Catheter-drawn blood cultures: is withdrawing the heparin lock beneficial?

Abstract

To assess the potential benefit of withdrawing or flushing away the heparin lock before collecting blood for culture from a central venous catheter. We compared the contamination rates of 152 pairs of blood samples aspirated from central venous catheters in afebrile renal dialysis or cancer patients. We also assessed the antimicrobial effect of 2000 U of heparin in Bactec Plus Aerobic/F culture bottles inoculated with a volunteer's blood plus one of six common bloodstream pathogens. There was no significant difference in contamination rates between first-drawn (26 of 152, 17.1%) and second-drawn (24 of 152, 15.8%) samples. There was no significance difference in yield (58 of 60 [97%] versus 52 of 53 [98%]) or time to flagging positive (16.6 versus 16.7 h) between the bottles with and without heparin. Our results do not support the practice of withdrawing or flushing away the heparin lock before collecting blood for culture from a central venous catheter.