CCHT - Certified Clinical Hemodialysis Technician Vascular Access and Cannulation 1 — Questions and Answers
Question 1: What is the recommended angle of needle insertion when cannulating a mature arteriovenous fistula?
- 5–10 degrees
- 25–35 degrees (Correct answer)
- 45–60 degrees
- 90 degrees perpendicular to the skin
Correct answer: 25–35 degrees
A 25–35 degree insertion angle allows the needle to enter the vessel lumen cleanly without going through the back wall. Shallower angles risk staying subcutaneous, while steeper angles increase the risk of posterior wall puncture and infiltration.
Question 2: Which of the following is the earliest and most reliable sign of needle infiltration during a hemodialysis treatment?
- A sudden drop in the venous pressure alarm
- Localized swelling and pain at the needle insertion site (Correct answer)
- Blood appearing in the arterial drip chamber
- An increase in the arterial pressure alarm above baseline
Correct answer: Localized swelling and pain at the needle insertion site
Infiltration occurs when the needle tip exits the vessel lumen into surrounding tissue. The immediate result is extravasation of blood or dialysate, causing localized swelling, firmness, and pain at the site. Pressure alarms may change secondarily but are not as specific or early an indicator.
Question 3: What is the minimum recommended distance between the arterial and venous needles during AV fistula cannulation to minimize recirculation?
- 1 cm
- 2 cm
- 5 cm (Correct answer)
- 10 cm
Correct answer: 5 cm
Placing needles at least 5 cm (approximately 2 inches) apart prevents recirculation, which occurs when already-dialyzed blood is immediately re-drawn into the arterial needle. Recirculation reduces treatment adequacy and Kt/V.
Question 4: According to the 'Rule of 6s,' which set of criteria indicates that an AV fistula is mature and ready for cannulation?
- Flow >400 mL/min, diameter ≥4 mm, depth ≤8 mm, maturation ≥4 weeks
- Flow >600 mL/min, diameter ≥6 mm, depth ≤6 mm, maturation ≥6 weeks (Correct answer)
- Flow >500 mL/min, diameter ≥5 mm, depth ≤5 mm, maturation ≥5 weeks
- Flow >800 mL/min, diameter ≥8 mm, depth ≤4 mm, maturation ≥8 weeks
Correct answer: Flow >600 mL/min, diameter ≥6 mm, depth ≤6 mm, maturation ≥6 weeks
The Rule of 6s states a fistula is mature when it has blood flow exceeding 600 mL/min, a vessel diameter of at least 6 mm, is no more than 6 mm below the skin surface, and has had at least 6 weeks to mature. These thresholds help ensure reliable cannulation and adequate dialysis delivery.
Question 5: Which type of hemodialysis vascular access carries the highest risk of bloodstream infection?
- Native arteriovenous fistula
- Synthetic arteriovenous graft
- Tunneled cuffed central venous catheter (Correct answer)
- Subcutaneous port-catheter device
Correct answer: Tunneled cuffed central venous catheter
Tunneled cuffed central venous catheters (CVCs) have the highest infection risk among hemodialysis accesses because the catheter provides a direct conduit from the skin surface into the central venous system, bypassing natural skin and vascular barriers. Native AV fistulas have the lowest infection rates and are the preferred access.
Question 6: In a non-urgent clinical situation, how long should a technician typically wait before cannulating a newly placed synthetic AV graft?
- 24–48 hours
- 3–5 days
- 2–4 weeks (Correct answer)
- 3–6 months
Correct answer: 2–4 weeks
Standard synthetic AV grafts require approximately 2–4 weeks of healing time to allow the graft material to incorporate into surrounding tissue and edema to resolve, reducing the risk of infiltration and hematoma on first cannulation. Early cannulation grafts are a separate product designed for use within 24–72 hours.
CCHT - Certified Clinical Hemodialysis Technician Vascular Access and Cannulation 1
What is the recommended angle of needle insertion when cannulating a mature arteriovenous fistula?