Question about thoracic paravertebral catheters

[excalibur]

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OK. I have never done a parvertebral block. I am interested though and have read the recent thread on SDN regarding them. Great stuff in that thread by the way.

I have reviewed the videos on USG placement.

My question is for those of you who place catheters and do the USG lateral to medial approach, doesn't the entry point of the catheter interfere with the surgical incision or at least the surgical prep? I know that when I do thoracic epidurals for our thoracotomies I tape the catheter in a fashion that the tape doesn't even pass midline of the back into the surgical side.

I feel I can have opportunities with our CT surgeons to try paravertebral catheters for thoracotomies, but I want to get this aspect down so no one gets upset that the catheter interferes with the prep or incision.

Actually, I have more questions...

-For catheter placement, do you use a standard epidural kit with a 17 g Tuohy?

-What do you typically set the depth of the US machine for these?

-Is anyone doing them with the straight linear probe? That is the only probe we have at our insititution. I have seen a few videos with just a straight probe, but the vast majority of videos show a curvilinear probe.

 

[Mman]

Don't have words of wisdom as I don't do PVB catheters (stick to single shots) and I don't use U/S. But I will say that you should be very careful. The degree of difficulty is much higher and margin of safety much smaller with a PVB compared to peripheral nerve blocks. It's not a block that tends to lend itself to self teaching.

 

[excalibur]

Don't have words of wisdom as I don't do PVB catheters (stick to single shots) and I don't use U/S. But I will say that you should be very careful. The degree of difficulty is much higher and margin of safety much smaller with a PVB compared to peripheral nerve blocks. It's not a block that tends to lend itself to self teaching.

Understood. I realize that paravertebral blocks in general are advanced blocks. I do all my blocks with ultrasound. The beauty of ultrasound is that you can SEE the anatomy and you can see where the needle is going in relation to the anatomy. I would rarely attempt new blocks on my own from just reading about the technique using anatomical landmarks and then going and trying it out, especially not ones that may have a high incidence of serious complications in novice hands

I know that with my ultrasound view I should shee the shadow of the transverse process, the external intercostal muscle, the internal intercostal muscle along with the important internal intercostal membrane, the somewhat triangular and black thoracic paravertebral space and the hyperechoic parietal pleura. The paravertebral space will be sandwiched in between the transverse process, the internal intercostal membrane, and the parietal pleura. Guide the needle until one pierces the internal intercostal membrane and enters the paravertebral space. Upon injecting the local anesthetic, the parietal pleura will displace downward and laterally on the US screen.

The complication to worry about is PTX which is why I want to practice them on thoracotomies where a CT will be placed anyway.

If I don't see the picture I want to see on US, then I don't do the block and proceed with throacic epidural. If I do see the picture, and I know I need to put the needle tip 'right there" on the screen, then I will do it.

I know you don't use ultrasound, but those who do use it to do blocks where you guide the needle just millimeters from the parietal pleura (supraclavicular block) and from the peritoneum (transversus abdominis plane block). The thoracic paravertebral block under ultrasound in that regard should be similair. I understand that the depth of the block is more and your angle will be steeper. I also understand that the risk of PTX is always there and is increased in novice hands. Again this is why if I were to do it, I would do it on thoracotomies where a CT will be placed.

 

[Oggg]

1. I've only done a handful of TPVB single shots. No catheters yet.
2. I think you have to do a parasaggital (non transverse) approach to keep the catheter out of a thioracotomy field.
3. The best scanning practice for TPVB is a lumbar laminectomy or SI Jt fusion. Second best is yourself
4. C60 is more panoramic than a linear probe. Supposedly you can see local spread to multiple levels with a Curved probe, so the guy in the recent ASRA newsletter (from Pitt) recommends C60. I can't see sht with the C60.
5. I've found parasaggital to be tough because the angle is very steep. We recently got the Sonosite MBe needle visualization software, and that shoul help. The Pitt guys state without evidence that they've had no problem seein their needle tip. The images they put in the ASRA newsletter don't show the needle tip at the TPVS.
6. 18g Tuohy with a 20g epidural catheter or 17g Tuohy with a 19g flextip are both fine.
7. If you can see your tip at all times, I think your Ptx risk is low.

 

[imfrankie]

This month's ASRA bulletin has a nice discussion.

 

[Oggg]

Yeah this months is Pitt advocating parasaggital approach. Last newsletter had a guy writing about transverse approach

 

[deleted9493]

Yeah, the insertion point can get in the way of a full clam shell thoracotomy on a lateral to medial approach. You can give yourself a little space by tunneling the catheter away from the incision but the obvious danger in that is that the track of the catheter is still potentially intersecting with the incision. Have the surgeon mark the extent of the biggest forseeable incision and see if a steeper approach to the PVB space isn't viable.

I still like using ultrasound on parasagittal approach with the probe oriented in the transverse plane scanning up and down to identify the hypoechoic transverse processes. This at least gives me a marker for the appropriate depth of the transverse process in larger patients--once I've identified TP depth, finish with blind technique. I'd think that this approach would be helpful for attendings supervising residents and give peace of mind, otherwise.

Yeah, 17g Tuohy--I like the hyperechoic/etched needles for the lateral to medial approach. Passing the catheter smoothly is usually the most challenging part of this procedure for me; I usually aim for 2-3 cm in the space.

High frequency linear probe for skinny patients. Standard probe for bigger folks.

 

[excalibur]

Thoracotomy for wedge resection today. My partner's case. Plan was thoracic epidural. I asked if I could bring the US to view anatomy only. I do, and I did not like my view. I saw easily identifiable parietal pleura, a black space above most of the pleura which any part of could have been paravertebral space. I saw what I believe were the intercostal muscles, and I could not really make out the transverse process. I just need more practice

 

[Oggg]

Scan your lumbar surgery patients under The drapes. Take all the time in the world.