6.1 Requisitions, Patient Prep & Site Selection
Key Takeaways
- Always verify the requisition against two patient identifiers and stop if any name, DOB, test, or special-instruction mismatch appears.
- Confirm patient requirements before drawing: fasting (typically 8–12 hours), timed draws, resting posture, medication timing, and consent/refusal.
- Match equipment to the patient and tests—gauge, device (ETS, butterfly, syringe), and tube types—before applying the tourniquet.
- Tourniquets stay on ≤1 minute; vigorous fist pumping raises potassium; brief warming can help poor peripheral flow.
- Preferred antecubital site is median cubital, then cephalic, then basilic last; avoid mastectomy/fistula arms, hematomas, edematous sites, and above-IV draws.
Why Pre-Draw Steps Dominate Specimen Errors
On the AMCA CMAC blueprint, Collecting Specimens and Diagnostic Testing is 25% of scored items (~40 of 160). Tasks 3.03.1–3.03.6 sit at the front of that block: verify requisitions, confirm patient requirements, select equipment, instruct the patient, prepare the patient (tourniquet, hand squeeze, heat), and prepare the site aseptically. Most laboratory “bad results” are pre-analytical—wrong patient, wrong prep, wrong site, or contaminated site—not analyzer failure. Master this section as a fixed checklist, not as optional courtesy steps.
3.03.1 Verify the Details of Requisitions
A requisition (paper or electronic order) is the legal/clinical authorization to collect specific specimens. Before you touch the patient, reconcile the order with the chart and the person in front of you.
| Requisition element | What you verify |
|---|---|
| Patient identity | Full legal name and date of birth match the patient’s stated ID and armband (if used) |
| Ordering provider | Name/credentials present; order is current |
| Tests ordered | Exact panels/tests; no ambiguous abbreviations you cannot resolve |
| Priority | Routine, STAT, timed, fasting, or “draw with next AM labs” |
| Special instructions | Ice, protect from light, chain of custody, peak/trough times |
| Diagnosis/ICD context | As required by facility for coding—not a substitute for clinical orders |
| Date/time stamps | Order date; any “collect after” or “do not draw before” notes |
Stop rules: any identifier mismatch, missing test, expired order per policy, or patient who cannot be identified → do not draw. Room number or bed number is never an identifier. Do not ask leading yes/no questions (“Are you Mrs. Lopez?”). Ask the patient to state full name and date of birth, then match the requisition and armband.
Electronic orders can still be wrong (duplicate patients, wrong encounter). Visual verification remains your job even when the barcode “beeps.”
3.03.2 Establish Whether the Patient Meets Test Requirements
Many tests are valid only if preconditions are met. Task 3.03.2 expects you to screen before collecting, not after the lab rejects the sample.
| Requirement | Typical expectation | What to do if not met |
|---|---|---|
| Fasting | Usually 8–12 hours, water often allowed; no food, caloric drinks, gum, or smoking per protocol | Reschedule or document non-fasting per provider order; do not silently collect “anyway” |
| Basal / morning | Rested, often fasting, morning cortisol/iron timing | Note time and status; follow timed-draw protocol |
| Medication hold | Some drugs held before levels or special panels | Confirm with provider/nurse—never independently stop meds |
| Peak / trough | Trough just before next dose; peak at drug-specific interval after dose | Coordinate with medication administration record |
| Rest / posture | Sitting 5+ minutes can matter for some analytes | Seat the patient; avoid drawing immediately after running in |
| Consent / ability | Alert enough to consent or surrogate identified | Do not force a refused draw; notify provider |
Ask focused questions: “When did you last eat or drink anything other than water?” “Which medications did you take this morning?” “Have you had a mastectomy or dialysis fistula?” Document answers that affect interpretation or site choice.
3.03.3 Select Appropriate Equipment for Test and Patient Type
Equipment choice is part of the CMAC skill set. Wrong gauge or device increases hemolysis, failed sticks, and injury risk.
| Device / supply | Typical use |
|---|---|
| ETS (evacuated tube system) with straight needle | Routine adult antecubital draws; standard 21-gauge |
| 22-gauge | Smaller or more fragile veins |
| 23-gauge butterfly (winged) | Hand veins, pediatrics, difficult access; may need discard tube before light blue |
| Syringe + transfer device | Collapsing veins; controlled vacuum; never force blood into tubes without a transfer device |
| Needle gauges (concept) | Higher gauge number = smaller bore |
| Tourniquet | Latex-free if allergy; single-use preferred |
| Antiseptic | 70% isopropyl alcohol routine; chlorhexidine (or facility culture prep) for blood cultures; non-alcohol prep when alcohol would invalidate the test (e.g., legal ethanol) |
| Tubes | Correct color/additive for ordered tests; check expiration and vacuum integrity |
| PPE | Gloves minimum; add face protection if splash risk |
Match tube inventory to the requisition before you stick so you do not leave the needle in place while hunting for a lavender top. For pediatric or elderly patients, prefer smaller volumes and devices that reduce vacuum trauma when policy allows.
3.03.4 Provide Instructions for Specimen Collection and Procedures
Patients need clear, brief teaching—even for a simple blood draw.
Venipuncture teaching points:
- Purpose in plain language (“blood tests your provider ordered for your cholesterol and blood count”).
- What they will feel (brief needle stick, pressure).
- How long it takes and that they may sit after.
- Aftercare: keep bandage on, avoid heavy lifting with that arm for a few hours if instructed, report prolonged bleeding or swelling.
- Rights: they may refuse; ask questions; report pain, numbness, or dizziness immediately.
Example of non-blood instruction (clean catch urine)—still within 3.03.4’s “e.g., clean catch” spirit for the broader specimen domain: cleanse as directed, begin voiding, catch midstream, avoid touching inside of cup. Full urine methods expand in Chapter 7; here, know that instruction quality is a blueprint task, not optional customer service.
Use teach-back: “Tell me when you last ate” or “Show me which arm we should avoid.” Language barriers require an interpreter per facility policy—not a minor child as sole translator for complex consent when alternatives exist.
3.03.5 Prepare Patients: Tourniquet, Hand Squeeze, and Heat
These three maneuvers improve vein visibility but alter analytes if misused.
Tourniquet
| Rule | Detail |
|---|---|
| Placement | About 3–4 inches (7–10 cm) above the intended puncture |
| Time limit | ≤1 minute; release and wait ~2 minutes before reapplying if needed |
| Purpose | Temporarily slows venous return so veins engorge |
| Overuse risk | Hemoconcentration (falsely ↑ proteins, potassium, calcium, enzymes, formed elements) |
| Release timing | Once blood flow is established (often as first tube fills), release per facility protocol |
Never leave a tourniquet on while you walk away for supplies. If veins do not appear, release, rehydrate/warm/reposition strategy, then retry—do not “crank tighter for five minutes.”
Hand squeeze / fist pumping
A gentle fist once can help define veins. Vigorous, repeated fist pumping is a classic exam trap: it can falsely elevate potassium (and affect other muscle-related analytes). Instruct: “Make a fist and hold” rather than “pump hard.”
Heat
Warm packs or warm towels (about 42°C / ~107°F, typically 3–5 minutes, never burning hot) increase local blood flow for difficult veins or capillary collections. Do not use microwave-overheated packs that risk burns. Heat is an assist, not a license to ignore site restrictions.
Additional prep
- Seat or recline patients with a history of syncope.
- Support the arm on a firm surface, palm up, slight elbow extension.
- Ask about latex allergy, bleeding disorders, anticoagulants, and preferred arm.
- Confirm nothing to eat/drink when fasting applies.
3.03.6 Prepare the Site: Aseptic Technique and Vein Selection
Preferred veins (antecubital fossa)
| Priority | Vein | Notes |
|---|---|---|
| 1st | Median cubital | Well anchored, lower nerve/artery risk for most patients |
| 2nd | Cephalic | Lateral (thumb side); useful when median is poor |
| 3rd | Basilic | Medial; last resort—near median nerve and brachial artery |
| Alternate | Dorsal hand | Butterfly, shallow angle; more painful, smaller veins |
Palpate: veins feel bouncy/spongy and non-pulsatile. Arteries pulse. Tendons feel hard and cord-like without bounce.
Sites and situations to avoid
| Avoid or restrict | Why |
|---|---|
| Arm on side of mastectomy / lymph node dissection | Lymphostasis, infection risk; needs provider guidance |
| Arm with AV fistula / graft | Never routine draw—limb-threatening |
| Above an IV | IV fluid contaminates specimen; draw below or other arm, follow policy for pausing IVs |
| Hematoma | Contaminated, painful; draw distal/other site |
| Edema, burns, scars, tattoos over site, infection/rash | Dilution, poor healing, contamination, dye issues |
| Sclerosed / thrombosed veins | No flow, painful |
| Foot/ankle (adults) | Higher clot risk; often requires provider approval |
Aseptic site prep (routine venipuncture)
- Cleanse with 70% isopropyl alcohol in a concentric circle from center outward (or facility-approved method).
- Allow to air dry fully (~30 seconds). Do not blow, fan, or wipe dry with non-sterile gauze.
- Do not re-palpate the cleansed center with a contaminated finger; if you must re-palpate, re-cleanse.
- For blood cultures, use facility culture prep (often chlorhexidine scrub with required dry time)—routine quick alcohol wipe is not enough.
Aseptic prep reduces culture contamination and local infection. It does not replace hand hygiene and glove use (infection-control domain), which still apply every draw.
Putting 3.03.1–3.03.6 Into One Flow
- Review requisition → gather tubes/equipment.
- Identify patient with two identifiers.
- Confirm fasting/timed/special requirements and contraindications.
- Explain procedure; obtain cooperation/consent.
- Position, apply tourniquet ≤1 min, select vein, release if prolonged search.
- Cleanse, dry, perform venipuncture (next sections cover needle technique).
If any step fails, stop and escalate—wrong-patient draws and contaminated cultures are high-harm, high-liability events. For CMAC scenario stems, the correct answer almost always prioritizes ID verification, requirement checks, and site safety over “just get the blood.”
A medical assistant is about to draw labs. The requisition lists “Maria J. Garcia, DOB 03/12/1988,” but the patient states her name as “Maria Garcia Hernandez” and DOB 03/12/1989. What is the correct action?
Why does CMAC-level training emphasize releasing the tourniquet within about one minute?
Which antecubital vein is generally the first choice for routine adult venipuncture?
A patient is ordered for fasting glucose and a lipid panel. She reports coffee with cream two hours ago. What should the medical assistant do first?