Blood cultures at central line insertion in the intensive care unit: comparison with peripheral venipuncture

Blood cultures are a key diagnostic test for intensive care unit (ICU) patients; however, contaminants complicate interpretations and lead to unnecessary antibiotic administration and costs. Indications for blood cultures and central venous catheter (CVC) insertions often overlap for ICU patients. Obtaining blood cultures under the strict sterile precautions utilized for CVC insertion might be expected to decrease culture contamination. This retrospective study compared the results of blood cultures taken at CVC insertion, at arterial line insertion, and from peripheral venipuncture in order to validate the advantage of CVC insertion cultures. Cultures from indwelling lines were excluded. Results of 14,589 blood cultures, including 2,736 (19%) CVC, 1,513 (10%) arterial line, and 10,340 (71%) peripheral cultures taken over 5.5 years in two ICUs (general and medical) were analyzed. CVC cultures were contaminated more frequently than arterial line or peripheral cultures (225/2,736 [8%] CVC, 48/1,513 [3%] arterial line, and 378/10,340 (4%) peripheral cultures [P < 0.001 for CVC versus peripheral and CVC versus arterial line cultures]). True pathogens were found more frequently in CVC insertion cultures (334/2,736 [12%] CVC, 155/1,513 [10%] arterial line, and 795/10,340 [8%] peripheral cultures [P < 0.001 for CVC versus peripheral cultures; P = 0.055 for CVC versus arterial line cultures; P < 0.001 for peripheral versus arterial line cultures]). Contamination and true-positive rates were similar for culture sets from the two ICUs for each given culture source. Despite superior sterile precautions, cultures taken at the time of central line insertion had a higher contamination rate than did either peripheral or arterial line blood cultures. This may be related to the increased manipulations required for CVC insertion.