Prevention of gram negative nosocomial bronchopneumonia by intratracheal colistin in critically ill patients. Histologic and bacteriologic study

Rebound Inverts the Staphylococcus aureus Bacteremia Prevention Effect of Antibiotic Based Decontamination Interventions in ICU Cohorts with Prolonged Length of Stay

Could rebound explain the paradoxical lack of prevention effect against Staphylococcus aureus blood stream infections (BSIs) with antibiotic-based decontamination intervention (BDI) methods among studies of ICU patients within the literature? Two meta-regression models were applied, each versus the group mean length of stay (LOS). Firstly, the prevention effects against S. aureus BSI [and S. aureus VAP] among 136 studies of antibiotic-BDI versus other interventions were analyzed. Secondly, the S. aureus BSI [and S. aureus VAP] incidence in 268 control and intervention cohorts from studies of antibiotic-BDI versus that among 165 observational cohorts as a benchmark was modelled. In model one, the meta-regression line versus group mean LOS crossed the null, with the antibiotic-BDI prevention effect against S. aureus BSI at mean LOS day 7 (OR 0.45; 0.30 to 0.68) inverted at mean LOS day 20 (OR 1.7; 1.1 to 2.6). In model two, the meta-regression line versus group mean LOS crossed the benchmark line, and the predicted S. aureus BSI incidence for antibiotic-BDI groups was 0.47; 0.09-0.84 percentage points below versus 3.0; 0.12-5.9 above the benchmark in studies with 7 versus 20 days mean LOS, respectively. Rebound within the intervention groups attenuated and inverted the prevention effect of antibiotic-BDI against S. aureus VAP and BSI, respectively. This explains the paradoxical findings.

Inhaled Amikacin to Prevent Ventilator-Associated Pneumonia

BACKGROUND

Whether preventive inhaled antibiotics may reduce the incidence of ventilator-associated pneumonia is unclear.

METHODS

In this investigator-initiated, multicenter, double-blind, randomized, controlled, superiority trial, we assigned critically ill adults who had been undergoing invasive mechanical ventilation for at least 72 hours to receive inhaled amikacin at a dose of 20 mg per kilogram of ideal body weight once daily or to receive placebo for 3 days. The primary outcome was a first episode of ventilator-associated pneumonia during 28 days of follow-up. Safety was assessed.

RESULTS

A total of 850 patients underwent randomization, and 847 were included in the analyses (417 assigned to the amikacin group and 430 to the placebo group). All three daily nebulizations were received by 337 patients (81%) in the amikacin group and 355 patients (83%) in the placebo group. At 28 days, ventilator-associated pneumonia had developed in 62 patients (15%) in the amikacin group and in 95 patients (22%) in the placebo group (difference in restricted mean survival time to ventilator-associated pneumonia, 1.5 days; 95% confidence interval [CI], 0.6 to 2.5; P = 0.004). An infection-related ventilator-associated complication occurred in 74 patients (18%) in the amikacin group and in 111 patients (26%) in the placebo group (hazard ratio, 0.66; 95% CI, 0.50 to 0.89). Trial-related serious adverse effects were seen in 7 patients (1.7%) in the amikacin group and in 4 patients (0.9%) in the placebo group.

CONCLUSIONS

Among patients who had undergone mechanical ventilation for at least 3 days, a subsequent 3-day course of inhaled amikacin reduced the burden of ventilator-associated pneumonia during 28 days of follow-up. (Funded by the French Ministry of Health; AMIKINHAL ClinicalTrials.gov number, NCT03149640; EUDRA Clinical Trials number, 2016-001054-17.).

Prophylactic antibiotics for preventing ventilator-associated pneumonia: a pairwise and Bayesian network meta-analysis

BACKGROUND

The role of prophylactic antibiotics in preventing ventilator-associated pneumonia (VAP) in patients undergoing invasive mechanical ventilation (IMV) remains unclear. This network meta-analysis compared the efficacy and safety of antibiotic prophylaxis in preventing VAP in an IMV population in intensive-care units (ICUs).

METHODS

We searched the PubMed, Web of Science, Embase, and Cochrane Library databases from inception to December 2021, to identify relevant studies assessing the impact of prophylactic antibiotics on the incidence of VAP, the mortality, and the duration of ICU stays and hospitalization to perform a meta-analysis.

RESULTS

Thirteen studies (2144 patients) were included, 12 of which were selected for the primary analysis, which revealed that treatment with prophylactic antibiotics resulted in a lower VAP rate compared with control groups [risk ratio (RR) = 0.62]. Bayesian network meta-analysis indicated that aerosolized tobramycin and intravenous ampicillin-sulbactam presented the greatest likelihood being the most efficient regimen for reducing VAP.

CONCLUSIONS

Antibiotic prophylaxis may reduce the incidence of VAP, but not the mortality, for adult patients undergoing IMV in ICUs. Tobramycin via nebulization and ampicillin-sulbactam via intravenous administration presented the greatest likelihood of being the most efficient regimen for preventing VAP. However, well-designed randomized studies are warranted before definite recommendations can be made.

Comparison of the clinical efficacy and toxicity of nebulized polymyxin monotherapy and combined intravenous and nebulized polymyxin for the treatment of ventilator-associated pneumonia caused by carbapenem-resistant gram-negative bacteria: a retrospective cohort study

Objective: To investigate the clinical efficacy and toxicity of nebulized polymyxin monotherapy and combined intravenous and nebulized polymyxin for the treatment of VAP caused by CR-GNB. Additionally, among patients treated with nebulized polymyxin monotherapy, we compared the clinical efficacy and toxicity of polymyxin B and polymyxin E. Methods: This study was a single-center, retrospective study. Included patients received aerosolized polymyxin for at least 72 h with or without intravenous polymyxin for the management of CR-GNB VAP. The primary endpoint was clinical cure at the end of polymyxin therapy. Secondary endpoints included AKI incidence, time of bacteria-negative conversion, duration of MV after inclusion, length of stay in ICU, and all-cause ICU mortality. Results: 39 patients treated with nebulized polymyxin monotherapy were assigned to the NL-polymyxin group. 39 patients treated with nebulized polymyxin combined with intravenous use of polymyxin were assigned to the IV-NL-polymyxin group. Among the NL-polymyxin group, 19 patients were treated with polymyxin B and 20 with polymyxin E. The clinical baseline characteristics before admission to the ICU and before nebulization of polymyxin were similar between the two groups. No differences were found between the two study groups in terms of microorganism distribution, VAP cure rate, time of bacteria-negative conversion, duration of MV after inclusion, length of stay in ICU and all-cause ICU mortality. Similarly, survival analysis did not differ between the two groups (χ2 = 3.539, p = 0.06). AKI incidence was higher in the IV-NL-polymyxin group. When comparing the clinical efficacy and toxicity to polymyxin B and polymyxin E, there was no difference between the two groups in terms of VAP cure rate, time of bacteria-negative conversion, duration of MV after inclusion, length of stay in ICU, SOFA score, CPIS, AKI incidence and all-cause ICU mortality. Conclusion: Our study found that nebulized polymyxin monotherapy was non-inferior to combination therapy with intravenous polymyxin in treating CR-GNB-VAP. Furthermore, we observed no differences in clinical efficacy or related toxic side effects between polymyxin B and polymyxin E during nebulized polymyxin therapy as monotherapy. However, future prospective studies with larger sample sizes are required to confirm these findings.

Aerosolized Antibiotics to Manage Ventilator-Associated Infections: A Comprehensive Review

BACKGROUND

Ventilator-associated lower respiratory tract infectious complications in critically ill patients cover a wide spectrum of one disease process (respiratory infection), initiating from tracheal tube and/or tracheobronchial colonization, to ventilator associated tracheobronchitis (VAT) and ventilator-associated pneumonia (VAP). VAP occurence has been associated with increased intensive care unit (ICU) morbidity (ventilator days, as well as length of ICU and hospital stay) and ICU mortality. Therefore, treatments that aim at VAP/VAT incidence reduction are a high priority.

AIM

The aim of the present review is to discuss the current literature concerning two major aspects: (a) can aerosolized antibiotics (AA) administered in a pre-emptive way prevent the occurrence of ventilator-associated infections? and (b) can VAT treatment with aerosolized avert the potential evolution to VAP?

RESULTS

There were identified eight studies that provided data on the use of aerosolized antibiotics for the prevention of VAT/VAP. Most of them report favorable data on reducing the colonisation rate and the progression to VAP/VAT. Another four studies dealt with the treatment of VAT/VAP. The results support the decrease in the incidence to VAP transition and/or the improvement in signs and symptoms of VAP. Moreover, there are concise reports on higher cure rates and microbiological eradication in patients treated with aerosolized antibiotics. Yet, differences in the delivery modality adopted and resistance emergence issues preclude the generalisability of the results.

CONCLUSION

Aerosolized antibiotic therapy can be used to manage ventilator-associated infections, especially those with difficult to treat resistance. The limited clinical data raise the need for large randomized controlled trials to confirm the benefits of AA and to evaluate the impact on antibiotic selection pressure.

Role of nebulized colistin as a substitutive strategy against nosocomial pneumonia caused by CR-GNB in intensive care units: a retrospective cohort study

BACKGROUND

Adverse reactions, especially nephrotoxicity, are great concerns of intravenous colistin treatment. The role of substitutive nebulized colistin in treating nosocomial pneumonia caused by carbapenem-resistant Gram-negative bacterial (CR-GNB) in critically ill patients remains unknown.

METHODS

This retrospective study enrolled patients with nosocomial pneumonia caused by colistin-susceptible CRGNB in the intensive care unit (ICU) without intravenous colistin treatment. Patients were categorized based on whether substitutive nebulized colistin was used alongside other intravenous antibiotics. Clinical responses and mortality rates were compared between the two groups in the original and propensity score (PS)-matched cohorts. This study aimed to investigate the clinical effectiveness of substitutive nebulized colistin in treatment outcomes of nosocomial pneumonia caused by CR-GNB. The impact of dosing strategy of nebulized colistin was also explored.

RESULTS

In total, 343 and 214 patients with and without substitutive nebulized colistin, respectively, were enrolled for analysis. In the PS-matched cohort, clinical failure rates on day 7 (22.6 vs. 42.6%, p = 0.001), day 14 (27.0 vs. 42.6%, p = 0.013), and day 28 (27.8 vs. 41.7%, p = 0.027) were significantly lower in patients with nebulized colistin. In multivariate analysis, nebulized colistin was an independent factor associated with lower day 14 clinical failure (Original cohort: adjusted odds ratio (aOR) 0.45, 95% confidence interval (CI) 0.30-0.67; PS-matched cohort: aOR 0.48, 95% CI 0.27-0.87). There were no differences in clinical failure rate and mortality rate between patients receiving high (> 6 MIU/day) and low (≤ 6 MIU/day) dose nebulized colistin in the PS-matched cohort.

CONCLUSIONS

In ICU-admitted patients with nosocomial pneumonia caused by colistin-susceptible CRGNB, substitutive nebulized colistin was associated with better clinical outcomes.

Secondary Prophylaxis With Inhaled Colistin to Prevent Recurrence of Pseudomonas aeruginosa and Extended-spectrum β-lactamase-producing Enterobacterales Pneumonia in ICU After Lung Transplantation: A Before-and-after Retrospective Cohort Analysis

BACKGROUND

Early pneumonia is an independent risk factor for 1-y mortality after lung transplantation (LTx). Pseudomonas aeruginosa is the most common isolate in early pneumonia and is also associated with an increased risk of chronic lung allograft dysfunction. The aim of our study was to evaluate the efficacy of secondary prophylaxis with inhaled colistin (IC) in preventing the recurrence of P aeruginosa or extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE) pneumonia in the postoperative period in the intensive care unit after LTx.

METHODS

We conducted a before-and-after retrospective cohort study by including all patients who underwent LTx between January 2015 and December 2020 in our center. Secondary prophylaxis with IC was instituted in January 2018 (observation period from January 2015 to December 2017, intervention period from January 2018 to December 2020).

RESULTS

A total of 271 lung transplants were included (125 in the observation period and 146 in the intervention period). The patients were predominately male (64.2%) with a median age of 57 y and received double LTx (67.9%) for chronic obstructive pulmonary disease/emphysema (36.2%) or interstitial lung disease (48.3%). The proportion of patients who experienced at least 1 recurrence of P aeruginosa or ESBL-PE pneumonia was significantly lower in the intervention period than in the observation period (0.7% versus 7.2%, P = 0.007).

CONCLUSIONS

Our study suggests a potential benefit of secondary prophylaxis with IC to prevent the recurrence of P aeruginosa or ESBL-PE pneumonia in the intensive care unit after LTx.

Nebulized Antibiotics for Healthcare- and Ventilator-Associated Pneumonia

Global emergence of multidrug-resistant and extensive drug-resistant gram-negative bacteria has increased the risk of treatment failure, especially for healthcare- or ventilator-associated pneumonia (HAP/VAP). Nebulization of antibiotics, by providing high intrapulmonary antibiotic concentrations, represents a promising approach to optimize the treatment of HAP/VAP due to multidrug-resistant and extensive drug-resistant gram-negative bacteria, while limiting systemic antibiotic exposure. Aminoglycosides and colistin methanesulfonate are the most common nebulized antibiotics. Although optimal nebulized drug dosing regimen is not clearly established, high antibiotic doses should be administered using vibrating-mesh nebulizer with optimized ventilator settings to ensure safe and effective intrapulmonary concentrations. When used preventively, nebulized antibiotics reduced the incidence of VAP without any effect on mortality. This approach is not yet recommended and large randomized controlled trials should be conducted to confirm its benefit and explore the impact on antibiotic selection pressure. Compared with high-dose intravenous administration, high-dose nebulized colistin methanesulfonate seems to be more effective and safer in the treatment of ventilator-associated tracheobronchitis and VAP caused by multidrug resistant and extensive-drug resistant gram-negative bacteria. Adjunctive nebulized aminoglycosides could increase the clinical cure rate and bacteriological eradication in patients suffering from HAP/VAP due to multidrug-resistant and extensive drug-resistant gram-negative bacteria. As nebulized aminoglycosides broadly diffuse in the systemic circulation of patients with extensive bronchopneumonia, monitoring of plasma trough concentrations is recommended during the period of nebulization. Large randomized controlled trials comparing high dose of nebulized colistin methanesulfonate to high dose of intravenous colistin methanesulfonate or to intravenous new β-lactams in HAP/VAP due to multidrug-resistant and extensive drug-resistant gram-negative bacteria are urgently needed.

Nebulized Colistin in Ventilator-Associated Pneumonia and Tracheobronchitis: Historical Background, Pharmacokinetics and Perspectives

Clinical evidence suggests that nebulized colistimethate sodium (CMS) has benefits for treating lower respiratory tract infections caused by multidrug-resistant Gram-negative bacteria (GNB). Colistin is positively charged, while CMS is negatively charged, and both have a high molecular mass and are hydrophilic. These physico-chemical characteristics impair crossing of the alveolo-capillary membrane but enable the disruption of the bacterial wall of GNB and the aggregation of the circulating lipopolysaccharide. Intravenous CMS is rapidly cleared by glomerular filtration and tubular excretion, and 20-25% is spontaneously hydrolyzed to colistin. Urine colistin is substantially reabsorbed by tubular cells and eliminated by biliary excretion. Colistin is a concentration-dependent antibiotic with post-antibiotic and inoculum effects. As CMS conversion to colistin is slower than its renal clearance, intravenous administration can lead to low plasma and lung colistin concentrations that risk treatment failure. Following nebulization of high doses, colistin (200,000 international units/24h) lung tissue concentrations are > five times minimum inhibitory concentration (MIC) of GNB in regions with multiple foci of bronchopneumonia and in the range of MIC breakpoints in regions with confluent pneumonia. Future research should include: (1) experimental studies using lung microdialysis to assess the PK/PD in the interstitial fluid of the lung following nebulization of high doses of colistin; (2) superiority multicenter randomized controlled trials comparing nebulized and intravenous CMS in patients with pandrug-resistant GNB ventilator-associated pneumonia and ventilator-associated tracheobronchitis; (3) non-inferiority multicenter randomized controlled trials comparing nebulized CMS to intravenous new cephalosporines/ß-lactamase inhibitors in patients with extensive drug-resistant GNB ventilator-associated pneumonia and ventilator-associated tracheobronchitis.

A Breath of Fresh Air in the Fog of Antimicrobial Resistance: Inhaled Polymyxins for Gram-Negative Pneumonia

Despite advancements in therapy, pneumonia remains the leading cause of death due to infectious diseases. Novel treatment strategies are desperately needed to optimize the antimicrobial therapy of patients suffering from this disease. One such strategy that has recently garnered significant attention is the use of inhaled antibiotics to rapidly achieve therapeutic concentrations directly at the site of infection. In particular, there is significant interest in the role of inhaled polymyxins for the treatment of nosocomial pneumonia, including ventilator-associated pneumonia, due to their retained activity against multi-drug resistant Gram-negative pathogens, including Acinetobacter baumannii and Pseudomonas aeruginosa. This review will provide a comprehensive overview of the pharmacokinetic/pharmacodynamic profile, clinical outcomes, safety, and potential role of inhaled polymyxins in clinical practice.

Effect of antibiotics administered via the respiratory tract in the prevention of ventilator-associated pneumonia: A systematic review and meta-analysis

PURPOSE

We evaluated the effect of antibiotics administered via the respiratory tract to prevent the ventilator-associated pneumonia (VAP) in mechanically ventilated (MV) patients.

METHODS

We searched relevant articles for trials that evaluated the impact of prophylactic antibiotics administered through the respiratory tract on the occurrence of VAP. The end-point was the occurrence of VAP in MV patients.

RESULTS

We included 6 comparative trials involving 1158 patients (632 received prophylactic antibiotic). Our meta-analysis revealed that prophylactic antibiotics administered through the respiratory tract reduced the occurrence of VAP when compared to placebo or no treatment (OR 0.53; 95% CI 0.34-0.84). This effect was seen when the antibiotics were given by nebulization (OR 0.46; 95% CI 0.22-0.97), but not when they were administered by intratracheal instillation (OR 0.57; 95% CI 0.28-1.15). We did not find a significant difference between the compared groups in the intensive care unit (ICU) mortality (OR 0.89; 95% CI 0.64-1.25). Antibiotic prophylaxis did not impact occurrence of VAP due to multidrug resistant (MDR) pathogens (OR 0.67; 95% CI 0.17-2.62).

CONCLUSIONS

Prophylactic antibiotics administered through the respiratory tract by nebulization reduce the occurrence of VAP, without a significant effect on either the ICU mortality or occurrence of VAP due to MDR pathogens.

Nebulization of Antiinfective Agents in Invasively Mechanically Ventilated Adults: A Systematic Review and Meta-analysis

BACKGROUND

Nebulization of antiinfective agents is a common but unstandardized practice in critically ill patients.

METHODS

A systematic review of 1,435 studies was performed in adults receiving invasive mechanical ventilation. Two different administration strategies (adjunctive and substitute) were considered clinically relevant. Inclusion was restricted to studies using jet, ultrasonic, and vibrating-mesh nebulizers. Studies involving children, colonized-but-not-infected adults, and cystic fibrosis patients were excluded.

RESULTS

Five of the 11 studies included had a small sample size (fewer than 50 patients), and only 6 were randomized. Diversity of case-mix, dosage, and devices are sources of bias. Only a few patients had severe hypoxemia. Aminoglycosides and colistin were the most common antibiotics, being safe regarding nephrotoxicity and neurotoxicity, but increased respiratory complications in 9% (95% CI, 0.01 to 0.18; I = 52%), particularly when administered to hypoxemic patients. For tracheobronchitis, a significant decrease in emergence of resistance was evidenced (risk ratio, 0.18; 95% CI, 0.05 to 0.64; I = 0%). Similar findings were observed in pneumonia by susceptible pathogens, without improvement in mortality or ventilation duration. In pneumonia caused by resistant pathogens, higher clinical resolution (odds ratio, 1.96; 95% CI, 1.30 to 2.96; I = 0%) was evidenced. These findings were not consistently evidenced in the assessment of efficacy against pneumonia caused by susceptible pathogens.

CONCLUSIONS

Performance of randomized trials evaluating the impact of nebulized antibiotics with more homogeneous populations, standardized drug delivery, predetermined clinical efficacy, and safety outcomes is urgently required. Infections by resistant pathogens might potentially have higher benefit from nebulized antiinfective agents. Nebulization, without concomitant systemic administration of the drug, may reduce nephrotoxicity but may also be associated with higher risk of respiratory complications.

Inhaled Antibiotics for Gram-Negative Respiratory Infections

Gram-negative organisms comprise a large portion of the pathogens responsible for lower respiratory tract infections, especially those that are nosocomially acquired, and the rate of antibiotic resistance among these organisms continues to rise. Systemically administered antibiotics used to treat these infections often have poor penetration into the lung parenchyma and narrow therapeutic windows between efficacy and toxicity. The use of inhaled antibiotics allows for maximization of target site concentrations and optimization of pharmacokinetic/pharmacodynamic indices while minimizing systemic exposure and toxicity. This review is a comprehensive discussion of formulation and drug delivery aspects, in vitro and microbiological considerations, pharmacokinetics, and clinical outcomes with inhaled antibiotics as they apply to disease states other than cystic fibrosis. In reviewing the literature surrounding the use of inhaled antibiotics, we also highlight the complexities related to this route of administration and the shortcomings in the available evidence. The lack of novel anti-Gram-negative antibiotics in the developmental pipeline will encourage the innovative use of our existing agents, and the inhaled route is one that deserves to be further studied and adopted in the clinical arena.

Nebulised colistin for ventilator-associated pneumonia prevention

We evaluated whether prophylactic nebulised colistin could reduce ventilator-associated pneumonia (VAP) rates in an intensive care unit (ICU) setting with prevalent multidrug-resistant (MDR) bacteria.

We used a single-centre, two-arm, randomised, open-label, controlled trial in a 12-bed ICU in the University Hospital of Larissa, Greece. Patient inclusion criteria included mechanical ventilation of >48 h. The two arms consisted of prophylaxis with 500 000 U colistin (Col group) or normal saline (NS group), thrice daily, for the first 10 ICU days or until extubation. The primary outcome of the study was the 30-day VAP incidence.

In total, 168 patients entered the study. VAP incidence was not different between Col and NS group patients (14 (16.7%)versus25 (29.8%), respectively, p=0.07). Regarding the secondary outcomes, the intervention resulted in a lower VAP incidence density rate (11.4versus25.6, respectively, p<0.01), and less Gram-negative bacteria-VAP (p=0.03) and MDR-VAP (p=0.04). Among VAP patients (n=39), prophylaxis with inhaled colistin improved ICU survival (p=0.016). There was no evidence of increased resistance to colistin or multidrug resistance.

Our findings suggest that nebulised colistin had no significant effect on VAP incidence.

Role of inhaled antibacterials in hospital-acquired and ventilator-associated pneumonia

Inhaled antibiotics are not usually considered outside the setting of cystic fibrosis or Pneumocystis jiroveci prophylaxis. However, because they deliver high drug concentrations at the site of infection with negligible systemic absorption and toxicity, they are logical compliments to standard intravenous therapy for severe nosocomial pneumonias -- particularly those caused by multiresistant organisms. Older studies that have shown marginal or no benefit have either applied inhaled antibiotics indiscriminately to low risk populations, or have used crude delivery systems, such as hand atomizers or poured it into the endotracheal tube. Although inhaled antibiotics cannot be recommended for prevention of nosocomial pneumonia at this time, a few studies involving prophylaxis have shown promising trends, particularly in high-risk patients with predisposing conditions. The greatest potential of inhaled antibiotics lies in the treatment of severe healthcare-associated pneumonia caused by a multiresistant organism. The method of delivery is extremely important. Trials that have shown the most benefit, even against pathogens most difficult to eradicate and in damaged lungs, have used optimized delivery systems. Most authorities recommend using ultrasonic or vibrating disk nebulizers to generate particle sizes between 1 and 5 microm that are crucial for deposition in terminal bronchioles and alveoli. Inhaled liposomal amphotericin has also demonstrated encouraging results in animal trials. Recently, inhaled phytochemicals were successfully employed in the treatment of a patient with primary pulmonary tuberculosis. When used selectively in high-risk patients, or in the treatment of established pneumonia, inhaled antibiotics have not been associated with development of resistant organisms.

Aerosolized antibiotics in the intensive care unit

This review summarizes recent clinical data examining the use of aerosolized antimicrobial therapy for the treatment of respiratory tract infections in mechanically ventilated patients in the intensive care unit. Aerosolized antibiotics provide high concentrations of drug in the lung without the systemic toxicity associated with the intravenous antibiotics. First introduced in the 1960s as a treatment of tracheobronchitis and bronchopneumonia caused by Pseudomonas aeruginosa, now, more than 40 years later, there is a resurgence of interest in using this mode of delivery as a primary therapy for ventilator-associated tracheobronchitis and an adjunctive therapy for ventilator-associated pneumonia.

Comparative evaluation of intratracheal colistimethate sodium, imipenem, and meropenem in BALB/c mice with carbapenem-resistant Acinetobacter baumannii pneumonia

OBJECTIVE

The identification of the optimal agent for administration via the respiratory tract when treating pneumonia caused by carbapenem-resistant Acinetobacter baumannii (CRAB).

METHODS

A murine model of acute CRAB pneumonia was established by intratracheal (i.t.) inoculation with 2.5 × 10⁷ colony-forming units (CFU) of A. baumannii strain Ab396 plus 10% porcine mucin. After 4h the infected BALB/c mice were treated intratracheally with 25μl of either 0.85% saline (control group), colistimethate sodium (CMS) (166 666 U/kg, CMS group), imipenem/cilastatin (30/30 mg/kg, imipenem group), or meropenem (20mg/kg, meropenem group), every 8h. The therapeutic efficacy of these agents was examined.

RESULTS

A. baumannii strain Ab396 was susceptible to CMS only. However, meropenem treatment did give a significantly superior survival rate (100%) compared to treatment with imipenem (50%), CMS (33%), or saline (0%) (p<0.001 vs. the control and CMS groups, p=0.006 vs. the imipenem group, by log-rank test). Furthermore, compared to the other groups, the meropenem group demonstrated significantly more favorable results in terms of tissue penetration of the antibiotic, bacterial clearance, normalization of the wet lung-to-body weight ratio, and down-regulation of pro-inflammatory cytokine levels in the lungs.

CONCLUSIONS

Administration of meropenem via the respiratory tract proved to have the best therapeutic efficacy among the antibiotics tested when treating advanced murine CRAB pneumonia.

Prevention of ventilator-associated pneumonia, mortality and all intensive care unit acquired infections by topically applied antimicrobial or antiseptic agents: a meta-analysis of randomized controlled trials in intensive care units

INTRODUCTION

Given the high morbidity and mortality attributable to ventilator-associated pneumonia (VAP) in intensive care unit (ICU) patients, prevention plays a key role in the management of patients undergoing mechanical ventilation. One of the candidate preventive interventions is the selective decontamination of the digestive or respiratory tract (SDRD) by topical antiseptic or antimicrobial agents. We performed a meta-analysis to investigate the effect of topical digestive or respiratory tract decontamination with antiseptics or antibiotics in the prevention of VAP, of mortality and of all ICU-acquired infections in mechanically ventilated ICU patients.

METHODS

A meta-analysis of randomised controlled trials was performed. The U.S. National Library of Medicine's MEDLINE database, Embase, and Cochrane Library computerized bibliographic databases, and reference lists of selected studies were used. Selection criteria for inclusion were: randomised controlled trials (RCTs); primary studies; examining the reduction of VAP and/or mortality and/or all ICU-acquired infections in ICU patients by prophylactic use of one or more of following topical treatments: 1) oropharyngeal decontamination using antiseptics or antibiotics, 2) gastrointestinal tract decontamination using antibiotics, 3) oropharyngeal plus gastrointestinal tract decontamination using antibiotics and 4) respiratory tract decontamination using antibiotics; reported enough data to estimate the odds ratio (OR) or risk ratio (RR) and their variance; English language; published through June 2010.

RESULTS

A total of 28 articles met all inclusion criteria and were included in the meta-analysis. The overall estimate of efficacy of topical SDRD in the prevention of VAP was 27% (95% CI of efficacy = 16% to 37%) for antiseptics and 36% (95% CI of efficacy = 18% to 50%) for antibiotics, whereas in none of the meta-analyses conducted on mortality was a significant effect found. The effect of topical SDRD in the prevention of all ICU-acquired infections was statistically significant (efficacy = 29%; 95% CI of efficacy = 14% to 41%) for antibiotics whereas the use of antiseptics did not show a significant beneficial effect.

CONCLUSIONS

Topical SDRD using antiseptics or antimicrobial agents is effective in reducing the frequency of VAP in ICU. Unlike antiseptics, the use of topical antibiotics seems to be effective also in preventing all ICU-acquired infections, while the effectiveness on mortality of these two approaches needs to be investigated in further research.

Delivery of antibiotics to the respiratory tract: an update

The use of inhaled medications for the treatment of pulmonary diseases has become an increasingly popular drug delivery route over the past few decades. This delivery route allows for a drug to be delivered directly to the site of the disease, with a lower dose than more conventional oral or intravenous delivery methods, with reduced systemic absorption and consequently reduced risk of adverse effects. For asthma this delivery route has become the 'golden standard' of therapy. It is not unexpected therefore, that there has been great interest in the prospect of using inhaled antibiotics for the treatment of both chronic and recurrent respiratory infections. Since the early 1980s, several investigations have demonstrated that antibiotics could be delivered safely by means of inhalation, using nebulisers as their delivery systems. Lately, antibiotics delivery via inhalation have seen a 'revival' in interest and most of these studies have focused on delivering antibiotics to the lungs by means of a dry powder format. This review focuses on recent advances in antibiotic inhalation therapy.

Intratracheal colistin sulfate for BALB/c mice with early pneumonia caused by carbapenem-resistant Acinetobacter baumannii

OBJECTIVES

: To study the efficacy of intratracheal colistin sulfate therapy in a murine model of acute pneumonia caused by a clinical CRAB strain, Ab396. Colistin therapy has currently achieved a favorable outcome in patients with carbapenem-resistant Acinetobacter baumannii (CRAB) infections, but parenteral colistin may have limited therapeutic efficacy for CRAB pneumonia.

DESIGN

: A controlled, in vivo experimental study.

SETTING

: Research laboratory of a medical center.

SUBJECTS

: Female BALB/c mice.

INTERVENTIONS

: The minimal inhibitory concentrations of antibiotics were measured. Acute pneumonia was established by intratracheal inoculation with an inoculum size of 2.5 x 10 colony-forming units Ab396 plus 10% porcine mucin into the lungs of mice, verified by histopathological examinations, and then treated with or without antibiotics. Mice received intratracheal saline treatment as a control group, intraperitoneal administration (IP) imipenem/cilastatin plus sulbactam (IP IS group, 80/80 mg/kg and 40 mg/kg every 8 hrs, n = 30), IP colistin sulfate (IP CS group, 150,000 U/kg every 8 hrs, n = 30), and intratracheal colistin sulfate (intratracheal CS group, 75,000 U/kg every 8 hrs, n = 30) at 2 hrs after intratracheal inoculation of Ab396.

MEASUREMENTS AND MAIN RESULTS

: The minimal inhibitory concentrations of colistin sulfate, imipenem/cilastatin, or sulbactam for Ab396 were 2 microg/mL, 128 microg/mL, or 32 microg/mL, respectively. Compared with the mice in the control, IP IS, and IP CS groups, those in intratracheal CS group had a significantly favorable outcome at 72 hrs after infection (survival rate = 0%, 10%, 0% and 100%, respectively; all p < .001, log-rank test). Furthermore, intratracheal therapy decreased significantly the bacterial loads in the lungs and normalized the wet lung/body weight ratios in mice with acute pneumonia.

CONCLUSIONS

: The intratracheal colistin sulfate therapy led to more favorable outcomes than therapies by IP colistin sulfate or imipenem/cilastatin plus sulbactam in mice with early CRAB pneumonia.

The impact of a simple, low-cost oral care protocol on ventilator-associated pneumonia rates in a surgical intensive care unit

OBJECTIVE

The purpose of this study was to determine the effects of a simple low-cost oral care protocol on ventilator-associated pneumonia rates in a surgical intensive care unit.

DESIGN

Preintervention and postintervention observational study.

SETTING

Twenty-four bed surgical/trauma/burn intensive care units in an urban university hospital.

PATIENTS

All mechanically ventilated patients that were admitted to the intensive care unit between June 1, 2004 and May 31, 2005.

INTERVENTIONS

An oral care protocol to assist in prevention of bacterial growth of plaque by cleaning the patients' teeth with sodium monoflurophosphate 0.7% paste and brush, rinsing with tap water, and subsequent application of a 0.12% chlorhexidine gluconate chemical solution done twice daily at 12-hour intervals.

MEASUREMENTS AND MAIN RESULTS

During the preintervention period from June 1, 2003 to May 31, 2004, there were 24 infections in 4606 ventilator days (rate = 5.2 infections per 1000 ventilator days). After the institution of the oral care protocol, there were 10 infections in 4158 ventilator days, resulting in a lower rate of 2.4 infections per 1000 ventilator days. This 46% reduction in ventilator-associated pneumonia was statistically significant (P = .04). Staff compliance with the oral care protocol during the 12-month period was also monitored biweekly and averaged 81%. The total cost of the oral care protocol was US$2187.49. There were 14 fewer cases of ventilator-associated pneumonia, which led to a decrease in cost of US$140 000 to US$560 000 based on the estimated cost per ventilator-associated pneumonia infection of US$10 000 to US$40 000. There was an overall reduction in ventilator-associated pneumonia without a change to the gram-negative or gram-positive microorganism profile.

CONCLUSIONS

The implementation of a simple, low-cost oral care protocol in the surgical intensive care unit led to a significantly decreased risk of acquiring ventilator-associated pneumonia.

Aerosolized antibiotics and ventilator-associated tracheobronchitis in the intensive care unit

CONTEXT

In critically ill intubated patients, signs of respiratory infection often persist despite treatment with potent systemic antibiotics.

OBJECTIVE

The purpose of this study was to determine whether aerosolized antibiotics, which achieve high drug concentrations in the target organ, would more effectively treat respiratory infection and decrease the need for systemic antibiotics.

DESIGN

Double-blind, randomized, placebo-controlled study performed from 2003 through 2004.

SETTING

The medical and surgical intensive care units of a university hospital.

PATIENTS

Critically ill intubated patients were randomized if: 1) > or = 18 yrs of age, intubated for a minimum of 3 days, and expected to survive at least 14 days; and 2) had ventilator-associated tracheobronchitis defined as the production of purulent secretions (> or = 2 mL during 4 hrs) with organism(s) on Gram stain. Of 104 patients monitored, 43 consented for treatment and completed the study. No patients were withdrawn from the study for adverse events.

INTERVENTION

Aerosol antibiotic (AA) or aerosol saline placebo was given for 14 days or until extubation. The responsible clinician determined the administration of systemic antibiotics (SA). Patients were followed for 28 days.

MAIN OUTCOME MEASURES

Primary: Centers for Disease Control National Nosocomial Infection Survey diagnostic criteria for ventilator-associated pneumonia (VAP) and clinical pulmonary infection score. Secondary: white blood cell count, SA use, acquired antibiotic resistance, and weaning from mechanical ventilation.

RESULTS

Most patients had VAP at randomization. With treatment, the AA group had reduced signs of respiratory infection: reduced Centers for Disease Control National Nosocomial Infection Survey VAP (14/19; 73.6%) to (5/14; 35.7%) vs. placebo (18/24; 75%) to (11/14; 78.6%), reduction in clinical pulmonary infection score, lower white blood cell count at day 14, reduced bacterial resistance, reduced use of SA, and increased weaning (all p < or = .05).

CONCLUSIONS

In critically ill patients with ventilator-associated tracheobronchitis, AA decrease VAP and other signs and symptoms of respiratory infection, facilitate weaning, and reduce bacterial resistance and use of systemic antibiotics.

Aerosolized ceftazidime prophylaxis against ventilator-associated pneumonia in high-risk trauma patients: results of a double-blind randomized study

BACKGROUND

Ventilator-associated pneumonia (VAP) is a frequent complication during recovery of severely traumatized patients. The primary objective of this study was to determine if prophylactic administration of aerosolized ceftazidime reduced the incidence of VAP in high-risk injured patients without altering the incidence of other infectious complications.

PATIENTS AND METHODS

This was a single-institution double-blind, randomized trial that compared a seven-day course of aerosolized ceftazidime with placebo. Intubated high-risk patients admitted to the trauma intensive care unit at a large regional trauma center between February 2003 and September 2005 were eligible for enrollment. The main outcome evaluated was the incidence of VAP at two weeks and 30 days. The incidences of multi-drug-resistant infections and other infectious complications were secondary outcomes.

RESULTS

A total of 105 patients were randomized, resulting in 52 patients in the placebo arm and 53 patients in the ceftazidime arm. There was no statistical difference between the groups with regard to demographic data, injury severity, calculated risk of VAP, or the number of doses received. In the intention-to-treat analysis, the incidence of VAP at two weeks was 24/52 (46%) in the placebo group and 21/53 (40%) in the ceftazidime group. The number of patients with VAP at 30 days was 26/52 (50%) in the placebo group and 26/53 (49%) in the ceftazidime group. There was no statistical difference in the development of multi-drug-resistant VAP or other infectious complications in the two groups.

CONCLUSION

The use of aerosolized ceftazidime did not reduce the rate of VAP in high-risk patients admitted after traumatic injury, but neither did it increase the incidence of other infectious complications. Routine use of prophylactic aerosolized ceftazidime to prevent VAP in trauma patients cannot be recommended.

Aerosolised Antibacterials for the Prevention and Treatment of Hospital-Acquired Pneumonia

Aerosolised administration of antibacterials remains theoretically attractive for the prevention and treatment of hospital-acquired pneumonia (HAP) because of the ability to generate high drug concentrations at the site of infection. There is renewed interest in this area because of the shortcomings of current therapies and increasing multidrug resistance in Gram-negative organisms. Clinical trials of aerosolised or endotracheally administered antibacterials for HAP prevention have generally been positive; however, early trials were hampered by the development of resistance related to indiscriminate use. More recent trials have shown efficacy at HAP prevention without adverse effects on microflora as a result of more limited usage. However, prophylactic aerosolised antibacterials still need to be studied in large randomised trials before they could enter widespread use. The treatment of HAP with aerosolised antibacterials has mostly been reported in case series without control groups. Both early reports with aminoglycosides and the more recent use of colistin have reported very good response rates; even with organisms such as Pseudomonas aeruginosa and Acinetobacter baumannii. Aerosolised antibacterials were almost always added to intravenous therapy. On the basis of these reports, the current HAP guidelines allow the addition of aerosolised antibacterials in selected patients with multidrug-resistant organisms. This seems to be a reasonable recommendation until large trials are performed. Overall, toxicity was relatively low in the publications reviewed. Aerosolised drug administration in mechanically ventilated patients requires attention to a number of factors in order to maximise drug deposition in the lung.

Administration of antibiotics via the respiratory tract for the prevention of ICU-acquired pneumonia: a meta-analysis of comparative trials

Introduction

The administration of prophylactic antibiotics via the respiratory tract is one of several strategies for the prevention of intensive care unit (ICU)-acquired pneumonia. We systematically examined the available evidence regarding the effect of prophylactic antibiotics administered via the respiratory tract on the development of ICU-acquired pneumonia, mortality, colonization of the respiratory tract, emergence of antimicrobial resistance, and toxicity.

Methods

We searched the PubMed database (January 1950 to September 2005) and references from relevant articles to identify trials that provided comparative data regarding the above-mentioned outcomes. Two investigators independently performed the data extraction to calculate the effect of the studied intervention on clinically relevant outcomes.

Results

Our meta-analysis includes 8 comparative trials (5 randomized controlled trials (RCTs) and 3 non-randomized trials) studying gentamicin (3 trials), polymyxins (3 trials), tobramycin (1 trial), and ceftazidime (1 trial) that studied 1,877 patients. Our primary analysis, which included the 5 RCTs, revealed that ICU-acquired pneumonia was less common in the group of patients that received the antibiotic prophylaxis (odds ratio (OR) = 0.49, 95% confidence interval (CI) 0.32–0.76). No difference in mortality was found between the compared groups (OR = 0.86, 95% CI 0.55–1.32). Data were too limited to permit an analysis of colonization with Pseudomonas aeruginosa. A secondary analysis, adding the three non-randomized comparative trials, did not reveal substantially different results regarding ICU-acquired pneumonia and mortality, while fewer patients were colonized with P. aeruginosa in the group that received prophylaxis, compared to the group of patients that received no prophylaxis (OR = 0.51, 95% CI 0.30–0.86). No serious drug-related toxicity was noted. No meaningful systematic analysis of the evidence regarding the emergence of resistance could be performed in the studies included in our meta-analysis.

Conclusion

The limited available evidence supports that prophylactic administration of antibiotics via the respiratory tract is associated with reduction of occurrence of ICU-acquired pneumonia. However, there is evidence from non-comparative studies that this preventive strategy may lead to an increase in the emergence of resistant bacteria. Thus, further investigation, at least in ICU patients at high risk for development of ICU-acquired pneumonia, is warranted, including a more systematic evaluation of issues related to the emergence of resistance.

Hospital-acquired pneumonia in the 21st century: a review of existing treatment options and their impact on patient care

Hospital-acquired pneumonia is a common nosocomial infection, with significant morbidity and mortality, and represents a major therapeutic challenge to clinicians. The therapeutic approach must be patient-oriented and institution-specific. The specific risk factors of each patient, such as previous antibiotic exposure, underlying diseases, length of hospital stay and the local patterns of antimicrobial resistance, should guide physicians in their decision of the initial optimal empirical therapy. Delays in the initiation or inappropriate/inadequate initial therapy are related to increased mortality and worse outcomes. In responding patients, as soon as culture data are available, efforts should be made to change the initial broad spectrum antibiotic regimen to a more targeted one (de-escalation). The optimal duration of treatment is a matter of debate, but courses longer than 1 week are rarely justified.

Lung deposition and efficiency of nebulized amikacin during Escherichia coli pneumonia in ventilated piglets

Lung tissue deposition and antibacterial efficiency of nebulized and intravenous amikacin (AMK) were compared in anesthetized and ventilated piglets suffering from a bronchopneumonia produced by the intrabronchial inoculation of Escherichia coli. AMK was administered 24 hours after the inoculation either through an ultrasonic nebulizer (45 mg x kg-1, n = 10) or by intravenous infusion (15 mg x kg-1, n = 8). Piglets were killed 1 hour after a second AMK administration performed 24 hours after the first one, and lung tissue concentrations of AMK and lung bacterial burden were assessed on multiple lung specimens. The amount of nebulized AMK reaching the tracheobronchial tree represented 38 +/- 6% of the initial nebulizer AMK charge. After nebulization, AMK lung tissue concentrations were 3- to 30-fold higher than after intravenous administration and were influenced by the severity of lung lesions: 188 +/- 175 microg x g-1 in lung segments with mild bronchopneumonia versus 40 +/- 65 microg x g-1 in lung segments with severe bronchopneumonia (p < 0.01). Lung bacterial burden was significantly lower in the aerosol group than in the intravenous group (median = 0 colony forming units. g-1 versus median = 5 x 10(2) colony forming units x g-1, p < 0.001). In conclusion, the deposition of AMK in infected lung parenchyma and the efficiency of bacterial killing were greater after nebulization than after intravenous administration.

Aerosolized ceftazidime for prevention of ventilator-associated pneumonia and drug effects on the proinflammatory response in critically ill trauma patients

STUDY OBJECTIVES

To evaluate the safety and efficacy of aerosolized ceftazidime for prevention of ventilator-associated pneumonia (VAP) and to evaluate the effects of the drug on the proinflammatory response.

DESIGN

Prospective, randomized, double-blind, placebo-controlled clinical trial.

SETTING

University teaching hospital.

PATIENTS

Forty critically ill trauma patients at high risk for VAP Intervention. Within 48 hours of admission to the intensive care unit (ICU), patients were randomly assigned to receive aerosolized ceftazidime 250 mg every 12 hours or placebo (normal saline) for up to 7 days. Bronchoalveolar concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, and IL-8 were determined at baseline and the end of therapy (days 4-7).

MEASUREMENTS AND MAIN RESULTS

The frequency of VAP in patients receiving aerosolized ceftazidime was 73% lower than that in patients receiving placebo at ICU day 14 (15% vs 55%, p = 0.021), and 54% lower for the entire ICU stay (30% vs 65%, p = 0.022). No clinically significant changes in bacterial culture and sensitivity patterns were observed. No adverse events from aerosolized ceftazidime were reported. Pulmonary TNF-alpha, IL-beta, and IL-8 concentrations were attenuated in the ceftazidime group compared with those in the placebo group (p < 0.001, p = 0.02, and p = 0.003). The frequency of VAP was related directly to changes in TNF-alpha and IL-beta (p < 0.001, p = 0.02).

CONCLUSIONS

Aerosolized ceftazidime decreased the frequency of VAP in critically ill trauma patients, without adversely affecting ICU flora. Aerosolized ceftazidime also may attenuate the proinflammatory response in the lung.

Lung tissue concentrations of nebulized amikacin during mechanical ventilation in piglets with healthy lungs

The tissue concentration of aminoglycosides in lung parenchyma is the main determinant of bactericidal efficiency. The aim of the study was to compare the lung deposition of amikacin administered either by an ultrasonic nebulizer or by intravenous infusion during mechanical ventilation. Eighteen healthy ventilated piglets received a single daily dose of amikacin by intravenous infusion (15 mg. kg(-1)) and 18 by aerosol (1 g in 12 ml). The amount of aerosolized amikacin reaching the tracheobronchial tree represented 40 +/- 5% of the initial dose with an aerodynamic size distribution showing 50% of particles ranging between 0.5 and 5 microm mass median diameter. Animals were killed at different time intervals after the second dose. Tissue concentrations of amikacin were determined on cryomixed multiple lung specimen by an immunoenzymatic method. The lung concentrations of nebulized amikacin, peaking at 208 +/- 76 microg. g(-1), were more than 10-fold higher than the lung concentrations of intravenous amikacin and were homogeneously distributed throughout the lung parenchyma. Amikacin plasma concentrations lower than 5 mmol. l(-1) were measured after the sixth hour after the nebulization. In conclusion, the ultrasonic nebulization of amikacin resulted in high tissue concentrations, far above the minimal inhibitory concentrations of most gram-negative strains.

Aerosolized antimicrobial therapy in acutely ill patients

Recent data are sparking renewed interest in therapy with aerosolized antimicrobials in critically ill patients as well as other populations such as those with neutropenia, human immunodeficiency virus infection, and cystic fibrosis. Pneumonia is a common complication in these patients and is associated with substantial morbidity and increased mortality. Clinical trials evaluated aerosolized antimicrobials for the prevention and treatment of pneumonia in hospitalized patients. In addition, factors that affect the pulmonary deposition of aerosolized drugs in mechanically ventilated patients were identified.

Expiratory washout versus optimization of mechanical ventilation during permissive hypercapnia in patients with severe acute respiratory distress syndrome

The aim of this study was to compare three ventilatory techniques for reducing PaCO2 in patients with severe acute respiratory distress syndrome treated with permissive hypercapnia: (1) expiratory washout alone at a flow of 15 L/min, (2) optimized mechanical ventilation defined as an increase in the respiratory frequency to the maximal rate possible without development of intrinsic positive end- expiratory pressure (PEEP) combined with a reduction of the instrumental dead space, and (3) the combination of both methods. Tidal volume was set according to the pressure-volume curve in order to obtain an inspiratory plateau airway pressure equal to the upper inflection point minus 2 cm H2O after setting the PEEP at 2 cm H2O above the lower inflection point and was kept constant throughout the study. The three modalities were compared at the same inspiratory plateau airway pressure through an adjustment of the extrinsic PEEP. During conventional mechanical ventilation using a respiratory frequency of 18 breaths/min, respiratory acidosis (PaCO2 = 84 +/- 24 mm Hg and pH = 7.21 +/- 0.12) was observed. Expiratory washout and optimized mechanical ventilation (respiratory frequency of 30 +/- 4 breaths/min) had similar effects on CO2 elimination (DeltaPaCO2 = -28 +/- 11% versus -27 +/- 12%). A further decrease in PaCO2 was observed when both methods were combined (DeltaPaCO2 = -46 +/- 7%). Extrinsic PEEP had to be reduced by 5.3 +/- 2.1 cm H2O during expiratory washout and by 7.3 +/- 1.3 cm H2O during the combination of the two modes, whereas it remained unchanged during optimized mechanical ventilation alone. In conclusion, increasing respiratory rate and reducing instrumental dead space during conventional mechanical ventilation is as efficient as expiratory washout to reduce PaCO2 in patients with severe ARDS and permissive hypercapnia. When used in combination, both techniques have additive effects and result in PaCO2 levels close to normal values.

Intravenous almitrine combined with inhaled nitric oxide for acute respiratory distress syndrome. The NO Almitrine Study Group

Inhaled nitric oxide (iNO), a selective pulmonary vasodilator and intravenously administered almitrine, a selective pulmonary vasoconstrictor, have been shown to increase PaO2 in patients with acute respiratory distress syndrome (ARDS). This prospective study was undertaken to assess the cardiopulmonary effects of combining both drugs. In 48 consecutive patients with early ARDS, cardiorespiratory parameters were measured at control, after iNO 5 ppm, after almitrine 4 micrograms. kg-1. min-1, and after the combination of both drugs. In 30 patients, dose response to 2, 4, and 16 micrograms. kg-1. min-1 of almitrine with and without NO was determined. Almitrine and lactate plasma concentrations were measured in 17 patients. Using pure O2, PaO2 increased by 75 +/- 8 mm Hg after iNO, by 101 +/- 12 mm Hg after almitrine 4 micrograms. kg-1. min-1, and by 175 +/- 18 mm Hg after almitrine combined with iNO (p < 0.001). In 63% of the patients, PaO2 increased by more than 100% with the combination of both drugs. Mean pulmonary artery pressure (Ppa) increased by 1.4 +/- 0.2 mm Hg with almitrine 4 micrograms/kg/ min (p < 0.001) and decreased by 3.4 +/- 0.4 mm Hg with iNO and by 1.5 +/- 0.3 mm Hg with the combination (p < 0.001). The maximum increase in PaO2 was obtained at almitrine concentrations <= 4 micrograms. kg-1. min-1, whereas almitrine increased Ppa dose-dependently. Almitrine plasma concentrations also increased dose-dependently and returned to values close to zero after 12 h. In many patients with early ARDS, the combination of iNO 5 ppm and almitrine 4 micrograms. kg-1. min-1 dramatically increases PaO2 without apparent deleterious effect allowing a rapid reduction in inspired fraction of O2. The long-term consequences of this immediate beneficial effect remain to be determined.

Risks and routes for ventilator-associated pneumonia with Pseudomonas aeruginosa

In a prospective study, we screened specimens from 190 mechanically ventilated patients hospitalized in a surgical intensive care unit, and from the environment to assess risks and routes of colonization/infection. Specimens from various sites were collected on admission and once a week throughout each patient's stay. All P. aeruginosa isolates were typed by determination of DNA patterns. Data were collected from patients to identify risk factors. In vitro production of exoenzymes of different strains were compared. Forty-four patients were colonized with P. aeruginosa on the bronchopulmonary tract and 13 suffered from pneumonia. The 7-d and 14-d Kaplan-Meier rates of colonization were 2.21 and 7.03%. Twenty-one patterns of bronchopulmonary tract isolates were isolated from single patients and 10 from several patients. The lower airway was often the first site of colonization. The contribution of environment to patient colonization appeared to be small. The length of hospitalization, the previous use of third-generation cephalosporins less effective against P. aeruginosa, and chronic obstructive pulmonary disease were the most significant predictors of colonization/infection. The in vitro exoprotein production was not correlated with the presence of pneumonia. Our study may be useful in identifying which patients in the mechanically ventilated population are at greater risk of P. aeruginosa pneumonia.

Use of aerosolized colistin sodium in cystic fibrosis patients awaiting lung transplantation

BACKGROUND

In patients with cystic fibrosis (CF) who are awaiting lung transplant, prolonged exposure to systemic antibiotics has frequently led to airway colonization with resistant isolates of Pseudomonas. This resistance limits the arsenal of effective antimicrobials available for infections after the initiation of immunosuppression and has been considered a theoretical deterrent to lung transplantation.

METHODS

Twenty CF transplant candidates with "pan-resistant" Pseudomonas received maintenance antibiotic therapy with aerosolized colistin sodium (75 mg b.i.d.), and intravenous antibiotics were eliminated. Ten other CF candidates did not use colistin sodium. Sputum cultures and antibiotic sensitivities were followed every 3-6 weeks.

RESULTS

All 20 candidates (100%) who used aerosolized colistin sodium became colonized with sensitive isolates of Pseudomonas in an average of 45.1+/-20.2 days. In contrast, only 3 of 10 CF transplant candidates (30%) who did not use colistin sodium later became colonized with sensitive isolates. The mean time to spontaneous emergence of sensitive organisms was 144.6+/-48.0 days in candidates who did not use colistin sodium and was significantly longer than in the candidates who used colistin sodium (P=0.007). The occurrence of redeveloping sensitive isolates of Pseudomonas was significantly greater in the candidates who used colistin sodium (P<0.05). Of the candidates who used colistin sodium, six have been transplanted at our institution. In five of these six recipients (83.3%) bacterial cultures taken from the explanted lungs continued to demonstrate sensitive organisms.

CONCLUSION

Aerosolized colistin sodium may be a useful therapy to promote emergence of sensitive microbes in CF candidates with pan-resistant isolates of Pseudomonas.