Total Parentral Nutrition (TPN)

Total Parentral Nutrition (TPN)

TPN stands for Total Parenteral Nutrition. This means that food, (really a liquid full of nutrients) is provided through a vein. No extra food needs to be taken orally.

 

Parenteral (intravenous) feeding is an expensive and complex way of providing nutrition, and should be reserved for those situations in which enteral feeds are not practicable. It should only be undertaken by experienced medical and nursing staff and where adequate biochemical, bacteriological and pharmaceutical services are available. In preterm infants with low body nutrient stores, cautious use of intravenous nutrition can prevent catabolism, with its resultant negative nitrogen balance, until enteral feeds are established. Infants with serious gut disorder may require total parenteral nutrition for several weeks .

 

General Usage

TPN is normally used following surgery, when feeding by mouth or using the gut is not possible, when a person's digestive system cannot absorb nutrients due to chronic disease, or, alternatively, if a person's nutrient requirement cannot be met by enteral feeding (tube feeding) and supplementation. It has been used for comatose patients, although enteral feeding is usually preferable, and less prone to complications. Short-term TPN 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 TPN is occasionally used to treat people suffering the extended consequences of an accident or surgery. Most controversially, TPN has extended the life of a small number of children born with nonexistent or severely birth-deformed guts. The oldest were eight years old in 2003.

severely birth-deformed guts. The oldest were eight years old in 2003.

The preferred method of delivering TPN is with a medical infusion pump. A sterile bag of nutrient solution, between 500 mL and 4 L is provided. The pump infuses a small amount (0.1 to 10 mL/hr) continuously in order to keep the vein open. Feeding schedules vary, but one common regimen ramps up the nutrition over a few hours, levels off the rate for a few hours, and then ramps it down over a few more hours, in order to simulate a normal set of meal times.

The nutrient solution consists of water, glucose, salts, amino acids, vitamins and (more controversially) sometimes emulsified fats. Long term TPN patients sometimes suffer from lack of trace nutrients or electrolyte imbalances. Because increased blood sugar commonly occurs with TPN, insulin may also be added to the infusion. Occasionally, other drugs are added as well.

Chronic TPN is performed through a Hickman line or a Port-a-Cath (venous access systems). In infants, sometimes the umbilical artery is used.

Battery-powered ambulatory infusion pumps can be used with chronic TPN patients. Usually the pump and a small (100 ml) bag of nutrient (to keep the vein open) are carried in a small bag around the waist or on the shoulder. Outpatient TPN practices are still being refined.

Nutritional content

TPN requires water (30 to 40 mL/kg/day), energy (30 to 60 kcal/kg/day, depending on energy expenditure), amino acids (1 to 2.0 g/kg/day, depending on the degree of catabolism), essential fatty acids, vitamins,

Basic TPN solutions are prepared using sterile techniques, usually in liter batches according to standard formulas. Normally, 2 L/day of the standard solution is needed. Solutions may be modified based on laboratory results, underlying disorders, hypermetabolism, or other factors. Commercially available lipid emulsions are often added to supply essential fatty acids and triglycerides; 20 to 30% of total calories is usually supplied as lipids. However, withholding lipids and their calories may help obese patients mobilize endogenous fat stores, increasing their insulin

Solutions: Many solutions are commonly used. Electrolytes can be added to meet the patient's needs.

Patients who have renal insufficiency and are not receiving dialysis or who have liver failure require solutions with reduced protein content and a high percentage of essential amino acids. For patients with heart or kidney failure, volume (liquid) intake must be limited. For patients with respiratory failure, a lipid emulsion must provide most of nonprotein calories to minimize CO2 production by carbohydrate metabolism. Neonates require lower dextrose concentrations (17 to 18%).

Beginning TPN administration

Because the central venous catheter needs to remain in place for a long time, strict sterile techniques must be used during insertion and maintenance. The TPN line should not be used for any other purpose. External tubing should be changed q 24 h with the first bag of the day. In-line filters are controversial and may not help. Dressings should be kept sterile and are usually changed q 48 h using strict sterile techniques. For TPN given outside the hospital, patients must be taught to recognize symptoms of infection, and qualified home nursing must be arranged.

The solution is started slowly at 50% of the calculated requirements, using 5% dextrose to make up the balance of fluid. Energy and nitrogen should be given simultaneously. The amount of regular insulinSome Trade Names

HUMULIN

NOVOLIN

given (added directly to the TPN solution) depends on the blood glucose level; if the level is normal and the final solution contains the usual 25% dextrose concentration, the usual starting dose is 5 to 10 units of regular insulinSome Trade Names

HUMULIN

NOVOLIN

/L of TPN fluid

Monitoring

Progress should be followed on a flowchart. An interdisciplinary nutrition team, if available, should monitor the patient. Weight, CBC, electrolytes, and BUN should be monitored often (eg, daily for inpatients). Blood glucose should be monitored q 6 h until stable. Fluid intake and output should be monitored continuously. When the patient becomes stable, blood tests can be done much less often.

Liver function tests should be done. Plasma proteins (eg, serum albumin, possibly transthyretin or retinol-binding protein); prothrombin time; plasma and urine osmolality; and Ca, Mg, and phosphate (not during glucose infusion) should be measured twice/wk. Full nutritional assessment (including BMI calculation and anthropometric measurements.

Complications

With close monitoring by a nutrition team, the complication rate may be < 5%. Complications may be related to the central venous catheter.

Glucose abnormalities are common. Hyperglycemia can be avoided by monitoring blood glucose often, adjusting the insulinSome Trade Names

HUMULIN

NOVOLIN

dose in the TPN solution, and giving subcutaneous insulinSome Trade Names

HUMULIN

NOVOLIN

as needed. Hypoglycemia can be precipitated by suddenly discontinuing constant concentrated dextrose infusions. Treatment, depending on the degree of hypoglycemia, may consist of 50% dextrose IV or infusion of 5 or 10% dextrose for 24 h before resuming TPN via the central venous catheter.

Abnormalities of serum electrolytes and minerals should be corrected by modifying subsequent infusions or, if correction is urgently required, by beginning appropriate peripheral vein infusions. Vitamin and mineral deficiencies are rare if solutions are given correctly. Elevated BUN may reflect dehydration, which can be corrected by giving free water as 5% dextrose via a peripheral vein.

Volume overload (suggested by > 1 kg/day weight gain) may occur when high daily energy requirements require large fluid volumes.

Metabolic bone disease, or bone demineralization (osteoporosis or osteomalacia), develops in some patients receiving TPN for > 3 mo. The mechanism is unknown. Advanced disease can cause severe periarticular, lower extremity, and back pain. Temporarily or permanently discontinuing TPN is the only known treatment.

Adverse reactions to lipid emulsions (eg, dyspnea, cutaneous allergic reactions, nausea, headache, back pain, sweating, dizziness) are uncommon but may occur early, particularly if lipids are given at > 1.0 kcal/ kg/h. Temporary hyperlipidemia may occur, particularly in patients with kidney or liver failure; treatment is usually not required. Delayed adverse reactions to lipid emulsions include hepatomegaly, mild elevation of liver enzymes, splenomegaly, thrombocytopenia, leukopenia, and, especially in premature infants with respiratory distress syndrome, pulmonary function abnormalities. Temporarily or permanently slowing or stopping lipid emulsion infusion may prevent or minimize these adverse reactions.

Hepatic complications include liver dysfunction, painful hepatomegaly, and hyperammonemia. They can develop at any age but are most common among infants, particularly premature ones (whose livers are immature). Transient liver dysfunction, evidenced by increased transaminases, bilirubin, and alkaline phosphatase, is common with the initiation of TPN. Delayed or persistent elevations

 

may result from excess quantities of amino acids. Pathogenesis is unknown. Contributing factors probably include cholestasis and inflammation. Progressive fibrosis occasionally develops. Reducing protein delivery may help. Painful hepatomegaly suggests fat accumulation; carbohydrate delivery should be reduced. Hyperammonemia can develop in infants. Signs include lethargy, twitching, and generalized seizures. Correction consists of arginine supplementation at 0.5 to 1.0 mmol/kg/day. For infants who develop any hepatic complication, limiting amino acids to 1.0 g/kg/day may be necessary.

 

Gallbladder complications include cholelithiasis, gallbladder sludge, and cholecystitis. These complications can be caused or worsened by prolonged gallbladder stasis. Stimulating contraction by providing about 20 to 30% of calories as fat and stopping glucose infusion several hours a day is helpful. Oral or enteral intake also helps. Treatment with metronidazoleSome Trade Names

FLAGYL

, ursodeoxycholic acid, phenobarbitalSome Trade Names

LUMINAL

, or cholecystokinin helps some patients with cholestasis

 

Basic Adult Daily Requirements for Total Parenteral Nutrition
Amount		Nutrient
mL	30–40	Water (/kg body wt/day)
		Energy*
kcal	30	Medical patient
kcal	30–45	Postoperative patient
kcal	45–60	Hypercatabolic patient
		Amino acids (/kg body wt/day)
g	1.0	Medical patient
g	2.0	Postoperative patient
g	3.0	Hypercatabolic patient

 

 

 

 

 

 

		Minerals
mEq	90	Acetate/gluconate
mEq	15	Calcium
mEq	130	Chloride
μg	15	Chromium
mg	1.5	Copper
μg	120	Iodine
mEq	20	Magnesium
mg	2	Manganese
mg	300	Phosphorus
mEq	100	Potassium
μg	100	SeleniumSome
mEq	100	Sodium
mg	5	Zinc

 

 

 

 

 

 

 

		Vitamins
mg	100	Ascorbic acid
μg	60	Biotin
μg	5	Cobalamin
μg	400	Folic acid
mg	40	NiacinSome Trade Names
mg	15	Pantothenic acid
mg	4	Pyridoxine
mg	3.6	Riboflavin
mg	3	Thiamin
IU	4000	Vitamin A
IU	400	Vitamin D
mg	15	Vitamin E
μg	200	Vitamin K
*Requirements for energy increase by 12% per 1 C

 

 

 

 

 

 

Energy requirements

Over feeding and underfeeding are associated with undesirable effects afirst step in nutrition support care is to determine energy needs as accurately as possible.

The energy requirements of an individual are primarily related to body size and composition, age ,gender,and activity.critical  illness often leads to amarked increase in energy and protein requirements. Amyriad of predictive energy equations and indirect calorimetry are tools used to determine energy needs and metabolic status .

•         The most widely used predictive energy equation is the HARRIS-BENEDICT equation which is reflect the resting energy expenditure:EEE

•         Men resting energy expenditure=66+13.7(W)+5(H)-6.8(A)

•         Women resting energy expenditure=655+9.6(W)+1.9(H)-4.7(A)

•         W=weight in kilogram

•         H=height in centimeters

•         A=age in years

•         The IRETON-JONES equation :

•         EEE(v)=1925-10(A)+5(W)+281(S)+292(T)+851(B)

•         EEE(s)=629-11(A)=25(W)-609(O)

•         V=ventilator dependent

•         s=spontaneous breathing

•         A=age

•         W=weight in kilogram

•         S=sex(male 1,female0)

•         T=trauma

•         B=burns

•         O=obesty

•         (present 1, absent 0)

Indirect calorimetry

Indirect calorimetry is the calculation of heat production through the measurement of pulmonary gas exchange,specificaly the measurement of oxygen consumption(Vo2)and carbon dioxide production (Vco2). The measurements of Vo2 and Vco2 are converts to energy expenditure (Kcal/day)by application of the weir eqoution.

•         Energy expenditure= [(Vo2)(3.941) + (Vco2)(1.11)]1440

•         Where Vo2 and Vco2 are expressed in L/min and 1440= number of minuts in aday.

•         Currently ,indirect calotimetry is used to determine caloric requirements of patients requiring numtritional support, to modify nutritional regimens and to predict successful weaning from mechanical ventilation.

•         Indirect calorimeters are classified based on the method of Vo2 measurement.Open-circuit indirect calorimeters determine Vo2 by measuring minute ventilation (VE) and the difference between inspired and expired gas concentrations. Close-circuit calorimeters determine Vo2 by measuring the Volumetric change from a reservoir of oxygen over time.

•                 A-Open – Circuit calorimetry

•                 Theory and calculations

•                 Mixing-chamber technique

•                 Breath-by-breath technique

•                 Dilution technique

•                 B- Closed-circuit calorimetry

•                 Volume-loss technique

•                 Volume-replenishment technique

 

Parenteral Nutrition In Renal Diseases

 

       Total parenteral nutrition is associated with increased infectious complications and is significantly more expensive than enteral feedings. Parenteral nutrition also requires a greater fluid volume to meet calorie and protein needs than the equivalent enteral nutrition. Parenteral nutrition should be reserved only for those patients who are unable to receive enteral nutrients.

       One method of delivering parenteral nutrition to hemodialysis patients is to provide intradialytic parenteral nutrition   (IDPN).  IDPN   allows   parenteral nutrition without concern for volume overload, additional time commitment of the patient, or additional vascular access.  The  two  primary  disadvantages  of IDPN  is  the  cost  (~$200–500  per  “dose”),  and  the small amount of nutrition that is actually provided per “dose.” IDPN cannot meet a patient’s basic calorie or protein needs, in part because it is provided only

       three times per week during dialysis. Typically IDPN pro- vides an average of only 400–500 calories and 30–40 gm protein per day. Finally, there is no prospective, randomized controlled evidence supporting improved clinical outcomes with IDPN.

 

Studies

Total parenteral nutrition in the management of acute renal failure

 MJ Blumenkrantz, JD Kopple, A Koffler, AK Kamdar, MD Healy, EI Feinstein and SG Massry

       Malnutrition is frequently present in patients with acute renal failure and may affect morbidity and mortality in this condition.    When adequate nourishment cannot be given through the gastrointestinal tract, total parental nutrition with amino acids and hypertonic glucose may have beneficial results. Total parenteral nutrition has been reported to stabilize or reduce serum urea nitrogen, potassium and phosphorus levels, improve wound healing, enhance survival from acute renal failure, and possibly increase the rate of recovery of renal function. The optimal composition of the total parenteral nutrition infusate is unknown..

 

. Preliminary results of a double-blind study are reported in which one man received hypertonic glucose alone, two received glucose with essential amino acids (21 g/day), and three received glucose with essential (21 g/day) and nonessential (21 g/day) amino acids. All infusates were isocaloric. No differences were observed in serum urea nitrogen levels, serum urea nitrogen/creatinine ratios or urea appearance rates. Nitrogen balance was negative in all patients. The ratio of essential amino acids/nonessential amino acids was higher and the tyrosine/phenylalanine ratios were lower in plasma in the two patients receiving glucose with essential amino acids. No patient survived the hospitalization. In view of the markedly negative nitrogen balance frequently observed in these and earlier studies, the use of a different composition or quantity of amino acids, a higher energy intake, and anabolic hormones deserve further investigation.