Catheter-related sepsis (CRS) remains one of the most important potential complications of the use of a pulmonary artery catheter. Although most of the published data on CRS relates to its occurrence in relation to central venous cannulation it is probably fair to assume that the same principles apply to the occurrence of CRS in the patient with a pulmonary artery catheter.

Two common mechanisms of catheter contamination have been implicated. In one the catheter becomes colonised by the patient's own skin flora while in the other hub-contamination occurs as a result of the use of faulty aseptic technique during catheter handling.

Catheter colonisation occurs by the spread of skin flora (typically coagulase -ve staphylococci or enterococci) along the external surface of the catheter. In a fascinating study by Elliot et al ²³ it has also been demonstrated that despite rigorous skin disinfection and observance of a strict aseptic technique, viable microorganisms can be impacted during the insertion of a central venous catheter and can be isolated from the tip of the catheter in about 15% of cases.

Catheter contamination occurs as a result of soiling of the hub of one of the lumens by pathogenic, nosocomial organisms (particularly staphylococcus aureus and candida spp) with subsequent intraluminal spread of the organism to the intravascular portion of the catheter.

The haematogenous spread of infection from a distant source (for example the lung or urinary tract) is often suggested as a cause of catheter contamination, but is usually not relevant ². The only exception to this rule is in the case of infection with candida spp where up to half the infections may have been seeded from the patients own gastrointestinal tract. Rarely, endocarditis may complicate catheter-related bacteraemia ¹.

Widely varying rates of catheter colonisation and blood-stream infection are quoted. At one end of the spectrum, colonisation rates of 5% have been reported ²¹ at the other, rates more than 20% are not unusual ^{3, 4}. The incidence of blood-stream infection is consistently lower than the colonisation rate and is typically reported as 10-30% of the colonisation rate.

It must also be understood that colonisation and infection rates are partly determined by the culture technique which is used to establish the diagnosis. The 'classical' technique is that of Maki ⁵ who described an extraluminal roll plating method and defined a minimum 'cut-off count' which was necessary to make the diagnosis of catheter infection. More recently it has become apparent that endoluminal sampling techniques ⁶ are more sensitive and specific for the diagnosis of catheter-related sepsis. As a result, line colonisation is diagnosed twice as commonly when endoluminal as opposed to extraluminal sampling is used.

If sepsis occurs, it will greatly increase the risk of central venous thrombosis ⁷ and it has been estimated that an episode of CRS will add an additional 6.5 days to the duration of stay in an Intensive Care Unit at a cost of $US 29,000 ⁸.

The incidence of CRS is determined by various factors. The most important ones include:

1. Duration of placement.
The longer a catheter is in place, the more likely it is to become infected ⁹. Furthermore, the risks of infection increase sharply if the PAC is in place for more than 3 days. If the risk of bacteraemia is expressed in terms of 'risk per catheter day', an incidence of 6-8 cases per 1000 catheter days is typical ^{10, 11, 12}.

2. Route of insertion.
The internal jugular route is associated with a fourfold increase in the risk of CRS as compared to the subclavian route ¹³.

3. Geographic site of insertion.
At least one study ¹³ has found that placement of the catheter in the operating theatre as opposed to the critical care unit increases the risk of CRS.

4. Immunoparesis of the patient.
The effect of immunoparesis from any cause on CRS in patients with pulmonary artery catheters has not been specifically studied. In patients with central venous catheters, the impact of immunoparesis on the incidence of CRS is very marked ¹⁴ and it seems unlikely that the case is any different for those with indwelling PACs.

5. Multi-lumen catheters.
Multi-lumen central venous catheters are associated with a marked increase in the risk of CRS. No data are available for PACs which incorporate additional lumens, but presumably the same effect holds true.

Various techniques and technologies which are intended to reduce the incidence of CRS have been tried. These include:

1. Regular inspection of the insertion site.
The insertion site should be inspected daily and the catheter removed if pus is present.

2. Antibiotic prophylaxis.
There is a suggestion in the literature that antibiotic prophylaxis protects against CRS, but this effect is not very marked.

3. The use of antimicrobial-impregnated catheters.
The incidence of CRS may be reduced by using catheters which are impregnated with chlorhexidine and silver sulfadiazine or minocycline and rifampin. In one study ¹¹, the incidence of colonisation of the catheter was reduced from 24.1 to 13.5 per 100 catheters and this was matched by a near fivefold reduction (4.7:1) in the risk of bloodstream infection. In contrast, two other studies failed to demonstrate a significant reduction in the risk of blood-stream infection ^{16 , 12}, although in one the incidence of colonisation was reduced ¹⁶. In a recent meta-analysis by Veenstra et al ²² the risk of both catheter colonisation and catheter-related bloodstream infection was found to be approximately halved by the use of chlorhexidine-silver sulfadiazine-impregnated central venous catheters. In a separate study, the same authors concluded that the use of antimicrobial-impregnated catheters (in the United States) would decrease direct medical costs by $US196 per catheter inserted ²⁷. McGee and Gould ²⁵ and Mermel ²⁶have recently published separate reviews in which they recognise the importance of antimicrobial-impregnation of catheters as a strategy for reducing the rate of catheter-related sepsis. In their review, McGee and Gould remarked that: "The use of antimicrobial-impregnated catheters should be considered in all circumstances, especially when the institutional rate of catheter-related bloodstream infections is higher than 2 percent, which is the threshold at which chlorhexidine-and-silver-sulfadiazine–impregnated catheters may reduce overall costs."

4. Prophylactic catheter changes.
There are no data relating to PACs, but perhaps surprisingly, the incidence of CRS is apparently unaffected if central venous catheters are changed 'prophylactically' in an attempt to ensure line sterility ¹⁷.

5. The use of systemic heparin or heparin-bonded catheters.
A recent meta-analysis by Randolph et al ¹⁸ suggested that prophylactic heparin administration decreased the risk of catheter-related venous thrombosis and bacterial colonisation of central venous catheters and might decrease catheter-related bacteraemia. Heparin bonding decreased the risk of pulmonary artery catheter clot formation within the first 24 hours.

6. The use of 'dry' rather than transparent film dressings.
Several studies have suggested that gauze rather than transparent film dressing of the insertion site is associated with a lower rate of catheter colonisation ^{19, 20}. However, it should be noted that these studies do not relate to the current generation of permeable polyurethane dressings.

7. The use of chlorhexidine impregnated dressings.
More recently, chlorhexidine impregnated dressings have been introduced. The 'Biopatch' antimicrobial dressing (Johnson and Johnson, Arlington, TX, U.S.A.) is a hydrophilic polyurethane absorptive foam dressing impregnated with chlorhexidine gluconate. It is designed to release chlorhexidine and inhibit bacterial growth for more than seven days. It has been shown to significantly reduce bacterial colonisation of central venous catheter sites ²⁴.

The whole subject of catheter-related infection has recently been comprehensively reviewed by Fraenkel et al ¹⁵. These authors have also commented on the diversity of the criteria which are used in the diagnosis of a catheter-related infection and have suggested a more rational definition of the terminology which might be applied to a patient with CRS (Table 1).

In the United States, an expert committee based at the Centers for Disease Control and Prevention (CDC) have published 'Guidelines for prevention of intravascular device-related infections'.

1. Bernardin G Milhaud D Roger PM Pouliquen G Corcelle P Mattei M Swan- Ganz catheter- related pulmonary valve infective endocarditis: a case report. Intensive Care Med 1994, 20 [2]: 142- 4.

2. Anaissie EJ, Samonis G, Kontoyiannis D, et al Role of catheter colonization and infrequent hematogenous seeding in catheter-related infections. Eur J Clin Microbiol Infect Dis 14(2):134-137, 1995.

3. Mermel LA, McCormick RD, Springman SR, Maki DG The pathogenesis and epidemiology of catheter-related infection with pulmonary artery Swan-Ganz catheters: a prospective study utilizing molecular subtyping. Am J Med 1991 Sep 16;91(3B):197S-205S

4. Rello J, Coll P, Net A, Prats G Infection of pulmonary artery catheters. Epidemiologic characteristics and multivariate analysis of risk factors. Chest 1993 Jan;103(1):132-6

5. Maki DG, Weise CE, Sarafin HW A semiquantitative culture method for identifying intravenous-catheter-related infection. N Engl J Med 1977 Jun 9;296(23):1305-9

6. Kite P, Dobbins BM, Wilcox MH et al Evaluation of a novel endoluminal brush method for in situ diagnosis of catheter related sepsis. J Clin Pathol 1997 Apr;50(4):278-82

7. Timsit JF, Farkas JC, Boyer JM et al Central vein catheter-related thrombosis in intensive care patients: incidence, risks factors, and relationship with catheter-related sepsis. Chest, 114:207-13, 1998 Jul

8. Raad II In: 'Infections in Medicine' Infect Med 13(9):807- 812

9. Raad I; Umphrey J; Khan A; Truett LJ; Bodey GP The duration of placement as a predictor of peripheral and pulmonary arterial catheter infections. J Hosp Infect, 23(1):17-26 1993

10. McLaws ML, Murphy C, Taylor P, Coroneos N Measuring line-related bacteraemia in intensive care patients. Anaesth Intensive Care; 26:282-286 1998

11. Maki DG, Stolz SM, Wheeler S, Mermel LA Prevention of central venous catheter-related bloodstream infection by use of an antiseptic-impregnated catheter. A randomized, controlled trial. Ann Intern Med 1997 Aug 15;127(4):257-66

12. Logghe C, Van Ossel C, D'Hoore W, Ezzedine H, Wauters G, Haxhe JJ Evaluation of chlorhexidine and silver-sulfadiazine impregnated central venous catheters for the prevention of bloodstream infection in leukaemic patients: a randomized controlled trial. J Hosp Infect 1997 Oct;37(2):145-56

13. Mermel LA, McCormick RD, Springman SR, Maki DG The pathogenesis and epidemiology of catheter-related infection with pulmonary artery Swan-Ganz catheters: a prospective study utilizing molecular subtyping. Am J Med 1991 Sep 16;91(3B):197S-205S

14. Tacconelli E; Tumbarello M; Pittiruti M et al: Central venous catheter-related sepsis in a cohort of 366 hospitalised patients. Eur J Clin Microbiol Infect Dis, 16(3):203-9 1997

15. Fraenkel DJ, Rickard C, Lipman J: Can We Achieve Consensus on Central Venous Catheter- Related Infections? Anaesth Intensive Care 2000; 28: 475-49

16. Heard SO, Wagle M, Vijayakumar E, McLean S, Brueggemann A, Napolitano LM, Edwards LP, O'Connell FM, Puyana JC, Doern GV Influence of triple-lumen central venous catheters coated with chlorhexidine and silver sulfadiazine on the incidence of catheter-related bacteremia. Arch Intern Med 1998 Jan 12;158(1):81-7

17. Eyer S; Brummitt C; Crossley K; Siegel R; Cerra F Catheter-related sepsis: prospective, randomized study of three methods of long-term catheter maintenance. Crit Care Med, 18:1073-9, 1990 Oct

18. Randolph AG; Cook DJ; Gonzales CA; Andrew M Benefit of heparin in central venous and pulmonary artery catheters: a meta-analysis of randomized controlled trials. Chest, 113:165-71, 1998 Jan

19. Conly JM, Grieves K, Peters B: A prospective, randomized study comparing transparent and dry gauze dressings for central venous catheters. J Infect Dis 159:310 - 318, 1989.

20. Craven DE, Lichtenberg DA, Kunches LM, et al A randomized study comparing a transparent polyurethane dressing to a dry gauze dressing for peripheral intravenous catheter sites. Infect Control 6:361-366, 1985.

21. Myers ML; Austin TW; Sibbald WJ Pulmonary artery catheter infections. A prospective study. Ann Surg, 201(2):237-41 1985

22. Veenstra DL, Saint S, Saha S et al Efficacy of antiseptic-impregnated central venous catheters in preventing catheter-related bloodstream infection: a meta-analysis. JAMA 1999 Jan 20;281(3):261-7.

23. Elliott TS, Moss HA, Tebbs SE et al Novel approach to investigate a source of microbial contamination of central venous catheters. Eur J Clin Microbiol Infect Dis 1997 Mar;16(3):210-3

24. Hanazaki K, Shingu K, Adachi W, Miyazaki T Chlorhexidine dressing for reduction in microbial colonization of the skin with central venous catheters: a prospective randomized controlled trial. J Hosp Infect. 1999 Jun;42(2):165-8.

25. McGee DC, Gould MK. Preventing complications of central venous catheterization. N Engl J Med. 2003 Mar 20;348(12):1123-33.

26. Mermel LA.Prevention of intravascular catheter-related infections. Ann Intern Med. 2000 Mar 7;132(5):391-402.

27. Veenstra DL, Saint S, Sullivan SD. Cost-effectiveness of antiseptic-impregnated central venous catheters for the prevention of catheter-related bloodstream infection. JAMA. 1999 Aug 11;282(6):554-60.

Last edited on: 30/03/2003