Bacterial Colonization in Hemodialysis Temporary Dual Lumen Catheters: A Prospective Study

Aims. The use of hemodialysis temporary dual-lumen catheters is often complicated by infections, which may be a significant cause of death among patients with end stage renal disease (ESRD). The aim of this study was to assess the incidence of bacteremia and bacterial colonization related to non-tunneled, non-cuffed, dual-lumen temporary catheters in patients with ESRD submitted to hemodialysis. Methods. This study included 29 patients with ESRD. After catheter implantation, patients were monitored throughout the period of catheter permanence by means of blood samples collected weekly from a peripheral vein. Bacteria were isolated and identified according to CLSI recommendations. When catheters were removed for any reason, their tips were evaluated microbiologically. Results. A total of 194 blood samples from the 29 patients implanted with 55 catheters were analyzed. Of these, 15.5% (30 samples) demonstrated bacterial growth, principally Staphylococcus epidermidis (64.5%). Twenty patients (68.9%) presented at least one positive blood culture during follow-up. The median time for catheter colonization was 18.5 days (95% CI: 16.8–30.3). Of the 55 catheters implanted, 28 (50.9%) showed bacterial colonization, corresponding to 23.4 episodes/1000 catheter/days and 9.2 episodes of bacteremia /1000 catheter/days. Fifteen of 28 catheter tips analyzed showed bacterial growth (53.5%). In 14 of these (93.3%), there was agreement between the isolates from the catheter tip and blood cultures. Of 24 episodes of positive blood cultures from 20 different patients in 17 episodes (70.8%), the patients showed no clinical signs or symptoms of bacteremia. Conclusions. The high incidence of catheter colonization, the correlation between blood and catheter tip cultures, and the occurrence of frequent cases of asymptomatic bacteremia justify the proposal of routine peripheral blood collections to monitor patients undergoing hemodialysis with temporary dual-lumen catheters.     

Use of a silicone catheter with a Dacron cuff for dialysis short-term vascular access

Polyurethane and Teflon subclavian vein catheters have been widely used for temporary vascular access for hemodialysis, but their use has been associated with a significant complication rate. A silicone dual-lumen catheter with a Dacron cuff placed in the internal jugular or subclavian vein was evaluated as a means of obtaining short-term vascular access. Sixty-two catheters in 54 patients provided a cumulative experience of 206 patient-months. Blood flow rates greater than or equal to 200 mL/min were achieved, with a mean recirculation of 2.1%. Catheter function was better with placement on the right side. Exit-site infections developed in nine patients, for a rate of 5.3 episodes per 100 patient-months; all resolved with antibiotics. Catheter-related bacteremia occurred in one patient, for a rate of 0.49 episodes per 100 patient-months, a rate much lower than rates reported for polyurethane and Teflon catheters. Clotting occurred in 24.5% of catheters, and thrombolytic therapy was always successful in restoring function. Because of the lower rate of complications, the silicone dual-lumen catheter with a Dacron cuff provides a safer alternative for short-term hemodialysis vascular access than the Teflon and polyurethane catheters.     

Identification of central venous hemodialysis catheter-related infection by a semiquantitative culture method

BACKGROUND: Central venous hemodialysis catheter-related infection is a major cause of morbidity and mortality in the hemodialysis (HD) population. Due to an impaired immune response, symptoms and signs of infection may not be obvious, and thus bacteremia is often diagnosed and treated protractedly. In contrast, induction of the acute phase response is frequently observed in HD patients even without infection. Moreover, positive catheter cultures may result from contamination, asymptomatic colonization or infection. The aim of the present study was to compare the number of colonies from HD catheter tips, with symptoms and signs of infection in HD patients. METHODS: In a 10-year, single-center study, 53 HD patients (29 men, 24 women; mean age 66 +/- 10 years) who had their dialysis catheters removed were divided into 3 groups according to the number of colonies growing after rolling the catheter tip across blood agar (group I: <15 colonies [n=22], II: 15-50 colonies [n=15], III: >50 colonies [n=16]). RESULTS: The maximum white blood cell (WBC) count did not differ significantly between patients with low- and high-density colonization (group I: 11.746 +/- 9.680 WBC/microL vs. group III: 13.479 +/- 6.252 WBC/microL, p=NS) while maximum C-reactive protein (CRP) levels were higher in patients with high-density colonization (group I: 8.6 +/- 6.8 vs. group III: 19.2 +/- 12.2 mg/dL, p<0.05). Density of bacterial colonization was associated with the maximum body temperature (group I: 37.6 degrees C +/- 1.1 degrees C vs. 38.7 degrees C +/- 0.9 degrees C, p<0.05). Moreover patients with high-density colonization showed increased bacteremia (group I: 33% vs. group III: 93%, p<0.01) as well as an increased mortality due to septicemia (group I: 9% vs. group III: 50%, p<0.01). Patients of group II exhibited intermediate values in all analyses. CONCLUSION: The semiquantitative culture technique can help to differentiate between contamination and infection of central venous HD catheters and provides important prognostic information in dialysis patients.     

Factors influencing function of temporary dialysis catheters

AIM: To determine risk factors for failure of temporary dialysis catheters, we prospectively studied the outcome of 178 non-tunneled dual lumen catheters placed in 126 consecutive patients requiring treatment of acute renal failure (ARF) or end-stage renal disease (ESRD). METHODS: Internal jugular (IJ) or subclavian (SC) catheters were used in 122 instances and femoral catheters were employed in 56. RESULTS: IJ or SC catheters with tips in the right atrium or superior vena cava (n = 112) failed (defined as a blood flow < 250 ml/min) 17% of the time, compared with a 40% failure rate for catheters with more peripherally located tips (n = 10), p < 0.05, chi2 testing. In a multivariate analysis, use in ESRD and location peripheral to the SVC were risk factors for catheter failure. Use of one of three catheter brands was associated with a lower failure rate. Although mean venous pressures at 200 ml/min blood flow were higher in IJ or SC catheters that failed, the presence of a high venous pressure, number of catheter uses, IJ vs. SC placement, inpatient vs. outpatient status, and fresh venipuncture vs. placement over a guidewire passed through a previous catheter did not predict catheter malfunction. With femoral catheters, the only risk factor for failure was use in ESRD. CONCLUSION: Of the factors that can be influenced by placement technique, catheter tip location is most important. Whether one catheter brand is superior awaits further confirmation.     

Bacterial colonization of chronic hemodialysis catheters: Evaluation with endoluminal brushes and heparin aspirate

Tunneled catheters serve as interim access during maturation of a graft or fistula, or as a permanent vascular access in those patients who have exhausted their traditional access sites. However, bacteremia rates are high in patients with chronic catheters and indiscriminate removal of catheters during bacteremia increases morbidity and costs. A method to identify whether a catheter was colonized with the offending bacteria, without requiring catheter removal is desirable. We compared endoluminal brushing and heparin aspiration, to detect catheter colonization, in 24 asymptomatic patients undergoing elective tunneled hemodialysis catheter removal. The incidence of catheter colonization was highly correlated with catheter duration of inverted exclamation markY 30 days (p=0.03). Staphylococcus epidermidis represented 68% of the organisms isolated. No other organism accounted for more than 7% of the total. Fifteen (62.5%) of the 24 catheters had positive cultures. Eleven of the catheters were positive by culture of heparin aspirate and eight were positive by endoluminal brushing. Only four of the catheters were positive by both methods. The arterial lumen was more likely to have positive cultures than the venous lumen using either method. In this prospective investigation of tunneled hemodialysis catheters in asymptomatic patients we have demonstrated that a heparin aspirate sample is more likely to detect catheter colonization than a sample obtained using an endoluminal brush. Furthermore, 75% of catheters present for more than 30 days were colonized. Further study is needed to determine if the heparin aspirate method could be used in patients with bacteremia to accurately identify catheters that need removal.     

Central venous catheters as a vascular access modality for pediatric hemodialysis

Background The use of hemodialysis catheters is an essential component of dialysis practice. Children are particularly likely to require multiple courses of dialysis over their lifetime, hence the repeated need for vascular access. These catheters remain a significant source of morbidity and mortality. Methods All catheters inserted for hemodialysis at the Center of Pediatric Nephrology and Transplantation, Cairo University over a period of 40 months were studied. Patient data as well as data of catheter insertion, dwell, cause of removal and complications were reported. Results A total of 195 uncuffed central venous catheters were used for temporary access in 131 patients for a mean duration of 35.7 days. Of attempted insertions, 87.4% achieved successful access, of which 56% remained for the required period, 8.9% were accidentally dislodged, and 35.1% were removed due to complications—mostly infection. The overall rate of possible catheter-related bacteremia was 9.6 episodes/ 1,000 catheter days. Infection increased with longer catheter dwell. Nineteen cuffed tunneled catheters were surgically inserted and used for up to 11 months (mean 117 days). Loss of these catheters was attributed mainly to infection (ten episodes) and catheter thrombosis (six episodes). During the study, 317 femoral catheters were inserted. Conclusion Uncuffed central venous catheters are both needed and useful for short-term hemodialysis. Vascular access for extended durations may be provided by cuffed tunneled catheters. Infection is the major serious concern with both uncuffed and cuffed catheters.     

Safety of triple lumen catheters in the critically ill

The authors performed this prospective study to determine the infection rate of triple lumen catheters (TLC) in their surgical intensive care unit (SICU) patient population. Patients who required a central venous line for the first time while in their SICU were studied. Those with preexisting catheter infections, bacteremias, and TLC reinsertions were excluded. TLC was placed through the internal jugular or the subclavian vein and all peripheral lines were removed. The distal port was used for parenteral nutrition and the other two ports were used for fluids and medications. Dressings were changed daily and blood cultures were obtained through each port of the TLC. At the time of catheter removal, blood, catheter tip, and the subcutaneous tract were cultured. Duration of catheterization was recorded. Eighty-six catheters were studied. The mean duration of catheterization was 6.2 days and the range was two to 23 days. Six of 86 (6.9%) catheter tip cultures were positive and the remaining 80 (93.1%) were negative. Two positive tips (2.3%) had negative blood cultures for two catheter infections (CIs). The remaining four catheters (4.6%) had associated bacteremias for four catheter sepsis (CS). The two catheter infections occurred among catheters indwelling for 10 days or less while the four cases of catheter sepsis occurred among catheters indwelling longer than 10 days. In conclusion, triple lumen catheters can be safely left in place for up to 10 days with minimal risk for bacteremia.     

Conversion of temporary hemodialysis catheters to tunneled hemodialysis catheters

PURPOSE: To determine the feasibility and clinical outcomes of conversion of temporary to tunneled hemodialysis catheters using the same venous insertion site. METHODS: Data from 42 patients with existing temporary hemodialysis catheters referred for placement of tunneled hemodialysis catheters were retrospectively reviewed. In these patients, the temporary catheter was exchanged for a peel-away sheath, and a tunneled catheter was inserted using the existing venous access site. Technical success, procedural complications, and clinical outcomes were evaluated. Hemodialysis records were reviewed to assess catheter patency during a 30-day follow-up period. RESULTS: The study group consisted of 20 males and 22 females (mean age: 58 years). All 42 temporary catheters were successfully converted to tunneled hemodialysis catheters without immediate procedure-related complications. Follow-up data were available for 32 patients (total: 3038; median 71 catheter days). Nine catheters were removed for infection, yielding a catheter infection rate of 0.30/100 catheter days; three catheters were removed for blood flow <200 ml/min. 13 patients had catheters removed when catheters were no longer needed. Three patients died with working catheters. The patency rate was 72% at 30 days, with four catheters functioning at the end of the study period. CONCLUSION: Conversion of a temporary hemodialysis catheter to a tunneled hemodialysis catheter using the same venous insertion site is a safe procedure that avoids complications associated with venotomy and allows conservation of other central venous access sites. Patency and infection rates in these catheters are comparable to several studies of catheter exchange and de novo placement of tunneled hemodialysis catheters.     

Risk factor analysis for long-term tunneled dialysis catheter-related bacteremias

Infection, mainly related to vascular access, is one of the main causes of morbidity and a preventable cause of death in hemodialysis patients. From January 1994 to April 1998 we conducted a prospective study to assess the incidence and risk factors of catheter-related bacteremia. One hundred and twenty-nine tunneled dual-lumen hemodialysis catheters were inserted percutaneously into the internal jugular vein in 89 patients. Bacteremia (n = 56) occurred at least once with 37 (29%) of the catheters (an incidence of 1.1/1,000 catheter-days); local infection (n = 45, 1/1,000 catheter-days) was associated with bacteremia in 18 cases. Death in 1 case was directly related to Staphylococcus aureus (SA) septic shock, and septicemia contributed to deaths in 2 additional cases. Catheters were removed in 48% of the bacteremic episodes. Treatment comprised intravenous double antimicrobial therapy for 15-20 days. Bacteriological data of bacteremia showed 55% involvement of SA. Nasal carriage of SA was observed in 35% of the patients with catheters. Bacteremic catheters were more frequently observed in patients with diabetes mellitus (p = 0.03), peripheral atherosclerosis (p = 0.001), a previous history of bacteremia (p = 0.05), nasal carriage of SA (p = 0.0001), longer catheter survival time (p = 0.001), higher total intravenous iron dose (p = 0.001), more frequent urokinase catheter infusion (p < 0.01), and local infection (p < 0.001) compared with non-bacteremic catheters. Monovariate survival analysis showed that significant initial risk factors for bacteremia were nasal carriage of SA (p = 0.00001), previous bacteremia (p = 0.0001), peripheral atherosclerosis (p = 0.005), and diabetes (p = 0.04). This study confirms the relatively high incidence of bacteremia with tunneled double-lumen silicone catheters and its potential complications. Possible preventive actions are discussed according to the risk factors.     

Risk of bacteremia from temporary hemodialysis catheters by site of insertion and duration of use: a prospective study

BACKGROUND: Uncuffed, nontunneled hemodialysis catheters remain the preferred means to gain immediate access to the circulation for hemodialysis. Bacteremia is the primary complication that limits their use. The risk of bacteremia by site of insertion and duration of use has not been well studied. METHODS: Two hundred eighteen consecutive patients who required a temporary hemodialysis catheter were prospectively followed. RESULTS: Catheters were placed at 318 new insertion sites and remained in use for a total of 6235 days. The incidence of bacteremia was 5.4% after three weeks of placement in internal jugular vein and 10.7% after one week in femoral vein [relative risk for bacteremia 3.1 (95% CI, 1.8 to 5.2)]. The incidence of bacteremia was 1.9% one day after the onset of an exit site infection but increased to 13.4% by the second day if the catheter was not removed. Guidewire exchange for malfunction and patient factors did not significantly affect the risk of bacteremia. CONCLUSIONS: Internal jugular catheters may be left in place for up to three weeks without a high risk of bacteremia, but femoral catheters in bed-bound patients should be removed after one week. Catheter exchanges over a guidewire for catheter malfunction do not increase bacteremia rates. Temporary catheters should be removed immediately if an exit site infection occurs.     

Chlorhexidine versus povidone iodine in preventing colonization of continuous epidural catheters in children: a randomized, controlled trial

BACKGROUND: Chlorhexidine is better than povidone iodine for skin preparation before intravascular device insertion or blood culture collection, but it is not known whether chlorhexidine is superior in reducing colonization of continuous epidural catheters. METHODS: Children requiring an epidural catheter for postoperative analgesia longer than 24 h were randomly assigned to receive skin preparation with an alcoholic solution of 0.5% chlorhexidine or an aqueous solution of 10% povidone iodine before catheter insertion. Using surgical aseptic techniques, catheters were inserted into either the lumbar or the thoracic epidural space based on the preferences of the anesthesia team, on clinical indication, or both. Immediately before epidural catheter removal, their insertion site and hub were qualitatively cultures. After their removal, the catheter tips were quantitatively cultured. Catheters were classified as colonized when their tips yielded 1,000 or more colony-forming units/ml in cultures. RESULTS: Of 100 randomly assigned patients, 96 were evaluable. The clinical characteristics of the patients and the risk factors for infection were similar in the two groups. Catheters were kept in place for a median (range) duration of 50 (range, 21-100) h. Catheters inserted after skin preparation with chlorhexidine were one sixth as likely and less quickly to be colonized as catheters inserted after skin preparation with povidone iodine (1 of 52 catheters [0.9 per 100 catheter days] vs. 5 of 44 catheters [5.6 per 100 catheter days]; relative risk, 0.2 [95% confidence interval, 0.1-1.0]; P = 0.02). Coagulase-negative staphylococci were the only colonizing microorganisms recovered, and the skin surrounding the catheter insertion site was the origin of all the colonizing microorganisms. CONCLUSIONS: Compared with aqueous povidone iodine, the use of alcoholic chlorhexidine for cutaneous antisepsis before epidural catheter insertion reduces the risk of catheter colonization in children.     

A clinical trial on the prevention of catheter-related sepsis using a new hub model.

BACKGROUND: Catheter hub contamination is being increasingly recognized as a source of catheter-related sepsis. The authors have investigated the efficacy of a new hub design in preventing endoluminal catheter contamination and catheter-related sepsis arising at the hub. METHODS: Adult surgical and intensive care patients requiring a subclavian catheter for at least 1 week were randomly assigned to receive catheters with standard connectors (control group, n=73) or equipped with a new hub model (new hub group, n=78). Skin, catheter tip, and hub cultures were performed at the time the catheter was withdrawn because therapy was terminated or because of suspicion of sepsis, in which case peripheral blood cultures were taken. RESULTS: Of the 151 patients included, 15 (10%) developed catheter-related sepsis. Catheters were more often withdrawn because suspicion of infection in the control group (42 vs. 19%, p<0.005). Catheter sepsis rate was higher in the control group (16 vs. 4%, p<0.01) because of the low rate of catheter sepsis arising at the hub observed in the new hub group (1 vs. 11%, p<0.01). The prevalence of culture-positive catheter hubs without associated bacteremia (colonization) was higher in the control group (18 vs. 5%, P<0.03). CONCLUSIONS: A new catheter hub has proved to be useful in preventing endoluminal bacterial colonization and catheter-related sepsis in subclavian lines inserted for a mean of 2 weeks.     

Bacteremia associated with central venous catheter infection is not an independent predictor of outcomes

Background: Infection is the leading complication of central venous catheters. In the setting of suspected line infection, the CDC recognizes only catheter-related bloodstream infection but not catheter infection without bacteremia, which is designated “colonization.” To evaluate the hypothesis that catheter-related bloodstream infection has worse outcomes than catheter infection without bacteremia, we compared demographics, clinical data, and outcomes.

Study Design: Analysis of catheter infections was performed on data collected prospectively for all episodes of infection occurring from December 1996 to September 1999 on the surgical services at a university hospital. Catheter tips were cultured only when infection was suspected. Catheter infection without bacteremia was defined as systemic evidence of infection, the presence of at least 15 colony-forming units on the catheter tip by a semiquantitative technique, and absence of bloodstream infection with the same organism as the catheter. Catheter-related bloodstream infection required the presence of bacteremia with the same organism as the catheter tip.

Results: The 59 patients with catheter-related bloodstream infection had more coexistent infections than the 91 patients with catheter infection without bacteremia (2.9 ± 0.1 versus 1.7 ± 0.1; p = 0.0001), most commonly pneumonia (37.3% versus 16.5%, p = 0.004) and urinary tract infections (28.8% versus 8.8%, p = 0.001). Catheter-related bloodstream infection was associated with an increased proportion of gram-negative organisms compared with catheter infections without bacteremia (29.5% versus 16.9%, p = 0.04) and a trend toward fewer gram-positive organisms (61.5% versus 73.7%, p = 0.07). There were no differences in APACHE II score, WBC, length of hospital stay, time from admission to fever, time from fever to treatment, normalization of WBC, days of antibiotics, defervescence, gender, presence of comorbidities, occurrence of colonization while in an ICU, or mortality rate (18.6% with bacteremia, 24.2% without; p = 0.42).

Conclusions: The presence of bloodstream infection in addition to catheter infection does not appear to alter outcomes. The definition of catheter infection perhaps should be extended to include catheter infections without bloodstream infection in the presence of systemic illness without another source.     

Prevention of central venous catheter sepsis: a prospective randomized trial

A prospective randomized trial was undertaken to evaluate the influence of routine 72-hour catheter exchange and the use of an implantable collagen cuff in preventing central venous catheter infection in critically ill patients requiring multiple lumen central venous access. Patients were randomized to one of four groups, which determined whether the central venous catheter placed would be removed at 3 or 7 days and whether an implantable collagen cuff would be used or not. Upon removal, cultures of the central line tip, the insertion site, and peripheral blood were obtained. One hundred and fifty-nine catheters were studied in 85 patients during a 14-month period. There were 26 (16.4%) episodes of catheter colonization and four (2.5%) episodes of catheter infection in the entire population. Catheter colonization rates (same organisms cultured from catheter tip and skin site) were 14.5 per cent at 3 days and 18.4 per cent at 7 days. Infection rates (same organism cultured from catheter tip and peripheral blood culture) were 2.4 per cent at 3 days and 2.6 per cent at 7 days. With regard to the use of the collagen cuff, colonization rates were 14.5 per cent with the use of the cuff and 18.1 per cent without the use of the cuff. Infection rates were 5.3 per cent with the use of the cuff and 0 per cent without the use of the cuff. None of these differences reached statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of a silicone dual-lumen catheter with a Dacron cuff as a long-term vascular access for hemodialysis patients

We evaluated our experience over a 4-year period with a silicone dual-lumen catheter with a Dacron cuff (SDLCDC) to determine if the catheter represents an alternative to the polytetrafluoroethylene graft for long-term vascular access for hemodialysis patients. Records of 131 patients who used 168 catheters were reviewed for catheter function, duration of use, and occurrence and response to treatment of complications. Eighty-five percent of catheters functioned adequately until their use was no longer required or the end of the study. One-year catheter survival estimate was 65% and median survival estimate was 18.5 months. Mean blood flow rate achieved was 243 mL/min and recirculation was 7.5%. Exit-site infection occurred in 21% of patients and bacteremia in 12%. There were significantly more exit-site infections in diabetics than nondiabetics (33% v 11%, P less than 0.02). Exit-site infections resolved with parenteral antibiotic therapy in 90% and bacteremia in 25% of cases without catheter removal. Unresolved bacteremia was the most common cause of catheter removal and led to the loss of 7% of catheters. Thrombotic complications occurred in 46% of catheters. Urokinase instillation successfully treated catheter occlusion in 81% of cases. When urokinase instillation failed, streptokinase infusion restored catheter patency 97% of the time. The literature on the polytetrafluoroethylene (PTFE) graft was reviewed, and the SDLCDC was found to be similar to the graft in function, duration of use, and frequency of infectious and thrombotic complications. We conclude that the catheter represents an alternative to the graft for long-term vascular access in hemodialysis patients. Because of the frequent complications with both accesses, neither should be considered optimal. Further research is required to improve vascular access for patients in whom placement of an arteriovenous fistula is not possible.     

All currently used measurements of recirculation in blood access by chemical methods are flawed due to intradialytic disequilibrium or recirculation at low flow

Blood flows and recirculations with standard and reversed direction of lines were measured by chemical (urea and creatinine) and ultrasound dilution (saline) methods in 47 chronic hemodialysis patients. Thirty-seven patients had 47 dual-lumen, central vein (CV) catheters: 32 were PermCath (Quinton Instruments Company, Seattle, WA), 6 were Access Cath (MEDCOMP, Harleysville, PA), 3 were Soft Cell PC (Vas Cath, Mississauga, Ontario, Canada) and 6 were SNIJ (experimental catheters). Three of these last catheters had the tip staggered 7 mm, and three had flush tips; PermCath, Access Cath, and Soft Cell PC catheters have the tips staggered 23 to 25 mm. Forty-six catheters were implanted into the superior vena cava/right atrium, and one catheter was implanted through the left saphenous vein into the left iliac vein. The catheters were studied 1 to 31 months after implantation (median, 3.0 months). Ten patients with arteriovenous (AV) graft access were also studied. The stop-flow method was used in catheter dialysis, and the slow-flow method was used to calculate recirculations in AV access dialysis with samples for systemic blood concentrations taken from arterial line both before and after samples from the arterial and venous lines. At 500 mL/min pump speed, actual blood flow was 436+/-18 mL/min (mean+/-SD; range, 407 to 464 mL/min) with standard direction of catheter lines. At 500 mL/min pump speed, the arterial chamber pressure was -330+/-48 mm Hg (mean+/-SD; range, -380 to -225 mm Hg, and the venous chamber pressure was 259+/-48 mm Hg (mean+/-SD; range, 140 to 310 mm Hg). Arterial chamber pressure was less negative, and venous chamber pressure was less positive with SNIJ catheters, which had larger internal diameter (2.1 mm) compared with the other catheters (2.0 mm). Recirculation varied with the catheter design and the location of the catheter tip. In the catheters with tip staggered more than 20 mm and with standard line connection at pump speeds of 50 mL/min and 500 mL/min, recirculations were approximately 1 % and 5%, respectively, when measured by the chemical method. In the same catheters with reversed lines, the recirculations were approximately 5% and 27%, respectively. Inflow failure catheters with reversed lines had similar recirculation values to those of well-functioning catheters with reversed lines. In catheters with tips staggered 7 mm, and with standard connection of lines, recirculations were approximately 3% and 8%, respectively, at pump speeds of 50 and 500 mL/min. With reversed lines, at the same pump speeds, the values were 7% and 12%, respectively. In flush-tip catheters, the recirculation was higher at a 50 mL/min pump speed (approximately 17%) than at a pump speed of 500 mL/min (approximately 13%). The ultrasound dilution method usually gave lower values than the chemical methods, most likely because of overestimation of recirculation by chemical methods. At least triplicate measurements are needed because single measurements by the ultrasound dilution method are associated with substantial variation. We conclude that both currently used methods (stop flow and slow flow) of taking systemic samples for measurements of recirculation by chemical methods are flawed because of disequilibrium and recirculation at low flow.     

永久性双腔血液透析导管流量及再循环率的测定

目的了解不同型号永久性双腔血液透析留置导管的实际流量以及不同流量和连接方法下导管再循环率的情况,为永久性双腔导管的临床应用提供实证依据。方法将56例使用永久性双腔血液透析导管的血液透析患者根据留置导管不同分为Perm-cath组(P组)30例,Tal Palindrome TM组(T组)26例,利用Transonic HD02血液透析监护仪进行实际血流量监测。测定正接和反接状态下,泵设流量分别为150、200、250、300、350mL/min时的再循环率。结果无论正接还是反接,两组实际流量均能达到泵设流量的要求;不同泵设流量时正接和反接实际流量比较,差异无统计学意义(均P>0.05)。正接时泵设流量150～350mL/min,两组几乎没有再循环。反接时,不同泵设流量组内再循环率比较,差异无统计学意义(均P>0.05);但各不同泵设流量下,P组再循环率显著高于T组(均P<0.01)。结论两种永久性双腔血液透析留置导管血流量能满足泵设流量需求,正接时都没有再循环;反接时Tal Palindrome TM型再循环率比Permcath型低,两种导管再循环率不随泵设流量的增加而增加。因此,应尽量避免反接导管,必须反接时,可相应提高血流量,以保证透析效果。     

Bacterial contamination of epidural catheters: microbiological examination of 502 epidural catheters used for postoperative analgesia

STUDY OBJECTIVE: To investigate the frequency of bacterial colonization of epidural catheters used for postoperative pain treatment longer than 24 hours in abdominal, thoracic, or trauma surgery patients. DESIGN: Retrospective study. SETTING: Intermediate care facility and general ward of a university hospital. PATIENTS: 502 patients who received epidural catheters after abdominal, thoracic, or vascular surgery at our institution from January 1996 to December 2000. INTERVENTIONS: Placement of an epidural catheter, which was used for postoperative pain treatment, for more than 24 hours. The puncture site dressing included saturation each day with povidone-iodine. MEASUREMENTS AND MAIN RESULTS: Microbiologic monitoring of epidural catheter tips and daily examination of puncture sites with regard to signs of inflammation took place. Four times daily patients were examined to check adequacy of pain treatment and neurologic deficits. Catheter tip cultures were positive in 29 patients (5.8%). Staphylococcus epidermidis was isolated in 22 cases (76%). No case of spinal epidural abscess was observed within 6 months after epidural catheterization. The average catheterization time was 5 days (quartile range: 4 to 6 days). CONCLUSIONS: Meticulous management ensures a relatively low level of bacterial contamination in epidural catheters applied for postoperative pain treatment greater than 5 days. Contamination rarely leads to spinal epidural infection.     

Bacteremia in a pediatric hemodialysis unit secondary toEnterococcus fecalis

Bacteremia is often a serious and recurring problem in children with hemodialysis catheters. We report an outbreak ofEnterococcus bacteremia in a pediatirc hemodialysis unit occurring from June 1992 to June 1993. During this period, 18 episodes of bacteremia occurred in eight children: 11 infections were polymicrobial.Enterococcus fecalis was associated with 13 infections in five patients (8 polymicrobial). Other pathogens includedEnterobacter cloacae (5 infections),Staphylococcus (3),Staphylococcus epidermidis (2), andKlebsiella pneumoniae (2). AllEnterococcus infections occurred in patients with dual-lumen subclavian venous catheters. Skin and catheter sites were culture negative, except in one patient. Rectal swabs were positive forEnterococcus in five patients.Enterococcus was not isolated from any source within the unit. Serotypes of allEnterococcus isolates were different, except for 2 isolates in the same patient. Starting in June 1993, catheters were flushed after dialysis with vancomycin or ampicillin. Since initiating this procedure, further episodes ofEnterococcus bacteremia have not occurred. A questionnaire sent to other pediatric hemodialysis units failed to identifyEnterococcus among 26 cases of bacteremia. In conclusion: (1)Enterococcus is an unusual pathogen for hemodialysis-related bacteremia in children; (2) patients with dialysis catheters were predisposed to this infection; (3) a common source forEnterococcus could not be identified by either culture or by serotyping; (4) flushing catheters with antibiotics after dialysis was effective prevention.