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The Hitchhiker’s Guide to
Parenteral Nutrition Management
for Adult Patients
INTRODUCTION
F
eeding nutritionally compromised patients has
never been as easy, or as hard, as it is today. We
are able to provide nutrients parenterally and
enterally to patients who once would have been con-
sidered “unfeedable.” Today’s inpatient population is
sicker than patients in the past; the same may be said
for patients needing specialized nutrition support. This
results in challenges to clinicians caring for these
patients. Our goal in writing this article is to provide a
succinct and easy to follow guide for practicing clini-
cians ordering parenteral nutrition.
INDICATIONS
The guiding principle of nutrition support is to use the
least invasive and most physiologic method of feeding.
Infusing chemicals directly into the bloodstream is the
least preferred method of providing nutrition support
(1). Yet, for a select subset of the population, intra-
venous infusion of central parenteral nutrition (PN) or
peripheral parenteral nutrition (PPN) is the only viable
means to provide substrates for metabolism. PN carries
with it inherent risks associated with the placement of a
central venous catheter. Due to the increased risk of
complications with PN therapy, including thrombosis
and infection, a careful assessment of PN appropriate-
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
Howard Madsen, RD, Pharm.D., Nutrition Support
Pharmacy Practice Resident and Eric H. Frankel,
MSE, Pharm.D., BCNSP, Nutrition Support Coordina-
tor, Covenant Health System, Lubbock, Texas.
Carol Rees Parrish, R.D., M.S., Series Editor
While parenteral nutrition is a life-saving modality for people with intestinal failure, it
is not without significant risk. In the hospital setting, under certain clinical circum-
stances, patients will also benefit from the use of parenteral nutrition. The purpose of
this article is to aid the clinician in the safe provision of parenteral nutrition support,
including development of the prescription, appropriate monitoring, and awareness of
the issues involved in the preparation and stability of commonly used additives.
Frequently asked questions and challenges that arise with the use of parenteral nutri-
tion are also addressed.
Howard Madsen Eric H. Frankel
ness should precede placement of a central venous
catheter (1,2). Table 1 lists indications and contraindi-
cations for PN.
PATIENT ASSESSMENT
Prior to initiating PN, a nutrition assessment is neces-
sary to determine nutrient needs and to anticipate any
metabolic changes that may occur due to the patient’s
underlying condition, medications or concurrent thera-
pies, etc. Table 2 provides a list of factors to consider
when assessing a patient’s nutritional status. Deter-
mining energy and protein needs in the severely mal-
nourished patient under physical stress, often ventila-
tor-dependent with little mobility, can be difficult.
Critical illness brings further challenges in determin-
ing the appropriate calorie level, as matching caloric
expenditure to caloric provision may be detrimental—
providing lower calorie levels initially has been advo-
cated (3,4). Calorie requirements often increase in
relation to stress, fever, and seizures, while a decrease
in needs may be seen in the setting of sedation or
reduced mobility. While indirect calorimetry is consid-
ered the “gold standard” to determine caloric expendi-
ture, formulas and calculations are frequently used.
Unfortunately, no studies to date have demonstrated
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
Table 1 Indications, Relative Indications and Contraindications for Parenteral Nutrition
Parenteral nutrition is usually indicated in the following situations
- Documented inability to absorb adequate nutrients via the GI tract such as: - Massive small-bowel resection/short bowel syndrome (at least initially) - Radiation enteritis - Severe diarrhea - Untreatable steatorrhea/malabsorption (i.e., not pancre- atic insufficiency, small bowel bacterial overgrowth, or celiac disease)
- Complete bowel obstruction, or intestinal pseudo-obstruction
- Severe catabolism with or without malnutrition when GI tract is not usable within 5–7 days
- Inability to obtain enteral access
- Inability to provide sufficient nutrients/fluids enterally
- Pancreatitis accompanied by abdominal pain with jejunal delivery of nutrients
- Persistent GI hemorrhage
- Acute abdomen/ileus
- Lengthy GI work-up requiring NPO status for several days in a malnourished patient
- High output enterocutaneous fistula (>500 mL) and inability to gain enteral access distal to the fistula site
- Trauma requiring repeat surgical procedures
Parenteral nutrition maybe indicated in the following situations
- Enterocutaneous fistula
- Inflammatory bowel disease not responding to medical therapy
- Hyperemesis gravidarum when nausea and vomiting persist longer than 5–7 days and enteral nutrition is not possible
- Partial small bowel obstruction
- Intensive chemotherapy/severe mucositis
- Major surgery/stress when enteral nutrition not expected to resume within 7–10 days
- Intractable vomiting when jejunal feeding is not possible
- Chylous ascites or chylothorax when low fat/fat free EN does not adequately decrease output
Contraindications for Parenteral Nutrition
- Functioning gastrointestinal tract
- Treatment anticipated for less than 5 days in patients without severe malnutrition
- Inability to obtain venous access
- A prognosis that does not warrant aggressive nutrition support
- When the risks of PN are judged to exceed the potential benefits
Used with permission from the University of Virginia Health System Nutrition Support Traineeship Syllabus (Parrish CR, Krenitsky J, McCray S). Parenteral Module. University of Virginia Health System Nutrition Support Traineeship Syllabus, 2003.
Table 2 Important Factors to Consider when Assessing a Patient for Parenteral Nutrition
- Anthropometric Data – include:
- Recent weight changes
- Current height and weight
- Lab values – including:
- Comprehensive metabolic panel
- Serum magnesium level
- Serum phosphorus level
- Serum triglycerides as indicated (Table 18)
- Medical/Surgical History
- Anatomy (resections)/ostomies
- Pre-existing conditions such as diabetes, renal failure, liver disease, etc.
- Diet/Medication History – include:
- Food/drug allergies
- Diet intake prior to admission
- Special diets
- Herbal/supplement use
- Home and current medications
Table 4 Review of Access Devices Used for Nutritional Support (10–13)
Line Type Advantages Disadvantages Peripheral Lines Peripheral – Short • Least expensive • Loss of line is common. High levels of phlebitis
- Easily placed and removed and vein damage with nutrition support
- Lowest risk for catheter related infections • Kcals usually limited due to volume restriction
- Beneficial for patients needing short term • Limited to one lumen nutrition support (<1 week) • Limits infusion osmolality to 600–900 mOsm/L and
- Need to change frequently (48–72 hours) infusion pH between 5 and 9 (lower limit of mOsm represents INS standards)
Peripheral – Midline • May be used for a longer duration than peripheral • Must maintain guidelines for peripheral lines when catheters looking at concentration and pH
- Ease of placement compared to central lines • Not a central line
- Allows access to larger vessel
Central Lines Peripherally Inserted • Able to infuse solutions >900 mOsm/L • Not as long term as other centrally placed catheters— Central Catheters or • May be placed by trained RN length of stay ~ a year (PICC) lines • Decreased rate of infection when compared to other • More difficult self care if located in anticubital central lines in home care patients position (should not be painful)
- Able to place lines with multiple lumens • Blood sampling not always possible
- Many PICC lines can be used for CT contrast injection • More frequent flushing and maintenance required
Hickman ®, and • Able to give solutions >900 mOsm/L • Surgical procedure, more difficult to place involving Broviac®^ • Provide full nutritional support via IV route increased cost and monitoring as well as risk to
- Able to place lines with multiple lumens patient. Adds additional time and complexity in
- Able to remain in place for extended time periods placement (1–3 years usual) • Removal also more involved than PICC removal, due to tunnel
- Catheter protruding from chest may affect some people’s self image
Groshong ®^ Catheters • Able to give solutions >900 mOsm/L • Surgical procedure, more difficult to place involving
- Provide full nutritional support via IV route increased cost and monitoring and risk to patient
- Able to place lines with multiple lumens. • Adds additional time and complexity in placement
- Able to remain in place for extended time periods • Removal also more involved than PICC removal,
- May be “locked” with normal saline due to tunnel
- Catheter protruding from chest may affect some people’s self image
Femoral Lines • Gives IV access to patients with no other option • Increased infection risk
Multiple Lumen acute • Economical, can be removed by trained RN • Increased infection rate compared to single lumen care catheters • May be placed at bedside or in radiology by a and tunneled catheters. Usually not repairable physician if damaged
- Should not be used in home care, for acute care only
- Short dwell time, 1–2 weeks
Port • Long term use with lowest infection risk of all • Placement and removal are surgical procedures options (dwell time may be years) performed in the operating room or interventional
- Site care only when accessed suite
- Body image intact • Requires “stick” to access port with Huber needle.
- Ideal for intermittent access If needle is in place, risk of infection increases
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
(continued from page 48)
nutrition are candidates for central PN.
Several conveniently packaged, “fixed concentra-
tion” PPN products are available commercially and are
suitable for peripheral administration. These formula-
tions contain dextrose ranging from final concentra-
tions of 5%–10% or 3% glycerol in addition to amino
acids in final concentrations of 3% to 4.25%. Some of
these products are available with or without a standard
amount of electrolytes. PPN formulations can also be
compounded on an individual basis (customized)
allowing the flexibility to add intravenous fat emul-
sions (IVFE) or manipulate electrolytes. IVFE are not
included in commercial premixed formulations, but
10% or 20% concentrations of IVFE may be given as
a piggyback. All IVFE are isotonic and lower the over-
all osmolarity of the infusate. Some clinicians will pro-
vide up to 60% of the total caloric requirements as
lipid, while others limit the lipid to less than 1
gm/kg/day due to the possibility of altered immune
function associated with infusion of long chain triglyc-
erides (19). Patients on IVFE should be monitored for
Fat Overload Syndrome; a syndrome characterized by
hypertriglyceridemia, fever, clotting disorders, hepato-
splenomegaly, and variable end organ dysfunction.
This syndrome has been reported in the setting of
excessive IVFE administration to children and criti-
cally ill adult patients (20,21). This is particularly
important in the critical care setting where the seda-
tive, propofol (Diprivan ©^ and two generic versions), a
medication in a 10% IVFE base, is frequently used.
CENTRAL NUTRITIONAL SUPPORT
Central venous catheters provide temporary or long-
term access to large diameter veins with blood flows in
the range of 2–6 L/min. This rapid blood flow allows
infusion of formulations with osmolarities in excess of
900 mOsm/L (central solutions range from ~1500–
2800 mOsm/L). Central venous access devices include
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
Table 5 One Method to Calculate Osmolarity of IV Admixtures
- First, multiply the gm, mEq or mL by the mOsm/unit listed in Table 6
- Add all the multiplied values to determine the total mOsm for the mixture
- Add each volume in the formulation to give a total in liters
- Divide the total mOsm by the total volume in liters to deter- mine the mOsm/L of the formulation
Table 6 Milliosmoles of Selected Additives (15)
Additive mOsm/Unit
Sterile Water 0.
Dextrose Options (3.4 cal/g) Dextrose 5, 10, 30, 50, 70% ~5 mOsm/g
Amino Acid Options (4 cal/g) Amino Acid 8.5, 10, 15% ~10 mOsm/g
Intravenous Fat Emulsion (IVFE) Options 10% (1.1 cal/mL) 20% (2.0 cal/mL) ~0.280 mOsm/mL 30% (3.0 cal/mL)
Micronutrients Calcium Gluconate 0.662 mOsm/mEq Magnesium Sulfate 1 mOsm/mEq Multi-trace Elements (MTE-5) 0.36 mOsm/ml MVI infusion Concentrate (MVI-12)41.1 mOsm/dose Potassium Acetate 2 mOsm/mEq Potassium Chloride 2 mOsm/mEq Potassium Phosphate 2.47 mOsm/mM Sodium Acetate 2 mOsm/mEq Sodium Chloride 2 mOsm/mEq Sodium Phosphate 4.0 mOsm/mM
Table 7 Peripheral Parenteral Nutrition “Vein Protector” (16)
- Hydrocortisone, 15 mg
- Heparin, 1500 units
- Plus: transdermal nitroglycerin (NTG) patch, 0.1 mg/hour
Table 8 Criteria for use of Peripheral Parenteral Nutrition
- Nutritional needs <1800 kcals per day
- Patient requires less than 10 to 14 days of intravenous nutrition
- Peripheral venous access is available (good peripheral veins)
- Requires only one intravenous line with intravenous fat emulsion (IVFE) administration via piggyback infusion
- Fluid restriction is not an issue
gm/kg may avoid uremic complications (26). However ,
if total kcals are inadequate to support protein utilization
or glucose is poorly controlled, catabolism of endoge-
nous protein (lean body mass) will render this interven-
tion useless. Of note, dietary protein only comprises
25% of the nitrogen pool that is turned over each day.
Hence, a change in protein from 1.3 down to 1 g/kg/day
in a 75 kg patient represents a mere decrease of 22 g
protein/day. GI bleeding, hyperglycemia and the obliga-
tory catabolism of trauma/sepsis would generate appre-
ciably more urea than this “additional” 22 grams of pro-
tein/day. In the past, restricting protein in patients with
liver failure was the standard practice; however, it is
now accepted that this may worsen the underlying liver
disease, and does not aid hepatic encephalopathic
episodes. For very nice reviews of protein
in liver and renal disease, see references 27
and 28. Table 9 describes the commonly
available amino acid products and their
characteristics.
To Count, or Not to Count Protein
as Calories?
Total calories are used to characterize oral
diets and tube feeding products. Charac-
terizing the PN prescription as protein and
non-protein calories does not make physi-
ological sense (29,30). The use of non-
protein calories for calculations presumes
that one can direct protein utilization.
Consider: When you provide amino acids to a catabolic
patient, oxidation rates may equal or exceed amino acid
infusion rates. There are multiple pathways taken by
amino acids; utilization of substrate at the cellular level
is not limited to a single pathway. Mixed fuel utilization
will always take place, although the relative amounts of
each substrate may change.
Fat
Intravenous fat emulsions (IVFE), (formerly called
lipid emulsions), are generally used to provide
20%–30% of daily kcals unless conditions exist which
prohibit or complicate lipid administration of this
amount, i.e. hypertriglyceridemia or propofol infu-
sions. Note that the vehicle for propofol is 10% IVFE
and it provides essential fatty
acids, calories (1.1 cal/mL
infused) and vitamin K (31).
See Table 10 for commercial
lipid emulsions available in
the U.S and their vitamin K
content. The content of vita-
min K varies depending on
the manufacturer and con-
centration, with safflower oil
containing less vitamin K
than soybean oil. Vitamin K
typically increases propor-
tionally with increasing lipid
concentrations (example,
viatmin K content doubles
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
(continued from page 53)
Table 10 Energy and Vitamin K Content of Commonly Used IVFE (32–35)
Soybean Oil Safflower Oil Vitamin K Lipid Emulsion Kcals/mL* g/L g/L mcg/dL
Intralipid 10% 1.1 100 0 30. Intralipid 20% 2 200 0 67. Intralipid 30% 3 300 0 93 Liposyn II 10% 1.1 50 50 13. Liposyn II 20% 2 100 100 26 Liposyn III 10% 1.1 100 0 31 Liposyn III 20% 2 200 0 62 Liposyn III 30% 2.9 300 0 93
*Kcals/mL differ according to lipid and glycerol content of IVFE
Table 11 Normal Serum Electrolyte Values and Parenteral and Enteral Ranges (36–38)
Normal Serum Parenteral Adult Enteral Electrolyte Range* Intake Range Requirements
Sodium 135–145 mM/L 0–200 mEq/L 100–150 mEq/day Chloride As needed to maintain acid-base balance Potassium 3.5–5.1 mM/L 0–240 mEq/day 60–120 mEq/day Acetate** As needed to maintain acid-base balance Phosphate 2.3–4.7 mg/dl 0–60 mM/day 15–30 mM/day Magnesium 1.7–2.5 mEq/L 0–48 mEq/day 8–24 mEq/day Calcium 9.2–11.0 mg/dl (ionized calcium 0.8–1.2 mEq/L) 0–25 mEq/day 9–22 mEq/day *Note: Normal lab values vary between institutions and the populations they serve. **Acetate is converted to bicarbonate in the liver.
with an increase from 10% to 20%) (32–34).
Micronutrients
Electrolytes in PN formulations are added according to
anticipated patient requirements, metabolic response to
medications, and recommended daily intakes. Table 11
provides typical ranges for parenteral electrolyte content.
Excessive electrolyte losses from wounds, GI suction,
surgical drains, fever (sweat loss), emesis, and diarrhea
need to be replaced in the PN formulation or other IV
solutions. Table 12 provides the approximate electrolyte
composition and volume of many body fluids.
Vitamins and trace elements are usually added as
commercially prepared multivitamin and trace metal
“cocktails,” which may meet daily requirements and
prevent toxicity. Table 13 reviews the current recom-
mendations for parenteral multivitamin injections by
the Food and Drug Administration (FDA) (39).
The short term (<1 week) PN patient rarely needs
supplementation of Vitamin K, while the long-term
patient requiring PN for weeks to months will likely
require 2–4 mg/week of parenteral vitamin K (40,41).
The newest commercial vitamin products, Infuvite®
(Baxter Healthcare Inc, Deerfield, IL), and MVI-Adult®
(Mayne Pharma (USA), Paramus, NJ) were formulated
to meet the latest FDA standards and
include Vitamin K. Mayne Pharma
manufactures a product that does not
contain vitamin K (MVI-Adult without
vitamin K®), but use of this product is
not necessary, as even patients on
coumadin need some vitamin K. It is
important to remember, however, that
wide fluctuations in vitamin K intake
have significant impact on the effects of
coumadin, and thus, intake should
remain consistent when patients are
placed on this anticoagulant (42). As
previously discussed, IVFEs also con-
tain vitamin K and may contribute sig-
nificant amounts depending on the oil
used, rate of infusion and concentration
of lipid (Table 10).
General trace element dosing
guidelines are listed in Table 14. There
is some concern that the recommended
manganese dose may be excessive for long-term PN
patients. Periodic monitoring is recommended to
ensure whole blood manganese levels remain within
safe limits for patients receiving PN (44). When con-
sidering the dosing of multivitamins and trace ele-
ments, adjustments may need to be made in certain set-
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
Table 12 Approximate Electrolyte Composition of Various Body Fluids (36)
Electrolytes (mEq/L)
Source Volume (mL/d) Na K HCO 3 Cl
Saliva 500–2000 2–10 20–30 30 8– Gastric 2000– pH<4 60 10 — 90 pH>4 100 10 — 100 Pancreatic 1000 140 5 90 75 Bile 1500 140 5 35 100 Small Bowel 3500 100 15 25 100 Colonic — 60 30 — 75 Diarrhea 1000–4000 60 30 45 45 Urine 1500 40 0 — 20 Sweat 1500 50 5 — 55 Reprinted from Matarese LE. Metabolic complications of parenteral nutrition therapy. In: Gottschlich MM, Ed. The Science and Practice of Nutrition Support: A Case-Based Core Curriculum. 2001;269-286, with permission from the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). A.S.P.E.N. does not endorse the use of this material in any form other than its entirety.
Table 13 Recommended Daily Intake of Intravenous Vitamins (39)
FDA/AMA/NAG* Vitamin Recommended amounts/day
Thiamin (B1) 6 mg Riboflavin (B2) 3.6 mg Pyridoxine (B6) 6 mg Cyanocobalamin (B12) 5 mcg Niacin 40 mg Folic Acid 600 mcg Pantothenic acid 15 mg Biotin 60 mcg Ascorbic acid (C) 200 mg Vitamin A 3300 IU Vitamin D 5 mg Vitamin E 10 IU Vitamin K 150 mcg *National Advisory Group on Standards and Practice Guidelines for PN (ASPEN)
account the improved bioavailability of insulin when
added to the PN.
Adjusting dextrose concentration in intravenous
nutrition and monitoring for medication effects can
further aid the practicing clinician in blood glucose
control. Lowering dextrose concentrations is one way
to improve glycemic control where needed. IVFE may
be used to provide a greater percentage of the caloric
intake. In the refractory hyperglycemic patient, some-
times PN just needs to be discontinued until eug-
lycemia is achieved (50). Anticipating drug effects on
blood glucose levels helps maintain control. Table 15
lists some medications, which are known to affect
blood glucose levels. Illness, stress, and activity of the
patient may also play a role and must be considered
when adjusting glucose management. Table 16 pro-
vides additional suggestions to aid in blood glucose
control.
H 2 -antagonists
H 2 antagonists are often added to the PN admixture in
patients requiring gastrointestinal stress ulcer prophy-
laxis. Famotidine is a common additive and has been
shown to be stable in 3-in-1 admixtures of various
compositions for at least 72 hours (53). The adult rec-
ommended dose of famotidine is 20 mg dosed every
12 hours, which can be added to PN as 40 mg per 24-
hour bag. Famotidine is renally excreted, therefore, a
50% dose reduction is recommended when a patient’s
creatinine clearance is <50 mg/min. Ranitidine may
also be added to PN formulations. It is stable in 3-in-
solutions for 24 hours, however more than 10% of the
drug may be lost at 48 hours (54). The adult recom-
mended dose is 200–300 mg daily, generally not to
exceed 400 mg per day. Doses should be reduced to 50
mg daily if the creatinine clearance is <50 mg/min
(55). Patients receiving an intravenous or oral proton
pump inhibitor usually do not need a H 2 -antagonist.
Iron
Iron supplementation may be needed for chronic home
PN patients. Although body stores should last for up to
6 months, deficiencies have been reported after 2
months on PN without supplementation (56). Iron dex-
tran has been used in 2-in-1 PN formulations in doses
of 10–75 mg/day with no apparent side effects (57,58).
However, the addition of iron to 3-in-1 PN admixtures
has not been well studied and reports of incompatibil-
ities exist (58). Anaphylaxis and destabilization of
lipid formulations are both problems associated with
this form of iron, and many clinicians prefer to sup-
plement iron separately from PN solutions. Some of
the newer iron products such as Ferrlecit®^ (Na ferric
gluconate complex) by Schein and Venofer ®^ (iron
sucrose or iron saccharate complex) by American
Regent may be considered for use separate from PN.
Due to the complexity of PN formulations and the
small market share of the PN population, compatibility
studies of these new iron compounds in PN are
unlikely to ever be performed by the manufacturers.
FREQUENTLY ASKED QUESTIONS
IN THE CLINICAL SETTING
How Should PN Be Initiated?
Although PN infusion rates are often gradually
advanced, there is no real reason to do this. Patients
with diabetes, at a high risk for refeeding, or patients
starting PN at home might benefit from this approach;
however, in the acute care setting, this is not necessary.
Hospitalized patients requiring PN can be started at the
goal rate for the volume to be provided; assuming
measures have been taken to minimize metabolic
response (i.e., patient not overfed).
Hyperglycemia puts the patient at risk for infec-
tion and thwarts utilization of nutrients that the par-
enteral formulation provides. Overfeeding should be
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
(continued from page 58)
Table Suggested Strategies for Improving Glucose Control
- Do not overfeed the patient
- Limit dextrose in TPN to 150 g/day initially
- Review other sources of IV dextrose (including CVVHD, peritoneal dialysis, antibiotic drips, etc.—PN may need to be adjusted accordingly).
- Increase units of insulin given at each step for sliding scale coverage
- Increase frequency of glucose checks if necessary (every 4–6 hours)
- Add insulin drip
- Stop TPN for 24 hours and get glucose under control
avoided with any form of nutrition support; dextrose is
usually the macronutrient of most concern with PN;
therefore, if calorie requirements are the reason for a
slow escalation, then the dextrose can be provided at a
fractional amount of the goal and increased as the
patient tolerates. If the PN carbohydrate content has
been limited in anticipation of refeeding, or for the
presence of hyperglycemia, there is no need to also
limit the PN rate or “titrate the rate up” as this would
be “doubly cautious” and unnecessary. Daily reformu-
lations as necessary are based on current lab values
and the response to any changes made previously.
When Should PN Be Discontinued?
PN should be discontinued with transition to PO or
enteral nutrition as soon as feasible. Many patients
may benefit from a trophic enteral feeding while on
PN. Once enteral feedings or PO intake has advanced
to >50% of estimated kcals, and the patient is tolerat-
ing this well, the PN formula can be weaned or dis-
continued. PN can be restarted in 2–3 days if the
patient does not continue to tolerate enteral or PO
nutrition or if intake is less than 50% of estimated
requirements. Attention to glycemic control post-PN is
crucial in those patients who have not previously been
diagnosed as having diabetes mellitus, yet required
insulin with the PN and became hyperglycemic again
once PN stopped. PN therapy may act as a very expen-
sive surrogate glucose tolerance test.
How Should PN Be Tapered?
There is a general belief that PN formulations require
tapering. Rebound hypoglycemia is rarely seen but is
often discussed in the clinical setting (59–61). The risk
is very low, even in patients with diabetes mellitus, as
they are somewhat “protected” by inherent insulin defi-
ciency. Stopping PN with insulin is the same as stop-
ping an independent insulin drip; remember, the half-
life of regular insulin is only 5 minutes (although,
somewhat longer if the patient is in renal failure). A
taper down of PN is not needed, especially if the patient
is receiving another dependable source of carbohy-
drate. If a particular patient is prone to hypoglycemia,
tapering PN over 1–2 hours before discontinuation is
justified and can avoid this problem.
When Should I Be on the Lookout
for Refeeding?
Many hospitalized patients are malnourished due to
the nature of their disease and/or treatment effects.
When initiating nutrition support, it is important to
monitor these patients closely to avoid refeeding.
Refeeding syndrome is characterized by an abrupt
decrease in serum potassium, magnesium and/or phos-
phorus. This results from pancreatic stimulation and
insulin secretion (the driving force behind refeeding)
after the introduction of a consistent nutrient source,
primarily carbohydrate. The clinical presentation of
refeeding syndrome can also include sodium and fluid
retention causing edema, which may result in stress to
the cardiac and respiratory systems. In these patients,
PN should be started at partial, or “refeeding” calories,
especially carbohydrate, with an appropriate supple-
mentation of electrolytes and vitamins as appropriate.
Once the patient is stable, PN can then be advanced to
target as tolerated. A thorough discussion of this topic
is available elsewhere (62).
What Happens If the Patient is Overfed?
While it is natural to want to provide “hyperalimenta-
tion” via the parenteral route for malnourished and
catabolic patients, overfeeding, especially in cases of
previously undernourished patients can cause more
harm than good (see refeeding above). Critically ill
and post-surgical patients often have an “obligatory
hypercatabolism” not correctible by feeding (63).
Overfeeding these patients may increase stress on vital
organs including the heart, liver, and kidneys (64,65).
All PN patients should be monitored closely and
calories rarely need to exceed 30–35 kcal/kg. Indirect
calorimetry may be helpful in some patients to
help determine calorie needs and avoid under, or over-
feeding (66).
Which is Best? 3-in-1 Versus 2-in-
Many institutions have switched from the traditional 2-
in-1 PN admixtures to a 3-in-1 admixture combining
IVFE into the amino acid/dextrose mix rather than
hanging the IVFE separately. Both systems are avail-
able to the practicing clinician and each has advan-
tages as well as disadvantages. These are reviewed in
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
(continued on page 64)
oral/enteral intake and the impact of medications.
Experience allows anticipation of trends and impact
on electrolyte manipulations. This is particularly
helpful when monitoring intervals are extended as
they are for home PN patients. Trends in serum elec-
trolyte levels are far more meaningful than looking
at a single value. Serum electrolyte levels fluctuate
under natural physiologic control and variance in
lab equipment. Minute adjustments in PN electrolytes
are rarely beneficial and often only warranted if the
patient has been on PN for a long enough time period
that response is well known. For a nice review/guide-
lines for electrolyte replacement, see references
How Often Should Labs Be Checked?
Daily labs are needed when initiating PN. This fre-
quent level of monitoring may be warranted for several
days to >2 weeks while electrolytes are being adjusted
and the impact of PN initiation and advancement takes
place. Guidelines for appropriate lab monitoring are
addressed in Table 18.
Long-term Complications
Long-term complications of PN can include fatty liver,
cholestasis, metabolic bone disease, and electrolyte/
vitamin/mineral depletion or toxicity (46). In the long-
term PN patient, it is important to be aware of, and
monitor for, these adverse effects. This topic is beyond
the scope of this article, however, a nice review of long-
term complications is readily available (47). See Table
19 for gastrointestinal complications of long term PN.
What Should You Do When the Labs
on Your PN Patient Look Like This?!!
Lab Result @ 4:00 A.M.
Sodium 125
Potassium 6.
Chloride 101
CO 2 17
BUN 12
Creatinine 0.
Glucose 896
Triglycerides 684
Magnesium 3.
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
Table 18 Suggested Monitoring for Parenteral Nutrition (In-patient)
Parameter Baseline Initiation Critically Ill Stable Patients
CBC with differential Yes Weekly Weekly PT, PTT Yes Weekly Weekly Basic chemistry—Na, K, Cl, CO 2 , BUN, creatinine Yes Daily × 3 Daily 1–2 times per week Magnesium, calcium, phosphorus Yes Day 1 As needed Weekly Serum triglycerides Yes Day 1 As needed As needed Serum glucose Yes Daily Daily 1–2 times per week Capillary glucose Q 6 hrs × 48 hrs; As needed 3 x day until consistently As needed stop if WNL <150 mg/dl* Weight Yes Daily Daily 2–3 times per week Intake and output Yes Daily Daily As needed ALT, AST, ALP, total bilirubin Yes Day 1 Weekly Monthly Nitrogen balance As needed As needed As needed CBC = complete blood cell count; BUN = blood urea nitrogen; PT = prothrombin time; PTT = partial thromboplastin time; ALT = alanine aminotransferase; AST = aspartate aminotransferase; ALP = alkaline phosphatase. *More tightly controlled blood glucose levels of 80-130 may be sought (49). Adapted from Mirtallo JM. Introduction to parenteral nutrition. In: Gottschlich MM, Ed.The Science and Practice of Nutrition Support: A Case-Based Core Curriculum. Dubuque, IA: Kendall/Hunt Publishing Co.;2001: 211–223, with permission from the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). A.S.P.E.N. does not endorse the use of this material in any form other than its entirety.
A. Order insulin (20 units SQ) and sodium poly-
styrene resin (Kayexalate®) 30 mL enema STAT
B. Call the endocrine fellow
C. Check fingerstick glucose at the bedside NOW for
quick verification of chemistry result before giving
insulin
Note: This patient’s fingerstick glucose at 1800
and 2400 during PN infusion were 141 and 103
respectively.
The above situation demonstrates spurious lab results
after PN contamination of a blood sample drawn from
a central line without following proper flushing proce-
dure. The procedure includes turning off the PN, flush-
ing the line, discarding the initial aspirate, then draw-
ing up the sample amount needed for the lab and then
resuming the PN. If the PN admixture is not turned off
and/or if the flush is inadequate prior to the draw, the
lab results will reflect the extraordinarily high glucose,
potassium and triglyceride levels in the sample sec-
ondary to contamination with the PN solution. Other
electrolyte imbalances may also be seen. Although the
PN may be held upon reviewing these results, a quick
check of a bedside finger stick blood sugar and subse-
quent lab redraw is the most appropriate response.
CONCLUSION
PN is a valuable and necessary medical treatment for
many patients providing both nutritional sustenance
and life extension at a time when it is not possible to
sustain them any other way. By focusing on the essen-
tial elements of PN management, this form of nutrition
support can be applied successfully with minimal com-
plications, thus providing great benefit to those who at
one time would have been deemed “unfeedable.” See
Table 20 for summary guidelines. ■
NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #
Table 19 Complications of Long Term PN (9,36)
Problem Possible Causes Symptoms Treatment/Prevention
Fatty Liver Exact etiology unknown. Theories include: Elevation of LFTs • Avoid overfeeding Overfeeding of dextrose &/or total calories; • Do not exceed recommended overfeeding of fat; EFAD; carnitine dosages of macronutrients deficiency,choline deficiency (Table 3)
- Enteral nutrition as soon as possible (even if trophic)
- Enteric antibiotics if blind loops/ bacterial overgrowth possible
- Add Taurine to PN
Cholestasis Exact etiology unknown. Theories include: Elevated alkaline phosphatase; • Avoid overfeeding lack of nutrition in the bowel leading to progressive increase in • Do not exceed recommended decreased bile stimulation and impaired total bilirubin dosages of macronutrients bile flow; overfeeding of glucose, lipid (Table 3) and/or amino acids; toxic tryptophan • Enteral nutrition as soon as metabolites, choline deficiency possible
- Enteric antibiotics if blind loops/ bacterial overgrowth possible
Gastrointestinal Atrophy of villi in the GI tract due to lack Observedin vitro;in vivo only • Enteral/oral nutrition concurrent Atrophy of enteral nutrients symptom may be enteric or as soon as possible bacteremia and sepsis without clear source
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