Blood Cultures in the Emergency Department Evaluation of Childhood Pneumonia

Samir S. Shah, MD, MSCE; Maria H. Dugan, BA; Louis M. Bell, MD; Robert W. Grundmeier, MD; Todd A. Florin, MD; Elizabeth M. Hines, BA; Joshua P. Metlay, MD, PhD

Disclosures

Pediatr Infect Dis J. 2011;30(6):475-479. 

In This Article

Results

During the study period, 9099 eligible children from the ambulatory care cohort received a discharge diagnosis of CAP. Of these, 877 (9.6%) were evaluated in the ED (Table, Supplemental Digital Content 1, http://links.lww.com/INF/A721). Among those evaluated in the ED, the mean age was 3.6 years (median, 2 years; range: 0–18 years) and 52.5% were males. Most (69.1%) patients were non-Hispanic blacks. Comorbidities included asthma (40.6%), cerebral palsy (2.6%), and chromosomal abnormalities (1.7%). Pneumonia-associated complications were diagnosed in 81 (9.2%) patients. Complications included organ dysfunction (7.0%), complicated pneumonia (3.7%), and metastatic infection (0.2%); 1.6% (n = 14) had more than one pneumonia-associated complication.

Blood cultures were obtained from 291 children (33.2%). The prevalence of bacteremia among those with blood cultures obtained was 2.1% (95% CI: 0.8%–4.4%) (Table 1). Bacteremia was absent in some subgroups including patients discharged home after evaluation in the ED and patients without an infiltrate on chest radiograph. The prevalence of bacteremia was higher in other subgroups of patients including patients with pneumonia-associated complications (Table 1). Among patients diagnosed with a complicated pneumonia (effusion/empyema, lung abscess, or necrotizing pneumonia) the prevalence of bacteremia was 13% (95% CI: 2.8%–33.6%). S. pneumoniae was the most common causative organism accounting for 4 of the 6 cases of bacteremia (Table, Supplemental Digital Content 2, http://links.lww.com/INF/A722). All 4 cases of pneumococcal bacteremia were caused by serotypes not included in the heptavalent pneumococcal vaccine. All 4 S. pneumoniae isolates were susceptible to penicillin by current standards for nonmeningeal infections. The remaining 2 cases of bacteremia were caused by S. aureus (methicillin-resistant) and H. influenzae (nontypable). The contamination rate was 1.0% (95% CI: 0.2%–3.0%). Contaminants were coagulase-negative staphylococci in all 3 cases.

Compared with children without blood cultures, children with blood cultures were more likely to be >5 years of age (37.8% vs. 13.3%; P < 0.001) and have either partial or absent heptavalent pneumococcal vaccination history (44.0% vs. 33.1%; P < 0.001). Blood cultures were also more frequently obtained in children with clinical examination findings suggestive of more severe illness including those described as ill-appearing and those with hypoxia. Approximately two-thirds of patients who were eventually diagnosed with pneumonia-associated complications and half of those hospitalized had a blood culture obtained on initial evaluation.

There were no statistically significant differences in demographic, clinical, or laboratory variables at initial presentation between patients with and without bacteremia (Table 2). However, the 6 patients with bacteremia did have a higher rate of pneumonia-associated complications (66.7%) compared with both nonbacteremic patients (16.5%, P = 0.010) and patients without blood cultures obtained (5.1%, P < 0.001). The most common complications were respiratory failure in bacteremic patients (50%), sepsis in nonbacteremic patients (10.2%), and sepsis in patients without a blood culture obtained (3.6%).

All patients with a positive blood culture were admitted to the hospital on initial presentation. Table, Supplemental Digital Content 2, http://links.lww.com/INF/A722, summarizes the changes in clinical management in patients with positive blood cultures obtained during initial ED evaluation. Blood culture results altered management in 5 of the 6 bacteremic patients of whom 1 had an appropriate broadening of final antibiotic coverage and 4 had an appropriate narrowing of final antibiotic coverage. The only patient (case 2) with a bloodstream infection not sensitive to empiric therapy had methicillin-resistant S. aureus infection; this patient had severe back pain and a concomitant epidural abscess diagnosed by magnetic resonance imaging. In this instance, the blood culture result led to an appropriate change in antibiotic therapy and prompted additional diagnostic tests that meaningfully contributed to the diagnosis. The management changed for 1 of the 3 patients with contaminant blood cultures; changes in this patient included a repeat blood culture and 1 day of unnecessary treatment with vancomycin. No adverse events attributable to changes in therapy were reported.

Of the 586 patients without a blood culture obtained in the ED, 28 (5%) had a blood culture obtained within 3 days of presentation. Among those with a delayed blood culture, 1 was positive for pathogenic bacteria (methicillin-sensitive S. aureus) and 2 were considered contaminants (Staphylococcus hominis; Staphylococcus epidermidis). If these patients with delayed blood cultures were included in our overall analysis, the prevalence of bacteremia would be 2.2% (95% CI: 0.9%–4.5%).

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