Antimicrobial therapy in pulmonary aspiration

Acute Respiratory Failure in Pregnancy

Acute respiratory failure in pregnancy has multiple etiologies, including thromboembolism, amniotic fluid embolism, venous air embolism, aspiration of gastric contents, respiratory infections, asthma, beta-adrenergic tocolytic therapy, and pneumomediastinum and pneu mothorax. Proper management of acute respiratory fail ure in pregnancy requires an understanding of the specific diseases and the normal gestational changes that occur in maternal respiration (decreased functional re sidual capacity, increased minute ventilation, mild respi ratory alkalosis) and hemodynamics (increased cardiac output, increased blood and plasma volume, unchanged central pressures). Knowledge of the determinants of oxygen delivery to fetal tissue (uterine blood flow, pla cental transfer, fetal circulation) and how they are af fected by changes in maternal hemodynamics, position, acid-base status, and medications can help sustain nor mal fetal development, whenever possible, without compromising maternal care. Diagnostic testing such as radiography, hemodynamic monitoring, and fetal moni toring are considered in terms of attendant risk to the mother or the fetus, alterations in normal values related to gestation, and indications for usage. Similarly, the risks and benefits of supportive and specific therapies for the various etiologies of acute respiratory therapy are reviewed.

Clinical aspiration-related practice patterns in the intensive care unit: a physician survey

OBJECTIVE

To characterize physician practice patterns regarding the clinical, microbiological, and antimicrobial-related events of suspected or documented aspiration and aspiration pneumonia within the intensive care unit.

DESIGN

National mail survey.

SETTING

University medical center.

STUDY POPULATION

Critical care physician members of the Society of Critical Care Medicine.

INTERVENTIONS

Survey questionnaire.

MEASUREMENTS AND MAIN RESULTS

The response rate was 645 (32%) of 2,000 mailed surveys; analysis of data represents completed questionnaires from 605 respondents. Intensivists (42.3%), pulmonologists (22.6%), and surgeons (21.6%) represent the majority of respondents. Altered level of consciousness (67.9%) in the intensive care unit was identified as the predominant predisposing factor for aspiration pneumonia. Sixty-four percent of physicians used sputum specimens, rather than protected specimen brushes or bronchoalveolar lavage, as the diagnostic source of bacterial cultures in cases of suspected aspiration pneumonia. Microbiological assessment of aspiration pneumonia revealed the absence of any predominant pathogen, although Staphylococcus aureus and Pseudomonas aeruginosa were cited in 40.1% of combined responses, whereas anaerobes represented the fifth most prevalent cultured bacteria. In cases of suspected and confirmed aspiration, 51.9% and 77.7% of respondents, respectively, would prescribe an antimicrobial agent in the absence of a definitive infectious process, with administration of dual antimicrobial therapy increasing from 28.9% to 46.0% in suspected vs. confirmed cases of aspiration. In the treatment of aspiration pneumonia, 27.6% of physicians preferred pathogen-specific therapy, whereas the remainder (72.4%) selected an empirical antibiotic regimen based on prior clinical experience. Overall, a beta-lactam/beta-lactamase inhibitor, followed by a cephalosporin, aminoglycoside in combination, or clindamycin, was most often selected for empirical therapy of all defined aspiration-related clinical diagnoses.

CONCLUSIONS

Our study revealed a divergent approach to antimicrobial treatment of cases of aspiration in the intensive care unit. Further investigation is warranted to determine why empirical antimicrobials are initiated frequently for noninfectious stages of aspiration.

Aspiration-Induced Pulmonary Injury

Pulmonary aspiration of gastric contents can cause a spectrum of sequelae that spans from relatively minor to rapidly lethal disease. To emphasize the extent of this spectrum and to encompass both noninfectious complications and infection, we use the term “aspiration-induced pulmonary injury” rather than “aspiration pneumonia.” In this article we review the relevant literature, focusing on more recent insights into the pathogenesis of lung injury, the natural history of aspiration, risk factors, the relationship between aspiration and infection, and recommendations for management. The relevance to human disease of studies using intra-airway acid instillation in animals is questioned. We discuss the difficulties in predicting the clinical course after aspiration. We identify risk factors for aspiration-induced pulmonary injury that are commonly encountered in the intensive care unit, and discuss in detail factors of special interest to the intensivist, including the impact of tracheal intubation; the effects of enteric intubation, particularly the comparison between pre- and postpyloric routes of enteric feeding administration; and the relative risks associated with particular feeding protocols. We conclude with recommendations regarding treatment and prevention strategies.

Is penicillin G an adequate initial treatment for aspiration pneumonia? A prospective evaluation using a protected specimen brush and quantitative cultures

OBJECTIVE

To evaluate the bacteriology of early aspiration pneumonia using a protected specimen brush and quantitative culture techniques, and whether penicillin G is adequate as initial treatment pending culture results.

PATIENTS AND METHODS

52 patients (of which 45 required mechanical ventilation) meeting usual clinical criteria for aspiration pneumonia were prospectively included. On admission, patients were given intravenous penicillin G and a protected specimen brush was performed < or = 48 h after.

RESULTS

Cultures of the brush were negative (< 10(3) CFU/ml) in 33 patients (1 had blood cultures positive with S. pneumoniae) and positive (> or = 10(3) CFU/ml) for S. pneumoniae in 2 patients. Seventeen patients had a positive culture (> or = 10(3) CFU/ml) for at least one penicillin G resistant microorganism, with a total of 20 organisms (S. aureus: 6; H. influenzae: 2; Enterobacteriaceae: 8; P. aeruginosa: 3; C. albicans: 1). In 4 of these patients, a penicillin-sensitive pathogen was also recovered in significant concentrations (S. pneumoniae: 2; Streptococcus sp.: 2). These 17 patients with a resistant pathogen did not differ from the 35 other patients with respect to need for ventilatory support and mortality rate. By contrast, they were older (61.1 +/- 21.9 vs. 42.9 +/- 18.8 years; p < 0.005) and required longer mechanical ventilation (6.1 +/- 4.6 vs. 3.5 +/- 2.7 days; p < 0.03) and hospitalization (11.2 +/- 8.8 vs. 6.7 +/- 4.7 days; p < 0.02). Of 17 patients 12 with penicillin G resistant organisms versus 0/35 without, were in-hospital patients and/or had a digestive disorder (p < 0.001).

CONCLUSION

The broad range of offending organisms seen in early aspiration pneumonia precludes use of any single empiric regimen, making protected specimen brush mandatory in many patients. Nevertheless, the involvement of S.pneumoniae in a notable proportion of our patients suggests that routine penicillin prophylaxis after early aspiration (at least in most patients with community-acquired aspiration) is warranted given the potential severity of pneumococcal sepsis in such patients.