total parentral nutrition

[abu3li]

Parenteral nutrition (PN) is feeding a person
intravenously , bypassing the usual process of
eating and digestion. The person receives
nutritional formulae that contain nutrients such
as glucose , amino acids , lipids and added
vitamins and dietary minerals. It is called total
parenteral nutrition (TPN) or total nutrient
admixture (TNA) when no significant nutrition is
obtained by other routes. It may be called
peripheral parenteral nutrition (PPN) when
administered through vein access in a limb,
rather than through a central vein.
History
Developed in the 1960s by Dr Stanley J.
Dudrick, who as a surgical resident in the
University of Pennsylvania, working in the basic
science laboratory of Dr Jonathan Rhoads, was
the first to successfully nourish initially Beagle
puppies and subsequently newborn babies with
catastrophic gastrointestinal malignancies. [1] Dr
Dudrick collaborated with Dr Willmore and Dr
Vars to complete the work necessary to make
this nutritional technique safe and successful. [2]
Mechanism
A mechanical pump under computer control is
used to dispense the TPN fluid. Pumps are
available that allow TPN administration at home,
usually with the preparation and attachment by
a family member. These pumps operate on an
external dispensing line, part of a single-use
dispensing cassette. Connection of the
dispensing line to the patient is via a valve on a
semi-permanent attached venous port whose
closure is displaced by a connection on the
dispensing line. Preparation, attachment, and
valve replacement require care in sanitation and
sterile techniques at specific locations. The use
of a rechargeable battery and a portable
component pack allows a convenient household
mobility for many patients during administration
periods, these being typically from twelve to
sixteen hours a day.
Indications
Total parenteral nutrition (TPN) is provided
when the gastrointestinal tract is nonfunctional
because of an interruption in its continuity (it is
blocked, or has a leak - a fistula ) or because its
absorptive capacity is impaired. [3] It has been
used for comatose patients, although enteral
feeding is usually preferable, and less prone to
complications. Parenteral nutrition is used to
prevent malnutrition in patients who are unable
to obtain adequate nutrients by oral or enteral
routes. [4]
Gastrointestinal disorders
TPN may be the only feasible option for
providing nutrition to patients who do not have
a functioning gastrointestinal tract or who have
disorders requiring complete bowel rest,
including bowel obstruction, [5] short bowel
syndrome , [5] Gastroschisis , [5] prolonged
diarrhea regardless of its cause, [5] high-output
fistula , [5] very severe Crohn's disease [5] or
ulcerative colitis, [5] and certain pediatric GI
disorders including congenital GI anomalies and
necrotizing enterocolitis. [6]
Use in cancer
The benefit of TPN to cancer patients is largely
debated, and studies to date have generally
showed minimal long term benefit. There is no
evidence to support the idea that intravenous
nutrition 'feeds the cancer, not the
patient'. [ citation needed ]
Duration
Short-term PN may be used if a person's
digestive system has shut down (for instance
by peritonitis ), and they are at a low enough
weight to cause concerns about nutrition during
an extended hospital stay. Long-term PN is
occasionally used to treat people suffering the
extended consequences of an accident, surgery,
or digestive disorder. PN has extended the life
of children born with nonexistent or severely
deformed organs.
Living with TPN
Approximately 40,000 people use TPN at home
in the United States, and because TPN requires
anywhere from 10–16 hours to be
administered, daily life can be affected. [7]
Although daily lifestyle can be changed, most
patients agree that these changes are better
than staying at the hospital. [8] Many different
types of pumps exist to limit the time the
patient is “hooked-up”. Usually a backpack
pump is used, allowing for mobility. The time
required to be connected to the IV is dependent
on the situation of each patient; some require
once a day, or five days a week. [7]
It is important for patients to avoid as much
TPN related change as possible in their
lifestyles. This allows for the best possible
mental health situation; constantly being held
down can lead to resentment and depression.
Physical activity is also highly encouraged, but
patients must avoid contact sports (equipment
damage) and swimming (infection). Many teens
find it difficult to live with TPN due to issues
regarding body image and not being able to
participate in activities and events. [7]
Complications
TPN fully by-passes the GI tract and normal
methods of nutrient absorption. Possible
complications, which may be significant, are
listed below.
Infection
TPN requires a chronic IV access for the
solution to run through, and the most common
complication is infection of this catheter.
Infection is a common cause of death in these
patients, with a mortality rate of approximately
15% per infection, and death usually results
from septic shock . [9]
Blood clots
Chronic IV access leaves a foreign body in the
vascular system, and blood clots on this IV line
are common. [10] Death can result from
pulmonary embolism wherein a clot that starts
on the IV line but breaks off goes into the
lungs. [11]
Micrograph of periportal fatty liver as
may arise due to TPN . Trichrome stain .
Patients under long-term TPN will typically
receive a periodic heparin flush to dissolve
such clots before they become dangerous.
Fatty liver and liver failure
Fatty liver is usually a more long term
complication of TPN, though over a long
enough course it is fairly common. The
pathogenesis is due to using linoleic acid (an
omega-6 fatty acid component of soybean oil)
as a major source of calories. [12] [13]
Hunger
Because patients are being fed intravenously,
the subject does not physically eat, resulting in
intense hunger pangs. The brain uses signals
from the mouth (taste and smell ), the stomach/
G.I. Tract (fullness) and blood ( nutrient levels)
to determine conscious feelings of hunger. [14]
In cases of TPN, the taste, smell and physical
fullness requirements are not met, and so the
patient experiences hunger, despite the fact that
the body is being fully nourished. In cases
where the patient eats food despite the inability,
they can experience a wide range of
complications. [15]
Special Complications in Pregnancy
Pregnancy can cause major complications when
trying to properly dose the nutrient mixture.
Because all of the baby’s nourishment comes
from the mother’s blood stream, the doctor
must properly calculate the dosage of nutrients
to meet both recipient’s needs and have them
in usable forms. Incorrect dosage can lead to
many adverse, hard-to-guess effects, such as
death, and varying degrees of deformation or
other developmental problems . [16]
It is recommended that parenteral nutrition
administration begin after a period of natural
nutrition so doctors can properly calculate the
nutritional needs of the fetus . Otherwise, it
should only be administered by a team of
highly skilled doctors who can accurately guess
the fetus’ needs. [16]
Other complications
Total parenteral nutrition increases the risk of
acute cholecystitis [17] due to complete disuse
of gastrointestinal tract, which may result in bile
stasis in the gallbladder. Other potential
hepatobiliary dysfunctions include steatosis , [18]
steatohepatitis , cholestasis , and cholelithiasis .
[19] Six percent of patients on TPN longer than
3 weeks and 100% of patients on TPN longer
than 13 weeks develop biliary sludge. The
formation of sludge is the result of stasis due to
lack of enteric stimulation and is not due to
changes in bile composition. Gallbladder sludge
disappears after 4 weeks of normal oral diet.
Administration of exogenous cholecystokinin
(CCK) or stimulation of endogenous CCK by
periodic pulse of large amounts of amino acids
have been shown to help prevent sludge
formation. These therapies are not routinely
recommended. [20] Such complications are
suggested to be the main reason for mortality
in people requiring long-term total parenteral
nutrition, such as in short bowel syndrome . [21]
In newborn infants with short bowel syndrome
with less than 10% of expected intestinal length,
thereby being dependent upon total parenteral
nutrition, 5 year survival is approximately 20%.
[22]
Complications are either related to catheter
insertion, or metabolic, including refeeding
syndrome . Catheter complications include
pneumothorax, accidental arterial puncture, and
catheter-related sepsis. The complication rate at
the time of insertion should be less than 5%.
[23] Catheter-related infections may be
minimised by appropriate choice of catheter and
insertion technique. [24] Metabolic
complications include the refeeding syndrome
characterised by hypokalemia,
hypophosphatemia and hypomagnesemia .
Hyperglycemia is common at the start of
therapy, but can be treated with insulin added
to the TPN solution. Hypoglycaemia is likely to
occur with abrupt cessation of TPN. Liver
dysfunction can be limited to a reversible
cholestatic jaundice and to fatty infiltration
(demonstrated by elevated transaminases).
Severe hepatic dysfunction is a rare
complication. [25] Overall, patients receiving
TPN have a higher rate of infectious
complications. This can be related to
hyperglycemia. [26]
Solutions
The nutrient solution consists of water and
electrolytes; glucose , amino acids, and lipids;
essential vitamins , minerals and trace elements
are added or given separately. Previously lipid
emulsions were given separately but it is
becoming more common for a "three-in-one"
solution of glucose, proteins, and lipids to be
administered. [27][28]
Emulsifier
Only a limited number of emulsifiers are
commonly regarded as safe to use for
parenteral administration, of which the most
important is lecithin . [ medical citation needed ]
Lecithin can be biodegraded and metabolized,
since it is an integral part of biological
membranes, making it virtually non-toxic. Other
emulsifiers can only be excreted via the
kidneys, [ citation needed ] creating a toxic load.
The emulsifier of choice for most fat emulsions
used for parenteral nutrition is a highly purified
egg lecithin, [29] due to its low toxicity and
complete integration with cell membranes. [30]
Use of egg-derived emulsifiers is not
recommended for people with an egg allergy
due to the risk of reaction. In situations where
there is no suitable emulsifying agent for a
person at risk of developing essential fatty acid
deficiency, cooking oils may be spread upon
large portions of available skin for
supplementation by transdermal absorption.
Another type of fat emulsion Omegaven is being
used experimentally within the US primarily in
the pediatric population. It is made of fish oil
instead of the egg based formulas more widely
in use. Research has shown use of Omegaven
may reverse and prevent liver disease and
cholestasis. [31]