Hello. My name is Ashley DePriest. I'm the Assistant Director of Clinical Nutrition at Emory University Hospital in Atlanta, Georgia. Today I'm going to be talking about infusing life into nutrition in the ICU. I have no disclosures to report. The objectives of this presentation are first to review current guidelines and best practices for the use of parenteral nutrition in adult and pediatric patients. We'll discuss optimal strategies for provision of micro and macronutrients through parenteral nutrition and examine the risks and benefits of early versus late and supplemental parenteral nutrition in critically ill patients. Today we'll start by talking about initiating nutrition support and discussing the difference between early versus late parenteral nutrition and specifically how do we define early versus late. We'll talk about the amount of energy and protein we need to reach and when should we reach protein and energy goals. We'll review feeding complications and when we should be adding and considering supplemental nutrition. And then finally we'll talk about what's next, best practices for transitioning parenteral nutrition to enteral and oral. Initiating nutrition support, early versus late PN. In order to talk about the timing of nutrition support, we first need to consider the phases of critical illness. Historically we've talked about early versus late when talking about nutrition initiation in terms of the first week or the first 24 to 48 hours. But now more and more we're starting to consider three phases of critical illness in order to determine when we should be initiating and how much we should be initiating of nutrition support. The early acute phase is defined as hemodynamic instability, metabolic derangements that are not influenced by nutrition and is typically that first day or two of illness or injury. The late acute phase is defined by hemodynamic and metabolic systems are stabilizing. You can still have significant muscle wasting and it's usually around days three to seven of your illness or injury. And lastly you would have the recovery phase which is defined by improvement in the initial injury or illness. You'll see anabolism happening more and more so this is when we may be able to have an impact on body composition with using nutrition intervention. And this is typically seen at least one week after the initial injury or illness. Now sometimes patients may not enter into that recovery phase and what they may enter into is what we call chronic critically ill phase. This is defined by chronic inflammation. That chronic inflammation makes muscle maintenance difficult. It makes muscle building almost impossible. And again this is typically after that first initial week of injury or illness. Another period of critical illness that we don't often discuss but that has a major impact on how we decide when to start nutrition support is the pre-injury period. Patients can experience various weight changes prior to becoming critically ill or injured. They have different levels of nutrient intake prior to coming in and they may or may not be exercising before becoming critically ill. All of these things can impact if and when we would start nutrition support. For example, if a patient has experienced significant weight changes, had very poor nutrient intake prior to coming into the hospital, we may consider them severely malnourished and we may need to be a little more aggressive in providing nutrients sooner for a patient who comes in with a stable weight and good nutrient intake prior to admission. So what I'm defining and what I'm describing here is a malnutrition assessment. So on admission, all ICU patients should be assessed for malnutrition. The things we're looking for when we're assessing for malnutrition are significant weight loss, inadequate intake, but we also are performing, as dieticians, we perform a nutrition-focused physical exam where we're assessing muscle and fat losses. We may also be assessing for generalized or localized fluid accumulation, which may indicate low protein intake, as well as a reduced functional status, which traditionally has been defined as a reduced reduction in hand grip strength. That's not always feasible in the ICU, but when it can be done, it's useful. And any two or more of these criteria, a patient is considered malnourished, depending on the degree. So more weight loss, more muscle loss, less intake can be more severe. After we've assessed the overall nutrition status of a patient, the next thing we must consider before deciding if and when to start nutrition support is the gut and the ability of the gut to function. So during critical illness, the gut undergoes a lot of changes as well. Typically, on a normal patient, there is constant crosstalk happening between your gut microbiome and your immune system. This results in signaling and the production of many anti-inflammatory immune factors that help support a healthy immune system. However, in critical illness and injury, we get a loss of this gut function. There's a major change in the microbiome that converts it to a passive biome. This promotes inflammatory signaling, which reduces the overall healthy immune response. And this is why we begin to talk about some of the non-nutritional benefits of enteral nutrition. So even before we start to think about how much calories and how much protein we would provide a patient, we don't want to forget about the non-nutritional benefits of enteral nutrition. Providing even just trophic or trickle amounts of enteral nutrition to the gut can help to maintain and support appropriate GI responses. This includes supporting your commensal bacteria, keeping virulent bacteria from becoming overgrown, and maintaining those tight junctions within the GI tract, which also help prevent bacteria translocation. The other thing that even trickle or trophic enteral nutrition can do is to support the healthy immune response. Stimulating the gut can help promote T-helper 2 cells production over the T-helper 1 cells, and it helps to maintain mucosal-associated lymphoid tissue, MALT, and secretory IgA and GALT. All of these things help to support that very healthy immune response that is needed during critical illness. And finally, even trickle and trophic effects of enteral nutrition can help with the metabolic response as well. It can promote the production of incretin, which improves our insulin sensitivity, even in patients who are undergoing this inflammatory process. Now even though there are these wonderful benefits, the non-nutritional benefits to enteral nutrition, even when we cannot provide max amounts of calories and protein, we still have a few contraindications that can happen in the ICU. So for example, bowel discontinuity or obstruction, obviously you cannot provide enteral nutrition in those settings. Severe, severe malabsorption, I think we typically think, I typically think of a patient maybe with a GVHD or some sort of very severe diarrhea. It may not be appropriate to use the gut when it is just not functioning properly. Necrotizing pancreatitis can put a patient at very high risk when we try to feed the gut. Active GI bleeds, or if a patient is post-bleed with a very high risk for re-bleeding, we may want to hold off on stimulating the gut. Hemodynamic instability, there's a lot of discussion around this these days, but specifically if we are suspecting that there is very poor end organ perfusion, that is a case in which we may not want to feed the gut because we put the patient at risk of ischemia and necrosis, which is the next contraindication to enteral nutrition. And then finally, if we have severe electrolyte abnormalities, this could lead to paralytic ileus, or we'll talk a little bit later about refeeding syndrome. So all of these things may be indications as to wanting to not start enteral nutrition. Some considerations for pediatric population, obviously this is a very unique population. Many pediatric ICUs have many different types of illnesses and injuries, and so we don't treat every single patient the same. The big thing in thinking about feeding pediatric patients is that we want to want to try to anticipate their time to volitional state, because this may be more important for pediatrics than it is in adults, because our PEDS patients are still growing, they're still developing, so they have a very fast, much faster growth rate, and they can become malnourished much faster as well. It's also important to remember that even metabolically, these patients are not just smaller adults. They are in a growth period, and so many of their metabolic processes are going to be different than the adult population. So when we start to think about EN versus TN, we definitely have a few myths I think we need to dispel. There's a lot of conversation historically around whether parenteral nutrition is safe to provide for patients in the ICU, and so we have two big randomized trials to help us guide our practice in this setting. First, the calories trial was 2,400 patients. This was a mixed ICU population. These were patients that were deemed appropriate to receive enteral nutrition. The patients were randomized to either early EN or early PN within the first 36 hours of ICU admission. The patients received their intervention for at least five days, and they met 80% of goal nutrition needs. In this trial, there was no significant difference in length of stay or mortality in patients who received either early enteral nutrition or early parenteral nutrition. The second trial, Neutria 2, was again over 2,400 patients in a medical ICU population of patients with septic shock. Patients were randomized to EN versus PN 24 hours after intubation, and they received intervention for five days. Once again, no significant difference in infection, no difference in length of stay or mortality. So what does this mean? What do these trials tell us? Parenteral nutrition is most likely safe. It is safe in the patient population that we're serving. That infection risk, we think, has gone away as we have developed better protocols around keeping central lines clean, as well as better blood sugar control in the ICU. We used to use also something we called Hyper-OW. Parenteral nutrition was not necessarily tailored to patients, but rather we were providing very, very high amounts of calories, 3,000 plus calories a day, and driving blood sugars up into 3, 4, or 500. So now that we are better equipped to handle more appropriate parenteral nutrition orders and provide more appropriate amounts of calories, as well as blood sugar control and cleanliness with the nursing at the bedside, we find that parenteral nutrition is really safe to give our critically ill patients. So now as we start to get into whether we should be providing early versus late PN alone, because we've talked about enteral nutrition and maybe we're finding that there are contraindications, and so we're deciding whether we should be starting parenteral nutrition, we have to revisit those phases of a critical illness. First, in the early acute phase, once again, this is defined by hemodynamic instability, metabolic derangements that, again, are not influenced by nutrition. We know that the nutritional benefits of support are likely not to be effective during this phase. So in other words, the patient's body just really doesn't know what to do with nutrients when they are early in the acute illness. And so we would want to focus on some of those non-nutritional benefits of early EN during this phase. If we can't provide enteral nutrition, nothing is probably better than something. Again, PN is likely not needed as these IV calories and protein are not going to provide the same benefit to the gut that a trickle or trophic effect of EN can have. So in this very early acute phase, if the patient is not able to initiate enteral nutrition, we would not initiate parenteral nutrition. Moving into the late acute phase, when we start to see hemodynamic and metabolic systems stabilizing, we've become higher risk of seeing significant muscle wasting. And this is when we would certainly want to continue the non-nutrient benefits of enteral nutrition if the patient is able and they are tolerated. And this is a time period where if we are able to initiate enteral nutrition, we may start to trial titrating to goal. We would start to up the nutrition in a slow manner just to monitor for tolerance. And if we're unable to do that though, if there is a total contraindication to enteral nutrition, this is the phase in which parenteral nutrition should be considered. Again, patients are becoming more stable, their metabolic systems are stabilizing, they're able to then take nutrients and utilize them in a meaningful way. So this is where we would begin to provide calories and protein through a parenteral route. So when considering initiation of parenteral nutrition, there's a few things we need to think about. First, does the patient have central line access? And does that central line access have a dedicated lumen that can be for PN alone? We want to avoid disconnecting and reconnecting parenteral nutrition throughout a stay. And we also want to provide parenteral nutrition in a consistent manner throughout the day so that we can avoid shifts in blood sugar as well as volume and fluid. The next thing to think about when initiating parenteral nutrition therapy is the duration of therapy. If a patient is only going to need the parenteral nutrition for a day or two, it may not be really worth, you may not get those benefits out of providing that parenteral nutrition as you would if you're going to provide it over at least five to seven days. So for example, if your barrier to providing enteral nutrition is related to the intubation and the inability to put an NG tube in a patient, but once that patient is extubated, they most likely will be able to chew and swallow. Maybe they have a crib reform plate issue or maybe you're not able to get the OG tube down. And so once they're extubated, they can go ahead and start eating. And we know we're most likely going to extubate them in the next day or two. That's probably not someone I would be starting aggressive parenteral nutrition on. Nutritional status upon admission, we talked about kind of all the things that happen prior to a patient coming into the hospital. Are they eating well? Are they exercising? Are they healthy? Or are they losing weight, not eating well, already at a disadvantage starting in the ICU? And so if that is the case, if you have a patient that is already severely malnourished, that patient is already likely using up their supply of lean body mass. The body's breaking it down in order to use it for nutrients. And so that may be someone we would want to really start nutrition earlier and be a little more aggressive with. And then lastly, you want to make sure that you understand your facility's P.N. ordering timeline. Most facilities have a cutoff time to when you need to get that order in so that they can prepare the formulation and provide it to the patients in a timely manner. So for example, if you aren't able to get that order in in time, it could be up to 48 hours before the next time a patient can receive parental nutrition. So considering that in your timeline of whether it's needed to start or whether you could start other things within that time frame is always important. For pediatric parental nutrition in the PICU, it is not recommended to start it within 24 hours of admission. So very similar to the adult population. In that early acute phase of critical illness, the risk of overfeeding a patient because the patient can't utilize those nutrients in a proper way far outweighs the benefits, if any, of providing P.N. to a patient within the first 24 hours. So this is based off of a single randomized trial comparing early versus late. Once again, no differences in the groups in hospital or 90-day mortality. We also had no significant differences in the groups between the PICU length of stay or hospital length of stay. However, in the patient that was started on parental nutrition early, within the first 24 hours, they did have a significant increase in infection rates. So in this case, we do see that parental nutrition may increase infection. Again, this may be related to overfeeding in a time when the body cannot properly utilize nutrients, resulting in hyperglycemia, which we know increases infections. So holding off within that first 24 hours is important in your pediatric patient population. So let's move on to amount. What are the energy and protein goals, and when should we reach them? So before we start to increase our goal calorie, I want to touch a little bit on refeeding syndrome. Refeeding syndrome is historically described as a range of metabolic and electrolyte alterations occurring as a result of the reintroduction and or increased provision of calories after a period of decreased or absent calorie intake. So in other words, you have a patient that has just not been eating, is severely malnourished, catechetic, has no stores, no muscle that can be broken down and produced into energy. These are patients that are at very high risk of refeeding syndrome, which can result in a various number of cardiopulmonary issues, and ultimately could end up in death. Hypophosphatemia is the hallmark of refeeding syndrome, and that is hypophosphatemia in the setting of calorie provision. But you can also see low potassium, low magnesium, as well as other metabolic derangements. So it's always recommended to screen your ICU patients for risk of refeeding syndrome. The dietician should be doing this prior to initiating a recommendation for enteral nutrition or parenteral nutrition. You should, in patients that are at risk, you should check and electrolyte, serum electrolytes prior to initiation of any nutrition, which can include IV dextrose as well. You want to replete any low levels of electrolytes and start IV thiamine prior to the initiation of nutrition support. Again, make sure your registered dietician is on board. They can help create that plan for titration. And cardiorespiratory monitoring and Q4-hour vitals, which we know are already happening, maybe even more frequently in the ICU, should be considered in our very high-risk patients as well. Now, before we talk about how much we should be feeding someone, I want to touch a little bit on all of the different things that can affect a patient's metabolism in the ICU. Thinking about a basal metabolic rate, there's a lot of different things that can affect your basal metabolic rate, even when you're not critically ill. Your age can affect your BMR. Your gender and body composition, these are the three big things that affect the BMR, even in the non-critical care setting. But again, that phase of critical illness can also have an effect on your BMR. We talked about very early on how the body is really just not utilizing nutrients in the way that it normally does. So providing those nutrients is probably not going to help in any meaningful way. The next thing that can affect your metabolism is your inflammatory response. So during inflammation, the release of cytokines can result in an elevation of your metabolic rate and an elevation of energy expenditure. So in instances of very high inflammatory responses, you may actually see an increase in your metabolic rate and an increase in energy utilization. Organ dysfunction, so things like liver failure, can certainly disrupt your metabolic pathways. They reduce your enzymes or other cofactors that are required in metabolism and can really change how much you're utilizing and how appropriately you're utilizing your nutrients. Related to the inflammatory response, you also have hypermetabolic injuries, so things like severe burns, trauma, sepsis, certain cancers can create a very inflammatory but also high energy expenditure response in the body, and thus those patients typically need a lot more calories and protein than just your typical critical care patient. And lastly, there are various medications that can affect your metabolism, corticosteroids, beta agonists, vasopressors, sedatives and analgesics, as well as antibiotics, can all significantly impact the metabolism of a critically ill patient. Calculating estimated needs, so how do we know how much to feed a patient? Well, the gold standard has always been and is considered still indirect calorimetry, and this is in the case of both adults and pediatrics. In the case of when indirect calorimetry may or may not be available, the ESPEN guidelines suggest using a VO2 from PA catheters or a VCO2 from the ventilator in order to better predict, use predictive equations. There are various, there are a plethora of predictive equations that have been validated in a number of different settings. The one that is most commonly used for adult intubated patients is the Penn State 2003B, and for our pediatric patients, most commonly, we see the Schofield equation utilized in order to calculate energy needs. The thing to remember, these predictive equations are only about 60 to 70% accurate in adults, and it's even worse for pediatric patients. So, many institutions will, just for ease and time's sake, will use a simple weight-based approach, anywhere between 11 to 35 calories per kilo of body weight, depending on where they are in the face of a critical illness, as well as other factors such as body composition. That simple weight-based approach is both easy and most likely just as accurate as using a predictive equation, not quite as accurate as indirect calorimetry. So, as we start to feed the patient, and as we start to decide how much we should be feeding the patient, let's go back and revisit those phases of critical illness. So, once again, starting in the early acute phase of hemodynamic instability, metabolic derangements, again, patients cannot really take on those nutrients and utilize them in a very meaningful way. So, the name of the game here is to avoid overfeeding. We have to not forget that a lot of our medications contain calories and nutrients, such as dextrose and lipids. So, we want to keep an eye on that and include that in our calculations when we're feeding patients. The goal is to start low and titrate slow. So, we start low, slowly titrating over the next two to three days. The suggested targets, ideally measured by indirect calorimetry, would be starting at 25% of enteral nutrition on day one, 50% to day two, and then up to 75% on day three. Remembering to hold off on these titration goals if refeeding is suspected or if you find major drops in phosphorus with the introduction of calories. During this time period, you would also want to provide a moderate amount of protein, 1 to 1.2 grams per kilo. This is, once again, related to those metabolic derangements. We want to have a little bit of protein that helps keep off that burning of utilization of muscle mass for energy, but it also is not going to really be able to be incorporated, reincorporated into muscle. So, that's why we really keep it at a more moderate amount this early on. During the late acute phase of critical illness, again, metabolism is stabilizing, the hemodynamics are getting better. This is when we have a really high risk of significant muscle wasting if we don't provide enough nutrition. So, if we're not providing enough calories and protein during this time period, the body will start to find ways of creating calories, and its preference for that is to break down your muscle. So, as recovery begins, our goal is to get the goal as soon as possible. We want to feed as much and as soon as possible. So, don't forget to consider your dextrose and lipid-containing medications. And in this phase, this is where we really can start to see the potential of protein, and it's very, very important to start upping your protein during that late acute phase. We go up to 1.2 to maybe even 1.5 grams per kilo of body weight. This is for your standard critically ill patient. You have someone with a burn or a severe trauma injury, like an open abdomen, for example, those patients most likely will require a lot more protein, but we're not going to go into that much detail here on that, but this is when you would really start to provide that. Again, providing 100% of measured estimated energy needs. The most important thing, which I will touch on again later, is that we need to be monitoring the tolerance and adjusting our regimen as needed. Remember, these numbers, our targets, are most likely just guesses, best guesstimates, or estimates. And so, we need to make sure that we're monitoring for their ability to actually meet the patient's needs and adjust as needed. Lastly, in the recovery phase, as we really find that improvement, major improvement from that initial injury or illness, we want to start to really make sure we're meeting protein and calorie needs. This is often when transitions of care are happening, so it's very important to monitor closely and to collaborate with our other team members, including our speech therapists, our nurses, to make sure that energy and protein needs are being met. For example, this is typically a time when maybe a patient is going to start to be extubated. And so, having a multi-professional conversation or prior to extubation around whether we feel like this patient's going to be able to eat, swallow, chew, and take in adequate nutrients orally is very important. If for some reason we don't think that's the case, we need to try to keep a feeding tube in place as we extubate that patient. Or, as we move out of the ICU and onto the floor, we need to make sure that they have appropriate central line access that's manageable outside of the ICU. This may also be a time when we're titrating off perineural and enteral nutrition and moving into either enteral or oral. And this is also when exercise regimens become very important, and this, again, increases our metabolic needs that must be taken into consideration. Pediatric calorie and protein targets are similar, but just a little bit different. Once again, indirect calorimetry is preferred over the predictive equations. When we are using predictive equations in pediatric patients, we caution with the use of stress factors, as this may lead to overfeeding. Volumetric equations are typically more accurate than predictive equations. So, again, using the ventilator or VCO2 or CO2 measurement to calculate energy needs may be more accurate. At least 80% of estimated needs providing that early in the ICU stay showed a significant improvement in outcomes in patients receiving mechanical ventilation. So, due to the reductions in metabolism, I, again, recommended to avoid full feeding in the early to one-week phase of critical illness for the pediatric patient population. But, however, note that what that means for the pediatric population is a lot different than the adult. So, 54 to 58 calories per kilo per day is what we associate with protein balance and anabolism in the pediatric ICU patient population. So, very high numbers compared to the adults, but, once again, that's because our pediatric patients are still in that growth phase. They're still building and growing, and so they need a lot more support to do that. Now, we've talked a lot about the fact that we are, in most cases, keeping our best guess for how much calories and protein patients need. So, whether that's being provided through perineural nutrition or enteral nutrition or oral nutrition, we need to keep a close eye in the ICU on signs of both under and overfeeding. So, signs of underfeeding may include a loss in lean body mass. It could include difficulty from weaning from the ventilator. I think it's a good time to remind everybody that lean body mass is not just the muscle we see on the outside, but it's also the muscles inside our organs. For example, our diaphragm that works to help us breathe. If we're having difficulty weaning from the ventilator, it could be an indication that we're not getting a patient enough nutrition in order to help sustain that healthy muscle function. We may also see poor wound healing, pressure injury development, infections, and prolonged days on antibiotics can also be an indication of underfeeding. We can't produce those immune factors without having protein and calories and without stimulating the gut in an appropriate way. So, if those things aren't happening, we may have a longer time with infections, prolonged stays on antibiotics. And then lastly, the most common thing and most frequent thing we look for in the ICU is weight changes. But we know that is very often impacted by other things such as, you know, the patient's been on that bed for weeks and weeks and we haven't really gotten them off the bed to calibrate that. They may have SCDs or other equipment on the bed with them now, once again, unable to calibrate and tear zero that weight out to really get a good weight on the patient. So, that's why some of these other signs are a lot more important to monitor and monitor more frequently rather than wait. Now, we mentioned that especially in the early acute and late acute phases that signs of overfeeding, we want to try to avoid these as much as possible. So, these may be some indications that we are providing a patient with too much calorie or protein. First one is hyperglycemia. We mentioned that very, very, very early in the acute phase that metabolic derangements are not influenced by nutrition status. So very often you will see in the acute phase hyperglycemia, this is not related to nutrition provision. Whether you give them nutrition or whether you don't give them nutrition, the patient will be hyperglycemic. And so making adjustments to your nutrition regimen in the acute phase of critical illness in order to impact your glycemic control, probably not the best use of your time. Liver dysfunctions, specifically hepatic steatosis, especially in perinatally fed patients, you can see this happening. Azotemia, fluid overload, increased respiratory rate, or a decreased total volume. Again, looking at that, like are we giving them too much and the patient isn't able to really metabolize things and it creates changes in our metabolism that can result in a need to push out more CO2. Again, CO2 production and work of breathing can all be indicators of overfeeding a patient in the ICU. So now let's talk a little more about feeding complications. We very frequently see patients that don't tolerate enteral nutrition in the ICU. And so in those cases where maybe we are able to start something and we get those non-nutritional benefits of enteral nutrition, when do we start to add and consider supplemental parenteral nutrition? Supplemental PN is not likely to be beneficial until after the recovery phase of critical illness. This is generally recognized as after the first week. Most studies assessing supplemental PN are in well-nourished patients. But again, an emphasis in that first week of critical illness is that we need to avoid overfeeding. Overfeeding causes more problems for critically ill patients early on than underfeeding. So we really, really need to avoid that overfeeding. Adding supplemental PN early on can create an instance where the body's just not ready to utilize those nutrients properly. And it can result in, again, hyperglycemia, hepatic steatosis, azotemia, all of those things that we see actually quite frequently in the ICU could be from overfeeding our patients. We do have a study to help guide this practice. The APANIC study compared early supplemental PN, which was provided within 48 hours, with late supplemental PN, not before day eight. And the early group saw an increase in length of stay. And they also saw an increased percentage of patients that were more than two days on mechanical ventilation. So it delayed extubation, caused a higher length of stay because they were on the ventilator longer. So once again, overfeeding may not be the best for our critically ill patients. And supplemental PN may result in a time where we are, in a situation where we are overfeeding patients. Now supplemental PN for pediatrics, pretty general guideline, not based on a whole lot of evidence, but there is one trial that compared late PN on day eight to early PN for PICU patients. The patients that received late PN did have better outcomes. And the late PN group did not receive as much PN. So once again, those cases where we were avoiding overfeeding showed better outcomes than the cases where we were providing too much nutrition. Now the thing with the pediatric ICU patients, which may also be the case in many adult populations as well is that there really should be a focus on protocolizing and optimizing enteral nutrition delivery. So often the reasons we're not getting adequate EN delivery in the pediatric population is not because they can't tolerate it, but rather it's because of our systems and our protocols around taking them off of enteral nutrition for various tests and procedures or cleaning or all these different reasons that the patient maybe has to leave the ICU. They miss out on some of that nutrition. And so really working with your multi-professional team on finding ways to optimize the delivery of that enteral nutrition can help you really be able to avoid the need for supplemental nutrition and keep that for times when the patient truly can't tolerate the enteral route. So now let's move on to best practices for transitioning, PN to EN and really PN to oral as well. There are no formal guidelines that discuss transitioning from PN to EN, but there are a lot of things that in my opinion should really be considered during this process. First, it's important to establish the patient's ability to take and their potential to tolerate enteral or PO. So not only do we want to have that, like can they actually chew and swallow, but can they stay awake long enough to chew and swallow enough nutrition, right? And will their gut be able to handle that amount of nutrition? And thinking about how long it may take for the gut to reacclimate to getting nutrition through it. So if someone's been on enteral nutrition for a very long time, those tight junctions are deflated. They're probably laying flat. They're not up and ready to take on nutrition. So it may take several days to re-stimulate that GI tract and be ready to absorb nutrients in a meaningful way. Anytime you're adding perennial nutrition to another nutrition regimen, as we talk about, it is important to avoid overfeeding and avoiding hyperglycemia. So in many cases, too, we have to think about and consider the insulin regimen for our patients. So often we add insulin to our perennial nutrition bag. And so when we're transitioning patients to the PO or the enteral route, we need to take that into consideration and transition the appropriate administration of that as well. Underfeeding really is less of a concern as most often when we're transitioning patients, this transition only takes one to three days. So it's better to err on the side of less nutrition and avoid that overfeeding than it is to overfeed someone and then create other complications that we then have to deal with. A common practice for perennial nutrition is we hear people say, oh, cut it in half and we'll discontinue it. But it's important to think about what does this really mean? Are you saying that we're gonna cut the volume in half? Do you want us to cut the calories in half? So I think a better approach to trying to transition someone from PN to something else is to let your nutrition support team or let your dietician or pharmacist manage that. And by just letting them know that you're ready to transition, you're ready to wean them off the PN and onto whatever else they're being provided. Another thing we have to think about when we're taking patients off of perennial nutrition is we need to avoid rebound hypoglycemia. And we do that through a gradual taper of that perennial nutrition over to a final discontinuation. Generally, most places will also have the nurse check a POC blood sugar at least 30 minutes and then again, maybe two hours after stopping that PN. And then lastly, patients that have been on PN have been provided a lot of volume in many cases. Many cases, two liters, maybe above two liters of volume a day. So when we take that out or we start to reduce that, we need to make sure that they can adequately meet their fluid needs as well. And so in some cases, patients may need additional IV fluid support for the short term before they can really start to make sure that they can take in adequate fluid. What about micronutrients? So micronutrients is a question that the dietician and I get often. How and what should we be giving our patients in the ICU? Now, we've already talked a little bit about refeeding syndrome. Again, just as a reminder, patients at a high risk for refeeding syndrome should have their potassium and phosphorus checked and IV thiamine before starting nutrition support. IV thiamine is relatively safe to provide patients. We don't really check for levels of that. We're not gonna wait for that level to come back if we need it. We're just gonna give that IV thiamine and go ahead and start to feed that patient, especially in those cases of high risk for refeeding. Malnutrition and severe malnutrition is another situation in which we may add supplemental micronutrients. Anybody that has had a poor PO intake prior to coming in the hospital may be deficient and they may require some repletion. I think routinely checking every ICU patient for all micronutrients is probably not a best practice. But in the case of a severely malnourished patient, it may be worthwhile. It also may be worthwhile just going ahead and starting some micronutrient supplementation. Again, relatively low harm risk in doing that. Another situation in which micronutrients become very important is during renal replacement, especially CRRT. So CRRT pulls a lot of things out of the blood, which can be good, but it also pulls with it things like our vitamins, especially B vitamins, and vitamin C, copper, selenium, and protein. So CRRT pulls a lot of these things out of the blood. We need to replace it. So replacing it with good nutrition, high in protein, as well as a good B vitamin, a vitamin C, a copper, and a selenium are definitely a best practice. If you have a patient on CRRT for long periods of time, it may be good to check those levels. Lastly, I will touch on selenium since it's something that comes up frequently. We have some studies that indicate that there may be a reduction in mortality with the use of selenium in the ICU, as well as a reduction in acute renal failure. However, there's not a whole lot of strong evidence to support the routine use of selenium in the ICU. We did think maybe for a while there might be some benefits of selenium in the cardiac ICU, but it seems like, again, that may not be the case. Selenium, along with things like arginine, glutamine, these may be nutrients and micronutrients that really have more of an effect when they are combined with other nutrition. So in the world of nutrition, a lot of times we like to try to cherry pick and pull out individual things and say that this one thing is what's gonna make the biggest impact. We've done that with things like vitamin D, like vitamin C in the past, and what we're really finding is that nutrition is a little more complicated than that, and it's really about the whole picture. So providing all of these things in conjunction with each other can really help, it's what's really gonna help improve outcomes for our patients. So key takeaways from today's presentation. First of all, timing of nutrition support. Traditionally, again, we've only talked about nutrition support in terms of before one week and after one week. And so now we're really starting to pay more attention to those phases of acute illness, and really trying to identify when those phases start and stop, and that is going to help guide our provision of nutrition support in the ICU. In the future, I think we'll be seeing more data around certain biomarkers, and maybe there's labs we'll be able to check, or maybe there are other indications that will be a clear delineation of the changes between one phase to the next, and I think that's really gonna be where we can start to tailor nutrition support in the ICU to the individual even more so. So we'll be on the lookout for a lot of that in the coming years. But in the meantime, once again, timing of nutrition support is a complicated practice, and we need to be making decisions with our multi-professional discussions, and it's based on a number of data points. So it's not just one person making one decision. It's not just a protocol where you start and continue to titrate up. It really needs to be individualized and tailored in order to help really make an impact on improving outcomes for our patients. Energy and protein goals. Remember, indirect calorimetry is the gold standard, but even with indirect calorimetry, it's a moving target. Energy is a moving target. We saw very frequently with COVID, for example, patients that came into the ICU, according to indirect calorimetry measurements were very, very, very low metabolic demand. As they went throughout their stay, by week two, many of these patients were 200% their resting energy expenditure. So a lot of very big changes that can happen, and they can happen very quickly in terms of your metabolic demand. So patients can become malnourished very fast, or they can become overfed very fast. So again, energy is a moving target. If you're using indirect calorimetry, you still need to be developing systems and processes for checking and rechecking that throughout a hospitalization. But if you're using predictive equations or a weight-based approach, once again, you still need to have, there's an emphasis on monitoring, and monitoring for those signs of over and underfeeding in order to help prevent complications in the ICU. So avoiding that hyperglycemia, but also avoiding the utilization of lean body mass for energy. And we talked about those signs of over and underfeeding and how we should be continually monitoring those. Once again, it's a multi-professional approach. Everyone should be having the conversation every day around whether the patient is meeting those needs. And lastly, we talked a little about micronutrients. We do think that this could be helpful in some situations. We don't have a whole lot of strong evidence. We know, for example, refeeding is needed, diamond is needed. We do know in CRRT, there may be many cases where we need some additional supplemental micronutrient provision. But in other ways, the jury's still out. I think this is gonna be another one of those things we'll see more of in the future if we can find ways to identify these biomarkers to determine where the patient is in the phase of critical illness. We'll be able to measure serum levels of micronutrients in a more meaningful way. Right now, many of our micronutrients are acute phase responders. So if we're ordering a micronutrient level, it may not actually be low or it may not actually be normal, even if the serum level indicates low or normal. We really just don't know because when inflammation is present, it makes a lot of these levels change. And so not only do we not know if the measure is accurate, but we also don't know whether providing and supplementing that nutrient really makes a big impact in its own setting. Really, the important emphasis for now should be on creating a holistic approach to nutrition, providing the RDAs, recommended daily allowances of our nutrients each day at minimum, and supplementing as needed. So that is my presentation. Thank you so much for joining us. Infusing life into the ICU is such an important practice and I encourage everyone to really create a multidisciplinary approach around caring for your critically ill patients, especially as it comes to nutrition. Thank you.

Ashley DePriest

Assistant Director

Clinical Nutrition

Emory University Hospital

ICU nutrition

Parenteral nutrition

Enteral nutrition

Critical illness phases