CCMA Phlebotomy Procedures 2 — Questions and Answers
Question 1: A tourniquet should be released within how many minutes of application to prevent hemoconcentration?
- 30 seconds
- 1 minute (Correct answer)
- 2 minutes
- 5 minutes
Correct answer: 1 minute
The tourniquet should be applied no longer than 1 minute to prevent hemoconcentration and hemolysis, which can falsify laboratory results.
Prolonged tourniquet application (>1 minute) causes: hemoconcentration (increased concentration of large molecules like proteins, RBCs, potassium that cannot pass through capillary walls during venous stasis), hemolysis (from increased venous pressure), and falsely elevated results for potassium, proteins, calcium, and cells. CLSI guidelines: apply tourniquet 3–4 inches above the puncture site, release before or immediately upon blood flow initiation, and always release within 1 minute. If a vein is difficult to locate, release, wait 2 minutes, and reapply before puncture.
Question 2: Which gauge needle is most commonly used for routine adult venipuncture?
- 16 gauge
- 18 gauge
- 21–22 gauge (Correct answer)
- 27 gauge
Correct answer: 21–22 gauge
21–22 gauge needles are standard for routine adult venipuncture, providing adequate flow without excessive trauma to the vein or hemolysis.
Needle gauge selection: 16–18 gauge: blood donations, large-volume draws, trauma patients; 20–21 gauge: standard adult venipuncture; 21–23 gauge: butterfly needles for fragile or small veins, elderly patients; 23–25 gauge: pediatric venipuncture, hand veins; 25–27 gauge: intradermal or subcutaneous injections. A 21–22 gauge needle is the routine choice for adult venipuncture — large enough to allow adequate blood flow without creating excessive negative pressure (which causes hemolysis) or coring the stopper repeatedly. Butterfly (winged) sets (21–23 gauge) are used for difficult veins.
Question 3: Which of the following patients should have the antecubital vein avoided for venipuncture?
- A 45-year-old healthy male patient
- A patient with a dialysis fistula in the left arm (Correct answer)
- A patient who has been fasting for 12 hours
- A patient with well-hydrated, easily visible veins
Correct answer: A patient with a dialysis fistula in the left arm
Venipuncture in an arm with a dialysis arteriovenous (AV) fistula is contraindicated, as it risks damaging the fistula and compromising dialysis access, which can be life-threatening.
Contraindications for phlebotomy in specific sites: AV fistula/graft arm (dialysis access) — NEVER puncture (risk of infection, thrombosis, damage to critical vascular access); Mastectomy side — avoid due to risk of infection and lymphedema (especially if lymph nodes were removed); IV/PICC line site (draw from the other arm if possible); Edematous extremities (results unreliable, risk of infection); Hematoma site (results unreliable); Burns, rashes, or severe skin breakdown. Always ask patients about these contraindications before selecting a venipuncture site.
Question 4: The gray-top (fluoride/oxalate) tube is specifically required for which laboratory test?
- Coagulation studies (PT/INR, PTT)
- Whole blood glucose testing (Correct answer)
- Complete blood count (CBC)
- Thyroid function tests (TSH, T4)
Correct answer: Whole blood glucose testing
The gray-top tube contains sodium fluoride (a glycolytic inhibitor) that prevents continued glucose metabolism after collection, preserving accurate blood glucose levels.
Gray-top tube additive: sodium fluoride (glycolysis inhibitor) + potassium oxalate or EDTA (anticoagulant). Fluoride inhibits the enzyme enolase, stopping glycolysis in red blood cells (which would otherwise consume glucose at ~10 mg/dL/hour at room temperature). Without fluoride, glucose values drop rapidly, leading to false hypoglycemia. Gray-top tubes are used for: fasting glucose, glucose tolerance tests (GTT), lactate levels. Not suitable for: most other chemistry tests (fluoride interferes with many assays). Light blue (citrate) = coagulation; Lavender (EDTA) = CBC; Red/gold (SST) = most chemistry tests.
Question 5: When drawing multiple tubes during a single venipuncture, which tube must be drawn BEFORE the SST (gold) tube?
- EDTA (lavender) tube
- Sodium fluoride (gray) tube
- Sodium citrate (light blue) tube (Correct answer)
- Heparin (green) tube
Correct answer: Sodium citrate (light blue) tube
The light blue (sodium citrate) tube must be drawn before the SST because citrate tubes require a precise 9:1 blood-to-anticoagulant ratio, which can be disrupted by carryover from SST clot activator.
CLSI order of draw: (1) Blood culture bottles, (2) Light blue/sodium citrate (coagulation), (3) SST/gold (serum), (4) Red (no additive), (5) Heparin (green), (6) EDTA (lavender/pink), (7) Fluoride (gray). The light blue tube must precede SST because: (a) SST tubes contain silica/clot activators that would contaminate the citrate tube and falsely shorten clotting times; (b) the 9:1 blood-to-citrate ratio must be exact for accurate PT/INR and PTT. If a light blue is the only tube needed, a discard tube (red or blue) is drawn first to remove tissue thromboplastin released at puncture.
Question 6: A patient states they are scared of needles and may faint. What precaution should the medical assistant take?
- Reassure the patient and proceed quickly without additional precautions
- Have the patient sit in a standard chair and perform the draw as quickly as possible
- Have the patient lie down or recline in a phlebotomy chair with safety restraints available (Correct answer)
- Refuse to perform the draw until the patient's fear is completely resolved
Correct answer: Have the patient lie down or recline in a phlebotomy chair with safety restraints available
Patients who are prone to vasovagal syncope (fainting) during blood draws should be positioned supine or in a reclined chair with side arms to prevent injury from falling.
Vasovagal syncope (fainting) is triggered by the sight of needles, blood, or anxiety, causing sudden drop in heart rate and blood pressure. Prevention and management: (1) Have the patient lie down or recline in a phlebotomy chair if possible; (2) Ask the patient to look away during the draw; (3) Keep the patient cool (wet cloth to forehead); (4) Engage the patient in conversation to distract; (5) Have the patient flex the muscles of the legs and abdomen (increases venous return); (6) If syncope occurs: lay flat, elevate legs, call for assistance, monitor vital signs. Document the episode. Never have a vasovagal-prone patient sit in an unsupported chair.
CCMA Phlebotomy Procedures 2
A tourniquet should be released within how many minutes of application to prevent hemoconcentration?