P–R

parenteral nutrition The intravenous adminis-
tration of NUTRIENTS as a method of supplying
appropriate sustenance to a person who cannot
meet his or her NUTRITIONAL NEEDSby eating, such
as someone who is in a COMAor has a severe swal-
lowing disorder. Parenteral nutrition, called total
parenteral nutrition (TPN) when it is a person’s
sole source of nutrition, is helpful for short-term,
intense feeding when ENTERAL NUTRITIONis not a
viable option. Parenteral nutrition is most success-
ful as temporary supportive treatment such as
after extensive surgery or during recovery from
major trauma, though sometimes is necessary for
longer therapy such as in severe gastrointestinal
disease or cancer. In the long term, however, par-
enteral nutrition cannot deliver all of the nutrients
the body needs and, in particular, is lacking in its
ability to supply lipids (fats), which the body
requires for cell maintenance and energy.
Parenteral nutrition solutions are very irritating
to the veins so must be infused into the larger
veins deep in the chest. This requires the doctor to
insert a percutaneous intravenous catheter (PIC
line) into a VEINin the arm and thread it through
the smaller vein to a large vein. An alternative is a
Hickman line, in which the intravenous catheter
enters the jugular vein at the base of the neck and
extends into the superior VENA CAVA, the largest
vein in the upper body. Fluids run continuously
into either line with the aid of an infusion pump
to maintain delivery of the solution at constant
rate and pressure.
Some of the complications of extended par-
enteral nutrition include LIVER FAILURE, RENAL FAIL-
URE, NUTRITIONAL DEFICIENCY (notably of trace
minerals and lipids), and MALNUTRITION. INFECTIONis
also a significant risk, partly because the
indwelling catheter provides a pathway for BACTE-

RIAto enter the body and partly because the con-

tent of parenteral nutrition solutions is very high

in GLUCOSE, which attracts and feeds bacteria.

See also END OF LIFE CONCERNS; QUALITY OF LIFE;

SWALLOWING DISORDERS.

pellagra A health condition resulting from long-

term deficiency of niacin (vitamin B 3 ). Pellagra is

uncommon in the United States, occurring pri-

marily in people who have chronic ALCOHOLISMor

gastrointestinal disorders that prevent absorption

of dietary niacin (also called niacinamide, nicoti-

namide, nicotinic acid, or niacinic acid) or of the

essential amino acid tryptophan. The body

requires niacin for cellular METABOLISM. Trypto-

phan is a niacin precursor from which the body

can synthesize niacin. Niacin is necessary for the

energy conversions that take place during cellular

metabolism.

Symptoms and Diagnostic Path

Early symptoms of pellagra are those of nonspe-

cific gastrointestinal upset: NAUSEA, VOMITING, and

DIARRHEA. Burning in the MOUTHand especially of

the tongue is common, with a characteristic gray

membranous tissue coating on the gums that con-

tinually sloughs or peels. As pellagra worsens,

additional symptoms that appear include GLOSSITIS

(inflamed tongue) and SKIN RASH that intensifies

with sun exposure after which the skin becomes

rough, thick, and discolored. A characteristic pat-

tern of this damage often develops around the

neck.

At the same time, the lack of niacin causes the

mucosa (mucous membrane lining) of the gas-

trointestinal tract to deteriorate, progressively

reducing the ability of the intestines to absorb

nutrients; MALNUTRITIONresults. Niacin deficiency

198