Catheter-Related Bloodstream Infection

Chapter 116 Catheter-Related Bloodstream Infection



Sean Smarick, VMD, DACVECC



KEY POINTS



• Intravenous catheters may become contaminated and can lead to local and distal infectious complications. A bacteremia caused by a colonized catheter is referred to as a catheter-related bloodstream infection (CRBSI).

• The diagnosis of a CRBSI includes culturing the catheter or blood or both, but any fever of unknown origin, bacteremia, or infection at the insertion site should prompt the clinician to consider a CRBSI.

• Treatment of known CRBSI includes removing the catheter and administering systemic antibiotics.

• Frequency of CRBSI may be reduced by aseptically placing and maintaining catheters and educating caretakers involved in catheter placement.


DEFINITION


Intravenous catheters are often used in critically ill patients, but they can become contaminated with microorganisms. Skin contaminants may be introduced during placement or may migrate along the external surface of the catheter. Additionally, contamination of the catheter hub or infusate may lead to colonizing of the internal surface. Some bacteria produce biofilm, a matrix of microorganisms and their produced glycocalyces along with host salts and proteins that provide protection from the host’s defenses. Catheter contamination may lead to local signs of phlebitis; when catheter colonization leads to a bacteremia, the resultant infection is referred to as a catheter-related bloodstream infection (CRBSI).1,2



INCIDENCE


CRBSI has been reported in dogs and cats. In small animal intensive care units, CRBSIs have been implicated as a cause of morbidity and mortality.3-7 In veterinary medicine the incidence of catheter contamination has been reported as 10.4% to 22% in peripheral catheters3,7,8 and from 0 to 26% in jugular catheters, which is consistent with human reports.6,7,9 CRBSI is well studied in humans, and the incidence is approximately 5% with central venous catheters.10 In a few prospective studies in veterinary medicine, the incidence in small animals has been reported as 1 in 88 with peripherally placed 8-inch and 12-inch catheters,3 1 in 65 in similar catheters placed in the jugular vein,6 0 in 30 in jugular catheters in cats,9 and 2 in 121 with both peripheral and centrally placed catheters.7 This approximates to a combined rate of 1.3% (bloodstream infections per 100 catheters). This rate likely underestimates the current and future incidence of CRBSI, because peripheral venous catheters have a lower rate of CRBSI, and the use of central venous and arterial catheters is increasing in veterinary medicine. Indwelling catheters that are tunneled through the subcutaneous tissues have been described for long-term use (weeks to months) in veterinary patients. Some of these catheters have access ports also placed subcutaneously. The combined reported rate of CRBSI for these types of catheters of 2 in 60 is consistent with rates reported in people for similar types, despite a decreased duration of catheterization in the veterinary patients. The veterinary population was overrepresented by patients undergoing radiation therapy for neoplasia, and that group included both of the patients that developed CRBSI.11-13



DIAGNOSIS


CRBSI should be considered in febrile patients that have an intravascular catheter in place when there is no other obvious source of infection. Phlebitis and, especially, purulent discharge at the catheter site may indicate that catheter colonization has resulted in a localized infection that may lead to a CRBSI; however, the lack of localized reaction does not rule out a CRBSI, because close to 50% of humans show no local signs. Because clinical signs are not reliable, cultures are required for the diagnosis of a CRBSI.1,14 It should be noted that a CRBSI differs from a catheter-associated bloodstream infection. In a CRBSI, the catheter is the primary source of infection whereas in a catheter-associated bloodstream infection, a catheter is seeded and colonized by organisms spread hematogenously from another source of infection. The lack of an identifiable or suspected source of infection and critical interpretation of cultures are needed to diagnose a CRBSI.14


Considering the relatively low incidence of CRBSI, routine screening of qualitative (i.e., positive versus negative) catheter tip or segment cultures is not recommended because of the number of false-positive results.14,15 Numerous culturing methods of diagnosing a CRBSI have been reported and the source (intraluminal versus extraluminal) of the infection, number of lumens of the catheter, availability of culturing methods, ability to aspirate the catheter, and need to keep the present catheter in place may dictate which method is to be used in individual patients. Because infections identified soon after catheter placement tend to originate on the external surface, and infections of long-term catheters tend to originate on the internal lumen, culturingblood from the lumen may be a source of false-negative cultures in short-term catheterization.14 Multilumen catheters pose a challenge in that one or multiple lumens may be colonized, leading to false-negative results if only one lumen is cultured. In one study involving humans, sampling only one lumen of a triple-lumen catheter identified only 60% of the CRBSIs.16 Catheters do not necessarily need to be removed to diagnose a CRBSI. Considering the low number of true CRBSIs in febrile patients, catheters in such patients may remain unless they are no longer needed, they have a purulent discharge, or the patient is decompensating.1,14,17


Ideally, quantitative cultures of blood obtained percutaneously and through the catheter are obtained. A positive result is one in which the catheter-obtained culture(s) has 3 to 5 times greater bacterial concentration than the culture obtained percutaneously. Alternatively, qualitative cultures in which positive blood culture results from the catheter precede results from the percutaneous culture by more than 2 hours can be used if the quantitative methods are unavailable. If neither method is available or if the catheter is removed, a semiquantitative culture obtained by rolling a 5-cm section of the catheter four times over a blood agar plate and finding more than 15 colony-forming units (CFU) per ml is also a method with good sensitivity and specificity in humans. Qualitative or quantitative (>100 CFU/ml) blood cultures drawn from the catheter and quantitative cultures (>1000 CFU/ml) of broth that was flushed through or sonicated with the catheter have also been described for diagnosing CRBSI. Staining lysed cells from catheter-obtained blood samples with acridine orange to look for organisms and performing cultures of endoluminal brushing of the catheter also show promise as additional methods of diagnosis.1,14


For obtaining blood cultures, the catheter and percutaneous site should undergo aseptic preparation, equal volumes for each sample should be collected, and the samples should be obtained within 10 minutes of each other. Ideally, cultures are obtained before instituting empiric antibiotic therapy.1,14

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  2. Hyperthermia and Fever
  3. Ventilator-Associated Lung Injury
  4. Allergic Airway Disease in Dogs and Cats and Feline Bronchopulmonary Disease

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Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Catheter-Related Bloodstream Infection

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