3.1 Patient Assessment and Preparation

3.1 Patient Assessment and Preparation

Quick Answer: Before any draw, confirm identity and order, screen for latex/adhesive allergy, bleeding risk, mastectomy/lymphedema, fistula/graft, IV lines, fasting, and recent exercise; choose an appropriate gauge (commonly 21 g adult ETS, 23 g butterfly for difficult veins); position the patient safely; plan tourniquet time ≤1 minute; and escalate or defer when restrictions, instability, or failed attempts make collection unsafe.

Domain I expects the Medical Laboratory Assistant to do more than stick a vein. Collection quality starts with a deliberate pre-draw assessment: the right patient, the right preparation, the right equipment, and a plan for limbs or conditions that change the approach. Errors at this step drive recollections, delayed diagnosis, and patient harm.

/practice/ascp-mlaPractice questions with detailed explanations

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Why Pre-Collection Assessment Matters

Laboratory results are only as good as the specimen. Many “mystery” chemistry or hematology flags are actually preanalytical: wrong arm on a post-mastectomy patient, non-fasting lipids drawn as fasting, exercise-driven potassium spikes, or a prolonged tourniquet that concentrates analytes. The MLA’s job is to surface these risks before the needle goes in, document what the patient reports, and follow facility policy when collection should wait.

Assessment is not a long interview. It is a focused safety checklist done after identification and order review, while assembling supplies and positioning the patient.

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Clinical History and Condition Screen

Allergies: latex and adhesives

Ask about latex (gloves, tourniquets, some bandages) and adhesive (tape, bandage strips). For latex allergy, switch to non-latex gloves and tourniquets and avoid latex-containing supplies. For adhesive sensitivity, use paper or other hypoallergenic tape and apply pressure with gauze rather than aggressive adhesive dressings when policy allows. Document the allergy in the collection record if your LIS or paper requisition captures it, and flag recurring issues so future collectors avoid the same materials.

Bleeding disorders and anticoagulation

Patients on warfarin, DOACs, heparin, dual antiplatelet therapy, or with hemophilia, thrombocytopenia, or liver disease may bleed longer after venipuncture. That does not automatically cancel a needed draw, but it changes aftercare:

• Apply firm pressure longer than the usual 1–2 minutes (often 3–5 minutes or until hemostasis is confirmed).
• Do not “wave them out” until the site is dry and stable.
• Prefer sites that are easy to compress; avoid deep, hard-to-monitor punctures when alternatives exist.
• Report unexpected prolonged oozing or expanding hematoma per policy.

Never discontinue a patient’s anticoagulant on your own—only a licensed provider manages medications.

Mastectomy, lymph node dissection, and lymphedema

Same-side (ipsilateral) arm draws after mastectomy or axillary lymph node dissection are generally avoided because of infection risk and lymphedema risk. Prefer the contralateral arm. For bilateral mastectomy or when both arms are restricted, do not invent a site—escalate to the nurse or ordering provider for an approved alternative (hand veins, foot veins only if authorized, or capillary if the test allows). Document the restriction and the approved plan.

Fistulas, grafts, and vascular access devices

Arms with AV fistulas or grafts are dialysis lifelines. Do not place a tourniquet on or draw from that arm. Use the opposite arm or another approved site. Ports, PICC lines, and central lines are not routine MLA draw sites unless you are trained and authorized under facility protocol with nursing/physician involvement.

Fasting status

Common fasting tests include fasting glucose, lipid panels, and some metabolic workups. Typical adult fasting is 8–12 hours of no caloric intake (water usually allowed; confirm facility/test-specific rules). If the patient ate recently:

• Check the order and lab policy—some tests can proceed with “non-fasting” documentation; others must be rescheduled.
• Do not relabel a non-fasting specimen as fasting.
• Note last food/drink time when required.

Recent exercise, stress, and other physiologic factors

Strenuous exercise can raise potassium, CK, LDH, and other muscle-related analytes and may affect WBC counts. Extreme anxiety or crying (especially in children) can alter white cell and glucose patterns. When clinically relevant and policy-directed, note recent vigorous exercise and follow guidance on delaying non-urgent draws. Hydration status and posture (lying vs sitting) can also shift some chemistry values—standardize position when possible.

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Needle Gauge Selection

Gauge number is inverse to diameter: higher number = thinner needle.

Butterfly (winged infusion) sets improve control on rolling or small hand veins and for patients who cannot fully extend the arm. Drawbacks include extra tubing dead space (important for light-blue coagulation tubes—use a discard tube when indicated) and higher cost. Match tube size to vein quality: a tiny vein plus a large vacuum tube increases collapse and hemolysis.

Select gauge based on vein size, patient age, volume needed, and test type—not personal habit alone.

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Patient Positioning and Safety Setup

• Prefer a phlebotomy chair with an armrest, or a bed with the arm fully supported. Never draw a standing patient for routine venipuncture (syncope risk).
• Arm should be straight or slightly bent, palm up for antecubital access, below heart level when practical to aid venous filling.
• Remove bulky clothing from the collection arm; do not force a tight sleeve to act as a tourniquet.
• Have gauze, tape or bandage, sharps container within reach, and tubes organized in order of draw before puncture.
• For patients with a history of fainting, recline them and stay close; know your facility’s syncope response.

Explain the steps briefly: “You’ll feel a small stick; keep your arm still.” Consent and age-appropriate communication are covered in Chapter 2—assessment includes noticing language barriers, cognitive impairment, or combativeness that requires a second staff member.

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Tourniquet Time Awareness (Introduction)

Apply the tourniquet 3–4 inches above the intended site, tight enough to engorge veins but not so tight that the arterial pulse is lost. CLSI-aligned practice limits effective tourniquet time to about 1 minute. Prolonged tourniquet use causes hemoconcentration (false elevation of proteins, cells, and some analytes) and increases hemolysis risk.

Practical workflow:

1. Apply tourniquet → select vein → release if prep will take longer.
2. Cleanse site and allow alcohol to air dry.
3. Reapply briefly just before puncture if needed, then release as soon as blood flow is established (or within the 1-minute window).

Full additive and order-of-draw detail is in Section 3.3; the assessment habit is simply: watch the clock and do not leave a tourniquet on while hunting endlessly for a vein.

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When to Escalate or Defer Collection

Stop and escalate (nurse, supervisor, pathologist/lab director pathway, or ordering provider per policy) when:

• Two unsuccessful attempts (common facility limit) without success—do not “keep trying.”
• Only available sites are restricted (bilateral mastectomy, double fistulas, severe burns) without a documented alternative plan.
• Patient refuses, becomes combative, or lacks capacity and no authorized decision-maker process is in place.
• Patient is hemodynamically unstable, actively seizing, or needs emergency care first.
• Required fasting, timed draw window, or special prep was not met and the test cannot be reported as noncompliant.
• Order discrepancies, missing identifiers, or wrong patient data (Chapter 2) remain unresolved.
• Suspected arterial stick, severe nerve pain (electric shock), or expanding hematoma during collection—release tourniquet, withdraw needle, apply pressure, and follow adverse-reaction protocols (Chapter 4).

Deferring a non-urgent draw is safer than producing a wrong-site or wrong-prep specimen. Document the reason, who was notified, and any reschedule instructions.

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Mini Workflow: Assessment to Ready-to-Stick

1. Identify patient (two identifiers) and match to order.
2. Review tests for special prep (fasting, timed, ice, light protection).
3. Screen allergies, limb restrictions, bleeding risk, IVs, and access devices.
4. Choose arm/site plan; select needle system and tube set in order of draw.
5. Position patient; wash hands; glove; assemble equipment.
6. Apply tourniquet briefly, palpate, cleanse, dry, recheck landmarks.
7. Perform venipuncture; release tourniquet; invert tubes; label at bedside.
8. Ensure hemostasis; thank patient; transport per test requirements.

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Key Takeaways

• Assessment prevents bad specimens and patient injury—treat it as a required step, not optional small talk.
• 21 g is the adult standard; 23 g butterflies help difficult veins; volume and test type drive exceptions.
• Position safely, support the arm, and keep tourniquet time ≤1 minute.
• When in doubt about restricted sites, prep failures, or failed attempts—escalate or defer, then document.