Blood cultures

Strict asepsis. So important to do this right as a skin contaminant can end up with a patient having to stay on prolonged antibiotics for a blood infection they don't have

Introduction

• Blood cultures often done as part of a sepsis screen along with urine culture, chest X-ray, sputum culture and further serology as part of a septic screen.
• Indicated when a patient has had a fever, rigors, sweats, delirium, other signs of sepsis. Some patients with bacteraemia may not be febrile
• Send Two bottles one is prepared for aerobes and the other anaerobes.
• Very good skin asepsis is needed with chlorhexidine or alcohol to avoid contamination with coagulase-negative Staphylococcus spp. (such as S. epidermidis).
• Only 5 mL of blood is needed for each bottle, but more than 20 mL is preferred to increase your chance of culturing any circulating bacteria.
• The aerobic container is the more important if blood limited.
• Label the bottles but do not cover barcodes and send them to the laboratory urgently.
• Peel off the miniature barcode and apply to the patient medical records.

Special situations

• Oncology and Haematology patients may have long-term vascular access such as a central venous catheter (CVC) or port so attempt to send off one set of cultures drawn through this site, and one elsewhere (e.g. a peripheral upper limb vein).
• The more cultures taken, the higher the yield supported best by studying cases of infective endocarditis, where a minimum of three cultures (more if you can) should be sent BEFORE antibiotics given.

Results

• Cultures results take at least 24 hours even longer
• Microbiology may call you to notify you of a positive culture.
• False positives are not uncommon and take expert advice

Practicalities

• Wash hands, ensure name badge visible
• Introduce yourself, ensure correct patient
• Ask if you may take a blood sample
• Explain why it is necessary
• Ensure verbal consent obtained

Equipment

• Sterile Gloves, Tourniquet, Alcohol wipes or equivalent
• Green needle and syringe and vacutainers

Technique

• Place tourniquet around the upper arm and wait until veins dilated
• Find a decent vein often in the forearm
• Clean the skin with several alcohol wipes - some say up to 5
• Avoid touching the skin again
• Insert the needle into the vein and watch for flashback
• Fill the syringe and inject into culture bottles
• Before removing the needle release the tourniquet
• Remove the needle and apply pressure with a cotton wool ball or gauze
• Wait until haemostasis achieved and apply plaster if needed
• Thank patient

Finally

• Dispose of sharps
• Label bottles at bedside with patient identifiers
• Answer any questions from patient

Complications

• Failure: try 2-3 times and if failing ask for help or come back later
• Haematoma: usually because needle removed from a vein before tourniquet removed
• Arterial puncture: remove needle and apply pressure