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 DOI: 10.1177/0115426503018005422

2003 18: 422Nutr Clin PractLinda M. Lord

Restoring and Maintaining Patency of Enteral Feeding Tubes  

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Techniques and Procedures

Restoring and Maintaining Patency of Enteral Feeding Tubes

Linda M. Lord, NP, MS, CNSNUniversity of Rochester Medical Center

Feeding the gastrointestinal tract directly withenteral nutrition, as opposed to parenteral feeding,has been recently recognized by the Agency forHealthcare Research and Quality as one practiceshown to have significant positive health care out-comes at a lower cost.1 As institutions move fromusing parenteral nutrition support to enteral tubefeedings, a knowledge base should be obtained tomake this practice successful and minimize compli-cations. One common complication is tube clogging,especially in long, small-bore feeding tubes usedfrequently in acute care settings. Nasally placedfeeding tubes and jejunostomy tubes tend to clogmore readily than gastrostomy tubes because theyare longer, with a smaller internal diameter. Theability to minimize tube clogging will save time andexpense, decrease radiographic exposure for tubeplacement confirmation, decrease patient traumaexperienced during nasally inserted tube reinser-tions, and minimize trips to endoscopy or radiologyfor replacement of jejunal catheters. Lowering theincidence of tube clogging will also allow for theprovision of nutrients and fluid needed to achievebetter health care outcomes.

Etiology and Prevention of Tube CloggingFeeding tubes can clog for a variety of reasons

that include the formation of a formula precipitatefrom contact with an acidic fluid, stagnant formula,feeding tube properties, contaminated formula, andimproper medication administration. Addressingeach of these potential causes for tube clogging willhelp ensure feeding tube patency and uninterruptednutrition formula delivery.

Formula Contact With Acidic FluidSeveral investigations have shown the impor-

tance of preventing the mixture of the nutrition

formula with acidic gastric secretions. In an in vitroinvestigation by Marcuard and Perkins,2 tube clog-ging occurred when intact protein nutrition formu-las containing casein were acidified to a pH �4.6.Clumping did not occur with elemental or semiele-mental nutrition formulas at the same lowered pH.These results were confirmed in another in vitroinvestigation by Hofstetter and Allen,3 whereclumping occurred within 35 seconds in intact pro-tein formulas containing casein when their pH val-ues were lowered to 4.6. This article pointed out thatcasein, a milk protein, denatures at its isoelectric pHpoint of 4.6. The isoelectric pH point of a protein iswhere all positive charges are equal to all negativecharges in the protein molecule. It was also shownthat the clumping did not occur with elemental orsemielemental formulas because these containeither free amino acids or small peptides. Further-more, it was discovered that the addition of sodiumor calcium caseinate to nutrition formulas signifi-cantly increased the tendency to clump. Interest-ingly, when feeding tubes were placed in simulatedgastric juice and formulas either flowed at a slowrate or were stopped, formula clumping occurred ina retrograde manner in the tube tips. Gastric juicestend to be acidic, with a pH of 1.5. In an in vivoinvestigation by Powell et al,4 it was shown thattube clogging occurred less frequently when thefeeding tubes were not used to check for gastricresiduals. Feeding tubes clogged more frequently inpatients fed with intact protein formulas when gas-tric residuals were checked on a 4-hour schedule. A10-mL water flush was instilled to flush the feedingtube before and after each residual check to mini-mize the mixing of the nutrition formula with theacidic gastric juices. Despite this, increased cloggingoccurred with routine gastric residual checks, and itwas theorized that the contact with gastric juiceslowered the luminal pH, causing a precipitation ofthe nutrition formula and subsequent tube clogging.By comparison, jejunal aspirates tend to be neutralto alkaline, with a pH of 7.6. No tube cloggingoccurred at a pH of �6 in the Hofstetter and Allenstudy3 or �5 in the Marcuard and Perkins2 inves-tigation. In continuing research, Marcuard andStegall5 observed the incidence of clogging in gastricvs small bowel feeding tubes. Clogging occurred in44% of 57 tubes placed in the stomach vs 15% oftubes placed in the small bowel.

Correspondence: Linda M. Lord, NP, MS, CNSN, 601 ElmwoodAvenue, Box 667, Rochester, NY 14642. Electronic mail may besent to linda_lord@urmc.rochester.edu.

0884-5336/03/1805-0422$03.00/0Nutrition in Clinical Practice 18:422–426, October 2003Copyright © 2003 American Society for Parenteral and Enteral Nutrition

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Prevention of Acidified FormulaIn order to prevent tube clogging from an acidified

formula, it would be prudent to flush immediatelybefore and after checking for gastric residuals withat least 20 to 30 mL of water. Liquid medicationswith a pH of �5 should never be mixed with thenutrition formula, and if delivered via the feedingtube, they should be maximally diluted and a 30 mLwater flush should be delivered before and afteradministration.6 The use of small bowel feedings,which are already advocated in the critically illpatient population as a means to deliver early nutri-tion support, would obviate the concern of clogformation from gastric acid.

Stagnant FormulaNutrition formulas can easily form a clog when they

are infusing at slow rates or paused and water flushesare not properly delivered. This occurs because nutri-tion formulas are suspensions, and the larger particles(sodium, calcium caseinate, and soy protein) are proneto settle in the horizontal segment of the tube if theflow rate is too slow or stops.7 Calorically dense orfiber-containing formulas are more viscous and fur-ther increase the risk for clogging.

Prevention of Stagnant FormulaIn order to minimize clogging, feeding tubes should

be flushed routinely with about 30 mL of water at leastevery 4 hours during continuous feedings and at least30-mL water flush after each intermittent or bolusfeeding. Enteral infusion pumps should be used whenslow infusion rates are ordered. Nutrition formulasshould not be allowed to run dry, and pump alarmsshould be responded to promptly.

Feeding Tube PropertiesClogging tends to occur less frequently with poly-

urethane feeding tubes compared with siliconetubes, possibly because silicone tubes tend to havethicker walls, decreasing their internal diameters.8

In addition, thick yeast colony formation has beenreported in 3 silicone feeding tubes, leading to tubeocclusion in 2.9 All tubes were 20 French andincluded 2 percutaneous gastrostomy tubes and 1jejunostomy tube. Histologic dissection of thesetubes showed that the yeast actually penetrated thesilicone material and became very adherent. Thetubes that clogged did so within 2 to 3 months.Associated with the yeast formation wasobserved tube material fatigue. The 2 occludedtubes became opacified and nodular and the thirdtube became darkly discolored. Feeding tubeswith more than 1 exit portal hole have beenshown to clog more frequently than those with 1exit hole, possibly because of the higher exposureof the nutrition formula to gastric acid.3 Tubediameter has not been shown to have a signifi-cant effect on tube clogging. Feeding tubes should

be replaced per manufacturer guidelines, and ifmaterial tube fatigue is detected, the tube shouldbe replaced sooner.8

Contaminated FormulaA formula clog may also be caused by significant

contamination (bacterial counts of 107 cfu/mL) thatcauses the formula to coagulate.10

Prevention of Formula ContaminationProper hand-washing and clean technique should

be used when preparing and administering the for-mula to minimize contamination. Manufacturer’srecommendations should be followed regarding for-mula hang times and proper use of the enteraldelivery sets. Nutrition formula contamination canfurther be prevented by incorporating any addi-tional fluid requirements into the water flushesinstead of diluting the nutrition formula.

Solutions for Feeding Tube FlushesVarious solutions have been used to flush feeding

tubes. These include water, carbonated beverages,and cranberry juice.7,11 Cranberry juice has consis-tently been shown to be inferior to water in prevent-ing tube clogging.8,11 This is most likely because ofthe stickiness of the juice and its lower pH.3,8 Cran-berry juice pH values range from 2.5 to 2.7. CocaCola (The Coca Cola Company, Atlanta, GA) wasalso compared with water as a feeding tube flushand showed no difference in clogging rates. This issurprising because Coca Cola is as acidic as cran-berry juice, with a pH of 2.5. Nonetheless, water isthe preferred solution for feeding tube flushesbecause it is easily obtainable at low cost, and nosolution has been shown to be superior in maintain-ing tube patency.

Medication ClogsTube clogging can be caused by inadequately

crushed pills, congealed medications or precipitateformation from medication with formula, or medica-tion interactions.

Prevention of Medication ClogsWhenever possible, liquid medications should be

used. Elixirs or suspensions are less likely to causeclogging compared with syrups that tend to beacidic. Pharmacies may be able to formulate a liquidsolution or suspension from powders or tablets. Ifnot, tablets should be crushed into a fine powder anddispersed well in warm water. A tablet-crushing60-mL syringe is available called the Pill Crusher(Welcon, Fort Worth, TX). The tablet is placed in thesyringe barrel, and the corrugated plunger acts as acrushing mechanism. This allows for the crushing ofthe tablet, drawing up of water, and the administra-tion of the diluted medication through the feeding

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tube, all with the same syringe. Enteric-coated ortime-released tablets or capsules should not becrushed. Avoid the administration of bulk-formingagents such as soluble fiber (ie, psyllium) throughfeeding tubes, as they quickly congeal when com-bined with water. However, there are some fibersources that have instructions included for tubefeeding administration. For example, KananaBanana flakes (Corpak Medsystems, Wheeling, IL)is a powder packet of instant banana flakes thathave directions for feeding tube administrationprinted on the packet. One tablespoon of powder canbe mixed with 60 mL of water and delivered bysyringe method via the feeding tube. Benefiber(Novartis, Fremont, MI) is also a soluble fiber sourcethat is 100% water soluble. According to instructionson the 7.2 oz canister, Benefiber (1 tablespoon) canbe added to 2 to 4 oz water, mixed well, and instilledinto feeding tubes. Feeding tubes should be flushedwith 20 to 30 mL water before and after the admin-istration of these fiber supplements. Manufacturersof Kanana Banana flakes and Benefiber state thatthese powders should never be put into nutritionformulas because the formula will thicken andpotentially cause clogging. Nutrition formulas areavailable that already contain insoluble fiber or ablend of soluble and insoluble fibers. Manufacturersrecommend that fiber-containing nutrition formulasbe shaken vigorously before administration toensure that the fiber remains in solution.

Medications should not be mixed together ormixed with the nutrition formula, unless approvedby a pharmacist. Medications can interact with eachother, negating a drug’s therapeutic effect by phys-ically or chemically reacting to each other or alteringthe pH. These interactions may not be visible, orthey may be visible and form a precipitate, poten-tially causing a tube to clog. Medications can alsointeract with the nutrition formula, denaturing theprotein, causing a precipitate and potential tubeclogging, or negating the therapeutic effect of thedrug. Feeding tubes should be flushed with 25 mLwater before and after medication administration,and medications should be administered separatelywith at least a 5 mL water flush between each one.12

Some medications can significantly interact with thenutrition formula within the gastrointestinal tract,and the feeding infusions need to be held for aprescribed time interval before and after medicationdelivery. Examples of these medications are the oralforms of ciprofloxacin, sucralfate, phenytoin, andmycophenolate.

Pancreatic Enzyme LockIn an intermittent feeding schedule, a pancreatic

enzyme lock may be used to prevent tube clogging.Sriram et al13 found less clogging in patients’ feed-ing tubes that were flushed with a pancreatic

enzyme suspension and maintained as a “lock” inbetween feedings. The pancreatic enzyme suspen-sion contained pancreatic enzyme powder that wasactivated by adding sodium bicarbonate powder and15 mL of sterile water. A pH value of 7.5 wasachieved. The researchers used 5 mL of this suspen-sion as the “lock,” because it was determined thatthis volume was sufficient to completely fill theinternal lumen of all varieties of feeding tubes. Thiswas compared with a previous control group whoonly received a standard 50 mL water flush every 4hours.

Tube UncloggingVarious liquid irrigants, enzyme solutions, and

mechanical devices have been used to salvage aclogged feeding tube. A tube will more likely becleared from a clog the sooner the unclogging pro-cess begins after clog formation.14 This makes itvital to respond to pump alarms or sluggish flowrates promptly. It also makes it important to haveunclogging materials close at hand.

Liquid IrrigantsTechniques using the instillation of liquid irrig-

ants (water or carbonated beverages) or enzymesolutions rely on contact of the liquid and the clog.Various liquids and enzyme solutions were evalu-ated in vitro by Marcuard et al15 for their ability todissolve a clog. The liquids included distilled water,carbonated beverages (Mountain Dew; PepsiCo,Purchase, NY), Pepsi (PepsiCo), Classic Coke (CocaCola Company), and Sprite (Coca Cola Company),papain, plain Viokase (Axcan Scandipharm, Bir-mingham, AL) and activated Viokase. The pH of theactivated Viokase and distilled water were adjustedto 7.9 by adding 1-N NaOH. Various intact nutrientformula clogs were placed in each liquid and adissolution score was assigned. These scores rangedfrom 0 (no dissolution) to 4 (total dissolution). Thehighest dissolution score was achieved by the acti-vated Viokase, and the lowest scores were observedwith the papain solution and plain Viokase. Of note,the water adjusted to an alkaline pH similar to theactivated Viokase had significantly lower dissolu-tion scores. This shows that the action of the Viokaseitself, not the pH, is the probable reason for thesignificantly higher dissolution scores. The authorsattribute the success to chymotrypsin, which is aproteolytic enzyme known to cleave peptide bondsand polypeptide chains. Part II of this investigationevaluated the ability of Pepsi to unclog 8 polyure-thane, 8 French feeding tubes, and if unsuccessful,the activated Viokase was trialed. Because this wasdone in vitro, the clogs could be worked on promptly.After aspirating any luminal contents, a 50 mLsyringe was filled with the Pepsi and administeredin the tube under manual pressure for 1 minute. The

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tube was then clamped for 5 minutes. Patency wasrestored in only 2 tubes. When the activated Viokasesolution was used with the same technique, theremaining 6 tubes were successfully unclogged. PartIII was an in vivo study evaluating the ability ofwater, and then the activated Viokase, to clearfeeding tubes in 10 patients. An elongated, small-diameter, hollow catheter (Drum-cartridge catheter)was inserted in the feeding tube. It was thenattached to the end of the syringe to direct the liquidin close proximity to the clog. Initially, 5 mL of waterwas instilled under manual pressure for 1 minuteand then clamped for 5 minutes. No tube wascleared by this method. The activated Viokase wasthen tried with the same technique, and 5 tubeswere successfully cleared at the first attempt and 2more by the second attempt. Part III was continuedby this research team, with a total of 32 patientsincluded in the data collection.5 Sixty tube occlu-sions were discovered within an 8 month period, andin 44, tube unclogging was attempted. Water wassuccessful in clearing the clog in 12 tubes. In theremaining 32 cases, the activated pancreaticenzyme cleared the clog in 23 tubes. In the 7 remain-ing tubes, 6 contained nonformula clogs. Theseincluded 2 knotted tubes, 3 tubes that had impactedtablet powder, and 1 tube with a trapped tomatoseed. The 1 tube that had the formula clog wasclogged for 24 hours, allowing a 45 cm-length for-mula clog to develop.

To simulate the activated Viokase solution above,1 crushed tablet Viokase or 1/4 teaspoon Viokasepowder and 1 crushed nonenteric coated 324 mgsodium bicarbonate tablet or 1/8 teaspoon bakingsoda can be added to 5 mL of tap water. This resultsin a Viokase pH 7.9 solution.15

The Clog Zapper (Corpak Medsystems, Wheeling,IL) is a kit that contains a 10 mL oral syringe witha patented enzyme powder, a 6 mL syringe, a12-inch hollow, small-diameter catheter, and 4 � 4gauze pads. The 12-inch catheter is inserted into thefeeding tube. The enzyme powder is reconstitutedwith water and instilled through the catheter. Therecommended wait time is 30 to 60 minutes. The6-mL syringe is then used for a water flush. Thistechnique was tested in 17 patients with a variety ofnasally inserted small-bore tubes and jejunostomytubes.16 All tubes had formula clogs, but the lengthof time the tube was occluded was unknown. TheClog Zapper technique was successful in unclogging15 tubes on the first attempt and the remaining 2tubes on the second attempt. The advantage ofhaving this kit on hand is the ability to work on aclog as soon as possible with an ideal uncloggingagent.

Mechanical Declogging DevicesMechanical devices rely on methods that physi-

cally grind down clogs. The DeClogger (Bionix,

Toledo, OH) is an elongated, flexible, plastic devicewith a screw-threaded end that has been approvedby the FDA for insertion into gastrostomy tubes andlarge-bore jejunostomy tubes. It is available in avariety of French sizes and lengths. The DeCloggeris rotated within the lumen of the feeding tube tobore through a clog. A cytology brush has also beenshown to successfully unclog small-bore nasoentericfeeding tubes.17 One drop of silicone is applied to thebrush and the brush inserted to a premeasuredlength and removed. Both these mechanical devicesshould be premeasured so as not to exceed thelength of the feeding tube, to prevent tube damage.

ConclusionProper tube feeding administration and handling,

water flushes, and medication administrationshould minimize the incidence of tube clogging. Ininstances where it would be difficult to replace aclogged tube (ie, newly placed jejunostomy tubes,jejunal extensions placed through gastrostomytubes, or nasoenteric tubes), it may be prudent toinstill a pancreatic enzyme “lock” in between feed-ings. As an alternative, our service has found ithelpful to administer activated Viokase solution, asdescribed above by Marcuard,15 for 30 minutes perweek in the nasoenteric and jejunal feeding tubes ofour home patient population. We found that thispractice successfully resolves sluggish infusions andprevents tube occlusions, possibly by clearing anyresidue buildup in the tube lumen. When a clog isdiscovered, it should be resolved as soon as possiblewith literature-supported methods to improve thechances of clearing the tube. The uninterrupteddelivery of needed nutrients and fluid should helpdecrease nutrition- and fluid-related complicationsand minimize patient anxiety over tube replace-ments.

References1. Agency for Healthcare Research and Quality. Making Health

Care Safer. No. 43; Nutritional Support. Part III, Section E,Chapter 33, 1991

2. Marcuard SP, Perkins AM. Clogging of feeding tubes. JPEN12:403–405, 1988

3. Hofstetter J, Allen LV. Causes of non-medication-induced naso-gastric tube occlusion. Am J Health Syst Pharm 49:603–607, 1992

4. Powell KS, Marcuard SP, Farrior ES, et al. Aspirating gastricresiduals causes occlusion of small-bore feeding tubes. JPEN17:243–246, 1993

5. Marcuard SP, Stegall KL. Unclogging feeding tubes with pancre-atic enzyme. JPEN 14:198–200, 1990

6. Altman E, Cutie AJ. Compatibility of enteral products withcommonly employed drug additives. Nutr Support Serv 4:8–17,1984

7. Nicholau DP, Davis SK. Carbonated beverages as irrigants forfeeding tubes. Ann Pharmacother 24:840, 1990

8. Metheny N, Eisenberg P, McSweeney M. Effect of feeding tubeproperties and three irrigants on clogging rates. Nurs Res 37:165–169, 1988

9. Marcuard SP, Finley JL, McDonald KG. Large-bore feeding tubeocclusion by yeast colonies. JPEN 17:187–193, 1993

October 2003 425RESTORING AND MAINTAINING PATENCY OF ENTERAL FEEDING TUBES

at Scientific library of Moscow State University on December 4, 2013ncp.sagepub.comDownloaded from

10. Kohn CL. The relationship between enteral formula contamina-tion and length of enteral delivery set usage. JPEN 15:567–571,1991

11. Wilson MF, Haynes-Johnson V. Cranberry juice or water? Acomparison of feeding-tube irrigants. Nutr Supp Serv 7:2324,1987

12. Scanlan M, Frisch S. Nasoduodenal feeding tubes: Prevention ofocclusion. Am Assoc Neurosci Nurs 24:256–259, 1992

13. Sriram K, Jayanthi V, Lakshmi RG, et al. Prophylactic locking of

enteral feeding tubes with pancreatic enzymes. JPEN 21:353–356, 1997

14. Mateo MA. Maintaining the patency of enteral feeding tubes.Online J Knowl Synth Nurs 1, 1994

15. Marcuard SP, Stegall KL, Trogdon S. Clearing of obstructedfeeding tubes. JPEN 13:81–83, 1989

16. Corpak Medsystems. Clog Zapper™ Clinical Results, 199717. Caos A, Gogel HK. A simple method for clearing obstructed

enteral feeding tubes. Gastrointest Endosc 32:55, 1986

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