peripheral parental nutrition

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20TH ANNIVERSARY Vol. 21, No. 6 June 1999

Refereed Peer Review

FOCAL POINT

KEY FACTS

#Peripheral parenteral nutrition(PPN) is a safe, simple technique

that can be used as an alternative

to total parenteral nutrition (TPN)

in selected patients.

PeripheralParenteral NutritionTufts University

Erika Zsombor-Murray, DVMLisa M. Freeman, DVM, PhD

ABSTRACT: Many clients now expect appropriate nutritional support to be provided to their

hospitalized pets. In many veterinary clinics, enteral nutrition via feeding tubes is perceived to

be the only viable option. Although enteral nutrition is usually the preferred method, parenteral

nutrition is the method of choice when the enteral route is contraindicated. Advances in the

formulation of parenteral nutritional solutions, intravenous catheters, and administration tech-

niques make its use more amenable to veterinary clinics. Parenteral nutrition administered

through a peripheral vein can be used as an alternative to total parenteral nutrition in appropri-

ate patients.

M

etabolic alterations put ill and traumatized patients at risk for malnu-trition and its deleterious effects on immune function, wound healing,and overall survival.1 The benefits of nutritional support in preventing

malnutrition are well accepted, but the optimal use of parenteral or intravenousnutrition is controversial. In the past, parenteral nutrition was recommendedonly when enteral nutrition was contraindicated; parenteral nutrition was some-times considered a technique that should be avoided at all costs because of itspotential complications. Administering parenteral nutrition has also been pre-sented as a complicated prospect for nutritional support. Thus, its use in veteri-nary medicine has been primarily limited to universities and a few referral hospi-tals. However, parenteral nutrition is now more accepted, safer, and easier than itonce was, and its use is becoming more feasible for all veterinarians. Much of theinitial resistance to parenteral nutrition was the result of its potential complica-tions, some of which can be overcome or minimized by using the peripheralroute of administration.

HISTORY OF PARENTERAL NUTRITIONThe use of parenteral nutrition in companion animals is not new. In 1656, a

pigs bladder attached to a goose quill was used to infuse wine into a dogs vein.2

In the 1930s, increased study and awareness of the dangers of malnutrition pro-vided the impetus behind the development of better methods to prevent it. Par-enteral nutrition began to be used in the late 1930s to prevent and treat malnu-trition in humans; however, its regular use in humans did not occur until thelate 1960s, at which time Dudrick and coworkers reported normal growth anddevelopment in dogs fed parenterally.3 The use of parenteral nutrition in dogs

was first reported in the veterinary literature in 1977 in an article on the success-

CE

V

I Abolishing protein catabolism

is impossible in many ill or

traumatized patients, but

nutritional support helps

minimize losses and supports

the patient until recovery.

I Administering PPN is a simpler

method of providing nutritional

support compared with TPN and

usually is associated with fewer

complications.

I Although combination parenteral

products are commercially

available, compounded PPN

formulas are superior because

they provide more balanced

nutrition and can be tailored to

meet individual patients needs.

I Strict adherence to administration,

monitoring, and aseptic technique

protocols in patients receiving

PPN will reduce the risk of

complications.


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ful maintenance of 10 dogs for up to 1 month using to-tal parenteral nutrition (TPN).4 Since that time, theuse of parenteral nutrition in ill animals has expanded.

Initially, parenteral nutrition was provided through alarge central vein (e.g., subclavian vein in humans,

jugular vein in dogs and cats). The risks associated withcentral venous catheters (e.g., sepsis, complications dur-ing placement) may delay initiation of TPN support orprevent its use completely. Therefore, techniques thatsimplify initiation and administration of parenteral nu-trition and reduce the risk of complications make itsuse more feasible. One way of achieving these goals isby administering parenteral nutrition peripherally,

which has become possible because of the developmentof new nutritional products and changing ideas of thegoals of parenteral nutrition.

GOALS OF PARENTERAL NUTRITIONThe goals of parenteral nutrition are no differentthan those of any other type of nutritional supporttoprevent nutritional deficiencies by providing adequateenergy substrates, protein, and micronutrients. Duringthe hypercatabolic state in ill animals, there is accelerat-ed loss of lean body mass; ongoing protein catabolismand wasting of lean body mass cannot be abolished

with nutritional support.5 The goal of nutritional sup-port in these patients, therefore, is to support the pa-tient and minimize ongoing destruction of body tissueuntil the animal recovers. This requires the provision of

adequate calories and protein. It is now accepted thatproviding excessive levels of calories and protein willnot improve a patients condition and is likely to causecomplications.

Another goal of nutritional support is to prevent vita-min and trace-element deficiencies. Currently availablesolutions for parenteral nutrition are designed for hu-mans and do not meet all the amino acid, vitamin, ortrace-element requirements for dogs or cats, promptingsome veterinary nutritionists to avoid the term totalparenteral nutrition. Nonetheless, parenteral nutritionhas successfully supported dogs and cats for months

and is thus usually sufficient for our purposes.

3,4

Par-enteral nutrition solutions that meet the specific re-quirements of our patients, however, will require fur-ther research and development.

Ideas regarding the nutritional requirements of pa-tients have changed over the past decade. Not onlymust basic nutritional requirements be met, but certainnutrients called conditionally essential nutrients (e.g.,the amino acid glutamine) may be required in higherthan normal amounts in ill or traumatized patients. Inaddition, some nutrients may have benefits when pro-vided at concentrations higher than those needed for

known nutritional requirements. This higher concen-tration is meant to improve immunity, diminish thechance of gut-derived sepsis, or hasten wound healing.6

Using nutrients in this manner is known as nutritionalpharmacology. Examples of nutrients that have been

used experimentally include arginine, zinc, and n-3polyunsaturated fatty acids. In the future, our knowl-edge may be sufficiently sophisticated to formulate anutritional protocol not only based on a patients ca-loric, protein, and micronutrient requirements but alsoaimed at modulating the deleterious effects of the dis-ease itself.

INDICATIONSParenteral Nutrition

Nutritional support is indicated in patients that aremalnourished; unlikely to eat for more than 3 days; or

at risk of developing malnutrition because of profound,ongoing protein losses. The enteral route still should bethe first choice for providing nutritional support andshould be used when possible. Enteral feeding is a safer,more economical, and more convenient method of pro-viding nutrition. In addition, providing nutrition by theenteral route has specific benefits to the gastrointestinaltract by preventing mucosal atrophy, maintaining localimmunocompetence, and preserving normal flora.7

Despite these advantages, there are situations inwhich the parenteral route should be chosen. Parenteralnutrition should be selected when enteral nutrition

cannot be tolerated, such as in patients with vomitingor regurgitation, those with severe malabsorption orgastrointestinal obstruction, and potentially in patientsthat cannot protect their airway. Parenteral nutritioncan also be used to supplement enteral feedings in pa-tients that cannot tolerate receiving all nutritional re-quirements enterally. Theoretically, providing even asmall amount of nutrition enterally in conjunction

with parenteral nutrition could help improve patientoutcome by protecting mucosal integrity and minimiz-ing the potential for bacterial translocation and sepsis.

Parenteral nutrition can be provided via a large central

vein or a peripheral vein and can provide either 100% ofrequirements or partial-energy requirements. There iscurrently much controversy regarding the nomenclatureof parenteral nutrition in both the veterinary and humanliterature. We define TPN as a parenteral solution formu-lated to provide 100% of energy requirements and ad-ministered as a hyperosmolar solution via a central vein.Peripheral parenteral nutrition (PPN), sometimes alsocalled partial parenteral nutrition, is defined here as a par-enteral solution formulated to provide 50% of energy re-quirements and administered via a peripheral vein. TPNis a combination of dextrose and amino acids with or

Compendium June 1999 20TH ANNIVERSARY Small Animal/Exotics

T O T A L P A R E N T E R A L N U T R I T I O N I C O N D I T I O N A L L Y E S S E N T I A L N U T R I E N T S I N U T R I T I O N A L P H A R M A C O L O G Y


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without a lipid source, vita-mins, and trace elements.The use of TPN has been re-viewed.810 Because of thetechnical requirements of TPN

administration and potentialcomplications, however, itsuse is not always feasible.Nevertheless, there are manyanimals that can benefit fromparenteral nutrition, and thusPPN may be a practical alter-native.

Peripheral parenteral nu-trition is an option that maybe easier to implement thanis TPN (Figure 1). The for-

mula presented in this article provides a solution with alower osmolarity than that of TPN that can still pro-vide 50% of caloric needs. There are other methods offormulating PPN solutions that allow up to 100% ofcaloric requirements to be met, but calculating and ad-ministering these formulas can be more chal-lenging. The formula for PPN presented inthis article is easy to administer and results infew complications when specified protocols arefollowed, thus requiring less intensive monitor-ing than that required for TPN.

Peripheral Parenteral NutritionPeripheral parenteral nutrition has a numberof advantages over TPN. It should not, howev-er, be viewed as a replacement for TPN but asan alternative that may be appropriate in se-lected patients (see Candidates for PeripheralParenteral Nutrition). Because PPN will notprovide all of an animals energy requirements,it should not be used in patients that are debil-itated (i.e., those that already have signs ofmalnutrition), have large protein losses, or willrequire nutritional support for long periods.

ADVANTAGES AND DISADVANTAGES OFPERIPHERAL PARENTERAL NUTRITION

It is only within the past decade that PPNhas been considered a reasonable route of ad-ministration for parenteral nutrition. Previous-ly, parenteral nutrition was administered onlyvia a large central vein because relatively largevolumes of parenteral nutrition were given tomost patients to meet perceived energy re-quirements. Estimates of energy requirementsare now much more conservative; thus smaller

volumes can be adminis-tered. In addition, solutionsavailable in the past weretoo high in osmolarity to beadministered peripherally. It

was not until the develop-ment of safe fat emulsionsthat PPN became a reality.Fats are a more concentratedenergy source than is glu-cose and reduce the osmo-larity of PPN solutions.11

Providing parenteral nutri-tion via a peripheral catheteroffers several advantages overusing a central catheter (see

Advantages of Peripheral Par-

enteral Nutrition). The first is the ease of peripheralcatheter placement compared with placing jugularcatheters. In many hospitals, technicians do not routinelyplace jugular catheters and TPN is therefore not an op-tion. Another advantage is that PPN is less likely than is

Small Animal/Exotics 20TH ANNIVERSARY Compendium June 1999

I N D I C A T I O N S F O R P P N I E N E R G Y R E Q U I R E M E N T S I F A T E M U L S I O N S

Figure 1In certain patients, parenteral nutrition adminis-tered through a peripheral vein can be an effective and simplealternative to total parenteral nutrition.

I Patients in which the

gastrointestinal tract

cannot be used (e.g.,

due to obstruction,severe malabsorption,

pancreatitis, or risk

of aspiration)

I Nondebilitated patients

I Patients likely to require

only short-term

intravenous nutritional

support (i.e., fewer than 5

to 7 days)

I Patients in which a jugular

catheter cannot be placedI Patients that cannot

tolerate their full nutritional

requirements enterally

(use peripheral parenteral

nutrition to supplement

oral or tube feeding [low-

dose enteral nutrition])

Candidates for Peripheral Parenteral Nutrition

I Easier catheter

placement

I Less likely to cause

metabolic complications

I Less intensive monitoring

is required

I Nutritional support may

be initiated earlier

I Can be as effective as

total parenteral nutrition

in appropriately selected

patients

Advantages of Peripheral Parenteral Nutritiona

aVersus total parenteral nutrition.


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TPN to cause metaboliccomplications because of itslower energy content. Thismeans that clinicians may bemore likely to initiate nutri-

tional support earlier, result-ing in a shorter delay to theonset of therapy. In addition,less intensive monitoring isrequired. Finally, in appropri-ately selected patients, PPNcan be as effective as TPN.Human studies show similarmuscle and respiratory func-tion with TPN and PPN inpostoperative patients.12 Sim-ilarly, nondebilitated dogs

and cats with pancreatitismaintained body weightwhile receiving PPN.13

The primary disadvantageof PPN is the limited num-ber of calories that can beprovided peripherally. Thus,an animal receiving PPNcan still become malnour-ished. If the patients underlying condition does notimprove after 3 to 5 days of PPN, other methods ofnutritional support should be used (i.e., a combina-

tion of enteral nutrition and PPN; TPN if the animalcannot tolerate enteral feeding). Although PPN willhelp to maintain nutritional status, it will not im-prove nutritional status in an already debilitated pa-tient; therefore, its use should be restricted to nonde-bilitated animals.

In humans, thrombophlebitis continues to be the mostcommon problem associated with PPN administration.The incidence of thrombophlebitis in human patientsranges from 2.3% to 70%, depending on the study14; theincidence in dogs and cats has not been reported butanecdotally appears to be lower than that in humans.

Nonetheless, many factors increase the risk of throm-bophlebitis, including properties of the veins, catheter,and solution as well as infusion rates, all of which mustbe considered to maintain a low incidence of this prob-lem (see Reducing Thrombophlebitis Risk in PatientsReceiving Peripheral Parenteral Nutrition1416).

PERIPHERAL PARENTERAL NUTRITIONSOLUTION CHOICESSingle Agents

Although single agents are available and have beenused clinically by veterinarians, they do not provide bal-

anced nutrition and are prob-lematic when used alone (e.g.,50% dextrose is too hyperos-molar and 5% dextrose istoo low in calories to be ben-

eficial when administeredalone via a peripheral vein;Table I). For example, ad-ministering 5% dextrose to a25-lb dog at a maintenancefluid rate would provide only128 kcal (less than 25% ofenergy requirements and noprotein). Administering lipidas a single agent can suppressthe immune system and, likedextrose, provides no pro-

tein. The osmolarity of aminoacids (Table I) makes this so-lution too irritating to thevascular endothelium to beadministered peripherally,and amino acids are not abalanced or efficient meansof providing calories. Thus,the use of these agents indi-

vidually as a means of nutritional support should beavoided.

Commercial Combination ProductsUntil recently, there were no commercially availabledextroseamino acid solutions because such solutions

were difficult to sterilize. When heat-sterilized together,amino acids and dextrose undergo the Maillard brown-ing reaction, which adversely affects the quality of theindividual ingredients. Thus, manufacturers had to de-vise alternate methods for this process.

There are two approaches to this problem. Dextroseand amino acids can be sterilized in a dual-chamberbag in which the two components are connected butseparated (Figure 2). Just before administration, the seal

between the two compartments is broken by squeezingthe bag and the solutions are mixed. Products that usethis approach are Clinimix and Quick Mix (bothmanufactured by Clintec Nutrition Co., Deerfield, IL;Table I). In another product (ProcalAmine; McGaw,Inc., Irvine, CA), glycerin or glycerol, which can safelybe sterilized with amino acids, is used as a caloriesource. Glycerol can be a substrate for glycolysis and isthus an effective substitute for glucose. In addition, lessexogenous insulin is required in humans to maintainglucose homeostasis with a glycerol-containing solutioncompared with an isocaloric, isonitrogenous dextrose


T H R O M B O P H L E B I T I S I D E X T R O S E A M I N O A C I D S O L U T I O N S I G L Y C E R O L

I Use the largest vein and smallest catheter

possible.

I Use a catheter material of the lowest

thrombogenicity (polyurethane or silicone is

ideal; tetrafluoroethylene is acceptable; avoid

polyvinyl chloride and polyethylene).

I Keep the osmolarity of the solution below 750

mOsm/L.

I Use three-in-one solutions containing lipid to

reduce osmolarity.

I Keep the pH of the solution neutral.

I Administer PPN through a 1.2-m inline filter.I Follow protocols for compounding and

administering solutions and monitoring patients

receiving PPN.

I At the first signs of thrombophlebitis, remove the

catheter and place a new one at a different site.

Reducing Thrombophlebitis Risk inPatients Receiving PeripheralParenteral Nutrition (PPN)1416


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amino acid combination.17 The number of calories pro-vided is less than that in the dextroseamino acid prod-ucts (Table I).

The major advantages of using these products aretheir commercial availability and the fact that no prepa-ration is required. This makes them useful in clinicsthat are not yet equipped to mix PPN solutions. These

products vary in their osmolarity, protein content,caloric density, pH, and electrolyte concentration(Table I), and thus it is important to determine whichis most appropriate for an individual patient. Potassiumcontent in these products ranges from 24 to 30 mEq/L;therefore, additional potassium supplementation is usu-ally not required unless a patient is severely hy-pokalemic. Additional sodium and chloride supple-mentation may be required if ongoing losses orpreexisting imbalances are present. It also is importantto realize that the amino acid profiles are designed forhumans and do not necessarily meet canine or feline re-

quirements. We currently administer these products ata maintenance fluid rate (cats, 50 ml/kg/day; dogs, 66ml/kg/day) by continuous-rate infusion unless this rateis contraindicated (e.g., in cardiac disease). At this rate,these products provide the majority of protein require-ments (dogs, 100%; cats, 50% to 60%) but only 20%to 40% of an animals energy requirements and should

be used only in nondebilitated patients.Benefits of these commercial solutions are attributedto the concept of protein-sparing, which is the ideathat administering the products will decrease the use ofendogenous protein. In some studies, using combina-tion products improved nitrogen balance compared

with amino acids or dextrose alone, although the bene-fits of protein-sparing are still controversial.18 Some ad-vocate the use of lipid solutions in conjunction withthese commercial products to supplement caloric intake.Lipids can be administered through a Y-type adminis-tration set, although this increases the risk of sepsis.


S O D I U M A N D C H L O R I D E S U P P L E M E N T A T I O N I A M I N O A C I D P R O F I L E S I P R O T E I N - S P A R I N G

TABLE I

Commercially Available Components Versus Combination Solutions for Peripheral Parenteral Nutritiona

Trade Osmolarity Na+ Cl+ K+ Mg++ Ca++ PO4 Calories (kcal/L)

Name (mOsm/L) pH (mEq/L) (mEq/L) (mEq/L) (mEq/L) (mmol/L) (kcal/L) Nonprotein Protein

Components5% dextrose 252 4.0 - 170

10% dextrose 505 4.0 340

50% dextrose 2525 4.2 1700

8.5% amino acids Travasol 890 6.0 34 340

8.5% amino acids Travasol 1144 6.0 70 70 60 10 30 340with electrolytes

20% lipid Intralipid

260 8.0 15 2000

10% lipid Intralipid 260 8.0 15 1000

Combination Products2.75% amino Clinimix 665 6.0 35 39 30 5 4.5 15 170 110acids/5% dextroseb (2 L)

2.75% amino Quick Mix 670 6.0 35 35 30 5 15 170 110acids/5% dextroseb (1 L)

3% amino acids/3% ProcalAmine 735 6.8 35 41 24 5 3 3.5 130 116glycerin (1 L)

aRepresentative products are listed; see text for manufacturer information. Similar available products may have different properties.bProducts without electrolytes are also available.Ca= calcium; Cl= chloride; K= potassium; Mg= magnesium; Na= sodium; PO4 = phosphate.


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Most animals tolerate the adminis-tration of combination products well,although some with moderate to severehepatic or renal failure may not toleratetheir administration at the usual rate;

these animals may require more cau-tious administration or different nutri-tional support techniques. Care shouldbe taken when administering these so-lutions to cardiac patients because oftheir sodium content and the potentialfor fluid overload. Thrombophlebitiscan occur because of the relatively highosmolarity. Although these commercialproducts are superior to any singleagent for nutritional support, they arenot a replacement for other types of

parenteral nutrition and are used onlyfor interim support in our hospital.

Three-in-One FormulaThe preferred method for supplying

PPN is to compound a mixture specif-ically tailored to the patients individu-al needs using amino acids, dextrose,and lipid. The formulation should have an osmolaritythat is less than 750 mOsm/L.

Amino Acids

A variety of amino acid solutions are available, in-cluding standard preparations and specialized solu-tions designed for humans with various diseases (e.g.,formulas for hepatic or renal disease). The safety andefficacy of these specialized solutions have not beentested in dogs or cats, and their cost usually makesthem unrealistic for veterinary use. Therefore, this ar-ticle discusses only standard amino acid preparations.The most commonly used amino acid preparation(Travasol; Clintec Nutrition Co.) consists of 8.5%amino acids in sterile water and provides 340 kcal/Land essential amino acids for humans (Table I).

Amino acids are available with or without elec-trolytes, and the appropriate selection depends on thestatus of the individual patient. All compoundedPPN solutions should contain amino acids as a pro-tein source.

DextroseDextrose is used as a caloric source for PPN. Three

preparations (50%, 10%, and 5%) are available, butonly the 5% or 10% preparations should be used forperipheral administration because of their osmolarity(see Table I for comparison).

LipidsAlthough dextrose and amino acid

solutions supply readily usable sourcesof calories and protein, respectively,they have the disadvantage of signifi-

cantly increasing the tonicity of the so-lution as their concentrations rise andare thus more thrombogenic. ProvidingPPN with only dextrose and aminoacids therefore carries a high risk ofthrombophlebitis (if 50% dextrose isused) or provides negligible calories (if5% or 10% dextrose is used). Thus, it

was only after safe lipid emulsions weredeveloped for commercial use thatPPN became practical.

Lipids are an ideal nonprotein calo-

rie source because of their much high-er energy content (9 kcal/g for lipidscompared with 4 kcal/g for protein orcarbohydrate), low osmolarity, andneutral pH. Intralipid(Clintec Nutri-tion Co.) is currently the most com-monly used lipid source in the UnitedStates. It is available in a 10% or 20%

solution (Table I); a maximum infusion rate of 2g/kg/day should be observed. Intralipid contains fatfrom soybean oil and egg yolk phospholipid in combi-nation with glycerol to create an isotonic solution. Us-

ing lipids in compounded PPN solutions allows theformulation of peripheral solutions that provide a rea-sonable number of calories without increasing the riskof thrombophlebitis.11 The diminished incidence ofthrombophlebitis in humans who are given lipid-con-taining solutions may also be attributed to a coatingeffect of lipid emulsions.19

Several precautions must be undertaken when usinglipid solutions. Because lipid solutions may react withother PPN ingredients, careful observation for discol-oration or precipitation during mixing is necessary. Inaddition, fat precipitates can form and cause fat em-

bolization in animals. Side effects to lipid solutions arerare, but chills, fever, and headaches occasionally occurin humans.11Anecdotal reports in dogs and cats suggestthat allergic reactions, such as rashes, can develop fromrepeated lipid infusion. Propofol has the same base aslipid solutions; thus allergic reactions could theoretical-ly develop in animals that have received propofol. Highdosages or rapid infusion of lipid solutions suppress thereticuloendothelial system and can therefore impair im-mune function.20 Finally, lipid solutions are normallyquickly cleared from the serum, but patients with cer-tain diseases (e.g., hypothyroidism, idiopathic hyper-


P R O T E I N S O U R C E I C A L O R I C S O U R C E I L I P I D P R E C A U T I O N S

Figure 2One type of commerciallyavailable combination product for pe-ripheral parenteral nutrition adminis-tration combines dextrose and aminoacids in a dual-chamber bag.


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lipidemia, pancreatitis) have abnormalities in lipidclearance and may not tolerate the use of lipid inPPN.11 Lipids should not be used in animals with pre-existing hypertriglyceridemia or should at least be usedat reduced concentrations and with caution.

Vitamins and Trace MineralsIn our hospital, vitamins are routinely added to com-

pounded PPN solutions. Although there has been a na-tionwide shortage of parenteral vitamins for both humansand companion animals, one company currently has anavailable parenteral multivitamin preparation (Cernevit;Clintec Nutrition Co.) that contains vitamins A, D, E, C,and B; biotin; and folate. Our hospital uses a dose of 0.5ml reconstituted product/5 kg body weight (maximum, 5ml/animal). An alternative is to use a standard parenteralB-vitamin complex solution for animals (2 ml/L of PPN).

Trace elements (zinc, copper, manganese, and chromium)can also be administered, although we consider these tobe optional in most patients receiving PPN because theyshould already be well nourished. When used, trace ele-ments (Abbott Laboratories, North Chicago, IL) are ad-ministered at a dose of 0.5 ml/5 kg body weight (maxi-mum, 5 ml/animal).

CALCULATING REQUIREMENTS AND APERIPHERAL PARENTERAL NUTRITION FORMULA

In our hospital, commercial PPN solutions are usedas an interim means of nutritional support (i.e., for 1 to

2 days) and are administered at a maintenance fluidrate (cats, 50 ml/kg/day; dogs, 66 ml/kg/day). Veteri-nary nutritionists use a variety of methods for formu-lating three-in-one PPN, and each has its advantagesand disadvantages. This article presents the techniqueused in our hospital (see Worksheet for CalculatingThree-in-One Compounded Peripheral Parenteral Nu-trition), although it is important to note that this is notthe only method possible and that it provides only 50%of energy requirements (plus 100% and 50% to 60%of protein requirements in dogs and cats, respectively).The method is designed to approximate a maintenance

fluid rate and has been used successfully in more than200 dogs and cats in our hospital.First, the animals energy requirements are calculated.

The resting energy requirement (RER) is the numberof calories required for maintaining homeostasis whilean animal sits quietly. The most accurate formula forcalculating RER is:

RER = 70 Body weight0.75 (kg)

For animals that weigh between 2 and 35 kg, the fol-lowing linear formula gives a good approximation ofenergy needs:

RER = 30 Body weight (kg) + 70

The second step for determining energy requirementsis to calculate the illness energy requirement (IER),

which is an estimate of the number of calories neededto sustain an ill or injured patient. This is calculated by

multiplying the RER by an illness factor, which is asubjective assessment of a patients needs above thoserequired for RER. Illness factors for dogs and cats havebeen extrapolated from research in human patients andare selected based on activity level and underlying dis-ease.10 Until recently, illness factors as high as 2.0 wereused in human and veterinary patients to calculate IER,but these values were too high and often led to over-feeding. Current recommendations in both humansand animals are therefore more conservative, and illnessfactors lower than 1.5 should be used for nearly all pa-tients. Therefore, the IER is calculated as follows:

IER = RER Illness factor (i.e., 1.0 to 1.5)

Next, the partial energy requirement (PER) is calcu-lated. Because only 50% of the animals IER can beprovided by three-in-one PPN, the IER is multipliedby 50%. Depending on the size of the animal, differentpercentages of the PER are supplied by dextrose, aminoacids, and lipid. These are standard formulas, and per-centages may need to be adjusted depending on the an-imals underlying disease. For example, if the animalhas preexisting hypertriglyceridemia, reduction or elim-ination of the lipid is necessary.

Commercial parenteral multivitamins for humans areroutinely added to PPN in our hospital, although astandard parenteral B-vitamin complex can also beused. Trace elements also can be administered if de-sired. Vitamin K is administered subcutaneously onceon day 1 of PPN and then once weekly. If amino acids

with electrolytes are used, this formulation will approx-imate maintenance amounts of potassium. Additionalpotassium supplementation may be required if hy-pokalemia is present.21 Other supplements, includingdrugs, may or may not be compatible with the PPN.Check with the manufacturer of the supplement before

adding anything to the PPN. Any additives should beintroduced in a sterile fashion at the time of mixing.

SOURCES OF PERIPHERAL PARENTERALNUTRITION COMPOUNDING

Some clinics have the facilities and technical staff tocompound their own PPN. This requires a clean area,adequate supplies, and trained personnel. Commercialsets are available for compounding PPN (i.e., sterile bags

with three-lead transfer sets [All-in-One Containers;Clintec Nutrition Co.]; Figure 3) that can be connected


R E S T I N G E N E R G Y R E Q U I R E M E N T I I L L N E S S E N E R G Y R E Q U I R E M E N T I P A R T I A L E N E R G Y R E Q U I R E M E N T


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Resting Energy Requirement (RER)RER (kcal/day) = 70 Body weight0.75 (kg)

or, for animals weighing between 2 and 35 kg:

RER = 30 Body weight (kg) + 70 = kcal/day RER = _____ kcal/day

Illness Energy Requirement (IER)IER = RER Illness factor IER = _____ kcal/day

Partial Energy Requirement (PER)To supply 50% of the animals IERPER = IER 0.50 PER = _____ kcal/day

Nutrient Requirements(Note: This will supply fluids at greater than maintenance rate for animals


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C O M P O U N D I N G P P N I I N L I N E F I L T E R S I B A G S A N D C A T H E T E R S

to dextrose, amino acids, and lipidfor transfer to a special mixing bag.

After mixing, the bag is clamped offand the solution is administered tothe animal.

For many clinics, however, com-pounding PPN in-house is not feasi-ble. In this situation, there are now anumber of alternatives. Many phar-macies in human hospitals are willingto make arrangements with veterinar-ians to compound PPN. Typically,they require the calculations to bemade by the veterinarian, and eitherone or several days worth of PPN iscompounded (it is often more costefficient to make enough for several

days at a time). Alternatively, someuniversities and referral veterinaryclinics will compound PPN and shipit to veterinarians. The advent of hu-man home health care in many citieshas recently expanded the availabilityof TPN and PPN for veterinarians.Many home health care companiescompound and deliver TPN to hu-man patients on a daily basis and are

willing to make arrangements withveterinarians for this service. Using

the method of calculation describedin this article, PPN can now be avail-able to most veterinary clinics.

PERIPHERAL PARENTERALNUTRITION ADMINISTRATION

Regardless of the type of PPNchosen, there are certain rules of ad-ministration that apply. Dehydratedpatients should be rehydrated be-fore commencing PPN administra-tion. Ongoing fluid losses should be

corrected with concurrent adminis-tration of a crystalloid fluid. Thus ifongoing fluid losses are miscalculat-ed or change daily, adjustments tothe crystalloid fluid therapy can beperformed without altering the PPNsolution or rate of administration. The PPN solutionitself is calculated to approximate maintenance fluid re-quirements. Ideally, PPN should be administered over24 hours as opposed to cyclically. In certain conditions,such as a hospital without 24-hour care, it may be ac-ceptable to administer PPN over 12 hours, but this is

more likely to result in metaboliccomplications (see Complicationsand Monitoring section).

Using the calculations in this arti-cle, PPN can be started at the full cal-

culated rate (i.e., there is no need togradually increase the PPN rate). Bagsof PPN should be refrigerated untilused and hung at room temperaturefor no longer than 24 hours. A bag ofPPN should not be administered tomore than one animal. An animalstolerance of oral feeding and its con-dition should be assessed daily. If theanimals condition does not start toresolve after 3 to 5 days of PPN ad-ministration, either TPN or PPN

combined with enteral nutrition shouldbe considered. When the animal isable to acquire at least half of its ener-gy requirements orally, PPN can bediscontinued (tapering PPN is not re-quired).

Inline filters (1.2 m) should al-ways be used as part of the admin-istration set to filter particulate mat-ter from the solution and to preventair from entering the vascular sys-tem. Solutions should be adminis-

tered with an infusion pump toavoid giving a bolus of the PPN so-lution. A nonthrombogenic cathetershould be placed; we use 8- to 12-inch, 19- to 22-gauge, tetrafluo-roethylene Intracath catheters(Becton Dickinson, Sandy, UT).Maintaining the sterility of PPNsolutions, lines, and catheters is ab-solutely critical to prevent sepsisbecause the solution is an idealgrowth medium for bacteria.

The patients PPN cathetershould be a dedicated line andshould therefore not be used to ad-minister medications or additionalfluids, take blood samples, or mea-sure central venous pressure. The

line should not be disconnected, except to change PPNbags. When the bag is empty (which should occur every24 hours), the bag, line, and catheter bandage should bechanged. Sterile technique should be used when han-dling the catheter or the line and when changing bags(Figure 4). The catheter site should be evaluated for

Figure 3A sterile bag with a three-leadtransfer set allows veterinary clinics to com-pound a three-in-one peripheral parenteralnutrition in a sterile fashion.

Figure 4Catheters and lines used for pe-ripheral parenteral nutrition administrationmust be handled aseptically to reduce therisk of infection.


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signs of swelling, redness, or irritation. If there is irrita-tion at the site or any question of the catheters patency,the catheter should be removed and a new one placed ina different vein. The catheter should be carefullyrewrapped. The bandage also should be changed if it be-

comes soiled with urine, feces, or vomit.

COMPLICATIONS AND MONITORINGAlthough complications are much less common with

PPN than with TPN, patient monitoring is still one ofthe most important aspects of providing nutritionalsupport. Potential complications can be mechanical,

metabolic, or septic.The most common com-

plications of PPN are me-chanical, including catheterocclusion or premature re-

moval, line disconnectionor breakage, and throm-bophlebitis. Catheter andline problems can be mini-mized by careful attentionto catheter care and moni-toring of animals (e.g., us-ing an Elizabethan collar toprevent animals from chew-ing the line or catheter).Thrombophlebitis is not anindication for termination

of therapy but does requirerelocation of the catheter.Metabolic complications

are much less commonwith PPN formulated usingthe calculations in this arti-cle than with TPN. Themost common problem ishyperglycemia, which, if se-vere, can be managed withexogenous insulin. Hyper-ammonemia or hypertrigly-

ceridemia are uncommonbut can occur and usuallyrequire reformulation of thesolution with reduced pro-tein or reduced lipid levels,respectively. Refeeding syn-drome (characterized byhypokalemia, hypophos-phatemia, and hypomag-nesemia) also can occur butis unlikely. Another possibleproblem is congestive heart

failure resulting from volume overload, especially whenintravenous fluids are given in addition to the PPN.Metabolic complications are not always the direct resultof the PPN but may be caused by the underlying disease.

Septic complications are the most serious potential

problem of PPN but can be minimized by adhering tostrict protocols for mixing and handling solutions andmonitoring animals. If fever or other signs of potentialsepsis occur and other causes (e.g., peritonitis, urinarytract infection, pneumonia) are ruled out, cultures ofthe blood and PPN catheter should be performed.

The complication rate is quite low, however, if strictprotocols for mixing and administering PPN are ob-served. In a study conducted in our hospital of dogs andcats with pancreatitis receiving three-in-one compound-ed PPN, the only complications noted were metabolic(e.g., hyperammonemia, hypercholesterolemia, and hy-

pertriglyceridemia) in 1 of 12 patients.

13

No cases ofthrombophlebitis or sepsis occurred.13 In a recently com-pleted study of dogs and cats receiving a commercialPPN solution, 2 of 30 patients developed transient mildhyperglycemia and 2 developed phlebitis; sepsis was notnoted.22

Other important parameters to monitor includebody weight and signs of malnutrition. PPN is intend-ed for animals that are not already debilitated, do nothave large protein losses, and are expected to eat within4 to 5 days. If the situation changes (e.g., the animalhas increased vomiting or diarrhea or significant

drainage from wounds or the condition persists formore than few days) or the animal begins to exhibit weight loss or decreasing serum albumin concentra-tions, it is important to change to TPN or a combina-tion of PPN and low-dose enteral nutrition.

SUMMARYMany of the problems associated with TPN can be

overcome by using PPN, but PPN should not beviewed as a replacement for TPN. Although it does notprovide all nutritional requirements, PPN can be bene-ficial in appropriately selected patients. In addition,

PPN reduces the risk of complications compared withTPN. Like TPN, however, PPN does have potential tocause major problems and thus should be administered

with care; protocols for mixing and administering solu-tions as well as monitoring patients should be devisedand strictly followed. The ease of use of PPN has madethe benefits of parenteral nutrition more widely avail-able to veterinarians and their patients.

REFERENCES1. Thatcher CD: Nutritional needs of critically ill patients.

Compend Contin Educ Pract Vet18(12):13031313, 1996.


M E C H A N I C A L C O M P L I C A T I O N S I H Y P E R G L Y C E M I A I S E P T I C C O M P L I C A T I O N S

The importance of providing

nutrition to ill veterinary

patients has become increasingly

clear over the past two decades,

and nutritional support is now

commonplace. Although total

parenteral nutrition is now

more widely accepted, safer,

and easier than it once was, itsuse is still not feasible for many

practices. Advances in the

formulation of parenteral

nutrition solutions, intravenous

catheters, and administration

techniques as well as more

conservative calculation of

nutritional requirements have

facilitated the use of peripheral

parenteral nutrition (PPN).

Simplified administration andfewer complications make PPN

a convenient and practical

method of nutritional support

in carefully selected patients.

A LookBack

COMP

ENDIUMS

20thANNIVERSARY

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- 1 99 9


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17:468478, 1993.15. Kane KF, Cologiovanni L, McKiernan J, et al: High osmo-

lality feedings do not increase the incidence of throm-bophlebitis during peripheral IV nutrition.J Parenter Enter-al Nutr20:194197, 1996.

16. Bodoky A: Parenteral nutrition by peripheral vein, portalvein, or central venous catheter? World J Surg 10:4752,1986.

17. Lev-Ran A, Johnson M, Hwang DL, et al: Double-blindstudy of glycerol vs glucose in parenteral nutrition of post-surgical insulin-treated diabetic patients. J Parenter EnteralNutr11:271274, 1987.

18. Fairfull-Smith R, Stoski D, Freeman JB: Use of glycerol inperipheral parenteral nutrition. Surgery92:728732, 1982.

19. Kehoe JE, Mihranian MH, Masser EL, et al: Use of 20% fatemulsion in peripheral parenteral nutrition.J Parenter Enter-al Nutr8:647651, 1984.

20. Carpentier YA, Van Gossum A, Dubois DY, DeckelbaumRJ: Lipid metabolism in parenteral nutrition, in Rombeau

JL, Caldwell MD (eds): Clinical Nutrition: Parenteral Nutri-tion, ed 2. Philadelphia, WB Saunders Co, 1993, pp 3574.

21. Dibartola SP, Autran de Morais HS: Disorders of potassium:Hypokalemia and hyperkalemia, in DiBartola SP (ed): FluidTherapy in Small Animal Practice. Philadelphia, WB Saun-ders Co, 1992, pp 89115.

22. Freeman LM, Rush JE, Rozanski EA, et al: Nutritional sup-port using a commercial glycerin/amino acid solution. ProcInt Vet Emer Crit Care Soc Meet:827, 1998.

About the AuthorsDrs. Zsombor-Murray and Freeman are affiliated with the

Department of Clinical Sciences, School of Veterinary

Medicine, Tufts University, North Grafton, Massachusetts.

Dr. Freeman is a Diplomate of the American College of

Veterinary Nutrition.

2. Rhoads JE, Dudrick ST: History of intravenous nutrition, inRombeau JL, Caldwell MD (eds): Clinical Nutrition: Par-enteral Nutrition, ed 2. Philadelphia, WB Saunders Co,1993, pp 110.

3. Dudrick ST, Wilmore DW, Vars HM, Rhoads JL: Long-term total parenteral nutrition with growth, development,and positive nitrogen balance. Surgery64:134142, 1968.

4. Carter JM, Freedman A: Total intravenous feeding in thedog.JAVMA171:7176, 1977.

5. Nordenstrom J: Peripheral parenteral nutrition: Changingtrends in intravenous feeding. Nutrition8:440441, 1992.

6. Barton RG: Immune-enhancing enteral formulas: Are theybeneficial in critically ill patients? Nutr Clin Pract12:5162,1987.

7. Mainous MR, Block EFJ, Deitch EA: Nutritional support ofthe gut: How and why. New Horizons2:193201, 1994.

8. Davenport DJ: Enteral and parenteral nutritional support, inEttinger SJ, Feldman EC (eds): Textbook of Veterinary Inter-nal Medicine, ed 4. Philadelphia, WB Saunders Co, 1995,pp 244252.

9. Lippert AC, Armstrong PJ: Parenteral nutritional support, in

Kirk RW (ed): Current Veterinary Therapy X: Small AnimalPractice. Philadelphia, WB Saunders Co, 1989, pp 2530.10. Remillard RL, Thatcher CD: Parenteral nutritional support

in small animal patients. Vet Clin North Am Small AnimPract19:12871306, 1989.

11. Dickerson RN, Brown RO, White KG: Parenteral nutritionsolutions, in Rombeau JL, Caldwell MD (eds): Clinical Nu-trition: Parenteral Nutrition, ed 2. Philadelphia, WB Saun-ders Co, 1993, pp 310333.

12. Stokes MA, Hill GL: Peripheral parenteral nutrition: A pre-liminary report on its efficacy and safety. J Parenter EnteralNutr17:145147, 1993.

13. Freeman LM, Labato MA, Rush JE, Murtaugh RJ: A retro-spective evaluation of peripheral parenteral nutrition (PPN)in small animal patients with pancreatitis. Proc Int Vet EmerCrit Care Soc Meet:881, 1996.

14. Payne-James JJ, Khawaja HT: First choice for total parenter-al nutrition: The peripheral route. J Parenter Enteral Nutr


peripheral parental nutrition

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