Georgios Nakos

Bronchoalveolar lavage fluid characteristics of early intermediate and late phases of ARDS. Alterations in leukocytes, proteins, PAF and surfactant components.

AbstractObjective To determine the concentration of proteins and phospholipids, markers of inflammatory reaction such as platelet-activating factor (PAF), and cell alterations in bronchoalveolar lavage (BAL) fluid during the evolution of the acute respiratory distress syndrome (ARDS). Design Prospective controlled study. Setting 14-bed medical-surgical intensive care unit in a 750-bed university teaching hospital. Patients 19 mechanically ventilated patients, 9 patients with ARDS and 10 patients without cardiopulmonary disease (controls), were eligible for this study. Interventions BAL was performed during the early, intermediate, and late phases of ARDS. Measurements and results Total phospholipids and individual phospholipid classes of the surfactant, proteins, PAF, and cells were measured. High levels of PAF, an increase in neutrophils and proteins, and quantitative as well as qualitative alterations in phospholipids in BAL fluid were observed in ARDS patients compared to the control group. PAF, proteins, and neutrophils were higher in early ARDS than in intermediate or late ARDS. The surfactant pool increased in the early phase and decreased in the intermediate or late phase of the syndrome. The qualitative alterations of surfactant consist of reduced phospholipid content in the surfactant structures with good surface properties; moreover, there was a considerable decrease in the percentage of phosphatidylcholine and phosphatidylglycerol, followed by an increase in phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and sphingomyelin in all three phases of ARDS compared to the control group. Lysophosphatidylcholine was detectable only in late ARDS. Conclusion Total surfactant phospholipids, surfactant components, and inflammatory markers such as PAF, cells, and proteins were affected in patients with ARDS. These factors, undergoing quantitative alterations during the course of ARDS, could have a significant role in the pathogenesis and evolution of ARDS.

The role of apoptosis in the pathophysiology of Acute Respiratory Distress Syndrome (ARDS): an up-to-date cell-specific review.

ARDS pathophysiology is characterized by complex mechanisms that involve cells of inflammation, lung tissue cells, cytokines, chemokines, as well as apoptosis activators and inhibitors. There are two important theories that link apoptosis with ARDS and suggest that epithelial cell apoptosis, as well as the accumulation of neutrophils in the lung, may contribute to a cascade of events and, finally, ARDS. The activation of the Fas/FasL pathway is an important mechanism of alveolar epithelial injury in the lungs of patients with ALI. In addition, neutrophilic inflammation in the alveolar spaces is characteristic of ALI in humans and in most animal models of ALI. The enhanced phagocytosis of apoptotic neutrophils could lead to resolution of inflammation and repair during ARDS. In this review, we will focus on elucidating the role of apoptosis in the pathophysiology of ARDS and the contribution of Fas-mediated inflammation in ARDS. Furthermore, we will give evidence that TNF-alpha, IL-1beta and IL-13 attenuate the pro-cell death effects of Fas/CD95 on A549 epithelial cells, at least partially, by the NF-kB and PI3-K pathways, suggesting that induction of the expression of antiapoptotic genes protects the epithelial cells from cell death.

Tracheal gas insufflation reduces the tidal volume while PaCO2 is maintained constant

ObjectiveThe aims of the present study were two-fold: first, to confirm the effect of tracheal gas insufflation (TGI) throughout the respiratory cycle on alveolar ventilation at various catheter flows and constant total inspired VT as an adjunct to conventional volume cycled mechanical ventilation in patients with acute lung injury; second, to test the efficacy of TGI in the reduction of toal VT, peak and mean airway pressure while maintaining PaCO2 in its baseline value. The hemodynamic effect and the consequences on oxygenation as result of the reduction of VT, were also estimated.DesignProspective study of patients with acute lung injury requiring mechanical ventilation.Setting: 12 bedded, adult polyvalent intensive care unit in a teaching hospital.Patients7 paralyzed and sedated patients with acute respiratory failure were studied. All patients were clinically and hemodynamically stable without fluctuation of the body temperature. All patients were orally intubated with cuffed endotracheal tubes, and mechanically ventilated with a standard circuit of known compliance.InterventionsContinuous flows (4 and 6 l/min) were delivered through a catheter positioned 1 cm above carina while tidal volume or PaCO2 were maintained constant at their baseline value.ResultsIn this study a modest level of TGI significantly enhanced CO2 elimination in patients with acute respiratory failure. Improved ventilatory efficiency resulted from the functional reduction of dead space during TGI allowing the same PaCO2 to be maintained at the same frequency with lower tidal volume and lower airway pressure requirement. Tidal volume, peak and mean airway pressure decreased linearly with catheter flow, without significant changes in oxygenation, while PaCO2 remained stable.ConclusionThe results of this study suggest that TGI may be an useful adjunct mode of mechanical ventilation that limits alveolar pressure and minute ventilation requirements.

Bronchoalveolar lavage alterations during prolonged ventilation of patients without acute lung injury

Mechanical ventilation deteriorates previously injured lung, but little is known about its effect on healthy human lung. This work was designed to assess the effect of prolonged mechanical ventilation on bronchoalveolar lavage (BAL) fluid composition of patients without acute lung injury. Twenty-two ventilated patients (tidal volume 8–10 mL·kg−1, positive end-expiratory pressure 3–5 cmH2O) without lung injury, who did not develop any complication from the respiratory system during the 2‐week study period, were studied. They were subjected to three consecutive BALs, the first during 36 h from intubation, the second at the end of the first week of mechanical ventilation and the third at the end of the second week of mechanical ventilation. Total BAL protein increased during mechanical ventilation (148±62, 381±288, 353±215 µg·mL−1 BAL for the first, second and third BAL, respectively). In contrast, BAL phospholipids decreased (2.7±1.1, 1.4±0.6, 1.2±0.7 µg·mL−1 BAL, respectively). Large surfactant aggregates were reduced and inflammatory markers, such as platelet activating factor (PAF), PAF-acetylhydrolase and neutrophils, significantly increased after 1 week, but partially remitted after 2 weeks of mechanical ventilation. In summary, this study demonstrates that prolonged mechanical ventilation even of patients without acute lung injury is associated with the presence of inflammatory markers and surfactant alterations.

Desferrioxamine attenuates minor lung injury following surgical acute liver failure

Acute liver failure (ALF) can be complicated by lung dysfunction. The aim of this study was to test the hypothesis that inhibition of oxidative stress through iron chelation with desferrioxamine (DFX) attenuates pulmonary injury caused by ALF. 14 adult female domestic pigs were subjected to surgical devascularisation of the liver and were randomised to a study group (DFX group, n = 7), which received post-operative intravenous infusion of DFX (14.5 mg·kg−1·h−1 for the first 6 h post-operatively and 2.4 mg·kg−1·h−1 until completion of 24 h), and a control group (n = 7). Post-operative lung damage was evaluated by histological and bronchoalveolar lavage fluid (BALF) analysis. DFX resulted in reduced BALF protein levels and tissue phospholipase (PL)A2 activity. Plasma malondialdehyde and BALF nitrate and nitrite concentrations were lower, while catalase activity in the lung was higher after DFX treatment. PLA2, platelet-activating factor acetylhydrolase and total cell counts in BALF did not differ between groups. Histological examination revealed reduced alveolar collapse, pneumonocyte necrosis and total lung injury in the DFX-treated animals. DFX reduced systemic and pulmonary oxidative stress during ALF. The limited activity of PLA2 and the attenuation of pneumonocyte necrosis could represent beneficial mechanisms by which DFX improves alveolar–capillary membrane permeability and prevents alveolar space collapse.

Inhaled activated protein C protects mice from ventilator-induced lung injury

IntroductionActivated Protein C (APC), an endogenous anticoagulant, improves tissue microperfusion and endothelial cell survival in systemic inflammatory states such as sepsis, but intravenous administration may cause severe bleeding. We have thus addressed the role of APC delivered locally by inhalation in preventing acute lung injury from alveolar overdistention and the subsequent ventilator-induced lung injury (VILI). We also assessed the effects of APC on the activation status of Extracellular- Regulated Kinase 1/2 (ERK) pathway, which has been shown to be involved in regulating pulmonary responses to mechanical stretch.MethodsInhaled APC (12.5 μg drotrecogin-α × 4 doses) or saline was given to tracheotomized C57/Bl6 mice starting 20 min prior to initiation of injurious mechanical ventilation with tidal volume 25 mL/Kg for 4 hours and then hourly thereafter; control groups receiving inhaled saline were ventilated with 8 mL/Kg for 30 min or 4 hr. We measured lung function (respiratory system elastance H), arterial blood gases, surrogates of vascular leak (broncho-alveolar lavage (BAL) total protein and angiotensin-converting enzyme (ACE)-activity), and parameters of inflammation (BAL neutrophils and lung tissue myeloperoxidase (MPO) activity). Morphological alterations induced by mechanical ventilation were examined in hematoxylin-eosin lung tissue sections. The activation status of ERK was probed in lung tissue homogenates by immunoblotting and in paraffin sections by immunohistochemistry. The effect of APC on ERK signaling downstream of the thrombin receptor was tested on A549 human lung epithelial cells by immunoblotting. Statistical analyses were performed using ANOVA with appropriate post-hoc testing.ResultsIn mice subjected to VILI without APC, we observed hypoxemia, increased respiratory system elastance and inflammation, assessed by BAL neutrophil counts and tissue MPO activity. BAL total protein levels and ACE activity were also elevated by VILI, indicating compromise of the alveolo-capillary barrier. In addition to preserving lung function, inhaled APC prevented endothelial barrier disruption and attenuated hypoxemia and the inflammatory response. Mechanistically, we found a strong activation of ERK in lung tissues by VILI, which was prevented by APC, suggestive of pathogenetic involvement of the Mitogen-Activated Kinase pathway. In cultured human lung epithelial cells challenged by thrombin, APC abrogated the activation of ERK and its downstream effector, cytosolic Phospholipase A2.ConclusionsTopical application of APC by inhalation may effectively reduce lung injury induced by mechanical ventilation in mice.

Influence of propofol and volatile anaesthetics on the inflammatory response in the ventilated lung

Background: The immunomodulatory effects of volatile anaesthetics in vitro and the protective effect of propofol in lung injury spurred us to study the effects of volatile anaesthetics and propofol on lung tissue in vivo.

Treatment of Toxic Epidermal Necrolysis with the Combination of Infliximab and High-Dose Intravenous Immunoglobulin

Background: Therapeutic evidence for toxic epidermal necrolysis (TEN) is indicative for high-dose intravenous immunoglobulin yet inconclusive for corticosteroids. Objective: To describe the combination of corticosteroids, infliximab and a high-dose intravenous immunoglobulin course for TEN. Patients and Methods: In three patients (SCORTEN survival probabilities: 41.7%, 64.2%, 41.7%) disease control was evaluated by (a) employing quantitative image analysis to measure progression of skin detachment and (b) patients’ outcome (complete re-epithelization). Published cases of TEN treatments with infliximab were retrieved from PubMed. Results: Within 48 h skin disease progression was arrested in all patients. Two patients were discharged after 3 weeks without any sequels from skin or conjunctivae. One patient passed away on the ninth day, however with noticeably improved skin (mortality rate: 33% observed vs. 50% expected). A PubMed search retrieved five TEN patients treated successfully with infliximab. Conclusion: The described combination presents a feasible therapeutic alternative for TEN that warrants further evaluation.

HPLC-fluorimetric assay of phospholipase A2. Application to biological samples with high protein content and various reaction conditions

Phospholipase A(2) (PLA(2)) quantitation in real-time, using (7-nitro-2-1,3-benzoxadiazol-4-yl)amino-derivatives of phosphatidylcholine (NBD-PCs) as substrates, is influenced by high protein content, color or turbidity. The purpose of the study was to overcome such limitations by a complementary reversed-phase HPLC step to separate the substrates from the products of the reaction. Plasma and bronchoalveolar lavage (BAL) fluid were applied as enzymic sources, while standard porcine PLA(2) and human plasma PAF-acetylhydrolase (PAF-AH) were employed as positive controls. The method was validated with a radiometric assay and compared with the real-time fluorimetric assay. Regarding PLA(2) and PAF-AH determination, the isocratic elution systems CH(3)OH-H(2)O (80:20, v/v) and CH(3)OH-H(2)O-CH(3)COOH (60:40:0.2, v/v/v) separated efficiently C(12)-NBD-FA/C(12)-NBD-PC and C(6)-NBD-FA/C(6)-NBD-PC, with 4.4 and 2.2 resolution, respectively. Analysis time was ∼15 min/injection. The reproducibility, expressed as relative standard deviation, was ≤13% for PLA(2) and ≤16% for PAF-AH, respectively. The assay was linear for PLA(2) activities extending from 1 pmol up to at least 250 nmol FA/h/mL sample, similar to the radiometric assay. It was appropriate for samples with high protein content, where the real-time fluorimetric assay was insufficient. The HPLC method was also evaluated under elevated temperatures, various pH values and Ca(2+) concentrations.

Serum procalcitonin as a diagnostic tool of bacteremia

Procalcitonin (PCT) is a highly specific marker of severe bacterial infections and organ failure due to sepsis. The aim of the present study was to determine the diagnostic value of serum PCT in ICU patients with bacteremia caused by either Gram-negative or Gram-positive bacteria.