,

40–47 Several meta-analyses have shown benefit on clinical outcomes

(e.g., infectious complications, ventilator days, LOS); however, no mortality benefit

has ever been found in critically ill patients receiving immunonutrition versus

standard EN.

4,18–20

,

48

The population which appears to have better outcomes with immune-modulating

EN is patients undergoing major elective surgery, particularly surgery for upper GI

malignancy. Reduced infection risk and shorter LOS in high-risk elective surgery

patients, mostly patients with upper GI malignancy, receiving immunonutrition with

EN supplemented with both arginine and fish oil was shown in a meta-analysis.

47

Joint guidelines from SCCM–ASPEN gave the highest recommendation for use of an

immune-modulating EN formula in patients undergoing major elective surgery,

trauma, burns, and head and neck cancer; the recommendation was slightly lower for

critically ill, mechanically ventilated, nonsurgical medical ICU patients.

4

Conversely, CCP guidelines advise against use of formulas with “arginine and other

nutrients” in critically ill patients based on failure to show an infectious or mortality

benefit and potential for harm in septic patients.

18–20 Neither the CCP guidelines nor

the SCC-ASPEN guidelines recommend use of an arginine-supplemented immunemodulating formula for patients with severe sepsis.

4,18–20 Additional studies with

well-defined patient populations are necessary to determine the effects of

combinations of immune-modulating components (arginine, glutamine, nucleic acids,

ω-3FAs), optimal component and dose combinations, and the most beneficial timing

for administration of immune-modulating components.

Altered Fat Components

Stress or critical care and immune-modulating formulas contain different sources of

fat to alter the type of fatty acids provided. Fat sources commonly include MCTs,

along with predominantly canola oil, high-oleic oils, or fish oils. Absorption of

MCTs is relatively independent of pancreatic enzymes and bile salts, and is

carnitine-independent; thus, they can be absorbed in patients experiencing

malabsorption of the long-chain triglycerides. Formulas containing a relatively large

percentage of fat calories as MCTs are frequently marketed for critically ill patients

with malabsorption.

Canola oil and high-oleic oils have high monounsaturated fatty acid (MUFA)

content. MUFAs have been popularized by reports of low cardiovascular disease in

populations using olive oil, but further research is needed to determine the role of

these fatty acids in ill patients. Usual polyunsaturated vegetable oils (i.e., corn, soy,

and safflower oils) are avoided or provided in relatively small quantities in critical

care formulas to limit omega-6 fatty acids (ω-6FAs), which are precursors to

inflammatory, vasoconstrictive, and platelet-aggregating agents.

50,51 Some ω-6FAs

may, however, be converted to γ-linolenic acid (GLA), then to dihomo-GLA, and

subsequently to arachidonic acid.

52 Dihomo-GLA competes with arachidonic acid in

the pathways for prostaglandin synthesis resulting “1” series prostaglandins with

lower proinflammatory effects, similar to “3” series prostaglandins from ω-3FA.

Small amounts of ω-6FAs are required in the diet to prevent deficiency of linoleic

acid, an essential fatty acid not provided by MCT and fish oils.

Fish oils, including menhaden oil, provide fatty acids primarily from the ω-3

family, with the very long-chain fatty acids eicosapentaenoic acid (EPA) and

docosahexaenoic acid (DHA) predominating. The proposed role of ω-3FAs in

critical illness is to reduce infectious complications and death in selected patient

populations. The ω-3FAs are precursors to less inflammatory and more vasodilatory

eicosanoids than those from ω-6FA.

50–52

Few data are available evaluating effects of only fat modification in EN for

critical illness, and combinations of immune-modulating components may produce

different effects than single nutrients. Improved clinical outcomes for postsurgical

and critically ill patients have been associated with EN-containing ω-3FAs, usually

in conjunction with other immune-modulating components, although the effects remain

controversial.

4,18,26 Some studies suggest data are inadequate to support routine use of

fish oil, whereas others indicate the potential for arginine to counteract the benefit of

fish oil in EN containing combinations of immune-modulating components.

53,54

Studies suggest a minimum of 5 to 7 days of supplementation with immunemodulating components, including ω-3FAs, is necessary to see beneficial effects on

postoperative outcomes.

49–51

Incorporation of ω-3FAs into cell membranes may be

required to see benefits; this has been demonstrated in humans with supplementation

for 5 days.

55 Fat modification to provide high-ω-3FA content also has been studied in

ARDS and acute lung injury (as discussed in the Pulmonary Disease section).

The question of whether to initiate EN in J.B. with an immune-modulating formula

does not have a clear-cut answer. The data provided for J.B. do not indicate sepsis;

thus, he would be a candidate for an immune-modulating formula using the SCCM–

ASPEN guidelines.

4 The more conservative CCP guidelines would not recommend

an arginine-containing immune-modulating formula.

18–20 The decision of whether to

use the immune-modulating formula would likely depend on practices within the

hospital and the immune-modulating formulas available. Because J.B. was admitted

with pneumonia and now has ARDS, the other consideration would be whether a

specialized pulmonary formula would be more appropriate for his EN.

PULMONARY DISEASE

CASE 37-3, QUESTION 2: How do pulmonary formulas differ from standard polymeric formulas? If J.B.

receives a specialized pulmonary formula, what nutrient modifications should the formula contain?

There are two types of EN formulas intended for patients with pulmonary

conditions. Both have a moderate caloric density (1.5 kcal/mL) and the percentage of

calories from fat is relatively high (40%–55%), although the types of fats differ. The

premise

p. 779

p. 780

for higher fat content is that fat metabolism produces less carbon dioxide (CO2

)

than carbohydrate metabolism, thereby reducing the work load of the lungs. Early

studies comparing isocaloric, high-fat, low-carbohydrate diets with highercarbohydrate diets showed improved respiratory parameters in ambulatory patients

with chronic obstructive pulmonary disease (COPD) as well as reduced time on the

ventilator and decreased arterial CO2 concentrations in mechanically ventilated

patients.

26,56,57 Caloric intake in these studies ranged from 1.7 to 2.25 times the

measured energy expenditure, which is excessive by current standards. Excess

calories contribute to higher CO2 production; thus, the early studies are of

questionable relevance, and in practice, preventing overfeeding is as important for

control of CO2 as high-fat, low-carbohydrate diets.

26,27

In addition, improved

respiratory parameters with a high-fat EN product are unlikely in patients without

excess CO2 production or retention. Data from 60 malnourished, underweight

patients with COPD do suggest respiratory status in this population is more likely to

benefit from a high-fat, low-carbohydrate (28% of calories) formula compared with

a high-carbohydrate (60%–70% of calories) formula.

58 Although the percent of

calories from fat (55%) in the high-fat formula was similar to traditional pulmonary

formulas, fat distribution was considerably different with 20% of fat as MCTs and a

predominance of MUFAs. Currently marketed pulmonary formulas contain 20% to

40% of fat calories as MCTs and fat sources providing higher MUFAs. During a

period of overfeeding for weight gain, pulmonary formulas may be reasonable;

however, they are not warranted for routine use in most patients.

The second type of pulmonary EN formula is an immune-modulating pulmonary

(IMP) formula with an anti-inflammatory lipid profile (fish oils rich in ω-3FAs,

borage oil rich in GLAs), antioxidants (vitamins C and E, βcarotene), and no

supplemental glutamine or arginine, which has been studied in patients with ARDS

and ALI.

4,18–20 Three studies comparing this formula with a typical high-fat pulmonary

formula with elevated ω-6FA content were included in a meta-analysis by PontesArruda et al.

59 and showed a significant reduction in new organ failures, time

receiving mechanical ventilation, ICU LOS, and mortality.

Based on the one study available when the initial CCP guidelines were published,

the committee recommended use of IMP formulas with a combination of fish oils,

borage oil, and antioxidants in patients with ARDS.

18 The SCCM–ASPEN and

updated 2009 CCP guidelines evaluated additional studies and both recommended

patients with ARDS or ALI be placed on an IMP formula.

4,20 However, the choice of

control formula in these otherwise high-quality studies has been questioned because

there is some evidence of harmful effects from administration of ω-6FA-rich fats in

critically ill patients.

18

The study by Grau-Carmona et al.

60 compared an IMP formula to standard EN

rather than a high-fat pulmonary formula. In 132 septic patients with ARDS or ALI,

no difference was found in gas exchange, ventilator days, or infection rate, although

ICU LOS was less with the IMP. Based on inclusion of this study and one other with

those available from previous CCP evaluations, the 2013 CCP guidelines

downgraded their recommendation to consider use of a IMP formula in patients with

ARDS or ALI.

20 An additional study using an IMP formula preemptively in severe

trauma patients was included in the 2015 CCP guidelines.

19 No difference was found

in the level of oxygenation, development of ALI or ARDS, ventilator days, ICU LOS

or mortality; however, more patients in the study group developed bacteremia.

61 The

2015 CCP guidelines remained the same as in 2013.

19

J.B. was diagnosed with ARDS; therefore, an IMP formula could be considered

based on the CCP and SCCM–ASPEN guidelines.

4,19,20 The formula should contain

fish oils to provide a high-ω-3FA content, borage oil to provide GLA, and increased

antioxidant vitamin content. Delayed gastric emptying is associated with high-fat

diets and must be considered when evaluating possible benefits and adverse effects

of high-fat EN. This applies to both IMP and routine pulmonary formulas. Abdominal

distension, increased gastric residuals, nausea, and vomiting can result from delayed

gastric emptying. J.B. has his feeding tube placed in the small bowel, so delayed

gastric emptying is not a concern. However, the potential to overwhelm pancreatic

lipase activity resulting in fat malabsorption should be considered when a high-fat

load, especially long-chain triglycerides, is delivered into the small bowel.

Continuous infusion is more likely to be tolerated than other, more rapid delivery

methods in most patients. As shown in Table 37-2, the cost of routine pulmonary

formulas is slightly higher than for standard polymeric formulas and IMP formulas

are significantly more expensive.

RENAL FAILURE

CASE 37-3, QUESTION 3: J.B. has been in the ICU for 10 days. His ARDS has improved; however, he

now has acute kidney injury and hemodialysis willstart today. Morning laboratory results include the following:

Sodium, 131 mEq/L

Potassium, 5.7 mEq/L

BUN, 80 mg/dL

SCr, 3.8 mg/dL

Glucose, 100 mg/dL on an insulin drip

Magnesium, 2.9 mg/dL

Phosphorus, 5.6 mg/dL

WBC, 9.7 × 10

3

/μL

Hgb, 11.4 g/dL

Hct, 34.3%

An EN formula for renal failure is ordered. How do the nutrient components in renal formulas differ from

standard polymeric EN formulas? Is a renal formula appropriate for J.B.?

Two types of EN formulas for renal disease/injury are available and both are

calorically dense (1.8–2 kcal/mL) to limit fluid provision. Highly specialized

formulas with enriched essential amino acid content are based on the theory that

recycling of urea nitrogen for nonessential amino acid synthesis reduces the

accumulation of BUN.

26,56,57 Clinically significant recycling of nitrogen and

incorporation into nonessential amino acids does not appear to occur, however.

Essential amino acid formulas may be appropriate for patients with chronic renal

failure with glomerular filtration rates less than 25 mL/minute/1.73 m2 who are

receiving very low-protein diets and for whom dialysis is not an option.

56 Use should

be limited to no more than 2 to 3 weeks, because hyperammonemia and metabolic

encephalopathy have been associated with longer use. These formulas are not

appropriate for patients with acute kidney injury, such as J.B., or for those receiving

dialysis. The NPC:N ratio is approximately 300:1 in these formulas. Water-soluble

vitamins are typically included in currently available high essential amino acid

formulas; however, vitamin content should be reviewed as some essential amino acid

formulas do not contain vitamins. Renalcal contains higher-than-normal essential

amino acids with about two-thirds essential combined with one-third nonessential

amino acids.

Polymeric enteral formulas designed for renal failure or renal insufficiency are the

standard for hospitalized patients with impaired renal function. These formulas

contain a balanced amino acid profile and are not enriched with essential amino

acids. The NPC:N ratio varies from about 130:1 (for patients with increased nitrogen

losses from dialysis) to 230:1 (typically used for nondialyzed patients).

p. 780

p. 781

Lower-than-normal concentrations of potassium, phosphorus, and magnesium are

used in these formulas to minimize electrolyte problems. Many critically ill patients

receiving dialysis for acute kidney injury tolerate a nonrenal formula; however, those

with elevated potassium, phosphorus, or magnesium generally require a renal

formula to control electrolyte levels. Based on his electrolytes, J.B. will require a

renal formula. A polymeric formula with a lower NPC:N ration (i.e., 140:1;

moderate protein content) would be appropriate given the plan for dialysis.

Polymeric renal formulas meet 100% of the DRI with less than 2,000 mL/day.

Modular Components

CASE 37-3, QUESTION 4: After several days on the renal formula (NPC:N ratio, 140:1), there are

indications that J.B.’s protein intake should be higher. Serum electrolytes today include the following:

Sodium, 137 mEq/L

Potassium, 5.1 mEq/L

Phosphorus, 4.5 mg/dL

Magnesium, 2.6 mg/dL

What are the options for increasing protein provision?

J.B. is receiving a renal formula with moderately high-protein content based on the

NPC:N ratio of 140:1. There are no very high protein formulas with low potassium,

phosphorus, and magnesium on the market; therefore, a very high protein formula will

provide significantly more of these electrolytes than J.B. currently receives. His

current serum levels of the renally eliminated electrolytes are near the upper end of

normal and would likely rise above the normal range if the EN is changed to a

nonrenal formula. Using a lower potassium concentration in the dialysis bath might

keep serum potassium within normal range. Addition of a phosphate binder to the

medication regimen could be considered; however, the risk of tube occlusion may be

increased with a phosphate binder. A better option is to provide additional protein

from a modular protein component, although this can also increase the risk of tube

occlusion if not administered properly.

Modular components are individual nutrient substrates, or combinations of two

substrates, designed for addition to oral diets or enteral formula regimens. They

provide only the macronutrient(s) without electrolytes or vitamins, and should only

be used to supplement a diet or EN, not as a sole source of nutrition. Protein modules

are powders containing 3 to 5 g protein/tablespoon. Most protein modules are intact

protein. Arginine and glutamine are available as individual packets to allow

supplementation as a single amino acid. Glucose polymers are used to supplement

calories as carbohydrate. They do not increase osmolality or alter food or formula

flavor. Powdered carbohydrate modules contain 20 to 30 kcal/tablespoon, whereas

liquids contain 2 kcal/mL. Protein and carbohydrate modular components typically

are mixed with water and administered through the feeding tube rather than being

mixed directly into the formula. Additional fat can be provided as 50% safflower oil

emulsion (Microlipid) or as MCT oil. A combination carbohydrate and fat modular

product is available if both sources of calories are appropriate. A modular fiber

product containing soluble fiber in the form of partially hydrolyzed guar gum is also

available.

Glucose Control Formulas

CASE 37-4

QUESTION 1: M.P., a 59-year-old man, is admitted to the hospital secondary to dehydration and for a GI

workup related to a 35-pound unintentional weight loss during the past 3 months. He states he has been unable

to eat for a week due to continual nausea, although he reports no vomiting. M.P. received IV fluids in the ED

and currently has 0.9% sodium chloride infusing at 125 mL/hour. Past medical history includes hypertension,

hyperlipidemia, gastric reflux, and diabetes mellitus type 2. M.P. is 5 feet 11 inches tall and his admit weight is

130 kg. Laboratory values from this morning show the following results:

Glucose, 230 mg/dL

BUN, 20 mg/dL, down from 31 mg/dL in the ED

SCr, 1.2 mg/dL, down from 2.3 mg/dL in the ED

Sodium, 141 mEq/L

Potassium, 4.3 mEq/L

Chloride, 105 mEq/L

His small bowel follow-through study indicates severely delayed gastric emptying. A feeding tube is to be

placed into the small bowel for a trial of enteral feeding.

Should a “glucose control” or “diabetic” formula be used for initiating tube feedings in M.P.? How do

formulas for glucose control differ from standard polymeric EN formulas?

No ideal macronutrient distribution has been identified for meals intended for

patients with diabetes mellitus and general dietary guidelines for healthy eating are

considered appropriate.

62 However, formulas for hyperglycemic patients, known as

diabetic formulas, do not necessarily follow this recommendation. Diabetic formulas

have caloric distributions of 31% to 40% carbohydrate, 42% to 49% fat, and 16% to

20% protein. The carbohydrate content is lower, and fat content is higher than in most

standard polymeric formulas. High MUFA sources predominate to provide greater

than 60% of fat as MUFAs. The source and type of carbohydrates in diabetic

formulas varies, with a predominance of more complex carbohydrates (i.e.,

oligosaccharides, cornstarch, fiber) and insulin-independent sugars (i.e., fructose).

Fiber sources associated with improved glycemic control, mainly soluble fibers but

also soy polysaccharide, are included in these formulas to help minimize

postprandial hyperglycemia. Fiber content ranges from 14 to 21 g/L and formulas are

1 kcal/mL; thus, the recommended fiber intake of 25 to 38 g daily generally can be

achieved with less than 2,000 kcal/day.

29

Multiple studies comparing diabetic formulas to standard EN formulas providing

equal calories and protein have been conducted. Results of a large meta-analysis

including 23 studies, 19 being randomized controlled trials, favor the diabetic

formulas for glucose control.

63 Postprandial increases in glucose, glucose area under

the curve, and peak blood glucose concentrations were significantly reduced with the

diabetic formulas. However, there were no significant effects on total cholesterol,

high-density lipoprotein, or triglyceride concentrations, or on overall complication

rates. Also, mortality differences were not found in the single 2-week trial reporting

mortality for critically ill patients. Ability to utilize results of this meta-analysis in

practice is limited by many studies of low methodologic quality, inclusion of singlemeal trials, and use of oral supplements in healthy volunteers. For hospitalized

patients with hyperglycemia, no well-designed clinical trials of adequate size were

found to make a recommendation regarding use of diabetic formulas in the ASPEN

guidelines regarding adults with hyperglycemia.

64

M.P. could receive either a diabetic formula or a standard formula. The metaanalysis discussed previously would suggest glucose control may be better with a

diabetic formula; however, the ASPEN guidelines found inadequate data to make a

recommendation regarding use of diabetic formulas in hospitalized patients with

hyperglycemia and the Academy of Nutrition and

p. 781

p. 782

Dietetics suggests following a general pattern of healthy eating for patients with

diabetes.

62–64 Either a diabetic or standard formula would be acceptable for M.P.

based on available data. Problems with delayed gastric emptying or fat

malabsorption must be weighed against possible benefits of improved glucose

control with diabetic formulas. These problems are of minimal concern for M.P. as

he is being fed into the small bowel and his history does not suggest fat

malabsorption. Treatment goals for EN in patients with diabetes mellitus should

include individualization of macronutrient composition, avoidance of excess

calories, and maintenance of euglycemia.

62–64 M.P. may benefit from a treatment plan

that includes gradual weight loss and this may influence the decision of whether to

use a diabetic formula or a very high protein formula that would permit lower total

calories while still providing adequate protein.

MONITORING ENTERAL NUTRITION SUPPORT

CASE 37-4, QUESTION 2: What types of complications can occur with tube feeding? What steps can be

taken to prevent complications in M.P., and how should he be monitored for complications?

Appropriate monitoring of patients receiving EN is essential to recognize and

prevent complications. Complications can be divided into three groups: mechanical,

metabolic, and GI (Table 37-5).

Mechanical Complications

The major mechanical complications are tube occlusion and aspiration. Mechanical

complications often can be avoided with good nursing technique and careful

observation of feeding tolerance. Adequate tube flushing is essential to prevent tube

occlusion. Flushing with 30 mL of water every 4 hours during continuous feeding or

before and after intermittent feedings is recommended.

34,35 Flushing must also occur

before and after medication administration and after withdrawal of gastric contents.

M.P.’s tube should be flushed using these guidelines. Frequent assessment of tube

placement by auscultation, location of markings on the tube, and withdrawal of

gastric contents is important to prevent pulmonary aspiration of the formula

secondary to displacement of the tube into the esophagus or pharynx. Tube placement

should be evaluated every 4 to 6 hours with continuous feeding, or before each

intermittent or bolus feeding.

34,36,37,39,57

Withdrawal of gastric contents through a gastric tube using a syringe allows

evaluation of volume in the stomach (gastric residual volume [GRV]). Endogenous

secretions from saliva and gastric fluids, about 4,500 mL/day in normal adults

receiving food, contribute to GRV when gastric emptying is impaired. Variations in

GRV also occur based on the volume and timing of previous feeds, especially for

intermittent or bolus feeds, feeding tube characteristics, and patient position and

activity.

36,37 Gastrostomy tubes may yield less volume than NG tubes because of their

more anterior position in the stomach. Soft, small-bore feeding tubes may collapse

when GRV is checked, resulting in falsely low GRV. GRV is not usually checked

through tubes placed in the postpyloric region because (a) problems with tube

collapse have been reported and (b) the small bowel does not serve as a reservoir

for residuals. M.P. has a jejunal feeding tube; thus, GRV is not reliable when

checked through his feeding tube. If M.P. has an NG tube in addition to a small bowel

feeding tube, GRV can be checked through the NG tube to assess whether formula is

“backing-up” or refluxing into the stomach. Previously, methylene blue or blue food

coloring was added to the formula to evaluate reflux; however, reports of mortality

associated with this practice resulted in its abandonment.

4,14,34,35 The use of glucose

oxidase test strips to detect the presence of enteral formula in tracheobronchial

secretions lacks sensitivity and specificity, and the results have not been shown to

correlate with aspiration; thus, it is not a recommended practice.

33,34,35,36 Current

practice recommendations vary on the GRV volume for to holding feeding; CCP

guidelines recommend holding at somewhere from 250 to 500 mL whereas SCCM–

ASPEN recommendation holds for GRV greater than 500 mL and consider jejunal

placement of the feeding tube when GRV is consistently greater than 500 mL.

4,19,20,35

In addition, use of a promotility agent, preferably metoclopramide, should be

considered when GRV is greater than 250 mL after a second check.

19,20 These agents

may improve feeding tolerance and formula delivery, and the risk of aspiration may

be decreased, although the benefit of these agents has been questioned. If the feeding

is held because of a high GRV, hourly evaluation of the GRV is recommended until

the volume is less than 200 to 250 mL and the feeding is restarted. The fluid

withdrawn for GRV assessment may be infused through the tube back into the

stomach to minimize electrolyte imbalances; however, CCP guidelines suggest either

discarding GRV or feeding back up to 250 mL may be acceptable.

19,20 Elevating the

head of the bed to 30 to 45 degrees, with 45 degrees preferred in critically ill

patients, during and after feedings also is recommended to reduce the risk of

aspiration.

19,35,39

Metabolic Complications

Major metabolic complications of EN include hyperglycemia, electrolyte

abnormalities, and fluid imbalance. Although rigorous studies evaluating monitoring

frequency are lacking, regular biochemical determinations similar to those used for

PN are recommended to identify and correct metabolic abnormalities before severe

abnormalities occur. Baseline values for serum glucose, SCr, BUN, and electrolytes

should be available to guide selection of the enteral formula. The few baseline

laboratory results available for M.P. may be adequate as a baseline, but additional

laboratory parameters will be necessary as part of the monitoring regimen once EN

starts.

Capillary glucose measurements every 6 hours or an insulin protocol is

recommended before EN starts in diabetic or hyperglycemic patients or if

hyperglycemia is anticipated. Given M.P.’s history of diabetes and a baseline

glucose greater than 200 mg/dL, diligent monitoring and treatment of his

hyperglycemia is warranted even before EN starts. M.P. will require long-term

glucose monitoring; however, routine glucose monitoring in nondiabetic patients can

be stopped once a stable euglycemic state is established with EN at the goal volume

and infusion regimen.

A basic metabolic panel ([BMP]; serum glucose, sodium, potassium, chloride,

bicarbonate, calcium, BUN, and SCr) is generally checked daily after feeding starts

in critically ill patients and those at risk of electrolyte abnormalities or renal

dysfunction. More stable patients may have serum glucose and electrolytes (sodium,

potassium, chloride, bicarbonate) monitored rather than a BMP. During the first week

of EN, whether initiated in the hospital or alternate site (SNF or at home), a BMP,

phosphorus, and magnesium should be monitored a minimum of 2 to 3 times weekly

in patients with weight loss; once or twice weekly may be adequate if there is no

weight loss. Monitoring frequency can be reduced once tolerance to tube feeding is

established and there are no metabolic abnormalities. Daily BMP for a minimum of 4

to 5 days is probably best for M.P. considering his recent dehydration. Daily

phosphorus and magnesium also should be considered for a few days in M.P.

because of his significant weight loss and risk of refeeding syndrome (see chapter 38

for a more detailed discussion of refeeding syndrome). Despite being obese, M.P. is

at risk of electrolyte abnormalities associated with refeeding syndrome.

25 Failure to

monitor M.P. and replace electrolytes as necessary could result in serious electrolyte

abnormalities. Once M.P.’s BMP, phosphorus, and magnesium are stable, the

frequency of monitoring could be reduced to once or twice weekly. Critically ill

patients generally require daily or every other day monitoring while in the ICU. For

patients receiving long-term EN, the frequency of laboratory monitoring gradually is

decreased. Laboratory monitoring should be done once or twice yearly in stable

patients without significant medical problems. Patients who have medical problems

that can affect nutrient, electrolyte, or trace element requirements or tolerances

should be monitored as appropriate to the medical condition.

p. 782

p. 783