Total Parenteral Nutrition (TPN)

Total Parenteral Nutrition (TPN)

Parenteral nutrition refers to the delivery of calories and nutrients into a vein. It is a form of specialized nutrition, including amino acids, dextrose, fat emulsion, vitamins, minerals and trace elements given intravenously.

Partial parenteral nutrition supplies only part of daily nutritional requirements, supplementing oral intake. Many hospitalized patients are given dextrose or amino acid solutions by this method.

Total parenteral nutrition supplies all daily nutritional requirements. Because TPN solutions are concentrated and can cause thrombosis of peripheral veins, a central venous catheter is usually required.

Indications

TPN may be the only feasible option for patients who do not have a functioning GI tract or who have disorders requiring complete bowel rest, such as the following:

• Some stages of ulcerative colitis.
• Bowel obstruction.
• Certain pediatric GI disorders (e.g. congenital GI anomalies, prolonged diarrhea regardless of its cause).
• Short bowel syndrome due to surgery.
• Inflammatory bowel disease.
• Gastrointestinal fistula.
• Severe diarrhea, e.g. ulcerative colitis.
• Persistent vomiting.
• Malabsorption.
• Hypermetabolic states for which enteral therapy is either not possible or inadequate.
• Severe burns.
• Trauma/surgery when nothing can be taken by mouth for more than 5 days.
• Acute renal failure.
• Tumor in GI Tract.
• Patient at risk for malnutrition because of:
  • Gross underweight (more than 80% below the standard).
  • Metastatic cancer.
• NPO for more than 5 days.

Methods of Parenteral Nutrition

• Total Nutrient Admixture into a central vein (TNA).
  • This parenteral formula combines carbohydrates in the form of a concentrated (20-70%) dextrose solution, proteins in the form of amino acids; lipids in the form of an emulsion (10-20%), including triglycerides, phospholipids, glycerol and water; vitamins and minerals.
  • It is indicated for the patients requiring parenteral feeding for seven or more days. It is given through a central vein often into the superior vena cava.
• Peripheral Parenteral Nutrition (PPN)
  • This parenteral formula combines carbohydrates as a lesser concentrated glucose solution with amino acids, vitamins, minerals and lipids.
  • It is given through a peripheral vein and it is indicated for the patients requiring parenteral nutrition for fewer than 7 days.
• Total Parenteral Nutrition (TPN)
  • This parenteral formula combines glucose, amino acids, vitamins and minerals.
  • It is given through a central IV line. If lipids are needed, they are given intermittently mixed with the TPN.
• Fat emulsion (lipids)
  • It is composed of triglycerides (10-20%) e.g. phospholipids, glycerol and water. May be given centrally or peripherally.

Articles

• Central venous access devices: Long-term VADS such as Hickman, Broviac or Groshung catheters or peripherally inserted central catheter (PICC line) or peripheral IV access.
• Volume control infuser.
• Filters: 0.22 micron for TPN (without fat emulsion).
• 3.2 Micron filter for TNA or fat emulsion.
• Bag of parenteral nutrition.
• Administration tubing with Luer-Lock connections.
• Hypoallergic tape.
• Face mask (optional).
• Sterile gloves.

Procedure

• Assess the need for parenteral nutrition by performing nutritional assessment.
• Check the physician's order for method of parenteral nutrition (TNA, TPN, PPN or lipids) and flow rate.
• Explain the procedure in detail to the patient and relatives.
• Obtain informed consent.
• Collect needed equipment for the procedure.
• Remove the bag of parenteral nutrition from refrigerator at least 1 hour before procedure (if refrigerated).
• Inspect fluid for presence of creaming or any change in constitution.
• Wash hands, don cap, mask, gown and sterile gloves.
• Using strict aseptic technique, attach tubing (with filter) to TNA bag and purge out air.
• Close all clamps on new tubing and insert tubing into volume control infuser.
• Place the patient in the supine position and turn the head away from VAD insertion site.
• Clean the insertion site with alcohol and povidone-odine solution.
• Assist the physician while inserting VAD.
• After insertion of VAD, connect tubing to hub of VAD using sterile technique and make sure that the connection is secured using Luer-Lock connection.
• Open all clamps and regulate flow through volume control infuser.
• Monitor administration hourly, assessing for integrity of fluid and administration system and patient tolerance.
• Record the procedure.

Complications

• Sepsis
• Electrolyte imbalance
• Hyperglycemia/Hypoglycemia
• Hypervolemia
• Hyperosmolar diuresis

Considerations

• Strict surgical asepsis is mandatory throughout the insertion of the catheter, when handling the solution and tubes and when caring for the site of insertion. The parenteral line can serve as an excellent cultural medium since it directly leads to blood and bacterial invasion leads to septicemia.
• Psychological support is necessary, as the patient is not taking anything orally, for a long time.
• As nothing enters the GI tract, bowel elimination will decrease and it should be explained to the patient.
• Because TPN solutions are high in glucose, infusions are started slowly to prevent hyperglycemia.
• Rate of infusion for an adult is 1 liter (40 mL/hr) the first day, 2 liters (80 mL/hr) for 24 to 48 hours and 3 liters (120 mL/hr) within 3 to 5 days.
• To prevent hypoglycemia, while discontinuing parenteral nutrition, the solution should be reduced gradually over 48 hours.
• TPN is given for fewer than 7 days.

Gastric Aspiration

Definition

It is removal of stomach content through a nasogastric tube by aspiration using low suction. Or it is the method of removal of fluid, gas and other contents from stomach and intestine through a gastrointestinal tube for therapeutic and diagnostic purposes.

Purposes

• To relieve abdominal distention.
• To maintain gastric decompression after surgery.
• To remove blood and secretions from the gastrointestinal tract.
• To remove the contents of the stomach.
• To prepare the patient for general anesthesia and gastrointestinal surgery.
• To aid in healing of the wound in case of surgery of the stomach and intestines.

Articles

• Tray,
• Gastrointestinal tube (Ryle's tube),
• Kidney tray or drainage collection bottle or bags for drainage from stomach,
• Mackintosh,
• Stethoscope,
• 20 cc syringe,
• Gauze pieces,
• Disposable gloves,
• Towel,
• Pint measure,
• Lubricant,
• Leucoplast and scissors,
• Bowl with water.

Procedure

• Check the doctor's order.
• Explain the procedure to the patient.
• Maintain privacy by screen.
• Position the patient in semi fowler's position.
• Lower side rails on your side, spread mackintosh near head end.
• Wash hands and put on gloves.
• Remove the cap from distal and of Ryle's tube and attach 20 cc syringes to the end by holding it with a gauze piece.
• Aspirate the stomach contents gently.
• As the syringe is filled with contents pinch Ryle's tube, disconnect the syringe from tube and empty contents into kidney tray.
• Continue aspirating till all stomach content is aspirated.
• Disconnect the syringe and clamp the Ryle's tube. Rinse the syringe in a basin of water.
• Measure the amount of contents aspirated using a pint measure.
• Discard the aspirated contents and wash pint measure. Discard the non-absorbent pad.
• Remove gloves and wash hands.
• Assist the patient for a mouth wash.
• Record the colour, odour and quantity of contents aspirated. If necessary send sample to lab.

Maintaining Fluid and Electrolyte Balance

Fluid

 It is a substance which can flow. Body fluid includes blood, cerebrospinal fluids, pleural fluid, peritoneal fluid, etc. In a normal adult, the body fluid is 60% of the total body weight, while in  a child it is more that is about 70% and in infants it is about 80% of the total body weight. These fluids contain a large amount of water.

Distribution of Fluid in the Body

Intracellular Fluids

The intracellular compartment refers to the spaces inside the cell. Intra = inside; cellular = of the cell. It comprises all fluids within body cells. In adults, approximately 40% of body weight is ICF (Intracellular fluid). Potassium is the principal electrolyte of ICF.

Intracellular fluids are:

• Synovial Fluid,
• Peritoneal Fluid,
• Pericardial Fluid,
• Cerebrospinal Fluid.

Extra Cellular Fluid

Extra: outside; cellular:  of the cells. So it means all the fluids outside cells. In adults about 20% of the body fluid is extracellular. In children, 26.7% of the total weight is extracellular fluid which is divided into following smaller compartments:

Interstitial Fluid: Inter: in between; stitial: tissue. It is the fluid between the cells and outside the blood vessels. It contains lymph. In an adult, about 15% of the total body weight is interstitial fluid; in children it is 20%. A bat

Intravascular Fluid: Intra inside; Vascular: blood vessels. So fluid which is containing = inside the blood vessels is known as intravascular fluid. Such as blood plasma.

Sodium is the principal electrolyte of ECF.

Electrolytes

Electrolytes are minerals found in our body that have an electric charge. Body fluid contains salts/minerals such as sodium (Na), Potassium (K), etc. known as electrolytes. Electrolytes play an important role in maintaining the normal intracellular and extracellular fluid balance.

An electrolyte is an element that when dissolved in water or another solvent, separates into ions and is able to carry as electrical current.

Ions are of two types:

Cations: Positively charged electrolytes called cations e.g. sodium (Na+), potassium (K+), Calcium (Ca), etc.

Anions: Negatively charged electrolytes called anions e.g. Chloride (CI), bicarbonate (HC02), etc.

Main electrolytes of body fluids are:

• Extracellular Fluids
  • Sodium
  • Calcium chloride bi-carbonate
• Intracellular Fluids
  • Potassium
  • Magnesium
  • Calcium

Movement of the Body Fluids + Body Electrolytes

Fluid and electrolyte constantly shift from one compartment to another through semipermeable membrane to facilitate body process such as tissue oxygenation, acid base balance and urine formation.

• Diffusion,
• Osmosis,
• Osmotic pressure,
• Osmolarity,
• Active transport,
• Hydrostatic pressure.

Regulation of Body Fluids

Body fluids are regulated by fluid intake hormonal control and fluid output. This physiological balance is termed homeostasis. In health, the body is able to respond to disturbances in fluids and electrolytes to prevent and repair damage.

Fluid Intake

Fluid intake is regulated primarily through the thirst mechanism. The thirst control center is located in the hypothalamus in the brain. The osmoregulator in the hypothalamus continuously monitors serum osmotic pressure. When osmolarity increases, the hypothalamus stimulates thirst. Eating salty food, decreased oral fluid intake, excess fluid loss, administration of hypertonic solutions, etc. increases the osmotic pressure. Eating potato chip is an example; the salt on the chips increases the osmotic pressure of the body fluids and stimulates the thirst mechanism. The hypothalamus will also be stimulated when excess fluid is lost and hypovolemia occurs, as in excessive vomiting and haemorrhage. Thirst is the conscious desire for water and is one of the major factors that determines fluid intake. The average adult's intake is about 2200-2700 ml/day.

Hormonal Regulation

Hormones regulate fluid intake through various mechanisms.

Antidiuretic Hormone (ADH): It is stored in the posterior pituitary gland and is released in response to changes in blood osmolarity. The osmoreceptors in the hypothalamus are stimulated when there is an increase in osmolarity to release the hormone ADH. The ADH works directly on the renal tubules and collecting ducts to make them more permeable to water. This is turn causes water to return to the systemic circulation, diluting the blood and decreasing its osmolarity.

Aldosterone: The adrenal cortex releases aldosterone in response to increased plasma potassium level. It acts on the distal portion of the renal tubule to increase the reabsorption of sodium and excretion of potassium. Sodium retention leads to water retention. So, release of aldesterone acts as volume regulator.

Rennin: It responds to decreased renal perfusion secondary to decrease in extracellular volume. Rennin acts to produce angiotensin I which causes some vasoconstriction. Angiotensin I convert to angiotensin II by angiotensin converting enzyme. Angiotensin II causes massive selective vasoconstriction of many blood vessels and relocates and increases the blood flow to the kidney improving renal perfusion. It also stimulates the release of aldosterone from the adrenal cortex. 

Fluid Output Regulation

Fluid output occurs through four organs, they are:

Kidney: The kidneys are the major regularity organs of fluid balance. They receive approximately 1800 ml of plasma to filter each day and produce 1500 ml of urine.

Skin: Water loss from the skin is regulated by the sympathetic nervous system, which activates sweat glands. An average 400-500 ml of fluid is lost via the skin each day.

Lungs: The lungs expires about 350-400 ml of water daily.

Gastrointestinal Tract: The GI tract plays a vital role in fluid regulation, approximately 3-6 liter of isotonic fluid is moved into the GI tract and then returns again to the extra cellular fluid. In normal conditions, the average adult loses only 100-200 ml of the 3-6 liter each day through faeces.

Fluid Balance

In a healthy person, fluid intake is usually adjusted according to the fluid output and vice versa. In this way, the fluid and electrolyte content of the body remains fairly constant. This is called the fluid balance. The intake and output of fluids is balanced both in terms of amount and composition. As fluid is lost from the body through various means, an adequate amount of fluid should be taken to balance the fluid output. Thirst is the means of recognizing that our body needs more fluid.

Total body water is also variable by:

Age: Increase in age and fat, increases displacement of water so decrease in water in body is in relation to body weight. 

Sex: In male, needs higher than female due to high metabolic rate in male and there is high rate of adipose tissue in female.

Obesity: In non-obese person greater amount of water is needed than obese person due to presence of high amount of fatty tissue in obese person.

Fluid Imbalance

Fluid imbalance occurs when either the intake exceeds or output is more than intake. When there is excessive fluid in the body, the state is called over hydration and when there is less fluid in the body it is called dehydration. Both these conditions are dangerous for patients. In such conditions an accurate assessment of fluid and electrolyte need must be made by:

• Assessing the degree of dehydration of the patient.
• Keeping an accurate intake and output chart.
• Weighing the patient.

Regulation of Acid Base Balance

If concentration of hydrogen ions in body fluids is stable then it is called acid base balance. The pH is the scale of measuring the acidity and alkalinity of a fluid. Optimal pH varies from one body fluid to another. The normal pH of arterial blood is 7.4, that of venous blood is 7.35 and ICF is averages 7.0. The lower pH in cells and venous blood reflects their greater amounts of acidic metabolites and carbon dioxide, which combines with water to form carbonic acid, H2CO3 Whenever the pH of arterial blood rises above 7.45, the person is said to have alkalosis or alkalemia. Arterial blood below 7.35 results in acidosis or academia. PH level 7 is known as neutral. Any arterial pH between 7.35 and 7.0 is called physiological acidosis.

The H+ concentration in blood is regulated by:

• Buffer system.
• Respiratory system.
• Renal mechanism.

Buffer Systems

• Buffer is a substance that can absorb or release hydrogen ions to correct an acid base imbalance.
• A buffer substance is a group of chemical substances which make it possible for the blood to take up large amounts of acids or bases without a change in the pH of the body fluid.
• But the buffer system can only function effectively if there is normal functioning of the kidneys and lungs.
• If excess hydrogen ion is present in the body fluids, buffer bind with the hydrogen ion minimizing the changes in pH. When body fluids become too alkaline, buffers release hydrogen ion, minimizing the changes in pH. 

Respiratory System and pH Control

• Lungs help to control and maintain the pH or acid base level in blood. 
• An increased amount of CO2 in the blood stimulates the respiratory centre in the medulla oblongata.
• Rate and depth of respiration is increased, permitting excess amount of carbon dioxide to be expired. As the result the blood CO2 level goes down.
• After that decreased blood level of CO2, causes less stimulation of the respiratory centre that makes decrease rate and depth of respiration which permits accumulation of CO2 in the blood.
• In this way normal acid base balance is maintained.

Urinary System and pH Control

• The kidneys too help in maintaining the pH level.
• When body fluid tends to be more acidic, the kidneys can eliminate more H+ ions from the body and can reabsorbed more bases mainly Na.
• When the body fluids tend to be more alkaline it eliminate fewer H+ ions.

Major Electrolyte Imbalances 

Hyponatremia: Serum sodium level is below 135 meq/lit.

Normal = 135-145 meq/lit.

Hypernatremia = Serum sodium level is about 145 meq/lit

Hypokalemia = Serum potassium level below 3.5-5 meq/lit

Normal = 3.5 - 5.0 meq/lit

Hyperkalemia = Serum potassium level above 5 meq/lit

Hypocalcemia: Serum calcium level below 4.5 meq/litri nor

Normal = 4.5 - 5.5 meq/lit bas viibios

Hypomagnesemia: Serum magnesium level below 1.5 meq/lit

Normal = 1.5-2.5 meq/lit

Hyper Magnesium: Serum magnesium level above 2.5 meq/lit