Clinical Nutrition is a dynamic field which is constantly evolving. As a result, hospitalists are faced with an array of challenges. Several advances in tube feeding (TF) recently have come to practice including devices to assist with blind feeding tube placement (industrial magnets and bedside visualization system CORTRAK®). Newer applications for TF are practiced in patients with acute pancreatitis, intestinal failure and gastrointestinal (GI) fistulas.
Use of parenteral nutrition (PN) declined since it first became available in 1970’s when it was often selected as a first-line therapy. This is largely due to newer information concerning the importance of maintaining gut integrity via enteral nutrition and recognition of the many adverse events associated with PN. Nonetheless, the utility of PN cannot ethically be questioned when it is the last resort. Meanwhile, the permissive underfeeding, immunonutrition (glutamine, arginine and omega-3 fatty acids), probiotics, among other topics, are being researched and conclusive data is not yet available.
Between 30% to 50% of hospitalized patients have some degree of protein-energy malnutrition. There is also abundant evidence that appropriate nutritional support (NS) reduces the length of hospital stay, morbidity and mortality. Daily hospitalist responsibilities include determination of appropriate timing and types of TF or PN, ordering necessary laboratory tests and monitoring for complications.
Provision of TF and PN to a hospitalized patient requires collaboration among physicians, dietitians, nurses and PN pharmacists. Each member of a multi-disciplinary team has specific responsibilities and their activities are associated with different types of errors. Nursing related mistakes are common (inappropriate flushing, wrong PN infusion rate, etc.) but physician and pharmacist miscalculations are the most costly (excessive potassium in infusate, etc.). In many hospitals in the United States, due to its complexity, PN is among top three medications associated with errors.
Legally and ethically, tube and intravenous feedings are considered a medical therapy, and an adult patient or legally authorized surrogate should be informed about the benefits and risks of the intervention, and have the right to accept or refuse the therapy. For patients with advanced dementia, there is no evidence that TF improves quality of life, reduces pressure sores, and/or prolongs survival. NS is not indicated in patients with end stage disease wherein aggressive therapies are discontinued.
II. Identify the Goal Behavior.
Identification of patients at risk
There is no gold standard test to diagnose malnutrition. A clinical method, termed the subjective global assessment (SGA), defines malnourished patients as those who are at increased risk for medical complications. SGA has been validated to accurately predict risk of increased in-hospital mortality, infectious complications and length of stay (LOS). Malnutrition severity by SGA class is directly correlated with the risk of overall inpatient mortality. Generally, a patient with poor oral intake, continuous weight loss, evidence of muscle atrophy, and subcutaneous fat loss is severely malnourished (See Figure 1).
BMI (<18.4 kilograms/meters2 [kg/m2]) can help identify adult patients at increased risk of an adverse outcome. Low serum concentration of albumin is associated with increased incidence of nosocomial infections and in-hospital mortality. However, patients with an acute infection or inflammation, hepatic or renal diseases, may have a low serum albumin due to impaired synthesis, increased degradation, and/or losses regardless of nutritional status. Alterations in hydration may limit interpretation of albumin and prealbumin concentrations in hospitalized patients.
C-reactive protein (CRP) level is useful to assess the presence of an acute phase response: elevated CRP levels would indicate an acute inflammatory response with an expected low albumin/prealbumin levels. In 2009, the Academy of Nutrition and Dietetics and American Society for Parenteral and Enteral Nutrition (AND-ASPEN) agreed upon an etiology-based approach towards malnutrition diagnosis that incorporates a current understanding of the inflammatory response. Rather than relying on laboratory tests, AND-ASPEN have agreed upon the set of clinical characteristics (very similar to SGA) to be used in the detection of malnutrition.
Timing of nutritional support (tube and parenteral feeding) in adults
The results of the clinical trials have not always been consistent and the decision about when to start NS should be based on clinical judgment. Well-nourished adults should be considered for NS if oral intake is inadequate for 7-14 days. A pre-existing malnutrition is probably the most common indication for NS and earlier intervention is necessary. Patients who are malnourished on admission should receive NS within 5-7 days after hospitalization. Studies showed that 22% of the inpatients remain nil per os (NPO) for approximately 5 days.
TF, if not contraindicated, should be given to all intensive care unit (ICU) patients who are not expected to take a full oral diet within 3 days and it should begin during the first 24 hours. Early TF appears to minimize translocation of intestinal bacteria, enhance immunocompetence, blunt the hypermetabolic response to stress and decrease sepsis. Exact timing for initiation of PN in critically ill patients is not clear. For patients in shock, hemodynamic stability should be accomplished prior to initiation of NS.
Tube feeding (TF), also known as enteral nutrition (EN), is favored over PN because it is less invasive, maintains gut integrity, has lower incidence of infectious complications and hyperglycemia, and is more cost-effective. Current evidence suggests that the majority of hospitalized patients can be fed by the enteral route. TF is indicated for the patient with a functional GI tract, and who is unable to meet nutritional needs orally. Unfortunately, during hospitalization only half of the patients receive intended TF volume and 15% reach goal feeds within 3 days.
Common indications for TF:
Inability to take oral diet: oral, laryngeal, esophageal cancer and oropharyngeal dysfunction (cerebrovascular accident [CVA], etc.)
Acute illness with hypermetabolic state: critical illness, including severe trauma, burns, sepsis, and acute respiratory distress syndrome (ARDS).
Unwillingness to take oral diet: psychogenic starvation (anorexia nervosa, etc.)
Bowel obstruction or perforation
Severe secretory diarrhea
Short-term feeding tubes (1-4 weeks) can be placed through the nose or mouth. Some tubes include a guidewire which should never be reinserted while the tube is in the patient to avoid perforation. Tracheal intubation and pneumothorax are rare complications and should be considered in patient whose condition deteriorates following blind positioning of the feeding tube.
Placement of a percutaneous endoscopic gastrostomy (PEG) has now become a common practice in patients requiring TF for more than 4-5 weeks. Patient with morbid obesity or previous upper abdominal surgery may require radiologically or surgically placed gastrostomy. Gastric tubes and ports have large bores to accommodate medication administration.
(See Table I)
|Silicone||Soft and comfortable||Lumen collapses easily, difficult to check residuals|
|Polyurethane||Larger diameterLess clogging||Less comfortable|
|Polyvinyl chloride||Inexpensive||StiffGastric acid makes tube brittleIf used for long time, may cause nasal or gastric erosions|
Checking tube position. Abdominal auscultation is not considered reliable. The standard practice is to obtain an x-ray for blindly placed feeding tubes.
Feeding formula may be administered into the stomach (gastric feeding) or small intestine (post-pyloric feeding).
Gastric feeding is suitable for most patients. It is more physiologic, the stomach has reservoir capacity and is able to tolerate larger volume and the higher osmolality of the formula reduces risk for diarrhea. Buffering properties of formulas are effective for prophylaxis against gastric stress ulcers.
Perception of TF tolerance based on gastric residual volume (GRV) is problematic. Increased GRV may identify “sicker” patients. GRV of 200 milliliters (mL) and 400 mL carries the same risk of aspiration (approximately 22%). Measurement of GRV should not replace clinical judgment in determining patient tolerance of TF. Signs of feeding intolerance may include vomiting, stomach fullness, abdominal distention and diarrhea. Most patients can be started on low volume continuous gastric feeding. Continuous feeding is generally better tolerated than bolus feeds, produces more weight gain and is associated with reduced incidence of aspiration. Stable patients with good intragastric feeding tolerance may be evaluated for transition to bolus feeds.
Post-pyloric feeding is recommended in patients with:
High risk of aspiration (previous aspiration, anatomic abnormalities of GI tract, recumbent position)
Severe gastroesophageal reflux disease (GERD), esophagitis or gastroparesis
Intolerance of gastric feeding
Major intra-abdominal surgery or multiple trauma
Postpyloric feeding should be administered continuously by pump to avoid abdominal cramping, tachycardia, sweating and diarrhea (“dumping effect”) caused by boluses. There is no need to check residuals. Feeding tolerance is monitored by clinical signs.
Disadvantages of post-pyloric feeding:
Difficulty with tube placement (average delay of feeding is 28 hours)
Frequent tube clogging (finer bore than gastric tubes)
There are a variety of commercially available enteral formulas that differ in nutrient composition and cost. Brands and hospital formularies change frequently. Formula selection should be based on patient’s age, underlying diseases, nutrient needs, and tolerance.
Standard formulas are given to the patients with relatively normal digestion and absorption. Fiber-enriched formulas are preferred for long-term tube feeding and in patients with constipation. Elemental and semi-elemental formulas are reserved for patients with compromised GI function (inflammatory bowel disease, short bowel syndrome, etc.). Disease-specific formulas should be used judiciously. For example, diabetic formulas have a high fat content and may not be suitable for patients with severe gastroparesis. Patients who are on TF as a sole nutritional source will require supplemental water/fluids to prevent dehydration. Dietitian consultation is essential for all patients receiving TF.
The patient may aspirate oro-pharyngeal secretions, gastric acids or feeding formula. Oro-pharyngeal aspiration may be a particular concern in patients with neurogenic dysphagia (cerebral palsy, CVA, etc.) or alcoholics and be unrelated to TF.
Methods to decrease aspiration in patients on TF:
Head of bed elevation
Minimize use of sedating agents
Small bowel feeding
Clogged tubes: The best prevention of tube blockage is administration of liquid medications and frequent water flushes. Pancreatic enzymes and sodium bicarbonate mixture can be used for unclogging, however, there is no data that it is more effective than warm water. Avoid use of sodas and juices.
Parenteral Nutrition (PN) is indicated when enteral nutrition is not medically feasible or tolerated. Parenteral feeding provides consistent nutrient delivery and relatively rapid progression to the intended nutritional goal.
PN should not be initiated when:
Treatment anticipated for less than 5 days (except pediatrics)
Patient has no appropriate venous access
Risks of PN are judged to exceed the benefits
PN may be administered via central or peripheral veins. The osmolality of the PN solution dictates whether it may be infused peripherally. Peripheral PN usually requires administration of large fluid volumes and is not suitable for patients who are fluid restricted. It can cause phlebitis and, in the event of extravasation, severe tissue damage can occur.
(See Table II)
|Peripheral PN||Central PN|
|Anticipated duration of PN||5-7 days||As long as indicated|
|Osmolality limits||<900 mosm/L||>900 mosm/L|
|Catheter requirements||Dedicated large bore peripheral IV(except peds)Rotate site every 48-96 hours||Central line with tip at SVCand right atrium junction:PICCIJ, subclavian, Swan-Ganz(not distal port or cordis)Tunneled cathetersPorts|
|Other||Lipids permitted peripherally||Multi-lumen catheter: dedicatedport required for PN|
PN is generally infused continuously over 24 hours. Patients may be transitioned to cyclic PN (off PN for a specified time each day) in preparation for discharge home on PN, or if they are experiencing PN-related liver disease (steatosis and cholestasis).
Composition of PN:
Most components of PN are dosed according to a specific body weight, pre-existing nutritional status, underlying illness and the degree of stress incurred (refer to ASPEN guidelines or calculations adapted by your institution). Glucose infusion rate has to be calculated and should not exceed the upper limit of oxidation for age/weight to prevent lipogenesis and hypercapnia. Renal and hepatic diseases may result in intolerance to protein loads and amino acids dose should be reduced.
There are potential immunosuppressive and proinflammatory effects from currently used omega-6 fatty acid-rich lipid emulsions but data is limited. Fat is the most energy dense macronutrient (9 kilocalorie/gram [kcal/gm] versus approximately 4 kcal/gm for dextrose and amino acids). Use of intravenous (IV) lipids allow for lower dextrose dose and may decrease associated hyperglycemia. Linoleic and linolenic fatty acids are essential to humans and must be provided in sufficient amounts to prevent the fatty acid deficiency. Electrolytes, minerals, trace elements and multivitamin preparation are generally added to PN. Severe vitamin deficiencies can occur in patients receiving PN without vitamin supplementation for as short a time as a few weeks.
(See Table III)
|Prior to PN||CMP, Magnesium, Phosphorus, CalciumTriglyceride|
|Follow-up||BMP, Magnesium, Phosphorus, CalciumPOC glucose q 6 hours or as neededI&O and weightsIndirect calorimetry (rarely), when under- or overfeeding is suspectedLFTs and TriglycerideFatty acid panel, iron studies, carnitine level as needed|
Complications of PN:
Insoluble calcium-phosphorus complexes from improperly compounded solutions have caused diffuse pulmonary emboli.
Mechanical complications of PN are typically related to the catheter (thrombosis, malposition, perforation or leak).
Line sepsis observed in 2-20% of patients on PN and generally related to the catheter care.
Multiple acute and chronic metabolic complications may manifest in patients undergoing PN. Hyperglycemia remains the most common abnormality.
PN can worsen acid-based status of the patient if incorrect salt is selected. Electrolyte abnormalities are common. Since change to the electrolytes of the PN bag occurs only once daily, supplemental doses outside the PN may be needed to correct deficiency.
(See Table IV)
|Hyperglycemia||Insulin therapyAdjust dextrose amount in PN|
|Hypoglycemia||Stop insulin infusionTreat per protocolAdjust dextrose amount in PN|
|Hypokalemia, hypophosphatemia, hypomagnesemia||Monitor for refeeding syndromeReplace separately from PN until levels are stableOptimize content in PN|
|Fluid overload||Concentrate PNConsider diuretics|
|Metabolic acidosis||Increase acetate content|
|Metabolic alkalosis||Increase chloride content|
|Hypercapnia||Indirect calorimetry if overfeeding suspectedDecrease dextrose by increasing lipids in PN|
|Hypertriglyceridemia||Reduce lipid infusionReduce dextrose content in PNIndirect calorimetry if overfeeding suspectedCheck carnitine level and replace if low|
|Metabolic bone disease||Optimize calcium and phosphorusCheck Vit D and PTH levelsDEXA scanBisphosphonatesExercise as able|
|Cholestatic liver disease||EN when possibleUrsodiol orally (improves biochemicalmarkers and pruritus)Reduce calories in PNMay require reductions in Copperand Manganese dosesTransition to cyclic PN|
|Anemia||MVI, folate and B12Oral or IV iron supplementation,blood transfusion|
|Essential fatty acid deficiency||Provide with lipids(minimum 20% 250 mL twice weekly for adults)|
|Aluminum toxicity (peds)||Obtain blood aluminum concentrationand monitor if abnormal|
Possible barriers to sending patient home on PN:insurance approval, lack of local home health services, patient and family ability to understands and perform home PN, and the availability of physician to manage outpatient PN.
Transitioning to oral diet: For patient on continuous TF consider holding feeding for one hour before each meal time and/or change to overnight feeding to stimulate appetite. When patient is meeting 50% of nutrients goal, reduce the volume of TF by half. Once the patient is consistently taking 75% of meals, discontinue TF. There is some evidence that PN has a negative effect on appetite. When patient is consuming at least 500 kcal/day orally, the PN content may be reduced by an equal amount to see if appetite improves. Once the patient is tolerating >60-75% of nutrients orally/TF, PN can be discontinued.
III. Describe a Step-by-Step approach/method to this problem.
Approach To Tube and Parenteral Feeding In Hospitalized Patients
Step 1. Identify patients at nutritional risk (pre-existing malnutrition, prolonged NPO and/or inadequate oral intake, hypermetabolic state) and decide if NS is warranted. In general, malnourished non-critically ill adult with continuously compromised oral intake after hospitalization, should receive NS within 5-7 days or sooner.
Step 2. Estimate anticipated duration of nutritional intervention (days or weeks).
Step 3. Give TF to all patients with functional GI tract if not contraindicated. TF should begin with a trial of gastric TF for most patients. Short term tubes are placed via nasally or orally. For patients with oro-pharyngeal or esophageal obstruction/cancer, consider PEG/radiological or surgical gastrostomy placement on admission. Generally, latter inserted for long-term TF after patient was fed via nasogastric tube for >4-5 weeks.
Post-pyloric feeding reserved for patients with high risk of aspiration (previous aspiration, anatomic abnormalities of GI tract, recumbent position), severe GERD, esophagitis, gastroparesis or intolerance of gastric feeding. Patients with gastric feeding intolerance or known aspiration who is fed via PEG, may benefit from PEG-Jejunostomy or G-Jejunostomy tube insertion. Gastric feeding can be delivered continuously or as boluses. For patients on post-pyloric feeding, continuous administration of formula is advised to avoid “dumping effect”.
Step 4. PN is not recommended unless there are contraindications to TF (bowel ischemia, GI bleeding, bowel obstruction or perforation, etc.) or patient has failed a trial of TF. Peripheral PN can be utilized for a short time. Patients who already have a central line or will require PN for more than 7 days, should receive central PN. Enteral feeding should be encouraged when possible. Even minimal administration of formula has been shown to prevent bacterial translocation, maintain gut integrity and immunity, and promote intestinal adaptation after surgery.
Step 5. Monitor response to TF and PN. Recognize and appropriately manage complications of NS.
IV. Common Pitfalls.
1. After initiation of TF or PN, patients who are critically ill, malnourished, elderly, or alcoholics are at risk for developing a refeeding syndrome. Rapid advancement of nutrients, primarily carbohydrates, increases concentration of circulating insulin which leads to intracellular movement of electrolytes and enhances sodium and water retention. Uptake of phosphorus to make the phosphorylated products of glycolysis also results in hypophosphatemia. Patients may present with lethargy, weakness, cardiac arrhythmia, hypophosphatemia, hypokalemia, hypomagnesemia and worsening edema. Prevention is a key. Correct electrolytes prior to starting NS and thereafter, and advance feeding gradually over several days in patients at risk. Give thiamine IV for 3-5 days and carefully monitor ins/outs and weights.
2. Tolerance of TF should be assessed primarily by clinical signs. When gastric residual volumes are taken into the account, follow trends, not one high level.
3. Ordering PN for short time is not supported. In adults, administration of PN for 3 days or less is inappropriate. Use caution with following (see Table V):
|Severely limited IV access||PN may not be compatiblewith life saving medications||Obtain second line|
|Hemodynamic instability||Hyperosmolar PN maycontribute to volume shifts||Do not initiate PN untilhemodynamic stabilityis achieved|
|Significant hyperglycemia||PN may worsen glycemiccontrol||Do not start PN if bloodglucose >300 mg/dL.Consider insulin infusionduring initiation phase.Monitor POC glucose levelsclosely.|
|Severe electrolyte abnormalities||PN may worsen electrolyteabnormalities||Correct abnormalities priorto initiating PN and monitorclosely|
4. PN should be tapered down over 1-2 hours to avoid rebound hypoglycemia. In event of abrupt discontinuation of PN, infuse D10 solution at the same rate as the PN and monitor point of care glucose levels.
V. National Standards, Core Indicators and Quality Measures.
The Joint Commission has identified PN as a high risk IV product. They recommend the use of standardized commercial PN formulations for appropriate patients. ASPEN organization advocates a standardized process for PN management including use of commercial PN products, ordering, labeling, screening, and administration of PN. Customized PN formulations should be available for patients with complex nutritional needs.
VI. What’s the Evidence?
“A.S.P.E.N Enteral Nutrition Practice Recommendations”. JPEN J Parenteral Enteral Nutr. January 26, 2009.
“A.S.P.E.N Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient”. JPEN. vol. 40. February 2016. pp. 159-211.
“Comparison Between Premixed and Compounded Parenteral Nutrition Solutions in Hospitalized Patients Requiring Parenteral Nutrition”. Nutr Clin Pract. vol. 31. April 2016. pp. 229-234.
Corkins, MR, Guenter, P, DiMaria-Ghalili, RA. “Malnutrition Diagnoses in hospitalized patients: United States”. JPEN. 2010.
Kochevar, M. “ASPEN statement on parenteral nutrition standardization”. J Parenter Enteral Nutr. vol. 31. 2007. pp. 441-448.
Koretz, R. “Enteral nutrition: a hard look at some soft evidence”. Nutr Clin Pract. vol. 24. 2009. pp. 316-324.
Lloyd, DA. “Managing liver dysfunction in parenteral nutrition”. Proc Nutr Soc. vol. 66. 01-NOV-2007. pp. 530-8.
Mirtallo, J, Canada, T, Johnson, D, Kumpf, P, Peterson, C. “Safe practices for parenteral nutrition”. J Parenter Enteral Nutr. vol. 28. 2004. pp. 39-70.
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- I. Problem/Challenge.
- II. Identify the Goal Behavior.
- III. Describe a Step-by-Step approach/method to this problem.
- IV. Common Pitfalls.
- V. National Standards, Core Indicators and Quality Measures.
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