Episode Transcript
Dr. Linda Nguyen
[00:00:00] Jill Brook: Hello, fellow POTS patients and super people who care about POTS patients. I'm Jill Brook, your Hyperallergic host, and today we are discussing gut motility and gastrointestinal issues in POTS with a most fabulous physician and researcher. Our guest today is Dr. Linda Nguyen, a gastroenterologist and motility specialist at Stanford University. In addition to seeing patients, she has also authored so many peer-reviewed medical articles that I gave up, counting them. She has a special interest in a lot of topics that POTS and Dysautonomia patients care about, such as gastroparesis, chronic nausea, cyclic vomiting, irritable bowel Syndrome, autonomic dysfunction, the overlap with Ehlers-Danlos Syndrome and myalgic encephalomyelitis and brain gut disorders. And she has a reputation for not only being brilliant, but also really getting it that complex chronic disorders can interact with GI issues and greatly affect quality of life.
Dr. Nguyen has also recently published a new article about gut motility in POTS, which we'll discuss today. Dr. Nguyen, thank you so much for joining us today.
[00:01:15] Dr. Linda Nguyen: Jill. Thank you for having me and for all those kind words.
[00:01:20] Jill Brook: Well, okay, so as a GI specialist, I am wondering how many POTS patients do you really see? Like does GI come up often in POTS? And what kind of GI symptoms do you tend to see in the POTS patients?
[00:01:35] Dr. Linda Nguyen: Yeah, so I see a lot of patients with POTS, and I don't know if that's just because it's now my referral practice and people seek me out because they know I take care of patients with POTS.
That being said, up to 80% of patients with POTS will have some type of gastrointestinal manifestation. Nausea is the most common one. It followed by vomiting, abdominal pain, and then, the constipation, diarrhea.
[00:02:07] Jill Brook: Okay. And I guess we'll get to this in a minute, but do you actually have things you can do for people who have those issues? Because we hear about that a lot, right? And, and I guess patients get used to thinking they just have to live with nausea forever...
[00:02:21] Dr. Linda Nguyen: There's definitely things that we can do. There's no magic cure. There's no magic bullet. As you all know and most of what we do is one. Address the predominant symptoms so what's bothering you?
The which of all those constellation symptoms is bothering you the most? Because it's generally not just nausea or it's not just abdominal pain. It's multiple symptoms and so we can try to address them one at a time because you can't address everything all at once. Because if you start too many medications at once, you don't know what's doing what.
So I typically start with the most prominent symptom that's affecting someone's quality of life, but also looking at the physiology in trying to address the physiology. For example, patients with nausea can either have rapid gastric emptying, slow gastric emptying or normal gastric emptying. Exact same symptoms, three different physiologies.
And so if someone has nausea with rapid gastric emptying, I would choose a different treatment, as opposed to someone with nausea and slow gastric emptying.
[00:03:39] Jill Brook: So that is so interesting. And I guess I'm excited to have you educate us a little bit about GI Motility and I guess before we get into all the different ways that POTS patients can have messed up GI motility, can you just give us a primer on GI motility? Like what is it supposed to look like?
[00:03:58] Dr. Linda Nguyen: Well, one, if your GI tract is working normally, Once you are done chewing and swallowing, everything takes care of itself. And you should not be aware of anything other than the urge to have a bowel movement, sit on the toilet, evacuate and be done. So the process of eating and pooping should be automatic and you're not really thinking about it.
So that's normal GI physiology. The entire digestive process is controlled by nerves and hormones, and so there are nerves within the GI tract, so the enteric nervous system or the second brain, but also the autonomic nervous system, which is why you can see how POTS can affect the GI tract because POTS is within that spectrum of autonomic dysfunction or autonomic dysregulation.
[00:04:58] Jill Brook: Can I ask what might be a silly question... is the enteric nervous system outside of the autonomic nervous system?
[00:05:07] Dr. Linda Nguyen: The enteric nervous system is essentially it in of itself. So actually, if you take the colon out of the body and you put it into a bath, you'll see the contractions. It'll contract without any input from the brain or the autonomic nervous system, because that's the enteric nervous system that's functioning.
[00:05:28] Jill Brook: Oh, that kind of blows my mind. Interesting. Okay. So can I ask, so once someone, for example like takes a bite of an apple and chews it up, how long is it supposed to take normally until that gets pooped out and where is it spending most of its time? Like in the stomach or the small intestine or colon?
[00:05:50] Dr. Linda Nguyen: Well, I don't know the exact time of an apple. But most of the studies on gastric emptying has been looked at using a standardized meal of like egg beaters, bread, jam, and water. And so we know how long it takes for that to empty because how long it takes to digest Something really depends on the content of the food.
So the caloric content, as well as whether it's a fat, protein, carbohydrate or a fiber. So an apple with the skin on it actually takes longer to digest than a peeled apple.
[00:06:34] Jill Brook: Okay.
[00:06:35] Dr. Linda Nguyen: it's more complex. So that meal there that I had mentioned earlier, minus the apple, if you had normal digestion at the end of four hours, then most of that food should be gone at the end of two hours more than half should, should be gone. And the number that we use there is what we call the 60% retention. So at two hours, about 60% is still left in the stomach. By four hours, less than 10% should be left in the stomach. And so that's how we decide if someone has slow gastric emptying if at the end of four hours you have more than 10% in the stomach.
[00:07:21] Jill Brook: Okay, perfect. So, do you mind explaining what happens after the time in the stomach and what the time and transit looks like then?
[00:07:30] Dr. Linda Nguyen: So after the stomach, then in the small bowel it can take anywhere from two to six hours for things to move through the small intestine.
Anything over six hours is considered slow for motility. And then in the colon it can take up to 59 hours for things to move through the colon and exit. And in patients where the stools or whatever is in the colon for more than 59 hours, then it's considered slow.
[00:08:06] Jill Brook: Okay. And so it's a little bit interesting to me that in POTS it seems like it can get messed up in either direction. Do you mind talking more about that, the fast or the slow motility?
[00:08:18] Dr. Linda Nguyen: Yeah. In part because the stomach, which is sort of the part that we think about the fast motility on with nausea.
When you eat the upper part of your stomach is supposed to relax, to make room for food, right? So for Thanksgiving, if you eat the appetizer, the Turkey and the second, Pumpkin pie, the stomach is relaxing. So you can fit all of that. That relaxation of the stomach is under vagal control.
So if the stomach does not relax appropriately, then you can get fast and empty. Then in terms of the slow emptying, there's the stomach that, it contracts to grind the food down to particles that are less than two millimeters before it goes into the small bowel. And so if there is a problem where the stomach isn't contracting appropriately, then it can take a long time to break the food down into small particles, and then it gets into the duodenum or the small intestine.
And if the motility or the contractions of the small intestine are disorganized or disordered, it can cause sort of a backflow. So it's not just the stomach, it's like the upper stomach, the lower stomach, the valve of the stomach, the small bowel. Any of those areas can be disordered. Why one over the other?
We don't know that. Why do some people with POTS have fast emptying and others have slow emptying? We don't know.
[00:09:57] Jill Brook: Okay. And can I ask, what happens if the food sits too long? So if the slow motility is the problem and the food sits there too long, sometimes you hear people talk about, oh, the food starts to rot in your system.
Is that a myth or can that actually happen? Like, do secondary problems happen from the food sitting there too long?
[00:10:17] Dr. Linda Nguyen: I mean, it doesn't necessarily rot in terms of Getting mold, or when you think about like rotting food in your refrigerator that doesn't happen. But what happens is, let's say the food isn't digesting and let's say you belch, right?
And you belch and some of that food may come back up and you're tasting the acidity of the food. Or if you don't and there's food there and you go to eat the next meal, there's less room in your stomach, so you feel full more easily. So having food sitting in your stomach causes fullness, that bloating feeling you can cause nausea, vomiting, and then the next meal is more difficult to eat.
[00:11:06] Jill Brook: So you and your team recently did a whole study on POTS GI motility and you had some kind of cool technology. Do you mind talking a little bit about what you did in that study?
[00:11:19] Dr. Linda Nguyen: Yeah. So, it was a retrospective study and these are patients who were having a number of GI symptoms and most commonly nausea, vomiting, and or constipation.
And what we did was a test called a Smart Pill, which is this capsule that you swallow and it measures pressure, temperature, and pH. And based on those three parameters, I can tell you how long it's been in the stomach, the small bowel, and the colon. So you can track as it's moving through the gut. And there are normal values.
And so what we did was we took patients who had the smart pill study done. As well as autonomic testing. And then we looked at those with and without POTS on the autonomic testing. So we didn't rely on the history of POTS or not. We wanted to look at patients who actually had autonomic testing that confirmed that they had POTS.
And so then we went back and kind of compared the two groups in terms of age, race, symptoms ,diagnoses, and then looked at the transit time. So how long it took for the capsule to go through the system. And what we found, and it wasn't surprising, was that our patients with POTS tended to be younger than patients without POTS.
The symptom characteristics were the same. So again, both groups had nausea and vomiting but when we looked at the transit time, it was not so much the stomach that was different. It was a small bowel. So about a quarter of patients with POTS had slower transit through the small bowel, which can cause nausea, bloating. Slow small bowel transit also increases the risk of developing something called small intestinal bacterial overgrowth or SIBO, which is bacteria that is normally present in the gut, but because of the slow motility, it stagnates and it builds in the small bowel and that can cause additional symptoms.
[00:13:40] Jill Brook: So, is what you're talking about with the slow motility in the small bowel or in the small intestine, is that different than gastroparesis? Does gastroparesis specifically refer to what's going on in the stomach? Is this a separate problem?
[00:13:58] Dr. Linda Nguyen: Yeah, yeah. So gastroparesis is specifically stomach. If the small bowel is slow, we generally call it chronic intestinal pseudo obstruction. It's not the most accurate clinical description of it.
In that, historically that diagnosis of chronic intestinal pseudo obstruction. Is more along the lines of patients having symptoms like a mechanical bowel obstruction and the small bowel is dilated and you can see it on imaging like CT scan or x-ray, but there's no mechanical blockage. And these patients, the bowel isn't dilated.
They don't have those obstructed symptoms, but things are moving more slowly. So more of like a small bowel dysmotility.
[00:14:48] Jill Brook: And then when it gets to the colon, does it get more normal again?
[00:14:52] Dr. Linda Nguyen: In our study we had patients with slow colonic motility. But there was no difference between the POTS and the non POTS patients. So, okay. About, a third of patients had slow colonic motility, but that was not different than the non POTS.
[00:15:14] Jill Brook: Population. Oh, so that, is that just more common in the general population? So POTS patients don't stand out on that?
[00:15:21] Dr. Linda Nguyen: It's not necessarily that it's more common in the general population. Constipation is common and we're testing a group of patients with symptoms of constipation. Mm-hmm. So we're not necessarily looking at healthy volunteers with no GI symptoms that we're comparing with.
We're comparing with a group of patients who also have nausea, vomiting and constipation.
[00:15:48] Jill Brook: Okay, so this all starts to sound pretty complex because people can either have their motility be too fast or too slow. It could be in their stomach or it could be in their small bowel or even in their colon. What kinds of treatments exist to help people?
[00:16:04] Dr. Linda Nguyen: Yeah. Well, it goes back to the symptoms and is it too fast, too slow? Or normal. And stepping back a little bit especially with the nausea sometimes the nausea actually doesn't even come from the stomach.
It can be coming from the brain. So if you think about nausea, for example, in patients who are getting chemotherapy, right? The chemotherapy's not affecting the stomach. The chemotherapy is triggering the nausea center in the brain. For people who have motion sickness and get nausea, there's no problem with the stomach, right?
It's the vestibular systems in the ear that's causing the nausea. Just because someone has nausea, it doesn't mean it's coming from the stomach. It could be coming from the ear or the brain. And so it helps to try to tease out like what's causing the nausea. So in patients with POTS who tell me that every time I stand up, I get nauseous, then I start thinking that maybe it's the POTS, that's the issue, not necessarily the stomach.
Then you treat the POTS. But let's say someone who has Tachycardia and they have slow stomach emptying. And the nausea is after eating. Then I may use something like pyridostigmine or mestinon, which I'm sure you're all aware of, helps to treat the POTS symptoms and the Tachycardia, but it also accelerates motility, so you get a two for one with that. Smart. And so the other things that I would use is that if someone say has nausea, fullness but their stomach emptying is fast because the upper part of the stomach is not relaxing, I'll use a medication called buspirone it's an anti-anxiety medication, but it helps with relaxation of the stomach.
So that can help with the nausea, the symptoms. And we know that the brain and the gut are interconnected. It's not to say that anxiety is the cause of the symptoms, but when you stand up and you're tachycardic and you're dizzy and you're feeling nauseous, it's normal over time to develop anxiety, which worsens the GI symptoms.
Because what happens is we know that anxiety increases your sympathetic activity. Mm-hmm. So that, especially if you have Hyperallergic POTS, it increases that activity. And it can further alter GI physiology as well as sensation so it can lower the threshold for fullness, pain, nausea.
Wow. So the buspirone helps to relax the stomach, but it can also help treat the anxiety, which again, it's a two for one, that you help decrease the symptoms that are associated with POTS, with chronic illness, but also improve the nausea.
[00:19:21] Jill Brook: Okay. Oh, that's great. And so, It sounds like there can be so many root causes. You had talked about how a hyper adrenergic state can make digestion worse, but then you also mentioned the vagus nerve. And then I think you also, I don't know if general neuropathy is similar to the vagus nerve angle or if that can be its own separate cause, but I, I guess when we think about POTS, we think about sort of almost this tangled web of, of threads and we don't completely understand all of them, but we know that there's some angle of sympathetic state and some angle of hypovolemia and some angle of neuropathy or vagal nerve tone. And do any of those seem like stronger influences on GI symptoms to you, or does it seem like it's all just like a giant mess of everything?
[00:20:17] Dr. Linda Nguyen: It's a giant mess of everything. Yes. And we try our best to tease it out and as a gastroenterologist, I'll try to explain how I think of the autonomic nervous system as opposed to a neurologist view of the autonomic nervous system. So it's a very simplistic view to start with. And so I think of the autonomic nervous system in terms of the sympathetic and parasympathetic, parasympathetic being, being the vagus so it's like a seesaw, right? I don't think of it as general neuropathy of the autonomic nervous system, but I think about it more in terms of the imbalance of it.
So the sympathetic nervous system, when you're under stress, like when you're being chased by a bear, it revs up. It's supposed to rev up. So having, an increased sympathetic system is not a bad thing, especially when you're being chased by a bear. But it's supposed to calm down when you eat.
So rest and digest is when your parasympathetic nervous system comes up, then it comes down. So when you have the sympathetic nervous system, way up high here, like in hyperadrenergic POTS, chronic stress, chronic anxiety, and when I say chronic stress it's both physical and emotional. Chronic stress and the additive effects of stress.
Then if you think about the parasympathetic nervous system when you're resting or when you're eating, it has to work a lot harder to get up because the sympathetic nervous system is starting up higher than it's supposed to be. So that's kind of how I think of the autonomic dysregulation and how that can affect the GI tract. In terms of when you think of more like a neuropathy, just like the muscles in our hands and feet.
There's the motor component, so the nerves that work for the muscles to contract and to move things. So the gut has the motor nerves. It also has a sensory nerves. So when you touch something, it tells you if it's hot, cold, sharp, dull in your stomach. It tells you, if you've eaten, eaten something spicy, cold, hot tells you when you're supposed to be full.
So there's the sensory component uh, of your digestive system. So, In patients with POTS, especially if there's a small fiber neuropathy component to it, then it may not be just the motor part that's affected the sensory part can be affected so that you may eat a cracker and it feels like you ate an entire Thanksgiving dinner because you have like a sensory neuropathy of your stomach.
Kind of like with diabetes, where you get a peripheral neuropathy and someone puts, a sheet on your hand and it feels like it. It's the most painful thing in the world. That same thing can occur in the stomach. They eat a cracker and it felt like you just ate a whole buffet.
[00:23:39] Jill Brook: Oh, that's so interesting. Wow. So I know in your biography it mentions an interest in overlaps with Ehlers-Danlos Syndrome and chronic fatigue syndrome, Myalgic encephalomyelitis. In your patient population, do they tend to have similar problems to the people who have only POTS or when they have those in addition to POTS, do you see different symptoms or different problems?
[00:24:09] Dr. Linda Nguyen: Yeah. Well, the reason I'd become interested is really more because I was seeing patients with POTS and EDS and ME/CFS and I was trying to figure out why I was seeing all these patients with similar overlapping conditions why that's the case. I think there's a lot of research that needs to be done to figure out what the underlying pathophysiology or the mechanism is. I suspect it's sort of the a neuro immune dysregulation, so the nervous system, the immune system somehow being dysregulated and causing the brain fog, fatigue, POTS, gi dysmotility. What that is is way beyond my realm of expertise and research.
But just because we don't know the cause and the triggers, that doesn't mean that we can't help patients. I'm oftentimes, very upfront with patients if I don't know an answer to something, I'll say, I don't know the answer. I don't know why this is happening, but I believe you, I'm going to try to help you to the best I can, but where the science is right now, I don't have the answer as opposed to saying, it must be you because I don't know the answer.
[00:25:38] Jill Brook: Right. And that's so huge right there.
[00:25:41] Dr. Linda Nguyen: It's not me, it's you.
[00:25:43] Jill Brook: Well, we so appreciate physicians like you and can I ask, did you learn this in medical school? Was this your area of research or how come it seems like there are so few gastroenterologists who know about this area?
[00:25:59] Dr. Linda Nguyen: You mean of POTS or of the neuro GI motility part of it.
[00:26:06] Jill Brook: Well, I was going to say POTS and Ehlers-Danlos and ME/CFS. And it, it seems like you've put some puzzle pieces together that I've never really heard very many other GI specialists talk about.
[00:26:18] Dr. Linda Nguyen: Yeah. So, one, I definitely did not learn this in medical school, nor did I learn it in in my residency or GI training.
So I did train in GI motility and physiology. And so when I came into practice, I was seeing patients with motility disorders and disorders of brain gut interaction. At that time we were calling it functional GI disorders. But when I came to Stanford, this was back in 2008 we have a POTS clinic, we had an ME/CFS clinic and I had my GI clinic and I would get referrals and I started to notice that it was the same team of doctors taking care of a lot of patients with similar problems. Because of this, and I wasn't trained in this, but I needed to learn what was going on.
So I learned from the POTS doctors, I learned from the ME/CFS doctors and every time I refer a patient to a specialist and they send the report back to me, I would read it and then go up and look up something. And I'm fortunate here because we do have multidisciplinary case conference that we do once a month with our autonomic neurology group.
So in our multidisciplinary conferences, we either discuss topics just in general. Like most recently we talked about autoimmune gastrointestinal dysmotility, how to diagnose it, when do you think about it, and what are the treatment options.
And then we also talk about patients whom we share that may be puzzling ... more complicated than the usual complexity of patients with POTS and GI dysmotility.
[00:28:13] Jill Brook: Oh, well I'm so happy that Stanford is embracing the complexity. That is great. because I don't know that there's that many places that are doing that.
I guess as we finish up, are there any other final thoughts you have for patients trying to get help from their doctors? Like for example, is there anything that helps you help them? If patients come to you and maybe they have kept, I don't know, tabs on their diet or their pooping habits, or is there anything that makes it easier for you to help them?
[00:28:48] Dr. Linda Nguyen: One, what helps is what are your goals for coming to see me? Whether it's I want to know the diagnosis or what's going on, or I don't care what the physiology is, I just want to feel better. And it's the nausea that is bothering me. And the reason I say that is that, everyone who comes to see me has different goals that they want to achieve.
Mm-hmm. And so the best way for me to help you is to know what your goals are coming in. I actually love it when patients have a summary of their medical history, not necessarily everything that you've eaten and your pooping diary, that that doesn't really help too.
Okay. But if you were healthy until the age of 25 when you got food poisoning and then all of a sudden things changed, then that's something that is helpful. And then with the symptoms, like what makes it better, what makes it worse, and of those symptoms, which ones are the most bothersome?
A summary of what testing that you've had done. What medications or what things you've tried and what happened with it. Did it work? Did it not work or did it work? But you just had such severe side effects that it just wasn't worth taking. Mm-hmm. So all those things are helpful.
And then, other things that that play a role in the symptoms is that patients with POTS often have other issues like migraine headaches, fibromyalgia, disordered sleep, are probably the three most common things that I see. And so if you don't have someone who's helping to take care of those issues, it'll also affect the GI tract, because that's part of that chronic stress and the increased sympathetic activity.
It's not stress because something bad happened at home stress, but this is like physical stress that is affecting mm-hmm.
[00:30:58] Jill Brook: Okay, great. That's great information because I know that's lots of patients. They wait so long to get in to see someone like you and they really want to make the most of it.
So that's so helpful. Well, Dr. Nguyen, thank you so much for your time today. I know you need to get back to the clinic, but we're so grateful for your ongoing work to help POTS patients in the clinic and through your research and with your whole team. So please thank all of your co-authors and team for us as well.
We're really excited to have people of your caliber looking into our issues.
[00:31:28] Dr. Linda Nguyen: You're very welcome, and like I said, we're here, we're learning. And I hope one day that we will have more answers and I would have to say that there is hope there compared to where things were 15 years ago.
I do think there's more awareness, more people are looking into this. So, there is hope and I wanted to make sure that I extended that hope with community.
[00:31:57] Jill Brook: Wonderful. Well, thanks for all your good work and hey listeners, that's all for now. We hope you enjoyed this episode. We'll be back with more next week. But until then, thank you for listening. Remember, you're not alone and please join us again soon.
