Saline Lock Question???

[RenaissancemaN]

Just wondering why sometimes when you flush a saline lock that you're able to aspirate for brisk blood return, but you meet resistance when flushing afterwards????

- Positioning?

- thrombus?

[EmergencyNrse]

It's a fair question to ask.

Couple of factors for consideration:

You assess your vein by palpation, assess its size, diameter, length and position...

Choose the correct catheter appropriate for the vein...

Upon insertion you can guesstimate the position of the tip of the catheter but you cannot know for certain if there is an underlying junction where another vein segment might be joining together with the one you cannulated, whether or not there is a valve present @ the tip of the catheter or if the vein or catheter both have changed direction.

You have and assess patency by aspirating blood but there is resistance huh?

What is the size of the syringe? The larger the diameter the greater the pressure.

Try a 3cc syringe over a 6cc or 12cc.

Small diameter catheters (22g,24g) don't flush as well sometimes even in the presence of good blood return.

Pull back a little bit and see if perhaps the tip of the catheter is resting against the vein wall.

This will help if there is narrowing in the vein from the presence of a valve.

Don't get too caught up with "positional" IV's if it remains patent. Use it but perhaps be careful with IV push medications and/or fluid boluses. If There is a concern about a patient going bad consider establishing an additional IV site that isn't as problematic.

Oh, and be sure to report off to the next nurse if you transfer care so they know to be gentle too or it will be blown when you get back.

[IndySkies]

I like your response to the question and the trouble shooting suggestions you mention.

However, not to get to pedantic about it, I think you mean the smaller the diameter the greater the pressure, that is why a 3cc syringe will flush sometimes when a 6cc or 12cc will not.

This is not that intuitive but it has to do with the fact that fluid doesn't like to be compressed and you are using the same pressure, (i.e., your thumb, hand pressure), on the plunger over a smaller diameter, (the opening of a 3cc syring as apposed to a larger one).

[IndySkies]

Whoops..I made a mistake it's the diameter on the plunger, not the exit port of the syringe that makes the difference

[IVRUS, BSN, RN]

When you are aspirating, the smaller syringes will not generate the PSI's that a larger one will.

However, with infusing, the 3 cc syringe exerts more pressure than a 10cc syringe.

[Virgo_RN, BSN, RN]

My first guess would be positional, and I would pull back a little on the cannula to see if that helps.