Conventional Mechanical Ventilation Is Associated with Bronchoalveolar Lavage-induced Activation of Polymorphonuclear Leukocytes: A Possible Mechanism to Explain the Systemic Consequences of Ventilator-induced Lung Injury in Patients with ARDS

Background: Protective ventilatory strategies have resulted in a decreased mortality rate in acute respiratory distress syndrome, but the underlying mechanisms remain unclear. The authors hypothesized that (1) mechanical ventilation modulates activation of polymorphonuclear leukocytes (PMNs), (2) the consequent release of proteinases is correlated with a systemic inflammatory response and with multiple organ dysfunction, and (3) these deleterious effects can be minimized by a protective ventilatory strategy.

Methods: Human PMNs were incubated with bronchoalveolar lavage fluid obtained from patients at entry or 36 h after randomization to ventilation with either a conventional (control) or a lung-protective strategy. PMN oxidant production and surface expression of adhesion molecules and granule markers, including CD18, CD63, and L-selectin, were measured by flow cytometry. Extracellular elastase activity was quantified using a fluorescent substrate.

Results: Bronchoalveolar lavage obtained from both groups of patients at entry showed similar effects on PMN oxidant production and expression of surface markers. At 36 h, exposure of PMNs to bronchoalveolar lavage fluid from the control group resulted in increased PMN activation as manifested by a significant increase in oxidant production, CD18, and CD63 surface expression, and shedding of L-selectin. By contrast, these variables were unchanged at 36 h in the lung-protective group. There was a significant correlation between the changes of the variables and changes in interleukin-6 level and the number of failing organs.     

Superoxide production by neutrophils in a model of adult respiratory distress syndrome

Neutrophils (polymorphonuclear leukocytes [PMNs]) are thought to contribute to the pathophysiology of adult respiratory distress syndrome (ARDS) by the release of toxic oxygen metabolites. This study investigated superoxide production by circulating and bronchoalveolar lavage (BAL) PMNs in a rat model of ARDS induced by chronic Escherichia coli (lipopolysaccharide) endotoxemia. Superoxide production was stimulated by fmet-leu-phe, opsonized zymosan, and phorbol myristate acetate. Circulating and BAL PMNs from lipopolysaccharide-infused rats compared with PMNs from control rats are primed for nonselective increased superoxide production. The BAL PMNs are not only partially primed to release superoxide on adherence, they concomitantly have a depressed superoxide response to a phagocytic (opsonized zymosan) stimulus. These PMN responses may partially explain both the pulmonary injury and the increased susceptibility to pulmonary infection seen in patients with ARDS.     

Neutrophil function in a rat model of endotoxin-induced lung injury

Polymorphonuclear neutrophil leukocytes (PMNs) are known to cross the alveolar-capillary barrier and enter the alveolus in acute adult respiratory distress syndrome (ARDS). The pathogenic role of PMNs in both the acute lung injury and subsequent infectious susceptibility in ARDS is not clear. In the present study we investigated the functional status of various neutrophil populations using a chronic, endotoxemia-induced ARDS model. Rats infused with Escherichia coli endotoxin for three days develop an acute lung injury with a histologic picture closely resembling human ARDS. The PMNs recovered from the circulation and by bronchoalveolar lavage were compared with normal rat PMNs. In endotoxemic animals, superoxide production was markedly enhanced in circulating PMNs, indicating production of high levels of potentially cytotoxic oxygen intermediates, while myeloperoxidase activity was decreased in both circulating and lavage PMNs, indicating depressed myeloperoxidase-dependent antimicrobial activity.     

Granulocyte colony-stimulating factor and neutrophil-related changes in local host defense during recovery from shock and intra-abdominal sepsis.

BACKGROUND: We have reported that treatment with exogenous granulocyte colony-stimulating factor (G-CSF) improves abscess localization and reduces mortality without aggravating neutrophil (PMN)-mediated reperfusion injury in a model of septic abdominal trauma. The purpose of this study was to determine actions of G-CSF on PMN function in the peritoneum. METHODS: Anesthetized swine were pretreated with broad-spectrum antibiotics and underwent cecal ligation and incision and 35% hemorrhage (trauma). After 1 hour they were resuscitated with shed blood, crystalloid, and either G-CSF (n = 10) or saline solution vehicle (n = 9). The animals were observed for 72 hours. RESULTS: After trauma, saline solution treatment increased PMN infiltration into the peritoneum within 2 hours (P = .035), increased peritoneal PMN elastase production (i.e., cytotoxicity) by 24 hours (P = .004), and decreased adherence of peritoneal PMNs to an artificial substrate from 4 to 72 hrs (P = .043). The mean autopsy score was 7.0 +/- 0.5. With G-CSF treatment peritoneal neutrophilia was enhanced (maximum 48 hours, P = .002) and PMN cytotoxicity was augmented and delayed (maximum 48 hours, P = .004). Despite these changes, adherence of peritoneal PMNs was not significantly changed and there was no evidence for PMN-mediated damage in the lung as judged by bronchoalveolar lavage protein, bronchoalveolar lavage PMNs, lung tissue myeloperoxidase, or histologic changes. The mean autopsy score was improved to 4.1 +/- 0.3 (P < .001). CONCLUSIONS: G-CSF in resuscitation fluids improved localization of an intra-abdominal septic focus by increased production of circulating PMNs, increased PMN extravasation into the peritoneal cavity, and increased PMN cytotoxicity at the abdominal septic focus, without exaggerating PMN-dependent reperfusion injury in the lung. Therefore these data further support the idea that G-CSF in resuscitation fluids might reduce septic complications in the multiply injured trauma patient.     

Neutrophil Adhesion Molecule Expression Is Comparable in Perinatal Rabbits and Humans

Background: Human newborns, particularly those born before full term, are more susceptible to bacterial infections as a result of impaired host defense mechanisms. Compared with adults, circulating leukocytes from human newborns (preterm and full-term gestations) and newborn rabbits (full-term gestation) have low resting levels of CD62L (L-selectin) and do not significantly increase surface expression of CD18 after inflammatory stimulation. To determine the potential utility of preterm rabbits in investigations of perinatal human conditions, the authors compared the surface expression of the beta2 -integrin CD18 and CD62L (L-selectin) on polymorphonuclear leukocytes (PMNs) from perinatal rabbits and perinatal humans, both under resting conditions and after in vitro activation with inflammatory stimulants.

Methods: After erythrocyte lysis of whole-blood samples, leukocytes from 7-day-old, full-term (31-day gestation), and preterm (24-day gestation) rabbits, as well as full-term (37-42 week gestation) and preterm (27-36 week gestation) human newborns were prepared and stimulated in vitro at 37 degrees C with either C5a or phorbol myristate acetate. After fluorescence labeling of CD18 and CD62L with monoclonal antibodies, PMN adhesion molecule expression was assessed by flow cytometry.

Results: Constitutive CD18 expression was not significantly different between perinatal and adult humans but was reduced in all perinatal rabbits compared with adults. Inflammatory stimulation caused significant increases in CD18 expression in adult human PMNs but not in full-term and preterm newborns. Changes in CD18 expression in adult and preterm rabbits after stimulation, although in the same direction as humans, were more variable. In both species, constitutive CD62L expression on PMNs from all perinates was significantly lower than in adults. However, CD62L was shed to similar degrees after inflammatory stimulation in all groups.     

Changes of pulmonary intercellular adhesion molecule-1 and CD11b／CD18 in peripheral polymorphonuclear neutrophils and their significance at the early stage of burns

Objective: To investigate the role of intercellular adhesion molecule-1 (ICAM-1) in the accumulation of polymorphonuclear neutrophils (PMN) in the lungs at the early stage of burns. Methods: Myeloperoxidase content in lung tissues and bronchoalveolar lavage fluid (BALF) were detected.ICAM-1 and its mRNA expression in lung tissues were determined bycal method and in situ hybridization. CD11b/CD18 expression on the peripheral PMNs was measured by flowcytometry. Results : The levels of myeloperoxidase in lung tissues and BALF after burn injury were markedly higher than those of control. Expression of ICAM-1 and its mRNA in the lung tissues and CD11b/CD18 on peripheral PMNs surface was significantly increased at 2, 6, 12, 24 h after burns. Conclusions. PMNs accumulation in the lungs is related to increased ICAM-1 expression on pulmonary microvascular endothelial cells and CD11b/CD18 expression on PMN at the early stage of burn injury.     

Experimental study of dynamic changes in elastase-antiprotease in rabbits in the early stage of inhalation injury

In this experiment, rabbit model with smoke inhalation injury was used. The study was designed to observe the dynamic changes of elastase activities of polymorphonuclear leukocytes (PMN), alveolar macrophages (AM) and bronchoalveolar lavage fluid (BALF); and trypsin inhibitory capacities of serum and BALF (STIC & BTIC). The relationships between these changes and acute lung injury, as well as the concomitant changes of arterial blood gas levels, lung water volume and pathomorphology of trachea and lung tissues were also observed. It was found that after injury the elastase activities of PMN and AM were markedly reduced, and the elastase activity of BALF was rapidly increased. STIC was also reduced. PaO2 progressively dropped and PaCO2 progressively increased. Animals showed respiratory distress. Pathomorphological phagocytes aggregations in lungs, pulmonary edema and pneumorrhagia were found. There were serious destructions of capillary endothelial cells, alveolar epithelial cells, basement membranes and interstitial fibers. The number of elastic fibers of parenchyma decreased. The lung water volume was markedly increased, and there was a significant correlation between the increment of extravascular lung water and the rising of elastase activity of BALF. On the basis of our observation, it is proposed that the imbalance of elastase-antiprotease may play an important role in the development of acute lung injury after smoke inhalation.     

Dietary restriction impairs neutrophil exudation by reducing CD11b/CD18 expression and chemokine production

HYPOTHESIS: Patients with malnutrition are susceptible to infection. Polymorphonuclear neutrophils (PMNs) are the major effector of the nonspecific immune response in host resistance to infection. Dietary restriction may impair PMN-mediated immunity in the peritoneal cavity by reducing PMN exudation, adhesion molecule expression on PMNs, and chemokine production. DESIGN: Randomized study of murine glycogen-induced peritonitis with dietary restriction. SETTING: University research laboratory. MATERIALS: Male C57BL/6J mice. INTERVENTIONS: Mice (N = 204) were assigned to ad libitum, moderate, and severe diet-restricted groups receiving mouse chow ad libitum (132 g/kg, 66 g/kg, and 33 g/kg daily for 7 days, respectively). After dietary restriction with or without 1 day of refeeding, mice were administered glycogen intraperitoneally to induce cell exudation. MAIN OUTCOME MEASURES: CD11b, CD18, and CD62L expressions on circulating PMNs, phagocytosis, and reactive oxygen intermediate production by exudative PMNs were measured after glycogen installation. The levels of PMN-specific chemokine, macrophage inflammatory protein 2 (MIP-2), in peritoneal lavage fluid were also measured. These parameters were measured after glycogen installation in the refeeding experiment. RESULTS: Seven days of dietary restriction decreased CD11b/CD18 expression on circulating PMNs, MIP-2 levels in peritoneal lavage fluid, and subsequent PMN exudation into the peritoneal cavity early in peritonitis. Both CD11b and CD18 expression on circulating PMNs and MIP-2 levels correlated significantly with numbers of exudative PMNs. Seven days of dietary restriction also impaired phagocytosis, while up-regulating reactive oxygen intermediate production by exudative PMNs. Only 1 day of ad libitum refeeding normalized CD11b/CD18 expression with PMN exudation into the peritoneal cavity. CONCLUSIONS: Short-term dietary restriction impairs PMN exudation into local inflammatory sites in murine peritonitis by reducing CD11b/CD18 expression and MIP-2 production. Even brief nutritional replenishment in diet-restricted patients may improve host defense via restoring these PMN functions and chemokine production at local inflammatory sites.     

Neutrophil phagocytosis during endotoxin-induced lung injury

Depressed neutrophil (PMN) phagocytosis in patients with ARDS may contribute to the known increased incidence of pulmonary sepsis. To evaluate changes in phagocytosis, circulating PMNs from normal rats were compared to circulating and alveolar PMNs (obtained by bronchoalveolar lavage, BAL) from rats after 72 hr of endotoxin infusion (LPS-Rx)-induced acute lung injury. Since phagocytosis correlates with adherence, PMN adherence to coverslips and to a standard nylon wool column was also measured. PMN adherence to nylon wool was 65% for control, 77% for circulating LPS-Rx, and 20% for BAL PMNs. As a measure of phagocytosis the PMNs were incubated for 30 min with opsonized fluorescent (FITC) tagged yeast. Total PMN with yeast were 95.4 +/- 2.1% for control; 96.4 +/- 1.8% for circulating LPS-Rx; and 78.7 +/- 7.8% (P less than 0.05 compared to control) for BAL PMNs. Total numbers of yeast particles per 100 PMN are 270 +/- 64 for control, 300 +/- 42 for circulating LPS-Rx, and 170 +/- 45 (P less than 0.05 compared to control) for BAL PMN. Conclusions: (1) Intraalveolar (BAL) PMNs have decreased adherence; (2) nonadherent PMNs have decreased uptake of yeast; (3) BAL PMNs, overall, have a significantly decreased uptake of yeast; (4) this depression in BAL PMN phagocytosis may partially explain the known decreased rate of bacterial clearance in injured lungs and the increased risk of pulmonary sepsis with adult respiratory distress syndrome.     

Neutrophil CD18 expression and blockade after traumatic shock and endotoxin challenge.

OBJECTIVE: The expression of the leukocyte CD18 adhesion complex on polymorphonuclear leukocytes (PMNs) was measured, and the physiologic effects of blockade of the complex were studied after trauma and sepsis. SUMMARY BACKGROUND DATA: Margination of PMNs occurs early during inflammation and depends, in part, on expression of the CD18 adhesion complex. Blockade of this adherence complex can reduce PMN-mediated damage. This study tests the hypothesis that PMN activation after resuscitated trauma produces an occult endothelial injury that increases the vulnerability to a delayed inflammatory stimulus. METHODS: Anesthetized (fentanyl) mongrel pigs were sham injured or fluid resuscitated from soft tissue injury +35% hemorrhage. Systemic blood was collected at 24-hour intervals from awake animals. The CD18 density on circulating PMNs was determined with flow cytometry using mean channel fluorescence (MCF). The CD18 receptors were blocked with monoclonal antibodies either immediately before trauma or immediately before an endotoxin (lipopolysaccharide [LPS]) challenge that was administered to all groups 3 days after the shock episode. Bronchoscopy was performed before trauma, pre-LPS, and post-LPS, and protein content was measured in bronchoalveolar lavage (BAL). RESULTS: Mean channel fluorescence was reduced on PMNs for 48 hours in animals with trauma versus animals with sham injuries. Anti-CD18 therapy produced higher circulating PMN counts compared with nontreated sham or shock groups. The incremental rise of BAL protein after shock was prevented with anti-CD18; the increment after LPS was attenuated. Anti-CD18 was administered before trauma and reduced the fluids necessary to maintain cardiac filling pressures after LPS. CONCLUSIONS: These data suggest that PMNs are activated after resuscitation from traumatic shock and that these cells produce an endothelial injury that may increase the vulnerability to a septic challenge. The broad implication is that temporarily blocking PMN adhesiveness at the time of trauma might salvage some host tissue and reduce the incidence of septic complications in the post-trauma period.     

25% Albumin modulates adhesive interactions between neutrophils and the endothelium following shock/resuscitation

BACKGROUND: Polymorphonuclear neutrophil (PMN) sequestration in the lung is a hallmark of acute respiratory distress syndrome (ARDS). We have shown that 25% Albumin (A25) resuscitation attenuates lung injury after hemorrhagic shock and lipopolysaccharide (LPS) exposure by reducing lung leukosequestration. We hypothesize that this protective property is mediated by alteration of neutrophil-endothelial cell adhesive interactions. MATERIALS AND METHODS: A 2-hit rodent model of shock resuscitation was used. CD11b and L-selectin were measured using flow cytometry in rat and human neutrophils ex vivo. Intercellular adhesion molecule-1 (ICAM-1) levels were measured by Northern blot and immunohistochemistry. RESULTS: Resuscitation with A25 attenuated the increase in PMN CD11b expression in Ringer's lactate (RL) resuscitated animals at end resuscitation and at 4-hour post-LPS. While PMN L-selectin levels remained stable in RL treated animals, A25 resuscitation resulted in a significant decrease in surface L-selectin expression at 4-hour post-LPS. ICAM-1 lung endothelial cell mRNA, was increased in RL resuscitated animals, however reduced with A25 use by 51%. The LPS induced ICAM-1 endothelial cell protein expression was also prevented with A25 resuscitation. Antioxidant property of albumin was shown to play a critical role in altering CD11b expression. CONCLUSIONS: The A25 exerts its lung-protective activity at various levels including altering the interaction between neutrophils and endothelial cells via suppressed expression of adhesion molecules. These findings suggest a novel role for A25 as an anti-inflammatory agent in PMN-mediated diseases such as ARDS.     

Decreased leukocyte adhesion with anti-CD18 monoclonal antibodies is mediated by receptor internalization.

BACKGROUND. Adhesion of polymorphonuclear leukocytes (PMNs) to endothelial cells is mediated partially by CD11/CD18 integrins. The purpose of this study was to define (1) the response of PMNs to anti-CD18 monoclonal antibody binding, and (2) the mechanism responsible for anti-CD18 monoclonal antibody-mediated decreases in PMN adhesion to endothelial cells. METHODS. Canine PMN O2- production, myeloperoxidase, and lysozyme release in response to the anti-CD18 monoclonal antibody IB4 were measured by standard assays. To examine endocytosis of CD18 receptors, PMNs incubated with IB4 and a fluorescein isothiocyanate secondary antibody were analyzed by flow cytometry. RESULTS. Treatment of PMNs with IB4 did not stimulate O2- production or degranulation but decreased adhesion of 51Cr-labeled PMNs to ex vivo canine aorta. Incubation of PMNs at 25 degrees C resulted in a decrease in fluorescence intensity that was not affected by NaN3 or vanadate but was blocked by NaF, 4 degrees C, and bafilomycin, which prevents endosomal acidification. Treatment with an antifluorescein antibody decreased the fluorescence intensity in NaF and 4 degrees C, but not in bafilomycin-treated neutrophils. CONCLUSIONS. IB4 decreases PMN-endothelial cell adhesion but does not stimulate neutrophil oxidative metabolism or degranulation. These data suggest that reduced adhesion may be the result of internalization of the CD18/IB4 complex. Anti-CD18 monoclonal antibodies may be useful in preventing PMN adhesion without the potentially deleterious effects of cell activation.     

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.     

Effects of spermidine and p-cresol on polymorphonuclear cell apoptosis and function

Polymorphonuclear leukocytes (PMNs) from chronic kidney disease (CKD) patients display accelerated apoptosis and dysfunction, which may predispose CKD patients to infections. In this study, we investigated the effect of spermidine and p-cresol on apoptosis and function on PMN from healthy subjects. We measured the effect of spermidine and p-cresol on apoptosis, ROS production unstimulated and stimulated (S. aureus and PMA) and expression of CD95, caspase 3, and CD11b on PMN. After incubation with p-cresol and spermidine, we did not observe any changes in apoptosis, viability or expression of caspase 3 and CD95 in PMN from healthy subjects. PMN incubated for 10 minutes with spermidine demonstrated a significant reduction in spontaneous, S. aureus and PMA-stimulated ROS production. p-cresol induced a decrease in PMA-stimulated ROS production. Spermidine and p-cresol also induced a decrease in the expression of CD11b on PMN. Spermidine and p-cresol decreased the expression of CD11b and oxidative burst of PMN from healthy subjects and had no effect on PMN apoptosis and viability.     

EPA + DHA supplementation reduces PMN activation in microenvironment of chronic venous leg ulcers: A randomized,double‐blind,controlled study

Sustained high levels of activated polymorphonuclear leukocytes (PMNs) and PMN‐derived proteases in the microenvironment of chronic venous leg ulcers (CVLUs) are linked to chronic inflammation and delayed healing. Uncontrolled PMN activity eventually destroys newly developed tissue and degrades critical growth factors. The bioactive components of fish oil (n‐3 eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) have strong inflammation‐resolving actions and have been shown to assuage PMN activity, but have not been tested in CVLU patients. This randomized controlled study compared the effectiveness of oral EPA + DHA therapy to a placebo for reducing PMN activation in CVLU microenvironments. At Days 0, 28, and 56, markers of PMNs (CD15) and activated PMNs (CD66b), and levels of PMN‐derived proteases human neutrophil elastase and matrix metalloproteinase‐8 were measured in CVLU fluid from patients receiving standard compression therapy and (1) EPA + DHA therapy (n = 16) or (2) placebo (n = 19). By Day 56, the EPA + DHA Group had a significantly lower percentage of CD66b+ cells in CVLU fluid compared to Day 0 (p = 0.02) and to Day 28 (p = 0.05). Importantly, there were downward trends in levels of both matrix metalloproteinase‐8 and human neutrophil elastase over time in the EPA + DHA Group, which also demonstrated greater reductions in wound area by Day 28 (57% reduction) and Day 56 (76% reduction) than the Control Group (35% and 59%, respectively). Moreover, reductions in wound area had significant negative relationships with CD15+ cells in wound fluid at Days 28 (p = 0.008) and 56 (p < 0.001), and CD66b+ cells at Days 28 (p = 0.04) and 56 (p = 0.009). The collective findings provide supplemental evidence that high levels of activated PMNs in CVLU microenvironments inhibit healing, and suggest that EPA + DHA oral therapy may modulate PMN activity and facilitate healing of CVLUs when added to standard care regimens.     

Role of L-selectin in the development of ventilator-associated pneumonia in patients after major surgery

BACKGROUND: The circulating level of soluble L-selectin (sL-selectin) has been reported to be low in adult respiratory distress syndrome and acute lung injury. This study explores the role of L-selectin in the development of ventilator-associated pneumonia (VAP) in patients undergoing major surgery. PATIENTS AND METHODS: Thirty-four patients who underwent esophagectomy were maintained by mechanical ventilation in a surgical intensive care unit. Fourteen patients developed VAP by postoperative day (POD) 7, while 20 patients did not. The plasma levels of soluble adhesion molecules and elastase were measured serially by ELISA or EIA. The expression of L-selectin on polymorphonuclear neutrophils (PMNs) was analyzed by flow cytometry. RESULTS: In multiple logistic regression analysis, only the preoperative plasma level of sL-selectin was significantly associated with VAP. The plasma sL-selectin level before surgery was significantly lower in the patients who developed VAP compared with the patients who did not develop VAP. After surgery, the level of sL-selectin did not change. The plasma level of soluble intercellular adhesion molecule-1 increased in the patients with and without VAP. The plasma level of soluble vascular cell adhesion molecule-1 was significantly higher in the patients with VAP. L-selectin expression on PMNs showed a peak on POD 2 in the patients without VAP, whereas it was impaired in the patients with VAP. CONCLUSIONS: Determination of the preoperative plasma level of sL-selectin may help to identify patients at high risk for VAP after esophagectomy.     

Effects of lung preservation solutions on PMN activation in vitro

Polymorphonuclear leukocyte (PMN) activation and PMN-endothelial cell interactions may cause graft failure due to ischemia-reperfusion injury after lung transplantation. We investigated the effects of Euro-Collins solution (EC), low-potassium dextran solution (LPD), and EC plus pentoxifylline (EC-PTXF) on adhesion molecule (CD11b/CD18 and L-selectin) expression, chemotaxis, and oxidative burst of PMN. PMN from healthy human volunteers were incubated with EC, LPD, and EC-PTXF, and, in controls, without preservation solution. LPD exerted a suppressive effect on PMN chemotaxis as compared to EC (P < 0.05), but had no attenuating effect on the increase of CD11b/CD18, the shedding of L-selectin, and intracellular oxidant generation. EC-PTXF attenuated the expression of CD11b/CD18 and the oxidative burst as compared to EC alone (P < 0.05). These effects of LPD and PTXF on PMN function may contribute to successful organ preservation in transplantation. Received 22 June 98 Received after revision: 30 December 1998 Accepted: 19 January 99     

Cardiopulmonary bypass renders patients at risk for multiple organ failure via early neutrophil priming and late neutrophil disability.

BACKGROUND: Cardiopulmonary bypass (CPB) is associated with a systemic inflammatory response syndrome (SIRS) and these patients are recognized to be at increased risk for delayed infectious complications. We have documented that circulating neutrophils (PMNs) from patients manifesting SIRS have evidence of early postinjury priming for cytotoxicity. Consequently, we hypothesized that CPB would result in early postoperative PMN hyperresponsiveness (priming). MATERIALS AND METHODS: Six patients (mean age 50 +/- 2.9 years) who underwent CPB for CABG had sequential blood samples obtained perioperatively. PMNs were isolated and superoxide anion (O(-)(2)) generation (nmol O(-)(2)/3.75 x 10(5) PMNs/min) was measured by reduction of cytochrome c after exposure to fMLP, C5a, or PMA; elastase release (% total PMN elastase content) was measured by cleavage of AAPV-pNA after exposure to fMLP or C5a. RESULTS: PMNs were activated for increased elastase release 6 h after initiation of CPB. Significant PMN priming for O(-)(2) production was discovered at 3, 6, and 12 h following CPB and for elastase release at 3 and 6 h after CPB. At 2 to 3 days after CPB, O(-)(2) generation was significantly less than that of the preoperative control. Neutrophil primability with PAF was detected at 6 h after CPB. A similar defect in PAF-primable O(-)(2) production was seen 2 and 3 days post-CPB. Direct PMN interrogation with the receptor-independent activator PMA revealed loss of integrity of the NADPH oxidase at 2 and 3 days following CPB. CONCLUSIONS: A vulnerable window exists between 3 and 12 h after CPB when PMNs are primed for enhanced cytotoxicity via O(-)(2) production and elastase release. Paradoxically, PMN oxidase integrity becomes deficient 48 h post-CPB, while protease degranulation remains intact. These events render the bypass patient at risk for multiple organ failure via both early PMN-mediated tissue injury and delayed infectious complications.     

Mechanical Ventilation with Lower Tidal Volumes and Positive End-expiratory Pressure Prevents Pulmonary Inflammation in Patients without Preexisting Lung Injury

Background: Mechanical ventilation with high tidal volumes aggravates lung injury in patients with acute lung injury or acute respiratory distress syndrome. The authors sought to determine the effects of short-term mechanical ventilation on local inflammatory responses in patients without preexisting lung injury.

Methods: Patients scheduled to undergo an elective surgical procedure (lasting >=5 h) were randomly assigned to mechanical ventilation with either higher tidal volumes of 12 ml/kg ideal body weight and no positive end-expiratory pressure (PEEP) or lower tidal volumes of 6 ml/kg and 10 cm H2O PEEP. After induction of anesthesia and 5 h thereafter, bronchoalveolar lavage fluid and/or blood was investigated for polymorphonuclear cell influx, changes in levels of inflammatory markers, and nucleosomes.

Results: Mechanical ventilation with lower tidal volumes and PEEP (n = 21) attenuated the increase of pulmonary levels of interleukin (IL)-8, myeloperoxidase, and elastase as seen with higher tidal volumes and no PEEP (n = 19). Only for myeloperoxidase, a difference was found between the two ventilation strategies after 5 h of mechanical ventilation (P < 0.01). Levels of tumor necrosis factor [alpha], IL-1[alpha], IL-1[beta], IL-6, macrophage inflammatory protein 1[alpha], and macrophage inflammatory protein 1[beta] in the bronchoalveolar lavage fluid were not affected by mechanical ventilation. Plasma levels of IL-6 and IL-8 increased with mechanical ventilation, but there were no differences between the two ventilation groups.     

Inflammation and the acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a clinical syndrome of non-cardiogenic pulmonary oedema associated with bilateral pulmonary infiltrates, stiff lungs and refractory hypoxaemia. ARDS is characterized by an explosive acute inflammatory response in the lung parenchyma, leading to alveolar oedema, decreased lung compliance and, ultimately, hypoxaemia. Although our understanding of the causes and pathophysiology of ARDS has increased, the mortality rate remains in the range of 30-50%. No major advances in pharmacological therapy have been achieved. Mechanical ventilation is the main therapeutic intervention in the management of ARDS. The only approach that has been shown to reduce the inflammatory response and mortality is the use of lung-protective ventilatory strategy with a low tidal volume and high positive-end expiratory pressure. This chapter will review the current state of the literature on the pathogenesis of ARDS and ventilatory and pharmacotherapy approaches to its management.