I'm Chris Mogenson and I'm a team leader dietitian specialist at Brigham and Women's Hospital in Boston, Massachusetts. I appreciate the conference committee inviting me to give this talk today. My topic is the effect of obesity on nutrition support choices. My disclosures are here. Today I'm going to talk about nutrition assessment of patients with obesity, energy requirements, protein requirements, the route of feeding, enteral versus parenteral, and then long-term critical care and beyond. All patients require a nutrition assessment when they're in the ICU, and it's especially important for patients with obesity. Malnutrition changes clinical outcomes and the approach of the critically ill patient with or without obesity. We conducted a study of 1,799 patients who were critically ill with obesity and had nutrition assessments conducted. I'm just going to focus on the nutrition assessment piece and critical care outcomes. You can see here in this table, when we look at nutrition status, those with malnutrition had a 58% increased chance in the odds of mortality compared to those who were well-nourished. Here in our Kaplan-Meier curve, we have 100% follow-up of these patients out to one year. You can see those patients with any degree of protein energy malnutrition have higher odds of mortality than those without malnutrition and obesity. Our approach to the nutrition assessment in patients with obesity is very similar to other patients who don't have obesity. We look at their height and weight. We look for weight history. One thing that's unique, though, is to look for a history of bariatric surgery. We often have patients with obesity who've had bariatric surgery in the past and may have lost weight, but they may still have class 1 obesity or they may have regained weight over time. What type of bariatric surgery is important to get you thinking about micronutrient deficiencies and any challenges with enteral axis? We want to get a handle on recent diet history. Has the patient been eating poorly before this admission or were they transferred from another hospital? We want to get a sense of their recent nutrition support history. Many times patients aren't fed or there are challenges feeding them at other hospitals before they come to a tertiary care center. Then the nutrition-focused physical examination is very important. We want to look for areas of muscle wasting and fat wasting. You may think it's hard to find, but if you look carefully, you actually can find it. We look at the temporal muscles. We'll look at pectoralis, trapezius, deltoid. You may be surprised to find how much muscle wasting you find. Fat wasting can certainly be a little bit harder, so you want to look for redundant skin on the triceps and pannus. This will give you a sense of, has this patient lost a lot of fat mass? Some will tell you that it was unintentional weight loss. Then finally, assess for signs and symptoms of micronutrient deficiencies, which is particularly important for our patients who've had bariatric surgery. We look for signs of B vitamin deficiencies, vitamin C deficiency, zinc deficiency. Many of these can show up as a rash in the skin, or cracks in the corners of the mouth, or in the case of vitamin C, corkscrew hairs in the arms and legs. When we assess for presence of malnutrition, the Academy of Nutrition Dietetics and the American Society for Parenteral Nutrition Clinical Characteristics are often used. I'm not going to go through all of these details, but we do evaluate six clinical characteristics, energy intake, unintentional weight loss, loss of subcutaneous fat, loss of muscle mass, accumulation of fluid or edema, and reduced grip strength. Two clinical characteristics are required for diagnosis. Patients with obesity may have malnutrition in the context of an acute illness or injury. We see this often in patients with severe COVID-19 or in the context of chronic illness. These may be your patients with COPD or malignancy, where they've been having nutrition problems for a prolonged period of time and unintentional weight loss. The presence of malnutrition shortens your nutrition support timeline. Again, whether or not your patient has obesity or not, you still need to think of where they're starting from. If your patient is nutritionally intact, you have about seven to 10 days to get enteral nutrition to greater than 60% of energy and protein requirements. If you're not there, you have to think about supplemental parenteral nutrition or why. Look into why is your patient not being fed well. For your malnourished patient, we don't have good data, but the timeline's probably shorter. Malnourished patients don't have the reserve that nutritionally intact patients do. You might be looking at three to five days, but we certainly do need more work in this area. If your patient has malnutrition, track what they're getting and try to optimize how you're feeding them. Now let's talk about energy requirements. Hypocaloric high-protein feeding strategy is recommended for critically ill patients with obesity. Why do we do this? Well, pre-existing comorbidities may be exacerbated with excessive energy delivery. We think about diabetes, hyperlipidemia, restricted lung disease, heart failure, and fatty liver disease. We want to prevent making these things worse. A lot of the studies that have looked at hypocaloric high-protein feeding are really looking at nutritional outcomes because you have to think about if you're underfeeding your patient calories, are there negative nutritional consequences? This was an early study done by Berg and colleagues looking at patients requiring parenteral nutrition and there were nine patients who received hypocaloric feeding, seven patients received standard feeding, and the most important outcome here was there was no significant difference in nitrogen balance and no significant difference in mean weight loss. Both groups lost weight. So this suggests that this is a viable feeding option without negative nutritional consequences for our patients. How about clinical outcomes that we care about? This was a study by Dickerson and colleagues that looked at hypocaloric feeding, which they defined as less than 20 calories per kilo, and eukaloric feeding, which was the control group defined as greater than 20 calories per kilogram. And most of these patients were enterally fed if you received some supplemental parenteral nutrition when there were problems with their feeding, but this was primarily an enteral nutrition study in the ICU. And what was interesting, as you can see here, is that there was a significant decrease in duration of ICU stay with hypocaloric feeding, almost 29 days in the eukaloric patients versus about 19 days in the hypocaloric patients, a trend in reduction in duration of mechanical ventilation, so about 24 days versus six days. So we missed statistical significance here, but it certainly was a trend. And then duration of antibiotic therapy was also reduced, so about 27 days versus about 17 days. So this was statistically significant. And no big change, no significant difference at all, actually, in survival. So this suggests some beneficial, meaningful outcomes when this type of feeding strategy is used. So how do we calculate the energy requirements? In 2009, the Society of Critical Care Medicine, the American Society for Parenteral and Enteral Nutrition, came up with their original guidelines for feeding critically ill patients. How do we intervene in critically ill patients nutritionally? And they gave three options for feeding critically ill patients with obesity, if you can measure their energy expenditure, give 60% to 70% of their estimated needs, or you could do 11 to 14 cals per kilo of actual weight, or you can do 22 to 25 cals per kilo of ideal body weight. Lots of choices. So at my institution, we decided to look at this in patients that we had done in direct calorimetry. We had 31 patients with a BMI over 30 who had energy expenditure measured. We had 20 patients in the BMI of 30 to 50 range, and we had 11 with a BMI greater than 50, and we compared measured resting energy expenditure, taking 60 to 70% of that. We took the middle of the range, 65%, and compared that to the Society of Critical Care Medicine announcement guidelines, as well as two other predictive equations. And what we found is that the 11 to 14 cals per kilo of actual weight worked best for a BMI of 50 or less, and 22 to 25 cals per kilo correlated best for patients with a BMI greater than 50. Ideally, if you can measure your patient's energy expenditure, you should do it. You would start with that 60 to 70% of measured resting energy expenditure. So how about protein requirements? You may think that patients with obesity have plenty of depot of fat stores and protein stores, and why can't they draw upon this to recover from their critical illness? This is a very small study of 17 patients published in 1991 by Jeevanandam, but it gives you a little bit of a glimpse into changes in metabolism in critically ill patients. These are folks who've had trauma, patients with obesity, and patients without obesity. In this graph on the left, the order of the macronutrient oxidation is fat, then carbohydrate, then protein. As you can see, the trauma patients with obesity had nearly equal fat and carbohydrate oxidation and reduced protein oxidation, whereas the trauma patients without obesity had much, much higher fat oxidation compared to carbohydrate and protein. And then in our graph on the right, protein turnover in trauma patients with obesity is much higher compared to those patients without obesity. And then when you look at protein synthesis, protein synthesis is reduced in trauma patients with obesity compared to those without. So again, small study. We certainly would need more, and some unpublished data out of my group is that we are seeing looking at metabolomics in critically ill patients with obesity. We're seeing some signals that this may actually be correct, so stay tuned for our analysis of that data. So what do we do for protein requirements? The more protein is mobilized in patients with obesity, we need to provide adequate protein to preserve lean body mass while restricting calories. So for class one and class two obesity, we're going to give at least two grams per kilo of ideal body weight or more. For class three obesity, we're going to give two and a half grams of protein per kilo of ideal body weight or more. So how about the route of feeding? In theory, this should be easy, right, if the gut works, then you can safely use it. Many patients requiring mechanical ventilation have orogastric tubes in place to make it very easy to start natural nutrition. However, watch out for patients who've had bariatric surgery. So on the left here, we have an unmodified GI tract where a feeding tube, whether it's nasogastric or orogastric tube, can be placed easily or you can fairly easily get post-pyloric access, but look at the rheumogastric bypass. Think about trying to traverse this surgery to get a feeding tube in place. Think about the safety of feeding into that small pouch. What do you do if you want post-pyloric access? So you might engage a bariatric surgeon to help you with your enteral access. Sleeve gastrectomy, a lot easier for short-term enteral access. You can feed into that sleeve pretty easily, but for both rheumogastric bypass and sleeve gastrectomy, when you think about long-term enteral access, it poses much more of a challenge. You can't easily do a percutaneous endoscopic gastrostomy in these patients, so engage the bariatric surgeon or your advanced endoscopist to help you with decisions if your patient does require long-term enteral access. So your enteral formula choice in general, you're looking at a high-protein, low-calorie formula. You're looking for a formula with greater than 30% of calories from protein, which generally will work out to be greater than 80 grams of protein per liter. You may still need modular products to meet protein requirements, and you may need disease-specific formulas anyway. For example, electrolyte restricted if your patient has acute kidney injury, just depending on their complications. So monitoring and adjusting, just like any other critically ill patient, is quite important. You may find that you need to restrict electrolytes, and that makes your feeding a little bit more complicated. You also have to think about calorie-containing medications. For example, propofol, which will give you 1.1 cals per ml from fat, and large volumes of medications mixed in D5, for example, a bicarb drip. And these may be very short-term therapies, so it's important to just monitor them and adjust your feeding plan accordingly. And some of them, like propofol, can make your feeding plan really difficult, because some of our very obese patients have very large propofol requirements for sedation. So you may be looking at a patient getting 50% or more of their energy requirements from propofol, and so what you're giving for your nutrition regimen is really mostly protein. You gotta make sure you're getting enough carbohydrate in there for those obligate carbohydrate users, like your brain, your kidneys, and your red cells. So very quickly, let's zip through a natural nutrition case. We had a 50-year-old man with type 2 diabetes, obstructive sleep apnea, hypertension, class 3 obesity, admitted with severe COVID-19, and he was intubated. We received a consult for tube feeding via his orogastric tube. He had class 3 obesity, as you can see in his anthropometric data, and so we used the 22 to 25 cals per kilo of his ideal body weight, and two and a half grams of protein per kilo of his ideal body weight to calculate his requirements. So we can use a very high-protein formula here. So one that has one cal per mL and 87.3 grams of protein per liter will work out very nicely. You might play a little bit with your rate options. If we look at 65 mLs an hour, that would give 1560 calories, but only 136 grams of protein. Let's bump that up to 75 mLs an hour. We're looking at 1800 calories, looking better compared to the energy needs of max of 1818 calories, but again, only 157 grams of protein, so we're still not quite there. This is where your whey protein powder comes in or what other protein modular you have at your institution. So I'm showing you the math here that you can read on your own and the goal in the interest of time, and the goal would be the very high-protein formula, 65 mLs an hour. We would give two packets of the whey protein four times a day, very nice and easy for our nurses, and that would be 1760 calories and 184 grams of protein per day, meeting our patient's needs. So how about venous access and parenteral nutrition requirements? Well, venous access is usually less problematic than enteral access, whether your patient has history of bariatric surgery or not. Any central line may be used for parenteral nutrition as long as the tip is confirmed to be central. So sometimes people see peripherally inserted central catheters and say, oh no, can't use that for parenteral nutrition. As long as the tip is in the right spot, you absolutely can. We do need to dedicate a limit for parenteral nutrition once it's started to reduce infectious complications and really a fresh stick for parenteral nutrition really may not be necessary. Some institutions feel that's important. We reviewed the literature. It's very weak, and so we felt saving our patients a procedure was much more important. So if a patient has a preexisting central line, we will dedicate a limit from that point forward for parenteral nutrition. So parenteral nutrition is indicated when enteral nutrition is contraindicated. So if your patient is hemodynamically unstable on multiple pressers, you're worried about ischemic bowel, you have massive GI bleeding, you have a patient who keeps vomiting with their enteral nutrition, other signs of enteral intolerance, these are things that would be contraindications to enteral nutrition. You need to think about parenteral nutrition. But it may pose volume challenges in the critically ill patient with obesity to give enough protein and limit calories. So you need to work closely with your nutrition support pharmacist to develop that safe and stable parenteral nutrition solution. So the maximum amino acids are generally between 7% and 8%, so that's 70 to 80 grams of protein per liter. So if we think of our prior patient who needed 180 grams of protein, that's a lot of volume. So that can pose a challenge. And then if you want to have dextrose and lipid in the bag, we actually have minimum concentrations once you add lipid into the bag. So you're looking at a minimum of 10% dextrose and 2% lipid. And this can lead to some overfeeding. So really working with your pharmacist is important to get the right balance of macronutrients. You might need to be creative and say, well, we'll give our lipids on the side, or we might give our lipids a couple of times a week. That might help with your volume management. But really, it's quite challenging, and that could be a whole talk on how to do the calculations. I'm not giving you an example on this one, just in the interest of time. So thinking about micronutrients. So parenteral nutrition patients will automatically have vitamins and trace elements added to the solution. And so for your enteral patients, consider a standard multivitamin mineral supplement. It takes some time for the tube feeds to get up to goal to assure your patient is getting the full complement of micronutrients that they need for metabolism and to support recovery, particularly, say, after surgery. Now, if your patient has a history of bariatric surgery, you want to find out what kind. Roomwide gastric bypass carries more micronutrient risk than some of these other surgeries, say sleeve gastrectomy. You want to get that good history. Has the patient been able to take their vitamins leading up to this admission? Pay attention on physical exam and check micronutrient levels if indicated. So there are many times that we're getting surveillance micronutrient levels when our folks with a history of bariatric surgery have come in. If your patient has a history of bariatric surgery and they were admitted with severe vomiting, I cannot emphasize this enough, give thyme, and the severe vomiting depletes thymine levels, increases risk for Wernicke's encephalopathy, it goes on too long, you might be looking at Wernicke-Korsakoff syndrome. If your patient is severely malnourished, with obesity or without, and you're starting any mode of nutrition support, give thymine. Again, thymine needs are increased in your malnourished patients that you're starting feeding. If your patient has had severe diarrhea or high alpha fistula, you might want to consider checking a zinc level because they have higher zinc losses. So now moving into long-term critical care and rehab settings, your patients with obesity shouldn't stay on hypocaloric high-protein nutrition forever. As your patients improve and start moving into the chronic phase, you give more calories and less protein, but there's less literature to guide us in this area. So if you have access to indirect calorimetry, increasing calories towards the measured energy expenditure is a really good start. At Brigham Women's Hospital, we generally give 18 to 20 calories per kilogram of actual weight. We give at least a gram of protein per actual weight as our patients are moving into that long-term and sort of rehab phase. Other institutions may use predictive equations and subtract calories. So they might calculate off of a predictive equation and subtract 500 calories to promote some weight loss if it's indicated. And then ideally, you're going to adjust your nutrition support regimen before the patient transferred to rehab and give the rehab a summary of why you fed the patient the way you did. There may be questions. You want to monitor improvement for strength, endurance, and wound healing. This gives you a sense of are you giving enough calories and enough protein, and you might need to give more energy, more protein if your patient's not making progress. Other things to think about. Try to get accurate weights. You may be surprised to your patient's weight change. So as they're in your ICU for a prolonged period of time, you may find patients with BMI is in the low 30s. They quickly lose weight. They might even diurese and they get down to a BMI less than 30. So be ready to reassess if your patient moves from a different obesity class. If they move from class 3 to class 2, that's going to change your protein delivery. Or if they move from class 1 down to an overweight category, that changes everything. Now for patients who've extubated and their oral diet is advanced, they may need some encouragement to eat enough food to support recovery, and that supportive environment is key to their recovery. Some patients fall into the trap of, ah, I've been losing weight because I've been sick. This is a great opportunity. Or they may feel ashamed that they are obese and they're eating, and they may not feel like they're allowed to eat. And I've seen both situations happen, and bad outcomes from that. Poor healing, and in some cases, need to resume nutrition support therapy. So encourage your patients, you know, talk about food for fuel and food for recovery. And this is not the time to actively pursue weight loss by starvation. So in summary, patients with obesity may admit with pre-existing malnutrition or become malnourished, just like any other patient in the ICU. Your careful nutrition assessment is going to guide your nutrition therapy, depending on the severity of malnutrition. Hypercaloric and high-protein feeding is appropriate during the acute phase of your patient's illness. Be careful with enteral access for those patients who've had bariatric surgery. And work with your pharmacist to ensure safe and stable PN prescriptions for patients who need it. You want to watch for weight change, and adjust energy and protein delivery if needed. Increase your energy delivery, decrease your protein delivery when your patients are getting ready for rehab. And really, for your patients taking an oral diet, encourage adequate oral intake. Watch for those inappropriate or maladaptive eating behaviors. Encourage your patient to eat enough to heal and recover, get out of the hospital, and get out of rehab. So here are some of our selected references here, and I thank you very much for your time.

obesity

nutrition support

malnutrition

enteral feeding

bariatric surgery

micronutrient management