Excluding Bacteremia in Children with Central Venous Catheters
Abstract & Commentary
By Hal B. Jenson, MD, FAAP, Chief Academic Officer, Baystate Health Professor of Pediatrics and Dean of the Western Campus of Tufts University School of Medicine, Baystate Medical Center Springfield, MA, is Associate Editor for Infectious Disease Alert.
Synopsis: Bloodstream infections associated with central venous catheters and caused by Gram-negative bacteria are significantly associated with an earlier time to positivity (99.2% at 36 hours) compared to other organisms (84.4% at 36 hours). The overall predicted probability for a culture being positive within 36 hours was 96.6% for catheter-associated infections.
Source: Shah SS, et al. How long does it take to "rule out" bacteremia in children with central venous catheters? Pediatrics. 2008;121:135-141.
A retrospective, cohort study of 200 episodes randomly selected from 315 episodes, during 2000-2003, at Children's Hospital of Philadelphia, of laboratory-confirmed bloodstream infections among out-patient children with central venous catheters was performed to determine the optimum duration of antibiotic therapy before infection could be reliably excluded. Blood cultures were performed using the BacT/Alert system, which automatically monitors carbon dioxide production every 10 minutes, 24-hours a day to detect bacterial growth. Patients with a single commensal organism isolated from the blood culture were excluded from the study.
The mean age of the children was 5.5 years (interquartile range, 2.7-12.1 years). The catheters included percutaneously inserted central catheters (PICC; 18), double-lumen (129), or single-lumen (22) Broviac catheters, double-lumen Medcomp catheters (12), subcutaneously implanted ports (14), and others (5). Catheters were in place for a median of 80.5 days. Among the 200 children, 134 (67%) were receiving Pneumocystic carinii prophylaxis, 42 (21.5%) had recently received antibiotics, 41 (20.5%) had recently received or were receiving parenteral nutrition, and 35 (17.5%) had received corticosteroids recently.
Among the 200 study patients, 127 (63.5%) had monomicrobial infections and 73 (36.5%) had polymicrobial infections, including 52 with > 1 gram-negative bacteria. The causative organisms included gram-positive bacteria (69), gram-negative bacteria (50), Candida (6), and rapidly growing mycobacteria (2). The most common gram-negative bacteria causing monomicrobial infections were Pseudomonas (16) and Klebsiella (12).
The median time to positive blood culture was 14.0 hours (interquartile range, 11.1-20.4 hours). Infections caused by gram-negative bacteria had a shorter time to becoming positive regardless of whether the infections were monomicrobial or polymicrobial. Most cultures with ≥ 1 gram-negative bacteria were positive within 24 hours of collection (94.1% predictive probability; 95% CI, 87.6-97.3%). In contrast, the predicted probability for infections caused by gram-positive bacteria or other organisms (eg, Candida and rapidly growing mycobacteria) was only 66.4% at 24 hours and 84.4% at 36 hours.
Vomiting at presentation was independently associated with an earlier time to positive blood culture, but was not associated with a specific organism.
Commentary
These results are useful in the management of suspected bloodstream infections among children with central venous lines by demonstrating that almost all (> 96%) bloodstream infections have positive blood cultures within 36 hours of collection. The results also show that infections caused by gram-negative bacteria are even more likely (99.2%) to have positive blood cultures within 36 hours of collection. This remained significant even after adjusting for age, catheter type, and recent treatment with antimicrobial therapy. This study was not able to assess blood culture volume, which directly influences time to positive blood culture. It is common that pediatric blood cultures, especially among very young children, include only 1-2 mL of blood, which may increase the time to becoming positive.
The results suggest that discontinuing antibiotic treatment among clinically stable children with central venous catheters is warranted if the blood cultures remain negative at 36 hours after collection. Vomiting was an independent marker of a shorter time to positive blood culture. It may be that vomiting is a sentinel marker of a more severely ill patient with higher-grade bacteremia, and should be an important part of the assessment of fever in children with central venous lines.
A retrospective, cohort study of 200 episodes randomly selected from 315 episodes, during 2000-2003, at Children's Hospital of Philadelphia, of laboratory-confirmed bloodstream infections among out-patient children with central venous catheters was performed to determine the optimum duration of antibiotic therapy before infection could be reliably excluded.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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