In this 184th episode I welcome back Drs. Kara Segna and Hassan Rayaz to discuss truncal blocks. We discuss rectus sheath, transversus abdominis plane, quadratus lumborum and erector spinae plane blocks.
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4 thoughts on “Episode 184: Truncal Blocks with Drs. Segna and Rayaz”
Thank you very much for the great episode.
I have 2 questions concerning the TAP Block:
1) How does it compare to a filtration of the wound margin by the surgeon?
2) Some are concerned about SSI caused by the block (eg as part of appendectomy) . Is that justified?
From Dr. Segna:
This is a paper that combined randomized controlled trials (RCTs) comparing TAP block with wound infiltration for pain relief after surgery. The primary outcomes were pain scores at rest and on movement at 1, 8 and 24 hours postoperatively and cumulative morphine consumption over 24 hours. Nine RCTs were compared with 500 participants included. It was found that TAP blocks resulted in lower pain scores at 8 and 24 hours (not 1 hour) compared to infiltration and that MMEs in 24 hours were decreased (although in my opinion not by much at 3.85mg).
Here is another study from 2020: https://link.springer.com/article/10.1007/s12630-020-01818-x
This study looked at 42 studies (2900 patients) and came to the conclusion that there are no major differences.
Although the studies do not majorly support TAP blocks as far-superior to wound infiltration, I have found in my own practice that when I do rescue TAP blocks in the PACU that my patients find significant relief with a minimum of 2 points improvement on the 1-10 Pain scale but upwards of 4 points. When I round on the acute pain service the patients who get TAP blocks seem to have a smoother transition with their pain control, but this is my personal opinion.
As far as surgical site infection, I could not find any papers speaking to this which confirms my suspicion that it may exist but the incidence is incredibly low. I myself have performed thousands of TAP blocks and I have not had a surgical site infection as of yet. I do take care to avoid going through infected appearing tissue and I perform my TAP blocks with an Ultrasound so I have direct visualization of my needle at all times in order to avoid entering the peritoneal cavity. If I were concerned of an intra-abdominal infection I would consider the patient as a whole and decide on a case by case basis if the patient is a block candidate. TAP blocks are part of a multimodal approach to pain management so in certain instances I may rely on other methods.
Could you explain how the fascia transversalis and fascia iliaca relate to each other and the TAP block? Are they connected to each other and how does this impact what nerves are blocked with a TAP block?
From Dr. Rayaz:
I love how thoughtful this question is. The transversalis fascia does indeed contribute aponeurotic fibers to the fascia iliaca below L5. This brings on significant clinical questions. If the transversalis joins with other fascia to transition into the fascia iliaca, can local anesthetic from a tap block spread to the femoral distribution and, on the risk side, cause motor weakness leading to increased fall risk. As far as local anesthetic used for a tap block spreading to the femoral nerve via the fascia iliaca, even with larger volumes, this would seem to be difficult to do. That being said, there are case reports of potential femoral spread, but I don’t know if any comprehensive reviews. Overall, I’d call femoral involvement a rare but possible complication of the tap block. If a patient receives a tap block and is going home, I usually advise the patient to have a supporting person with them prior to getting out of bed, car, etc just to make sure there’s someone with them if they have any weakness. In the inpatient setting, the nurse, tech, and/or PT/OT will likely be with the patient upon getting out of bed. It’s also important to note that the transversalis fascia is just one of the different fascia that join to form the fascia iliaca and the way it’s fibers join with the other fascia would likely impact how any medication spreads. Judging by how seemingly uncommon it is for patients to have lower extremity weakness, it doesn’t look like there’s great spread. One would also have to factor in diffusion of medication as well.
I have included a link to nice anatomy study to illustrate the details of how different fascia interact with the fascia iliaca below.
I really appreciate the question! It shows great attention to detail and an ability to apply this knowledge to the clinical setting. We obviously have some very thoughtful listeners on ACCRAC.