Increased risk of bacteremia in patients hemodialyzed through central catheters

As part of an ongoing prospective survey of nosocomial bacteremias. patients developing bacteremia while undergoing in-centre hemodialysis were observed over a 23 month period. Thirty-six episodes of bacteremia occurred in 30 patients: every episode was dircclly a ttributable to hemodialysis. In 28 of the 36 episodes (78%). there was evidence ofinnammation with or without drainage of pus at the hemodialysis access site. Staphylcx:occus aureus accounted for 76% of the INFECTION IS NOW THE PRINCIPAL CAUSE OF MORbidity and the second leading cause of death in patients undergoing hemodialysis. with vascular access the principal source of these infections (1.2) . As part of a hospita l-wide program of monitoring blood culture isolates for nosocomial bacteremias. the a uthors have been prospectively following patients acquiring bacteremia as a result of in-centre hemodialysis. The results of two years of s uch s u rveillance are presented. and evidence provided that hemodialys is through a percutaneous central venous access catheter greatly adds to the risk of d ialysis-related bacteremia. University of Alberta Hospitals. Edmonton. Alberta Correspondence and reprints: Dr CD Taylor. 2£3. 1 1 WMC. University of Alberta Hospitals. Edmonton. Alberta T6G 287 Received for publication January 25. 1990. Accepted April 3. 1990 CAN J INFECT DIS VOL 1 No 1 MAY 1990 bacteremic isolates. Patients hemodialyzing through central venous catheters had a far higher incidence of bacteremia (0.0 I per dialysis run) than patients hemodialyzing through vascular grafts (0.0005 per dialysis run). Can J Infect Dis 1990;1(1):11-14


PATIENTS AND METHODS
As part of a n ongoing infection control su n,eilla nce project identify ing nosocomia l bacteremia .h emodia lysis-related bacteremic episodes occurr-ing within the in-centre h emodia lysis un it were prospectively evalua ted over a 23 month period from August 1, 1986 lo June 30, 1988.One of the a uthors (TK) reviewed a ll positive b lood cultures reported by the h ospital microbiology labora tory.Bacteremic cases were reviewed by a physician (GT) prior to inclusion.All bactere mias occurr-in g in patients u nde rgoing hemodia lysis in the 16bed.in -centre h emod ia lysis unit were documented.Patients undergoing dia lysis for acute renal failure in the intensive care units were n ol included.A bacteremia was defined as a bacter-ial infection of Lhe bloodstream where one or more blood cu ltures contained pathogenic organisms.If culture yielded a typical skin commensal.two blood cultures taken at different sites or at different limes positive for the same species of bacteria were considered to represent bacteremia.One blood cu lture with a typical skin commensal was documented as a bacteremia if the attending physician diagnosed bacteremia and prescribed a course of antibiotic therapy directed against the bactercmic organism.Organisms considered to be skin commensals were: Corynebacterium species.Bacillus s pecies.viridans group streptococci.micrococcus.coagulase-negative staphylococci or Propionibacterium species.A single positive cu lture due to Staphylococcus aureuswas considered significant.The primary organ system caus ing the bacteremia .if present.was noted.and the mode of hemodialysis at the lime of bacteremia was determined (ie.via a vascular access graft or through central venous cannula).Evidence of access s ite infection was determined by direct inspection.Infection rates were calculated per dialysis run and per dia lysis year (one patient undergoing 156 h emodialysis nms was equivalent to one dialysis year) .
The University of Alberta Hospitals (UAJI) dialysis centre is a 16-bed unit providing in-centre h emodialysis services to an average of 100 patients , up to 283 runs/week.Patients arc preferentially dialyzed through an arteriovenous fistula.Dialysis U1rough a central venous catheter is undertaken if no fistula is in place or if the fis tula is actively infected or clotted.The right subclavian site is preferentially used: insertion is performed in the unit by house staff using the Scldingcr

RESULTS
Thirty-six episodes of bactere mia were detected in 30 patients.No source of infection apart from the dialysis access site was found in any patient: in 28 episodes (78%) there were clinical signs of infection (inflammation with or without drainage of pus) al the access site.Staph aureus was by far lhe most common isolate.accounting for 27 e pis odes (75%) (Table 1).There was one death in the bacteremia popula tion which was clinically direc tly attributed to infection with KLebsiella pneumoniae (bacteremia mortality rate 2. 7%).Dialysis via a central venous catheter was associated with 24 (67%) of a ll episodes of bacteremia.despite the fact that only 9% of all dia lysis in the unit is conducted through this type of access.Table 2 calculates b actere mia rate by mode of dialys is and a risk of bacteremia per dia lysis run.The bactere mia rate was 0.22 per patient dialysis year overall (0.08 for vascular graft dialysis patients and 1.56 for central venous catheter patients).
Of the 24 patients developing bacteremia while being dialyzed through a centra l line, the access site was in the subclavian position in 23 and the femoral site in one.Patients were undergoing central line dialysis because: no graft had yet been established (14 patients); a graft was established but not mature (nine patients): and presence of superficial graft site infection (one patient).
There was apparent clustering of infection suggestive of epidemic spread in the months of May and June 1988 (Figure 1).with 10 (27%) of the bacteremic episodes occurring during these last two months of the study.However, a case control study of staff members failed to reveal any staff member as having a significant association with dialysis on/off procedures in bacteremic cases.Likc,visc.phage typing of the 10 isolat<:>s in this two month period failed to reveal a common isolate.

DISCUSSION
This study is similar to others documenting the extent of risk of bacteremia in hemodialysis patients (1.4).It is also similar in documenting the type of microorganisms caus ing these infections (1.[4][5][6].Staph aureus accounted for 75% of all of lh<:> bacteremias seen in the 23 months of the study.Fortunately.the mortality rate related to these was quite low -only one death related to infection was seen.This is quite likely related to the close supervision patients undergoing incentre hemodialysis receive.probably resulting in prompt diagnosis and treatment of infection.
The major finding of this study was documentation of the great ly increased risk of uactcrcmia in patients undergoing hemodialysis via a central venous catheter.Since this was not a controlled study.it is possible that other factors associated with these patients are more important than the mode of dialysis itself.It seems unlikely that these possible other factors cou ld completely account for this greatly increased risk.It is left to be concluded that central venous access dialysis shou ld be avoided if at all possible.eg. by close following of patients with moderate degrees of renal Impairment and creation of vascular grafts well in advance of possible commencement of hemodia lysis.The vast majority of the centralline-related bacteremias (23 of 24) occurred in patients who either did not have a vascular graft in place or who had a graft not sufficiently mature to be used.Further steps should be taken to reduc<:> the risk of dialysis via central catheters.As the access cannula is left in place for weeks in some cases.it is not difficult to conceptualize the process by which microorganisms might traverse the •catheter wound' to enter the bloodstream.Other studies have demonstrated that colonization or skin at the insertion site of central venous catheters is a major source of organisms causing bacteremia (7).Staph aureus carriage on the skin has been demonstrated in 6 to 42% of the hemodialysis patient population (8.9).Staph aureus remained on the skin after skin prepara-lion a nd has been found to be prese nt in s i~ nifica nlly heavie r growth in persons with poor hygiene.Elimina ting chronic Staph aureus carriage.either wilh intern1iltent cycles of ora l rifampi n and intranasal bacitracin (8) or more reccnlly with intermittent or continuous intra n asal mupirocin (10.L 1). h as been s uggested to be usefu l in rcducin~ the incidence of bacteremia due to this organism.
Body site selected for ven ous access has been shown to be an imporiant variable.Femora l a ccess sites shou ld be avoided.The authors avoid femora l access if possib le. a nd as a consequence saw only one bacteremia in a patient dialyzing throu~h this s ite.Increased frequency of ma nipula tion of the cathete r junction sites -for example , when the catheter is used for the administration of drugs , Ouids or blood products-is a lso felt to be a risk factor and s hould likewise be avoided (12).Fina lly. the type of dressing a pplied to the cannula h as rcccnlly been shown to be an important factor in increasing the risk or infection.Transparent semiocclusive dressings have been s hown to increase the multiplication of bacteria under the dressing a nd lead to a n increased ris k of catheter infection ( 13) .

Figure 1 )
Figure 1) Bacteremias in hemodialysis patienLs (rom August 1986 to .June 1988 at the Urtil'ersity of Alberta Hospitals dialysis centre Prophylactic antibiotics are not administered prior to line insertion.but may be given if a concurrent infection is present elsewh ere.eg.fistula infection.The line is used exclusively for dialysis and is flushed with 2000 to 3000 units of heparin at the time of insertion and after each dialysis run.Transparent semiocclus ive dressings are applied and changed after each run and when the site is inspected.Povidone-iodine ointment is applied to central line insertion s ites at the lime or dressing change.The catheter is removed when no longer required for hemodialysis or if there is catheter malfunction.thrombosis or evidence of local (pus or erythema) or systemic infection.Routine changing of the subclavian line.e ither by reinsertion or by passing over a guidewire to the same site, is not undertaken.
on Anlimicrobial Agents and C hemotherapy.Los An~cles .Califomia.October 1988: 157.8. Yu VL.Goelz A. Wagen er ryi.et al.SLaphylococcus aureus nasal carriage and infection in patients on h emodialysis.N Eng! J Med 1986:315:9 1-6.9. Haplowitz L. Com stook J. Landwehr D. Dalton II.Mayhall C. Prospective study of microbial colonization of the nose and skin and infection of l he vascular access site in hemodialysis patients.J Clin Microbiol 1989 :26:1257-62.10.Boelaert JR.DcBaer e Y. Godard C. Van Landuyt I rw.Eradication of Staphylococcus au reus in dialysis by n asal mupirocin.Program and Abstracts of the 29th lnterscien ce Conferen ce on Antimicrobial Agents a:1d Ch emotherapy.Hou ston.Texas.September 1989:3 15.I I .Holton D. Nic-o lle LE.Diley D. Bernstein K. Efficacy of mupirocin nasal ointmen t in eradica ti ng Stapltylococcus aureus in chronic hemodialysis patients.Pro~ram and Abstracts of the 29th Interscience Con ference on Antimicrobial Agents and Chemotherapy.Houston.Texas.September 1989:3 15. t 2. Maki DG.Sepsis a rising from extrinsic contamination of the infusion and measu res for control: In : Philips I. ed.Microbiological llazards of Infusion Therapy.Lan caster : MTP Press.1977:99-14 1. 13. Conly J. Grieve I<.Peters B. A prospec tive r andomized study comparing transparent and dry gauze dressings for central venous ca theters.