All procedures
GMC #05/Diagnostic procedures taught from Y3
Blood cultures
Take samples of peripheral venous blood to test for the growth of infectious organisms.
Target · Perform under supervision0% ready
Do it on a patient with a supervisor observing you (GMC “direct supervision”).
Overview
Aseptic non-touch technique (ANTT) is everything — contamination causes false positives, unnecessary antibiotics and prolonged admissions. Take before antibiotics wherever possible (Sepsis Six).
Key numbers
- Fill each bottle with 8–10 mL blood — under-filling reduces sensitivity; inoculate aerobic then anaerobicUK SMI / manufacturer
- Infective endocarditis: 3 sets from separate venepuncture sites, ideally spaced over timeBSAC / ESC-informed UK practice
- Take before antibiotics where possible — but never delay antibiotics in septic shockNICE NG51 (sepsis)
Indications
- Suspected bacteraemia / sepsis
- Pyrexia of unknown origin
- Suspected infective endocarditis (multiple sets from different sites)
Contraindications & cautions
- Do not delay antibiotics in septic shock to obtain cultures if access is difficult
Equipment
Aerobic + anaerobic culture bottlesANTT pack, 2% chlorhexidine/70% alcohol wipesNeedle & holder / winged collection setSharps bin
Step by step
Prepare (ANTT)
- 1Wash hands, apron/gloves; assemble sterile field
- 2Palpate and select the vein, then clean the skin for 30 seconds and let it dry fully — do not re-palpate afterwards
- 3Clean the bottle tops and let dry
Collect
- 1Take blood (typically 8–10 mL per bottle for optimal yield)
- 2Inoculate the bottles without changing the needle; avoid introducing air into the anaerobic bottle
- 3Label at the bedside with time and site
After
- 1Dispose of sharps immediately; document; send promptly to the lab
- 2For endocarditis: ≥2 sets from separate venepuncture sites, ideally spaced
Complications
- Contamination → false-positive (skin flora, e.g. coagulase-negative staph)
- Standard venepuncture risks: haematoma, vasovagal
OSCE tips
- ANTT + “don’t re-palpate after cleaning” is the single biggest marks source.
- Correct fill volume (8–10 mL) matters for yield — don’t under-fill.
- Before antibiotics; 3 sets for endocarditis.
Read
Sources & credits
Authored to UK finals standard and verified against UK guidance (UK SMI · BSAC · NICE NG51 (sepsis)) and Geeky Medics OSCE guides . Southampton teaching materials © University of Southampton. Always follow current local policy.