0
Original Research: CHEST INFECTIONS |

Experimental Severe Pseudomonas aeruginosa Pneumonia and Antibiotic Therapy in Piglets Receiving Mechanical Ventilation* FREE TO VIEW

Carlos M. Luna, MD, FCCP; Sebastián Baquero, MD; Sebastián Gando, MD; Juan Risso Patrón, MD; Joaquín García Morato, MD; Oriol Sibila, MD; Rubén Absi, PhD; Angela Famiglietti, PhD; Carlos A. Vay, PhD; Florencia Von Stecher, MD; Carlos Agustí, MD; Antoni Torres, MD, FCCP
Author and Funding Information

*From the División Neumonología (Drs. Luna, Baquero, and Gando), Centro Universitario de Cirugía Experimental (Drs. Patrón and Morato), Departamento de Bioquímica Clínica, Facultad de Farmacia y Bioquímica (Drs. Absi, Famiglietti, and Vay), and División Patología, Facultad de Medicina (Drs. Von Stecher, Agustí, and Torres), Hospital de Clínicas, Universidad de Buenos Aires, Buenos Aires, Argentina; and Hospital Clínic de Barcelona (Dr. Sibila), Institut del Tòrax, Servicio de Neumología, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain.

Correspondence to: Carlos M. Luna, MD, FCCP, Acevedo 1070, Banfield (1828), Buenos Aires, Argentina; e-mail: cymluna@advancedsl.com.ar



Chest. 2007;132(2):523-531. doi:10.1378/chest.07-0185
Text Size: A A A
Published online

Background: Little is known about the general and local consequences of severe pneumonia under mechanical ventilation (SPMV) and how these are resolved with antibiotic therapy (ABT).

Objectives: To investigate the physiologic, biological, microbiological, and pathologic changes produced by experimental SPMV in a porcine model, and to evaluate the effect of ABT.

Methods: Pseudomonas aeruginosa was inoculated in 12 large white-Landrace piglets receiving mechanical that were killed after 72 h if death did not occur before. Vital signs, serum and BAL cytokines, serum C-reactive protein (CRP), and graded postmortem lung pathology and cultures (blood and quantitative BAL and lung) were evaluated. Six piglets received inappropriate ABT (no ABT or ceftriaxone), and six piglets received appropriate ABT (ciprofloxacin).

Measurements and main results: Pathologic and microbiological evidence of infection were present in all the animals in both groups. SPMV produced significant oxygenation and lung compliance worsening, increased serum CRP, and reduced BAL fluid tumor necrosis factor (TNF)-α. Arterial thrombosis in lung pathology was associated with higher temperature, hypoxemia and low lung compliance, higher initial serum CRP and TNF-α concentrations, and increased serum interleukin (IL)-6 and BAL IL-6 and TNF-α. Reduced ABT reduced body temperature and culture positivity.

Conclusions: This model resembles VAP and has been used for studying pulmonary infection and inflammation related to mechanical ventilation. ABT reduced fever and bacterial burden in SPMV but had no effect on cytokine or CRP concentrations, oxygenation, or lung mechanics. Pulmonary artery thrombosis was associated with worse response to infection.

Figures in this Article

Ventilator-associated pneumonia (VAP) is a severe pneumonia that appears in patients receiving mechanical ventilation (severe pneumonia under mechanical ventilation [SPMV]) leading to complications in critically ill patients, prolonging their length of hospital stay and increasing the risk of death.1The pathophysiology of SPMV includes inflammation, necrosis, alveolar edema, and emphysema-like lesions produced by the infection, but is also induced by positive pressure mechanical ventilation.2Pseudomonas aeruginosa is the most common pathogen of VAP in humans and is associated with a high mortality rate.34 Little is known about the general and local consequences of VAP and how these are resolved under appropriate antibiotic therapy (ABT). Furthermore, these consequences are difficult to address in the clinical setting due to the complexity of this disease.5 Therefore, an animal model of SPMV resembling severe VAP may allow better understanding of this severe disease. We hypothesized that this previously used porcine model2,67 may be useful to study physiologic, clinical, and biological response after bacterial challenge under mechanical ventilation, and to determine the effect of ABT on this response to thereby improve the understanding of this disease and improve the management of patients with VAP.

An experimental ICU with cardiovascular monitors (model 78353-A; Hewlett-Packard; Andover, MA), ventilators (Monal D; Air Liquide Santé; Paris, France), and electrical infusors (Abbott Infusor Pump; Abbott; Abbott Park, IL) was set up in our institution. A team provided 24-h care of the animals studied during the 3-day study period.

Animal Model Preparation

Twelve, healthy, 3-month-old, large white-Landrace piglets weighing 20 ± 2 kg were anesthesized and orotracheally intubated with a 7.0-mm low pressure cuff tube (Portex; Hythe; Kent, UK). The animals were preanesthetized with IM ketamine (250 mg) and anesthetized with a continuous infusion of midazolam (0.3 mg/kg/h), pancuronium bromide (4 mg; 0.50 mg/kg/h), and fentanyl (0.07 mg; 5 μg/kg/h). A femoral venous catheter was placed for continuous infusion of 10% dextrose (1.5 mL/kg/h) and Ringer lactate (3 mL/kg/h). A 3F catheter (Plastimed; St Leu La Forêt, France) was placed in a femoral artery for pressure monitoring and blood sampling. An 8F suprapubic bladder catheter (Vesicoset; Angiomed; Karlsruhe, Germany) was introduced by surgical minipelvitomy. The piglets were then ventilated in a prone position in volume-controlled mode with a constant tidal volume (Vt) of 15 mL/kg. This Vt could induce per se lung injury; however, it was identical to the original description by Marquette et al5 for this model. Initial ventilatory settings included respiratory rate (15 breaths/min), inspiratory/expiratory ratio (33%), fraction of inspired oxygen (Fio2) [21%], and positive end-expiratory pressure (0 cm H2O). Fio2 was set according to blood gas analysis to obtain Pao2 ≥ 80 to < 100 mm Hg.

Measurements During Mechanical Ventilation

Hemodynamic parameters, airway pressure, respiratory compliance, and blood gas levels were determined every 6 h. Paco2 was maintained between 35 mm Hg and 45 mm Hg by increasing the respiratory rate but avoiding the development of auto-positive end-expiratory pressure. Above this limit, hypercapnia was tolerated.

Bronchial Inoculation

Eighty milliliters of a 106 cfu/mL suspension of Pseudomonas aeruginosa American Type Culture Collection 27853 susceptible to ciprofloxacin (minimal inhibitory concentration, 0.5 μg/mL) and not susceptible to ceftriaxone (minimal inhibitory concentration, 32 μg/mL) were inoculated and evenly distributed among every lobe of both lungs using a fiberbronchoscope.

Follow-up

Ventilator parameters, heart rate, BP, rectal temperature, blood gas levels, and serum electrolytes were measured at 0, 2, 6, 12, 24, 36, 48, 60, and 72 h.

Blood Analysis:

Hematology and biochemical parameters, lactate, C-reactive protein (CRP), and cytokines were determined at 0, 24, 48, and 72 h.

Bacteriology:

BAL fluid, lung tissue, and blood cultures were performed either before or immediately after death.

BAL Fluid Cytokines:

BAL fluid cytokines were measured after intubation and at the end of the study.

Sacrifice and Spontaneous Death

The animals were killed at 72 h under general anesthesia by IV potassium chloride infusion. Spontaneous mortality was considered when this occurred prior to sacrifice.

Postmortem Studies
Lung Specimen Collection:

After death, the piglets remained on mechanical ventilation until specimen collection. The lungs were exposed through a cervicothoracic midline incision. Cultures were separately performed on the BAL retrieved from both the intact and abnormal lung areas. An aliquot of pooled BAL fluid was used for cytokine measurement. Thereafter, at least 1 cm3 peripheral lung tissue specimen was obtained while the lungs were maintained inflated. Specimens were cut into two parts for bacteriologic and pathologic studies.

Pathology:

Pulmonary vessels, pleura, and parenchyma were studied. Pneumonia was graded in accordance with previously published criteria8 as grades 0, no pneumonia; grade 1, purulent mucous plugging; grade 2, bronchiolitis; grade 3, pneumonia; grade 4, confluent pneumonia; and grade 5, abscessed pneumonia. Pneumonia was limited to the last three categories.

BAL

Six 20-mL aliquots of sterile saline solution (0.9% NaCl) were instilled through the bronchoscope channel and aspirated by hand.

CRP Determination

CRP was quantified by immunoturbidimetry. Reference values are up to 0.5 mg/dL.

Cytokine Concentrations

Tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 levels were measured in serum and BAL supernatant by enzyme-linked immunosorbent assay, based on the quantitative immunometric sandwich enzyme immunoassay technique (Quantikine; R&D Systems; Minneapolis, MN). The upper limits for serum concentrations in control subjects in our laboratory were as follows: TNF-α, 25 to 50 pg/mL; IL-6, < 39 pg/mL; and IL-10, < 31 pg/mL.

ABT Study Groups

Six piglets in the inappropriate ABT group received either IV ceftriaxone at 50 mg/kg bid beginning 2 h after inoculation or no ABT. The six animals in the appropriate ABT group received ciprofloxacin IV at 200 mg q8h (7 mg/kg tid) beginning either late (24 h after inoculation) or early (2 h after inoculation).

End Points

End points were spontaneous mortality, worsening of oxygenation, systemic inflammatory response (blood cytokines and CRP determinations), local inflammatory response (BAL cytokine determination), type and degree of lung histopathologic lesions, and bacteriologic response to ABT.

Approval by the Institutional Committee

The animals studied were treated in compliance with the guidelines of the ethics and research committees of the Hospital de Clínicas, and the Guide for the Care and Use of Laboratory Animals (NIH Publication No. 93–23, revised 1985).

Statistical Analysis

All data are expressed as mean ± SD. The Student t test for unpaired data was used to compare continuous variables. Physiologic, biochemical, and other biological parameter modifications according to time were evaluated by one-way analysis of variance for repeated measures; p < 0.05 was considered statistically significant.

Two piglets died suddenly during the first day and were replaced. The 12 remaining animals survived > 48 h. Five pigs died spontaneously (two at approximately 60 h and three pigs a few hours before the scheduled 72 h), and seven were killed. The piglets received ventilation following the model standardized by Marquette et al,5 with a relatively high Vt. Nonetheless, none had pneumothorax, a complication previously described in this model.

Clinical and Hemodynamic Findings

Tachycardia appeared early (heart rate time 0, 129.1 ± 31.3 beats/min; at 2 h, 159.8 ± 18.5 beats/min; p = 0.002). Diastolic BP dropped at 36 h. Fever achieved 39.4°C at 24 h (p = 0.02) compared with basal values (Fig 1 , top left, A). ABT (appropriate or inappropriate) did not modify any clinical or hemodynamic parameters except for fever, which was significantly higher at 72 h in piglets not receiving ABT (Fig 2 , top left, A).

Laboratory Findings

The most remarkable finding on blood analysis was the steep fall in Pao2/Fio2 ratio, which progressively worsened up to the end (Fig 1, top right, B). Sepsis-related biochemical abnormalities were not detected because pH, bicarbonate, and lactate values remained within the normal range. The WBC count remained high throughout the study period, with a wide range of values, similar to what occurred with blood glucose, billirrubin, sodium, aspartate aminotransferase, and alanine aminotransferase values (Table 1 ). Renal dysfunction was not observed, with serum creatinine values remaining normal during the study. Some abnormalities in basal or follow-up values (ie, hematocrit dropped from 30.1 ± 5.2 to 24.4 ± 4.3% after 72 h) were attributed to nonspecific physiologic variations in this animal model (Table 1). No differences observed in the laboratory findings were related to the ABT.

Respiratory Mechanics

As expected during the development of pneumonia and/or acute lung injury, airway pressures increased significantly at 2 h while static compliance decreased (Fig 1, bottom, C). No changes in respiratory mechanics attributable to the ABT were detected.

Cytokines and CRP

CRP increased significantly at 72 h (p = 0.01), while cytokine blood concentrations did not change (Table 1). On comparing the basal vs the final BAL cytokine concentrations, only TNF-α changed (280.6 ± 367.0 vs 48.5 ± 33.9, p = 0.04) [Fig 3 ]. Cytokines (serum or BAL) and CRP concentrations did not show any changes related to the appropriateness of the ABT. However, serum IL-10 at 24 h and 48 h (Fig 2, top right, B, bottom left, C, and bottom right, D), BAL IL-10 at 72 h, and BAL IL-6 at 72 h were higher in subjects not receiving ABT compared with those receiving appropriate or inappropriate ABT.

Histopathology Findings

Pneumonia developed in all the piglets (grades 3 to 5). Of 24 lung areas explored (2 in each pig), 21 showed evidence of lung infection: 14 had confluent and/or abscessed pneumonia (grades 4 and 5), 4 had mild pneumonia (grade 3), 2 had purulent mucous impaction (grade 2), and 1 had bronchiolitis (grade 1). Most had pneumonia in both explored areas; however, a few animals presented pathologic criteria of pneumonia only in the more compromised area. Although evidence of infection was less frequent in specimens from piglets receiving appropriate ABT, this difference was not significant (data not shown). Acute or subacute pleuritis was present in all subjects, with vascular lesions (endothelial or thrombosis) present in seven subjects and alveolar damage in five subjects (Fig 4 ). Thrombosis was associated with a higher temperature, higher initial blood CRP and TNF- α, increased blood IL-6, increased BAL IL-6 and decreased TNF-α at 72 h, and spontaneous death (Fig 5 ).

Microbiology

P aeruginosa was present in all BAL fluid or lung tissue samples. BAL findings were positive at concentrations ≥ 104 cfu/mL in animals not receiving ABT, being negative (no grow) in three pigs and positive at a concentration of < 104 cfu/mL in the other five pigs receiving ABT (Table 2 ). Lung tissue culture findings were negative in two animals (both receiving appropriate ABT), while a growth ≥ 104 cfu/mL was observed in only one pig (not receiving ABT) [Table 2]. Although pneumonia was present in all the piglets, growth ≥ 104 cfu/mL in the BAL culture was obtained in 100% of those in the no-ABT group, but only in 22% of those receiving ABT. Appropriate or inappropriate ABT was associated with negative BAL and lung tissue culture findings in pathologically confirmed SPMV (p = 0.027) [Fig 6 ]. The appropriateness of ABT did not produce measurable changes. Bacteremia due to P aeruginosa was not detected in any subject (Table 2).

This SPMV porcine model standardized by Marquette et al5 has been useful in advancing the knowledge in the field of VAP.2,9 Pneumonia developed after inoculation in all piglets studied, with the presence and grade of pneumonia being independent of the appropriateness of ABT.

SPMV produced tachycardia, fever, and diastolic hypotension. However, there was no other physiologic, clinical, or biochemical evidence consistent with septic shock. However, the Pao2/Fio2 ratio fell to 65% of its initial value at 24 h, while airway pressures increased and lung compliance decreased in accordance with the worsening in oxygenation. A relatively stable hemodynamics contrasting with severe respiratory compromise has been previously described.5 This suggests local rather than systemic response to infection in this model, with the lack of bacteremia supporting this hypothesis. However, some systemic impact coexists with local response producing a simultaneous rise in blood CRP and a fall in BAL fluid TNF-α. Increased serum CRP and down-regulation of BAL TNF-α have been described during lung infection.1011

It has been recognized that appropriate ABT improves the outcome of SPMV12while reducing the yield of deep lung cultures.13 The use of either ABT reduced the spontaneous mortality and positivity of cultures in this model. Additionally, the use of appropriate or inappropriate ABT produced a measurable effect on body temperature, serum IL-10 and BAL IL-6 and IL-10 concentrations between 24 h and 72 h after inoculation.

Quantitative BAL fluid cultures from all the subjects not receiving ABT yielded ≥ 104 cfu/mL of P aeruginosa as the only microorganism isolated, thereby confirming the high diagnostic accuracy and pathogen identification of BAL culture for pneumonia in subjects not receiving antimicrobials. Conversely, the accuracy of BAL culture was reduced in the animals receiving ABT. This fact confirms the limited usefulness of BAL culture for evaluating the presence of infection and the appropriateness of ABT in subjects receiving prior ABT.1417

P aeruginosa was isolated, at least at low counts, in BAL or lung tissue in all the piglets, but the diagnostic threshold of pneumonia of ≥ 104 cfu/g of lung tissue was seldom achieved. Pneumonia is a pathologic diagnosis and a bacterial growth < 104 cfu/g during the first 3 days after inoculation should not be considered as evidence to rule out the presence of pneumonia.

The dynamics of serum or BAL cytokine, reflecting systemic and local inflammatory activity, was modified by ABT. This approach may be useful to study clinical response to other therapeutic strategies (corticosteroids, immune modulators). The preventive effect of cytokines has been suggested in SPMV18 and could be tested in this model of exogenously acquired pneumonia in the future.

Interestingly, lung vessel thrombosis was associated with significant local and systemic (clinical, physiologic, and biological) impact. This may reflect the severity of pneumonia associated with advanced alveolar damage. Endothelial cell destruction has long been recognized as a key feature of ARDS.19Local inflammation leads to increased tissue factor production and fibrinolysis inhibition. The resulting procoagulant environment is proinflammatory because of excessive fibrin deposition and cross-talk between coagulation and inflammation.20 TNF-α and IL-6 released into the circulation produce the up-regulation of the expression of tissue factor, a major initiator of intravascular coagulation, on monocytes and endothelial cells. Overt disseminated intravascular coagulation is present in few patients, but an elevated d-dimer concentrations and abnormalities of the protein C system are almost universal findings.18 Increased local procoagulant activity associated with hypoxemia has been described in VAP patients receiving inadequate ABT.21 In addition, a significant pulmonary vascular resistance increase has been described in piglets developing SPMV.5 Unfortunately, we did not study coagulation in the present model. The finding of thrombosis associated with SPMV may have therapeutic implications.

One of the limitations of this study was the small number of animals included, which may not confirm an expected clinical improvement, changes in cytokine concentrations, or bacterial clearance enhancement under appropriate ABT. We used the ventilator settings described by Marquette et al,5 although a lung-protective ventilatory approach may have decreased the degree of lung injury attributable to a large Vt. The high mortality at 72 h prevented the prolongation of the observation time in this SPMV model.

This SPMV model produces several of the consequences observed in VAP. These occur after the massive entrance of a high concentration of microorganisms, which is not the usual method of acquiring VAP. Our findings should be evaluated carefully because they do not necessarily apply to VAP.

In summary, inoculation of P aeruginosa produced SPMV resembling VAP in humans. BAL culture was found to be highly accurate in the diagnosis of SPMV and its etiology in piglets not receiving ABT. Blood CRP concentrations rose and BAL TNF-α fell, consistent with systemic and local inflammatory impact, being more common in piglets with arterial thrombosis and worse in piglets not receiving ABT. Future studies are required to determine the impact of SPMV on procoagulant activity and right-heart hemodynamics, and to study how innovative therapies may modify the outcome of this disease.

Abbreviations: ABT = antibiotic therapy; CRP = C-reactive protein; Fio2 = fraction of inspired oxygen; IL = interleukin; SPMV = severe pneumonia under mechanical ventilation; TNF = tumor necrosis factor; VAP = ventilator-associated pneumonia; Vt = tidal volume

This work was funded by Sección Infecciones, Asociación Argentina de Medicina Respiratoria; Institut d’Investigacions Biomediques August Pi i Sunyer, Barcelona, España, and supported by CIBER CB06/06/0028.

Dr. Luna has served on the advisory board for Bayer for $1,500, and was a speaker for AstraZeneca and received $2,000. The other authors have no conflicts of interest to disclose.

Figure Jump LinkFigure 1. Top left, A: After inoculation, the temperature rose steeply, being 36.6 ± 1.0°C at baseline and rising to 39.4 ± 1.4°C at 24 h (*) [p = 0.0002] and 38.1 ± 1.8°C at 48 h (‡) [p = 0.021]. Top right, B: Pao2/Fio2 decreased over time, becoming significant 24 h after inoculation, being 386 at baseline and 242 mm Hg at 24 h (*) [p = 0.034]. Bottom, C: Peak and plateau pressures and compliance in the overall population at the different time points from the time of inoculation to the time of death. A continuous increase in airway pressures (P) was obvious from the beginning of the experiment, achieving significance at 2 h (p = 0.003 for peak [*] and p = 0.007 for plateau [§] pressures). Static compliance reduction became significant at 72 h (‡) [p = 0.009]. These changes may be attributed to pneumonia and to acute lung injury.Grahic Jump Location
Figure Jump LinkFigure 2. Effects attributable to the use of either appropriate (ciprofloxacin) or inappropriate (ceftriaxone) ABT on temperature and serum and BAL cytokine concentrations at different time points. Top left, A: Body temperature tended to be higher in piglets not receiving ABT, beginning 24 h after inoculation. This difference became significant at the last measurement before death (*) [p = 0.018]. Top right, B: Serum IL-10 was lower in piglets receiving ABT at 24 h (*) [p = 0.006] and at 48 h (‡) [p = 0.046] after inoculation. Bottom left, C: BAL IL-10 concentration was lower in piglets receiving ABT (*) [p = 0.040] at the time of death. Bottom right, D: IL-6 concentrations were lower in piglets receiving ABT (*) [p = 0.008] at the time of death. HS = hours.Grahic Jump Location
Table Graphic Jump Location
Table 1. Hematology, Blood Chemistry, Lactate, CRP, and Cytokines in All Piglets at Different Time Points (0, 24, 48, and 72 h) After the Onset of the Experiment*
* 

Data are presented as mean ± SD.

 

p < 0.05 comparing 0 h with 72 h.

Figure Jump LinkFigure 3. Determinations of IL-6 (top), IL-10 (center), and TNF-α (bottom) in BAL fluid before the inoculation and at the end of the study. * = TNF-α values were significantly lower at 72 h.Grahic Jump Location
Figure Jump LinkFigure 4. Top left, A: Microphotograph showing pneumonia (consolidation coexisting with significant accumulation of polymorphonuclear leukocytes, fibrinous exudates and cellular debris in the alveolar space) and abscessed pneumonia (arrow), cellular necrosis coexisting with disruption of cellular architecture, grades 3–4 and 5 (hematoxylin-eosin, original × 50). Top right, B: Microphotograph showing an arterial vessel presenting an occluding fibrin-hematic thrombus (hematoxylin-eosin, original × 100). Bottom left, C: Microphotograph showing alveolar spaces with polymorphonuclear leukocyte infiltration presenting hyaline membranes covering the alveolar epithelium (hematoxylin-eosin, original × 250). Bottom right, D: Microphotograph showing bronchial lumen presenting purulent mucous plugging (arrows). The surrounding parenchyma shows evidence of acute pneumonia (hematoxylin-eosin, original × 40).Grahic Jump Location
Figure Jump LinkFigure 5. Significant serum and BAL fluid changes in the concentration of CRP and cytokines in the three piglets presenting pulmonary arterial thrombosis at autopsy. These piglets presented higher initial blood CRP and TNF-α values (top left and bottom left panels), increased blood IL-6 at 48 h and 72 h (center left panel), and decreased BAL IL-6 and TNF-α at 72 h (top right and center right panels). Bottom right: Body temperature in piglets with and without thrombosis (TROM).Grahic Jump Location
Table Graphic Jump Location
Table 2. Antimicrobial Therapy and BAL, Lung, and Blood Cultures Obtained by the Time of Death
Figure Jump LinkFigure 6. Differences in the bacterial burden observed in lung tissue culture between piglets not receiving ABT vs those receiving either inappropriate ABT (ceftriaxone [CRO]) or appropriate ABT (ciprofloxacin [CIP]). The difference between the colony forming units per milliliter in the lung tissue of piglets not receiving ABT vs those receiving either ABT was significant (p = 0.007). E = early; L = late.Grahic Jump Location

We thank Diego Goffredo, MD, and Didier Bruno, MD, for help with preparing the experimental model, and Oscar Maldonado and Monica Pierdominici for technical support during the experiment.

Vincent, JL, Bihari, DJ, Suter, PM, et al (1995) The prevalence of nosocomial infection in intensive care units in Europe: results of the European Prevalence of Infection in Intensive Care (EPIC) Study; EPIC International Advisory Committee.JAMA274,639-644. [PubMed] [CrossRef]
 
Goldstein, I, Bughalo, MT, Marquette, CH, et al Mechanical ventilation-induced air-space enlargement during experimental pneumonia in piglets.Am J Respir Crit Care Med2001;163,958-964. [PubMed]
 
Crouch Brewer, S, Wunderink, RG, et al Ventilator associated pneumonia due toPseudomona aeruginosa.Chest1996;109,1019-1029. [PubMed]
 
Fagon, JY, Chastre, J, Domart, Y, et al Nosocomial pneumonia in patients receiving continuous mechanical ventilation: prospective analysis of 52 episodes with use of a protected specimen brush and quantitative culture techniques.Am Rev Respir Dis1989;139,877-884. [PubMed]
 
Marquette, CH, Wermert, D, Wallet, F, et al Characterization of an animal model of ventilator-acquired pneumonia.Chest1999;115,200-209. [PubMed]
 
Tonnellier, M, Ferrari, F, Goldstein, I, et al Intravenous versus nebulized ceftazidime in ventilated piglets with and without experimental bronchopneumonia: comparative effects of helium and nitrogen.Anesthesiology2005;102,995-1000. [PubMed]
 
Elman, M, Goldstein, I, Marquette, CH, et al Influence of lung aeration on pulmonary concentrations of nebulized and intravenous amikacin in ventilated piglets with severe bronchopneumonia.Anesthesiology2002;97,199-206. [PubMed]
 
Marquette, CH, Mensier, E, Copin, MC, et al Experimental models of tracheobronchial stenoses: a useful tool for evaluating airway stents.Ann Thorac Surg1995;60,651-656. [PubMed]
 
Goldstein, I, Wallet, F, Robert, J, et al Lung tissue concentrations of nebulized amikacin during mechanical ventilation in piglets with healthy lungs.Am J Respir Crit Care Med2002;165,171-175. [PubMed]
 
Flanders, SA, Stein, J, Shochat, G, et al Performance of a bedside C-reactive protein test in the diagnosis of community-acquired pneumonia in adults with acute cough.Am J Med2004;116,529-535. [PubMed]
 
Bergeron, Y, Ouellet, N, Deslauriers, A, et al Cytokine kinetics and other factors in response to pneumococcal pulmonary infection in mice.Infect Inmun1998;66,912-922
 
Luna, CM, Vujacich, P, Niederman, MS, et al Impact of BAL data on the therapy and outcome of ventilator-associated pneumonia.Chest1997;111,676-685. [PubMed]
 
Garrard, CS, A’Court, CD The diagnosis of pneumonia in the critically ill.Chest1995;108,15S-25S
 
Chastre, J, Fagon, JY Ventilator-associated pneumonia.Am J Respir Crit Care Med2002;165,867-903. [PubMed]
 
Marquette, CH, Copin, MC, Wallet, F, et al Relationship between microbiologic and histologic features in bacterial pneumonia.Am J Respir Crit Care Med1996;154,1784-1787. [PubMed]
 
Prats, E, Dorca, J, Pujol, M, et al Effects of antibiotics on protected specimen brush sampling in ventilator-associated pneumonia.Eur Respir J2002;19,944-951. [PubMed]
 
Luna, CM, Aruj, P, Niederman, MS, et al Appropriateness and delay to initiate therapy in ventilator-associated pneumonia.Eur Respir J2006;27,158-164. [PubMed]
 
Bernard, GR, Vincent, JL, Laterre, PF, et al Efficacy and safety of recombinant human activated protein C for severe sepsis.N Engl J Med2001;344,699-709. [PubMed]
 
Rinaldo, JE, Rogers, RM Adult respiratory-distress syndrome: changing concepts of lung injury and repair.N Engl J Med1982;306,900-909. [PubMed]
 
Zimmerman, GA, Renzetti, AD, Hill, HR Granulocyte adherence in pulmonary and systemic arterial blood samples from patients with adult respiratory distress syndrome.Am Rev Respir Dis1984;129,798-804. [PubMed]
 
El-Solh, AA, Okada, M, Pietrantoni, C, et al Procoagulant and fibrinolytic activity in ventilator-associated pneumonia: impact of inadequate antimicrobial therapy.Intensive Care Med2004;14,1914-1920
 

Figures

Figure Jump LinkFigure 1. Top left, A: After inoculation, the temperature rose steeply, being 36.6 ± 1.0°C at baseline and rising to 39.4 ± 1.4°C at 24 h (*) [p = 0.0002] and 38.1 ± 1.8°C at 48 h (‡) [p = 0.021]. Top right, B: Pao2/Fio2 decreased over time, becoming significant 24 h after inoculation, being 386 at baseline and 242 mm Hg at 24 h (*) [p = 0.034]. Bottom, C: Peak and plateau pressures and compliance in the overall population at the different time points from the time of inoculation to the time of death. A continuous increase in airway pressures (P) was obvious from the beginning of the experiment, achieving significance at 2 h (p = 0.003 for peak [*] and p = 0.007 for plateau [§] pressures). Static compliance reduction became significant at 72 h (‡) [p = 0.009]. These changes may be attributed to pneumonia and to acute lung injury.Grahic Jump Location
Figure Jump LinkFigure 2. Effects attributable to the use of either appropriate (ciprofloxacin) or inappropriate (ceftriaxone) ABT on temperature and serum and BAL cytokine concentrations at different time points. Top left, A: Body temperature tended to be higher in piglets not receiving ABT, beginning 24 h after inoculation. This difference became significant at the last measurement before death (*) [p = 0.018]. Top right, B: Serum IL-10 was lower in piglets receiving ABT at 24 h (*) [p = 0.006] and at 48 h (‡) [p = 0.046] after inoculation. Bottom left, C: BAL IL-10 concentration was lower in piglets receiving ABT (*) [p = 0.040] at the time of death. Bottom right, D: IL-6 concentrations were lower in piglets receiving ABT (*) [p = 0.008] at the time of death. HS = hours.Grahic Jump Location
Figure Jump LinkFigure 3. Determinations of IL-6 (top), IL-10 (center), and TNF-α (bottom) in BAL fluid before the inoculation and at the end of the study. * = TNF-α values were significantly lower at 72 h.Grahic Jump Location
Figure Jump LinkFigure 4. Top left, A: Microphotograph showing pneumonia (consolidation coexisting with significant accumulation of polymorphonuclear leukocytes, fibrinous exudates and cellular debris in the alveolar space) and abscessed pneumonia (arrow), cellular necrosis coexisting with disruption of cellular architecture, grades 3–4 and 5 (hematoxylin-eosin, original × 50). Top right, B: Microphotograph showing an arterial vessel presenting an occluding fibrin-hematic thrombus (hematoxylin-eosin, original × 100). Bottom left, C: Microphotograph showing alveolar spaces with polymorphonuclear leukocyte infiltration presenting hyaline membranes covering the alveolar epithelium (hematoxylin-eosin, original × 250). Bottom right, D: Microphotograph showing bronchial lumen presenting purulent mucous plugging (arrows). The surrounding parenchyma shows evidence of acute pneumonia (hematoxylin-eosin, original × 40).Grahic Jump Location
Figure Jump LinkFigure 5. Significant serum and BAL fluid changes in the concentration of CRP and cytokines in the three piglets presenting pulmonary arterial thrombosis at autopsy. These piglets presented higher initial blood CRP and TNF-α values (top left and bottom left panels), increased blood IL-6 at 48 h and 72 h (center left panel), and decreased BAL IL-6 and TNF-α at 72 h (top right and center right panels). Bottom right: Body temperature in piglets with and without thrombosis (TROM).Grahic Jump Location
Figure Jump LinkFigure 6. Differences in the bacterial burden observed in lung tissue culture between piglets not receiving ABT vs those receiving either inappropriate ABT (ceftriaxone [CRO]) or appropriate ABT (ciprofloxacin [CIP]). The difference between the colony forming units per milliliter in the lung tissue of piglets not receiving ABT vs those receiving either ABT was significant (p = 0.007). E = early; L = late.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1. Hematology, Blood Chemistry, Lactate, CRP, and Cytokines in All Piglets at Different Time Points (0, 24, 48, and 72 h) After the Onset of the Experiment*
* 

Data are presented as mean ± SD.

 

p < 0.05 comparing 0 h with 72 h.

Table Graphic Jump Location
Table 2. Antimicrobial Therapy and BAL, Lung, and Blood Cultures Obtained by the Time of Death

References

Vincent, JL, Bihari, DJ, Suter, PM, et al (1995) The prevalence of nosocomial infection in intensive care units in Europe: results of the European Prevalence of Infection in Intensive Care (EPIC) Study; EPIC International Advisory Committee.JAMA274,639-644. [PubMed] [CrossRef]
 
Goldstein, I, Bughalo, MT, Marquette, CH, et al Mechanical ventilation-induced air-space enlargement during experimental pneumonia in piglets.Am J Respir Crit Care Med2001;163,958-964. [PubMed]
 
Crouch Brewer, S, Wunderink, RG, et al Ventilator associated pneumonia due toPseudomona aeruginosa.Chest1996;109,1019-1029. [PubMed]
 
Fagon, JY, Chastre, J, Domart, Y, et al Nosocomial pneumonia in patients receiving continuous mechanical ventilation: prospective analysis of 52 episodes with use of a protected specimen brush and quantitative culture techniques.Am Rev Respir Dis1989;139,877-884. [PubMed]
 
Marquette, CH, Wermert, D, Wallet, F, et al Characterization of an animal model of ventilator-acquired pneumonia.Chest1999;115,200-209. [PubMed]
 
Tonnellier, M, Ferrari, F, Goldstein, I, et al Intravenous versus nebulized ceftazidime in ventilated piglets with and without experimental bronchopneumonia: comparative effects of helium and nitrogen.Anesthesiology2005;102,995-1000. [PubMed]
 
Elman, M, Goldstein, I, Marquette, CH, et al Influence of lung aeration on pulmonary concentrations of nebulized and intravenous amikacin in ventilated piglets with severe bronchopneumonia.Anesthesiology2002;97,199-206. [PubMed]
 
Marquette, CH, Mensier, E, Copin, MC, et al Experimental models of tracheobronchial stenoses: a useful tool for evaluating airway stents.Ann Thorac Surg1995;60,651-656. [PubMed]
 
Goldstein, I, Wallet, F, Robert, J, et al Lung tissue concentrations of nebulized amikacin during mechanical ventilation in piglets with healthy lungs.Am J Respir Crit Care Med2002;165,171-175. [PubMed]
 
Flanders, SA, Stein, J, Shochat, G, et al Performance of a bedside C-reactive protein test in the diagnosis of community-acquired pneumonia in adults with acute cough.Am J Med2004;116,529-535. [PubMed]
 
Bergeron, Y, Ouellet, N, Deslauriers, A, et al Cytokine kinetics and other factors in response to pneumococcal pulmonary infection in mice.Infect Inmun1998;66,912-922
 
Luna, CM, Vujacich, P, Niederman, MS, et al Impact of BAL data on the therapy and outcome of ventilator-associated pneumonia.Chest1997;111,676-685. [PubMed]
 
Garrard, CS, A’Court, CD The diagnosis of pneumonia in the critically ill.Chest1995;108,15S-25S
 
Chastre, J, Fagon, JY Ventilator-associated pneumonia.Am J Respir Crit Care Med2002;165,867-903. [PubMed]
 
Marquette, CH, Copin, MC, Wallet, F, et al Relationship between microbiologic and histologic features in bacterial pneumonia.Am J Respir Crit Care Med1996;154,1784-1787. [PubMed]
 
Prats, E, Dorca, J, Pujol, M, et al Effects of antibiotics on protected specimen brush sampling in ventilator-associated pneumonia.Eur Respir J2002;19,944-951. [PubMed]
 
Luna, CM, Aruj, P, Niederman, MS, et al Appropriateness and delay to initiate therapy in ventilator-associated pneumonia.Eur Respir J2006;27,158-164. [PubMed]
 
Bernard, GR, Vincent, JL, Laterre, PF, et al Efficacy and safety of recombinant human activated protein C for severe sepsis.N Engl J Med2001;344,699-709. [PubMed]
 
Rinaldo, JE, Rogers, RM Adult respiratory-distress syndrome: changing concepts of lung injury and repair.N Engl J Med1982;306,900-909. [PubMed]
 
Zimmerman, GA, Renzetti, AD, Hill, HR Granulocyte adherence in pulmonary and systemic arterial blood samples from patients with adult respiratory distress syndrome.Am Rev Respir Dis1984;129,798-804. [PubMed]
 
El-Solh, AA, Okada, M, Pietrantoni, C, et al Procoagulant and fibrinolytic activity in ventilator-associated pneumonia: impact of inadequate antimicrobial therapy.Intensive Care Med2004;14,1914-1920
 
NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging & repositioning the boxes below.

CHEST Journal Articles
PubMed Articles
  • CHEST Journal
    Print ISSN: 0012-3692
    Online ISSN: 1931-3543