Page 619 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Parenteral Nutrition 607

TABLE 25-1 Summary of Five Retrospective Studies on Parenteral Nutrition (PN) in
Dogs and Cats
Lippert Reuter Chan Pyle Crabb

Years included in study 1985-1989 1988-1995 1994-1999 1994-2001 1991-2003
Dogs included (n) 72 209 80 0 0
Cats included (n) 12 0 47 75 40
Major indication Gastrointestinal Pancreatitis Pancreatitis Pancreatitis Hepatic
Duration of PN in days (median [range]) 3.8 (1-14) 3.5 (0.5-25) 3.0 (0.3-8.8) 4.8 (0.5-18.5) 3.7 (0.3-9.5)
Weight change (mean) 3-4% 0.2 kg 0.3 kg 0.23 kg (n ¼ 25) 0.0 kg
Mechanical complications (number) 39 118 25 19 12
Hyperglycemia (%) 37 32 15 47 23
Septic complications (%) 7 7 4 0 0
Total complications (per day of PN) 0.42 0.52 0.16 0.62 0.29
Survival (%) 70 51 73 48 60

This increasing number of studies has been helpful in bet- of lean body mass in an ill or injured animal will occur,
ter understanding the metabolism of parenteral amino to a certain degree, even if the animal is provided with
acids in companion animals and will serve as a foundation adequate calories. However, appropriate nutritional sup-
on which to base future research into the specific port can minimize the amount of lean body mass lost and
requirements of ill and injured animals. the sequela of this loss. Therefore the goal of nutritional
support in the hospitalized animal should be not only
RATIONALE FOR treatment of those that are already malnourished but also
NUTRITIONAL SUPPORT IN minimizing the development of malnutrition in animals
HOSPITALIZED ANIMALS at risk.

Ill and injured animals undergo metabolic changes that PATIENT SELECTION
put them at high risk for malnutrition and its subsequent
complications. In a healthy animal that receives insuffi- Any route of nutritional support carries some risk of
cient calories to meet its needs, the body compensates complications, and parenteral nutrition is not an excep-
for this calorie deficit in the short term by first using tion. Studies in people have shown that parenteral
hepatic glycogen and then by mobilizing amino acids nutrition in some patient populations actually increases
from muscle. Glycogen stores are rapidly depleted, partic- the risk of complications and worsens the outcome.*
ularly in carnivores such as cats. Although these processes Therefore careful patient selection is particularly impor-
can provide needed energy, they are inefficient energy tant in the case of parenteral nutrition. Ideally, one would
sources; therefore after several days, the healthy animal select only those patients that would benefit from paren-
adapts by decreasing protein turnover and preferentially teral nutrition, but the appropriate selection criteria are
using fat. By this process, a healthy animal can survive not yet known in people or in companion animals. Most
for a long period without food, provided that adequate companion animals receive parenteral nutrition for rela-
water is available. In the ill or injured animal, however, tively short periods (median, 3 to 4 days), and one must
this normal adaptive response to a calorie deficit does determine whether short-term provision of parenteral
not occur, primarily as a result of alterations in the nutrition is likely to be beneficial. Occasionally, parenteral
cytokine and hormonal milieu that are associated with nutrition is administered for more prolonged periods,
the catabolic response. Thus these animals continue to and as always the risk/benefit ratio must be considered.
mobilize protein, perpetuating the loss of lean body mass. In a previously healthy dog that has been anorectic for
The problem with this continued loss of lean body 2 to 3 days and in which oral or enteral intake is likely
mass is that all of the body’s protein is functional tissue, to resume quickly, parenteral nutrition may not be
as compared with fat and carbohydrate, both of which beneficial. However, in a vomiting cat that has not eaten
have storage depots. In addition, loss of lean body mass for 1 week at home and is not expected to be eating again
negatively impacts wound healing, immune function, soon, parenteral nutrition would be indicated.
strength (both skeletal and respiratory muscle), and ulti- The indications for parenteral nutritional support are
mately prognosis. Although it has not been demonstrated situations in which an animal cannot voluntarily consume
in companion animals, hospitalized people with weight
loss have a worse outcome than those without. A loss *References 8, 24, 29, 32, 64, 70.