CHBT Vascular Access and Cannulation Basics 2 — Questions and Answers
Question 1: The 'buttonhole' or constant-site technique of cannulation involves:
- Inserting needles into the same sites at the same angle each session to create a fibrous tunnel (Correct answer)
- Using a larger-gauge needle (14G) to create a permanent channel in the graft
- Rotating sites to avoid aneurysm formation in AVF patients
- Using blunt needles only after a scab has formed at the insertion site
Correct answer: Inserting needles into the same sites at the same angle each session to create a fibrous tunnel
The buttonhole technique creates a fibrous tunnel by repeatedly inserting needles at identical sites and angles. Blunt needles are used after the tunnel is established. This reduces pain and aneurysm formation in AVF patients.
The buttonhole technique creates a fibrous tunnel by repeatedly inserting needles at identical sites and angles. Blunt needles are used after the tunnel is established. This reduces pain and aneurysm formation in AVF patients.
Question 2: What gauge needle is most commonly used for cannulation of an arteriovenous graft or fistula in hemodialysis?
- 15–16 gauge (Correct answer)
- 18–20 gauge
- 21–23 gauge
- 12–13 gauge
Correct answer: 15–16 gauge
15-gauge needles are standard for hemodialysis cannulation, allowing blood flow rates of 300–500 mL/min. 16-gauge may be used for lower prescribed flows. Smaller gauges restrict flow and reduce dialysis adequacy.
15-gauge needles are standard for hemodialysis cannulation, allowing blood flow rates of 300–500 mL/min. 16-gauge may be used for lower prescribed flows. Smaller gauges restrict flow and reduce dialysis adequacy.
Question 3: Which sign indicates possible stenosis in an arteriovenous fistula?
- High venous pressure during dialysis combined with a decreased thrill distal to the stenosis (Correct answer)
- Bright red arterial blood returning via the venous needle
- A palpable pulse throughout the entire fistula length
- Normal bruit quality with consistently achieved blood flow rates
Correct answer: High venous pressure during dialysis combined with a decreased thrill distal to the stenosis
Stenosis restricts flow, causing elevated venous pressure as blood backs up behind the obstruction. The thrill (vibration) is diminished distal to the narrowing. This warrants referral for imaging (fistulogram) and possible angioplasty.
Stenosis restricts flow, causing elevated venous pressure as blood backs up behind the obstruction. The thrill (vibration) is diminished distal to the narrowing. This warrants referral for imaging (fistulogram) and possible angioplasty.
Question 4: After completing a hemodialysis session, how long should manual pressure be held at a cannulation site before applying a bandage?
- Until hemostasis is achieved, typically 5–10 minutes (longer if on anticoagulation) (Correct answer)
- Exactly 2 minutes for all patients uniformly
- Until the patient reports the pain has subsided
- 30 seconds; then a pressure dressing can substitute for manual pressure
Correct answer: Until hemostasis is achieved, typically 5–10 minutes (longer if on anticoagulation)
Hemostasis must be achieved before releasing pressure; this typically takes 5–10 minutes. Patients on anticoagulants or with platelet disorders may require longer. Premature release risks significant hematoma formation.
Hemostasis must be achieved before releasing pressure; this typically takes 5–10 minutes. Patients on anticoagulants or with platelet disorders may require longer. Premature release risks significant hematoma formation.
Question 5: A patient with a tunneled hemodialysis catheter develops fever and chills shortly after starting treatment. What should the technician do?
- Stop treatment, notify the nurse immediately, and prepare for blood culture collection per protocol (Correct answer)
- Slow the blood flow rate and monitor temperature for improvement
- Administer acetaminophen to reduce fever and continue treatment
- Increase the dialysate temperature to match the patient's elevated body temperature
Correct answer: Stop treatment, notify the nurse immediately, and prepare for blood culture collection per protocol
Fever and chills during catheter-based dialysis are classic signs of catheter-related bloodstream infection (CRBSI). Treatment should be stopped immediately, the nurse notified, and blood cultures drawn from the catheter and peripherally per protocol.
Fever and chills during catheter-based dialysis are classic signs of catheter-related bloodstream infection (CRBSI). Treatment should be stopped immediately, the nurse notified, and blood cultures drawn from the catheter and peripherally per protocol.
Question 6: What is the correct needle orientation (bevel) for cannulating an arteriovenous fistula?
- Bevel up (opening facing up) at a 25–35 degree angle to the skin (Correct answer)
- Bevel down to prevent damage to the vessel back wall
- Bevel sideways to allow for maximum blood flow
- Perpendicular to the skin surface regardless of bevel direction
Correct answer: Bevel up (opening facing up) at a 25–35 degree angle to the skin
Standard cannulation technique inserts the needle bevel-up at a 25–35 degree angle. This orientation reduces trauma to the vessel wall and allows confirmation of correct placement by blood return through the needle.
Standard cannulation technique inserts the needle bevel-up at a 25–35 degree angle. This orientation reduces trauma to the vessel wall and allows confirmation of correct placement by blood return through the needle.
CHBT Vascular Access and Cannulation Basics 2
The 'buttonhole' or constant-site technique of cannulation involves: