Venepuncture, blood cultures and arterial blood sampling

Prepare the exact request, labels, specimen tubes, sterile single-use needle and holder or winged set, tourniquet, approved antiseptic, gauze, dressing, gloves, tray and sharps bin within reach. Check identity, allergies to adhesives or antiseptics, previous difficulty, fistula, lymph-node surgery, vascular devices, anticoagulation and fainting. Explain purpose and alternatives and position safely.

Use hand hygiene and clean gloves for venepuncture, adding PPE for splash risk. Select a palpable straight vein away from infection, haematoma and arterial pulsation; avoid restricted limbs according to local policy and seek help rather than repeated blind attempts. Apply the tourniquet only as long as necessary. Palpate before antisepsis, then clean and allow full drying; do not repalpate unless asepsis is restored.

Anchor the skin without contaminating the site, insert bevel up at a shallow angle until flashback, lower and advance only enough to stabilise. Attach tubes without moving the needle and follow the local laboratory order of draw and fill requirements. Release the tourniquet once flow is established and before needle removal. Ask the patient not to pump the fist because it changes analytes.

Withdraw smoothly, apply gauze pressure and activate the engineered safety feature immediately. Put the sharp directly into the nearby bin without passing, bending or resheathing. Invert additive tubes gently as manufacturer and laboratory require; do not shake. Label beside the patient with identifiers, date, time and collector, confirm against the wristband or spoken details, and send under local stability rules.

A failed attempt should not become persistent probing. Stop for electric-shock pain, paraesthesia, swelling, pallor, arterial-looking pulsatile flow, severe distress or presyncope. Remove, compress and reassess. Respect the organisation’s maximum-attempt policy and call a more experienced practitioner or vascular-access service. After fainting, lie the patient safely and assess rather than continuing upright.

Blood-culture equipment adds the correct adult or paediatric bottles, bottle-septum antisepsis and the local closed collection adapter. Verify number of sets, volume and order against current laboratory instructions because bottle systems differ. Inspect expiry, damage and fill markers. Do not cover the bottle barcode or remove detachable identifiers incorrectly.

Obtain cultures promptly when bloodstream infection is suspected, ideally before antimicrobials, without delaying urgent treatment in severe sepsis. NHS England recommends two adult sets: two aerobic and two anaerobic bottles, usually 8–10 mL in each according to the bottle instructions. Four bottles at a specified 10 mL target give 40 mL total; four at 8 mL give 32 mL. The report identifies at least 40 mL as optimal for adult detection. Paediatric volumes require a separate age/weight and bottle-specific plan.

Disinfect bottle tops and skin with the specified agent and contact time, then allow drying. Maintain non-touch technique for the venepuncture key parts. Draw separate sets from separate peripheral sites where feasible. A culture from a vascular line may answer catheter-infection questions only when paired and timed according to protocol; routine line draws increase contamination and can confuse interpretation.

Label each culture with site, date, time and collector and transport without avoidable delay; do not refrigerate unless the laboratory explicitly instructs. Document antimicrobial timing. Report difficulty, low volume or line collection because interpretation changes. Contamination can expose the patient to unnecessary antibiotics, line removal and admission, so technique is diagnostic stewardship.

Arterial sampling requires a pre-heparinised self-filling syringe, appropriate needle with safety device, antiseptic, gauze, secure cap, PPE and immediate analyser or transport arrangement. Check indication, oxygen concentration and recent change, bleeding risk, local collateral-circulation assessment, anatomy and ability to cooperate. Avoid an infected site, compromised circulation, fistula or vascular graft and seek expert help after failed attempts. Use local anaesthesia for arterial blood-gas sampling except in an emergency where it would delay necessary care.

Position the wrist slightly extended without hyperextension. Palpate the radial artery with the non-dominant hand, clean and dry the site, and insert bevel up at a typical 45-degree angle for adult radial puncture, adjusted to the assessed anatomy and supervised technique while keeping fingers off key parts. Arterial pressure should fill the syringe without forceful aspiration. Take only the volume required by the analyser and withdraw at once if severe radiating pain or paraesthesia occurs.

Apply firm uninterrupted pressure immediately. WHO describes assessing haemostasis after 2–3 minutes, with 5 minutes or longer potentially needed in anticoagulation, hypertension or a bleeding disorder. Continue until bleeding stops and reassess distal circulation; elapsed time alone does not establish safety. Expel visible air without spraying, engage safety, use the approved cap and mix to distribute heparin. Analyse promptly and document oxygen device or FiO2 and other required sample conditions.

Interpret arterial blood gas systematically: pH, PaCO2, bicarbonate/base excess, oxygenation and lactate, linked to clinical context and supplemental oxygen. Air contamination can raise PaO2 and lower PaCO2; delay permits cellular metabolism to lower oxygen and pH and raise carbon dioxide. A venous sample masquerading as arterial can mislead oxygenation assessment.

After sampling, inspect haemostasis, distal colour, warmth, capillary refill, pulse, sensation and movement. Warn about bruising and delayed bleeding. Urgently review an expanding haematoma, persistent bleeding, cool painful hand or neurological change. Communicate critical results immediately and record collection site, oxygen, complications and action.

After a sharps injury, encourage bleeding without aggressive sucking, wash with soap and water, irrigate mucosa, report immediately and follow occupational-exposure protocol for risk assessment and time-critical prophylaxis. Do not conceal the event. Review device, environment and workflow to prevent recurrence.