INTRODUCTION

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Pulmonary artery catheters (PACs) are widely used for the hemodynamic management of critically ill patients. Bacteremia and fungemia are the major complications of vascular access. The frequency of pulmonary artery catheter-related bloodstream infections may have decreased in recent years for several reasons, including use of an aseptic technique for PAC insertion (1); PAC insertion through an introducer made of Teflon, which is more resistant to microbial adherence than the formerly used polyvinyl chloride (2); shorter durations of PAC, as compared with the other central venous catheters; and widespread use of heparin-bonded PACs in which the heparin is associated with benzalkonium chloride, a compound with some antimicrobial activity (3).

Most central venous catheter-related bloodstream infections begin with invasion of the transcutaneous catheter tract by microorganisms from the cutaneous microflora of the patient (1, 3), an event which is therefore a primary target of efforts aimed at preventing systemic infections associated with pulmonary artery catheterization (SIAPAC).

The new pulmonary artery catheter Arrow "Hands-Off" (AHO) (Figure 1) is completely shielded before, during, and after the insertion procedure. The absence of PAC-skin contact may decrease the incidence of invasion of the catheter by cutaneous microflora.

View larger version (84K): [in this window] [in a new window]   Figure 1.   The Arrow "Hands-Off" thermodilution catheter is a catheter enclosed in a contamination-proof shield with an integrated flushing balloon test chamber, enabling the physician to prepare, test, and insert the catheter without exposing it to external contamination.

We conducted a randomized prospective study in intensive care unit patients to assess the value of the AHO for preventing SIAPACs.

	METHODS

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Patients

The study was conducted in the intensive care unit (ICU) of the Avicenne University Hospital, Bobigny, France, over an 18-mo period, after approval by our institutional review board. Written informed consent was obtained in every case from the patient or next of kin.

All patients requiring PAC, for any reason or duration, were prospectively randomized into two groups, of which one (standard group) received the thermodilution catheter routinely used in our unit (Abbot, Rungis, France) and the other (AHO group), the AHO catheter (Arrow, Fresnes, France).

Physicians and Nurses

Before initiation of the study, all physicians working in the ICU were trained to insert the AHO. Patients and their PACs were monitored according to written protocols already used in our unit before the beginning of this study.

Procedure

Pulmonary artery catheters were inserted in the ICU rooms. Decisions to insert or to remove a PAC were at the discretion of each patient's ICU physician, who also decided on the site of insertion before random PAC allocation.

The insertion site was shaved and disinfected. All personnel involved in the procedure wore caps and masks. The sterile insertion technique included skin preparation with 10% povidone-iodine (Betadine; Asta Medica, Merignac, France), generous sterile draping of the insertion site, and donning by the physician of a sterile gown and sterile gloves after a 3-min scrub. An 8.5-Fr introducer was inserted percutaneously into a central vein under local analgesia, and anchored with a suture. A heparin-bonded PAC was then advanced through the introducer. When insertion was completed, the site was cleaned and covered with a sterile polyurethane dressing (Tegaderm; 3M, London, Ontario, Canada). Connection lines, the fluid reservoir bag, flushing devices, and the sterile dressing were changed every 72 h.

Evaluation Criteria

The following parameters were recorded: age, Simplified Acute Physiologic Score (SAPS) on admission and on inclusion (7), whether the procedure was done by a junior or senior operator, site of insertion, number of catheter insertion attempts, duration of insertion, hemodynamic diagnosis, duration of PAC use, peripheral and catheter blood culture results, catheter tip culture results, ICU stay duration, and mortality.

Catheter Removal

The decision to remove the PAC was at the discretion of the patient's physician, but all patients with the following criteria had their PACs removed: (1) temperature above 38.5° C or under 36.5° C for 24 h; (2) temperature increase for 24 h in a patient with evidence of sepsis; (3) purulent discharge from the insertion site; (4) inflammation at the insertion site and positive skin culture.

Definition

After removal of the PAC, the catheter tip was rolled over a blood agar plate. After 18 h of incubation at 37° C, the number of colonies was counted; a positive tip culture was defined as growth of more than 15 colonies on the agar plate (8). Bacteria were identified using standard methods.

The identity of the blood and catheter bacteria was established based on the identity of their antibiotic susceptibility patterns (9).

The primary evaluation criterion was occurrence of SIAPAC defined as presence of all of the following: recovery of the same organism from the thermodilution catheter and a peripheral blood culture, absence of any other focus of infection, and improvement or resolution of clinical evidence of infection after removal of the thermodilution catheter (3, 8, 10).

Duration of insertion was defined as the time between the first puncture to the time capillary pressure was obtained.

Statistical Methods

Data are presented as means ± standard deviation (SD). Comparisons between dichotomous variables were done using the chi-square statistic or the two-tailed Fisher's exact test. Differences in means of numeric variables were compared by Student's t test. p Values of less than 0.05 were considered statistically significant.

	RESULTS

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Patients

The 150 patients enrolled in the study received a total of 166 PACs, of which 78 were standard PACs and 88 were AHOs. Patients in the two groups were similar (Table 1) regarding age, SAPS on admission and on inclusion, and therapeutic risk factors. Also similar in the two groups were the proportions of procedures done by junior and senior operators; the distribution of insertion sites, with a majority of subclavian (50%) and internal jugular vein approaches; the number of PAC insertion attempts; duration of insertion; distribution of hemodynamic diagnoses, with heart failure being the most common condition; and mean duration of PAC use (3.6 versus 3.5 d in the standard versus AHO groups; range, 1 to 7 d).

Microbiological Findings

Catheters. The positive tip culture rate was 9% (95% CI, 4.65%-13.35%) in the AHO group and 25.6% (95% CI, 18.96%-32.24%) in the standard group (p < 0.007). The organisms most often recovered from catheter tips were coagulase-negative staphylococci (Table 2).

Systemic infections associated with pulmonary artery catheterization. SIAPACs occurred with eight PACs (10.2%; 95% CI, 5.60%-14.80%) in the standard group versus none in the AHO group (p < 0.002). Microorganisms recovered during SIAPAC episodes were Staphylococcus aureus (n = 3), Enterococcus faecalis (n = 1), Klebsiella pneumoniae (n = 2), and Pseudomonas aeruginosa (n = 2). All SIAPACs occurred in patients who were not taking antimicrobials (Table 2) and who had had their PAC for at least 4 d.

SIAPAC rates by insertion site were 2.4% (95% CI, 0.7%- 4.73%) in subclavian veins, 6.5% (95% CI, 2.75%-10.25%) in internal jugular veins, and 9.1% (95% CI, 4.72%-13.48%) in femoral veins. The failure of statistical testing to demonstrate any significant association between the insertion site and the occurrence of SIAPAC (p = 0.28) was probably due to the small sample size.

When patients with and without SIAPAC were compared, no differences were found for any of the study parameters (Table 3). Duration of PAC use was similar between these two groups, but it is important to note that all SIAPAC episodes occurred after at least 4 d of PAC use.

	DISCUSSION

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The most salient finding of our study is that SIAPAC occurring after prolonged PAC use was significantly less common with the AHO than with a standard PAC. Most catheter-related infections are thought to be secondary to colonization of the insertion site followed by spread of microorganisms along the outer surface of the catheter (1, 3, 14). In a prospective study in patients undergoing open heart surgery, Elliot and colleagues found that despite scrupulous disinfection of the skin around central venous catheter insertion sites microorganisms were recovered from 66% of skin cultures; from 50% of introducers, guidewires, or dilators; and from 16% of central venous catheter tips drawn through the atrial appendage (15). In a recent prospective clinical study of the pathogenesis and epidemiology of Swan-Ganz catheter infections conducted using molecular subtyping of microbial isolates, Mermel and colleagues showed that colonized skin at the catheter insertion site was the source of 79% of PAC infections, suggesting that most infections stem from invasion of the space between the outer catheter surface and the tissue along the insertion tract (4). Decreased contact between the PAC and contaminated skin may substantially decrease the risk of catheter-related bloodstream infections (15). The significant reduction in PAC colonization and the absence of SIAPAC episodes in our AHO group supports this possibility.

A definition of catheter-related infection that includes clinical symptom improvement or resolution after catheter removal has been used in many other studies (16, 17) and was chosen for this study because it is more stringent than other definitions (8, 11). We included all patients who had a Swan-Ganz catheter inserted, regardless of whether or not they had evidence of sepsis. Using a definition of catheter- related infection that does not include improvement or resolution after catheter removal could theoretically lead to misclassification of patients with sepsis due to noncatheter- related causes as having SIAPAC, thus overestimating the number of SIAPAC cases. However, this did not seem to occur in our study, since all patients with positive catheter cultures improved after catheter removal.

An assessment of the SIAPAC rate should distinguish between stable patients catheterized for a brief period of time, e.g., as a preoperative measure, and critically ill patients with heavy cutaneous colonization who required prolonged use of a PAC. SIAPAC rates have been low after short-duration PAC use (1-4%) (1, 11, 12, 18, 19) and substantially higher after prolonged PAC use (6-10%) (20, 21). The rate of SIAPAC in our standard group was identical to that in earlier studies of prolonged PAC use (10.2%; 95% CI, 5.60%-14.80%), despite maximum aseptic precautions (see METHODS). The absence of SIAPAC in our AHO group is in striking contrast with this finding.

None of our patients was scheduled for surgery, and all were in a critical condition involving failure of at least one organ. In addition, SIAPAC occurred only in patients who were not receiving antimicrobials. Most other studies included preoperative patients who were receiving antibiotic prophylaxis (1, 11, 12, 18), which reduced the SIAPAC rate. Therefore we did not restrict the duration of PAC use, and mean PAC use duration was higher in our study (3.5 d; range, 1 to 7 d) than in other studies (11, 12, 18). There have been several reports that the risk of SIAPAC increases with duration of PAC use, reaching 6-10% after 4 d (1, 18). In keeping with these reports, all SIAPAC episodes in our study occurred after 4 d of PAC use. Finally, insertion was via the femoral route for 22 PACs (13.3%), which is considerably more than in earlier studies (1, 11, 12, 18), and SIAPAC developed in two of the 22 cases (9.1%) versus two of the 82 (2.4%) PACs inserted via the subclavian route and four of the 62 PACs (6.5%) inserted via the internal jugular route.

Insertion of the AHO catheter may be more difficult and longer than that of other PACs, but after receiving specific training all the physicians in our study performed the procedure faultlessly, and duration of insertion was similar in the AHO and standard PAC groups.

A deterrent to the use of the AHO may be its higher price as compared to the standard PAC. However, this difference may be offset by savings resulting from a smaller number of SIAPAC episodes. Several studies (14, 22, 23) estimated the mean cost of treatment of each SIAPAC episode at 6,000 U.S. dollars ($3,000-$10,000), suggesting that in our study avoiding eight SIAPAC episodes more than offset the excess cost of the use of AHO (10 U.S. dollars/catheter).

This study demonstrates that the absence of contact with skin flora associated with AHO use is effective in preventing catheter tip colonization and systemic infections associated with pulmonary artery catheterization. It also confirms that the risk of pulmonary artery catheter-related bloodstream infection with standard PACs is very low if the device is left in place for less than 4 d.