Phlebotomy – Tourniquet Use & Venipuncture Technique

Tourniquet Types & Rationale

• Standard single-use latex or elastic strip ("Menage")
  • Cheap, disposable → can be discarded if blood-soiled, reducing cross-contamination risk.
• Reusable plastic buckle tourniquet
  • Advantages: quick click-lock & one-hand release.
  • Drawback: difficult to disinfect if blood contacts the surface; sits directly on patient skin → potential fomite for pathogens.

Correct Tourniquet Placement

• Hold strip at midpoint, stretch, wrap around arm, cross ends.
• Create a half-loop tuck under the knot using one finger, then release stretch so band sits snugly.
• Tightness check: should be firm enough to engorge veins but not painful or occlusive of arterial flow.
• Time limit: remove within \le 1\text{ min} to avoid altering lab values (hemoconcentration).

Physiologic Effect of a Tourniquet

• Arterial inflow continues; venous outflow is impeded.
  • Veins distend → easier visualization/palpation.
• Small components (platelets, plasma) can leak past the restriction; larger components (RBC, WBC) pool.
• Prolonged stasis → hemoconcentration (↑ RBC, WBC counts, altered chemistry results).
  • Leads to falsely elevated lab values if specimen drawn under these conditions.

Syringe & Needle Setup

• Components: barrel, plunger, needle.
• Opening technique: peel mid-package, leave sterile half-sheathed on table until patient ready.
• Pre-check for manufacturing defects: bent shaft, metal burrs, occluded bevel.
• Plunger "break":
  • Before venipuncture, release initial adhesive seal by pulling/pushing once to ensure smooth motion with minimal force.
  • Prevents sudden jerks that could dislodge needle.
• Remove needle cap immediately before use; bevel inspection.

Vein Identification

• Use tapping/palpation rather than constant pressure.
• Evaluate BOTH:
  • Visibility – can you see a blue cord?
  • Palpability – does it feel bouncy, resilient?
• Prioritize palpability if you must choose; visible but non-palpable structures may be superficial capillaries.
• Trace vein course (direction) after locating midpoint.

Skin Antisepsis

• Tear open alcohol pad, lock pad between thumb–index to prevent fluttering.
• Scrub from intended stick site outward in concentric circles; do NOT zig-zag.
• Allow to air-dry; do not fan, blow, or blot → avoids re-contamination.

Needle Orientation & Bevel Rule

• The slanted opening (bevel) must face upward when penetrating skin.
• Facilitates smooth entry and visualization of flash.

Recommended Hand & Grip Mechanics

• Dominant hand: holds syringe like a dart – thumb on plunger flange, index–middle around barrel for stability.
• Three fingers of same hand rest lightly on patient’s arm to steady.
• Non-dominant hand: anchors (stretches) skin below insertion site, keeping vein immobile.
• Once cap removed, syringe should never leave dominant hand (treat as “live weapon”).

Insertion Angle Guidelines

• Right angle reference: 90^\circ.
• Preferred range: 15^\circ \text{ – } 30^\circ relative to skin.
  • Superficial vein: lower angle (≈ 15^\circ) to avoid through-and-through puncture.
  • Deeper vein: higher within range (≈ 30^\circ) to reach lumen.
• Excessive angle → unstable; minor patient movement may pull needle out.

Entering the Lumen & Flash Recognition

• Penetrate skin, advance until bevel fully inside vessel.
• Observe syringe hub for flash of blood (tiny red dot) indicating intraluminal placement.
• Stabilize hand, then draw plunger smoothly.

Drawing the Specimen

• Maintain anchor until bevel seated, then slowly release skin to avoid needle displacement.
• Withdraw required volume; avoid creating vacuum bubbles.
• Remove tourniquet immediately once blood flows if not already released.

Post-Draw Care & Hemostasis

• Withdraw needle along same angle.
• Bring gauze quickly: needle clear of arm → apply firm pressure ≥ 10 s.
• Hand gauze to patient to maintain pressure.

Sharps Disposal Protocol

• Dispose needle & syringe together into approved sharps container.
  • Do not push fingers beyond container opening.
  • Let device fall; never force or attempt to “dart” throw ➔ prevents bounce-back injuries.

Safety Needle Devices

• Some needles feature a retractable or slide-over shield that automatically covers bevel when removed from vein; engage immediately if present.

Practical Tips & Common Pitfalls

• If vein palpable without tourniquet, skip tourniquet to improve result accuracy.
• Avoid switching dominant ↔ nondominant hands mid-procedure.
• Never re-cap used needles.
• Monitor patient for dizziness, syncope – be prepared with chair/support.

Connections & Foundational Principles

• Builds on prior anatomy lesson: differentiating arterial vs venous flow, vessel wall properties.
• Reinforces infection-control fundamentals (aseptic technique, disposal hierarchy).
• Demonstrates ergonomic principles (body mechanics, hand stabilization) discussed in earlier skills labs.

Real-World / Ethical Considerations

• Single-use disposables minimize cross-patient infection, aligning with duty of non-maleficence.
• Accurate lab results critical for diagnosis; avoiding hemoconcentration maintains data integrity and patient safety.
• Respect patient comfort: prompt release of tourniquet, minimal repositioning, clear communication.