Download ER and ICU Nutrition - Pennsylvania Veterinary Medical Association

ER and ICU Nutrition
Tony Johnson, DVM, DACVECC
Veterinary Information Network (VIN)
Email: [email protected]
{3 Rivers Conference Nov 2016}
Introduction: Nutritional support is often overlooked in managing ER and ICU case – our patients are
quite literally starving to death in some cases. This manuscript will cover how to incorporate nutritional
support (both enteral and parenteral) in managing ER/ICU cases. This session will focus on real-world
fixes, and relies more on therapy and diagnosis than pathophysiology. Specific points that I feel are of
importance are highlighted in bold, and are intended to allow for easy scanning of this manuscript in the
heat of battle with the forces of disease. Many of the techniques and tests discussed below are based on
anecdotal reports and experience rather than solid evidence-based medicine. Interested attendees are
lovingly directed to large and boring tomes on internal medicine for further study.
When formulating a nutritional plan, it is important to decide if enteral or parenteral nutrition will be
started first. The preferred method of providing nutritional support to an anorexic patient is (voluntary)
enteral nutrition. There are many benefits of using the GI tract to assimilate nutrients: maintenance of
mucosal integrity and avoidance of bacterial translocation from the GI tract into the circulation first and
foremost. The rule of thumb – if the gut works, use it – may seem overly simplistic, but can help
veterinarians, staff and owners understand the rationale for the choice of one form of nutritional support
over another.
Enteral Nutritional support:
This portion of the handout will help you evaluate the nutritional needs of your patient and formulate a plan
for their enteral nutritional requirements in the ER and ICU. Many times, the nutritional status of the patient
is forgotten during the course of a patient’s illness and hospitalization. We expect them to heal from illness
or injury with only the resources they had at the initiation of their case. They may be in the hospital, treated
very aggressively with medications, IV fluids, surgery, oxygen etc., but many (probably MOST) of the
patients are anorexic. Providing nutrition can be as vital to these patients as all of the other interventions
put together! I will focus here mostly on tube feeding, primarily nasoesophageal or NE. NE tubes are easy
to place and use in any practice and can be really lifesaving for your anorexic patients.
But before we delve into providing nutrition to our patients, let’s take a step back and look at nutrition in
general for a moment.
For our purposes today, we will consider 3 main categories of nutritional elements: amino acids/proteins,
carbohydrates and lipids. As we come up with treatment plans for our patients, it is these 3 elements that we
will incorporate.
First - Protein
Provision of dietary protein is important because the body constantly needs to synthesize new structural
proteins (e.g, muscle, connective tissue). Additionally, the body may use amino acids for energy by first
converting them to glucose in a process called gluconeogenesis. Unfortunately cats are not able to
downregulate gluconeogenesis and therefore will break down their own muscle protein if they are not fed
any protein.
Dogs should be supported with 4-6 grams of protein/100 kcal (15-25% of total energy requirements),
while cats need 6 grams of protein/100 kcal (25-35% of total energy requirements). Patients with protein
intolerance, e.g., hepatic encephalopathy, severe azotemia should receive reduced amounts of protein; in
dogs this is usually 2-3 grams of protein/100 kcal and 4 grams of protein/100 kcal for cats.
Next - Carbohydrates
Carbohydrates are an important source of readily available energy. Carbohydrates are of vital importance
to the brain as it cannot convert other nutrients, like amino acids to carbohydrates – it must have them in
pure form. This is one of the reasons why hypoglycemia causes mental dullness and seizures.
Last - Lipids
Fats provide essential fatty acids which are extremely important for the maintenance of cellular membranes,
the synthesis of hormones and most importantly, a concentrated source of energy. When we provide
nutritional support to our patients, sometimes as much as half of the total daily calories can be provided in
the form of lipids.
Classically, the consequences or poor nutrition and starvation are
 Delayed wound healing
 Immunosuppression
 Contributing to bacterial translocation from the gut
 Decreased energy, mental depression
Many owners inquire about appetite stimulants such as cyproheptadine and mirtazapine. The downside to
appetite stimulants is that they delay appropriate nutritional intervention until catabolism has progressed
and the side effects of anorexia and malnutrition have become very advanced – we have a lot more ‘catch
up’ to play. They may also have undesirable side effects such as sedation or hepatic necrosis. It is
important to limit the use of appetite stimulants to a short trial in patients who have not experienced a
prolonged period of anorexia, or to those cases where other alternatives have been declined.
Force feeding deserves special attention, as it not only is unlikely to provide sufficient nutrition to meet
patient needs, the sheer struggle associated with it can lead to an uncooperative patient
Force feeding can lead to a food aversion and worsen the patient’s chances of eating on their own - this
problem can be particularly pronounced in cats! While it may be tempting to try this tactic, it should be
avoided and another method of providing nutrition sought.
Nutrition Assessment
All patients should have a nutritional assessment performed to determine the need for additional nutritional
therapy – this will help us determine who we should feed.
As a (very) general rule, anorexia of 3 to 5 days duration or loss of more than 10% of body weight are
indications for starting nutritional therapy as part of the treatment plan. The importance of not delaying
any longer than this is that negative effects on immune function can already be detected after 4 days of
food.
There is really only one good reason to delay nutritional intervention in a clearly malnourished patients and
that is major abnormalities in the major body systems (cardiovascular, respiratory or neurological systems).
In such cases, patients must be stabilized first. Correcting fluid deficits, major acid-base and electrolyte
abnormalities are recommended before starting nutrition.
Now let’s look at ‘how?’
In general the patient’s diagnosis and the degree of functionality of the gastrointestinal (GI) tract will also
help make the determination of which form of nutritional support will be used. There are many benefits of
using the GI tract to assimilate nutrients: maintenance of mucosal integrity and avoidance of bacterial
translocation from the GI tract into the circulation first and foremost. If the patient can reasonably be
expected to tolerate enteral nutrition, this is the best way to address their dietary needs, but if they have a
nonfunctional GI tract due to protracted vomiting, surgery or illness then parenteral nutrition will be
necessary until they can be transitioned to enteral nutrition in some form.
Let’s now look at HOW MUCH we will feed.
Many of us were taught to first calculate the resting energy requirement (RER) and then multiply this
amount by an illness energy factor. This results in overfeeding most patients, leaving scads of unneeded
metabolic substrate around and can lead to complications like diarrhea and hyperglycemia. So we typically
don’t adjust the RER upwards anymore – which makes our lives simpler.
For patients >2kg and <30kg (like our patient, who is weighing in at 4kg) the resting energy requirement
can be calculated as
(BW (in kilograms) X 30) + 70
For patients greater than 30kg or less than 2kg the following formula can be used:
RER = 70 x (body weight in kg)0.75.
The caloric density of the diet being fed is necessary to calculate the volume for each feeding
Feedings are usually started at 1/4 to 1/3 of RER and increased in daily increments until full RER is
reached.
NE tubes
Since NE tubes are for pretty short-term, inpatient use, we typically don’t send patients home with them
in place. Both NE and NG tubes are usually used for hospitalized patients since they require frequent
flushing and frequent monitoring to prevent tube dislodgement. The main risk is inadvertent placement in
the trachea. This can be disastrous, and owners need to be apprised of this risk.
An Elizabethan collar is nearly always needed to prevent pulling of the tube by the patient.
They are relatively contraindicated in coagulopathic patients due to the risk of inducing epistaxis, Feedings
can commence immediately after placement.
Tube Placement – Nasoesophageal/Nasogastric
NE and NG tubes can be generally placed in awake patients. Fractious animals may require procedural
sedation with an alpha-2 agonist (in cardiovascularly stable patients), combination of a sedative such as
diazepam or acepromazine and an opioid, or propofol.
The largest tube that can usually be placed in a cat’s nose is an 8 French tube. Tubes of 8-10 Fr can be used
in dogs if they are of appropriate length. The tube should extend to just proximal to the 8th -10th rib to avoid
entry into the stomach. The 13th rib is identified and the tube measured and marked to correspond to the 810th rib
2-3 drops of topical local anesthetic (such as proparacaine) are instilled into the intended nostril. With the
patient in sternal recumbency and the patient’s head in normal position, the tube is directed ventrally and
medially in an attempt to cause the tube to enter the ventral meatus. If the tube is introduced and meets
resistance after passing a short distance, it has likely passed into the dorsal meatus and is abutting on the
cribriform plate. Some patients can be observed to swallow as the tube enters the pharynx. If the patients
begin coughing, the tube may have inadvertently entered the trachea. Once the length marks have been
reached, the tube is secured to the lateral aspect of the muzzle with tape butterflies and suture. Tube
placement can be confirmed by several methods:
1. A lateral and VD radiograph
2. Attaching a syringe and aspirating on a properly placed NG tube will produce negative pressure as the
side of the esophagus will be sucked against the tube. A tube placed in the trachea will continue to
draw air.
3. Attaching an end-tidal CO2 monitor (ETCO2) monitor to a properly placed tube will read zero (there
is minimal CO2 in room air) while one attached to one that has been inadvertently placed in the
trachea will detect CO2.
4. In most awake patients, injecting 2-3cc of sterile water or saline will stimulate a cough if the tube has
been inadvertently placed in the trachea.
Remember – none of these methods are 100% foolproof. It is best to use several means to check tube
placement, and always warn owners of the risks.
Tube Complications and Troubleshooting
Tube dislodgement is a common complication for NE tubes, and can be avoided by securing the tube to
the muzzle and using an Elizabethan collar. Tube obstruction can be managed by attempting suction or
flushing of the tube first. If that fails, a carbonated beverage such as a soft drink, can be flushed into the
tube under pressure while the injection port is occluded. The carbonation will expand and may push the
obstruction into the gastric lumen.
PARENTERAL NUTRITION:
Parenteral Nutrition or PN should be considered as part of a treatment plan when
nutritional support via the gut is not possible. “PN” is:



More expensive than enteral nutrition
Only for in-hospital use
Generally composed of
o a carbohydrate source (dextrose)
o a protein source (amino acids)
o a fat source (lipids)
o +/- vitamins and trace metals
Indications
 Intractable vomiting
 Acute pancreatitis
 Severe malabsorptive disorders
 Severe ileus
 Recent GI surgery or trauma
TPN vs. PPN
Parenteral nutrition is divided into total and partial parenteral nutrition based on what portion of patient
caloric needs are met
Total Parenteral Nutrition (TPN):
 Typically delivered via a central venous (jugular) catheter
 Hyperosmolar – usually 1100-1500 mOsm/L
 Formulated to meet 100% of energy requirements
 Appropriate for long term support
 Typically must be compounded or delivered by an outside source
Partial Parenteral Nutrition (PPN):
 Peripheral or central administration; because of lower osmolarity of solution, can usually be
administered through a large peripheral vein, such as
o lateral saphenous in canines
o femoral vein in felines
 Usually formulated to meet 50 – 70% of patient’s nutritional requirements
 Intended for short-term use (< 5 days)
 Given in conjunction with enteral nutrition
 Not for severely malnourished patients
 Commercially available “off the shelf” solutions available (ProcalAmine™, etc.)
General Administration
 Requires a dedicated line placed using aseptic technique
 Catheter and lines must be handled with aseptic technique to avoid complications
 Long catheter preferable
 Silicone, polyurethane or tetrafluoroethylene catheter composition recommended, as these reduce
the risk of thrombophlebitis
 Multi-lumen catheter may be useful for blood sampling and administering other fluids and
medications
 TPN and PPN must be mixed sterilely (hence often formulated by outside source)
 Should be instituted gradually over 48-72 hours
 Adjust other intravenous fluids accordingly for amount of fluid being administered in parenteral
nutrition to avoid volume overload
Commercial ready to use preparations
 Glucose and amino acid solutions only provide < 50% of required calories when administered at
maintenance fluid rate
 Should only be used for short-term or interim nutritional support
 Note: solutions such as ProcalAmine™ contain maintenance levels of potassium and this limits
administration to rates of 2-4ml/kg/hr
Central Catheterization Options
The chosen site is clipped, scrubbed and draped, sterile gloves are worn and aseptic technique is used
 Over the wire (modified Seldinger) technique
o Uses a wire introduced into vessel through a needle to guide catheter
o Once venipuncture is made (see illustration below, Step 1), wire is introduced into vein (2).
o A vessel dilator (3) can be used to widen hole in vessel and make introduction of catheter
easier.
o Dilator is slipped over wire and introduced into vessel with a twisting motion.
o Dilator is then removed and catheter (4) is passed down wire and placed into vessel.
o Catheter is aspirated to remove air, flushed with saline and secured to skin.
o A light wrap may be placed, but is not necessary.
o Radiographs are usually taken afterwards to confirm placement.
Other techniques
 Peel-away introducer
 Through-the-needle catheter (such as Venocath™)
Formulation of Nutrient Mixtures
There are two sets of criteria for determining dose of TPN or PPN
TPN:
 TPN is based on patient’s protein requirements
 The non-protein calories are subtracted from that and then divided equally between carbohydrates
and lipids
PPN:
 Total RER is reduced by a certain percentage (usually decreased by 30% compared to TPN) and
then divided into portions of amino acids, lipids and carbohydrates based on patient’s body weight.
Some authors do not account for calories provided by amino acids when formulating parenteral nutrition,
i.e., the total amount of prescribed calories are met with lipids and carbohydrates.



In theory, if all calorie requirements are met with carbohydrates and lipids, then all of the amino
acids provided can be used for protein synthesis.
This approach is controversial with little supporting evidence and many of the complications
associated with parenteral nutrition may be related to excessive calories, high lipid and high
dextrose content
Therefore, the approach taken here is to account for the calories provided by amino acids.
Total Parenteral Nutrition
For TPN, initial calculations involve patient’s protein requirements, which will determine volume of amino
acid solution infused:
I: Protein requirements
Canine
Standard
5g/100 kcal
Feline
6g/100 kcal
Decreased 2-3g/100 kcal 3-4g/100 kcal
Increased
6g/100 kcal
6g/100 kcal
 (RER/100) x ___ g of required protein/100 kcal = grams of protein per day
The volume of amino acid solution can be determined by the percentage of amino acid contained in the
stock bottle (most solutions are 8.5% or 0.085 g protein per mL):

(___ g protein/day) / 0.085 g/mL = mL of amino acids per day
II: Non-protein calories
The calories supplied by the amino acid solution are calculated (each gram of protein provides 4 kcal) and
this is subtracted from the total RER to give the non-protein calories (NPC):

Non-protein calories (NPC) = RER - [(g protein/day)x 4 kcal/g] = non-protein calories
Non-protein calories are usually provided as 50:50 ratio of 50% dextrose and 20% lipid


(NPC x 0.5) = lipid kcal
(NPC x 0.5) = dextrose kcal
The volume of lipid and dextrose are then calculated:


Lipid kcal /(2 kcal/mL) = mL per day of lipid
Dextrose kcal /(1.7 kcal/mL) = mL per day of dextrose
III: Additives
To meet 100% of nutritional requirements, TPN also requires addition of vitamins and minerals in the
following proportions:



Trace minerals (Abbott Laboratories, North Chicago, IL)
Zinc, copper, manganese and chromium (Dose 0.1 mL/kg/day)
Standard B-vitamin complex (Dose 2 mL/L of PN solution)
IV: 24-hour volumes and rate:
Overall requirements for 24 hours’ worth of TPN will be comprised of:
___ mL 8.5% amino acid solution
___ mL 20% lipid solution
___ mL 50% dextrose
Which, when added, give:
___ mL total volume of TPN solution/24 hrs
Which, when divided by 24, gives:
___ mL/hr infusion rate
Partial Parenteral Nutrition
1. Calculate the resting energy requirement (RER)
 For patients >2 kg and <30 kg the resting energy requirement can be calculated as:
(BW (in kilograms) X 30) + 70
This gives the number of KCAL per day required by an animal at rest.
 For patients greater than 30 kg or less than 2 kg the following formula can be used:
RER = 70 x (body weight in kg) 0.75
2. Illness energy requirements are no longer advocated due to risk of overfeeding.
3. Calculate Partial Energy Requirement (PER) – this will meet the percentage of RER that you wish to
meet with PPN. In the examples below, 0.7 is used to derive PER.
Patients 3 to 10 kg:
 PER x 0.25 = ___kcal/day dextrose
 PER x 0.25 = ___kcal/day from amino acids
 PER x 0.50 = ___kcal/day from lipids
Patients 10 to 25 kg:



PER x 0.33 = ___kcal/day dextrose
PER x 0.33 = ___kcal/day from amino acids
PER x 0.33 = ___kcal/day from lipids
Patients > 25 kg
 PER x 0.50 = ___kcal/day from dextrose
 PER x 0.25 = ___kcal/day from amino acids
 PER x 0.25 = ___kcal/day from lipids
The volumes for each portion of the mixture can be derived by the same guidelines as for TPN above. This
volume is then administered over 24 hours to determine the fluid rate.
Complications
PN complications can be divided into mechanical, metabolic and infectious/septic.
 Mechanical complications include
o Catheter occlusion
o Line separation
o Thrombophlebitis due to the catheter
 Metabolic complications include
o Lipemia
o Electrolyte abnormalities
o Hyperbilirubinemia
o Hyperammonemia.
o Hyperglycemia
 a common complication of PN administration
 can either be managed by decreasing the dextrose portion of the PN solution,
decreasing the rate of PN administration or by the administration of regular insulin
as need to keep the BG in the range of 160-180mg/dl. (Tight glycemic control with
insulin in non-diabetic patients is not well described in veterinary patients, but it is
perhaps sensible that one should avoid hyperglycemia whenever possible).
 Septic complications (including, fever, catheter infections, endocarditis and septicemia) can occur
due to
o fertile environment provided by solutions
o possible immunosuppression due to primary disease
To Guard Against Infection
 Bags should be used within 24 hours due to risk of bacterial contamination
 Fluid lines must not be disconnected (e.g. – during a walk or owner visit)
 All fluid lines should be changed daily
 Check catheter site daily and rewrap
 Replace catheter if signs of thrombophlebitis develop
 Post sign on animal’s cage reminding caregivers of special handling requirements of PN patients
Daily monitoring should include
 Serum electrolytes
 Serum chemistries
 Vital signs
 Visual inspection of the catheter area
Updated January 11, 2016