Parenteral Nutrition: Indications and Practical Applications, by Katelyn Ariagno.
Hi, my name is Katelyn Ariagno.
And I'm a Registered Dietitian here at Children's Hospital Boston.
Today, we'll be talking about a couple different nutrition topics specific to the ICU and ICU
care.
Just to remind you that these are guidelines that we've established here at Children's
Hospital Boston, and you may need to alter these guidelines depending on your institution
and your resources that are available to you.
Nutrition Assessment and Estimating Nutrition Needs.
The first topic I'll be talking about today is estimating nutritional needs.
Estimating nutritional needs in the critically ill child remains a challenge.
Anthropometric data such as weight, height, or length are not always easily obtainable
in the ICU, and they're not always accurate due to other compounding factors in the ICU.
Additional anthropometric data, if able to be obtained by a skilled clinician, include
triceps skinfold measurements, or mid-arm circumference measurements, which can better
assess the patient's baseline body composition, such as their total body fat, or their degree
of malnutrition.
Along with anthropometric data, the physical exam of a patient plays a crucial role in
better assessing a patient's clinical baseline nutritional status.
Noting whether a patient is edematous, has any temporal or muscle wasting, or altered
skin integrity may further influence your final goal energy and protein needs.
Weight changes over time, in addition to trends and anthropometric data, remain the gold standard
in determining if your energy goals are accurate.
This is why it is important to obtain these anthropometric measurements on a regular basis.
Just as a patient's clinical status changes in the ICU, so do their energy demands.
Nutritional Needs of Critically Ill Children versus Healthy Children.
The nutritional needs of critically ill children significantly differ compared to healthy children.
More research here at Children's has shown that the energy demands of a critically ill
child are significantly reduced.
Factors that are contributing to this include patients being on bed rest, they're commonly
on sedation medications and chemical paralysis, along with being on mechanical ventilatory
support, which significantly reduces their energy demands.
Also if a patient is receiving parenteral nutrition support, it is thought that the
thermic effect of food is reduced by about 10% because the body is not using any energy
to digest and absorb the macro-nutrients.
If energy needs are incorrectly assessed a patient becomes at risk for being underfed
or overfed which can further complicate a patient's clinical condition, such as length
of stay in the ICU, days on mechanical vent support, or they also may become at increased
risk for infections.
Based on these metabolic factors playing a role in a patients energy demands, here at
Children's we estimate a resting energy expenditure, or REE, using the equations WHO or Schofield.
We then use a stress factor that we multiply to result in a number that we call total energy
expenditure.
The stress factor that we commonly use here ranges from 1 to 1.3, but can be as high as
2 if a patient is a status post to trauma or thermal injury, as well as if a patient
needs to undergo nutrition rehab, such as catch-up growth.
Point of clarification, depending on the individual patient, a stress factor may not always need
to be applied when estimating energy needs.
Patients may also have changing energy needs during different stages of their illness.
The RDA and DRI equations overestimate energy needs in a critically ill child, therefore,
are rarely used here at the hospital in the ICU setting.
Indirect Calorimetry remains the gold standard when attempting to assess Basal energy needs
and should be considered for a patient that is undergoing metabolic derangements in the
ICU.
Indications for Parenteral Nutrition.
Next I will be talking about parenteral nutrition support, or here at Children's the abbreviated
version called PN.
It is important to first identify the appropriate circumstances when PN should be used as a
primary form of nutrition support.
Generally, this includes patients that are on bowel rest, have altered bowel function
related to medical or surgical conditions, and anticipate being unable to be enterally
fed for greater than five or more days.
For infants, or severely malnourished patients, our threshold to starting PN is closer to
three days.
Once PN is deemed appropriate, we then identify the IV access the patient has.
This will determine the PN solution you are able to infuse.
Preferably here at Children's, the tip of the central venous line should be in a large
vessel, such as the right atrium or the superior vena cava, where the venous flow is at its
maximum and can handle a concentrated solution.
If a patient only has peripheral IV access, the challenge becomes meeting their energy
needs because the concentration is limited to not exceed 900 mOsm per liter, which usually
correlates to a PN solution of a dextrose of 10% and a 2% amino acid solution with standard
additives.
The next step in initiating PN is reviewing the patient's fluid status and electrolyte
trends.
Here at Children's Hospital Boston, we estimate fluid requirements using the Holiday-Segar
Method.
As a patient is initiating on PN and being maintained on PN, monitoring hydration status
closely is very important as fluid needs may change, depending on a patient's clinical
condition.
A patient may require increased fluids if they have insensible losses such as being
persistently febrile or if they have increased losses via stool or nasogastric tubes.
Also, a patient may require a concentrated fluid for their PN if they are becoming fluid
overloaded.
Here at Children's, our PN solution is a two in one, where our lipids are infused separately.
We also dose our contents of our PN per liter.
Our three macronutrients included in our PN solution consists of carbohydrate, being dextrose
with a 3.4 calorie per gram, proteins, which is a crystalline amino acid, which is 4 calories
per gram, and fat, which is a soybean safflower emulsion, which is a 20% solution, 2 calories
per milliliter.
In terms of dextrose, we look at it as being our primary source of calories in our PN.
And we use a glucose infusion rate or GIR as our measurement to help initiate and advance
the PN solution.
It is recommended here of starting a glucose infusion rate of around 5 milligrams per kilogram
body weight per minute.
We then will advance the GIR by a range of 2 to 5 milligrams per kilogram per minute,
which equals a 5% to 10% dextrose increase.
The upper limit for the GIR varies depending on age.
For infants, the upper limit for the glucose infusion rate is anywhere from 10 to 14 milligrams
per kilogram per minute.
For children ages 1 to 10 we do not like to exceed a GIR of greater than 10.
And for adolescents we do not like to exceed a GIR of greater than 6.
When advancing the GIR and PN, we closely monitor blood sugar levels, as well as urine
lights, making sure that there is no glucose noted in the urine.
In terms of protein, we do not like to use it as a primary fuel source as we do with
carbohydrates, but instead dose it appropriately to prevent further loss of lean body mass.
Our protein, our crystalline amino acids, contains a combination of essential, semi-essential,
and non-essential amino acids with the combinations varying depending on the age of the patient.
For infants we use the solution TrophAmine and for children greater than the age of one,
we use the solution Aminosyn.
In terms of initiating the protein in the PN, for infants we initiate protein at 2 grams
per kilogram body weight, and for children and adolescents we initiate protein at 1 gram
per kilogram body weight.
With advancement we increase protein by 1 gram per kilogram body weight every day to
our desirable upper ranges.
For infants the upper range of protein is 3 to 4 grams per kilogram body weight per
day.
For children our range of protein is 1.5 to 2.5 grams per kilogram per day.
And for adolescents our range is 1 to 1.5 grams per kilogram per day.
It is also important to take note though the instances where children will require more
or less protein outside of these ranges.
Such as a patient that is status post-trauma or with open wounds requiring increased protein,
or if a patient is showing signs of developing renal failure requiring less protein.
We however, do not like to go lower than the RDA for protein to again, prevent further
lean body mass loss.
With our fat source being a 20% solution called Intralipid, it contains a combination primarily
more of omega 6 fatty acids to prevent essential fatty acid deficiency.
We initiate the lipids for all ages here at Children's at 1 gram per kilogram per day.
And we'll advance by 1 gram per kilogram to again, our desirable upper ranges based on
the patient's age.
For infants, our upper limit for lipid dosing is no higher than 3 grams per kilogram per
day.
For children ages 1 to 10 it's a range of 1.5 to 2.5 grams per kilogram per day.
And for adolescents we do not like to exceed a dose of 1.5 grams per kilogram per day.
We recommend prior to initiating lipids obtaining a fasting triglyceride level to ensure optimal
tolerance.
And depending on the dosing of the lipid and the length of time they are on PN, we also
like to monitor essential fatty acid panels.
The next component of our PN solution consists of our electrolytes and additives.
The standard electrolytes we include in our PN solution here at Children's includes sodium,
potassium, phosphorus, chloride, magnesium, and calcium.
Our sodium standard ranges from 2 to 4 milliequivalents per kilogram, and our potassium and chloride
ranges from 2 to 3 milliequivalents per kilogram body weight.
We strongly recommend correcting any electrolyte derangements prior to the initiation of PN,
as it is very difficult to manage electrolyte shifts once the PN is infusing.
And any acute changes in PN rate or volume can adversely affect macronutrient metabolism,
such as hypoglycemia or hyperglycemia.
Patients again, may require additional or less additives in electrolytes based on their
clinical condition.
If they are going into renal failure, they may require less potassium, phosphorus.
If they have increased losses via a nasogastric tube or stool, they may require increased
amounts of sodium or potassium.
PN advancement is strongly dependent on laboratory data, which is why we closely follow daily
chemistries while they are advancing on PN.
And once they are at goal calories via PN, we follow weekly PN profile labs to ensure
continued tolerance.
On average, our patients reach goal energy needs via PN by day three or four.
It may take longer, closer to five to seven days, if a patient is at increased risk for
refeeding syndrome.
But again, laboratory data closely determines our advancement plan with PN.
If a patient is on PN greater than one month and continues to receive minimal or no enteral
nutrition, we also monitor long term nutrition labs to determine if additional micronutrients
such as selenium or carnitine should be added to our PN solutions, or if increased amounts
of our micronutrients, such as zinc or copper should also be included.
That concludes my lecture on estimating energy needs in a critically ill child and parenteral
nutrition support.
Thank you for your time.
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