title: The use of the arterial line as a source for blood cultures.
abstract: OBJECTIVE
  To determine the reliability of blood cultures obtained through indwelling arterial lines as compared to that of blood cultures obtained by venipuncture.
  
  
  METHODS
  A prospective observational study.
  
  
  METHODS
  Six-bed mixed medical surgical intensive care unit (ICU) of a 550-bed university-affiliated medical center.
  
  
  METHODS
  During a 3-month period blood culture sets, when clinically indicated, were drawn in parallel from indwelling arterial catheters and one-time venipuncture and the results compared. Each blood sample consisted of 15 ml and was distributed equally between three blood culture bottles: aerobic, anaerobic and one aerobic resin-containing bottle. Blood culture results from the two sources were compared according to preset definitions.
  
  
  RESULTS
  During the study period 90 parallel blood culture sets (540 bottles) were obtained from 36 patients. Forty-three (16%) venipuncture bottles were positive versus 88 (32%) arterial line culture bottles (p < 0.001). Of the parallel sets, 83% yielded equivalent results - either both sterile or both growing the same organism. Amongst the discordant sets, the arterial line cultures grew 37 gram-positive and 18 gram-negative isolates not found in venipuncture sets (i.e. 50% of 109 arterial line isolates), while only two gram-positive isolates were solely grown in venipuncture cultures (4% of all 55 venipuncture isolates, p < 0.001). On clinical correlation, all the gram-positive organisms in the discordant cultures were found not to reflect bacteremia, while five of the 18 gram-negative isolates (28%) grown only in arterial line cultures probably did reflect ongoing bacteremia.
  
  
  CONCLUSIONS
  The results of blood cultures taken from the arterial line are frequently equivalent to those taken from venipuncture. When discordant, the growth of gram-positive bacteria almost certainly reflects contamination or arterial line colonization, whereas the growth of gram-negative bacteria may have to be considered as reflecting bacteremia.
authors.affiliation: Infectious Diseases Unit, Shaare Zedek Medical Center, Jerusalem, Israel.
authors.forename: P D
authors.initials: PD
authors.lastname: Levin
authors.forename: M
authors.initials: M
authors.lastname: Hersch
authors.forename: B
authors.initials: B
authors.lastname: Rudensky
authors.forename: A M
authors.initials: AM
authors.lastname: Yinnon
mesh_terms: D016470:Bacteremia / Q000175:diagnosis*; D001431:Bacteriological Techniques; D001800:Blood Specimen Collection / Q000379:methods; D002405:Catheterization, Central Venous; D002406:Catheterization, Peripheral; D002408:Catheters, Indwelling / Q000382:microbiology*; D016009:Chi-Square Distribution; D015169:Colony Count, Microbial; D004866:Equipment Contamination; D006801:Humans; D007362:Intensive Care Units; D011446:Prospective Studies; D018805:Sepsis / Q000175:diagnosis