Venipuncture Technique: Syringe Method and Butterfly (Winged Infusion) Set

Why Alternative Collection Devices Exist

The standard evacuated tube system (ETS) works well for most adult patients, but the vacuum pressure inside collection tubes can collapse small, fragile, or rolling veins before enough blood is drawn. Two devices solve this problem: the syringe method and the butterfly (winged infusion) set. Selecting the right device for the right patient is a clinical judgment that directly affects specimen quality and patient comfort.

The Syringe Method

A syringe consists of a barrel, plunger, and attached needle (typically 21–23 gauge). The collector controls suction manually by pulling the plunger slowly and steadily. Because you set the negative pressure yourself, you can reduce it instantly if the vein begins to collapse.

When to use a syringe:

• Small or fragile veins in elderly patients
• Patients with difficult, rolling veins
• Situations where a butterfly is not available

Key technique points:

1. Pull the plunger slowly and evenly — jerking creates turbulence that hemolyzes red cells.

2. Fill only what you need; overfilling makes safe transfer harder.

3. After collection, activate the needle safety device immediately.

4. Use a syringe transfer device (a hub that accepts evacuated tubes) to move blood from the syringe into tubes. Never remove the tube stopper and pour blood in — this causes hemolysis and aerosol exposure.

5. Transfer blood in the correct order of draw and allow the vacuum to pull blood from the syringe rather than forcing the plunger, which can cause hemolysis.

6. Never recap the needle after use. Dispose of the entire syringe-and-needle unit (or the needle alone after the safety device engages) directly into a sharps container.

The Butterfly (Winged Infusion) Set

A butterfly set consists of a short bevel needle (commonly 23 gauge for routine draws; smaller gauges exist for pediatric use), two plastic wings for gripping, flexible tubing, and a Luer adapter that connects to either an ETS holder or a syringe. The tubing gives the needle more freedom of movement, making it ideal for:

• Hand and wrist veins
• Pediatric or small veins
• Elderly patients with fragile or superficial veins
• Patients with an IV line in the dominant arm requiring the non-dominant hand or wrist

Dead-space consideration: The tubing holds a small volume of air. If the first tube is an additive tube (e.g., a citrate tube for coagulation studies), that air can enter and alter the blood-to-additive ratio. Always fill the dead space with blood before the first additive tube by briefly filling a discard tube (or a small plain red-top tube) first. Check your facility's policy — some protocols omit the discard tube for non-coagulation draws.

Butterfly technique — step by step:

1. Assemble equipment: wings open flat, tubing untangled, Luer adapter attached to ETS holder or syringe.

2. Apply tourniquet, identify vein, cleanse site, and allow to dry.

3. Anchor the vein. Hold the wings together ("pinch" grip) and insert at a 10–15° angle, bevel up.

4. Watch for the flashback of blood entering the tubing — this confirms venous access.

5. Lower the angle to almost flat and advance slightly.

6. Stabilize the wings against the skin (tape if needed for multi-tube draws).

7. Insert a discard tube or appropriate first tube per order of draw.

8. Release tourniquet before or as the last tube fills; remove the last tube before withdrawing the needle.

9. Withdraw the needle, activate the safety device immediately (most sets have a retractable sheath or click-shield), apply gauze and pressure.

10. Dispose of the entire butterfly assembly directly into a sharps container — do not recap.

Order of Draw and Transfer

Order of draw applies equally to syringe and butterfly collections. When using a transfer device, fill tubes in the same sequence used for ETS draws: sterile/blood culture first, then citrate (light blue), then serum (red/gold), then heparin (green), then EDTA (lavender), then oxalate/fluoride (gray). Gentle inversion after each tube mixes additives; check each tube's required inversions.

Safety Rules — Non-Negotiable

• No recapping. Needlestick injuries most often occur during recapping. Activate the safety device with one hand and go straight to the sharps container.
• Inspect equipment. Check needle gauge, syringe expiration, and tubing integrity before every draw.
• Manage tubing kink. A kinked butterfly tube stops blood flow and may cause the patient to feel increased pressure; straighten gently without withdrawing the needle.
• Scope of practice. You are collecting a specimen, not starting an IV. Do not inject fluids or medications through a butterfly set during a phlebotomy draw.
• Standard precautions apply at all times: gloves on before patient contact, eye protection if splash risk exists.

Device Selection Summary

| Patient Scenario | Recommended Device |

|---|---|

| Standard adult antecubital | ETS (21g) |

| Elderly fragile antecubital vein | Butterfly 23g or syringe |

| Hand or wrist vein | Butterfly 23g |

| Pediatric small vein | Butterfly 23g (or smaller per policy) |

| IV in dominant arm | Butterfly 23g on opposite hand/wrist or other site per policy |

| Obese patient, deep vein | ETS long needle or syringe |

Matching device to patient protects vein integrity, reduces hemolysis, and supports accurate lab results — all of which affect patient care decisions downstream.