hypothermia, and contact activation of cells by the extracorporeal circuit. Redundant and overlapping inflammatory cascades amplify the initial response to produce a systemic inflammatory response, heightened by coincident activation of coagulation and fibrinolytic pathways. When unchecked, this inflammatory response can become maladaptive and lead to serious postoperative complications. Concerted research efforts have been made to identify technical refinements and pharmacologic interventions that appropriately attenuate the inflammatory response and ultimately translate to improved clinical outcomes. Surface modification of the extracorporeal circuit to increase biocompatibility, miniaturized circuits with sheer resistance, filtration techniques, and minimally invasive approaches have improved clinical outcomes in specific populations. Pharmacologic adjuncts, including aprotinin, steroids, monoclonal antibodies, and free radical scavengers, show real promise. A multimodal approach incorporating technical, circuit-specific, and pharmacologic strategies will likely yield maximal clinical benefit.

Opportunities of cerebroprotection in children in cardiac surgery (review of literature)

The analysis of the literature in the main search scientific systems was carried out to identify the current means of cerebroprotection. The assessment is given both to the familiar methods that  have become «traditional» for cardiac surgery (hypothermia, etc.) and pharmacological approaches that are less common in clinical practice: the use of melatonin,  ketamine.  The characteristics of some drugs that  are promising for solving this problem are also given.

Effects of Minimal Extracorporeal Circulation on the Systemic Inflammatory Response and the Need for Transfusion after Coronary Bypass Grafting Surgery

Objectives

The aim of this study is to compare the effects of the minimal extracorporeal circulation (MiECT) on postoperative systemic inflammatory response and the need for transfusion in patients undergoing open heart surgery with cardiopulmonary bypass.

Methods

Patients were divided into two groups; Group M (n=31) included the patients operated via using the MiECT system and Group C (n=27) included the patients operated via using conventional cardiopulmonary bypass (CPB). Perioperative markers of inflammation after cardiopulmonary bypass in both groups were tested by measuring the levels via chemiluminescent immunometric assay. Blood samples were taken consecutively after anesthesia induction, 30^th minute of CPB, on the 6^th, 24^th, and 48^th hours after cardiopulmonary bypass.

Results

The mean amount of priming solution was significantly lower in Group M when compared to Group C (802.60 ± 48.26 and 1603.71 ± 49.85 ml). The mean hematocrit (Hct) value taken immediately after cardiopulmonary bypass was found to be significantly higher in the MiECT patients with respect to the other group (% 32.71 ± 3.98 and % 28.82 ± 4.39). The transfused amounts of erythrocyte suspension and fresh frozen plasma were found to be significantly lower in patients in Group M when compared to those in Group C. Postoperative mediastinal drainage was also significantly lower in patients in Group M with respect to the other group. There was no significant difference between markers of inflammation.

Conclusion

Our results show that MiECT seems to be more advantageous in terms of priming volume, perioperative hematocrit levels, need for blood and blood product transfusion, and mediastinal drainage with respect to the conventional approach after coronary artery bypass grafting.

The Inflammatory Response to Cardiopulmonary Bypass— Should It Be Treated?

Proinflammatory cytokines, including tumor necrosis factor (TNF) α and the interieukins, are important in the metabolic response to injury or infection. Although the importance of cytokine release during cardiopulmonary bypass (CPB) is not fully appreciated, increasing num bers of publications present evidence that cytokine release during CPB is detrimental. In addition, endoge nous inhibitors of cytokine function, including TNF-sol uble receptor and interleukin 1 receptor antagonist, are released in response to elevated proinflammatory cyto kine levels during and after CPB. The involvement of these endogenous inhibitors in the pathophysiology of proinflammatory cytokine-induced solid organ injury after CPB remains to be defined.

Mechanisms of oxidative stress and myocardial protection during open-heart surgery

Cold heart protection via cardioplegia administration, limits the amount of oxygen demand. Systemic normothermia with warm cardioplegia was introduced due to the abundance of detrimental effects of hypothermia. A temperature of 32-33°C in combination with tepid blood cardioplegia of the same temperature appears to be protective enough for both; heart and brain. Reduction of nitric oxide (NO) concentration is in part responsible for myocardial injury after the cardioplegic cardiac arrest. Restoration of NO balance with exogenous NO supplementation has been shown useful to prevent inflammation and apoptosis. In this article, we discuss the "deleterious" effects of the oxidative stress of the extracorporeal circulation and the up-to-date theories of "ideal'' myocardial protection.

Expression of CD11b (MAC-1) and CD162 (PSGL-1) on monocytes is decreased under conditions of deep hypothermic circulatory arrest

Deep hypothermic circulatory arrest (DHCA) is a common technique used to protect vital organs during surgical interventions on the thoracic aorta or during surgery for complex congenital heart disease. Activated leukocytes are key mediators of inflammatory responses during ischemia. Intercellular crosstalk between leukocytes, platelets and endothelial cells is mediated by cell adhesion molecules. These molecules trigger complex cell-cell interaction mechanisms and initiate the release of proinflammatory molecules. One parameter that is known to have a significant impact on inflammatory cell activation and the production of proinflammatory markers is temperature. However, to the best of our knowledge, no data have yet been published on the effect of hypothermia on leukocyte surface markers during DHCA. Thus, the aim of the present study was to investigate the effect of hypothermia on the expression of cell adhesion molecules on monocytes under DHCA conditions in vitro. Blood samples collected from 11 healthy volunteers were incubated in a well-established model simulating circulatory arrest at 36°C and 18°C for 30 min. The expression of cluster of differentiation (CD) molecule 11B (CD11b), CD54 and CD162 on monocytes was measured as the mean fluorescence intensity (MFI) using flow cytometry. The expression level of CD11b on monocytes was significantly decreased following the incubation of the blood samples at 18°C compared with the level in blood samples incubated at 36°C (P<0.001). After 30 min of blood stasis in the circulatory arrest model, the expression level of CD162 on monocytes was significantly lower in the blood samples incubated at 18°C than in those incubated at 36°C (P<0.001). No association was identified between temperature and the surface expression of CD54 on monocytes following 30 min of stasis. These findings demonstrate that deep hypothermia decreases the expression of CD11b and CD162 on monocytes in an experimental setup simulating the conditions of DHCA. This may be the result of the inhibition of leukocyte-endothelial and leukocyte-platelet interactions, which may be a beneficial aspect of deep hypothermia that affects the inflammatory response and tissue damage during DHCA.

The dual role of the neuroinflammatory response after ischemic stroke: modulatory effects of hypothermia

Neuroinflammation is a key element in the ischemic cascade after cerebral ischemia that results in cell damage and death in the subacute phase. However, anti-inflammatory drugs do not improve outcome in clinical settings suggesting that the neuroinflammatory response after an ischemic stroke is not entirely detrimental. This review describes the different key players in neuroinflammation and their possible detrimental and protective effects in stroke. Because of its inhibitory influence on several pathways of the ischemic cascade, hypothermia has been introduced as a promising neuroprotective strategy. This review also discusses the influence of hypothermia on the neuroinflammatory response. We conclude that hypothermia exerts both stimulating and inhibiting effects on different aspects of neuroinflammation and hypothesize that these effects are key to neuroprotection.

An in vitro model for studying neutrophil activation during cardiopulmonary bypass by using a polymerase chain reaction thermocycler

The accurate temperature control of a polymerase chain reaction (PCR) thermocycler was exploited in developing an in vitro model to study neutrophil activation during cardiopulmonary bypass. Neutrophils from 12 volunteers underwent temperature changes in a PCR thermocycler (37 degrees C for 30 minutes, 28 degrees C for 60 minutes, and then 37 degrees C for 90 minutes). Different co-incubates were applied to neutrophils, as follows: Group A: phosphate-buffered saline solution; Group B: platelet activating factor (PAF) ; Group C: platelet-depleted plasma; Group D: platelet-depleted plasma + PAF; and Group E: platelet-rich plasma. Membrane-bound elastase (MBE) activity was measured every 30 minutes throughout the experiment. MBE activity decreased significantly after hypothermia, compared with the baseline level (p < 0.001), and it resumed an increase after re-warming. Among all co-incubates, platelet-rich plasma was the most potent pro-inflammatory stimulus to neutrophils. A linear correlation was found between MBE and platelet count in platelet-rich plasma (p = 0.004). A novel in vitro model involving a PCR thermocycler has been proved to be reliable in the study of neutrophil activation during cardiopulmonary bypass. The model could possibly be used as an alternative to animals in the development of new drugs to combat neutrophil damage to tissues and organs during cardiopulmonary bypass in cardiac surgery.

Hibernation: the immune system at rest?

Mammalian hibernation consists of torpor phases when metabolism is severely depressed, and T(b) can reach as low as approximately -2°C, interrupted by euthermic arousal phases. Hibernation affects the function of the innate and the adaptive immune systems. Torpor drastically reduces numbers of all types of circulating leukocytes. In addition, other changes have been noted, such as lower complement levels, diminished response to LPS, phagocytotic capacity, cytokine production, lymphocyte proliferation, and antibody production. Hibernation may therefore increase infection risk, as illustrated by the currently emerging WNS in hibernating bats. Unraveling the pathways that result in reduced immune function during hibernation will enhance our understanding of immunologic responses during extreme physiological changes in mammals.

Prolonged extracorporeal membrane oxygenation-assisted support provides improved survival in hypothermic patients with cardiocirculatory arrest

OBJECTIVE

Extracorporeal circulation is considered the gold standard in the treatment of hypothermic cardiocirculatory arrest; however, few centers use extracorporeal membrane oxygenation instead of standard extracorporeal circulation for this indication. The aim of this study was to evaluate whether extracorporeal membrane oxygenation-assisted resuscitation improves survival in patients with hypothermic cardiac arrest.

METHODS

A consecutive series of 59 patients with accidental hypothermia in cardiocirculatory arrest between 1987 and 2006 were included. Thirty-four patients (57.6%) were resuscitated by standard extracorporeal circulation, and 25 patients (42.4%) were resuscitated by extracorporeal membrane oxygenation. Accidental hypothermia was caused by avalanche in 22 patients (37.3%), drowning in 22 patients (37.3%), exposure to cold in 8 patients (13.5%), and falling into a crevasse in 7 patients (11.9%). Multivariate logistic regression analysis was used to compare extracorporeal membrane oxygenation with extracorporeal circulation resuscitation, with adjustment for relevant parameters.

RESULTS

Restoration of spontaneous circulation was achieved in 32 patients (54.2%). A total of 12 patients (20.3%) survived hypothermia. In the extracorporeal circulation group, 64% of the nonsurviving patients who underwent restoration of spontaneous circulation died of severe pulmonary edema, but none died in the extracorporeal membrane oxygenation group. In multivariate analysis, extracorporeal membrane oxygenation-assisted resuscitation showed a 6.6-fold higher chance for survival (relative risk: 6.6, 95% confidence interval: 1.2-49.3, P = .042). Asphyxia-related hypothermia (avalanche or drowning) was the most predictive adverse factor for survival (relative risk: 0.09, 95% confidence interval: 0.01-0.60, P = .013). Potassium and pH failed to show statistical significance in the multivariate analysis.

CONCLUSIONS

Extracorporeal rewarming with an extracorporeal membrane oxygenation system allows prolonged cardiorespiratory support after initial resuscitation. Our data indicate that prolonged extracorporeal membrane oxygenation support reduces the risk of intractable cardiorespiratory failure commonly observed after rewarming.

An alternative pathway for fibrinolysis is activated in patients who have undergone cardiopulmonary bypass surgery and major abdominal surgery

INTRODUCTION

We conducted this prospective study in order to investigate the hypotheses that an alternative pathway for fibrinolysis is activated in patients who have undergone cardiopulmonary bypass (CPB) surgery and major abdominal surgery and that the levels of fibrin degradation products digested by polymorphonuclear neutrophil elastase (elastase-XDP) and the D-dimer increase in the patients' plasma.

MATERIALS AND METHODS

We studied a total of 77 patients who were scheduled to undergo either CPB surgery (36 patients) or major abdominal surgery (41 patients) and then measured the elastase-XDP and D-dimer levels at several time points both during and after the surgeries. The CPB surgery was divided into surgery for aortic dissection (AD) and cardiac surgery. The major abdominal surgery consists of hepatic resection and esophagectomy.

RESULTS

The elastase-XDP and D-dimer levels significantly increased in the patients who underwent both CPB surgery and major abdominal surgery. The elastase-XDP levels in AD surgery showed highest values at the end of the CPB, while the levels in the other surgeries reached their peak on the day after the surgery. Statistical difference was seen in the levels of elastase-XDP among the three subgroups undergoing a hepatic resection. While we found significant correlations between the levels of elastase-XDP and D-dimer in patients undergoing CPB surgery and a subsegmentectomy of a cirrhotic liver, the correlation coefficients were markedly low in comparison to those of the other surgeries.

CONCLUSIONS

Our findings demonstrated that the elastase-mediated pathway of fibrinolysis is activated to varying degrees depending on the surgery performed. Variations in the correlation coefficients between the levels of elastase-XDP and D-dimer may suggest that elastase-mediated fibrinolysis play a different role from the physiological fibrinolysis mediated by plasmin.

"Initial, continuous and intermittent bolus" administration of minimally-diluted blood cardioplegia supplemented with potassium and magnesium for hypertrophied hearts

BACKGROUND

Hypertrophied hearts are subject to the deleterious effects of intraoperative ischemia-reperfusion, and stable maintenance of myocardial cardioplegic arrest is essential. Continuous cardioplegia infusion appears an ideal modification to overcome this issue, except for a large amount of crystalloid solution infused into the myocardium. We previously introduced "initial, continuous and intermittent bolus" administration of minimally-diluted blood cardioplegia (mini-BCP) supplemented with potassium and magnesium, and this study was designed to elucidate its efficacy in patients with hypertrophied hearts.

METHODS

Thirty patients (M:F=17:13, 69.2+/-7.8 years) with left ventricular mass index greater than 150 g/m(2) who underwent aortic valve replacement between 1996 and 2002 were enrolled, and were allocated to one of the two groups. The same infusion protocol was used for both groups as follows: initial and intermittent (every 20 min) BCP was antegradely infused for 2 min at the rate of 200 mL/min, and continuous retrograde BCP flow rate was set at 60-100mL/min. Group C (n=15) received 4:1-diluted BCP modified with Buckberg solution, and Group M (n=15) were given mini-BCP supplemented with potassium (initial/others: 15.4/9.8 mEq/L) and magnesium (initial/others: 6.5/4.0 mEq/L).

RESULTS

Stable cardioplegic arrest was maintained in all study patients, and total amount of crystalloid solution as cardioplegia was lesser in Group M (79.4+/-27.5 mL) than in Group C (937.3+/-372. 1mL, p<0.01). Group M showed a higher incidence of spontaneous heartbeat recovery after aortic unclamping (13 versus 6, p<0.05) and a lower incidence of postoperative atrial fibrillation (0 versus 5, p<0.05). Postoperatively, maximum dopamine dose (3.35+/-2.27 microg/kg/min versus 5.49+/-2.30 microg/kg/min, p<0.05) and peak plasma creatine kinase-myocardial band (CK-MB) (21.7+/-7.2 IU/L versus 28.8+/-8.4 IU/L, p<0.05) were lower in Group M. Early postoperative echocardiography revealed a lower incidence of paradoxical ventricular septal motion (M versus C; 3 versus 10, p<0.05) and greater left ventricular ejection fraction (M versus C; 70.7+/-4.0% versus 67.0+/-5.3%, p<0.05) in Group M.

CONCLUSIONS

These results suggest that "initial, continuous and intermittent bolus" administration of mini-BCP, supplemented with potassium and magnesium, is a novel modification for patients with hypertrophied hearts in terms of simplifying the maintenance of cardioplegic arrest with beneficial myocardial protective effects.

Phosphodiesterase type 4 inhibitor rolipram inhibits activation of monocytes during extracorporeal circulation

OBJECTIVE

Cardiopulmonary bypass is associated with systemic inflammatory response syndrome and risk of multiorgan injury mediated by activated leukocytes. Phosphodiesterase type 4 is the predominant phosphodiesterase isozyme in leukocytes and plays a key role in the regulation of leukocyte activation. The aim of this study was to examine the effect of rolipram, a selective phosphodiesterase type 4 inhibitor, on functional changes of monocytes during simulated extracorporeal circulation.

METHODS AND RESULTS

Simulated extracorporeal circulation was established by recirculating heparinized human blood for 120 minutes on a membrane oxygenator with or without 10 micromol/L of rolipram. L-selectin and CD11b expression of monocytes were measured with flow cytometry. C4d fragment, Bb fragment, C5b-9, and interleukin-6 were measured with enzyme immunoassay. Rolipram reduced the increase in CD11b expression and the decrease in L-selectin expression of monocytes in response to simulated extracorporeal circulation. Rolipram inhibited the increase in C4d fragment and interleukin-6, but it did not affect the increase in Bb fragment or C5b-9.

CONCLUSION

Rolipram inhibited changes in adhesion molecule expression and interleukin-6 release by activated monocytes in simulated extracorporeal circulation. This study suggests that phosphodiesterase type 4 inhibition could be feasible therapeutic strategy to prevent exaggerated inflammatory response and organ injury in patients undergoing cardiopulmonary bypass.

Effects of perioperative hypothermia and warming in surgical practice

Perioperative hypothermia is common and adversely affects clinical outcomes due to its effect on a range of homeostatic functions. Many of these adverse consequences are preventable by the use of warming techniques. A literature search was conducted to identify relevant published articles on perioperative hypothermia and warming. The databases searched include MEDLINE (1966 to February 2005), EMBASE (1974 to February 2005), CINAHL, the Cochrane library and the health technology assessment database. Reference lists of key articles were also searched. The primary beneficial effects of warming are mediated through increased blood flow and oxygen tension at tissue level. Reduction in wound infection, blood loss and perioperative pain with warming is promising. However, more evidence from good-quality prospective randomised controlled trials is needed to evaluate the role of warming in improving overall morbidity, mortality and hospital stay as well as to clarify its role as an adjunct to resuscitation and during the pre-hospital transport phase of critically ill patients. Awareness of the risks of perioperative hypothermia is the key to prevention. Achieving normothermia throughout the patient's journey is a worthwhile goal in surgical patients.

Clinical benefits of continuous leukocyte filtration during cardiopulmonary bypass in patients undergoing valvular repair or replacement

Valve operations in the form of repair or replacement make up a significant population of patients undergoing surgical procedures in the USA annually with the use of cardiopulmonary bypass. These patients experience a wide range of complications that are considered to be mediated by activation of complement and leukocytes. The extracorporeal perfusion circuit consists of multiple synthetic artificial surfaces. The biocompatibility of the blood contact surfaces is a variable that predisposes patients to an increased risk of complement mediation and activation. This can result in an inflammatory process, causing leukocytes to proliferate and sequester in the major organ systems. The purpose of this study was to determine whether filtration of activated leukocytes improved clinical outcomes following surgical intervention for valve repair or replacement. In this paper, we report a retrospective matched cohort study of 700 patients who underwent valve procedures from June 1999 to December 2002. The control group (CG) consisted of patients who had a conventional arterial line filter. In the study group (SG), patients had a conventional arterial line filter and a leukocyte arterial line filter (Pall Medical, NY). In the SG, blood diverted to the cardioplegia system was also leukocyte depleted to enhance myocardial preservation by adapting this device to the outflow port on the filter. Patient characteristics were similar for the SG and the CG, including 228 males and 122 females, mean age (62.4 versus 64.2 years), cardiopulmonary bypass time (127+/-64 versus 116+/-53 min), and aortic crossclamp time (84+/-23 versus 81+/-23 min). Our results demonstrate that the SG achieved statistically significant reduction in the time to extubation (p =0.03) and the number of patients with prolonged intubation in excess of 24 hours (p <0.04), in addition to improved postoperative oxygenation (p=0.01), and decreased length of hospital stay (p =0.03). We believe that leukocyte filters are clinically beneficial, as demonstrated by the results presented in this study.

Pathophysiologic changes and effects of hypothermia on outcome in elective surgery and trauma patients

Generally, hypothermia is defined as a core temperature <35 degrees C. In elective surgery, induced hypothermia has beneficial effects. It is recommended to diminish complications attributable to ischemia reperfusion injury. Experimental studies have shown that hypothermia during hemorrhagic shock has beneficial effects on outcome. In contrast, clinical experience with hypothermia in trauma patients has shown accidental hypothermia to be a cause of posttraumatic complications. The different etiology of hypothermia might be one reason for this disparity because induced therapeutic hypothermia, with induction of poikilothermia and shivering prevention, is quite different from accidental hypothermia, which results in physiological stress. Other studies have shown evidence that this contradictory effect is related to the plasma concentration of high-energy phosphates (e.g., adenosine triphosphate [ATP]). Induced hypothermia preserves ATP storage, whereas accidental hypothermia causes depletion. Hypothermia also has an impact on the immunologic response after trauma and elective surgery by decreasing the inflammatory response. This might have a beneficial effect on outcome. Nevertheless, posttraumatic infectious complications may be higher because of an immunosuppressive profile. Further studies are needed to investigate the impact of induced hypothermia on outcome in trauma patients.

ONO-6818, a novel, potent neutrophil elastase inhibitor, reduces inflammatory mediators during simulated extracorporeal circulation

BACKGROUND

Among the serine proteases, neutrophil elastase is a powerful cytotoxic enzyme and plays a pivotal role in the inflammatory response associated with cardiopulmonary bypass. This study assesses the effects of the specific inhibition of neutrophil elastase by a novel, potent, low-molecular-weight neutrophil elastase inhibitor, ONO-6818. We hypothesized that ONO-6818 reduces inflammatory mediators and modulates adhesion molecules and the deformability of neutrophils during simulated extracorporeal circulation.

METHODS

Simulated extracorporeal circulation was established by recirculating fresh heparinized (3.75 U/mL) human blood for 120 minutes in a membrane oxygenator and a roller pump with and without 1.0 micromol/L of ONO-6818 (n = 9 for control group, n = 7 for ONO-6818 group). The neutrophil adhesion molecules, CD11b and L-selectin, and the cytoplasmic F-actin of neutrophils were measured by flow cytometry. Neutrophil deformability was evaluated using simulated silicon microcapillaries. Neutrophil elastase, interleukin 8, and C5b-9 were measured using enzyme immunoassay.

RESULTS

Neutrophil elastase levels were significantly lower in the ONO-6818 group. ONO-6818 significantly reduced interleukin 8 and C5b-9 production. ONO-6818 did not modulate changes of CD11b and L-selectin during recirculation. Cytoplasmic F-actin content and changes of neutrophil deformability did not significantly differ between the groups.

CONCLUSIONS

Inhibition of neutrophil elastase activity with ONO-6818 reduces further interleukin 8 production and the formation of the complement membrane attack complex, and this results in a reduction of neutrophil elastase levels during simulated extracorporeal circulation. This study suggests that specific neutrophil elastase inhibition with ONO-6818 is a feasible therapeutic option to attenuate the exaggerated inflammatory response associated with cardiopulmonary bypass.

Induction of tissue factor in the arterial wall during recurrent thrombus formation

OBJECTIVE

Tissue factor (TF) is normally expressed at low levels in the media of blood vessels, but it is readily induced after vessel injury. It is not known whether vascular damage per se or thrombus formation is responsible for this phenomenon.

METHODS AND RESULTS

Cyclic flow variations (CFVs), attributable to recurrent thrombus formation, were induced in stenotic rabbit carotid arteries with endothelial injury. CFVs were observed for 30 minutes and 2, 4, and 8 hours in different groups of animals. Another group of rabbits pretreated with hirudin before inducing arterial damage to inhibit thrombus formation was observed for 8 hours. Arterial sections were immunostained for TF. Undamaged arteries served as controls. In additional rabbits, in situ hybridization experiments were performed. No TF expression was observed in the media of control vessels, whereas a progressive increase in TF mRNA and protein expression was observed in carotid arteries as CFVs progressed. No increase in TF expression was observed in animals pretreated with hirudin. In vitro experiments demonstrated that TF mRNA is induced in smooth muscle cells stimulated with activated platelets as well as with some platelet-derived mediators.

CONCLUSIONS

This phenomenon may contribute to sustain intravascular thrombus formation after the initial thrombogenic stimulus.

Activated neutrophils and platelet microaggregates impede blood filterability through microchannels during simulated extracorporeal circulation

BACKGROUND

Neutrophil sequestration and platelet microaggregates in organ capillaries have been implicated in the inflammatory response associated with cardiopulmonary bypass. We examined the filterability of neutrophils and platelet microaggregates through silicon microchannels during simulated extracorporeal circulation. We hypothesize that blood contact with artificial surfaces over time decreases the ability of neutrophils, platelets, and their aggregates to pass through microchannels.

METHODS

Fresh human blood from donors (n = 9) was recirculated for 120 minutes in a simulated extracorporeal circuit. Blood samples were obtained from a donor at 0, 30, 60, and 120 minutes of recirculation. The microchannel transit time and the flow behavior of blood cells were evaluated by a silicon microchannel array flow analyzer. CD11b, L-selectin, and F-actin of neutrophils were measured by flow cytometry. Neutrophil and platelet counts and platelet aggregation to adenosine diphosphate were measured.

RESULTS

The microchannel transit time was prolonged during recirculation, reaching 185.9% +/- 25.6% of baseline at 120 minutes. The video microscope showed that neutrophils and platelet microaggregates plugged the microchannels. CD11b, L-selectin, and F-actin levels changed significantly by 120 minutes. Platelet counts decreased and platelet aggregability was attenuated.

CONCLUSIONS

Simulated extracorporeal circulation caused a progressive loss in the ability of neutrophils, platelets, and their aggregates to pass through the microchannels independent of neutrophil adhesion molecule expression.

Mild hypothermia during hemorrhagic shock in rats improves survival without significant effects on inflammatory responses

OBJECTIVE

To explore the hypothesis that the survival benefit of mild, therapeutic hypothermia during hemorrhagic shock is associated with inhibition of lipid peroxidation and the acute inflammatory response.

DESIGN

Prospective and randomized.

SETTING

Animal research facility.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Rats underwent pressure-controlled (mean arterial pressure 40 mm Hg) hemorrhagic shock for 90 mins. They were randomized to normothermia (38.0 +/- 0.5 degrees C) or mild hypothermia (33-34 degrees C from hemorrhagic shock 20 mins to resuscitation time 12 hrs). Rats were killed at resuscitation time 3 or 24 hrs.

MEASUREMENTS AND MAIN RESULTS

All seven rats in the hypothermia group and seven of 15 rats in the normothermia group survived to 24 hrs (p <.05). Hypothermic rats had lower serum potassium and higher blood glucose concentrations at 90 mins of hemorrhagic shock (p <.05). At resuscitation time 24 hrs, the hypothermia group had less liver injury (based on serum concentrations of ornithine carbamolytransferase and liver histology) and higher blood glucose than the normothermia group (p <.05). There were no differences in serum free 8-isoprostane (a marker of lipid peroxidation by free radicals) between the two groups at either baseline or resuscitation time 1 hr. Serum concentrations of interleukin- 1 beta, interleukin-6, and tumor necrosis factor-alpha peaked at resuscitation time 1 hr. Tumor necrosis factor-alpha concentrations were higher (p <.05) at resuscitation time 1 hr in the hypothermia group compared with the normothermic group. Serum cytokine concentrations were not different between survivors and nonsurvivors in the normothermia group. Serum cytokine concentrations returned to baseline values in both groups by 24 hrs. There were no differences in the number of neutrophils in the lungs or the small intestine between the groups. More neutrophils were found in the lungs at resuscitation time 3 hrs than at resuscitation time 24 hrs in both groups (p <.01).

CONCLUSIONS

These data suggest that lipid peroxidation and systemic inflammatory responses to hemorrhagic shock are minimally influenced by mild hypothermia, although liver injury is mitigated and survival improved. Other mechanisms of benefit from mild hypothermia need to be explored.

Phosphodiesterase type 4 inhibition of activated polymorphonuclear leukocytes in a simulated extracorporeal circulation model

OBJECTIVES

Cardiopulmonary bypass is associated with a systemic inflammatory response syndrome and the risk of multiorgan injuries mediated by activated polymorphonuclear leukocytes. Phosphodiesterase type 4 is the predominant phosphodiesterase isozyme in polymorphonuclear leukocytes and plays a key role in the regulation of polymorphonuclear leukocyte activation. The aim of this study was to examine the effect of rolipram, a selective phosphodiesterase type 4 inhibitor, on the functional changes of polymorphonuclear leukocytes by using simulated extracorporeal circulation.

METHODS

Simulated extracorporeal circulation was established by recirculating heparinized human blood for 120 minutes on a membrane oxygenator with and without 10 micro mol/L rolipram. F-actin content and L-selectin and CD11b expression of polymorphonuclear leukocytes were measured by means of flow cytometry. Polymorphonuclear leukocyte deformability was evaluated with a microchannel array flow analyzer that had a similar diameter as the capillaries. Polymorphonuclear leukocyte elastase was measured with an enzyme immunoassay.

RESULTS

Rolipram reduced the increase of F-actin content of polymorphonuclear leukocytes and the increase of transit time of 100 micro L of blood sample through a microchannel. Rolipram reduced the increase of CD11b expression and the decrease of L-selectin expression of polymorphonuclear leukocytes. Rolipram reduced the release of elastase from polymorphonuclear leukocytes.

CONCLUSION

Rolipram inhibited the deformability change mediated by F-actin assembly, the changes in adhesion molecules, and the release of elastase from activated polymorphonuclear leukocytes in simulated extracorporeal circulation. This study suggests that phosphodiesterase type 4 inhibition could be a feasible therapeutic strategy to prevent the exaggerated inflammatory response related to cardiopulmonary bypass.

Endothelial damage during myocardial preservation and storage

Preservation and storage techniques represent two major issues in routine cardiac surgery and heart transplantation. Historically, these methods were conceived to prevent ischemic injury to myocardium after cardiac arrest during heart operations. Evidence shows that endothelium plays a critical role in the maintenance of normal heart function after cardiac operation, mainly by controlling the coronary circulation. Methods for preservation and storage, developed initially to protect cardiomyocyte function, may be deleterious for vascular endothelium and compromise myocardial protection. In this review article the present knowledge about endothelial injury secondary to preservation and storage techniques is discussed.

Leukocyte depletion attenuates expression of neutrophil adhesion molecules during cardiopulmonary bypass in human beings

BACKGROUND

On the basis of scanty information, the effects of a leukocyte filter during cardiac operations in human beings have been examined from the viewpoint of the expression of neutrophil adhesion molecules. This study was therefore designed to determine whether leukocyte depletion during cardiopulmonary bypass may interfere with neutrophil adhesion properties.

METHODS

Twenty-four patients undergoing elective heart operations were randomly allocated to a leukocyte-depletion group or a control group. Blood samples were collected at 7 points: before sternotomy, at 10, 30, and 60 minutes of cardiopulmonary bypass, at termination of cardiopulmonary bypass, 5 minutes after protamine administration, and 2 hours after cardiopulmonary bypass. The expression of the neutrophil surface adhesion molecules L-selectin and beta2-integrins was determined by flow cytometric analysis in whole blood.

RESULTS

(1) CD11a expression did not change significantly in either group. There were no significant differences between control and leukocyte-depletion groups (P =.63). (2) There was a significantly higher expression of CD11b on the neutrophils during cardiopulmonary bypass in the control group than in the leukocyte-depletion group (P =.01). (3) CD11c expression was initially up-regulated from the onset of cardiopulmonary bypass, reaching a peak at 60 minutes after bypass in the control group (P =.02). The expression of CD11c did not differ significantly between groups (P =.23). (4) L-selectin expression was significantly lower in the leukocyte-depletion group than in the control group (P =.03).

CONCLUSIONS

The major findings of the present study in human subjects undergoing elective cardiac operations with cardiopulmonary bypass are as follows: (1) bypass was associated with an up-regulation of the adhesion molecules L-selectin, CD11b, and CD11c but with no significant change in CD11a expression, and (2) the clinical use of a leukocyte-depleting filter could down-regulate the expression of CD11b and L-selectin.

The effect of methanol washing of plasticized polyvinyl chloride on biomaterial-contact-mediated CD11b (mac-1) expression in a rat recirculation model

Our objective was to assess whether using a methanol wash to reduce the level of plasticizer present on the surface of medical-grade polyvinyl chloride (PVC) has a moderating effect on the expression of CD11b (mac-1) on neutrophils in rats undergoing recirculation. The study was carried out on 3 groups of 10 adult male Sprague-Dawley rats weighing between 350 and 450 g. In the 2 test groups, the animals were exposed to 48 cm(2) of di-(2-ethyl-hexyl)-phthalate (DEHP)-plasticized PVC in a parallel plate recirculating test cell through which blood was recirculated at 1.5 ml/min. In the first test group, the PVC was untreated; in the second test group, the PVC was washed in methanol to reduce the level of plasticizer on the surface. The test cell was connected to the right femoral circulation, and recirculation was established for a period of 60 min. Blood samples were taken at 0, 30, and 60 min for assessment of CD11b expression on neutrophils using flow cytometric analysis. In a third group of 10 control experiments, rats underwent the entire surgical procedure, but without recirculation through the test cell. There was statistically significant (p < 0.001) lower Cd11b expression on neutrophils in the blood of rats perfused through the cell containing methanol-washed PVC after 30 min and at 60 min. CD11b expression was significantly (p < 0.001) lower in the control group than in both test groups at both the 30 and 60 min time points and at the 60 min time point on comparison with the group where blood was perfused through methanol-washed PVC. These results demonstrate that the biomaterial-contact-mediated upregulation of CD11b may be significantly reduced by employing a methanol-washing technique on the plasticized PVC. Although this technique does not entirely eliminate the expression of CD11b on neutrophils, the difference is significant and suggests the role of the plasticizer in the development of this inappropriate inflammatory response.

Use of modified ultrafiltration after repair of congenital heart defects

The use of cardiopulmonary bypass (CPB) for repair of congenital heart defects exposes children to extremes of hemodilution and hypothermia. Exposure of blood to the foreign surfaces of the oxygenator and bypass circuit initiates a systemic inflammatory response. Adverse effects of CPB include increased capillary permeability and increased total body water (TBW), which often results in tissue edema and multiple organ dysfunction. A variety of techniques have been developed for reversing tissue edema and hemodilution after CPB, including ultrafiltration during CPB, postoperative peritoneal dialysis, postoperative continuous arterial venous hemofiltration, and aggressive use of diuretics. A technique termed modified ultrafiltration (MUF) has been developed at the Hospital for Sick Children in London. Unlike conventional ultrafiltration, MUF is performed in the immediate post-CPB period and removes excess water from the patient as well as provides a method of salvaging blood from the circuit. MUF has been shown to modulate the inflammatory response to CPB by removing inflammatory mediators including interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF). A prospective randomized trial of MUF showed improved hemodynamics with a reduction in TBW and decreased need for blood transfusion when compared with nonfiltered controls. MUF has been shown to improve left ventricular systolic function after CPB, resulting in increased systolic blood pressure and cardiac index. In a recent study, use of MUF significantly reduced the incidence of pleural effusions after cavopulmonary connection and the Fontan procedure. MUF is a useful adjunct to CPB in children and significantly decreases perioperative morbidity. Copyright 1998 by W.B. Saunders Company

The effect of circuit surface area on CD11b(mac-1) expression in a rat recirculation model

The aim of the study was to assess the effect of exposed surface area of diethylhexylphthalate plasticized polyvinylchloride (PVC) on the expression of the adhesion molecule CD11b(mac-1) on neutrophils and to determine whether there is any apparent advantage in the current trend in reducing circuit surface area in terms of neutrophil activation. The study was carried out using a parallel plate rodent recirculation biomaterial testing model on 4 groups of 10 adult male Sprague Dawley rats weighing between 350 and 450 g. One group comprised the control group in which there was no biomaterial exposure. In the remaining 3 groups, the animals were subjected to either high (48 cm2), intermediate (24 cm2), or low (12 cm2) biomaterial surface area exposure. The parallel plate test cell was connected to the right femoral circulation and recirculation initiated at a flow rate of 1.5 ml/min for a period of 60 min. Blood samples were taken at 0, 30, and 60 min for the assessment of CD11b expression. Cd11b was assessed using flow cytometric analysis on neutrophils. The results demonstrated that there was a surface area related effect in the upregulation of CD11b. The difference at the terminal sample point between the highest surface area group (293.95 +/- 18.57%) and the low surface area group (133.80 +/- 49.31%) was highly statistically significant (p < 0.001). These results demonstrate that there may be some gain in terms of reduced inflammatory response from reducing the exposed surface area of PVC in extracorporeal perfusion circuits.

Cardiopulmonary bypass elicits a pro- and anti-inflammatory cytokine response and impaired neutrophil chemotaxis in neonatal pigs

BACKGROUND

Cardiopulmonary bypass (CPB) induces a systemic inflammatory response and organ dysfunction, especially in children. Plasma concentration of inflammatory markers are increased in response to the trauma of cardiac surgery and CPB. The aim of the present study was to investigate whether the CPB procedure in itself elicits increased levels of inflammatory markers in neonatal pigs.

METHODS

The inflammatory response was measured in piglets undergoing sternotomy alone (sham group, n=13) or sternotomy and CPB (n=14). Inflammatory mediators were measured at baseline and at fixed time-points during and after CPB. IL-8, IL-10 and TNF-alpha levels and C-reactive protein (CRP) concentrations were measured in plasma samples. Polymorphonuclear neutrophils (PMN) chemotaxis was measured ex vivo, and CD-18 expression using an immunofluorescence technique.

RESULTS

Immediately after the CPB procedure increased IL-8 levels were found in the CPB group, but not in sham operated animals (P=0.005). Simultaneously, a marked IL-10 response was measured in the CPB group. Concurrently, PMN chemotaxis decreased in CPB animals but not in the sham group (P=0.04). CD-18 expression and CRP levels were not significantly different between groups and TNF-alpha showed no changes in either group. The chemotactic response did not correlate with plasma IL-8 or IL-10, nor with CD-18 expression.

CONCLUSION

The CPB procedure elicited a systemic inflammatory response in terms of significantly elevated plasma levels of IL-8 and IL-10. Furthermore, a temporary and simultaneous decrease in PMN chemotaxis was observed immediately after CPB.

Stimulation of neutrophil activation during coronary artery bypass grafting: comparison of crystalloid and blood cardioplegia

BACKGROUND

During myocardial ischemia, activation of polymorphonuclear neutrophils (PMNs) results in the production of free oxygen radicals, which increase myocardial injury. It has been shown that PMNs also produce nitric oxide. It is not clear whether PMNs become activated as a result of their direct contact with ischemic/reperfused myocardium or if PMN activation and free oxygen radical production are effects of specific stimuli released during coronary artery bypass grafting (CABG). The aim of the current study was to evaluate plasma-mediated neutrophil stimulation and production of superoxide anion (O2) and nitric oxide in patients undergoing CABG, and to verify whether crystalloid and blood cardioplegia can modify such stimulation.

METHODS

Coronary sinus, peripheral arterial, and venous plasma samples were collected from 50 patients who underwent CABG and were divided into 2 equal groups which received either crystalloid or blood cardioplegia: directly before myocardial ischemia and aortic cross-clamping; at the beginning of reperfusion after aortic clamp release; and 30 minutes after reperfusion. O2 and nitric oxide production by PMN was evaluated by standard methods.

RESULTS

There was a significant (p < 0.05) increase in O2 production by PMN incubated with plasma obtained from the coronary sinus immediately after reperfusion in patients receiving crystalloid cardioplegia compared to blood cardioplegia. No difference was observed in plasma stimulation of nitric oxide production by PMN in the 2 groups of patients at different times during the procedure.

CONCLUSIONS

Cardioplegia may affect release of neutrophil-oriented stimuli from ischemic myocardium and modify neutrophil activation during coronary artery bypass grafting.

Stimulation of neutrophil integrin expression during coronary artery bypass grafting: comparison of crystalloid and blood cardioplegic solutions

OBJECTIVES

This study was designed (1) to evaluate the influence of plasma obtained from patients undergoing coronary artery bypass grafting on L-selectin, CD11b, and CD18 expression on human neutrophils and (2) to determine the influence of the use of crystalloid or blood cardioplegia during bypass grafting on plasma-mediated expression of adhesion molecules on polymorphonuclear neutrophils.

PATIENTS AND METHODS

Patients undergoing coronary artery bypass grafting were divided into 2 groups to receive crystalloid or blood cardioplegic solutions. Peripheral vein, radial artery, and coronary sinus blood samples were drawn at aortic crossclamping, aortic crossclamp release, and 30 minutes after reperfusion. Human neutrophils were incubated with patients' plasma, and the expression of CD11b, CD18, and L-selectin was determined with flow cytometry.

RESULTS

In patients receiving crystalloid cardioplegic solutions, plasma samples collected from the coronary sinus at aortic clamp release and 30 minutes thereafter induced significantly higher expression of neutrophil CD11b and CD18 than plasma samples obtained from a peripheral vein or artery at the same time points. The expression of L-selectin on polymorphonuclear neutrophils was significantly reduced with plasma obtained 30 minutes after reperfusion as compared with samples collected at aortic crossclamp release. In the group receiving blood cardioplegia, no significant differences in CD11b, CD18, or L-selectin expression were found.

CONCLUSIONS

(1) Ischemia/reperfusion after coronary artery bypass grafting is associated with the release of factors capable of neutrophil activation from myocardium into the circulating blood. (2) The release of soluble stimuli for neutrophils during bypass grafting may be modified by the cardioplegic solution.

Evaluation of leukocyte-reducing arterial line filter (LG6) for postoperative lung function, using cardiopulmonary bypass

OBJECTIVE

To prevent postoperative pulmonary dysfunction, we have investigated the effect of the Leuko-Guard 6 leukocyte-reducing arterial line filter (LG6) on postoperative lung function.

METHODS

Twenty-six cases of adult valvular heart disease were included in this study. Thirteen cases were operated upon using the LG6 (Group LG), and 13 cases were operated upon using a conventional arterial line filter (Group C). Neutrophil, polymorphonuclear leukocyte elastase and lipoperoxide were measured for this study, and the lung function was evaluated using the Oxygenation Index (PaO2/FiO2).

RESULTS

Statistically significant differences were observed in neutrophil counts between Group LG and Group C (LG = 2225 +/- 572/mm3, C = 3157 +/- 1413/mm3, p = 0.04) at 5 minutes after the onset of cardiopulmonary bypass. In simultaneous blood sampling from the pulmonary artery and the pulmonary vein, the sequestration of neutrophil in the lung decreased in Group LG after the discontinuation of cardiopulmonary bypass. Release of polymorphonuclear leukocyte elastase from the lungs was significantly decreased (p = 0.04) in the Group LG at 1 hour post-bypass. Significant differences were observed in the Oxygenation Index between Group LG and Group C (LG = 398 +/- 72, C = 326 +/- 71, p = 0.019) at 3 hours post-bypass.

CONCLUSION

We concluded that LG6 improved the postoperative lung function, and its mechanism might be derived from the prevention of leukosequestration in the lungs that occurs during the rewarming phase due to selective absorption of activated leukocyte by the LG6.

Induced hypothermia in experimental pneumococcal meningitis

Pneumococcal meningitis resulting from Streptococcus pneumoniae has a death rate of 28% in adults. In severe head injury and stroke, inflammatory changes and intracranial hypertension are improved by induced hypothermia, which also is neuroprotective. We hypothesized that moderate hypothermia ameliorates inflammatory changes in experimental pneumococcal meningitis. Wistar rats were cooled systemically, and meningitis was induced by pneumococcal cell wall components. The increase of regional cerebral blood flow in the meningitis animals was blocked by hypothermia at 6 hours. The reduction of intracranial pressure correlated with temperature. The influx of leukocytes into the cerebrospinal fluid and levels of tumor necrosis factor alpha in the cerebrospinal fluid were decreased. Cooling the animals 2 hours after meningitis induction to 30.5 degrees C was also protective. We conclude that hypothermia is a new adjuvant approach to reduce meningitis-induced changes, in particular intracranial pressure, in the early phase of the disease.

A review of myocardial normothermia: its theoretical basis and the potential clinical benefits in cardiac surgery

Myocardial protection during cardiac surgery aims to preserve myocardial function while providing a bloodless and motionless operating field to make surgery easier. Myocardial protection is achieved by decreasing the oxygen needs using hypothermia and producing electromechanical cardiac arrest using potassium infusion which allows surgery to be performed on a non-beating heart. The deleterious effects of hypothermia include dysfunction of enzymatic systems, development of acidosis, a decrease in tissue oxygen delivery, an increase in blood viscosity and a decrease in erythrocyte deformability. Ninety percent of the decrease in oxygen consumption is obtained by inducing electromechanical arrest and inducing hypothermia has little additional benefit. Maintenance of systemic and myocardial normothermia reduces problems and provides a more physiological approach for cardiopulmonary bypass (CPB). The current results obtained using normothermic protection are very encouraging, and it is an easier inexpensive option. This review summarizes the current knowledge on the benefits of normothermia, based upon experimental and clinical studies.

Differential expression of neutrophil adhesion molecules during coronary artery surgery with cardiopulmonary bypass

BACKGROUND

Activation of neutrophil adhesion molecules and subsequent neutrophil adhesion to vascular endothelium are key events initiating inflammatory organ dysfunction after cardiopulmonary bypass and ischemic reperfusion.

OBJECTIVES

We sought to characterize neutrophil integrin CD11b and L-selectin activation associated with coronary artery bypass graft surgery and to determine whether neutrophil activation contributes to their sequestration on postbypass reperfusion.

METHODS

Twenty patients undergoing routine coronary artery bypass were studied. Heparinized whole blood was simultaneously sampled from a central venous line, aorta, coronary sinus, and right and left atrium before, during, and up to 20 minutes after cardiopulmonary bypass. Neutrophil counts were obtained, and neutrophil CD11b and L-selectin expression was determined by flow cytometric analysis in whole blood.

RESULTS

CD11b expression on circulating neutrophils increased during cardiopulmonary bypass, peaking at 145% of baseline level after release of the aortic clamp and then declined by 20 minutes after bypass (analysis of variance, P =.003). No change in neutrophil L-selectin expression was observed during cardiopulmonary bypass. Neutrophils responded to ex vivo stimulation by C5a and leukotriene B(4) during cardiopulmonary bypass but not at 24 hours after the operation. After reperfusion, neutrophil loss, but not local activation, was demonstrated in the coronary and pulmonary circulations.

CONCLUSIONS

Upregulated CD11b expression on neutrophils is likely to contribute to neutrophil sequestration in the heart and lungs after bypass, but neutrophil activation may be limited by their reduced responsiveness to agonist stimulation. CD11b represents a potential therapeutic target for diminishing inflammation after cardiac operations.

Inflammatory response to cardiopulmonary bypass using roller or centrifugal pumps

BACKGROUND

The inflammatory response in 29 patients undergoing coronary artery bypass grafting using either roller or centrifugal (CFP) pumps was evaluated in a prospective study.

METHODS

Patients were randomized in roller pump (n = 15) and CFP (n = 14) groups. Terminal complement complex activation (SC5b-9) and neutrophil activation (elastase) were assessed during the operation. Cytokine production (tumor necrosis factor-alpha, interleukin-6, interleukin-8) and circulating adhesion molecules (soluble endothelial-leukocyte adhesion molecule-1 and intercellular adhesion molecule-1) were assessed after the operation.

RESULTS

Release of SC5b-9 after stopping cardiopulmonary bypass and after protamine administration was higher in the CFP group (p = 0.01 and p = 0.004). Elastase level was higher after stopping cardiopulmonary bypass using CFP (p = 0.006). Multivariate analysis confirmed differences between roller pump and CFP groups in complement and neutrophil activation. After the operation, a significant production of cytokines was detected similarly in both groups, with peak values observed within the range of 4 to 6 hours after starting cardiopulmonary bypass. However, interleukin-8 levels were higher using CFP 2 hours after starting cardiopulmonary bypass (p = 0.02). Plasma levels of adhesion molecules were similar in both groups within the investigation period.

CONCLUSIONS

During the operation, CFP caused greater complement and neutrophil activation. After the operation, the inflammatory response was similar using either roller pump or CFP.

Leukocyte depletion during cardiac operation: a new approach through the venous bypass circuit

BACKGROUND

Leukocyte depletion recently has been introduced for cardiac surgical patients to attenuate leukocyte-mediated inflammation and organ reperfusion injury. We evaluated the feasibility of a new leukocyte depletion method in which systemic leukocyte depletion is achieved through the venous side of the cardiopulmonary bypass circuit under low blood flow.

METHODS

Forty cardiac surgical patients undergoing cardiopulmonary bypass were allocated randomly to a leukocyte depletion group (n = 20) and a control group (n = 20). In the depletion group, leukocyte filtration was achieved with two filter sets located between the venous drainage and the venous reservoir. Leukocyte filtration was commenced after the start of rewarming but before the release of the aortic cross-clamp, and it was driven by a spare roller pump of the heart-lung machine.

RESULTS

All the episodes of filtration went smoothly within a period of 10 minutes and with a blood flow rate of 400 mL/min. The mean leukocyte removal rate calculated at the end of filtration was 69%. Circulating leukocytes were reduced by 38% in the depletion group compared with the control group at the moment of cross-clamp release (4.3x10(9)/L versus 6.8x10(9)/L, p<0.05). The postoperative inflammatory response also was reduced as indicated by less production of interleukin-8 (p<0.05). Clinically, there was no significant difference between the two groups in postoperative PaO2 or pulmonary hemodynamics.

CONCLUSIONS

It is technically feasible to deplete circulating leukocytes through the venous side of the cardiopulmonary bypass circuit with a low blood flow rate. Future studies should focus on the duration and timing of leukocyte depletion to optimize the methodology of leukocyte depletion for cardiac surgical patients.

Effects of cardiopulmonary bypass on leukocyte and endothelial adhesion molecules

During the inflammatory response, triggered by cardiopulmonary bypass, interaction between activated leukocytes, platelets, and endothelial cells is mediated through the expression of three main groups of adhesion molecules: the selectins, the integrins, and the immunoglobulin superfamily. The selectins, which mediate the initial rolling of the leukocyte on the endothelium, are divided in three subgroups: L-selectin is expressed on all three leukocyte types, P-selectin is expressed on platelets and endothelial cells, and E-selectin is only expressed on endothelial cells. Integrins can be found on most cell types, consist of an alpha and a beta subunit and mediate firm adhesion of the leukocyte and migration into the tissues. They are classified into subgroups according to the type of their beta subunit. Immunoglobulins such as ICAM-1 and VCAM-1 are expressed mainly on endothelium and act as ligands for certain integrins. This review article summarizes the existing, and rapidly expanding, literature concerning the effects of cardiopulmonary bypass on the expression of leukocyte and endothelial adhesion molecules. Deeper understanding of the, behavior and the role of adhesion molecules during cardiopulmonary bypass may facilitate effective intervention in the inflammatory response process and suppression of its adverse effects.

Inflammatory response to cardiopulmonary bypass using two different types of heparin-coated extracorporeal circuits

Previous reports have highlighted the disparity in biocompatibility of two differently engineered heparin coatings during the cardiopulmonary bypass (CPB) procedure. The aim of this prospective study was to evaluate the impact of the difference in haemocompatibility provided by either the Duraflo II equipment or the Carmeda equipment in the terminal inflammatory response observed after coronary artery surgery. Thirty patients were randomly allocated to two groups to be operated on using either Duraflo II equipment (group I) or Carmeda equipment (group 2) for extracorporeal circulation (ECC). Initial inflammatory response was assessed by terminal complement complex activation (SC5b-9). The late inflammatory response observed in the postoperative period was assessed by measuring cytokine production (tumour factor necrosis (TNF alpha), interleukin IL-6, interleukin IL-8) and circulating concentrations of adhesion molecules (ELAM-1, ICAM-1). The release of SC5b-9 after CPB and after protamine administration was lower in group 2 than in group 1 (p = 0.0002 and p = 0.006, respectively). A significant production of cytokines was detected in both groups with peak values observed within the time range of 4-6 h after the start of CPB.

Increased expression of neutrophil and monocyte adhesion molecules LFA-1 and Mac-1 and their ligand ICAM-1 and VLA-4 throughout the acute phase of myocardial infarction: possible implications for leukocyte aggregation and microvascular plugging

OBJECTIVES

This study sought to evaluate expression of adhesion molecules on neutrophils and monocytes throughout the acute phase of myocardial infarction.

BACKGROUND

Neutrophil and monocyte counts increase within days from onset of acute myocardial infarction. Because leukocytes are recruited to the involved myocardial region, we postulated that these activated cells would display an increased expression of adhesion molecules necessary for effective endothelial transmigration.

METHODS

We measured the expression of neutrophil and monocyte lymphocyte function associated antigen-1 (LFA-1), Mac-1, very late after activation antigen-4 (VLA-4) and intercellular adhesion molecule-1 (ICAM-1) by flow cytometry throughout the acute phase of acute myocardial infarction in 25 patients and 10 age-matched control subjects.

RESULTS

Expression of Mac-1 on neutrophils increased significantly, whereas no expression of VLA-4 and ICAM-1 was detected. The expression of LFA-1, Mac-1, VLA-4 and ICAM-1 on the monocyte cell membrane in patients with an acute myocardial infarction was increased compared with that in control subjects by 22% (on day 7), 67%, 13% and 44% (all on day 4), respectively (all p < 0.001). Elevated density of monocyte-specific CD14 in the AMI versus the control group was also shown (30%, p < 0.001).

CONCLUSIONS

Increased expression of neutrophil and monocyte adhesion molecules may contribute to their adhesion to endothelium in the ischemic territory. This adhesion could feasibly precipitate vasoconstriction or add a local thrombotic effect due to tissue factor expression secondary to Mac-1 engagement. In addition, the manifestation of increased density of LFA-1 and Mac-1 by activated leukocytes with monocytes also expressing ICAM-1 suggests that leukocytes may form microaggregates that could cause microvascular plugging. This mechanism may facilitate the occurrence of the "no-reflow" phenomenon or slow coronary filling after acute myocardial infarction.

Comparative effects of continuous warm blood and intermittent cold blood cardioplegia on coronary reactivity

BACKGROUND

Cardioplegia is known to affect coronary vascular reactivity. We examined the effects of intermittent cold and continuous warm blood cardioplegia on beta-adrenoceptor-mediated, adenosine triphosphate-sensitive K+ (K+ATP)-channel-mediated, and endothelium-dependent relaxation and on the myogenic tone of coronary arterioles.

METHODS

Pigs were placed on cardiopulmonary bypass. Hearts were arrested for 1 hour with a cold blood cardioplegic solution administered intermittently (n = 12; iCB-CP) or with a warm blood cardioplegic solution delivered continuously (n = 12; cWB-CP). Selected hearts (n = 6 in each group) were then reperfused for 1 hour. In vitro relaxation responses of precontracted microvessels (50 to 160 microns) were studied in a pressurized no-flow state.

RESULTS

Relaxation in response to isoproterenol (beta-adrenergic agonist) was similar after iCB-CP and cWB-CP, whereas forskolin (adenylate cyclase activator)-induced relaxation was impaired more after iCB-CP than after cWB-CP. After reperfusion the respective responses were similar. Both iCB-CP and cWB-CP preserved receptor-mediated, endothelium-dependent relaxation in response to adenosine, 5'-diphosphate; non-receptor-mediated endothelium-dependent relaxation in response to A23187; endothelium-independent cyclic guanosine monophosphate-mediated relaxation in response to sodium nitroprusside, and K+ATP-channel-mediated relaxation. Relaxations in response to 8-bromo-cyclic guanosine monophosphate (a cyclic guanosine monophosphate-dependent protein kinase activator) and to 8-bromo-cyclic adenosine monophosphate (a cyclic adenosine monophosphate-dependent protein kinase activator) were impaired after iCB-CP alone and after reperfusion, whereas the respective responses were not affected after cWB-CP. Myogenic tone was decreased similarly after iCB-CP and cWB-CP but was not further altered after reperfusion. Cardiac function was similar after iCB-CP and cWB-CP.

CONCLUSIONS

These results suggest that cWB-CP is similar to iCB-CP in its ability to preserve endothelium-dependent relaxation and K+ATP-channel function. The superior preservation of beta-adrenergic-cyclic adenosine monophosphate-mediated coronary responses after cWB-CP is brief and associated with minimal improvement of myocardial function and myogenic tone.

Inflammatory response to cardiopulmonary bypass: mechanisms involved and possible therapeutic strategies

BACKGROUND

Recent study of the inflammatory reactions occurring during and after cardiopulmonary bypass (CPB) has improved our understanding of the involvement of the inflammatory cascade in perioperative injury. However, the exact mechanisms of this complex response remain to be fully determined.

METHODS

Literature on the inflammatory response to CPB was reviewed to define current knowledge on the possible pathways and mediators involved, and to discuss recent developments of therapeutic interventions aimed at attenuating the inflammatory response to CPB.

RESULTS

CPB has been shown to induce complement activation, endotoxin release, leukocyte activation, the expression of adhesion molecules, and the release of many inflammatory mediators including oxygen-free radicals, arachidonic acid metabolites, cytokines, platelet-activating factor, nitric oxide, and endothelins. Therapies aimed at interfering with the inflammatory response include the administration of pharmacologic agents such as corticosteroids, aprotinin, and antioxidants, as well as modification of techniques and equipment by the use of heparin-coated CPB circuits, intraoperative leukocyte depletion, and ultrafiltration.

CONCLUSIONS

Improved understanding of the inflammatory reactions to CPB can lead to improved patient outcome by enabling the development of novel therapies aimed at limiting this response.

Cerebral hemodynamics and metabolism during infant cardiac surgery. Mechanisms of injury and strategies for protection

There is an established link between congenital heart disease and acquired brain injury, which relates to the dependence of the nervous system on a consistent and responsive supply of oxygen and glucose. The advances in the field of infant cardiac surgery have presented new and different challenges to the arena of child neurology. This review provides an overview of the mechanisms of neurologic injury and cerebral hemodynamics and metabolism during cardiac surgery. This review discusses current and future strategies for the management of children with congenital heart disease.

The influence of cardiopulmonary bypass on cytokines and cell-cell communication

Cardiopulmonary bypass (CPB) is characterized by systemic endotoxemia immediately after its onset as well as the systemic release of proinflammatory cytokines, including tumor necrosis factor-alpha and the interleukins 1 and 6. Recent studies document that increased morbidity and mortality rates correlate with elevated systemic concentrations of these proinflammatory cytokines during adult and neonatal sepsis, following thoracoabdominal aortic aneurysm repair, as well as following CPB. These proinflammatory cytokines induce increased neutrophil and endothelial surface adhesive molecule expression, thereby promoting enhanced neutrophil-endothelial adherence. Increased neutrophil-endothelial adherence and subsequent neutrophil organ binding are thought to be a "final common pathway" of organ injury during clinical inflammatory conditions. Proinflammatory cytokines also increase cellular expression of inducible nitric oxide synthase, thus increasing cellular production of nitric oxide, a known inflammatory mediator. This review discusses recent evidence of the adverse effects of proinflammatory cytokine release during CPB and therapeutic modalities that can reduce the systemic concentrations of these mediators of inflammation.