The inflammatory response and extracorporeal circulation

The Inflammatory Response and Extracorporeal Circulation David Royston, FRCA

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.

T IS WELL RECOGNIZED that after major surgery there is an inflammatory response by the body and its organs and tissues. This response is more exaggerated after cardiac surgery, and there is little doubt that this extravagant response is responsible for a proportion of the mortality and morbidity associated with cardiac surgery. Certain organs and tissues are considered to be at higher risk of developing deranged function after the perfusion and operative period. At the greatest risk are the formed elements in the blood, 1,z the platelet and white cell, resulting in bleeding and abnormal organ and tissue functions. In particular, the pulmonary system, heart and myocardium, kidney and splanchnic bed, and the brain and cerebral circulation are specific targets that contribute to early postoperative morbidity and mortality. The perfusion period is thought to trigger this generalized inflammatory response by inappropriate activation of polymorphonuclear neutrophils, their adhesion to endothelial cells, and the subsequent release of cytotoxic products. These harmful effects are exerted by a wide spectrum of compounds, regardless of whether they act as triggers (such as complementderived products), mediators (cytokines, adhesion molecules), or effectors (proteolytic enzymes, oxygen free radicals, arachidonic acid metabolites) of the inflammatory cascade. Although the mortality for most cardiac surgical procedures has decreased and overall morbidity has been Significantly reduced, there is still no doubt that perfusion techniques and other factors related to this time can still be improved, leading, it is hoped, to a better patient outcome. This review discusses certain aspects related to this abnormal response, concentrating on the heart and pulmonary systems as affected organs. The aim of this article is to discuss various aspects of the inflammatory response together with some of the methods attempting to modify or prevent such abnormal function.

abnormal site or in abnormal amounts and contribute to tissue damage. It seems logica! that the identification of the pivotal process(es) in the genesis of these abnormalities must be addressed before any rational intervention can be initiated. Currently, a great many putative inflammatory mediators can be measured using a variety of commercially available immunoassays. However, it is possible that the effect measured may not be the cause of the unwanted effects in the host. This may in part be attributable to three confounding variables. First, these compounds are local messengers and the levels measured systemically may not reflect the concentration at the organ or tissue of interest. Second, the method of stimulation and mediation of effect may be different. For example, leukocyte recruitment to inflammatory foci is generally associated with cellular activation. However, recent evidence suggests that chemotactic agents can be divided into two classes: "pure chemoattractants" such as transforming growth factor-beta 1, which influence actin polymerization and movement but not oxidative burst and associated granular enzyme release,3 and "classical chemoattractants" such as activated complement fragments and intedeukins, which stimulate directed migration and also activation events. Third, the inflammatory responses may not be related to the agent measured per se but by the action of that agent to stimulate the production of mediators at other parts in the amplification pathway, for which measurement techniques are unreliable or are not as yet available. An example of this is the pulmonary hypertension that occasionally follows administration of protamine. Complement activation certainly occurs during this process.4 Prevention of this response can be achieved without affecting complement directly by a number of interventions. These include protease inhibition,5 free radical scavengers,6 and alterations in arachidonic acid metabolism and actions.6-9 Over the years, many individual systems and mediators have been the focus of intense scrutiny and investigation to determine if this was the mediator of the problems associated with cardiopulmonary bypass (CPB). However, as time has pro-

I

INITIATION OF ORGAN AND TISSUE INJURY DURING CARDIAC SURGERY

The main trigger for tissue and cell injury has always been thought to be the contact of the blood with the foreign surface of the pump-oxygenator system. However, other factors may be equally important. These include a period of tissue ischemia and reperfusion, hypothermia of the tissues, relative hypotension with nonpulsatile perfusion, relative anemia, the effects of the administration of blood and blood products, and effects of the agents used to allow control of coagulation, especially heparin and protamine. Finally, thrombin and other factors in the coagulation/fibrinolysis system may be generated either at an

Copyright© 1997by W.B. Saunders Company KEY WORDS: organ dysfunction, microvascular injury, pub monary circulation, myocardial circulation, complement, cytokines, neutrophils, adhesion molecules, integrins

From the Department of Anaesthesia, Harefield Hospital, Harefield, UK. Address reprint requests to David Royston, FRCA, Consultant in Cardiothoracic Anaesthesia, Harefield Hospital, Hill End Rd, Harefield, Middlesex, UB9 6JH, UK. Copyright © 1997 by W.B. Saunders Company 1053-0770/97/1103-001353.00/0

Journal of Cardiothoracic and Vascular Anesthesia, Vol 11, No 3 (May), 1997: pp 341-354

341

342

DAVID ROYSTON

gressed, epidemiological and laboratory-based data, together with improved pharmacological interventions, have produced a vast and complex array of, at times, apparently conflicting evidence. Indeed, some theories and concepts have traveled full circle over the years of investigation. An excellent example of this is the role of complement activation in the damaging processes associated with CPB. With regard to the inflammatory response, Fig 1 reflects a diagramatic overview of this convoluted problem. This figure represents the concept of the close interaction of the various celt types in the blood and microvasculamre that can interact between each other and are also bathed in a milieu of plasmatic and other factors involved in this process. With this in mind, the next part of the discussion focuses on the potential for various mechanisms to be involved in impaired cardiopulmonary function. Before discussing the various mediators and modulators in more detail, it may be wolthwhile to consider what may be the end-organ response to this increased mediator activity.

Inflammatory Responses and the Lung There is no doubt that the lung is in a unique position and therefore may be particularly susceptible to different methods and mechanisms of injury. It is one of the three sites in the body where the inside meets the outside. It is obvious therefore that the lung contains a number of special defense mechanisms and also special cell types that may be inappropriately triggered. Together with the skin and gut, the lung is a rich site for mast cells. In addition, there is a large population of macrophages, which are mobile and scavenge the alveoli and small respiratory bronchioles. Both of these cell types when activated are able to produce deleterious effects that may be categorized as lung inflammationleading to abnormal lung function. An example of this activation of lung inflammation after nonpulmonarytrauma comes from studies of peripheral ischemia and reperfusion. .^ca h o r m o n e . ~

Fig 1. Overview of the inflammatory response

These showed that reperfusion of the lower limbs after a period of ischemia was associated with an abnormal and injurious response within the pulmonary circulation. This was shown as an increase of protein flux into the lung together with an increase in lung water content. 1°,11 In addition to having a variety of different cell types in the lung, the pulmonary circulation and its architecture are different from that found in the skin or other microvascular beds. Whether human pulmonary vascular endothelium behaves differently from systemic endothelium when stimulated is not known. To highlight the problems associated with studying the inflammatory response to perfusion, certain aspects of pulmonary function that are affected by the inflammatory response should be considered and the following question addressed: Is the reduction in lung function, and specifically gas exchange after perfusion, a direct consequence of an inflammatory process?

Relationship betweenpostoperative lungfunctions and inflammation. The definition of inflammation is based on the physical signs and symptoms characterized as rubor, calor, tumor, and dolor. In the lung, these physical signs translate to an increase in the flux of solutes, especially proteins, and water across the microvasculature. There should also be an increased blood flow to the affected area. In the clinical setting, abnormalities of lung function are usually defined in terms of the gas exchanging properties of the lung and respiratory mechanics such as altered compliance, These factors are used in most scoring systems that define the severity of lung injury after an abnormal challenge. 12 In patients with severely deranged lung function classified as adult respiratory distress syndrome, solute flux measurements were unrelated to gas exchange, ~3-15 as was an index of increased interstitial w a t e r . 14 Studies that investigated the clearance of small solutes from the lung after cardiac surgery showed that the abnormality in solute flux was present for about 3 days postoperatively. There was still a significant gas exchange abnormality at 1 week) 6 Similarly, in a separate study, oxygenation and lung mechanics were unrelated to lung protein accumulation after cardiac surgery, 17Acute lung injury is also more likely to be associated with decreases in pulmonary blood flow and pulmonary hypertension. It is therefore unclear if the acute abnormality of lung function that occurs in association with cardiac surgery is directly related to a classic inflammatory response. A number of examples of known pathologies associated with cardiac surgery may be cited as possible causes of the impaired oxygenation (Table 1). General anesthesia is associated with a reduction in the functional respiratory capacity) 8 This may lead to altered shape and motion of the diaphragm and chest wall. In addition, atelectasis may result from lung compression by pleural effusions 19or after surfactant loss associated with cardiac surgery.2° Left lower lobe collapse is common after coronary artery bypass graft surgery. 19It is also well recognized that prolonged ventilation does not necessarily equate to impaired lung function alone. There may be defects in either the mechanics of breathing or ventilatory drive in patients who have a phrenic nerve injury, possibly related to the application of ice slush in the pericardium21 or a neurological deficit.

INFLAMMATORY RESPONSE AND EXTRACORPOREAL CIRCULATION Table 1. Causes of impaired Gas Exchange and Prolonged Respiratory Support Not Directly Related to the Use of Extracorporeal Circulation

parts. This initiation process is followed by an early amplification of the response. The following three highly interactive systems are discussed: factor XII/kallikrein system, complement activation, and generation of thrombin by the coagulation system.

Loss of lung volume Functional residual capacity reduced because of Anesthesia alone Obesity Poor respiratory excursions caused by pain Atelectasis Left lower lobe collapse Pleural effusion Loss of surfactant Prolonged ventilation Phrenic nerve injury Cold (ice in pericardium,) Mechanical trauma during surgery Neurological deficit/stroke

Time Course of Activation

Of further interest is the finding that gas exchange can be improved postoperatively by modification of the technique of anesthesia. A high (T1 - T2) thoracic epidural for operative and postoperative pain relief has been associated with significant improvements in patient well-being and particularly in aspects of lung function.22-24 The precise mechanism of this effect is unclear because the use of epidural analgesia was also associated with alterations in the stress hormone response, cellular activation, and modifications in the balance between coagulation and fibfinolysis. 24-27 This ability to modify the early defect in oxygenation and lung mechanics by methods unrelated to the conduct of CPB suggests that the perfusion system per se is not the trigger for this problem. Nonetheless, the next section deals with the process of contact activation and discusses the potential relevance of this to tissue injury and organ dysfunction. CONTACT/T|SSUE ACTIVATION

The exposure of blood to any foreign surface leads to the triggering of so-called contact activation systems. These systems can be thought of as primitive host defense mechanisms able to isolate and destroy a foreign substance or surface that the blood "sees." These systems are ancient in teleological terms but suggest some interesting tricks of nature. In particular, these systems have developed initiation processes whereby proteolyric enzymes are developed from nonenzymatic component

.....

One of the most intriguing problems related to these systems, and also for the other mediators and modulators of the inflammatory response, is the time course of their activation. The presumption must be that these systems will be activated in parallel; kallikrein and complement should be activated with the same rime course as they are both focused on the period of contact of the blood with the surface of the bypass system. Kallikrein activation occurs almost instantaneously at the start of bypass.28,29However, the concentration of C3a rises progressively to peak at the end of the bypass period3° (Fig 2). Thrombin generation is also greatest toward the end of the peffusion period. This may in part be related to a diminution of the effect of the inhibitor of this process (antithrombin III) at this dine, Factor XII/Kallikrein Activation After surface contact with a negatively charged surface, factor XII undergoes a conformational change and becomes bound to high-molecular-weight kininogen (HMWK). This complex can then bind to the surface. HMWK releases kallikrein (a protease with serine at its active site) and also bradykinin. Factor XIIa is also increased in concentration by a feedback system involving kallikrein.31,32 Kallikrein has a number of potential routes for activation of inflammatory cascades (Fig 3). Principally it is able to activate neutrophils to produce other phlogistic agents such as oxygen free radicals, 33 or proteolytic enzymes such as elastase and cathepsin. 34 Kallikrein and bradykinin stimulate the fibrinolytic system; kallikrein acts to activate pro-urokinase, bradykinin will induce the release of tissue type plasminogen activator from the endothelium. Bradykinin has a very short half-life in the plasma. This may be because of the rapid metabolism by angiotensinconverting enzyme in the pulmonary circulation. ~5,36With the pulmonary endothelium out of the system during the perfusion, this may lead to a rise in arterial concentrations of bradykinin. However, there are no data to support this notion. If there are Effector

Mediator

Trigger C3a

343

Kall[krein

TNF . . . . .

IL-6

,.. Elastase

.....

FreeRadical

100'

,\

75'

\,\

50' == 25'

2

4

6

1'2

2'4

Time ( hour )

3'0

2'4

48

7'2

Fig 2. "time course of changes in various biochemical endpoints thought to be involved in the inflammatory response to perfusion, The three sections of the diagram have a different time on the horizontal axis and assume that bypass lasts for 2 hours from time 0. The data show that for the various putative triggers, mediators, and effectors of inflammation, there is a dichotomy of both the time course and peak activity of the biochemical endpoint studied.

344

DAVID ROYSTON

Bradykinin

AlO,"ofPrekallikrein "~ i Factor XIIa Kallikrein- .._ f %"'FactorXII"J i NN~t-'~~ FactorIXa[ ~ sc~A ~~~C5( FactirVII Thrombin

Platelets

Plasmin Fibfin~olysis

raised concentrations of bradykinin, then this may lead to increased capillary permeability and the development of tissue edema. In addition, bradykinin may be an important mediator in cerebral ischemia. 37,38 Inhibition of this kallikreinforadykinin system is achieved with the use of serine protease inhibitors such as aprotinin, FOY, or Futhan. These serine protease inhibitors are predominantly known for their blood-sparing action) 9,4° They are also associated with a number of profound actions on the inflammatory processes associated with cardiac surgery.41 in particular, aprotinin will inhibit the foreign surface activation of kallikrein, leading to reduced release of proteolytic enzymes. 34 In addition, aprotinin administration is associated with a reduction in tissue edema formation in the heart, lung, kidney, gut, and muscle in an animal model of hypothermic circulatory arrest.42The serine pr0tease inhibitor Futhan has also been shown to prevent cerebral ischemia after injury by improving cerebral blood flow.43,44In the case of aprotinin, this action has been attributed to the effects of aprotinin on bradykinin formation. 37,38 This may also be the mechanism of action of aprotinin to reduce the incidence of stroke and neurological deficit seen after repeat cardiac surgery.41,45

Complement Activation The complement system is also a major factor in contact activation. The human system is made up of 19 proteins that can be activated by the so-called classical or alternate pathways. This latter pathway is predominantly involved in the complement activation by biomaterials. The third component of complement (C3) binds to the surface and releases C3a (a potent chemoattractant). The fragment of C3 remaining on the surface is joined by the inactive factor B and properidin to produce the active proteolytic enzyme C3 convertase. The C3 convertase will cleave the fifth component, C5, to generate the active fragment C5a and to continue the recruitment of the terminal effector sequence C5-C9. This C5-C9 sequence is able then to perform and generate the vasoactive, chemotactic, immunoregulatory, and cytolytic activities of complement. The factor XII/kallikrein and complement systems are able to

I

I

C3a

Whitecells

Fig 3. Diagrammatic representation of negative surface activation of thrombin, complement, and vasoactive amine mediators. Figure shows certain interactions between activation by foreign surface and activation of white cell, platelet, and coagulation.

interact to augment each other's actions. For example, kallikrein is able to cleave C5 directly to produce C5a, 46 and C3 may be cleaved by plasmin47 (Fig 3). Much endeavor in the first decades of the use of extracorporeal circulation was spent on trying to understand how foreign surface activation was related to the "global inflammatory response." Pivotal early studies by the Alabama group 3°,48 showed that the incidence and degree of deranged function of the heart, lung, and kidney could be related to the raised plasma concentration of the complement fragment C3a. This led to suggestions that complement activation was the pivotal key in the genesis of the damaging effects of cardiac surgery.49 Interventions designed to ameliorate the gas exchange abnormality that follows surgery and a period of perfusion have met with varying degrees of success and have not clarified whether the impaired lung function is the direct consequence of an inflammatory response as discussed above. Over time, the precise role of complement fragments in the initiation of pulmonary dysfunction has been questioned by a number of separate lines of research. The first showed that the probability of developing serious lung injury or not in patients with the sepsis syndrome was unrelated to the degree of activation of complement (shown by a rise in C3a concentration). C3a concentrations rose equally whether lung injury developed or not. 5° Secondly, and more recently, studies by the Johns Hopkins group have shown that abnormalities in indices of abnormal pulmonary function occur as frequently in dogs deficient in C3 as in those sufficient in C3. 51 These two lines of study may suggest that reducing activation of complement alone may confer little benefit to the patient with regard to their pulmonary function. In humans, there have been a number of studies to investigate whether complement activation and gas exchange can be improved by modifications to the oxygenator system. Various studies have suggested that complement activation is less with membrane than bubble oxygenators.52 However, current evidence suggests that there are no appreciable differences in outcome between these two systems with regard to pulmonary function. 53,54 Of particular interest are the data using heparin-

INFLAMMATORY RESPONSE AND EXTRACORPOREAL CIRCULATION

bonded or coated perfusion and oxygenator systems. These modifications have been shown to reduce the activation of certain inflammatory mediators and particularly complement activation. 554v However, despite this. there was no benefit or improvement in lung functions in this circumstance. 58-61 Notwithstanding the apparent lack of effect of reducing complement activation on pulmonary function, more recent data have concentrated on the effects of the cytotoxic terminal component of the complement system {the C5b-9 complex) and myocardial performance. Inhibition of production and activity of this complex, by the use of a protease inhibitor, was associated with a significant reduction in the deleterious effects of ischemia-reperfusion to the myocardium.62 It therefore may be that complement activation plays some part in the damaging effects of cardiac surgery related to myocardial but not pulmonary function after the period of surgery. This argument is strengthened by considering outcome differences between different kinds of oxygenators. Improved cerebral and myocardial outcome has been shown, for example, when a membrane is used compared with a bubble oxygenator. 54 Activation of Coagulation and Thrombin Generation The factor XII portion of the complex can release factor XIIa and Xllb: XIIa will start the intrinsic coagulation cascade by direct effects on factor XI, which again binds to the surface and can also prime factor VII to activate and augment the intrinsic cascade of coagulation. However, the precise role of this system in the generation of thrombin in relation to contact activation has been made less clear by recent observations in patients deficient in factor XII. As discussed earlier in this review, there are other potential stimuli to the development of abnormal organ and tissue functions than the contact activation process alone. Two of these are considered briefly, cytokines and adhesion molecules. It may be that these other processes may contribute directly to We injury or may "prime" the inflammatory process to produce a response of inappropriate magnitude or site.63 Of interest on this point was the finding by Stahl et a163that hollow-fiber oxygenators "prime" cells, thereby enhancing reactivity, more than membrane or bubble oxygenators. CYTOKINES IN CARDIAC SURGERY

Cytokines are a large and rapidly expanding group of polypeptides or glycopeptides with molecular weights from 5 to 70 kDa. They are produced by many different cell types; the major site of synthesis, however, appears to be cells of the macrophage and monocyte series, but virtually every nucleated cell can produce them in response to tissue injury. The cytokines can be either protective or damaging. Most cytokines act locally at extremely low concentrations (picomolar or femtomolar levels) in the vicinity of the production site, and under physiological conditions cytokines are undetectable or only found at low concentrations in peripheral blood. At low levels, the cytokines seem to be essential for optimal function of the defense and repair systems of the body. Some of the clinically most important cytokines also act systemically as hormones that modulate functions of cells at distant locations through blood and lymph circulation. These cytokines seem to be potentially harmful mediators under

345

pathological conditions such as major trauma, sepsis, and shock, where significant plasma levels may be reached. Important cytokines in this regard are the proinflammatory cytokines: interleukin 1 (IL-1), tumor necrosis factor, and interleukin 6 (IL-6). /L-6 After major, noncardiac surgery, IL-6 concentrations begin to increase within 2 to 4 hours after skin incision,64,65 and this is followed by peak concentrations 6 to 24 hours later. In uncomplicated cases, IL-6 levels return to preoperative values 3 to 5 days after surgery. The postoperative levels of IL-6 in patients with complications are reported to be significantly higher than in cases without complications. 66 In relation to cardiac surgery, a marked increase in IL-6 levels appears during and immediately after CPB. 67,6s Fiom the previous discussions, it may not come as a surprise that the rise in IL-6 concentration was unrelated tO the activation of the complement system69 (Fig 2). Peak concentration Occurs a few hours after the end of CPB with a gradual decrease toward preoperative levels in the following 24 hours. 69The characteristic IL-6 response to CPB has been shown with bubble and membrane oxygenators 67 after hypothermic as well as normothermic CPB 7° and after CPB performed with heparin-coated CPB circuits. 69 In one study of patients undergoing cardiac surgery, pretreatment with methylprednisolone (30 mg/kg) suppressed the CPB-induced increases in IL-6,71 whereas methylprednisolone given in the Same dose did not modify the IL-6 levels in patients only undergoing lung surgery.72 TNF Reports about the tumor necrosis factor (TNF) response to CPB have been conflicting. A significant increase in TNF, preventable b y dexamethasone administration,73 was shown after r6moval of the aortic cross-clarnp, 73-v5whereas no detectable plasma TNF was found in other studies] °,76,77 In a single study, TNF was detectable in some patients preoperatively, but no significant changes occurred during and after CPB. 7s Other studies have shown no association between systemic endot0xemia, mucosal acidosis, and release of TNE 79 The use of heparin-coated systems is associated with a reduced TNF production, s° whereas it is highest in children, in whom the response to bypass may be more pronounced,s~ In contrast to the IL-6 response to CPB, there is no evidence indicating that TNF is released in large amounts in response to CPB. However, animal studies have shown that very small amounts of TNF decrease myocardial performance. 82 /L-1 A transient increased IL-1 production of mononuclear cells in vitro was found after CPB with peak concentration after 24 hours, coincident with a peak in body temperature. 76 By contrast, significant increases in IL-1 concentration have not been detected in peripheral blood during and after CPB 67,69,83 Cytokines and adverse outcome. Studies relating absolute plasma cdncentrations of cytokines to organ dysfunction are fraught with the difficulties related to the local hormone nature of these mediators (Table 2). It has, for example, been argued

346

DAVID ROYSTON

Table 2. Relationship Between Raised Concentrations of Triggers/Mediators of the Inflammatory Response and Measured Outcome Variables

Trigger/Mediator

RaisedPlasma ConcentrationUnaffectedby

Complement fragments

IL-6

RaisedPlasma Concentration Decreasedby

PhysiologicalEffect Relatedto Reductionin PlasmaConcentration

Membrane oxygenator Heparin coating Serine protease inhibition

None apparent None apparent Improved myocardial performance

Methylprednisolone Serine protease inhibition Dexamethasone Heparin coating Hemofiltration

Improved myocardial performance Not measured Improved myocardial performance Not measured T MAP I Bleeding Intrapulmonary shunt

Oxygenator (bubble or membrane) Perfusion temperature Heparin coating

TNF Complement fragments and cytokines

that the lack of an observed increase in TNFc~ concentration is attributable to the avid local binding of this cytokine and thus a lack of systemic release. Nonetheless, one of the most recent publications suggests a relationship between inflammatory cytokines and myocardial ischemia and dysfunction after c0ronary artery bypass surgery. 84 Data from that study show a bimodal pattern of reiease of TNF~ after CPB (Fig 2), the main peak occurring within the first few hours and a second smaller peak occurring at 24 hours, Levels returned to normal by 48 hours postbypass. The study als0 presents data on a comparison of TNF levels measured at various sampling Sites. Of interest, the highest levels were detected in blood from the pulmonary artery, suggesting that release occurred systemically and that clearance occurred in the lung. Similar patterns of release were reported for IL-6 and IL-8. Peak 1L-6 concentration appeared to be related to the length of time the aorta was cross-clamped. Furthermore, when ventricular function was assessed postoperatively by transesophageal echocardiography, peak IL-6 levels were related to the degree of myocardial dysfunction. Whether this relationship with cytokine concentrations reflects a direct action of IL-6 on heart function or whether IL-6 is merely a nonspecific marker of a generalized inflammatory state is, however, not clear. The role of cytokines and especially IL-6 in postoperative cardiac dysfunction is strengthened by the report that administration of methylprednisolone, before surgery, was associated with reduced IL-6 production and improved cardiac performance. 8s A difficult point from a clinical perspective is that IL-6 appears to induce a negative inotropic action through the induction Of local nitric Oxide release. 86 This suggests that any deleterious effects of IL-6 on the heart can be prevented by the use of agents aimed to reduce nitric oxide production. This suggestion mitigates against the more regular use of nitrates and nitroso compounds, which augment nitric oxide release, during and after the period of surgery. Otlaer studies that have examined the effect of lowering concentrations of cytokines have used hemofiltration at the end of surgery. These Studies, in a pediatric setting, show that hemoflitration during rewarming was associated with a reduction in plasma concentrations of C3a, C5a, IL-6, and IL-8. In turn, this was associated with a higher arterial pressure, a reduction in bleeding, and also pulmonary shunting. 81

One confounding variable in the cytokine story is the provision of exogenous cytokines. It is becoming increasingly clear that blood and blood products contain significant amounts of cytokines. For example, recent studies have shown that platelet concentrates contain significant concentrations Of IL- 1, IL-6, and tumor necrosis factor.87-89What is more interesting is that reinfnsed shed blood may be deleterious to the patient. There is evidence for activation of neutrophils9° and generation of cytokines 91 in this reinfused blood. Reinfusion of shed blood is associated with the development of a hemostatic defect 92 and also evidence of myocardial ischemia93 after reinfusion. If subsequent studies show that these cytokines play a significant part in the inflammatory response to perfusion, then it is obvious that efforts will need to be redoubled to reduce bleeding and the need for blood products associated with cardiac surgery.

PHAGOCYTIC CELLS AS INITIATORS AND AMPLIFIERS OF THE INFLAMMATORY PROCESS

The role of activated neutrophils in tissue injury related to the perfusion period has been largely taken for granted in many studies and reviews. This may be largely because of the enormous body of data to show that neutrophils are the basic inflammatory cell and are "activated" during the period of bypass. The questions to ask are the relative importance of each of the aspects of this cell activation to the process and whether alterations in perfusion technique or pharmacological interventions have altered this activation, leading to improved outcome. As in the Case of the cytokines, the problems associated with direct implication of these cells in microvascular injury is related to the fact that altered performance in cells in the peripheral blood has been measured and not in those cells that may be directly involved in any injury. Nonetheless, using an animal model of neutrophil sequestration, Brown et a194showed that activated neutrophils are sequestered in normal lungs more than quiescent neutrophils in the inflamed lung. This increased sequestration was associated with a decrease in cell deformability and with increased migration of neutrophils into the air spaces. A second aspect to consider is that many of the individual aspects of these responses have been investigated in pure systems or in animal models, which may not be relevant m the

INFLAMMATORY RESPONSE AND EXTRACORPOREAL CIRCULATION

human having cardiac surgery. In particular, the patient having bypass is usually given a great number of different drugs and agents and is also subject to a number of manuvers not routine in the scientific setting of the laboratory investigator. An example of this effect is the use of heparin. This is obtained from the cells of animals. In the animal, it is not released systemically to act as an anticoagulant but appears to be a locally active antiinflammatoryagent as shown by the following illustrative examples: During the process of migration into tissues, leukocytes interact primarily with vascular endothelial cells, but they have also been shown to interact with each other. This cell-cell interaction can be stimulated by C5a and also by platelet-activating factor (PAF). Heparin will inhibit this cellcell interaction in a concentration-dependent manner.95 The C5a-induced responses were inhibited more potently by heparin. Administrationof intradermal histamine is associated with a wheal-and-flare response. This response is reduced significantly by sytemic heparinization.96 These data suggest that certain of the inflammatory pathways found in different circumstances from cardiac surgery, such as shock and sepsis, can be inhibited by the drugs and processes inherent in the techniques used during the bypass period. Caution is needed when extrapolating mechanisms of action between pathological states, because mechanisms important in trauma, for example, may play no part in the genesis of bypass-related morbidity.

White Cells and Tissue Injury The white cell can produce a deleterious effect on the microvasculature and tissues by one of three mechanisms: First, the cell can become more sticky because of expression of adhesion molecules or by a reduction in deformability. This process is appropriate when trying to wall off an invading pathogen. However, if there is an inappropriate activation, the cells may be activated to occlude the microvasculature. Activation of phagocytic cells can be induced by factors such as complement fragments, cytokines, or lipid mediators such as PAF. Second, the white cells can be stimulated to secrete a number of cytotoxic products, of which oxygen free radicals and proteolytic enzymes are most often implicated. These two processes are interactive in the white cell. Superoxide is generated on the cell surface from molecular oxygen and the enzyme nicotinamide-adeninedinucleotide phosphate oxidase. Superoxide is a relatively unreactive species but can be converted to the very aggressive singlet oxygen with the help of the enzyme myeloperoxidase. This latter enzyme together with the proteolytic enzymes elastase and cathepsin are stored in the azurophilic granule of the neutrophil. The third possible mechanism for white cell-induced tissue injury is after deactivation of the clumped white cells and restoration of the flow of oxygenated blood to produce a reperfusion injury after the period of ischemia. Increased neutrophil retention in the microcircuIation. Logic dictates that if a gradient of white cells across an organ or tissue is measured, then this implies uptake or egress of cells into the tissue and thus an inflammatory process. The question to ask is whether an increase in neutrophil retention is always pathological. The answer to this is in part related to "normal" or

347

physiological neutrophil retention, and to the lung and pulmonary circulation.

Neutrophils and Capillary Transit Physiology. The passage of neutrophils through the microcirculation depends on the balance between the forces that tend to retard their progress and the forces that act to move them through the vessels. This driving force depends on the local blood velocity. Obstruction of blood flow, by neutrophils that plug capillaries and impede the passage of erythrocytes, is well established in the systemic microcirculation and is enhanced by a reduction in blood flow.97 The transit of neutrophils through the pulmonary microcirculation may differ from that of the systemic circulation, because pressures within the pulmonary circulation are much lower than in the systemic circulation, and flow is pulsatile. 98 The arresting forces are those of adhesion and friction between the neutrophil and the endothelial cell and those related to the deformation of the neutrophil. Deformation of the neutrophil is necessary because it has to achieve a smaller effective diameter to squeeze through the smaller lung capillaries. The average diameter of the pulmonary capillaries of 5/am is less than that of the systemic capillaries at 6 lam. The diameter of the circulating neutrophils averages about 7 pro. Capillary diameters are, however, influenced by alveolar pressure, which gives rise to zones of differing capillary recruitment. Indeed, there is evidence that during interventions such as the Valsalva maneuver, often performed at the end of the period of perfusion as a manual hyperventilation of the lungs, there is increased sequestration of neutrophils in the pulmonary vasculature. 99 Similar are the effects of the application of positive endexpiratory pressure (PEEP). However, studies of the effects of PEEP on pulmonary neutrophil kinetics suggest that the effects of the PEEP are lost after about 30 minutes of continuous application. 1°° Other studies, in animals, also show a regional variation with longer cell transit times in the upper lung regions;I°1 this has been confirmed in humans. 1°2 These data seem to suggest that local blood velocity, and hence shear stress, are important determinants of the retention of neutrophils in vivo. This may have relevance to the increased sequestration of neutrophils in the pulmonary circulation in states in which blood flow is reduced, such as in shock and during CPB.103 A number of other studies have been reported on the transit of fluorescently labeled neutrophils observed through a transparent window in the periphery of the dog lung. Using this approach, Lien et al I°4 showed that neutrophils were sequestered exclusively in the pulmonary capillaries. The same group l°s also calculated that only a small number of obstructions (2%) were needed to stop most (71%) of the neutrophils in the capillaries. These neutrophils do not obstruct the passage of erythrocytes because the excess of capillary segments allows streaming of erythrocytes around them. Fewer than half of the neutrophils passed through with no delay from arteriole to venule. Most of the neutrophils that were delayed in the pulmonary capillaries stopped completely for varying lengths of time. 1°4,105The distribution of transit times of neutrophils in the capillaries was wide, ranging from under 2 seconds to over 20 minutes. More recently, Gebb et al 1°6 used high-magnification video-

348

microscopy in canine pulmonary capillaries to further identify the site of any sequestration of the neutrophil. Leukocytes observed rolling along the arteriolar walls were nearly spherical. To pass through the capillary bed, the leukocytes deformed into elongated shapes, and many leukocytes remained elongated after entering the venules. The significance of this deformation is discussed later. Even with this evidence of cell deformation, about 46% of the leukocytes passed through without stopping, 42% stopped in segments between junctions, and 12% stopped in areas of the endothelial cell junction. This suggests that normal neutrophils are not attracted to sites where they can diapede or migrate into the surrounding tissues. In contrast, lymphocyte migration may have some unique features not observed in studies of neutrophil transmigration. Using the same technique of video microscopy, it has been shown that recirculating lymphocytes formed abrupt adhesions, without any rolling or slowing, on lung microvascular endothelial cells. ~o7 Pathology. The neutrophil has the capacity to become more sticky and to be held up in the microcirculation by a number of means. The method attracting most recent attention is related to the expression on the cell surface of so-called adhesion molecules, discussed later. However, physical effects to reduce the deformability of the neutrophil should not be overlooked. Activation of neutrophils is associated not only with changes in their adhesion to each other and to other cells, but also with a rapid decrease in their deformability. In the pulmonary microcirculation, decreased deformability seems likely to be the initiating event producing neutrophil delay or entrapment, allowing adhesive interaction between neutrophils and endothelial ceils to proceed thereafter. The influence of the mechanical properties of neutrophils on blood flow in the systemic microcirculation is well recognized. Neutrophils are not easily deformed, l°s which leads to entrapment in the capillaries. If subsequently activated, these sequestered cells are thought to contribute to the pathogenesis of ischemic diseases 1°9 and to lung injury. 1°3,11° The deformability of a cell depends on: (1) surface areavolume relationships; (2) viscoelastic properties of the membrane; (3) viscoelastic properties of the cytoplasm. The neutrophil has excess surface area, caused by cell membrane ruffling, which allows the cell to change shape. Although the two cells are similar in size, the neutrophil, being spherical, has twice the volume of the erythrocyte. The spherical shape of the neutrophil is much less deformable than the biconcave disc shape of the erythrocyte. The neutrophil also contains a rigid nucleus, and its granular cytoplasm is 1,000 times more viscous than the cytoplasm of the erythrocyte. Because of these relationships, neutrophils are 700 times less deformable than erythrocytes. Both neutrophils and erythrocytes are known to have altered viscoelastic properties associated with a period of cardiopulmonary bypass. Most information concerning the red and white cells during perfusion is related to the first two factors. However, much is also known about the third aspect after neutrophil activation in other, nonperfusion-related, studies. During the bypass period, both red and white cell deformabilities are reduced. 1H,112The maximum reduction in deformability was observed on the day after surgery. The increase in retention of neutrophils in the microcirculation being related to altered deformability rather than expres-

DAVID ROYSTON

sion of cell adhesion molecules, discussed later, to become more "sticky" is suggested by certain studies. First, cells able to express CD18/ll are retained less on filters than less mature cells that are not able to express this epitope. H3 Second, stimulation of the neutrophil with the chemotactic peptide formyl-methionine-leucine-phenylalanine (FMLP) is associated with decreased deformability of that cell. This effect is unaltered by a monoclonal antibody directed at the common beta chain of the CD 18/11 epitope, but is abolished by cytochalasin D, which disrupts actin. 113 Third, neutrophils activated with FMLP and treated with cytochalasin D were not retained in the lung more than cells treated with FMLP alone. 114 Moreover, this latter study showed that populations of neutrophils with differing deformability had differing retention rates in the lungs: the more deformable the cells, the fewer were retained in the lungs. These studies emphasize the importance of the cell cytoskeleton in retention activity. Other factors have also been suggested as to why there may be decreased cell deformability. This may be caused by oxidation of the cell membrane reducing the proportion of unsaturated fatty acids, leading to decreased membrane fluidity. H5 Additional factors leading to altered deformability are related to alterations in membrane permeability and activity of ion pumps. 116 Few studies have addressed alterations in postoperative outcome and altered rheology associated with the period of perfusion, although some studies relate reduced red cell deformability to poor outcome in a number of cardiothoracic and vascular settings. 117 Decreased red cell deformability has been related to poorer myocardial outcome H8 and an increased likelihood of a cardiac arrhythmia postbypass. 119 Decreased white cell deformability has been suggested as an important factor in injury to various organs such as the heart, lungs, muscle, and splanchnic circulations, i20-~23 Administration of the serine protease inhibitor aprotinin in high doses will prevent decreased red and white cell deformability. 1~2 This ability is not seen with the so-called half-dose regimen. The ability of aprotinin therapy to alter cell rheology has not been explained on a mechanistic basis, nor has this action been related to any outcome variable, and so the significance of this observation is unclear.

ADHESION MOLECULES AND INFLAMMATION

Three principal families of adhesion receptors have been identified in leukocyte-endothelial cell adhesion: the integrins, those belonging to the immunoglobulin supergene family, and the vascular selectins. Recent reviews have considered adhesion of leukocytes, including neutrophils, to both endothelial and epithelial cells 124,125and their relevance to neutrophil emigration. These adhesion molecules occur in pairs that join the neutrophil to the endothelium. This is shown in Fig 4. There is an enormous current literature on the effects of these factors in relation to organ and tissue injury. Most have followed studies using blocking monoclonal antibodies. In particular, there is a considerable literature from animal and tissue culture studies concerning the beneficial effects of antibodies to the selectins to improve myocardial functional recovery or reduce infarction size after myocardial ischemia.

INFLAMMATORYRESPONSEAND EXTRACORPOREALCIRCULATION

349

Neutrophil 1" with warm or cold bypass 1" without and with heparin coating

No change with bypass L selectin

CD1 la/CD18

CD11b/CD18

CD11c/CD18

ICAM 1

ICAM 2

I

I Fig 4. Adhesion molecules on neutrophil and endothelial cell. The various pairs of molecules are shown together with factors, related to the perfusion period, that influence their expression and the time course of that expression, Adhesion molecules shown as hatched items are expressed on none activated/none stimulated cells.

I

P selectin

These data have not, as yet, been translated into benefits in humans. Nonetheless, CPB results in upregulation of adhesion receptors. 126,~27 Platelets are also activated by CPB to upregulate adhesion receptors for neutrophils and monocytes,128 and leukocyte-platelet conjugates are increased in the circulation during and after CPB.126,127

Integrins Integrins are transmembrane glycoproteins comprising large and smaller 13 chains. Among these are the leukocyte cell adhesion molecules (leuCAMs), which consist of a common chain; the CD18 antigen, associated with one of three c~chains: the CD 11 (a-c) antigens. CD 18/CD 11 a and CD18/CD 1 lb are constitutively present on the surface of human peripheral blood neutrophils. When cells are activated, augmentation of integrins occurs by recruitment from intracellular sources, from specific granules, and with the revelation of neoepitopes. These changes are usually associated with increased cell adhesivity. The effects of warm (~32°C) and cold (~27°C) bypass have also been investigated in humans and for each of the ~ Chains of the CD 11/CD 18 complex.129Warm bypass was associated with an early and sustained upregulation of CDllb. In contrast, hypothermia resulted in a less pronounced CD 1lb upregulation during this period. However, C D l l b expression increased sharply on warming so that 30 minutes after bypass there was no difference between the two temperature regimens. Changes in CDllc expression grossly paralleled those described for CDllb. There was no change in CD l l a in this study in either group. There is, however, a dichotomy between increased CD

E selectin

I

1" by cytokines at4hr 1" by hypoxia

I

1" by cytokines at 24 hr

Endothelium 18/CDll expression and increased cell adherence, because immunostaining of cell surface integrins alone may not precisely indicate the functional state of that cell's adhesiveness. ~3° The complexity of the role of these adhesion molecules in the inflammatory responses is graphically illustrated by the leukocyte adhesion molecule deficiency syndrome, which results from a congenital inability to express functional CD18/ CDll. 131 Neutrophils in these patients show impaired adherence in vitro, an increased intravascular half-life in vivo, but will sequester normally within the pulmonary vasculature and are released normally during vigorous exercise. I32 In addition, CD18/CDll does not appear to be necessary for the sequestration of normal neutrophils within a normal pulmonary vascular bed. 133 Mortality in patients with this congenital defect is usually a result of overwhelming mucous membrane and skin infection, and rarely by pneumonia.131 This apparent dichotomy of the effects of integrin expression depending on stimulus and the microvascular bed being examined is given further emphasis by other experimental studies. In these experiments, the endobronchial instillation of phorbol ester induced a neutrophil-dependent inflammatory response in the lung. The migration from the pulmonary capillary of the neutrophil but not the intravascular neutrophil sequestration within the lungs was inhibited by a monoclonal antibody to CD18. In contrast, intravascular sequestration and migration into the lungs in response to pneumococci instilled intrabronchially was not abolished by this antibody. TM When the same stimuli were applied to the skin, the response was again not abolished by the antibody. Thus, the mechanisms mediating neutrophil migration appear to not only be stimulus-specific, but also differ in the pulmonary and systemic circulations. This

350

may be because of differences in endothelial responsiveness or because of the proximity of other effector cells, such as epithelial and phagocytic cells, which enhance recruitment of neuu'ophils within the lungs. It would indeed be unusual for CD18 alone to be a central pivot in such mechanisms. The rarity of pneumonia in patients lacking functional CD 18/CD 11 in the leukocyte adhesion molecule deficiency syndrome confirms alternative, CD 18-independent, pathways for effective neutrophil recruitment. Thus, treatment with monoclonal antibodies directed against neutrophil-derived adhesion molecules may be of limited benefit.

Immunoglobulin Adhesion Molecules Ligands for these integrins are single-chain glycoproteins of the immunoglobulin supergene family known as intercellular adhesion molecules (ICAMs). The intravascular ligands for CD lla/CD 18 and CD llblCD 18 are, respectively, ICAM-1 and ICAM-2. As with the integrins, and as described by Whitten and Hill in this JOURNAL,both ICAM-1 and ICAM-2 are constitutively present on endothelium. 135,136

Selectins The selectins are prefixed by their source initial (E for endothelial, L for leukocyte, and P for platelet, although P-selectin is also expressed on endothelium). Activation of endothelium by proinllammatory mediators, such as cytokines or lipopolysaccharide, induces the sequential expression of E-selectin followed by the ICAMs. The relationship of these selectins to microvascular injury may be highly complex in relation to cardiac surgery. For example, the novel expression of E-selectin peaks around 4 hours after stimulation,137in contrast to the upregulation of vascular ICAM-1, which is maximal at around 24 hours/38 These effects are at times when many patients are being weaned from ventilation or being transferred from the ICU. However, the E-selectin response of the endothelium to cytokines can be enhanced by hypoxia. 139 These studies, examining the coronary circulation, also showed this response was slowed by hypothermia (to 25°C), despite the cell retaining tile transcription information for E-selectin expression (contained in the so-called NFKI3, promoter region). This allowed the normal and possibly increased expression of E-selectin on the cell surface after rewarrning. It is obvious that, at least for the coronary circulation, there may be periods of hypoxia, hypothermia, and stimulation by cytokines during and after cardiac surgery that may increase local expression of selectins. Neutrophil L-selectin is constitutive on the cell surface. It interacts with P-selectin to mediate adhesion and the roiling of neutrophils along the endothelium. By this means, shear stresses are reduced to allow neutrophils to develop stronger adhesion to endothelium. This brings the neutrophil to a halt in preparation for subsequent diapedesis. Of interest are studies that show that neutrophil rolling in the microcirculation was blocked by fucoidin, a polymer of sulfated L fucose (blocking both L- and P-selectin) but not by anti-P-selectin antibodies alone, m6 indicating that rolling leukocytes adhered to the endothelium by L-selectin. Antibodies to L-selectin also inhibit

DAVID ROYSTON

lymphocyte adhesion to the pulmonary microvasculature. 1°7 The effects of inhibition of L-selectin on systemic and pulmonary inflammation have been investigated. Fucoidin was able to inhibit neutrophil accumulation in both lung and peritoneal inflammation. Pretreatment with this compound reduced the number of neutrophils recruited into the lungs and peritoneal cavity by more than 95%. Fncoidin treatment also increased the systemic neutrophil count. The fact that L-selectin is usually expressed on the cell surface, even at rest, may explain why studies in humans have not shown an increased expression during or after a period of bypass. 129 REPERFUSiON INJURY

During cardiac surgery, there is always some component of ischemia/reperfusion attributable either to the underlyingpathophysiological process requiring operation (unstable angina or recent myocardial infarction) or to attempts to preserve an organ (usually the heart) while a structural abnormality (valve or congenital defect) is corrected or an organ transplantation performed. The heart has been extensively studied in regard to the effects of reperfusion with active white cells after a period of ischemia. It may also be that the heart is at specifically higher risk for attack from activated cells as damaged and ischemic myocardium expresses both chemotactic factors 14° and the terminal effector subunit of complement activation (C5-9). 141 When the acutely ischemic heart is reperfused with agranulocytic blood, the no-reflow phenomenon is completely abolished.121 In addition, the authors of these studies noted that exclusion of granulocytes had other beneficial actions. In particular, in the heart it is possible to show a direct relationship between the amount of tissue edema and the number of granulocytes in the local region of that edema. 121 In the absence of granulocytes, there is no edema. ~42 Furthermore, the number of ventricular arrhythmias is reduced, and ventricular fibrillation is abolished in hearts reperfused with agranulocytic blood) 42 Although granulocytopenia cannot easily be induced in humans, recent studies have suggested that leukocyte-depleted blood is useful in preventing reperfusion injury in the neonatal heart.143 WHITE CELL CYTOTOXIC PRODUCTS

The role of cytotoxic products in the organ and tissue injury that follows a period of perfusion is also unclear. Evidence for the involvement of such products is based on measuring increased plasma concentrations, and mainly by studies investigating the effects of agents known to inhibit or block these putative cytotoxic products. Measurement of plasma concentrations of cytotoxic agents and relating them to organ dysfunction raises certain issues related to timing of events in a manner similar to the triggers and mediators of the response (Fig 2). Plasma myeloperoxidase activity is increased after sternotomy and the administration of heparin and reaches a peak at the end of the bypass period. 144In stark contrast, the concentration of elastase, which is released from the same granules as myeloperoxidase, rises throughout the period of surgery. Elastase concentrations remain elevated over the first 48 postopera-

INFLAMMATORY RESPONSE AND EXTRACORPOREAL CIRCULATION

tive hours. These changes in elastase concentrations were unrelated to the development and resolution of abnormal organ, and specifically pulmonary, function. 145 Most approaches aimed at affecting neutrophil activity have shown improvement in myocardial recovery after ischemia, although it is not always clear if this is attributable to alteration in vasomotor function or t o other interactive effects. For instance, inhibition of neutrophil activation by prostacyclin has been shown to protect the myocardium. ~46 Specific antibodies aimed at suppressing neutrophil adhesion to injured areas have

351

also been shown to be of b e n e f i t 47 Oxygen radical scavenger therapy clearly improves recovery of function after myocardial ischemia-reperfusion. Examples of this include chelation of free iron using desferroxamine, 14s which reduces neutrophil-free radical production during cardiopulmonary bypass; whereas infusion of scavengers with the cardioplegia has a beneficial action on myocardial performance. 142,149,15° Nonetheless, it is unclear whether this effect is attributable tO altered vasomotor responses or to effects involving neutrophils, platelets, or reduced local injury from the reactive oxygen species.

REFERENCES

1. Edmunds LH Jr: Blood-surface interactions during cardiopulmonary bypass. J Card Surg 8:404-410, 1993 2; Royston D: Blood ceil activation. Semin Thorac Cardiovasc Surg 2:341-357, 1990 3. Cornish CJ, Devery JM, Poronnik R et ai: S100 protein CP-10 stimulates myeloid ceil chemotaxis without activation. J Cell Physiol 166:427-437, 1996 4. Morel DR, Zapol WM, Thomas SJ: C5a and thromboxane generation associated with pulmonary vast- and bronchoconstriction during protamine reversal of heparin. Anesthesiology 66:597-604, 1987 5. Kreil E, Montalescot G, Greene E, et al: Nafamstat mesilate attenuates pulmonary hypertension in heparin-protamine reactions. J Appl Physio167:1463-1471, 1989 6. Morel DR, Lowenstein E, Nguyenduy T, et al: Acute pulmonary vasoconstriction and thromboxane release during protamine reversal of heparin anticoagulation in awake sheep: Evidence for the role of reactive oxygen metabolites following nonimmnnological complement activation. Circ Res 62:905-915, 1988 7. Nuttall GA, Murray MJ, Bowie EJ: Protamine-heparin-induced pulmonary hypertension in pigs: Effects of treatment with a thromboxane receptor antagonist on hemodynamics and coagulation. Anesthesiology 74:138-145, 1991 8: Hobbhahn J, Conzen PF, Zenker B, et al: Beneficial effect of cyclooxygenase inhibition on adverse hemodynamic responses after protatn!ne. Anesth Analg 67:253-260, 1988 9. Conzen PE Habazettl H, Gutmann R, et al: Thromboxane mediation of pulmonary hemodynamic responses after neutralization of heparin by protamiiae in pigs. Anesth Analg 68:25-31, i989 10. Welbourn CR, Goldman G, Paterson IS, et al: Neutrophil elastase and oxygen radicals: Synergism in lung injury after hindiimb ischemia. Am J Physio1260:H1852-H1856, 1991 11. Welbourn CR, Goldman G, Paterson IS, et al: Pathophysiology of ischaemia reperfnsion injury: Central role of the neutrophil. Br J Surg 78:651-655, 1991 12. Moss M, Goodman R Heinig M, et al: Establishing the relative accuracy of three new definitions of the adult respiratory distress syndrome. Crit Care Med 23:1629-1637, 1995 13. Royston D, Braude S, Nolop KB: Failure Of aerosolised 99mTc DTPA clearance to predict outcome in patients with adult respiratory distress syndrome. Thorax 42:494-499, 1987 14. Rinaldo JE, Pennock B: Effects of ibuprofen on endotoxininduced alveolitis: Biphasic dose response and dissociation between inflammation and hypoxemia. Am J Med Sci 291:29-38, 1986 15. Rinaldo JE, Borovetz HS, Mancini MC, et al: Assessment of lung injury in the adult respiratory distress syndrome using multiple indicator dilution curves. Am Rev Respir Dis 133:1006-1010, 1986 16. Royston D, Minty BD, Higenbottam TW, et al: The effect of surgery with cardiopulmonary bypass on alveolar-capillary barrier function in human beings. Ann Thorac Surg 40:139-143, 1985 17. Macnaughton PD, Braude S, Hunter DN, et al: Changes in lung

function and pulmonary- capillary permeability after cardiopulmonary bypass. Crit Care Med 20:1289-1294, 1992 18. Westbrook PR, Smbbs SE, Sessler AD, et al: Effects of anesthesia and muscle paralysis on respiratory mechanics in normal man. J Appl Physiol 34:81-86, 1973 19. Kollef MH, Peller T, Knodel A, Cragun WH: Delayed pleuropulmonary complications following coronary artery revascularization with the internal mammary artery. Chest 94:68-71, 1988 20. Ellison LT, Duke JFd, Ellison RG: Pulmonary compliance follOWing open-heart surgery and its relationship to ventilation and gas exchange. Circulation 35:I217-I225, 1967 (suppl 4) 21. Wilcox P, Baile EM, Hards J, et al: Phrenic nerve function and its relationship to atelectasis after coronary artery bypass surgery. Chest 93:693-698, 1988 22. Christopherson R, Beattie C, Frank SM, et al: Perioperative morbidity in patients randomized to epidural or general anesthesia for lower extremity vascular surgery. Perioperative lschemia Randomized Anesthesia Trial Study Group [see comments]. Anesthesiology 79:422434, 1993 23. Liem TH, Hasenbos MA, Booij LH, Gielen MJ: Coronary artery bypass grafting using two different anesthetic techniques: Part 2: Postoperative outcome. J Cardiothorac Vasc Anesth 6:156-161, 1992 24. Liu S, Carpenter R, Neal J: Epidural anesthesia and analgesia: Their role in postoperative outcome. Anesthesiology 82:1474-1506, 1995 25. Liem TH, Booij LH, Gielen MJ, et al: Coronary artery bypass grafting using two different anesthetic techniques: Part 3: Adrenergic responses. J Cardiothorac Vasc Anesth 6:162-167, 1992 26. Breslow MJ, Parker SD, Frank SM, et al: Determinants of catecholamine and cortisol responses to lower extremity revascularization. The PIRAT Study Group. Anesthesiology 79:1202-1209, 1993 27. stenseth R, Bjella L, Berg EM, et al: Thoracic epidural analgesia in aortocoronary bypass surgery: II: Effects on the endocrine metabolic response. ActaAnaesthesiol Scand 38:834-839, 1994 28. Fuhrer G, Gallimore MJ, Heller W, et al: Aprotinin in cardiopulmonary bypass: Effects on the Hageman factor (FXII)--kallikrein system and blood loss. Blood Coagul Fibrinolysis 3:99-104, 1992 29. Heller W, Fuhrer G, Gallimore MJ, et al: Changes in the kallikrein-kinin-system after different dose regimens of aprotinin during cardiopulmonary bypass operation. Adv Exp Med Bio1247b:43-48, 1989 30. Chenoweth DE, Cooper SW, Hugli TE, et al: Complement activation during cardiopulmonary bypass: Evidence for generation of C3a and C5a anaphylatoxins. N Engl J Med 304:497-503, 1981 31. Colman RW, Mattler L, Sherry S: Studies on the prekallikrein (kallikreinogen)--kallikrein enzyme system of human plasma. II. Evidence relating the kaolin-activated arginiue esterase to plasma kallikrein. J Clin Invest 48:23-32, 1969 32. Colman RW, Mattler L, Sherry S: Studies on the prekallikrein

352

(kallikreinogen)--kallikreiri enzyme system of human plasma. I. Isolation and purification Of plasma kallikreins. J Clin Invest 48:11-22, 1969 33. Zimmerli W, Huber I, Bouma BN, et al: Purified human plasma kallikrein does not stimulate but primes neutrophils for superoxide production. Ttiromb Haemost 62: i 121-1125, 1989 34. Wachtfogel YT, Kucich U, Hack CE, et al: Aprotinin inhibits the contact, neutrophil, and platelet activation systems during simulated extractrporeal perfusion. J Thorac Cardiovasc Surg 106:1-9, 1993 35. Bakhle YS: Pulmonary metabolism of bradykinin analogues and the contribution of angiotensin converting enzyme to bradykinin inactivatio n in isolated lungs. Br J Pharmaco159:123-128, 1977 36. Junod AF: Metabolism of vasoactive agents in lung. Am Rev Respir Dis 115(6 Pt 2):51-57, 1977 37. Kamitani T, Little MH, Ellis EF: Evidence for a possible role of the brain kallikrein-kinin system in the modulation of the cerebral circulation. C!rc Res 57:545-552, 1985 38. Karniya T; Katayama Y, Kashiwagi E e t al: The role of bradykinin in mediating ischaemic brain edema in rats. Stroke 24:571576, 1993 39. Davis R, Whittington R: Aprotinin: A review of its pharmacology and therapeutic efficacy i n reducing blood loss associated with cardiac surgery. Drugs 49:954-983, 1995 40. Royston D: High-dose aprotinin therapy: A review of the first five years' experience. J Cardiothorac Vasc Anesth 6:76-100, 1992 41. Royston D: Preventing the inflammatory resporise to open-heart surgery: The role of aprotinin and other protease inhibitors. Int J Cardiol 53:Sll-$37, 1996 42. Aoki M, Jonas RA, Nomura F, et al: Effects of aprotinin on acut e recovery of cerebral metabolism in piglets after hypothermic Circulatory arrest. Ann Thorac Surg 58:146-153, 1994 43. Yanamoto H, Kikuchi H, Sato M, et al: Therapeutic trial Of cerebral vasospasm with the serine protease inhibitor, FUT-175, administered in the acute stage after subarachnoid hemorrhage. Neurosurgery 30:358-363, 1992 44. Yanamoto H, Kikuchi H, Okamoto S, et al: PreVentive effect of synthetic serine protease inhibitor, FUT-175, on cei:ebral vas0spasm in rabbits. Neurosurgery 30:351-356, 1992 45. Levy JH, Pifarre R, Schaff HV, et al: A muiticenter double-blind, placebo-controlled trial of aprofinin for reducing blood loss and the requirement for donor-blood transfusion in patients undergoing repeat coronary artery bypass grafting. Circulation 92:2236-2244, 1995 46. Wiggins R C, Giclas PC, Henson PM: Chemotactic activity generated from the fifth component o1"complement by plasma kallikrein of the rabbit. J Exp Med 153:1391-1404, 1981 47. Ward PA: A p!asmin-split fragment of C'3 as a new chemotactic factor. J Exp Med 126:189-206, 1967 48. Kirklin JK, Westaby S, Blackstone EH, et al: Complement and the damaging effects of cardiopulmonary bypass. J Thorac Cardiovasc Surg 86:845-857, 1983 49. Westaby S: Complement and the damaging effects of cardiopulmonary bypass. Thorax 38:321-325, 1983 (editorial) 50. Weinberg PF, Matthay MA, Weslen O, et al: Biologically active products of complement and acute lung injury in patients with the sepsis syndrome: Am Re v ResPir Dis 130:791-796, 1984 51. Gillinov AM, Redmond JM, Winkelstein JA, et al: Complement and nentmphi! activation during cardioPUlmonary bypass: A study in the complement-deficient dog. Ann Thorac Surg 57:345-352, 1994 52. Utley JR: Pathophysiology of cardi0pulmonary bypass: Current issues. J Card Surg 5:177-189, 1990 53. Sundaram S, Courtney JM, Taggart DR et al: Biocompatibility of cardiopulmonary bypass: Influence on blood compatibility of device type, mode of blood flow and duration of application. In t J Arfif Organs 17:1i8-128, 1994 54. Nilsson L, Tyden H, Johansson O, et al: Bubble and membrane oxygenators: Comparison Of postoperative organ dysfunction with

DAVID ROYSTON

special reference to inflammatory activity. Scand J Thorac Cardiovasc Surg 24:59-64. 1990 55. Sverlnevig JL. Geiran OR. Karlsen H. et al: Complement activation during extracorporeal circulation: In vitro comparison of Duraflo II heparin-coated and uncoated oxygenator circuits. J Thorac Cardiovasc Surg 106:466-472. 1993 56, Borowiec JW. BylockA, van der Linden J. et al: Heparin coating reduces blood cell adhesion to arterial filters during coronary bypass: A clinical study. Ann Thorac Snrg 55:1540-1545. 1993 57. Gu YJ. van Oeveren W. Akkerman C. et al: Heparin-coated circuits reduce the inflammatory response to cardiopulmonary bypass. Ann Thorac Surg 55:917-922. i993 58. Francalancia NA, Aeba R. Yousem SA. et al: Deleterious effects of cardiopulmonary bypass on early graft function after single lung allotransplantation: Evaluation of a heparin-coated bypass circuit. J Heart Lung Transplant 13:498-507. 1994 59. Ovrum E. Mollnes TE. Fosse E. et al: Complement and granulocyte activation in two different types of heparinized extracorporeal circuits. J Thorac Cardiovasc Surg 110:1623-1632. 1995 60. Moen O. Fosse E. Brockmeier V. et al: Disparity in blood activation by two different heparin-coated cardiopulmonary bypass systems. Ann Thorac Snrg 60:1317-1323. 1995 61. te Velthuis H. Jansen PG. Hack CE, et al: Specific complement inhibition with heparin-coated extracorporeal circuits. Ann Thorac Surg 61:1153-1157, 1996 62. Homeister JW. Satoh R Lucchesi BR: Effects of complement activation in the isolated heart: Role of the terminal complement components. Circ Res 71:303-319. 1992 63. Stahl RE Fisher CA. Kucich U. et al: Effects of simulated extracorporeal circulafion on human leukocyte elastase release, superoxide generation, and procoagulant activity. J Thorac Cardiovasc Snrg 101:230-239. 1991 64. Sfienkin A. Fraser WD, Series J. et al: The serum interleukin 6 response to elective surgery. Lymphokine Res 8:123-127. 1989 65. Pullicino EA, Carli F, Poole S, et al: The relationship between the circulating concentrations of interleukin 6 (IL-6). tumor necrosis factor (TNF) and the acute phase response to elective surgery and accidental injury. Lymphokine Res 9:231-238. 1990 66. Oka Y. Murata A. Nishijima J. et al: Circulating interleukin 6 as a useful marker for predicting postoperative complications [published erratum appears in Cytokine 1993 5:89-90. 1993]. Cytokine 4:298-304. 1992 67. Butler J. Chong GL, Baigrie RJ. et al: Cytokine responses to cardiopulmonary bypass with membrane and bubble oxygenation. Ann Thorac Snrg 53:833-838, 1992 68. Kawamura T. Wakusawa R. Okada K, et al: Elevation of cytokines during open heart surgery with cmdiopulmonary bypass: Participation of interleukin 8 and 6 in reperfusion injury [see comments]. Can J Anaesth 40:1016-1021, 1993 69. Steinberg JB, Kapelanski DE Olson 1D, Weiler JM: Cytokine and complement levels in patients undergoing cardiopulrnonary bypass. J Thorac CardioVasc Surg 106:1008-1016. 1993 70. Frering B. Philip I. Dehoux M. et al: Circulating cytokines in patients undergoing normothermic cardiopulmonary bypass. J Thorac Cardiovasc Surg 108:636-641, 1994 71. Inaba H, KochiA. Yorozu S: Suppression by methylprednisolone of augmented plasma endotoxin-like activity and interleukin-6 during cardiopulmonary bypass. Br JAnaesth 72:348-350. 1994 72. Tonnesen MG. Anderson DC. Springer TA, et al: Adherence of neutrophils to cultured human microvascular endothelial cells: Stimulation by chemotactic peptides and lipid mediators and dependence upon the Mac-l, LFA-1, p150,95 glycoprotein family. J Clin Invest 83:637646. 1989 73. Jansen NJ. van Oeveren W, van den Broek L. et al: Inhibition by

INFLAMMATORY RESPONSE AND EXTRACORPOREAL CIRCULATION

dexamethasone Of the reperfusion phenomena m cardiopulmonary bypass [see comments]. J Thorac Cardiovasc Surg 102:515-525. 1991 74. Jansen NJ. van Oeveren W. Gu YJ, et al: Endotoxin release and tumor necrosis factor formation during cardiopalmonary bypass [see comments]. Ann Thorac Surg 54:744-747. 1992 75. Tonz M. Mihaljevic T, yon Segesser LK. et al: Normothermia versus hypothermia during cardiopulmonary bypass: A randomized. controlled trial. Ann Thorac Surg 59:137-143. 1995 76. Haeffner-Cavaillon N. RousseUier N, Ponzio O. et al: Induction of interleukin-I production in patients undergoing cardiopulmonary bypass. J Thorac Cardiovasc Surg 98:1100-1106. 1989 77. Markewitz A. Faist E, Lang S. et al: Regulation of acute phase response after cardiopulmonary bypass by immunomodulation. Ann Thorac Surg 55:389-394, 1993 78. Butler I. Parker D, Pillai R, et al: Effect of cardiopulmonary bypass on systemic release of neutrophil elastase and tumor necrosis factor [published erratum appears in J Thorac Cardiovasc Surg 105: 1056. 1993]. J Thorac Cardio'easc Surg 105:25-30. 1993 79 Andersen LW. Landow L. Baek L, et al: Association between gastric intraniucosal pH and splanchnic endotoxin, antibody to endotoxin, and tumor necrosis factor-alpha concentrations in patients undergoing cardiopulmonary bypass. Crit Care Med 21:210-217, 1993 80. Yamada H. Kudoh I. Hirose Y. et al: Heparin-coated circuits reduce the formation Of TNFa during cardiopnlmonary bypass. Acta Anaesth, Scand 40:3 l 1-317, 1996 81. Journois D. Pouard E Greeley W. et al: Hemotiltration during cardiopulmonary bypass in paediatric cardiac surgery: Effects on hemostasis, cytokines and complement components. Anesthesiology 81:1181-1189. 1994 82. Hansen PR, Svendsen JH, Hoyer S. et al: Tumor necrosis factor-alpha increases myocardial microvascular transport in vivo. Am J Physio1266:H60-H67. 1994 83. CavaiUon JM, Munoz C. Fitting C, et al: Circulating cytokines: The tip of the iceberg? Circ Shock 38:145-152. 1992 84. Hennein HA. Ebba H. Rodriguez JL. et al: Relationship of the proinflammatory cytokines to myocardial ischemia and dysfunction after uncomplicated coronary revascularization. J Thorac Cardiovasc Surg 108:626-635. 1994 85. Kawamura 1". Inada K. Okada H: Methylprednisolone inhibits increase of interleukin 8 and 6 during open heart surgery. Can J Anaesthesio142:399-403. 1995 86. Finkel MS, Oddis CV, Jacob TD, et al: Negative inotropic effects of cytokines on the heart mediated by nitric oxide. Science 257:387-389 87. Muylle L. Joos M. Wouters E. et al: Increased tumor necrosis factor alpha (TNF alpha), interleukin 1. and interleukin 6 (IL-6? levels in the plasma of stored platelet concentrates: Relationship between TNF alpha and [L-6 levels and febrile transfusion reactions. Transfusion 33:195-199. 1993 88. Muylle L. Peetermans ME: Effect of prestorage leukocyte removal on the cytokine levels in stored platelet concentrates. Vox Sang 66:14-17. 1994 89. Stack G. Snyder EL: Cytokine generation in stored platelet concentrates. Transfusion 34:20-25. 1994 90. Connall TE Zhang J. Vaziri ND. et al: Leukocyte C D l l b and CD18 expression are increased in blood salvaged for autotransfusion Am Surg 60:797-800:1994 91. Arnestad JP, Bengtsson A. Bengtson JP, et al: Formation of cytokines by retransfusion of shed whole blood. Br J Anaesth 72:422425. 1994 92. de Haan J. Boonstra PW. Monnink SH. et al: Retransfusion of suctioned blood during cardiopulmonary bypass impairs hemostasis. Ann Thorac Surg 59:901-907, 1995 93. Hannes W. Keilich M. Koster W, et al: Shed blood autotransfusion influences ischemia-sensitive laboratory parameters after coronary operations. Ann Thorac Surg 57:1289-1294. 1994

353

94. Brown GM, Drost E, Selby C, et al: Neutrophil sequestration in rat lungs. Ann N Y Acad Sci 624:316:317, 1991 95. Teixeira MM, Rossi AG, Hellewell PG: Adhesion mechanisms involved in C5a-induced eosinophil homotypic aggregation. J Leukoc Biol 59:389-396, 1996 96. Bowler SD, Smith SM, Lavercombe PS: Heparin inhibits the immediate response to antigen in the skin and lungs of allergic subjects. Am Rev Respir Dis 147:160-163, 1993 97. Schmid Schonbein GW, Usami S, Skalak R, et al: The interaction of leukocytes and erythrocytes in capillary and postcapillary vessels. Microvasc Res 19:45-70, 1980 98. Wasserman K, Butler J, Van Kessel A: Factors affecting the pulmonary capillary blood flow pulse in man. J Appl physiol 21:890900, 1966 99. Markos J, Hooper RO; Kavanagh Gray D, et al: Effect of raised alveolar pressure on leukocyte retention in the human lung. J Appl Physio169:214-221, 1990 t00. Markos J, D0erschuk CM, English D, et al: Effect of positive end-expiratory pressure on leukocyte transit in rabbit lungs. J Appl Physio174:2627-2633, 1993 101. Dnerschuk CM, Allard MF, Martin BA, et al: Marginated pool of neutrophils in rabbit lungs. J Appl Physio163:1806-1815, 1987 102. MacNee W, Martin BA, Wiggs BR, et al: Regional PUlmonary transit times in humans. ~fAppl Physio166:844-85fl, 1989 103. Donnelly SC, Haslett C: Cellular mechanisms of acute lung injury: Implications for future treatment in the adult respiratory distress syndrome. Thorax 47:260-263, 1992 (editorial) 104. Lien DC, Wagner WW Jr, Capen RL, et al: Physiological neutrophil sequestration in the lung: Visual evidence for localization in capilIaries. JAppl Physio162:1236-1243, 1987 105. Lien DC; Worthen GS, Capen R L, et al: Neutrophil kinetics in the pulmonary microcirculation: Effects of pressure and flow in the dependent lung. Am Rev Respir Dis 141:953-959, 1990 106. Gebb SA, Graham JA, Hanger CC, et al: Sites of leukocyte sequestration in the pulmonary microcirculation. J Appl Physio179:493497, 1995 107. Li X, Abdi K, Rawn J, et al: LFA-1 and L-selectin regulation of recirculating lymphocyte tethering and rolling on lung microvascUlar endothelium. Am J Respir Cell Mol Biol 14:398-406, 1996 108. Schmid Schonbein GW, Sung KL, Tozeren H, et al: Passive mechanical properties of human leukocyte s. Biophys J 36:243-256, 1981 109. Ernst E Hammerschmidt DE, Bagge U, e t al: Leukocytes and the risk of ischemic diseases. JAMA 257:2318-2324, 1987 ll0. Warshawski FJ, Sibbald WJ, Driedger AA, et al: Abnormal neutrophil-pulmonary interaction in the adult respiratory distress syndrome: Qualitative an d quantitative assessment of pulmonary nentrophil kinetics in humans with in vivo lnindium nentrophil scintigrapby. Am Rev Respir Dis 133:797-804, 1986 111. Ekestrom S, Koul BL, Sonnenfeld T: Decreased red cell deformability following open-heart surgerY. Scand J Thorac Cardiovasc Surg 17:41-44, 1983 112. Liu B, Belboul A, A1-Khaja N, et al: Effect of high-dose aprotinin on blood cell filterability in association with cardiopulmonary bypass. Coronary Artery Disease 3:129-132, 1992 113. Erzurum SC, Kus ML, Bohse C, et al: Mechanical properties of HL60 cells: Role of stimulation and differentiation in retention in capillary-sized pores.' Am J Respir Cell Mol Biol 5:230-241,1991 114. Worthen GS, Schwab Bd, Elson EL, et al: Mechanics of stimulated neutrophils: Cell stiffening induces retention in capillaries. Science 245:183-186, 1989 115. Hirayama T, Folmerz R Hansson R, et al: Effect of oxygen free radicals on rabbit and human erythrocytes: Studies on cellular deformability. Scand J Thorac Cardiovasc Snrg 20:247-252, 1986 116: Hirayama T, Herlitz H, Jonsson O, et al: Deformability and

354

electrolyte changes of erythrocytes in connection with open heart surgery. Scand J Thorac Cardiovasc Surg 20:253-259, 1986 117. Belboul A. al Khaja N, Bergman R et al: Blood cell filtrability: Reference values and clinical applications. Scand J Clin Lab Invest 50:297-302, 1990 118. Roberts D. Belboul A. A1 khaja N. et al: Changes in blood cell rheology associated with acute rejection following cardiac transplantation. Transplant Proc 22:1444-1445.1990 119. Hirayama T. Roberts D. Allers M. et al: Association between arrhythmias and reduced red cell deformability following cardiopulmonary bypass. Scand J Thorac Cardiovasc Surg 22:179-180. 1988 120. Bagge U. Amundson B. Lauritzen C: White blood cell deformability and p!ugging of skeletal muscle capillaries in hemorrhagic shock. Acta Physiol Scand 108:159-163. 1980 121. Engler RL. Dahlgren MD. Morris DD. et al: Role of leukocytes in response to acute myocardial ischemia and reflow in dogs. Am J Physiol 251:H314-H323. 1986 122. Braide M. Amundson B. Chien S. et al: Quantitative studies on the influence of leukocytes os the vascular resistance in a skeletal muscle preparation. Microvasc Res 27:331-352. 1984 123. Wilson JW. RatliffNB. Mikat E. et al: Leukocyte changes in the pulmonary circulation: A mechanism of acute pulmonary injury by various stimuli. Chest 59:36S. 1971 (suppl) 124. Albelda SM. Buck CA: [ntegrins and other cell adhesion molecules. FASEB J 4:2868-2880. 1990 125. Albelda SM: Endothelial and epithelial cell adhesion molecules. Am J Respir Cell Mol Biol 4:195-203.1991 126. Rinder CS. Bonan JL. Rinder HM. et al: Cardiopulmonary bypass induces leukocyte-platelet adhesion. Blood 79:1201-1205.1992 127. Rinder CS, Gaal D. Student LA. et al: Platelet-leukocyte activation and modulation of adhesion receptors in pediatric patients with congenital heart disease undergoing cardiopulmonary bypass. J Thorac Cardiovasc Surg 107:280-288. 1994 128. Rinder CS. Bohnert J. Rinder HM, et al: Platelet activation and aggregation during cardiopulmonary bypass. Anesthesiology 75:388393, 1991 129. Le Deist F. Menasche l~ Kucharski C. er al: Hypothermia during cardiopulmonary bypass delays but does not prevent neutrophilendothelial cell adhesion: A clinical study. Circulation 92:Ii354-Ii358. 1995 (suppl 9) 130. Philips MR, Buyon JR Winchester R, et al: Up-regulation of the iC3b receptor (CR3) is neither necessary nor sufficient to promote net~trophil aggregation. J Clin Invest 82:495-501, 1988 131. Anderson DC, Springer TA: Leukocyte adhesion deficiency:An inherited defect in the Mac-l, LFA- 1, and p150,95 g!ycoproteins. Annu Rev Med 38:175-194, 1987 132. Davies KA, Toothill VJ, Savill J, et al: A 19-year-old man with leucocyte adhesion deficiency: In vitro and in vivo studies of leucocyte function. Clin Exp Immunol 84:223-231, 1991 133. Yoder MC, Checkley LL, Giger U, et al: Pulmonary microcirculatory kinetics of neutrophils deficient in leukocyte adhesion-promoting glycoproteins. J Appl Physio! 69:207-213, 1990 134. Doerscbuk CM, Winn RK, Coxson HO, et al: CD18-dependent and -independent mechanisms of neutrophil emigration in the pulmo-

DAVID ROYSTON

nary and systemic microcirculation of rabbits. J Immunol 144:23272333, 1990 135. Rothlein R, Dustin ML, Marlin SD, et al: A human intercellular adhesion molecule (ICAM- 1) distinct from LFA- 1. J Immunol 137:12701274, 1986 136. Staunton DE, Dustin ML, Springer TA: Functional cloning of ICAM-2, a cell adhesion ligand for LFA-1 homologous to ICAM-1. Nature 339:61r64, 1989 137. Bevilacqua MR Stengelin S, Gimbrone MAJr, et al: Endothelial leukocyte adhesion molecule 1: An inducible receptor for neutrophils related to complement regulatory proteins and lectins. Science 243:1160-1165, 1989 138. Dustin ML, Rothlein R, Bhan AK, et al: Inductio n by IL 1 and interferon-gamma: Tissue distribution, biochemistry, and function of a natural adherence molecule (ICAM- 1). J Immunol 137:245-254, 1986 139. shen I, Verrier E: Expression of E-selectin on coronary endothelium after myocardial ischemia and reperfusion. J Card Surg 9:43%441, 1994 (suppl) 140. Hartmann JR, Robinson JA, Gnnnar RM: Chemotactic activity in the coronary sinus after experimental myocardial infarction: Effects of pharmacologic interventions on ischemic injury. Am J Cardiol 40:550-555, 1977 141. Schafer H, Mathey D, Hugo F, et al: Deposition of the terminal C5b-9 complement comPlex in infarcted areas of human myocardium. J Immunol 137:1945-1949, 1986 142. Weiss S: Oxygen, ischaemia and inflammation. Acta Physio1 Scand 548:9-37, 1986 (suppl) 143. Breda MA, Drinkwater DC, Laks H, et al: Prevention of reperfusion injury in the neonatal heart with leukocyte-depleted blood. J Thorac Cardiovasc Surg 97:654-665, 1989 144. Faymonville ME, Pincemail J, Duchateau J, et al: Myeloperoxidase and elastase as markers of leukocyte activation during cardiopulmonary bypass in humans. J Thorac Cardiovasc Surg 102:309-317, 1991 145. Mair P, Mair J, Seibt I, et al: Plasma elastase concentrations and pulmonary function after cardiopulmonary bypass. J Thorac Cardiovasc Surg 108:184-185, 1994 (letter) 146. Simpson pJ, Mitsos SE, Ventura A, et al: Prostacyclin protects ischemic reperfused myocardium in the dog by inhibition of neutrophil activation. Am Heart J 113:129-137, 1987 147. Vedder NB, Winn RK, Rice CL, et al: A monoclonal antibody to the adherence-promoting leukocyte glycoprotein, CD18, reduces organ injury and improves survival from hemorrhagic shock and resuscitation in rabbits. J Clin Invest 81:939-944, 1988 148. Menasche R Pasquier C, Bellucci S, et al: Deferoxamine reduces neutrophil-mediated free radical production during cardiopulmonary bypass in man. J Thorac Cardiovasc Surg 96:582-589, 1988 149. Menasche E Grousset C, Gauduel Y, et al: Enhancement of cardioplegic protection with the free-radical scavenger peroxidase. Circulation 74:Iii138-Iii144, 1986 150. Menasche R Grousset C, Gauduel Y, et al: A c0mParative study of free radical scavengers in cardioplegic solutions: Improved protection with peroxidase. J Thorac Cardiovasc Surg 92:264-271, 1986