Blood culture is not a ‘routine’ procedure. Best results will be obtained is withdrawn and inoculated carefully, without hurry, following the procedure outlined below
Indication
- Blood cultures are usually requested for patients with fever, rigors and other features of systemic infection.
- Where possible, they should be collected at, or very shortly after a temperature ‘spike’ and prior to starting antibiotic treatment
Contraindications
- Never choose the AV fistula arm of a renal dialysis patient.
- Never place a tourniquet on the arm of a patient with lymphoedema.
- Proximally sited IV drip with running line.
Equipment
- Tourniquet
- Alcohol swab x 8
- Syringes: 5mL x 1; 10mL x 4
- Butterfly or alternative IV cannula
- Needles: 18G x 4
- Sticking plaster
- Correct blood culture bottles (anaerobic and aerobic) x 2
- Sharps container
- Absorbent pad or ‘bluey’
Procedural technique
- Identify the patient and explain the procedure
- Prepare and position the patient for venepuncture, either in a comfortable chair or reclining on a bed.
- The alert and conscious patient will usually inform you of the best arm to use.
- Put on non-sterile gloves.
- Remove plastic shields from the top of each blood culture bottle without touching the rubber septum.
- Wipe the top of each bottle with an alcohol swab and allow to dry
- Select an appropriate vein, and apply the tourniquet 10–15 cm proximal to the chosen site. Palpate the vein and identify its position carefully. Prepare the skin surface with an alcohol swab, moving from the centre outwards.
- Repeat the process with a second alcohol swab and allow to air dry for 1 minute
- Without retouching the vein, cannulate and withdraw a small volume with the 5mL syringe and discard into the sharps container. Use the 10mL syringes to withdraw blood samples, using one syringe for each bottle.
- Undo the tourniquet, withdraw the needle and apply firm pressure with a dry swab to the venepuncture site.
- Insert the needle into the sterile septum of the blood culture bottle and inject at least 5 mL of blood, starting with the aerobic bottle. Withdraw the needle and repeat for the anaerobic culture bottle.
- Dispose of used sharps immediately in the sharps container.
- Label blood culture bottles with the patient’s name, ward, date, time AND site of venepuncture.
- Repeat the procedure on the other arm if two sets of cultures are required (such as for suspected infective endocarditis
Handy Hints
- Do not touch or palpate the vein after swabbing, unless there is difficult venous access, in which case adopt full aseptic technique with sterile gloves and field.
- It is unnecessary to replace the needle after withdrawing blood and prior to inserting it in the culture bottles. This increases the risk of needle-stick injury and contamination.
- Avoid placing a label over the barcode of the blood culture bottles.
- Avoid inoculating blood culture bottles as the last in line of a series of routine investigations. There will be a low rate of genuine positive results, and a high false positive rate due to skin contaminants.
- Avoid inoculating blood culture bottles with 20mL syringes. They are more likely to contaminate the cultures and are prone to overfilling the cultures if allowed to discharge passively.
- Neutropaenic haematology and oncology patients often have CVC line-associated bacteraemia. It is helpful to collect one blood culture set via the CVC line and one from a peripheral vein to distinguish line-associated infection from other sources of systemic infection.
- Suspected infective endocarditis – carefully collect three sets of blood cultures from peripheral veins at regularly spaced intervals. Remember to accurately document the time of venesection on the blood culture bottles, request and continuation notes.
- If very small quantity available (e.g. 5mL total) inoculate all into one aerobic bottle, and note “difficult venesection” on lab request.
- If less than 3mL (shocked patient, paediatric patient) inoculate all into a paediatric blood culture bottle.
About Mike Cadogan
