Posterior wall puncture: stop at the near wall

Question 1What does tenting of the near wall tell you?

1. aThe needle is through the back wall
2. bThe needle is in the artery
3. cThe vein is thrombosed
4. dThe needle tip has reached the wall and has not yet entered the lumen

Question 2Why is flashback unreliable for confirming the needle is in the lumen?

1. aFlashback only occurs in arteries
2. bFlashback never occurs in veins
3. cBlood can return when the bevel sits partly in the lumen after the needle has passed through the back wall
4. dFlashback is a sign of tenting

Question 3You have gone through the back wall. What do you do?

1. aAdvance the catheter straight away
2. bPush the needle further and withdraw quickly
3. cStop, withdraw slowly under vision until the tip is in the lumen, lower the angle and re-enter
4. dRemove the probe and continue by feel

Question 4Why is extra care needed over the vein in the antecubital fossa?

1. aThe veins there are always thrombosed
2. bAn artery or nerve often lies beneath the vein, and a needle through the back wall can injure it
3. cUltrasound cannot be used there
4. dThe vein is too small to see