Name:
Cellulitis
Description:
Cellulitis
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Duration:
T00H17M53S
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Upload Date:
2022-09-15T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
DR. SMITH: Welcome back to Run the List, a medical education podcast in partnership with McGraw Hill Medical. Our hosts are Dr. Navin Kumar, Dr. Walker Redd, Dr. Emily Gutowski, Dr. Joyce Zhou and myself, Blake Smith. As a quick disclaimer, this podcast is meant for informational and educational purposes only, and should not be understood as medical advice under any circumstances. [intro music] [intro music] [intro music]
DR. GUTOWSKI: Hi, everyone, welcome back to Run the List. My name is Emily Gutowski and I'm a resident in internal medicine at Mount Sinai Hospital in New York City. I'm here today with Dr. Sal Cilmi, ID attending, he did his fellowship at MGH in Boston and program director now at Mount Sinai Hospital in internal medicine. Today, we're going to be talking about cellulitis, which is a very common diagnosis in IM.
DR. GUTOWSKI: Dr. Cilmi, thank you so much for joining us. [Dr. Cilmi] Thank you for having me.
DR. GUTOWSKI: So without further ado, let's go ahead and get into the case. We have a 62-year-old woman who has a medical history of uncontrolled diabetes, hypertension, obesity, and peripheral arterial disease, presenting to the ED with swelling and a rash over her left leg. She tells you she woke up yesterday, she noticed her leg was swollen and it's been getting worse and more painful for the past 24 hours.
DR. GUTOWSKI: She doesn't remember any major trauma to the area, but she said she did shave her legs a couple of days ago with an old razor. She thinks she's had some fevers and chills at home, but she's never taken her temperature. So from what she's telling you, Dr. Cilmi, you start thinking she may have cellulitis. Just to start, what exactly is cellulitis? [Dr. Cilmi] Cellulitis is one of the soft tissue infections that's very common in internal medicine and we define soft tissue infections by the layers of the skin or the soft tissues that are affected.
DR. GUTOWSKI: So cellulitis actually is a particular infection of the dermis and the subcutaneous fat, that's how it's defined. Other things, like erysipelas are limited mostly to the dermis, things like folliculitis are limited to the hair follicles, et cetera, et cetera. So cellulitis is dermis and subcue fat.
DR. GUTOWSKI: Got it, and what kinds of things do we have to keep in mind in terms of the patient when we're thinking about a possible diagnosis of cellulitis? [Dr. Cilmi] Yeah, very good question. So a lot of this has to do with risk factors for this infection and risk factors can include things from obesity, diabetes, which is an immunocompromising condition, other immunocompromising conditions, also other anatomic compromising conditions like lymphedema, and certainly in this case as well, peripheral arterial disease, which limits blood flow to the tissues, all of those put this patient at risk for a soft tissue infection, which is cellulitis.
DR. GUTOWSKI: Okay, so let's get back to the case. So her vital signs are notable for a temperature of 100.4, her blood pressure is 124/72, and her heart rate is 96. On exam, her left shin has a poorly defined region of erythema. The area is warm to the touch, the skin is firm and the entire lower leg appears to be swollen, compared to the right leg. There's no purulence or crepitus. The rest of her exam is largely unremarkable.
DR. GUTOWSKI: So Dr. Cilmi, how does the physical exam in particular help you determine what's going on and what organisms might be at play? [Dr. Cilmi] Great question. So the case as presented obviously is suggesting an infectious process, like cellulitis here. If I could just go through it, you mentioned that her temperature is 100.4, kind of right on the border that we typically think is an actual fever, so that's important.
DR. GUTOWSKI: Also importantly, there's erythema, right? So we talk about the signs of inflammation, you know, everyone talks about calor meaning heat, and rubor meaning redness, or dolor meaning pain, right? And tumor being swelling- It kind of here has all of those signs of inflammation. And we often put loss of function as the fifth sign of inflammation here, but the fact of the matter is, that all of these suggest an inflammatory process.
DR. GUTOWSKI: The important points that you noted there, Emily was that the heart rate was 96, which is a little bit elevated probably, but not really tachycardiac, but the blood pressure is stable. So therefore we don't have a very hemodynamically unstable patient, which might suggest that if it were a soft tissue infection, it might be a little deeper than just superficial, like cellulitis or erysipelas.
DR. GUTOWSKI: The other things here that we are noting are no purulence or crepitance. Okay? So, purulence often allows us to think about cellulitis in terms of what's producing pus, which might lead you towards staphylococcal infection, especially if we think about what organisms could cause that; when it's non-purulent, we really think in terms of streptococcal infection. Now, there are a lot of microbiology that we could isolate from a cellulitic leg, for example, but the vast majority, even in diabetics are going to be Gram-positive cocci, which are staph and strep.
DR. GUTOWSKI: It's very true that purulent cellulitis is often staph, but it doesn't have to be, staph can also be non-purulent and vice versa, most likely non-purulent is going to be strep, but it could also be purulent as well. So it's just a bit suggestive. One of the things to worry about in terms of trying to distinguish between staph and strep, another little pearl actually is that streptococcal cellulitis is actually really fast on and fast off when you start treating it.
DR. GUTOWSKI: Whereas staphylococcal cellulitis, even non-purulent staphylococcal cellulitis actually kind of can get bigger kind of slowly, and then when you treat it, it really recedes very slowly. In fact, a hallmark of staphylococcal cellulitis is when you treat with the appropriate antibiotic and you draw a line around the cellulitic area, it actually will go beyond that in the first day and then recede.
DR. GUTOWSKI: So oftentimes we have to be aware of that, okay? And not immediately change antibiotics, but that's another pearl that you can have. Uncommonly, you can have Gram-negative cellulitides in certain cases, obviously there are very odd organisms, if the history would suggest it, for example, someone who injured themselves on a boat or in a marine environment or someone who's been clamming in the bay who has a leg cellulitis, those organisms are a little different.
DR. GUTOWSKI: But vast majority, Gram-positive cocci, staph and strep.
DR. GUTOWSKI: Got it. That's very helpful. Thank you for taking us through that. Before we make the diagnosis for this patient, what are some of the other things that we should be considering on our differential? [Dr. Cilmi] Another great question. So vascular disease itself is going to cause sort of alterations in the skin, right? So peripheral arterial disease or peripheral venous disease, venous stasis that can occur in many different circumstances can often be erythematous and red, so that's going to be on your list.
DR. GUTOWSKI: Other things are DVT, so deep venous thrombosis can actually present as a very painful, swollen, red leg, oftentimes unilaterally versus bilaterally, right? DVTs can cause bilateral swelling, but often that's from, you know, IVC clot or something that could actually stop the circulation from both legs. It's also interesting to note that it's rare to have bilateral lower extremity cellulitis, but it does happen in the right context and history is everything, again, that person clamming in the bay who comes in and two days later has bilateral redness, most likely would have bilateral cellulitis from the exposure.
DR. GUTOWSKI: Other things, other dermatitides can present like that, people who are extremely obese can often have a panniculitis of the lower extremities, that alternates being very red to not being red, if you actually elevate the legs, and so that's important to think about. Lymphedema itself actually causes swelling of the legs and often erythema, if it's a little irritated, without cellulitis or without soft tissue infection, but lymphedema is also a predisposing condition to get a soft tissue infection, so sometimes it's a little hard to tease out.
DR. GUTOWSKI: And then the last thing that we want to mention is, again, there is a distinction between superficial soft tissue infections and deep soft tissue infections. And that's very important. And so some of the things you can use to distinguish the two, although it's not a hundred percent, is that if you have someone with a likely cellulitis or a likely superficial infection that presents with hemodynamic instability, always think the infection could be deeper.
DR. GUTOWSKI: Obviously crepitance or the presence of bullae on the skin can often represent something brewing a little bit deeper than staying superficial, often compromised vascular supply, like a little venous insufficiency or an ischemic leg in the setting of redness, which could represent a compartment syndrome that actually would represent a deep tissue infection is also important to think about. And finally, if someone has neurologic changes, like either loss of sensation or incredible pain, out of proportion to what you're actually seeing, all of that might make you think that the infection got a little bit deeper and requires a little more diagnostic intervention.
DR. GUTOWSKI: Got it. That's really helpful. So we're reassured by her exam, we don't think that this is a deeper infection because we've ruled out a lot of the things that you just mentioned. She has a good pulse peripherally, there's no bullae or crepitus, like we said. We did do, let's say we did a Doppler, we were able to rule out a DVT and she tells us that she doesn't have any pre-existing lymphedema and her leg really does look different than it normally does at home.
DR. GUTOWSKI: So we're almost ready to call this cellulitis confidently. How do we really make the diagnosis? [Dr. Cilmi] Well, you know, the diagnosis is really clinical, for the most part. There really are no tests that can sort of confirm that, we can do a skin biopsy, but the fact is that a skin biopsy is rarely indicated, and can cause a little bit of trouble, especially if you're biopsying a place that's acutely infected.
DR. GUTOWSKI: Interestingly enough, in the literature, there are studies looking at early dermatology consultation in cellulitis, meaning that if you really are confused about what it could be, calling a dermatologist early on actually improves the diagnostic ability of the team to recognize cellulitis, and actually the patients get better a little bit faster.
DR. GUTOWSKI: Interesting. [Dr. Cilmi] The same way that if you have an invasive staphylococcal infection, if you call infectious disease consultation earlier, patients actually do better. So it's really sort of understanding what the clinical syndrome is and recognizing it early, before it gets to more complications. We often send, you know, the white blood cell count in a complete blood count with a differential, it's very helpful if there's any kind of left shift, including increased bandemia or immature white blood cell forms, it's actually much more likely to be bacterial infection.
DR. GUTOWSKI: An elevated white cell count is also telling that something's going on. And certainly, if you see purulence along the way, it's also very indicative of sort of a bacterial infection, but it really is a clinical diagnosis, and then you give the right therapy or at least what you think is the right therapy, and then it seems to get better more than anything.
DR. GUTOWSKI: Got it. Okay. So should be something that's pretty clear to us, but if we're on the fence at all, then good to get our ID and possibly dermatology colleagues involved as well. So going back to the case, her labs are notable for an elevation in her white count to 15. Her blood cultures and the differential are both pending. You diagnose her with cellulitis and you decide to admit her for treatment with IV antibiotics.
DR. GUTOWSKI: So let's talk about treatment a little bit. How do we think about what would be the most appropriate antibiotics for this patient and any patient with cellulitis? [Dr. Cilmi] Yeah. So algorithmically, if you think about it, again, the most likely pathogens in any cellulitis are by far Gram-positive cocci, so that means strep and staph. Streptococci are almost uniformly sensitive to beta-lactams, I mean, there certainly are those that are a little resistant, but for the most part, most streptococci, and certainly most of the ones that we think about that cause severe cellulitis like strep group A, streptococcus pyogenes, or strep group B, typical example, strep agalactiae, those are going to be just about sensitive to actually good old fashioned penicillin, but any of the penicillin derivatives, such as first generation cephalosporins, even second and third generation cephalosporins are pretty good getting most streptococci.
DR. GUTOWSKI: In terms of staph, of course, staphylococcus aureus which is really the king, comes in two flavors, right? There's one that we call methicillin-sensitive, although of course we don't use methicillin anymore; and one is methicillin-resistant, right? And so one of those is sensitive to sort of, penicillin derivatives and the other one is not. And so therefore when you see someone who's coming in with a really bad cellulitis, it's important to consider the fact that if it is staphylococcal, you want to cover for MRSA, which in our world is vancomycin added to the regimen. Okay?
DR. GUTOWSKI: If someone comes in with a relatively uncomplicated, non-purulent cellulitis, it's really okay to target strep and even maybe sensitive staph like MSSA. And therefore you could start with something like nafcillin or oxacillin or cefazolin. But if you really have a high likelihood that this patient could have MRSA, you really have to add vancomycin to that regimen to make sure that things are okay.
DR. GUTOWSKI: It turns out of course, that strep and staph are pretty much very, very sensitive for the most part to vancomycin, in fact, vanco is an excellent strep drug. So if you really think it's Gram-positive, vanco alone until you realize that maybe it isn't MRSA is actually a reasonable choice. The other thing that I think would build on that is when do you actually have to cover Gram-negative organisms, because that's less likely. There are certain circumstances when there's Gram-negative coverage necessary, and then a lot of that has to do with the history and what the exposures were, a lot of that has to do with immunocompromise.
DR. GUTOWSKI: So if someone is an immunocompromised host and I mean, significantly immunocompromised, things like neutropenia, patients who have been treated with chemotherapy for cancer, patients who have advanced AIDS, other kinds of immunocompromising conditions, Gram-negatives become a little bit higher on the list. Of note, diabetics who don't have an obvious ulcer, probably most likely have Gram-positive infection, but we often do in very severe diabetics cover for Gram-negatives upfront and very quickly sort of remove things to tailor the antibiotic therapy to be more specific.
DR. GUTOWSKI: But if you have any ulceration in the skin in a diabetic, or an ulcer that might have underlying osteomyelitis, it's another important thing to remember that you need to cover Gram-negatives, and in fact, in those cases, anaerobes, which are unlikely to cause regular old cellulitis, but certainly play a role in the tissue ulcers with osteomyelitis in diabetics, and also in things like genital or perennial infections where you might have some anaerobic flora that play a role.
DR. GUTOWSKI: That was very helpful, thanks, Dr. Cilmi. So this patient initially gets treated with vanc and cefepime for three days. She then gets transitioned to IV cefazolin for two days. Her fever, white count and exam all have very significant improvement. Her blood cultures have no growth and given her overall improvement, she's transitioned to PO antibiotics, the team decides on Keflex for three days and she is sent home with close PCP follow-up.
DR. GUTOWSKI: So we've treated this patient successfully. She's feeling a lot better and is very grateful for her care. Dr. Cilmi, as we start to wrap up this case, do you have any take-home points or pearls? I'll just share one that I didn't know about before, which is that in staphylococcal cellulitis infections, you can expect to see things getting worse before they get better.
DR. GUTOWSKI: [Dr. Cilmi] Right, that's kind of a pearl that I was taught many, many years ago and I still see it happen on the wards. One of the things before the take-home points I wanted to mention that the transition to PO antibiotics is actually often a question we do get. Remember that the use of intravenous antibiotics upfront is mostly due to the pharmacologic considerations of the drug, right? Because by definition, IV antibiotics have 100% serum bioavailability.
DR. GUTOWSKI: And so therefore you're actually getting a lot of bang for your buck, like a lot of people with bad cellulitis, you give them IV for a few days, and then you can easily transition them to PO, but remember that a lot of the beta-lactam antibiotics, like the one in this case that we're transitioning from cefazolin to cefalexin orally, the oral cephalosporins have very poor serum bioavailability, but we use it to sort of mop up the end of therapy, once they've gotten enough drug to sort of kill the bacteria and allow one's immune system to sort of fight that infection. Just to make that point.
DR. GUTOWSKI: But number one of the take-home points, I want to echo what you said, yeah, staph cellulitis gets worse before it gets better. That's one, but remember that overall, when you look at these kinds of patients and these kinds of syndromes, soft tissue infections depend on the level of the skin where they're at, right? We really divide them into superficial and deep, and cellulitis is actually superficial, right?
DR. GUTOWSKI: So you can get away with antibiotics alone as opposed to deep tissue infections, where you have to get the surgeons involved pretty early. Number two, I really want to say again, most cellulitis is Gram-positive cocci, most cellulitis is staph and strep. Even in the diabetic population without an ulcer or something that has, you know, degranulated tissue. Okay? So therefore targeting staph and strep are really important upfront.
DR. GUTOWSKI: And then, I want to echo the fact that if they're really severe and they have to be hospitalized, you want to start with intravenous antibiotics, and as you see improvement, you can then feel comfortable switching to oral antibiotics, some of which have better bioavailability than others.
DR. GUTOWSKI: Dr. Cilmi, this was a super interesting and helpful discussion about a topic that I know our incoming interns and residents at all stages will have a lot of experience with, and be very grateful for your assistance. So thank you so much for joining us and look forward to the next time we talk. [Dr. Cilmi] It is my pleasure. [outro music] [outro music]