OHSU Mesh Infection -BTK
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[00:00:00] Welcome to another episode of Behind the Knife. We are the OHSU hernia team. I'm Maggie Bosley, one of the hernia and abdominal wall reconstruction faculty here joined by my senior partner, Dr. Sean Ornstein, our abdominal wall recon fellow, Dr. Amber Sandoval, and our chief resident on service, Dr. Peter Farrin.

Today we're gonna be talking about mesh infections and why they matter and how to treat them. The dreaded complication all hernia surgeons think about as we all know. About a half a million ventral hernia repairs are performed a year and even more primary laparotomies that result in about a 20% hernia rate.

And so we know that repairing these hernias with mesh will decrease our chance of recurrence. But when it comes to placing these foreign bodies in our patients, we have to understand what are the consequences of that? What are the potential complications? And then when those arise, what do we do about that?

Historically, people have thought about [00:01:00] using antibiotics, potentially talk about mesh explan. But there's a lot more nuance than just planting mesh. And so let's dive into some considerations. First, let's start with talking about some risk factors from mesh infection. Yeah, so I think when, when talking about risk factors, we can kind of break it down into two major categories.

Patient risk factors and operative risk factors. So under the patient risk factors category are things like immunosuppression non-optimized patients, so obese patients, especially with the BMI over 35 patients who are actively smoking patients with uncontrolled diabetes and patients with a history of post-op surgical site infection.

And then the operative risk factors include things such as urgent repair, prolonged operative times. Contamination during the case and wound class, and then large dead spaces. And one specific thing to mention, sort of as a subcategory under that [00:02:00] is dead space, especially with a piece of mesh in an onlay position where the mesh is, is not a budding muscle, but rather just fat, which has less ability to clear bacteria and absorb fluid.

And then in terms of you know, these risk factors also just talking about emphasizing that there's a time to do a definitive hernia repair versus a time to do a temporizing hernia repair. And in patients who aren't optimized and in, in, in urgent settings potentially doing a temporizing repair to, to minimize these risk.

Yeah. Peter, I think you bring up a lot of good points about things to optimize for our patients and thinking about different tissue planes to put our mesh and what's at higher risk. But we're gonna kind of dive into that in a, in a minute. I think first, let's start off talking about when a patient gets a mesh infection.

What are some of the initial management strategies we should consider? Amber, do you wanna kind of take that one? Absolutely. The first principle that we think about is always source [00:03:00] control. The initial question to ask is, where's the infection and can we drain it? If there's a fluid collection, you can often start with percutaneous drainage to get control of abscesses or deep space infections.

Sometimes that's all that is needed to stabilize a patient and better characterize the problem in light of source control. Another decision point is whether salvage is feasible or whether you're headed toward explanation. That really depends on the type and the position of the mesh, the extent of the infection and the presence of fistula or gross contamination.

In some cases, like in patients with extra peritoneal macroporous mesh, a good debridement and negative pressure wound therapy may be able to buy time and lead to salvage. But in others, such as in clear mesh enteric fistula, drainage alone is inadequate and ex explantation may be necessary. One source control has been addressed.

The next step is to obtain cultures and tailor antibiotics. Deep wound or drain cultures are much more informative than superficial swabs [00:04:00] and empiric. Broad spectrum coverage is reasonable at first, but it's important to narrow when culture results come back. When it comes to antibiotics, there really is no agreed pond duration.

It's individualized based on the extent of the infection and whether meshes retained or removed. If attempting, salvage expect a prolonged course, sometimes weeks of therapy while monitoring for clinical improvement. Finally, the organisms involved matter a lot if enteric bacteria is isolated. This raises suspicion for mesenteric fistula, which likely won't respond to antibiotics alone and warrant surgical intervention.

If MRSA grows that's also a red flag and concerning for biofilm formation, which also may lead to explanation rather than antibiotic coverage alone. In short, get source control early drain when you can debride what is needed and culture aggressively, and then use those results to guide your antibiotic management.

But always be thinking about the bigger picture, which is which type of mesh you're dealing [00:05:00] with, what organism you're facing, and whether this is truly salvageable. Yeah. So when thinking about salvaging mesh versus needing to explan it Amber, you highlighted some good points. There's lots of things to consider and.

Maybe you're somebody who has one go-to mesh and you're not thinking about all these different factors that go into things. But I think if you really understand the prosthetic that you are putting in people or that you inherit from somebody else, you can really tailor your management. And so I think first, before we discuss X plant, let's talk about some, factors that affect salvage rates. And so the first thing I think we should highlight is a study that we'll make sure is in the show notes. This was published in 2020 in the American Journal of Surgery by Jeremy Warren and the Greenville Group that was assessing the factors that affect mesh salvage.

They pooled their cases and there was 213 mesh infections, and they analyzed these and found that the average time to [00:06:00] presentation after an initial hernia repair. To infection was 20 months and it was four years when there was fistula present. So just because you see that patient at your 30 day follow up and they're infection free doesn't mean that an infection isn't gonna come down the line.

And so these can present years out. And so it's really important for us to know how to manage 'em. And that stat is very consistent with some other literature around presentation of mesh infection timeline. Most of the cases that they dealt with involved intraperitoneal mesh and they found that if they were dealing with a macroporous polypropylene, they salvaged the mesh.

And 65% of the cases when, and 72% of the cases were salvaged when the mesh was in an extra peritoneal position. Mesh salvage was not possible in any case that had PTFE. And I know Dr. Orenstein and I talk about that often. If we see PTFE light up on a CT scan, we just know that that mesh is not going to be [00:07:00] something that can be salvaged.

And that's exactly what this study showed. They also found that rarely for a heavyweight microporous polypropylene mesh was that able to be salvaged or a multifilament polyester mesh. Also intraperitoneal mesh not salvageable very often. And so these findings make a lot of sense based on what we know about mesh science.

Thinking about monofilament mesh versus something like a multifilament polyester and the location mesh master ornstein. Can you tell us a little bit more about these mesh properties and why these findings make a lot of sense to us? Yeah, so you already hit home on a lot of the key aspects about mesh salvage, whether it be the mesh type and the mesh location.

As far as starting with the mesh type, multifilament versus monofilament is a critical factor. The problem with multifilament structures, whether it be multifilament mesh, just like multi filament suture. [00:08:00] The, these are typically smaller caliber sutures that are tightly wound or smaller caliber fibers In a mesh construct, they create these small little interstices where bacteria can be harbored.

And because of these tight little spaces, the body has a harder time getting good vascular supply to that and therefore has a hard time clearing that bacterial contamination via its, white blood cell response and inflammatory response. So basically these bacteria sit there and they harbor there and they can form biofilms and that leads to lack of clearance of that.

Now you may not be aware clinically that these bacteria are there. 'cause as you mentioned earlier, sometimes we don't see these infections until months or many years. And then so that's where multifilament structures, and again, seeing things like multifilament sutures, like hyon sutures, which are multifilament braided polyester or multifilament polyester meshes have a very harder time clearing these and frequently have to be [00:09:00] excised.

Take that now compared to a monofilament structure, like a lot of the monofilament. Polypropylene meshes and also newer monofilament polyester meshes. These have a knit or weave that has fewer of those small, little inter interstices is basically smaller less of those smaller nooks and crannies to hide those bacteria.

So that's another way they can be cleared out. Another key aspect of mesh is porosity, micro versus macro porous structures. Things that are. Microporous, like multifilament have tighter weave or knit of the mesh construct and also those smaller spaces for bacterial harbor. Conversely, with a macro porous structure, larger pores the mesh is, is a little bit wider space as far as the mesh fibers goes.

So not only is there less. Little nooks and crannies for the bacteria to hide out on. It also allows better neovascularization, so better blood supply, better and easier clearance of [00:10:00] any potential contamination. As you mentioned also with E-P-T-F-E meshes, these are solid laminar sheets and there are no pores whatsoever.

So, the only thing that the body can really do in these situations is encapsulate and surround that mesh. So if bacteria get in or around. The various parts of the surface of that, the body has an extremely hard time to clear that. So meshes like multifilament polyester or other multifilament meshes and solid laminar sheets like EPTV are close to impossible to salvage looking at both clinical data as well as benchtop data of studies that have looked at salva trays.

The other important aspect besides the mesh construct is mesh location. Tissue planes that we favor, such as retro muscular repairs, retrorectus repairs, and transverses ados release procedures. These to, to me, are like the golden plains of abdominal wall because not only do we create large spaces for large meshes [00:11:00] for giant prosthetic reinforcement of the visceral sac this also is against well vascularized muscle that that added vascularity helps to promote healing and integration of that mesh as well as to.

Fend off any potential contamination infection. Take that and compare that to say the onlay plane, which again you alluded to, where that's closer to the skin and has a more potential for contamination. That is, if there's any wound breakdown and you have bacterial contamination from the skin level that now is closer to, to the mesh and can contaminate that in a slightly different manner with the intraperitoneal mesh, one of the limitations of intraperitoneal underlay mesh.

Is the reduced ability for ingrowth. You only can get some ingrowth from the peritoneum, or if you clear that off from the fascia, you don't have tissue on both sides of that mesh. So not only do you have a reduced ability for ingrowth into the mesh, you also have decreased perfusion into that to then clear any potential contamination [00:12:00] and infection.

Thanks for that overview, Dr. Ornstein, our in-house mesh master. Even with a, a deep understanding of mesh science and when you can salvage and when you can't with conservative management let's consider what we should do if we lose the fight and we have to proceed with a mesh explan. Dr. Farrin, can you tell us a little bit more about this?

Yeah, so when you're faced with potentially Explaning mesh the question exists whether you need to explan all of the mesh, or you can just get away with excising only part of it. And this was a, this was a question that Kao Etal and the Carolinas Group sought to address and their publication 2020 publication in the Annals of Surgery.

We'll also link that study in the show notes. They sought to evaluate outcomes of patients undergoing mesh mesh explanation following partial mesh mesh excision and complete mesh excision. So, they queried the A-H-S-Q-C [00:13:00] registry for ventral hernia patients who underwent excision of mesh at the same time as ventral hernia repair.

They included a total of 1,904 patients. In their study, these patients underwent excision, a previously placed mesh at the time of ventral hernia repair, and after propensity matching complications were significantly higher after partial mesh excision, including surgical site infection, surgical site occurrence, surgical site occurrence, requiring procedural intervention and re-operation.

No differences were observed in patients with clean wounds. But in clean, contaminated wounds, partial mesh excision more frequent, frequently resulted in surgical site occurrence requiring procedural intervention. And in the case of mesh infection and fistulas, higher rates of surgical site occurrence requiring procedural intervention and reoperation we're seen after partial mesh excision.

Overall, the odds ratio analysis showed increased [00:14:00] likelihood of surgical site occurrence requiring procedural intervention. And re-operation with partial mesh excision. So overall, if you're needing to excise mesh, you should try to get it all out. This includes all form bodies too, such as suture material, especially sort of as we just discussed, multi filament polyester sutures that can harbor bacteria and braided sutures that can't be.

And just to further emphasize that we get a lot of referrals to us for mesh infection and mesh explan and many of the operative reports we review. I talk about, the surgeon mentioned how they excise mesh, and in many of these instances, there's still residual mesh product within the abdominal wall.

So it, it really is critical to get out every piece of mesh that you can. Now that said, there might be stray mesh fibers that are fully embedded in the abdominal wall that probably can be left there. But as a general rule, if the goal is to remove mesh for infection, partial mesh, debridement, and partial excision is usually.

[00:15:00] Inadequate to clear the infection, and even if you clear the infection in the short term, there's a good chance that they will be back with a, a long-term chronic infection unless you remove virtually all, or if not the vast majority of it. So now that we have thought about a mesh properties, salvage rates, things that are associated with salvage ex planting, mesh, getting all the mesh out.

Dr. Sandoval, after you graduate from our hernia and abdominal wall fellowship, what's gonna be your treatment algorithm for mesh infections? Yeah. Thank you, Dr. Bosley. When I think about managing a mesh infection, I'd like to approach it in a stepwise and algorithmic fashion. First, if I suspect a mesh infection, the initial steps will be diagnostic and focused on source control.

That means obtaining a CT scan to define the extent of the infection, sending cultures to identify the organism, and proceeding with drainage of any associated collections, whether that's percutaneous or operative. Next, once my diagnosis is established, I can [00:16:00] likely begin to stratify the situation, thinking about the key factors as far as the type of mesh, the anatomic plane it's in, and whether there's a fistula or ongoing contamination.

These features will largely determine whether a salvage attempt is reasonable for me. Okay. In general, I'll consider salvage when the mesh is extra peritoneal, macroporous polypropylene, and there's no fistula or MRSA infection. These are scenarios where local control, antibiotics and perhaps limited debridement may be more successful.

On the other hand, explanation will be in the back of my mind when there is a mesenteric fistula barrier or E-P-T-F-E material, an intraperitoneal underlay mesh, or chronic sinus tract or failure of a prior salvage attempt. And when I do proceed with removal, i'll attempt complete excision, which is generally preferred over partial removal and contaminated and infected fields.

Finally, once the infection is cleared, I can then turn my attention to reconstruction, [00:17:00] which likely will be done in a staged fashion. In these cases, depending on the cleanliness of the field, the ultimate goal down the line will always be to restore the abdominal wall with an extra peritoneal macroporous, polypropylene repair in a clean environment, optimizing long-term durability and minimizing recurrence.

So overall, the treatment algorithm moves from diagnosis and source control to stratification of the problem. Decision between salvage or explanation and finally reconstruction planning in the future? Yeah, I think you bring up a good point. You know, there's certainly data that you can interpret either way about whether or not you're going to do abdominal wall reconstruction in one stage or two stage procedure when it's associated with mesh fistula or contamination.

I think both Dr. Orenstein and I are, are more conservative in that nature and. I wanna take care of the problem at hand and really enter the operation, thinking about what is our goal today? And often my [00:18:00] goal is to eliminate infection and eliminate this acute problem and then come back to fight another day for their definitive recon.

So maybe we can dive into that literature at another podcast, but it, it's something to consider. Dr. Ornstein as our in-house mesh master on this podcast about mesh. Do you have any final pearls for us regarding mesh infections to kind of wrap this up? Yeah. Well, actually one of the best ways to prevent that is has nothing to actually do with the mesh itself, and that's about prevention.

As with any complications, the best way to prevent those is with prevention and for our patient population. Preoperative optimization, I wouldn't even say is important, I would say is crucial. For really optimizing outcomes for these patients, specifically weight loss management, diabetes control. And smoking cessation prior to an elective hernia repair, especially if there's a need for an abdominal wall reconstruction procedure.

Now that said, sometimes there are patients that become highly symptomatic. Perhaps [00:19:00] they become obstructed and the, their body sort of forces our hand to operate sooner than they are before they're fully optimized. And as you mentioned, a as, as, as everybody's mentioned, staged approaches there's nothing wrong with, and I think there's a good and safe.

A treatment algorithm to temporize a hernia, get them through their acute issue or mesh infection or fistula temporize the hernia with either primary suture repair or a bridge repair with a bioresorbable or biologic mesh, and then come back to fight another day that is saving those golden tissue planes for, and it's a more prime location and the patient is fully optimized and out of the major risk from an infectious standpoint.

And then of course there is the choosing the right mesh and the right tissue plane as already discussed at the index operation. But really want to get that patient to the best state of health that we can, and then maximize their outcomes by waiting till they're primed and ready to go for that.

Yeah, I think you summarized things perfectly for us. It's the, [00:20:00] the right patient at the right time and the right operation for them. So thank you everyone for listening to OHSU Hernia Squad and. Dominate, dominate the day.