The topic of CLABSI comes up sufficiently often in the exams that the candidates should make a point of reviewing it before every exam sitting, just to make sure they remember all the obscure minutae required of a detailed answer. Hisotrically, Question 8 from the first paper of 2006 and Question 2 from the second paper of 2000 asked for a list of preventative strategies, so as to protect your patients from the evils of CLABSI. On a slightly different note, Question 10 from the first paper of 2017 and the identical Question 6 from the second paper of 2019 were more administrative-oriented questions on how one might fashion a departmental policy to investigate and manage an out-of-control CLABSI rate. Question 14 from the second paper of 2024 went in a slightly different direction and asked how to decontaminate a precious central line, and what exactly makes it precious.
Below is a summary of recent guidelines and evidence, scraped together from the following sources:
Oh's Manual has a section on "line sepsis" (page 730 of the 7th edition) nested within Rishi and Dhillon's "Nosocomial Infections" chapter. Though brief, the section contains several important definitions which were probably worth knowing around the time of publication. The defintions offered below are from the The Australian Commission on Safety and Quality in Health Care report on CLABSI, which probably supercede Oh's Manual.
In summary:
Cental line colonisation:
- The growth of >15 colony-forming units (semiquantitative) or 100 (quantitative) from a proximal or distal catheter segment, in the absence of accompanying clinical symptoms and signs.
Central line associated blood stream infection (CLABSI):
- A laboratory-confirmed bloodstream infection in a patient where the central line was in place for over 48 hours on the date of the event, where the organism cultured from blood is not related to an infection at another site
CLABSI rate
- CLABSI rate = (Number of CLABSI / number of central line days ) ×1000
- i.e. CLABSI rate is number of CLABSIs per 1000 central line days
Rishi and Dhillon quote this massive 2006 review to produce the following infection risk profile:
Risk of infection per 1000 catheter days:
| Peripheral cannula |
0.5 |
| Arterial line: |
1.7 |
| Normal central line |
2.7 |
| Tunneled CVC |
1.6 |
| PICC |
1.1 |
| PA catheter |
3.7 |
Factors associated with increased risk of central line infection
- Femoral site (as opposed to subclavian)
- Non-tunnelled line (tunneling is protective)
- Plain uncoated catheter
- Antibacterial coating reduces risk of infection
- Antiseptic coating reduces the risk of colonisation
- Multiple lumens
- Frequent line access
- Frequent dressing changes (or very infrequent)
- Insertion by inexperienced operator
Mechanisms of central line infection
- Contamination during insertion
- Unclean CVC being inserted with a substandard sterile technique
- "Re-wiring" of an old line, rather than the insertion of a new line
- Contamination of insertion site after insertion
- Use of contaminated site, eg. groin
- Even subclavian lines can get infected if the patient' head hangs over them, and a stream of drool is constantly washing over the dressing.
- Poor care for dressings
- Use of solutions prone to contamination (eg. propofol, lipid or TPN)
- Contamination of lumen by breaking of sterile line connection
- Poor line changing and port handling technique (one is supposed to use chlorhexidine-soaked gauze)
- Haematogenous contamination of intravascular portion
- Antimicrobial-impregnanted catheters are supposed to prevent this from happening
- One may wish to be proactive about treating bacteraemia from organisms which are known to colonise plastic.
Prevention of central line associated blood stream infections:
- Intelligent decisionmaking regarding the indication for CVC insertion
- Use subclavian lines.
- Minimum number of lumens.
- Use of dedicated lumens for lipid infusions.
- Immunosuppressed patients or those with burns should have antibiotic-coated lines.
- For insertion, use aseptic technique and maximal barrier precautions.
- 0.5% chlorhexidine in 70% alcohol is the preferred cleaning agent.
- Handle ends of administration sets with gauze soaked in chlorhexidine.
- Review the line site daily.
- Remove the line as soon as possible.
- Change lines early - however, there is no evidence for how many days one can safely wait. Oh's Manual recommends that "there is no indication for routine CVC line changing based on catheter days".
- Sterile, transparent semipermeable dressings
- Change dressings regularly (every 7 days for standard dressings)
Positive blood cultures from the CVC
So, your CVC culture is positive. The meaning of positive CVC cultures is discussed in full in a separate summary article. In brief:
Positive cultures collected from the CVC could mean one of three things:
- CVC is colonised by organisms which are benign and doing no harm; in fact 15-25% of CVCs are colonised (usually by coagulase-negative staph) and the patients are fine, without any features of infection.
- CVC is colonised by organisms which are causing a clinically significant bacteraemia.
- CVC may still be colonised, but the culture grew organisms representing a systemic bacteraemia which did not originate in the CVC.
Organisms which Usually Represent "True" Bacteraemia:
- Staphylococcus aureus
- Streptococcus pneumoniae
- Streptococcus pyogenes
- Streptococcus agalactiae
- Escherichia coli
- Enterobacteriaceae
- Pseudomonas aeruginosa
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- Listeria monocytogenes
- Neisseria meningitidis
- Neisseria gonorrhoeae
- Haemophilus influenzae
- Bacteroides fragilis
- Cryptococcus neoformans
- Candida albicans
|
Organisms which Usually Represent CVC Colonisation:
- Corynebacterium sp.
- Bacillus sp. other than Bacillus anthracis
- Propionibacterium acnes
- Micrococcus sp.
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- Viridans group streptococci
- Enterococci
- Clostridium perfringens
- Coagulase-negative staphylococci.
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Risk factors for clinically significant S.epidermidis bacteraemia:
- Anyone at risk of native valve endocarditis
- Artifical valves
- History of rheumatic heart disease
- Immunosuppressed
- Implated pacemaker, or any other surgical implant
- Low birth infant
- Elderly person (>65 years of age)
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Management of CLABSI
- Though the advice would have to be tailored to each specific scenario, some broad recommendations can be made:
- 14 days of antibiotics IV is the standard.
- Some jurisdictional variability in the duration of antibiotics is to be expected
- the old 2009 ISDA guideline had 5-7 days for CONS, 7-14 days fro enterococcus, and 14 days for the rest (Mermel et al , 2009)
- Guenezan et al (2018) yield some different values, eg. 7 days for uncomplicated CONS and 14 days for all the rest.
- Ideally, the infected line should be removed. This represents the gold standard in source control
- If the patient remains bacteraemic >72 hrs following catheter removal, they are treated essentially the same as infective endocarditis, i.e the antibiotics are continued for 4-6 weeks. Plus they should obviously also have a workup for endocarditis.
Why might you not want to remove the catheter?
Some situations call for a more conservative approach. The following list was offered as a part of the answer to Question 14 from the second paper of 2024, based on the excellent work by Davidson et al (2016):
- Catheter is difficult to resite
- The patient has thrombosis or stenosis of common sites
- Expertise to resite the catheter is not readily available
- IR guided approaches are not available
- The patient
- Catheter is dangerous to resite or remove
- the patient is profoundly cogulopathic
- The patient has extremely fragile skin, burns, or some kind of desquamative skin condition, making resiting adhesive dressings more difficult
- The catheter is long-term and has adhesions that will require surgical removal, and the patient is for whatever reason opposed to surgery or has contraindications to it
- Catheter is easy to decontaminate
- The organism is susceptible to first tier therapies
- The organism is a low virulence organism
- The patient is at low risk from sepsis (eg. fully immunocompetent and otherwise fit and healthy)
- Catheter is essential for lifesaving therapy
When you must remove the infected catheter:
Here's the 2009 IDSA take on the indications for mandatory removal of an infected CVC:
- The patient is in florid septic shock because of the infected line
- The organism is a high-virulence organism (eg. S.aureus, Enterococcus, Candida, mycobacteria)
- The site is grossly contaminated, i.e. it looks so gross that it would be embarrassing to keep the line in
- The patient already has endocarditis
- You tried to manage things conservatively, but the bacteremia continues despite 72 h of correct antibiotics
Options to decontaminate an infected CVAD
So, you decided to keep the line, and your plan is to clean it up and make it useable again.
Some counterarguments to this:
- In about a third of such situation, this is looked back on with some regret (Dibb et al, 2016, found about 33% end up coming out anyway).
- One's line is never again entirely free of suspicion and each time the patient becomes febrile the question will come up again; and if the infected CVAD is removed that time, then the entire period of conservative management is viewed as something of a waste.
But let's say those are not strong arguments in your own specific individual case. Other studies have reported ~80% success rates (Corkum et al, 2017). A range of options are available:
- Rewire the line. "Guidewire exchange" is what this is occasionally referred to in the literature. The least satisfying of all the options, because it really just replaces an old contaminated line with a new contaminated line, connected by the guidwire that innoculates one with organisms from the other. This is most likely to work where there is only one lumen convincingly contaminated in a multilumen line, and/or where there is appetite for a prolonged course of antibiotics.
- Treat systemically with a prolonged course of antibiotics. You commit to treating these patients as if they already have infective endocarditis. Thie caveat is that this will sterilise the patient but not the catheter, expecially if the contamination is in the lumen or hub.
- Lock the catheter with antibiotics. The catheter lumen is filled with antibiotic solution, and the lumen remains undisturbed for a sufficiently long time, so that the bugs inside the lumen are exposed to a high concentration of agent, for a prolonged time. Multiple recipes exist (there is no standardised approach) but the rule of thumb is to use a high concentration and a long period, eg. Fortun et al (2006) who filled the lumen with solutions of vancomycin or gentamicin (2mg/ml) for 8-12 hours each day, for 5-14 days. The caveat is that the fibrinous sheath surrounding the exterior of the endovascular portion of the catheter will not be affected by this.
- Lock the catheter with something horribly corrosive. Another chapter deals with this in more detail, as it is more effective where the catheter has become blocked with some kind of chemical precipitate, but considering the options include 70% elthanol and 0.1M hydrochloric acid, one might expect them to also be effective agains microbes.