Aims: To assess the potential benefit of withdrawing or flushing away the heparin lock before collecting blood for culture from a central venous catheter.
Methods: 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.
Results: 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.
Conclusions: 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.