Parenteral Nutrition 

Malnutrition

Mal nutrition can be defined as: ‘a deficiency or excess (or imbalance) of energy, protein, and other nutrients that causes measurable adverse effects on the tissue/body size, shape, composition, function and clinical outcome.’

Multiple causes may contribute to malnutrition.

They may include..1. Inadequate or unbalanced food intake, 2. Increased demand due to clinical

disease status, 3. Defects in food digestion or

absorption, or4. A compromise in nutritional metabolic

pathways.

Onset may be acute or insidious.

Examples for malnutrition,

1. impaired immune response, 2. reduced skeletal muscle strength and fatigue, 3. reduced respiratory muscle strength, impaired

thermoregulation, 4. impaired skin barrier and wound healing may

all be a consequence of mild malnutrition.

In turn, these predispose the patient to awide range of problems including

1. infection, 2. delayed clinical recovery, 3. increased clinical complications, 4. inactivity, 5. psychological decline and 6. reduced quality of life.

Nutrition screening

By using the Body mass index tool method, measurement of protein-energy under nutrition has been determined.

Weight (kg) Body mass index =

Height (m)2

BMI category Likelihood of chronicProtein-energy under nutrition

<18.5 kg/m2 Probable

18.5-20 kg/ m2 Possible

>18.5 kg/m2 Unlikely

Indications for parenteral nutrition

Parenteral nutrition (PN) is the IV administration of anutritionally balanced and physiochemically stablesterile combination of the six main groups of nutrients withwater:

1. Amino acids, 2. Glucose, 3. Lipid emulsion including essential fatty acids,4. Vitamins, 5. Trace elements and 6. Electrolytes.

The simplest way to correct or prevent under nutrition is through conventional balanced food. However, this is not always possible.

Nutritional support may then require oral supplements or central feeding. Assuming the gut is functioning normally, the patient will be able to digest and absorb their required nutrients, including

water, protein, carbohydrate, fat, vitamins, minerals and electrolytes. If the gut is not accessible or functioning adequately to meet the patient’s need, or gut rest is indicated, then PN is used.

Close monitoring should ensure the patient’s needs are met; a combination of nutrition routes is sometimes the best course.

Where possible, PN patients should also receive enteral (GI track) intake.

Decision pathway to guide initial and ongoing nutritional support

Repeat screening and evaluation Tube feeding

Normal Short term naso- Initial screening gastric feeding or long term

gasotrostomyMalnourished or at risk Hospital food meets needs

Oral supplements to hospital foodFull nutritional Gut functioning but access impairedAssessment

Gut not accessible PNFunctioning inadequately Peripheralor gut rest required or Central

Nutrition team

Multidisciplinary nutrition teams have been formed in many hospitals, notably the larger tertiary central and teaching hospitals.

Oral diet Parenteral nutrition source

Water/volume Water/volume

Protein Amino acid mixture

Carbohydrate Glucose

Fat with essential fatty acids Lipid emulsions with essential fatty acids

Vitamins Vitamins

Minerals Trace elements

Electrolytes Electrolytes

Components of a parenteral nutrition regimen

Water volume

Water is the principal component of the body and accounts for approximately 60% and 55% of total body weight in men and women, respectively. Usually homeostasis maintains appropriate fluid levels and electrolyte balance and thirst drives the healthy person to drink. Some patients are not able physically to respond by drinking and so this homeostasis can readily be disrupted. In general, an adult patient will require 20-40 ml/kg/day fluid.

Consider increasing the fluid requirements Consider reducing the fluid input

Signs/symptoms of dehydration Signs/symptoms of fluid overload

Fever: increased insensible losses from lungs in hyperventilation and from skin in sweating. Allow 10-15% extra water per 100C above normal.

High humidity: reduced rate of evaporationBlood transfusion: volume input

Acute anabolic state: increased water required for increased cell generation

Drug therapy: assess volume and electrolyte content of infused drug

High environmental temperature or low humidity: increased rate of evaporation

Cardiac failure: may limit tolerated blood volume

Abnormal GI loss (vomiting, diarrhoea): consider both volume loss and electrolyte content

Renal failure: fluid may accumulate so reduce input accordingly, or provide artificial renal support

Burns or open wound: increased water evaporation

Blood loss: assess volume lost and whether replaced by transfusion, colloid, crystalloid

Factors affecting fluid requirements

Amino acids

20 amino acids are required for protein synthesis and metabolism. A majority of these can be synthesized endogenously. 8 of them cannot be synthesized and called essential amino acids. (Isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine)

A further group of ‘conditionally essential’ amino acids, arginin, choline, glutamine, taurine and methionine are defined as the patient’s needs exceed the synthesis in clinically stressed conditions. Also, due to the immature metabolic pathways of neonates, infants and children, some other amino acids are essential in the young patient, and these include histidine, proline, cysteine, tyrosine and taurine.

To balance the patient’s amino acid requirements and the chemical characteristics of the amino acids (solubility, stability and compatibility), a range of commercially available licensed solutions have been formulated.For adult –Aminoplex, Intrafusin, Synthamin and Vamin are designed.

L-glutamine was initially excluded from formulations due to its low solubility and relatively poor stability in the aqueous environment. It is recognized that there is a clinical need for this amino acid in catabolic stress, and it is now available as a free L-glutamine additive and as a depaptide (with alanine and lysine)

For adults, PN solutions are generally prescribed in terms of the amount of nitrogen they provide, rounding to the nearest gram, for example 9g, 11g, 14g or 18g nitrogen regimes may be prescribed. Assuming adequate energy is supplied.

Most adult patients achieve nitrogen balance with 0.2g nitrogen/kg/day.

In paediatrics, the term amino acid is preferred when formulating PN solutions. The term ‘protein content’ is no longer favoured as the solutions contain amino acids, not protein. The conversion factor for g of protein to g of nitrogen varies. Usually 1 g nitrogen per 6.25 g of protein is calculated. 

Amino acid and consequential nitrogen content of licensed amino acid solutions available commercially (in UK).

Amino acid g/l Nitrogen g/lPaediatric Primine 10% 100 15

Vaminolact 65.3 9.3Adult Glamin 134g 22.4

Hyperamine 30 179 30Intrafusin 11 73.28 11.4Intrafusin 22 152.3 22.8Synthamin 9/9 55 9.1Synthamin 14/14 85 14Synthamin 14/14 100 16.5Vamin 9/9 glucose 70.2 9.4Vamin 14/14 85 13.5Vamin 18 114 18.0

GlucoseGlucose is the recommended source of carbohydrate (1g anhydrous glucose provides 4 kcl).Glucose infusion rate should generally be between 2 and 4mg/kg/min.An infusion of 2mg/kg/min (equating to approximately 200g (800kcal) per day for a 70kg adult.) represents the basal glucose requirement.

Energy provision and tonicity of glucose solution

Concentration w/v Energy content (kcal/L)

Approx. osmolarity (mOsmol/L)

5% 200 278

10% 400 555

20% 800 1110

50% 2000 2775

70% 2800 3885

Lipid emulsions

Lipid emulsions are used as a source of energy and for the provision of the essential fatty acids, linoleic and α-linolenic acid. Supplying 10kcal energy per gm of oil, they are energy rich and can be infused directly in to the peripheral veins since they are relatively isotonic with blood.Typically, patients receive up to 2.5g lipid/kg/day. For practical compounding reasons, and assuming clinical acceptance, this tends to be rounded to 100g or 50g.

Lipid emulsions available in the market are as follows—

Licensed lipid emulsions

Lipid emulsion type Details of products with kcal per Litre

Soybean oil (egg phospholipids)

►Intralipid 10% (1100 kcal), 20% (2000 kcal), 30% (3000 kcal)

►Ivelip 10% (1100 kcal), 20% (2000 kcal)

►Lipofundin N 10% (1022 kcal), 20% (1900 kcal)

The first generation lipid emulsions have been in use since 1970s and utilize soybean oil as the source of long chain fatty acids. They are safe and their efficient.

Recent groups are developed from the source of Olive oil, fish oil.20% lipid emulsions are favoured, especially in paediatrics, as they contain less phospholipid.

Lipid clearance monitoring is particularly important in patients who are at risk of impaired clearance, including those who are hyperlipidaemic, diabetic, septic, have impaired renal or hepatic function, or are critically ill.

Micronutrients & Trace elements

Micronutrients have a key role in intermediary metabolism, as both co-factors and co-enzymes. For example: zinc is required by over 200 enzyme systems and affects many diverse body functions including acid-base balance, immune function and nuclic acid synthesis. It is evident, therefore, that the availability of micronutrients can affect enzyme activity and total metabolism.

Micronutrients & Trace elements

Trace elements are generally maintained at a relatively constant tissue concentration and are present to a level of less than 1mg/kg body weight. They are essential; difficiency results in structural and physiological disorders, but if identified early enough, can be resolved by re-administration.Ten essential trace elements are known: iron, copper, zinc, fluorine, manganese, iodine, cobalt (or as hydroxycobalamine), selenium, molybdenum and chromium.

VitaminsTwo groups of vitamins, water soluble and fat soluble. Fat-soluble vitamins are stored in the body, whereas excess water-soluble vitamins are renally cleared. Therefore, if there is inadequate provision, deficiency states for the water-soluble vitamins reveal themselves first.

FDA recommended daily requirements of vitamins (Parenteral dose)

Vitamin Recommended P/D

Vitamin Recommended P/D

A (retinal) 1.0mg B1 (thiamin) 6.0mgB2 (riboflavin)

3.6mg B6 (pyridoxine)

4.0mg

B12 5.0 mcgm C 200mgD 5.0 mcgm E(α-

tocoferol)10.0mg

K1 150.0mcgm Folic acid 600mcgmPantothenic acid

15.0mg Biotin 60.0mcgm

Niacin 40.0mg

ElectrolytesSodium, potassium, calcium, magnesium, and phosphate are included to meet patient needs. Depending upon the stability of the patient’s clinical state, they are kept relatively constant or adjusted on a near daily basis, reflecting changes in blood biochemistry. Recommended dose below can be used to guide electrolyte replacement if there are excessive GI waste or high losses through burns

Sodium chloride 10%

1.7 Sodium chloride 23.5%

4

Sodium chloride 30%

5.1 Sodium acetate 40mmol/10ml

4

Sodium glycerophosphate 21.6%

2 Potassium chloride 15%

2

Potassium acid phosphate 13.6%

1 Calcium chloride 1 mmol/ml

1

Calcium chloride 0.5 mmol/ml

0.5 Calcium chloride 13.4%

0.91

Calcium gluconate 10%

0.22 Magnesium sulphate 10%

0.4

Magnesium sulphate 50%

2 Addiphos 1.5

Iron chloride 100 mcgm

1.79 Iron chloride 300 mcgm

5.36

Sodium selenite 16mcgm

0.2

Contents /mL measured as (mmol)

Fluids 20 ml Per Kg Per day

Amino acids 0.2 gm Per Kg Per day

Glucose 2000 mgm Per kg Per day

Lipid 2.5 gm Per kg Per day

Trace element 1 mgm Per kg Per day

List of requirement

Routes of AdministrationPN can be administered peripherally or centrally

Peripheral routePeripheral administration should be considered first line for parenteral feeding. Supported by good techniques, line care and low tonicity feeds, patients can be successfully maintained with this route for many weeks. Peripheral lines are less costly than central lines. They can be inserted by less specialized staff, there is no requirement for a chest X-ray to confirm placement, and line care protocols are simpler. A mid line should be considered as a peripheral line as it does not reach the central circulation.Peripheral administration is sometimes complicated or delayed by phlebitis (inflammation of the vein).

PICCs Peripherally inserted central catheters are typically inserted into a peripheral vein, usually the cephalic or basilic in the upper arm, with the exit tip in the superior vena cava just above the right atrium.

They are used for the central administration of infusions. Single and double lumen versions are available. Some also have a one way valve to prevent backflow. Insertion is less invasive than for conventional central lines and can be under taken by nurse practitioners.

Pharmaceutical issues

Having identified the balance of nutrients required for a patient in a single day, it is necessary to formulate a physically and chemically stable sterile admixture. PN admixtures contain over 50 chemical entities and as such, are extremely complex.

All PN manufacturers should maintain the professional guideline and reference material before compounding and administering PN.Before use there must be the reports on stability over the product justified.

Physical stability (Precipitation, lipid destabilization, temperature,) must be confirmedChemical stability (vitamin stability, amino acid stability)

Microbial stability Shelf-life and temperature controlDrug stabilityLight protection

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