Department of Nephrology, Vrije Universiteit Medical Center, Amsterdam, The Netherlands
Correspondence and offprint requests to: Marcel C. Weijmer, MD, Department of Nephrology, Vrije Universiteit Medical Center, Postbox 7057, 1007 MB Amsterdam, The Netherlands. Email: mc.weijmer{at}vumc.nl
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Abstract |
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Methods. Catheter and patient characteristics, catheter-related complications and all cultures taken from haemodialysis catheters inserted during a 3 year period were collected.
Results. We analysed the outcome of 272 catheters (149 patients, 11 612 catheter-days, 37 TCC and 235 UC). Patients with an UC suffered more often from acute renal failure (40 vs 8% for TCCs, P<0.001), their hospitalization rates were higher (54 vs 14%, P<0.001) and coumarins were used less (11 vs 27%, P<0.01). Rates of preliminary removal were 1.8 per 1000 catheter-days for TCCs, 35.3 for untunnelled femoral catheters (UFCs) and 17.1 for untunnelled jugular catheters (UJCs). Infection rates were 2.9 per 1000 catheter-days for TCCs, 15.6 for UJCs and 20.2 for UFCs. Hospitalization was an independent risk factor for an adverse outcome and more apparent in patients with an UC. After correction for patient differences, the strongest risk factor for preliminary removal (RR 9.69, P<0.001) and infection (RR 3.76, P<0.001) was having an UC inserted. Already, within 2 weeks actuarial and infection-free survival were better for TCCs (P<0.05 vs all separate groups).
Conclusions. According to our results, a TCC should be used whenever it can be foreseen that a haemodialysis catheter is needed for more than 14 days.
Keywords: catheter; haemodialysis; patency; tunnelled cuffed; uncuffed; vascular access
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Introduction |
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Reported bacteraemia rates vary from 3.86.5 per 1000 catheter-days for UCs and 1.65.5 for TCCs [59]. In these studies, catheter care protocols and the definition of complications differ. In addition, because UCs and TCCs are used for different clinical situations, the higher incidence of complications in UCs may be caused by differences in patient characteristics and risk factors for infection. These factors all contribute to the finding that the incidence of catheter-related complications can vary widely between types of catheters used and dialysis centres [10]. Therefore, comparison of outcome of UCs in one centre with TCCs in another centre is not reliable as was clearly pointed out by Lund et al. [11].
The aim of the present study was to compare the outcome of TCCs with UCs limiting as much as possible the influence of confounding factors. The second purpose was to see whether our results support the time recommendations for maximum use of UCs outlined in the NKF-DOQI guidelines.
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Subjects and methods |
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Catheters, catheter care protocol and catheter outcome assessment
For femoral, we used straight dual-lumen polyurethane catheters of 20 cm, for the right subclavian site 15 cm and for the left subclavian position 20 cm [Quinton (Seattle, WA, USA), n = 18; Gamcath (Gambro, Hechingen, Germany), n = 113]. For the internal jugular position we used the same catheters with curved extensions (Quinton, n = 15; Gamcath, n = 89). For TCCs we used Neostar Circle-C (Horizon Medical Products, Atlanta, GA, USA; n = 24), PermCath (Quinton Instruments, Bothell, WA, USA; n = 5), Tesio twin-cath (n = 3) and Ash-split (Medcomp, Medical Components Inc., Harleysville, PA, USA; n = 5).
All catheters were inserted under local anaesthesia and strict asepsis, and sutured to the skin. Catheters were only used by experienced dialysis nurses or nephrology staff, using sterile gloves and masks. The semi-occlusive transparent dressings we used, were inspected every dialysis session and changed at least once a week, the exit-site being cleansed with a povidone-iodine solution. Before removing the caps, the catheter hubs were disinfected with a chlorhexidine solution (2.5%). After dialysis, all catheters were locked with unfractionated heparin (5000 U/ml) with a volume equivalent to the internal volume of the lumen noted on the catheter. Catheters were used for haemodialysis exclusively.
Catheter-related bacteraemia (CRB) was defined as fever or cold chills with positive blood cultures and no other obvious cause of infection. When a CRB was established, the catheter could be left in place in the case of good clinical response on initiation of antibiotic treatment. No catheter exchange procedures for CRB were performed. A catheter-related exit-site infection was considered to be present on clinical grounds by the caring nephrologist, a culture of the exit-site was taken and treatment with antibiotics had been started.
In accordance to national guidelines, the minimal acceptable Qb was 200 ml/min, the target was 250 ml/min. The target for dialysis efficiency was a Kt/V of at least 1.2 per treatment. When the minimal acceptable blood flow was not achieved or when the catheter was occluded, urokinase, 10 000 U/ml for 15 min, was installed with a volume equivalent to the internal volume of the lumen. In general, when Qb improved but 200 ml/min was not achieved, the procedure could be repeated, otherwise the catheter was removed or exchanged over a guide wire.
Statistical analysis
Statistical analysis was performed with SPSS software 9.0 (SPSS Inc., Chicago, IL, USA). Non-parametric tests for two (MannWhitney U-test) and multiple continuous variables (KruskalWallis test) were used. For comparing binary and categorical variables chi-square and Fisher's exact tests were applied where appropriate. ANOVA was used to compare age and time on dialysis between multiple groups. KaplanMeier survival curves were constructed to analyse the patency rates and infectious complications. Functional catheters at the end of the observation time and catheters removed because they were not needed anymore were analysed as censored values. Curves were constructed for all patient and catheter characteristics mentioned in Table 1. The log-rank test was used to compare groups and identify individual risk factors associated with a preliminary removal or catheter-related infection. At an individual two-sided P-value of <0.1, the factor was included to fit a Cox-regression model. We have included male sex, acute renal failure, time on dialysis, hospitalization and having an UC inserted in the final model. We used a forward stepwise conditional technique to identify the factors independently associated with catheter failure and infection. An R2 of linear regression was estimated for infection-free survival and overall patency curves. Actuarial catheter survivals at 14, 21 and 28 days were counted with the use of life tables and significance was calculated with the log-rank test for the individual time periods. Differences were considered statistically significant for P<0.05.
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Results |
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In our study, the risk for an adverse outcome or infection for second or more insertions was not increased (RR 1.10, 95% CI 0.751.62, P = 0.62) and therefore these catheters were not analysed separately. Patient and catheter characteristics are given in Table 1. Of patients who had a TCC inserted, 92% were on chronic haemodialysis treatment in contrast to patients with an UJC (62%, P<0.001) and to the group of all UCs combined (60%, P<0.001). Patients with UCs were characterized by higher hospitalization rates for non-catheter-related reasons compared to TCCs (54 vs 14%, P<0.001). Also, patients with UCs were those patients admitted to intensive care more often (P<0.01). Furthermore, 27% of TCCs were inserted with the use of a guide wire exchange procedure (P< 0.01) and more patients with a TCC were on coumarin treatment (11 vs 27%, P<0.01). Other differences in patient characteristics were not significant.
Catheter outcomes
Of 235 UCs inserted, 128 (54%) were removed because they were not needed anymore compared to 26 (70%) of TCCs. In contrast, 107 (46%) UCs had to be removed for a complication compared to 11 (30%) TCCs (P<0.001 by log-rank analysis). Catheter and patient characteristics are shown in Table 2. The rate for preliminary removal per 1000 catheter-days was lowest for TCCs (1.8) and highest for UFCs (35.3). UJCs and USCs had similar rates (17.1 and 16.1 per 1000 catheter-days) but were also higher than TCCs. Reasons for premature removal differed slightly but not significantly between UCs and TCCs. Infection was the primary reason (49% for UCs and 55% for TCCs). Considering UCs only, USCs were removed less because of infection but more for persistent flow problems or mechanical complications, compared to both UFCs (P<0.05) and UJCs (P<0.01) catheters. Log-rank analysis of survival curves showed better patency rates for TCCs compared to any of the untunnelled groups (P<0.001) adjusted for hospitalization. Of UCs, outcome of UFCs was significantly worse compared to USCs (P<0.05) and UJCs (P<0.01) (Figure 1A). Cumulative hazard-ratio analysis of adverse outcomes showed a linear appearance for all catheter groups suggesting the risk of adverse outcome is constant over time (test for linearity R2 > 0.8 for all groups).
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Infectious complications
A total of 35 episodes of CRB occurred in 31 catheters in 27 patients; in eight patients an exit-site infection preceded CRB. There were 45 episodes of solitary exit-site infections. Differences in CRB and exit-site infection rates within the catheter groups are presented in Table 3. Infection rates for TCCs (2.9 per 1000 catheter-days) were significantly lower compared to UCs (12.8 per 1000 catheter-days, P<0.001 by log-rank testing), especially to UJCs (15.6 per 1000 catheter-days, P<0.001) and UFCs (20.2 per 1000 catheter-days, P<0.01). CRB rates per 1000 catheter-days showed analogous results (Table 3).
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Risk factors for infection differed only slightly from risk factors for preliminary removal. Again, the only independent risk factors for infection were having an UC (RR 3.03, 95% CI 1.545.94, P = 0.001) and hospitalization in the week before the infection occurred (RR 2.72, 95% CI 1.754.22, P<0.001). Untunnelled and tunnelled jugular catheters were compared after correction for differences in patient characteristics. The strongest risk factor for infection (RR 3.76, 95% CI 1.887.51, P<0.001) or CRB (RR 3.07, 95% CI 1.088.74, P<0.05) was having an UJC.
In 48% of cases, cultures yielded gram-positive microorganisms, predominantly Staphylococcus aureus or Staphylococcus epidermidis and in 36% of cases cultures yielded gram-negative microorganisms. The remaining cultures revealed multiple microorganisms or yeasts.
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Discussion |
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In a large prospective study analysing vascular access infection in 111 383 dialysis sessions, Stevenson et al. [2] found a relative risk for CRB of 1.9 for UCs compared to TCCs. However, the major limitation, already recognized by the authors in their discussion, was that no data were available on patient characteristics and sites of insertion and no corrections could be made for these potential confounding factors. Moreover, only 1.6% of all dialysis treatments were performed with the use of an UC suggesting that these catheters were used only in a very specific patient group. In studies investigating TCCs only, the incidence of CRB generally is lower (1.35.5 episodes per 1000 catheter-days) [5] compared to our results. It is, however, striking to observe the 4-fold higher incidence of CRB found in the study by Saad [6] (5.5 periods of CRB per 1000 catheter-days) compared to the study of Little et al. [8] (1.3 periods of CRB per 1000 catheter-days) while their study design and definition of CRB seemed comparable. These differences between catheter studies could well be caused by differences in patients characteristics or catheter management protocols. From these observations it is obvious that the reported complication rates for UCs and TCCs in these studies differ widely and cannot be used for individual comparison.
In the present study, we could demonstrate multiple differences between patients who had an UC or a TCC inserted. In particular, we observed more hospitalizations, an established risk factor for infections, for non-catheter-related reasons in patients with an UC. This observation concerning hospitalization as a risk factor for adverse outcome confirms the findings of Tokars et al. [10].
Another important factor influencing the outcome of catheters is the catheter care protocol. It has been shown in randomized studies and recommended in the NKF-DOQI guidelines that the risk for CRB can be reduced with a thorough protocol [3,12]. Even the level of education of the dialysis nurses concerning catheter handling influences the outcome [13]. Studies on catheter-related complications differ widely in these practices and could be an important confounder when comparing patency rates and CRB. In the present study, we have tried to exclude these possible confounding factors by using a similar catheter care protocol for all catheters.
To relate our results to the NKF-DOQI guidelines, we focused on the survival and infection rates for the time period of 4 weeks as UCs, especially UJCs could be a reasonable alternative to TCCs for this period of time [7]. We could demonstrate that even when a catheter is needed for only 14 days, the best survival and lowest infection rates were for TCCs. Within 2 weeks, 25% of UJCs had to be removed for a complication and in 27% an exit-site infection or CRB had occurred. Of all TCCs, only 5% had to be removed for a complication within 2 weeks and 9% of catheters were infected. This conclusion is also supported by the observation that the patency curves and the infection-free survival curves are close to linear (R2 > 0.8 for all curves). Linearity means that the risk is independent of time, that episodes of infection per 1000 catheter-days can be compared proportionally and are valid for every time period [11]. However, earlier use of TCCs must be weighted against the more time-consuming and difficult insertion and removal of TCCs and the higher costs.
It is not completely clear why TCCs have a lower risk for infection. One explanation could be that the fixation of TCCs can be achieved better by the use of a subcutaneous cuff and that bacterial migration from the exit-site to the venous entry site is impeded [14]. A recent meta-analysis has clearly demonstrated that cuffing and tunnelling of catheters reduces the risk for CRB by 4477%; however, this analysis only included non-haemodialysis catheters [15]. UJCs are more difficult to fixate properly. Furthermore, they have an upward directed exit-site, an established risk factor for infection in peritoneal catheters [16]. This is probably because debris can accumulate, colonization is promoted and pus cannot drain in cases of local infection. In addition, preliminary reports on precurved UJCs with a better possibility for fixation and a downward directed exit-site suggest they can be left in place for a longer period of time with an equivalent risk for infection compared to TCCs [17]. USCs mostly have a downward directed exit-site and can be fixated more easily. This could explain the lower risk for infection for USCs we found compared to UJCs, as was already shown in the study on UCs by Kairaitis and Gottlieb [5].
Another point that influences the function of catheters is their construction. As TCCs have a 23 Fr larger diameter and Poiseuille's equation dictates that the flow rate is inversely proportional to the diameter to the fourth power, it is clear that there is more reserve in the case of partial obstruction for TCCs compared to UCs.
Our study has several limitations. First, the present study represents observational and prospectively stored data and the allocation to any type of catheter was not randomized. Guidelines should ideally be based on results from prospective randomized studies. However, the need for a large randomized controlled trial could be questioned if our results had supported the time recommendations on the safe use of UCs. In the light of current recommendations, it is very difficult to conduct a randomized trial comparing TCCs and UCs and no such trial reports have appeared in the literature so far, despite the great number of catheters used worldwide. Secondly, as in almost all other catheter studies, we included all catheters inserted in patients and not only first episodes. This could lead to repeated tabulation of patients and dependency of catheter episodes. However, in temporary catheters, Oliver et al. [7] recently showed that multiple insertions, and even guide wire exchanges, are not a risk factor for an adverse outcome. For TCCs, Little et al. [8] could only find an increased risk for an adverse outcome when three or more TCCs were inserted. In our study, only three patients had two TCCs inserted and no patient had more then two inserted. Furthermore, the risk for an adverse outcome or infection for second or more insertions in our study was not increased (RR 1.10, 95% CI 0.751.62, P = 0.62). Thirdly, despite similar protocols for TCCs and UCs in our centre, there is a possibility that more often thrombolytic treatment was used for a dysfunctional TCC and that dysfunctional TCCs were left in place longer than dysfunctional UCs because the latter can be exchanged more easily. However, it is unlikely that dysfunctional catheters regain flow when one or two sessions of intraluminal thrombolytic therapy are unsuccessful [18]. In addition, the acceptance of a blood flow of 200250 ml/min has probably favoured the results for UCs. Finally, culture results were not collected prospectively. As every exit-site culture and blood culture sent from one of our haemodialysis patients to the department of microbiology was reviewed, it is not likely we missed infectious periods or introduced systemic errors favouring one of the catheter groups.
In conclusion, the present study shows that UFCs, USCs and UJCs are associated with a high rate of premature removals and infectious complications compared to TCCs. According to our results, a TCC should be used whenever it can be foreseen that a haemodialysis catheter is needed for at least 14 days which is earlier than currently recommended by the NKF-DOQI. This indicates that almost no UC should be used in daily practice. However, when new strategies to reduce catheter-related complications, such as better designed UJCs and antimicrobial locking solutions [19,20], are introduced in clinical practice, the outcome of UCs may improve and new prospective randomized studies will be needed to estimate the time period for which UCs can be used safely.
Conflict of interest statement. None declared.
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References |
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