Page 632 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Parenteral Nutrition 619

to adjust the animal’s other intravenous fluids when hypomagnesemia. The shift to carbohydrate metabolism
initiating parenteral nutritional support to prevent fluid increases demand for important cofactors such as thia-
volume overload. mine, which may already be depleted in malnourished
patients, and neurologic manifestations of thiamine
Potential Complications deficiency may occur. 23,55,65 Congestive heart failure also
A number of possible complications can be associated with can occur secondary to fluid shifts. It is important, partic-
parenteral nutrition, and these generally are grouped ularly in animals with prolonged anorexia, to initiate
into one of three categories (Box 25-7). Metabolic parenteral nutrition slowly, to supplement vitamins
complications are the most common, with hyperglycemia (particularly thiamine), and to monitor serum electrolytes
typically seen most frequently. 14,43 Electrolyte for the first 3 to 4 days after initiation.
disturbances can develop either after instituting The most important factor in reducing the risk of
nutritional support or may worsen in animals with mechanical and septic complications is prevention
preexisting abnormalities. Refeeding syndrome is uncom- protocols. Careful attention to catheter placement and
mon in companion animals but can be difficult to manage catheter and line care will reduce the risk of
when it occurs. 3,35 Refeeding syndrome refers to a poten- problems. Placement of catheters by experienced person-
tially fatal complication secondary to nutritional manage- nel has been shown to reduce mechanical and septic
ment of severely malnourished patients. 23,55,63 It includes complications. 43,56 Elizabethan collars should be used
the development of hypophosphatemia with or without for any animal that shows a propensity to chew lines. Cre-
hypokalemia, hypomagnesemia, thiamine deficiency, and ative solutions may be needed for animals that circle in the
fluid shifts. 23,65 It can develop when nutritional support, cage or are otherwise fractious. Protocols for catheter
either parenteral or enteral, is initiated in a severely mal- placement, handling catheters and line with aseptic
nourished animal (particularly those that have not eaten technique, and maintaining dedicated catheters also
for a prolonged period). The glucose provided stimulates are beneficial in minimizing the incidence of sepsis.
insulin secretion that drives extracellular ions (e.g., phos- If clinical evidence of sepsis does develop, conventional
phorus, potassium, magnesium) intracellularly and recommendations include submission of the parenteral
stimulates protein synthesis. The result may be clinically nutrition admixture and the catheter tip for bacteriologic
significant hypophosphatemia, hypokalemia, and cultures. Often, sepsis develops as a result of the

BOX 25-7 Potential Complications of Parenteral Nutrition

Mechanical Hypertriglyceridemia
Line breakage Hypercholesterolemia
Chewed lines Refeeding syndrome (i.e., hypophosphatemia with or
Disconnected lines without hypokalemia and hypomagnesemia)
Perivascular infiltration
Catheter occlusion How to Reduce the Risk
Phlebitis Use a conservative estimate (RER) for initial calculation of
Thrombosis calorie requirements
Initiate TPN gradually
How to Reduce the Risk Monitor glucose and electrolytes daily
Aseptic placement of catheter
Aseptic handling of catheter and lines Septic (Clinical Signs of Sepsis in Conjunction
Use Elizabethan collars for animals that try to chew lines with a Positive Catheter Tip or Blood Culture)
Change bandage and check catheter site daily for swelling, How to Reduce the Risk
erythema, malpositioning of catheter
Maintain a dedicated catheter
Metabolic Catheter composed of materials of low thrombogenicity
Hyperglycemia Placing catheters, handling catheters and lines with aseptic
Hypoglycemia (most common when discontinuing technique
parenteral nutrition, especially if done abruptly) Using parenteral nutrition for the least amount of time
Hyperkalemia/hypokalemia deemed necessary
Hyperchloremia/hypochloremia Monitor body temperature, catheter site, general attitude
Hypernatremia/hyponatremia If sepsis is suspected, parenteral nutrition solution and
Hyperphosphatemia/hypophosphatemia catheter tip should be cultured
Hypermagnesemia/hypomagnesemia Remove catheter as soon as possible once parenteral nutrition
Hyperbilirubinemia is discontinued
Hyperammonemia