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CHAPTER 66: Infectious Complications of Intravascular Access Devices Used in Critical Care 591

DEFINITIONS AND DIAGNOSIS 7. Dramatic improvement of a febrile syndrome following catheter
OF DEVICE-RELATED INFECTIONS removal
8. Clusters of bacteremia due to Enterobacter species for seemingly unap-
The diagnosis of device-related infections remains a major challenge parent reasons (suggesting common-source contamination of IV fluids)
and establishing a firm diagnosis of device-related bacteremia may be
very difficult. Basing the diagnosis and subsequent definition of device- Many definitions for catheter-related infections have been used, but
related infection on clinical or laboratory criteria alone each has its own none is considered standard or uniform. However, definitions have been
limitations. Using only clinical findings is unreliable because of poor recently published as part of a guideline to aid in the diagnosis and man-
sensitivity and specificity. Using fever as a finding with high sensitiv- agement of intravascular catheter-related infections, which incorporate
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ity is problematic because of poor specificity. Using inflammation or both clinical and laboratory criteria and are outlined below.
purulence at the insertion site as a finding has high specificity but poor Catheter colonization: Significant growth of at least one micro-
sensitivity. In addition, the definitions used for clinical purposes may organism in a quantitative or semiquantitative culture of the catheter
differ from those used for surveillance. 51 tip, subcutaneous catheter segment, or catheter hub.
Several laboratory techniques are available to assist in the diagnosis
of catheter-related infection but differences in definitions and method- Exit site infection (microbiologic): Exudate at catheter exit site yields a
ologies make data difficult to compare. Methods used include qualita- microorganism with or without concomitant bloodstream infection.
tive culture of vascular catheters in broth, semiquantitative culture of Exit site infection (clinical): Erythema, induration, and/or tenderness
catheters on solid media, and quantitative culture of catheters in broth, within 2 cm of the catheter exit site; may be associated with other signs
removing organisms by flushing or sonication. Qualitative culture in and symptoms of infection, such as fever or purulent drainage emerging
broth is not specific, is prone to contamination, and probably should not from the exit site, with or without concomitant bloodstream infection.
be done. The use of semiquantitative cultures of catheter tips or of the Tunnel infection: Tenderness, erythema, and/or induration >2 cm
intracutaneous portion of the catheter or central-line sheath using the from the catheter exit site, along the subcutaneous tract of a tunneled
roll-plate method described by Maki and colleagues defines significant catheter (eg, Hickman or Broviac catheter), with or without concomi-
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colonization as 15 cfu or more. Using this laboratory definition and tant bloodstream infection.
applying it to diagnosing catheter-related bacteremia, a specificity of 76%
to 96% and a positive predictive value of 16% to 31% have been reported. Pocket infection: Infected fluid in the subcutaneous pocket of a totally
Owing to its simplicity, the roll-plate method has been adopted widely in implanted intravascular device; often associated with tenderness, ery-
many hospital microbiology laboratories. The use of quantitative cultures thema, and/or induration over the pocket; spontaneous rupture and
of broth, in which the catheter has been flushed or sonicated, may be drainage, or necrosis of the overlying skin, with or without concomi-
more sensitive but is too time consuming and laborious for routine use. tant bloodstream infection.
Quantitative blood cultures and differential time to positivity (DTP) Blood stream infection (infusate related): Concordant growth of
have been recommended as laboratory methods to assist in the diagnosis a microorganism from infusate and cultures of percutaneously
of catheter-related bacteremia when catheter removal is not possible. obtained blood cultures with no other identifiable source of infection.
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Blood cultures are obtained simultaneously from the central catheter Blood stream infection (catheter related): Bacteremia or fungemia in a
(a retrograde “drawback” culture) and from a peripheral venipuncture. patient who has an intravascular device and more than one positive blood
A threefold or higher differential count from blood obtained from the culture result obtained from the peripheral vein, clinical manifestations of
central catheter or a DTP (growth in a culture of blood obtained through infection (eg, fever, chills, and/or hypotension), and no apparent source
a catheter hub lumen is detected by an automated blood culture system for bloodstream infection (with the exception of the catheter). One of the
at least 2 hours earlier than the culture of simultaneously drawn periph- following should be present: a positive result of semiquantitative (>15 cfu
eral blood of equal volume) is considered to be indicative of catheter- per catheter segment) or quantitative (>10 cfu per catheter segment)
2
related bacteremia according to recent guidelines. Other techniques catheter culture, whereby the same organism (species) is isolated from a
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for diagnosing CLABSI include acridine orange leukocyte cytospin, a catheter segment and a peripheral blood culture; simultaneous quantita-
rapid diagnostic microscopy method, and endoluminal brush sampling tive cultures of blood with a ratio of >3 : 1 cfu/mL of blood (catheter vs
quantitative blood culture, but neither technique has been widely used peripheral blood); differential time to positivity (growth in a culture of
and the endoluminal brush technique has been associated with several blood obtained through a catheter hub is detected by an automated blood
undesirable side effects. 54 culture system at least 2 hours earlier than a culture of simultaneously
Using clinical criteria alone to make a diagnosis of catheter-related drawn peripheral blood of equal volume).
infection is a challenge. Whereas the presence of culture-positive puru-
lent exudate at the catheter insertion site in the presence of bacteremia
with the same organism would define a catheter-related bacteremia, MANAGEMENT OF INFECTION
making the diagnosis is much more difficult with bacteremia in the The management of intravascular device–associated infections depends
absence of any inflammation at the catheter insertion site. Signs of local on several variables, including the type of infection (local or bacteremic),
inflammation at the catheter insertion site are present in only about 50% the microorganism(s) involved, the type of device (peripheral or central
of the cases of catheter-related bacteremia. Several clinicoepidemiologic catheter, totally implanted device), and the severity of illness of the patient.
features are helpful in distinguishing catheter-related bacteremia from An updated guideline was published recently that outlines these variables
bacteremia caused by another source. These findings, which may be in detail and provides detailed recommendations for the management of
present alone or in combination, include the following: intravascular catheter–related infections. Local infections at the cath-
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1. Absence of an alternative source for bacteremia on clinical examination eter insertion site in peripheral catheters should be treated with catheter
removal, local care, and topical and/or systemic antimicrobial agents as
2. Patient not considered at high risk for bacteremia appropriate. If a spreading cellulitis develops, extending along the course
3. Presence of local purulence at the catheter exit site of the catheter, then systemic antimicrobials and catheter removal are
4. Presence of Candida endophthalmitis in patients who are receiving indicated. The antimicrobials chosen should be based on microbiologic
total parenteral nutrition cultures obtained from the discharge present at the insertion site.
The management of central catheter-related infections is more com-
5. Sepsis that is refractory to antimicrobial therapy plex and depends on the microorganism, the type of device, and the
6. Bloodstream infection caused by staphylococci or Candida species clinical status of the patient. The recently published guidelines suggest
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