CONTENTS
- Rapid Reference: Creating a tube feeding prescription 🚀
- General
- Macronutrient needs
- Enteral nutrition: getting started
- Troubleshooting enteral nutrition
- Total parenteral nutrition (TPN)
- Podcast
- Questions & discussion
- Pitfalls
the following parameters are needed:
- Height & weight.
- Propofol dose.
- Tube feed choice: 📖
- The basic tube feeding formulation is usually fine (e.g., Promote™️).
- Intermittent hemodialysis: renal tube feeding formulation.
- Energy target (kCal/kg): 📖
- ICU days 1-2: ~12.5 kCal/kg.
- ICU days 3-7: ~18 kCal/kg.
- ICU days >7: 25 kCal/kg.
- Protein requirement: 1.2 g/kg. 📖
- Size of supplemental protein packets (e.g., 15 grams/packet).
- (Reminder: Consider the risk of refeeding syndrome whenever starting nutrition: 📖)
to create a low-carbohydrate tube feeding regimen:
- Carbohydrate intake may be reduced by the addition of MCT oil modules:
- 1 module = 15 ml of MCT oil = 116 kCal.
- Using the ClinCalc calculator, increase the propofol rate by a value equal to (732/weight)(# modules). This will account for the fat calories in the MCT oil, allowing you to calculate a tube feed formulation that provides the proper amount of calories and protein.
nutritional phases in acute illness
- (1) Acute phase, early period
- Immediately following a severe injury, the body enters a catabolic state.
- Catabolism will occur whether or not exogenous nutrition is provided.
- If full nutritional support is provided during this phase (i.e., sufficient nutrition to meet the patient's caloric utilization), then the combination of exogenous nutrition plus energy generated from catabolism will cause overfeeding. Therefore, full nutritional support should generally not be provided during this phase.
- Guidelines recommend starting enteral nutrition during this phase if possible. However, only up to 50% of the patient's estimated caloric utilization should be provided at this point.
- In the acute phase of illness, excessive provision of nutrition could be particularly detrimental due to suppression of autophagy (a physiologic response to fasting that promotes regeneration of cellular components).
- (2) Acute phase, late period
- This is a transitional period.
- Ideally, recovery will begin, with waning of catabolism.
- Nutritional administration can be ramped up during this period.
- (3) Late phase
- Ideally, patients will transition into an anabolic state, with regeneration of lost muscle tissue. However, some patients may remain in a state of persistent catabolism (e.g., if the original insult cannot be resolved).
- Full nutritional support should generally be provided at this point (e.g., sufficient calories to balance out all caloric expenditures).
pitfalls in nutritional assessment
- The classic pitfall in nutritional assessment is failure to differentiate between the effects of an acute disease process (e.g., shifts in albumin levels due to septic shock) versus underlying malnutrition.
- Laboratory indices of nutrition generally fail and are not useful (e.g., albumin and prealbumin).
- Scoring systems (e.g., the NUTRIC score) fail to differentiate between malnutrition and acute illness, rendering them clinically unhelpful. The NUTRIC score is actually just a bizarre hybrid of the APACHE and SOFA scores, with no direct measurement of nutritional variables.
so how should be assess nutritional risk?
- Clinical judgement is required.
- Factors to consider include the following:
- Adequacy of oral intake (e.g., has the patient been NPO for several days, or had restricted access to food?).
- BMI (body mass index).
- Recent weight loss.
- Physical signs of cachexia (e.g., temporal wasting).
how should we approach at-risk patients?
- This is tricky. At first, it might seem that nutritionally depleted patients should receive more aggressive nutritional support. However, at-risk patients are also at greater risk of refeeding syndrome 📖 – which would suggest that we should be more conservative with their initial nutritional support.
- Overall the same general considerations and nutritional goals apply to these patients, when compared to other patients. Some differences might include:
- Greater attention to initial electrolyte levels, to monitor for the emergence of refeeding syndrome.
- Greater attention to ensure that patients are reaching nutritional targets.
predictive equations to determine caloric requirement
- Numerous equations are available to estimate caloric requirements. None of them work very well.
- The most common approach is to estimate caloric requirements as 25 kCal/kg/day.
- Unfortunately, estimation of nutritional needs is often inaccurate (potentially leading to underfeeding or overfeeding).
direct measurement of metabolic rate
- Measurement of the metabolic rate can provide a more accurate approach to personalizing nutritional prescriptions. However, studies have not yet shown that tailoring nutritional prescriptions based on individual energy expenditure improves hard ICU endpoints.(32019607)
- Nonetheless, measurement of the patient's metabolic rate is sensible, especially in situations where predictive equations can be far off the mark:
- Extremes of weight (profound cachexia or super-morbid obesity).
- Pregnancy.
- Hypermetabolic states (e.g., severe burns or thyroid storm).
- Multiple amputations.
- The most accurate approach is indirect calorimetry, which directly measures both CO2 generation and O2 consumption. This is recommended by recent ESPEN guidelines.(30348463) Unfortunately, this requires an expensive gadget (a “metabolic cart”) which is available in only 2% of ICUs.(30741491)
- Volumetric capnography is a simpler approach that is immediately available on many newer ventilators. This approach requires estimating the respiratory quotient (RQ) to be 0.85, but the amount of error introduced by this approximation is acceptable. The daily caloric requirement is estimated as the VCO2 in ml/min multiplied by 8.2 (figure below)(32019607; 30348463)
hypocaloric feeding when starting nutrition
- Current guidelines recommend gradually escalating the amount of calories provided. The following strategy may be reasonable: (32019607, 30348463)
- Acute early phase (ICU days 1-2) – Target ~25-50% of usual caloric goals (e.g., ~12.5 kCal/kg).
- Acute late phase (ICU days 3-7) – Target ~50-70% of estimated energy targets (e.g., ~17.5 kCal/kg) or 80-100% of measured energy requirements.
- Recovery phase (ICU day >7) – Target the estimated (25 kCal/kg) or measured energy requirement.
- Among patients with refeeding syndrome, an even more gradual escalation of nutritional intake may be appropriate. 📖
- Regardless of whether hypocaloric or full caloric feeds are provided, the full protein requirement should be provided (e.g., 1.2 g/kg/day).
- Protein is often regarded as the most important macronutrient for promoting immune function and maintaining lean body mass.(33002971)
- The EFFORT multicenter RCT demonstrated that a protein target of 1.2 grams/kg/day yielded equivalent or superior results compared to 2.2 grams/kg/day (among the subgroup of patients with acute kidney injury, there was a signal of possible increased mortality when provided 2.2 grams/kg/day).
- 1.2 grams/kg/day is a reasonable protein prescription.(30348463)
remaining calories: division between carbohydrate vs. fat
- The sections above discussed the total amount of energy administration (often 25 kCal/kg/day) and protein administration (often 1.2 g/kg/day). This leads us to the question of how the remaining calories should be divided up between fat and carbohydrate administration.
carbohydrate targets
- Providing at least ~600 kCal/day carbohydrate (~150 grams) will prevent starvation ketoacidosis. Ketoacidosis isn't necessarily dangerous (for example, it is a component of ketogenic diets). However, ketoacidosis may lead to some confusing electrolyte and pH shifts, which could be undesirable.
- Excess carbohydrate administration may promote hyperglycemia, with increased insulin requirements. This may lead to a downstream risk of hypoglycemia if the tube feed is stopped or interrupted (while the patient is still exposed to exogenous insulin).
- Reducing the amount of administered carbohydrate decreases hyperglycemia and glucose variability across several clinical trials.(32004195, 33734480)
- For patients with problematic hyperglycemia (e.g., brittle type-II diabetes), providing only ~33% of the calories in the form of carbohydrate may be reasonable to avoid excessive glucose variability.(33734480, 26549276)
how to decrease carbohydrate administration
- This depends on locally available resources, with possibilities including the following:
- (1) Switch to a different tube feeding formulation:
- The carbohydrate content of various formulations varies significantly (figure below).
- Some tube feeding formulations are specifically designed to be low-carbohydrate/high-fat (LCHF). However, availability of these formulations varies between hospitals.
- (2) Addition of supplemental fat calories (e.g., medium chain triglyceride oil, aka MCT oil).
- Additional fat administration allows for precise adjustment of the amount of carbohydrate provided. This strategy has the advantage of being compatible with any tube feeding formulation (e.g., it may be used for patients with renal failure who are receiving a renal tube feeding formulation).
- MCT oil provides supplemental fat calories. 15 ml of MCT oil (one tablespoon) contains 116 calories. Adding 6-8 tablespoons of MCT oil per day provides 700-900 additional fat calories.
- MCT oil may be more easily absorbed than other forms of oil, thereby limiting gastrointestinal side effects, such as diarrhea.
- (Formulating a tube feeding prescription with modular fat is discussed above: 📖).
⚠️ Beware of your cognitive biases. Obese patients are rarely viewed as malnourished by clinicians, but frequently suffer from protein calorie malnutrition and muscle wasting.(30741491)
general concepts
- It might be tempting to consider providing fewer calories to obese patients, with a goal towards weight loss. However, there is no high-quality evidence that this is safe within the context of critical illness.
- Unfortunately, providing inadequate nutrition causes predominantly loss of muscle mass. Obese patients metabolize lean mass at unusually high rates, creating an increased risk of losing lean body tissue.(30741491) Undernutrition thus leads to a very regrettable situation where the patient retains adipose tissue and remains overweight – but now also has superimposed protein-calorie malnutrition with muscle wasting.
- Pending the availability of better data, obese patients should be nutrified based on the same general principles as other patients. The goal of nutrition is not to promote weight loss, but rather to avoid catabolism.
nuts and bolts
Adjusted weight = IBW + (1/3)[Actual wt – IBW]
- The ESPEN guidelines provide a simple approach for nutrition in obesity (BMI >30)(30348463):
- Use the adjusted body weight rather than the actual weight. The adjusted body weight is equal to the ideal body weight plus one-third of the difference between the actual weight and the ideal body weight.
- Caloric needs can be estimated as (25 kCal/kg)(Adjusted weight).
- Protein needs can be estimated as (1.2 grams/kg)(Adjusted weight).
- In severe obesity, measuring the patient's caloric expenditure directly can be helpful (e.g., based on VCO2 measurement). 📖
start enteral nutrition early
- Early enteral nutrition (<24-48 hours after intubation) has consistently been shown to improve outcomes. Benefits include prevention of ileus, maintenance of gut integrity, avoidance of pneumonia, and stress ulcer prophylaxis. Initiation of nutrition within <48 hours is recommended by all clinical guidelines.(32019607, 34906215)
- Nearly all intubated patients should be fed.
the following are not contraindications to enteral nutrition
- Lack of bowel sounds.
- Therapeutic paralysis (the gut is composed of smooth muscle, which doesn't respond to paralytics).(33395086)
- Patient unable to lie in a semirecumbent position.
- Prone positioning.
- Pancreatitis.
- Open abdomen.
- Recent gastrointestinal or abdominal aortic surgery. (30348463)
- Low to moderate dose vasopressors.
contraindications to enteral nutrition
- (1) Gastrointestinal catastrophe:
- Obstruction.
- Severe ileus. (more on this here)
- Perforation.
- Mesenteric ischemia.
- Active, severe gastrointestinal bleeding.
- Abdominal compartment syndrome.
- High output fistula (with inability to access the gut beyond the fistula).
- (2) High doses of vasopressors:
- Numerous studies demonstrate that patients on low to moderate dose vasopressors can be fed enterally.(31826259) Enteral nutrition was associated with reduced mortality in patients receiving <0.3 ug/kg/min norepinephrine in one study.(33395086)
- The best data might come from the NUTRIREA-2 trial, which randomized 2,410 extremely ill patients (median vasopressor requirement of 0.5 ug/kg/min norepinephrine) to receive parenteral nutrition or full enteral nutrition (20-25 kCal/kg/day). There was a statistically significant increase in bowel ischemia among patients receiving enteral nutrition, but the absolute risk was only 1%. This study shows that enteral nutrition can cause mesenteric ischemia – but this occurs only very rarely and at the extremes of risk (patients on massive doses of vasopressor who are receiving full feeding).(29128300)
- Overall, the vast majority of patients on vasopressors who have been adequately resuscitated can be started on enteral nutrition, especially if feeding is initiated at a relatively low rate. However, enteral nutrition is contraindicated among patients with refractory shock or patients on high doses of vasopressors (e.g., greater than ~0.3-0.5 mcg/kg/min norepinephrine).
Salem sump tube
- This is a larger and stiffer tube which contains two lumens. One larger lumen may be used to infuse material, or to apply suction. A smaller lumen is open to the atmosphere, which prevents the tube from exerting too much traction on the gut mucosa.
- Salem sump tubes are typically inserted immediately following intubation. They are useful in sicker patients, who might need both infusion of material and suctioning of the gut.
- Among intubated patients, sump tubes are preferentially inserted via the mouth (i.e., an orogastric tube). Placement via the mouth may reduce the incidence of sinusitis and ventilator-associated pneumonia. Intubated patients already have an endotracheal tube in the back of their throats, so adding a small sump tube won't affect comfort substantially. When a patient with an orogastric tube is extubated, both the endotracheal tube and the orogastric tube are removed.
small bore feeding tube
- This is a smaller-bore, single-lumen tube. The tube is more flexible and comfortable. Unfortunately, this flexibility and small diameter makes it impossible to use the tube to suction enteric contents.
- Uses of small-bore feeding tubes:
- (1) Small-bore feeding tubes are more comfortable for patients who are not intubated. A nasoenteric small bore feeding tube can remain in place for weeks, allowing time for the patient to regain swallowing ability.
- (2) A small-bore nasal post-pyloric feeding tube can be placed at the bedside using electromagnetic guidance (CorTrak system). This can be useful in patients with gastroparesis, allowing nutritional delivery to bypass the stomach.
- Small-bore feeding tubes are generally inserted via the nose (even among intubated patients). When the patient is extubated, the nasal feeding tube may remain in place. This can be especially helpful for patients who are expected to remain delirious or unable to swallow following extubation (e.g., patients with hepatic encephalopathy or stroke).
gastric versus post-pyloric feeding tube placement
- For most patients, there is no significant difference between gastric or post-pyloric tube placement.
- Some medications may be better absorbed if administered within the stomach (e.g., amiodarone).
- Gastric tube placement is usually used initially, since this is easier and faster to perform.
- Post-pyloric tube placement may be useful in patients who encounter difficulty with gastric feeding (e.g., gastroparesis).
usually little benefit from disease-specific formulations
- The vast majority of patients can be adequately fed with a generic tube feed formulation (to which modular protein is added, as needed, to meet protein calorie requirements).
- 🛑 Arginine-supplemented formulations (e.g., Crucial™️, Impact™️) might be useful for some trauma or postoperative patients, but they tend to increase mortality among patients with severe sepsis.
- Some situations where disease-specific formulas may be helpful:
- (1) A renal tube feed formula should be used for patients with severe kidney failure (e.g., patients on intermittent hemodialysis, patients with volume overload, or patients with hyperkalemia or hyperphosphatemia).
- (2) Low-carbohydrate/high-fat formulations formulations may reduce hyperglycemia and glycemic variation (discussed further above: 📖).
what is the ideal of tube feeding formulations for most patients?
- Optimal characteristics of a tube feed formulation might be:
- Relatively low in carbohydrate and higher in protein (to avoid hyperglycemia and promote adequate protein administration – noting that hyperglycemia is extremely common in the ICU).
- Containing high-quality fats rich in omega-3 fatty acids (e.g., fats derived from fish oil, rather than canola oil).
- Containing proteins derived from whey, which may promote muscle synthesis more effectively than protein from casein.(21367943)
- One formulation which meets these criteria is Peptamen AF. However, it's unclear whether this formulation causes measurable benefits for most patients.
rationale for continuous feeding
- Continuous feeding requires less work from a nursing perspective (the infusion pump can be set and left alone).
- Continuous feeding might be associated with a lower rate of diarrhea.
- The main rationale for continuous feeding is that this is the most commonly employed technique, so that people are familiar with it.
rationale for intermittent feeding
- (1) Intermittent periods of fasting may improve insulin sensitivity, thereby reducing insulin requirements.(33538425)
- (2) Intermittent feeding may improve muscle synthesis (which is triggered by pulsatile release of insulin and amino acids following meals).(31826259)
- (3) Intermittent feeding improves the ability to reach daily nutritional targets because, even if the patient is NPO for part of the day, then full feeding is easy to achieve (by rescheduling the administration of meals).
- (4) Continuous feeding is aphysiologic, potentially leading to impaired resistance to stress, reduced autophagy, disarray of gastrointestinal hormones, abnormal intestinal motility, and increased inflammation. Alternatively, intermittent feeding may allow preservation of circadian rhythms and normal nutritional physiology.(32487846) An understanding of the physiology of intermittent fasting implies that bolus feeding should be superior to continuous feeding – since continuous feeding provides zero time within a fasting state! (31881139)
nuts & bolts of intermittent feeding
- Determine the total volume of tube feeding required and divide it into meals of ~240-720 ml (typically ~4-6 meals).(29924423) It might be ideal to space meals out during daylight hours, in order to promote a normal circadian rhythm.
- Meals may be administered using gravity infusion or an infusion pump. Modern infusion pumps can be programmed to perform intermittent feeding autonomously, thereby reducing the nursing workload.
bolus feeding
- Technically, the term “bolus feeding” might be best reserved for rapid administration of nutrition into the stomach (e.g., manually via syringe). However, the term “bolus feeding” is also sometimes used more widely, to refer to intermittent infusion of nutrition over periods of 30-60 minutes as well.
- While very rapid bolus feeding into the stomach may be tolerated, this may not be safe for post pyloric feeding.
- There probably isn't a major physiological difference between gastric bolus feeding versus intermittent infusion of nutrition over 30-60 minute periods.
bottom line on intermittent feeding
- Currently this is an area of equipoise, with ongoing clinical research. To date, studies comparing continuous versus intermittent feeding have not found major differences between these two strategies. One explanation for these neutral trials is that studies of intermittent feeding have spaced feeding around the clock (rather than allowing a 12-hour fasting period).(33538425)
- Continuous or intermittent feeding are both generally safe and effective.
- In most units, continuous feeding will likely remain the default strategy. Switching to intermittent feeding may be a rational approach for patients who have escalating insulin requirements.
avoid interruptions
- Avoid interrupting tube feeding for possible extubation
- If the patient has a sump tube, then feeding shouldn't be stopped until a definite decision has been reached to extubate the patient. Prior to extubation, the tube may be placed to suction.
- If the patient has a small-bore feeding tube, then the feeding tube cannot be placed to suction. Most of the time, these tubes are placed in the small intestine – so the risk of emesis is low. For patients with a post-pyloric feeding tube, feeding probably doesn't need to be held prior to potential extubation.
- In the unusual situation that a patient has a small-bore feeding tube placed in the stomach, then it might be reasonable to hold feedings for a few hours prior to extubation.
- Avoid interruptions for procedures
- Many hospitals have a culture of making patients “NPO post midnight” for any procedure (e.g., minor interventional radiology procedures). Such interruptions are generally unnecessary and should be avoided whenever possible. However, this needs to be negotiated with the service performing the procedure.
- Don't routinely check gastric residual volumes (GRV)
- The most recent ASPEN guidelines recommend not checking the gastric residual volume.(26773077)
- Tube feeds shouldn't be held based on high gastric residual volumes unless there is additional evidence of feeding intolerance (e.g., distension, nausea, vomiting).
- The best approach to gastric residual volumes is to stop checking them routinely. However, if there is clinical vomiting or distention, then residual volume may be useful to diagnose gastroparesis.
- Not measuring the gastric residual volume may increase the number of episodes of emesis, but this doesn't affect the risk of clinical pneumonia. Pneumonia seems to generally result from aspiration of oropharyngeal secretions, rather than gastric contents. Thus, emesis may be more of a nuisance than a life-threat.
mitigating interruptions: volume-based feeding protocols
- One strategy for prescribing tube feeding is to define a daily target volume of nutrition. If nutrition is held for several hours, then the target volume should be administered over the remaining duration. Thus, limited interruptions in feeding will not prevent the patient from reaching their nutritional targets.
- Several studies have shown that volume-based feeding protocols allow patients to reach nutritional goals more reliably.(30741491)
evaluation
- If there is distention/tenderness, obtain an abdominal X-ray to exclude obstruction or ileus.
- Obtain a gastric residual volume if possible.
management
- (1) If there is no evidence of ileus, then the patient likely has critical illness gastroparesis – treatment is described here: 📖
- (2) If there is evidence of ileus, this should be treated as described here: 📖
common causes of diarrhea in the ICU
- C. difficile is a leading cause of ICU-acquired diarrhea.
- Medications
- Overaggressive bowel regimens.
- Liquid drug preparations designed for enteral administration (elixirs and syrups) are a common cause of diarrhea. These are commonly hyperosmolar and often contain sorbitol – two factors which promote diarrhea.
- Antibiotic-associated diarrhea (noninfectious) may result from disruption of bowel flora.
- Magnesium-containing oral medications.
- Intestinal atrophy (after interruption of feeding, it may take the gut a while to start functioning fully).
evaluation
- Exclude C. difficile:
- This is generally the first consideration for an ICU patient with new-onset diarrhea.
- Rapid identification of patients with C. difficile may facilitate treatment and also allow enhanced contact isolation that protects other patients.
- Review the medication list for elixirs and syrups, bowel medications, and oral magnesium.
- Additional tests (e.g., stool bacterial culture) are rarely helpful among ICU patients with nosocomial diarrhea.
management – 1st line therapies
- 🛑 Tube feeding should NOT be held due to diarrhea!
- Potentially causative medications should be discontinued, if possible.
- Fermentable soluble fiber may be helpful (2.5-5 grams q6hr). Common examples of this include guar gum or banana flakes 🍌.
management – 2nd line therapies
- Formulations which are more concentrated may be more likely to cause diarrhea. If the tube feed regimen is unusually concentrated (e.g., >>~500 mOsm), then switching to a formulation with lower osmolality could help. This may be especially true if the feeding tube is post-pyloric.
- Loperamide may be used, but only after exhaustion of other options and exclusion of C. difficile. Loperamide carries the risk of causing ileus or colonic pseudo-obstruction, which are potentially more dangerous than diarrhea.
indications
- Total parenteral nutrition (TPN) is predominantly used in the surgical ICU, where patients often have an absolute contraindication to enteral nutrition (e.g., abdominal compartment syndrome, bowel obstruction). The vast majority of medical, neurologic, and cardiac patients can be managed with enteral nutrition. Enteral nutrition is generally preferred due to reduced risks of nosocomial complications, especially infection.
- Indications:
- (1) Enteral nutrition is truly contraindicated (see contraindications above; there aren't many).
- (2) Enteral nutrition has failed despite all efforts (e.g., including a post-pyloric feeding tube to bypass gastroparesis).
- Timing
- In general, early TPN should be avoided. TPN is generally started if enteral nutrition isn't possible for ~7-10 days.
- If the patient is already malnourished and enteral nutrition isn't anticipated to be feasible in the near future, earlier TPN may be considered.
risks/complications
- Line infection.
- Volume overload (TPN often involves 1.5-2 liters/day infusion).
- Metabolic:
- Refeeding syndrome.
- Hyperglycemia or hypoglycemia.
- Hypertriglyceridemia.
- Cholestasis; hepatomegaly.
- Hyperammonemia.
- Electrolyte abnormalities.
- Acalculous cholecystitis, intestinal atrophy.
monitoring & avoiding complications
- Glucose monitoring is required, since the continuous and aggressive provision of carbohydrates can easily lead to hyperglycemia.
- Electrolytes (including Ca/Mg/Phos) may be followed daily until stable.
- Acid-base abnormalities may often be caused or ameliorated by adjustment of TPN formulation (e.g., inclusion of sodium chloride versus sodium acetate).
- Refeeding syndrome should be carefully monitored for initially (e.g., with frequent measurement of electrolyte and phosphate levels), since patients who receive TPN have often been without nutrition for prolonged periods of time.(more on refeeding syndrome here)
- Fluid balance should be monitored carefully.
- TPN provides 1-2 liters of fluid daily. Among critically ill patients on additional medications and infusions, this may lead to a total fluid input of several liters.
- Diuretics should be used aggressively, as needed to establish a net even fluid balance.(more on diuresis here)
- Liver function tests should be followed weekly (since TPN may promote cholestasis).
- Triglyceride levels should be measured periodically (e.g., every two weeks initially, or every two days among patients on propofol infusions). If triglycerides rise above 400-500 mg/dL, the amount of lipid provided in TPN should be reduced. If triglyceride levels rise above 1,000 mg/dL, TPN should be held.
- Fever curve should be followed, with a low threshold to obtain blood cultures to evaluate for line infection.
tips
- Intravenous lipid currently used in the United States contains omega-6 fatty acids, which promote inflammation.(33002971) It may be beneficial to avoid the administration of lipid during the first week of TPN therapy.
- Patients on TPN should be re-evaluated daily for the ability to transition to enteral nutrition.
- An online calculator may help calculate TPN prescriptions.
- A detailed approach to the formulation of TPN is beyond the scope of this chapter. Nutritionists will generally be involved with this.
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To keep this page small and fast, questions & discussion about this post can be found on another page here.
- Nobody knows exactly when or how much to feed our patients, but there is agreement that early enteral nutrition is a good thing (within <48 hours of ICU admission).
- Never delay initiation of nutrition while waiting for a nutrition consult the next day. The calculator above shows how to quickly determine an initial tube feeding regimen.
- The gastric residual volume should not be checked routinely.
- Follow electrolytes (including Mg and Phos), especially when initiating nutrition. If the phosphate starts falling, consider refeeding syndrome.
- If your patient on enteral nutrition is developing refractory hyperglycemia, consider changing the enteral nutrition formulation before resorting to large doses of insulin.
Guide to emoji hyperlinks
- = Link to online calculator.
- = Link to Medscape monograph about a drug.
- = Link to IBCC section about a drug.
- = Link to IBCC section covering that topic.
- = Link to FOAMed site with related information.
- = Link to supplemental media.
Online calculators
Guidelines
- European Society of Parenteral and Enteral Nutrition (ESPEN) 2019 guidelines – Overall best & most updated guidelines (Singer et al.)
- American Society of Parenteral and Enteral Nutrition (ASPEN) 2016 guidelines (McClave et al.)
- Updated reviews of available data: CriticalCareNutrition.com.
Review of seminal studies by The Bottom Line
- EFFORT protein (2023) – Provision of 1.2 g/kg/day protein was equivalent or superior to higher doses of protein.
- TARGET trial (2018) – Use of energy-dense formula (1.5 kCal/ml) provided more calories, without affecting endpoints.
- EAT-ICU (2017) – Early goal-directed nutrition did not improve outcomes in a single-center study.
- The Refeeding Syndrome Trial (2016) – Among patients with refeeding syndrome (defined as hypophosphatemia provoked by feeding), restricted and gradual escalation of caloric provision improved outcomes.
- Ferrie et al. (2016) – Among patients on parenteral nutrition, provision of higher amounts of protein caused some small but measurable clinical benefits.
- PERMIT trial (2015) – Safe to provide ~50% caloric intake with 100% of protein requirement, for the first two weeks.
- PYTHON trial (2015) – Early nasoenteric feeding in patients with predominantly mild-moderate pancreatitis didn't affect outcomes.
- EPaNIC trial (2011) – Early parenteral nutrition (within the first week of critical illness) caused harm.
- TICACOS (2011) – Titrating nutrition based on resting energy expenditure (REE) may be associated with lower mortality.
- EFFORT (2023) – Higher versus lower protein prescription.
References
- 26773077 McClave SA, Taylor BE, Martindale RG, et al. Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). JPEN J Parenter Enteral Nutr. 2016 Feb;40(2):159-211. doi: 10.1177/0148607115621863 [PubMed]
- 29128300 Reignier J, Boisramé-Helms J, Brisard L, et al.; NUTRIREA-2 Trial Investigators; Clinical Research in Intensive Care and Sepsis (CRICS) group. Enteral versus parenteral early nutrition in ventilated adults with shock: a randomised, controlled, multicentre, open-label, parallel-group study (NUTRIREA-2). Lancet. 2018 Jan 13;391(10116):133-143. doi: 10.1016/S0140-6736(17)32146-3 [PubMed]
- 29924423 Ichimaru S. Methods of Enteral Nutrition Administration in Critically Ill Patients: Continuous, Cyclic, Intermittent, and Bolus Feeding. Nutr Clin Pract. 2018 Dec;33(6):790-795. doi: 10.1002/ncp.10105 [PubMed]
- 30348463 Singer P, Blaser AR, Berger MM, Alhazzani W, Calder PC, Casaer MP, Hiesmayr M, Mayer K, Montejo JC, Pichard C, Preiser JC, van Zanten ARH, Oczkowski S, Szczeklik W, Bischoff SC. ESPEN guideline on clinical nutrition in the intensive care unit. Clin Nutr. 2019 Feb;38(1):48-79. doi: 10.1016/j.clnu.2018.08.037 [PubMed]
- 30741491 Allen K, Hoffman L. Enteral Nutrition in the Mechanically Ventilated Patient. Nutr Clin Pract. 2019 Aug;34(4):540-557. doi: 10.1002/ncp.10242 [PubMed]
- 31826259 Korwin A, Honiden S. Reconsidering Nutritional Support in Critically Ill Patients. Semin Respir Crit Care Med. 2019 Oct;40(5):580-593. doi: 10.1055/s-0039-1697967 [PubMed]
- 32004195 Reintam Blaser A, Rice TW, Deane AM. Update on nutritional assessment and therapy in critical care. Curr Opin Crit Care. 2020 Apr;26(2):197-204. doi: 10.1097/MCC.0000000000000694 [PubMed]
- 32019607 Lambell KJ, Tatucu-Babet OA, Chapple LA, Gantner D, Ridley EJ. Nutrition therapy in critical illness: a review of the literature for clinicians. Crit Care. 2020 Feb 4;24(1):35. doi: 10.1186/s13054-020-2739-4 [PubMed]
- 32416161 Ridley EJ, Peake SL. Intermittent Enteral Nutrition as a Sole Intervention Has No Impact on Muscle Wasting in Critical Illness. Chest. 2020 Jul;158(1):15-16. doi: 10.1016/j.chest.2020.05.520 [PubMed]
- 32487846 Pletschette Z, Preiser JC. Continuous versus intermittent feeding of the critically ill: have we made progress? Curr Opin Crit Care. 2020 Aug;26(4):341-345. doi: 10.1097/MCC.0000000000000733 [PubMed]
- 33002971 Puzio TJ, Kozar RA. Nutrition in the critically ill surgical patient. Curr Opin Crit Care. 2020 Dec;26(6):622-627. doi: 10.1097/MCC.0000000000000764 [PubMed]
- 33395086 Wischmeyer PE. Overcoming challenges to enteral nutrition delivery in critical care. Curr Opin Crit Care. 2021 Apr 1;27(2):169-176. doi: 10.1097/MCC.0000000000000801 [PubMed]
- 33456876 Chowdhury R, Lobaz S. Nutrition in critical care. BJA Educ. 2019 Mar;19(3):90-95. doi: 10.1016/j.bjae.2018.11.007 [PubMed]
- 33538425 Puthucheary Z, Gunst J. Are periods of feeding and fasting protective during critical illness? Curr Opin Clin Nutr Metab Care. 2021 Mar 1;24(2):183-188. doi: 10.1097/MCO.0000000000000718 [PubMed]
- 33734480 Burslem R, Rigassio Radler D, Parker A, Zelig R. Low-carbohydrate, high-fat enteral formulas for managing glycemic control in patients who are critically ill: A review of the evidence. Nutr Clin Pract. 2022 Feb;37(1):68-80. doi: 10.1002/ncp.10652 [PubMed]
- 34897737 Al-Dorzi HM, Arabi YM. Nutrition support for critically ill patients. JPEN J Parenter Enteral Nutr. 2021 Nov;45(S2):47-59. doi: 10.1002/jpen.2228 [PubMed]
- 34906215 Preiser JC, Arabi YM, Berger MM, Casaer M, McClave S, Montejo-González JC, Peake S, Reintam Blaser A, Van den Berghe G, van Zanten A, Wernerman J, Wischmeyer P. A guide to enteral nutrition in intensive care units: 10 expert tips for the daily practice. Crit Care. 2021 Dec 14;25(1):424. doi: 10.1186/s13054-021-03847-4 [PubMed]
- 36762671 Hermans AJH, Laarhuis BI, Kouw IWK, van Zanten ARH. Current insights in ICU nutrition: tailored nutrition. Curr Opin Crit Care. 2023 Apr 1;29(2):101-107. doi: 10.1097/MCC.0000000000001016 [PubMed]