ENTERAL NUTRITION

Pharmacotherapy 4 for PharmD

Spring 2013

Introduction

• Enteral nutrition (EN) (= tube feeding): delivery

of nutrients by tube or by mouth into GI tract.

• Goal: to provide calories, macronutrients &

micronutrients to those patients who are unable to

achieve these requirements from oral diet.

• EN is the preferred method of specialized nutrition

support in many patients who are at risk of

malnutrition.

Indications for ENSuitable candidates:

• those who cannot or will not eat sufficient amount to meet nutritional requirements,

• those who exhibit sufficient functioning GI tract to allow absorption of nutrients,

• those in whom method of enteral access can be safely obtained.

• Most who require EN are critically ill patients who are endotracheally intubated for mechanical ventilation.

• Many of these patients may have ↓ gastric motility & emptying (sepsis, GI surgery, anesthetic agents, opioid analgesics, diabetic gastroparesis).

• → placing tip of feeding tube into duodenum, or preferably into jejunum.

Potential Indications for EN

Contraindications to EN

Absolute

• mechanical obstruction

• necrotizing enterocolitis.

EN difficult to perform:

• severe diarrhea

• protracted vomiting

• enteric fistulae

• severe GI hemorrhage

• intestinal dysmotility

EN versus PN

1. Clinical studies: EN in critically ill ↓ infectious complications

• Animal studies: EN prevents bacterial entry across gut.

• → EN is preferred over PN for feeding of critically ill patients requiring specialized nutrition support.

2. EN is > physiologic than PN in terms of nutrient utilization → fewer metabolic complications (glucose intolerance & ↑insulin requirements).

3. EN stimulates bile flow →↓ risk of developing cholestasis, gallbladder sludge & gallstones.

4. EN avoids potential infectious & technical complications associated with placement & use of central venous access device required for PN.

5. EN is <costly than PN when all factors are considered.

Early versus Delayed Initiation

• Studies comparing early versus delayed EN in critically ill patients showed trend toward ↓ infectious complications with early EN + trend toward ↓ mortality.

• But: In critically ill patients who are hemodynamically unstable, early EN may result in gut ischemia → initiation of EN should be delayed until patient is fluid resuscitated & has adequate perfusion pressure

• Early initiation of EN is not warranted for mild to moderately stressed patient who is otherwise well nourished (delay initiation of EN until oral intake is inadequate for 7-14 days)

Options & Considerations in Selection

of Enteral Access

Nasogastric, orogastric, nasoduodenal

& nasojejunal tube

Options & Considerations in Selection

of Enteral Access (cont’d)

Access sites for tube feeding.

Short-Term Enteral Access

• Is generally easier to initiate, < invasive & < costly than long-term access.

• The most frequently used routes: nasogastric [NG], nasoduodenal, or nasojejunal.

• Are used in hospitalized patient when anticipated tube feeding duration is < 4-6 weeks.

• Orogastric route is generally reserved for patients in whom nasopharyngeal area is inaccessible or in young infants who are obligate nasal breathers.

• These routes do not require surgical intervention → are least invasive.

• Feeding tube can be inadvertently pulled out relatively easily.

Short-Term Access (cont’d)

• Large-bore (14 French [F]) rigid NG tubes: low incidence of clogging, provide reliable way to measure gastric residual volumes.

• Disadvantage: patient discomfort.

• Small-bore nasal tubes (4F to 12F) for pediatric & adult patients.

• Tip of tube can be placed into stomach, duodenum, or jejunum.

• Are more comfortable.

• Disadvantage: may become easily occluded, do not allow reliable way to monitor gastric residual volumes, (collapse when aspiration of gastric contents is attempted) → when monitoring of gastric residual volumes is important, e.g., critically ill patient, large-bore NG tube is preferred.

Short-Term Access (cont’d)

• Many critically ill, injured, & postoperative patients exhibit delayed gastric emptying →<tolerate gastric feeding.

• Patients with diabetic gastroparesis, severe GERD or intractable vomiting are at > risk for aspiration.

• → placing tip of tube into duodenum or jejunummay be required.

• Small-bowel feedings were associated with possible reduction in gastroesophageal regurgitation & < rate of ventilator-associated pneumonia.

Short-Term Access (cont’d)

• Transpyloric route may be beneficial in patients who do not tolerate gastric feeding.

• Nasoenteric feeding tubes can be inserted at patient's bedside by trained medical personnel.

• - Greater skill is required to advance tip of feeding tube beyond pylorus.

• Prokinetic agents, such as metoclopramide & erythromycin, facilitate spontaneous passage of tube from stomach into small intestine.

• Variety of endoscopic & fluoroscopic techniques are used to insert transpyloric tubes.

• Radiographic confirmation of appropriate tip placement for feeding tubes inserted by bedside techniques should be obtained prior to use.

Long-Term Access

• Feeding tubes used for short-term enteral access are usually not optimal for long-term use because of patient discomfort, long-term complications, & mechanical failures that develop over time.

• Long-term access should generally be considered when EN is anticipated for > 4-6 weeks.

• Long-term enteral access options include gastrostomy, jejunostomy, esophagostomy, & pharyngostomy.

Long-Term Access (cont’d)

• Gastrostomy is the most common type of long-term enteral access - eliminates nasal irritation & discomfort & inadvertent removal is uncommon.

• Because feeding gastrostomies use large-bore tubes, clogging is less of a problem.

• The most common technique is percutaneous endoscopic gastrostomy (PEG): minimally invasive

• Only small children will usually require general anesthesia.

• PEG placement was associated with unexpectedly high 30-day mortality rate, possibly because patients had multiple coexisting morbid conditions.

• Patients with poor prognosis are not appropriate candidates for PEG placement.

Long-Term Access (cont’d)

• Once gastrostomy tract has matured → low-profile skin-level gastrostomy device may be placed for patient convenience & comfort.

• Exit site of all gastrostomies requires general stoma care to prevent inflammation & infection.

• In patients at high risk of GERD & aspiration who require long-term enteral access, jejunostomymay be the most appropriate option.

• Jejunostomies may be indicated in patients unable to tolerate gastric feeding due to impaired gastric motility or delayed gastric emptying.

• Because jejunostomies use smaller-bore tubes, occlusion occurs more commonly than with gastrostomy tubes.

Administration Methods

• continuous,

• cyclic,

• bolus methods

• May be accomplished by:

• syringe,

• gravity,

• infusion pump-controlled techniques

Continuous method• In hospitalized patient, is most commonly used for

initiation, & is generally preferred method in critically ill.

• < likely to result in abdominal distension, vomiting, & diarrhea than intermittent bolus method.

• Is preferred when EN is delivered into small intestine (better tolerance), may also be preferred in patients who have limited absorptive capacity due to rapid GI transit or severely impaired digestion.

• Delivery system: feeding reservoir or bag attached to extension set that is connected to infusion pump.

• ↑ nursing time because routine checks of enteral infusion are needed.

• For adults, EN infusion rates is generally 50-125 mL/h.

• In children, 1-2 mL/kg per hour can be started with advancements every 4-8 hours until the goal rate is achieved with good GI tolerance.

• Disadvantage: cost & inconvenience associated with pump & administration sets.

Other methods

Cyclic

• Patient who is not eating well during the day because of complaints of fullness & lack of appetite may benefit from trial of cyclic EN with enteral feeding held during the day & infused only at night.

• Patient is free from pump during the day allowing > mobility → useful for home patient or patient requiring rehabilitation.

• May be used in patients with either gastric or small bowel access.

Bolus

• Is most commonly used for patients in long-term care settings who have gastrostomy.

• Delivery of enteral feeding formulation is usually over 5-10 min.

• Syringe is used to instill feeding solution into tube.

• Instillation volume: 240-500 mL x 4-6 TD.

Other methods (cont’d)

• In children volume is usually 20 to 25 mL/kg per feeding until caloric requirements or adult volumes are reached.

• May result in cramping, N&V, aspiration, & diarrhea.

• Should be avoided in patients with delayed gastric emptying & who are at high risk of aspiration.

Intermittent

• If patient is experiencing intolerance to bolus administration over 5-10 minutes → administer prescribed volume over longer time, 20-60 min.

• Feeding formulation is emptied into reservoir bag or container & infused by infusion pump or gravity drip using roller clamp.

• Bolus method is more consistent physiologically with normal eating patterns → patients who need long-term EN & PN, especially children, may benefit when this approach is used because it minimizes development of cholestatic liver disease.

Enteral Feeding Formulation Selection

• Enhancements in enteral formulas to meet specific patient needs & improve tolerance: e.g., adding ribonucleic acid to enhance immune function.

• → nutraceuticals or pharmaconutrients

• Enteral feeding formulations are categorized by U.S. FDA as medical foods & are simply regulated to ensure sanitary manufacture.

• Nutrient complexity refers to amount of hydrolysis & digestion substrate source requires prior to intestinal absorption.

• Enteral formulas that contain partially hydrolyzed or elemental substrates are characterized as elemental, or defined-formula diets.

• Caloric contribution of each of macronutrients is as follows: carbohydrates, 4 kcal/g; protein, 4 kcal/g; & fat, 9 kcal/g.

Enteral Formula Nutrient Complexity

Protein Composition

• Protein sources may be partially hydrolyzed as peptides or L-amino acids.

• As molecular form of protein ↓ in size, osmotic load within enteral formula is increased.

• Conditionally essential amino acids formulations targeted for critically ill may be supplemented with glutamine &/or arginine.

• Glutamine was shown to be beneficial.

• ???There is no consensus on whether arginine-supplemented enteral formulations should be used in septic patients (might be harmful).

Carbohydrate Composition

• Usually provides the major source of calories.

• Elemental carbohydrates such as glucose & galactose contribute significantly to osmolality of enteral formulations, which is associated with feeding intolerance →polymeric entities are preferred.

• Glucose polymers provide useful carbohydrate source that is tolerated by most individuals: large chains that provide minimal osmotic load, yet are absorbed easily.

• Almost all commercially available enteral feeding formulations used in adults & older children are lactose-free - Why???

• Infant formulas are available with or without lactose.

Fat & Fatty Acid Composition

• Sufficient linoleic acid is required to prevent EFAD & should be ~ 1-3% of total daily calories.

• The most common sources of fat: vegetable oils (soy or corn) rich in polyunsaturated fatty acids.

• Concentration of fat is 2-45% of total calories.

• High fat content of diet → delayed gastric emptying.

• Enteral feeding formulations can contain fat as MCTs, from palm kernel or coconut oils.

• MCTs do not contain linoleic acid → formulations will also contain source of LCT to provide essential fatty acids.

Fat & Fatty Acid Composition (cont’d)

• Advantages of MCTs compared to LCT: more water soluble, undergo rapid hydrolysis, require little to no pancreatic lipase or bile salt for absorption, do not require carnitine for transport into mitochondria, do not require chylomicron formation for small-bowel enterocyte absorption.

• ↑ dietary proportion of omega-3 fatty acids to omega-6 fatty acids → < inflammation & immunosuppression may occur during metabolic stress.

• Docosahexaenoic acid (DHA) & arachidonic acid (ARA) supplementation provided benefits to child's visual function &/or cognitive & behavioral development in some, but not all studies.

• - Most infant formulas are now routinely supplemented with these fatty acids.

Fiber Content

• Fiber, as soy polysaccharides, has been added to several enteral feeding formulations intended for use in both children & adults (5.9-24 g/L of dietary fiber).

• Infant formulas do not contain fiber (exception is one formula intended for use in infants with diarrhea)

• Potential benefits of fiber:

- trophic effects on colonic mucosa + promotion of sodium & water absorption within colon.

- may help regulate bowel function in both normal individuals & in those with altered colonic motility.

- resulting short-chain fatty acids are excellent energy source.

• Fiber supplementation may be beneficial when long-term EN is required or in patients who experience diarrhea or constipation while receiving fiber-free enteral formulation.

Osmolality

• Iso-osmolar is considered to be ~300 mOsm/kg.

• Formulations that contain sucrose or glucose, dipeptides & tripeptides, & amino acids are generally hyperosmolar.

• ↑ caloric density also ↑ osmolality of enteral formulation.

• Osmolality of commercially available enteral feeding formulations ranges is 300-900 mOsm/kg.

• AAP: for infants ~ 450 mOsm/kg or <.

• Symptoms of gastric retention, diarrhea, abdominal distension, N&V have been attributed to enteral formulations having high osmolality (but: clinical evidence is lacking).

Renal Solute Load

• Is determined by protein, sodium, potassium, & chloride content of enteral formulation.

• Formulations that contain > solute load ↑ obligatory water loss via kidney.

• ~ 40-60 mL of water is minimal amount necessary to excrete 1 g of nitrogen.

• Those receiving high-protein enteral formulations unable to ingest > water, such as geriatric patient or patient with altered mental status, may be at risk for significant dehydration.

Adult Enteral Feeding Formulation

Classification System

MCT, medium-chain triglyceride; NPC:N, nonprotein calorie-to-nitrogen ratio.

Adult Enteral Feeding Formulation

Classification System (cont’d)

Pediatric Enteral Feeding

Formulation

Classification System

Pediatric Enteral Feeding

Formulation

Classification System (cont’d)

Pediatric Enteral Feeding

Formulation

Classification System (cont’d)

Standard Polymeric

• Are ~ isotonic (300 mOsm/L), provide ~ 1 kcal/mL, & are composed of intact nutrients in well-proportioned mix of carbohydrate, fat, & protein ± dietary fiber.

• Can provide nutrient requirements of majority of adults & children > 10 years of age receiving EN

• Nonprotein calorie-to-nitrogen ratio of these products is ~125:1-150:1.

• To maintain isotonicity, products within this category are not sweetened → not very palatable & generally only suited for tube feeding & not oral supplementation; however, flavored products are available.

High Protein

• Nonprotein calorie-to-nitrogen ratio < 125:1

• The lower the ratio, the higher protein density in relation to calories provided.

• Candidates: patients with trauma, burns, pressure sores, surgical wounds, high fistula output, & other critically ill patients (estimated protein requirements >1.5 g/kg per day).

• May also be beneficial in mechanically ventilated patients who are receiving propofol for sedation (vehicle is a soybean fat emultion that contains 1.1 kcal/mL) allowing provision of protein requirements while minimizing risk of overfeeding.

High Caloric Density

• Are concentrated to provide < fluid & electrolyte intake

• ~ 2 kcal/mL → allow using half the volume.

• Are often necessary for patients who require fluid &/or

electrolyte restriction (RI or CHF).

Elemental/Peptide Based

• Contain protein &/or fat components that are hydrolyzed into smaller, predigested forms (to optimize protein absorption in patients with impaired digestive or absorptive capacity).

• Are generally >in fat & use MCTs in varying proportions.

• Indications are not clearly established.

• Patients who do not tolerate standard, intact nutrient formulations as result of malabsorption might be candidates for trial of peptide-based formulation.

• Products that have higher percentages of MCTs & small amounts of LCT may be beneficial in chronic pancreatitis & cystic fibrosis, untreated celiac disease, biliary atresia or severe cholestasis, or chylothorax.

Disease Specific

• Specialized enteral formulations designed to modulate inflammatory response in patients with severe metabolic stress have been referred to as immune-enhancing formulations or immunonutrition: supplemented with glutamine, arginine, branched-chain amino acids, nucleotides, & omega-3 polyunsaturated fatty acids.

• Positive results: patients undergoing elective GI surgery, major cancer surgery of head & neck, & patients with severe trauma.

• Immune-enhancing formulations are associated with ↑ mortality in patients with preexisting severe sepsis.

• In ARDS, improved outcomes from using low carbohydrate formulation supplemented with specific fatty acids (eicosapentaenoic acid & γ-linolenic acid) & antioxidants have been documented.

Oral Supplements

• In general, are not intended for tube feeding, but to enhance oral diet.

• Are sweetened to improve taste → are hypertonic (~450-700 mOsm/kg).

• Osmolality is generally not a problem in patient with functioning GIT.

• In tube-fed patient, sweetened product is unnecessary & may contribute to GI intolerance, particularly diarrhea.

• Powder supplements that are mixed with milk should be avoided in lactose-intolerant patients.

• In addition to liquid supplements, puddings, gelatins, bars, & milkshake-like supplements are available.

Modular Products

• Powder or liquid (i.e., protein, carbohydrate, or fat) may be is used to supplement commercially available enteral formulation.

• May be necessary, especially in children, to achieve nutrient mix not supplied by single product.

• Formulations available in powder or concentrate can be also mixed with < water than needed for standard dilution to deliver > nutrients in < volume.

• Infant formulas generally are concentrated beyond their standard concentration in this way.

• Mixing process ↑ potential for contamination & incorrect preparation.

• Human milk fortifiers add additional calories, protein, & minerals & have been shown to improve nutritional outcomes in human milk-fed premature infants.

Rehydration

• Oral rehydration formulations are useful in maintaining hydration or treating dehydration in adult & pediatric patients with high GI output.

• Are available commercially in powder or liquid form or can be extemporaneously compounded.

• Can be administered orally or given via feeding tube.

• Glucose content is important because it stimulates active transport systems → passive sodium & water uptake simultaneously with glucose

• → may ↓ fecal water loss & generate positive electrolyte balance.

Formulary & Delivery System

Considerations

• Advantages of ready-to-use liquid formulations are convenience & lower susceptibility to contamination.

• One disadvantage is that > storage space is required.

• Ready-to-use liquid enteral formulations are available in rigid containers, cans, or closed, ready-to-hang bags.

• Bolus administration of EN is usually achieved using formulas available in cans.

• When formula from can is used for continuous or cyclic administration, it must first be poured into bag or bottle to allow for infusion via pump.

• Powder formula is open system of delivery.

Formulary & Delivery System

Considerations (cont’d)

• Powdered products are not guaranteed to be sterile by manufacturer because proper sterilization would destroy some of its components.

• FDA warns regarding use of powdered formulations in premature neonates & other immunocompromised infants.

• Powder formulations require reconstitution, often in blender that is difficult to sterilize, they are also > susceptible to contamination.

• Stringent handling procedures are recommended during all aspects of enteral feeding preparation & delivery to minimize contamination risk.

• Closed-system containers supply ready-to-hang, prefilled, sterile supply of formula in volumes of 1-1.5 L.

• Closed-administration system also offers advantage of not requiring refrigeration & allowing hang times beyond 24-36 hours, whereas conventional open-delivery systemnecessitates hang times of generally 4-8 hours.

Initiation & Advancement Protocol

• Typical recommendation for continuous administration of EN for adults is to start at 20-50 mL/h & advance by 10-25 mL/h Q 4-8 hrs until desired goal is achieved.

• For intermittent administration: to start at 120 mL Q 4 hrs & advance by 30-60 mL Q 8-12 hours.

• In children, recommendation for continuous administration is initiation of 1-2 mL/kg per hr or 20-25 mL/kg per bolus with advancement by 2 mL/kg per hr Q 4-12 hrs.

• In premature infants, initiate at lower rates usually 10-20 mL/kg per day.

• Diluting enteral feeding formulations is not routinely recommended unless necessary to ↑ fluid intake.

• Clinical signs of intolerance include abdominal distension, abdominal cramping, high gastric residual volumes, aspiration, & diarrhea.

Suggested Monitoring for Patients on

EN

Suggested Monitoring for Patients on

EN (cont’d)

Complications & Monitoring

Majority of complications are:

• metabolic,

• GI,

• mechanical.

Metabolic Complications

• Are similar to those associated with PN, but incidence tends to be < (< rates than PN)

• Complications related to hydration & electrolyte imbalance & altered glucose control are observed > frequently in critically ill patients, especially those with underlying organ dysfunction.

• Patients receiving long-term EN at home may only require laboratory monitoring every 2-3 months, depending on their clinical status.

• In addition to macronutrient content, it is important to evaluate actual content of water & micronutrients provided by enteral formulations, especially in critically ill patients.

• Supplemental fluid & electrolytes may be required in some.

• Patients who have fluid retention or ↑ serum electrolytes, may need > concentrated formulation or containing < of a particular nutrient.

GI Complications

• Include N&V, abdominal distension, cramping, aspiration, diarrhea, & constipation.

• For patients receiving tube feeding into stomach, gastric residual volumes are widely used as indicator of tolerance (volume of contents in stomach measured by using syringe & aspirating from large-bore NG or gastrostomy tube.

• Patients with high gastric residual volumes may be at > risk of vomiting &/or aspiration.

• Frequency of measuring gastric residual volumes is generally 4-8 hours.

• In adults, definition of high residual volume ranges from > 200 mL to > 500 mL.

• In children, residual volumes > twice bolus volume or twice hourly infusion rate for continuous gastric feedings are considered excessive.

GI Complications (cont’d)

• Symptoms such as abdominal distension, fullness, bloating, & discomfort should also be assessed (> reliable indicators of EN intolerance).

• Trend in ↑ gastric residual volumes is generally > important than isolated high measurement.

• ↓ in tube feeding rate may be warranted.

• Abruptly stopping tube feeding should be reserved for patients with overt regurgitation or aspiration.

• Gastric residual volumes should generally be returned to patient unless they are excessive (> 500 mL in adults).

• It may be beneficial to initiate prokinetic agent e.g. metoclopramide

• If high gastric residual volumes persist, transpyloric feeding tube may be considered for feeding into small bowel.

• Trial of PPI or H2RA, ↓use of narcotics, sedatives, or other agents that may delay gastric emptying may help.

Aspiration pneumonia

• Is the most serious complication & is potentially life-threatening.

• Risk factors:

- previous aspiration episode,

- ↓ LOC,

- neuromuscular disease,

- structural airway or GI tract abnormalities,

- endotracheal intubation,

- vomiting,

- persistently high gastric residual volumes,

- prolonged presence in supine position.

• Identification of these risk factors, along with close monitoring of gastric residual volumes, is recommended for management of critically ill patients receiving tube feeding.

Aspiration pneumonia (cont’d)

• HW: method to detect aspiration of feeding formulation into the airways & its disadvantage?

• Strategies to ↓ aspiration risk:

• keeping patient's head of bed elevated to 30-45° angle during feeding & for 30-60 min. after intermittent boluses.

• Changing from bolus or intermittent to continuous administration may also ↓ risk.

• Regular assessment of tube position is recommended.

Diarrhea

• Incidence in patients receiving EN is 20-70%

• When monitoring for diarrhea, stool frequency, consistency, & volume should be evaluated & previous bowel habits should be considered.

• One commonly accepted definition of diarrhea is > 3-5 liquid stools per day or > 250-500 mL/day (10 mL/kg per day in children) stool output for at least 2 consecutive days.

• Tube feeding-related factors that may contribute to diarrhea:

- too rapid delivery or advancement of formula,

- intolerance to formula composition,

- administering large volumes of feeding into small bowel,

- formula contamination.

Diarrhea (cont’d)

• If diarrhea occurs when using fiber-free formulation, consider switching to fiber-containing formulation.

• If using high-fat formulation, it may be beneficial to switch to formulation lower in fat or having proportion of fat supplied as MCTs.

• If protein malabsorption is suspected, switching from intact protein to peptide-based source may be beneficial.

• Avoid lactose-containing enteral formulations (majority of products are lactose-free).

• Assess risk of bacterial contamination of formula & take steps to ↓ potential risk factors.

• Infectious etiologies should be excluded

• Pharmacologic intervention to control severe diarrhea: use of opiates, diphenoxylate, & loperamide.

Diarrhea (cont’d)

• Common cause of diarrhea unrelated to tube feeding is drugs, particularly broad-spectrum antibiotics & sorbitol contained in many liquid medication formulations.

• In addition, many drugs available in liquid form are hyperosmolar, which may also contribute to diarrhea.

• All medications should be evaluated for their potential contribution.

• Infectious causes, such as antibiotic-induced bacterial overgrowth by Clostridium difficile or other intestinal flora, need to be considered.

• Diarrhea also may occur as result of malabsorption, secondary to underlying disease state or condition.

Mechanical Complications

• Feeding tube occlusion: result of improper administration of medications &/or flushing technique.

• Kinking of tube also may cause occlusion.

• Tube should be flushed with at least 30 mL of water before & after administering any medication (children < 30 mL depending on size of tube).

• Frequency of flushing should be at least Q 8 hrs during continuous feeding & before & after each intermittent feeding.

• If tube occlusion occurs, attempt to irrigate tube with warm water should be made.

• Some success has been shown with pancreatic enzymes mixed in sodium bicarbonate.

• Declogging devices that are specifically designed to unclog feeding tubes are available

Mechanical Complications (cont’d)

• Inadvertent tube removal or displacement: > 50% of patients.

• Measures to ↓ agitation & confusion should be attempted.

• Securing tube with tape may be helpful, as well as marking tube with permanent ink at exit site to assess for change in position.

• When feeding tube is inserted nasally or orally, there is risk that tube may inadvertently enter tracheobronchial tree (higher in patients who have impaired cough or gag reflex & when stylet is used for tube insertion).

• Proper positioning of tube should always be confirmed by radiography prior to feeding initiation to avoid inadvertent administration of enteral formula into lung.

Drug Delivery Via Feeding Tube

Concomitant Drug Administration

• Limitations:

- Medications delivered into small bowel may result in alterations of drug dissolution because stomach is bypassed.

- therapeutic effect designed to occur within stomach (antacids & sucralfate) may be influenced.

- many drugs are best absorbed in fasted state (should be administered on empty stomach as much as possible).

- patients receiving bolus gastric feedings may receive medications appropriately spaced between feedings, but patients receiving continuous feeding will require interruption for drug administration.

• medications in sublingual form, sustained-released capsules or tablets, & enteric-coated tablets should not be crushed & therefore should not be administered via enteral feeding tubes.

Drug Delivery Via Feeding Tube (cont’d)

Concomitant Drug Administration (cont’d)

• Solid dosage forms that are appropriate to crush should be prepared as very fine powder & mixed with 15-30 mL of water or other appropriate solvent before administering through tube.

• Content of many capsules may be opened & administered.

• It may be acceptable to administer intact pellets through feeding tube (should be small enough).

• Liquid dosage preparations have been used but risk of GI intolerance should be considered because of hyperosmolality & possible sorbitol content; they may not be the best choice if case of GI intolerance.

• At least 30 mL of water in adults & usually 10-15 mL in children should be given before & after medication administration

• If > than 1 medication is scheduled for given time, each should be administered separately & tube should be flushed with at least 5 mL water between them.

Admixture of Drugs with Enteral

Feeding

• May result in physical incompatibilities, including granulation, gel formation, separation, & precipitation

• →may inhibit drug absorption, gel formation potentially may clog small-bore enteral feeding tubes.

• Physical incompatibility with medications is more common in formulations that contain intact protein than in those with hydrolyzed protein.

• Also, more common with use of acidic pharmaceutical syrups

• → avoid routine admixture whenever possible, especially for nonaqueous preparations & syrups.

• Exceptions: adding electrolyte injections of potassium or sodium to enteral formulas to assist in maintaining or repleting electrolytes.

Drug–Nutrient Interactions

• One of the most studied interactions: phenytoin & enteral feeding →↓ phenytoin bioavailability

• →↓ phenytoin serum concentrations by as much 50-75%, possibly as result of binding of phenytoin to calcium caseinates or protein hydrolysates in enteral formulation.

• Patients typically require higher than normal phenytoin doses while receiving EN.

• Patient's clinical response & phenytoin serum concentrations should be monitored closely if phenytoin is given enterally during continuous enteral feeding & after its discontinuation.

• Some clinicians choose to hold feeding for 1-2 hours before & after phenytoin administration to minimize interaction.

Medications with Special

Considerations for Enteral Feeding

Tube Administration

Warfarin:

Consider

holding

tube

feeding 1

hour

before &

after

administr

ation

Drug–Nutrient Interactions (cont’d)

• ↓ bioavailability of certain antibiotics, particularly quinolones, has been documented when coadministered with enteral feeding.

• Ciprofloxacin absorption is significantly ↓ when given via a jejunostomy tube, so this practice should be avoided.

• Holding tube feeding for 30 min. before & 30 min. after quinolone administration has been recommended (not been shown to improve drug absorption).

• Warfarin resistance has been documented → vitamin K content within formulas intended for use in adults was reformulated to < 200 mcg/1,000 kcal.

• Warfarin dosage ↑ & INR monitoring may be required in patients receiving EN.

• When EN is discontinued, ↓ in warfarin dose may be required.

Developing EN regimen

Nutrition Outcome Goals

• Are to promote adequate nutritional state in adults & promote growth & development of infants & children.

• Assessing outcome includes monitoring objective measures of body composition, protein & energy balance, & subjective outcome for physiologic muscle function & wound healing.

• Besides improvement in nutrition outcome, another goal of EN is to ↓ disease-related morbidity (length of hospital stay, infectious complications, & patient's sense of well-being) & mortality.

• Avoid need for PN in patients unable to meet nutrient requirements with oral diet.