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.
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.
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 = (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:
|Normal central line
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
- Pseudomonas aeruginosa
- 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.
- Viridans group streptococci
- Clostridium perfringens
- Coagulase-negative staphylococci.
Risk factors for clinically significant S.epidermidis bacteraemia:
- Anyone at risk of native valve endocarditis
- Artifical valves
- History of rheumatic heart disease
- Implated pacemaker, or any other surgical implant
- Low birth infant
- Elderly person (>65 years of age)
Management of central line associated blood stream infections:
- 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.
- Ideally, the infected line should be removed.
- If the line is a Hickmans and there is a great interest in preserving it, one may atempt to "decontaminate" it by administering the antibiotics though its lumens.