Parenteral Nutrition Flashcards
Define parenteral nutrition, list the two main types, and explain when it should be used.
Parenteral nutrition is the process of providing either partial or total nutrient requirements to a patient via the venous system. There are two main types, either peripheral parenteral nutrition (PPN) or total parenteral nutrition (TPN).
· PPN provides only some nutritional requirements and should only be used for a short while or as supplemental support. It involves infusing a low osmolarity solution of dextrose, electrolytes, amino acids, vitamins, fat and trace elements by using peripheral veins.
· TPN introduces higher concentrations of these components using a central vein and provides complete nutrition. Parenteral nutrition should only be used when oral or enteral routes cannot be utilized because if the gastrointestinal tract is resting, adverse side effects can occur. The time to consider starting parenteral nutrition is generally after 5 to 7 days after a patient has been unable to eat normally.
Explain specific situations where TPN would be chosen over other means of nutritional support.
TPN provides nutrition via a central vein and is riskier than PPN, but TPN also supplies greater nutritional needs without introducing large fluid volumes. TPN is utilized as the primary therapy for the gastrointestinal tract diseases short gut syndrome and enterocutaneous fistula. It is also provided in cases of allogeneic bone transplantation, acute Crohn’s disease, severe necrotizing pancreatitis, and uncontrollable nausea with vomiting. The use of TPN for diseases such as anorexia nervosa and inflammatory disease has not been proven but is common practice. Sometimes, total parenteral nutrition is employed as an adjunct for cancer patients, when septicemia is present, or during surgery or some other type of trauma. Disorders of the gastrointestinal tract and sometimes the respiratory tract indicate use of TPN in pediatric patients.
Describe the components involved in determining an individual’s total daily energy expenditure.
An individual’s total daily energy (TDE) expenditure is mixture of a number of components, and these need to all be considered to determine nutritional requirements. The largest component, accounting for up to about three-quarters of energy expenditure, is the basal energy expenditure (BEE), also called BMR. This is the base energy expenditure rate and can be estimated using formulas relating to weight, height, age and gender. A simpler estimation of BEE is 30 to 35 calories per kg of weight. The most accurate method to determine caloric requirements is indirect calorimetry which measures oxygen consumption and carbon dioxide production. The other components to total daily energy expenditure are activity level and the specific dynamic action (SDA) of food referring to the increased heat production that occurs during eating or receiving infusions.
Explain the criteria used to classify a patient as malnourished and describe the three types of malnutrition.
A patient is considered malnourished or at risk if they do not have adequate nutrient intake for a week or more or if they lose at least 10% of their body weight. This condition is primarily due to a lack of either protein or total caloric intake. There are three classifications of malnutrition. The first, marasmus, is a chronic condition where there is a slow wasting of the fat just below the skin (adipose) and somatic muscle occurs but the visceral proteins are still intact; its genesis is a reduced total dietary intake such as in starvation, anorexia, chronic illness or aging. Kwashiorkor, or hypoalbuminemia, can present when the diet is overwhelmingly carbohydrate in nature with little or no protein intake such as with liquid diets or use of IV dextrose solutions. In this case, the visceral protein stores are depleted and extracellular spaces fill up with water. A combination of the two, marasmus-kwashiorkor, sometimes occurs in hospitalized patients with pre-existing marasmus who are then treated with IV dextrose solutions. All of these can impair the immune system.
Identify some diseases of the esophagus, stomach or intestine that affect nutritional status.
Sometimes the ingestion of nutrients is immediately inhibited in the esophagus by an obstruction or the inability to pass the food. The stomach can be dysfunctional whereby food either cannot be ingested or passed onto the small intestine. Diseases such as a peptic ulcer or gastric cancer can cause these malfunctions, but in addition a mechanical obstruction or surgery may precipitate specific incidents such as delayed emptying or a rapid discharge (dumping syndrome). Intestinaldiseases are more common and include short bowel syndrome, a postoperative syndrome characterized by intense diarrhea and loss of fluid and electrolytes followed by subsequent ability to stabilize and adapt; inflammatory bowel disease (Crohn’s disease or ulcerative colitis) caused by decreased intake, increased output, or malabsorption; and pancreatitis, where patients usually cannot metabolize carbohydrates or absorb nutrients and have weight loss and other issues.
Name some liver and gallbladder diseases that affect nutritional status and explain why they do so.
The liver is a metabolic storage vehicle. In other words, a variety of metabolic processes occur there including protein synthesis, the elimination of the bile, metabolism of toxins and nutrient regulation. If the liver is impaired such as in hepatitis or cirrhosis of the liver, untoward metabolic changes occur such as glucose or protein intolerance or their synthesis, altered ability to process fats, an increased requirement for nitrogen, and impaired storage of trace elements. Dietary intake is impaired from loss through nausea and vomiting but also because of psychological problems or alcohol use. Cholecystitis, inflammation of the gallbladder as a result of infection or postoperative stress, can lead to poor intake or increased loss of nutrients as well. If there is a biliary tract obstruction, poor eating habits or increased protein and caloric requirements may occur. A condition called steatorrhea, or excess fat in the stools, can result because fats and fat-soluble vitamins are not absorbed.
Explain the physiological differences and nutrient imbalances in acute versus chronic renal failure.
Chronic renal failure usually occurs secondarily to a number of a number of other mouth or gastrointestinal conditions. These types of conditions lead to a wasting of the lean body tissue and muscle mass and concomitant fluid retention as well as increased nutrient requirements. Acute renal failure results from a number of the same conditions or as a precedent to a comatose situation. In this case, the acute episode may be precipitated by the buildup of toxic protein metabolites and electrolyte imbalance as a result of the severe breakdown of endogenous proteins.
Explain the bodily changes that occur in diabetes mellitus that affect nutritional status.
An individual with diabetes mellitus has difficulty properly taking in and metabolizing mainly carbohydrates but other nutritional needs are affected as well. A hallmark of diabetes mellitus is that highly elevated plasma glucose levels or increased blood sugars are observed which leads to glucose in the urine and osmotic diuresis. If glucose is infused, the patient has difficulty oxidizing it. Fat metabolism is affected as well with increased lysis of lipids, fat oxidation and glycerol turnover. There is a net protein catabolism either through increased breakdown or decreased synthesis.
Describe how chronic obstructive pulmonary disease can lead to malnutrition.
In patients with chronic obstructive pulmonary disease, or COPD, severe weight loss often occurs. An individual with COPD expends quite a bit of energy as well during their labored breathing plus at times they have an oxygen deficit which affects metabolism. This can lead to malnutrition, which for these patients is defined as being less than 90% of ideal body weight or losing more 15% of their weight. Weight loss sometimes approaches a quarter of their body weight. Another respiratory condition, acute respiratory distress syndrome, can occur in individuals taking bronchodilators or other drugs. In this condition, oxygen transport is depressed secondarily to low phosphate levels.
Explain what cancer cachexia is.
Chronic diseases can sometimes cause cachexia which is general physical and mental debilitation caused by weakness and appetite loss. Cancer patients often experience a form of it called cancer cachexia not only because of the tumor itself but because of the chemotherapy treatments they are receiving or they are depressed. Anorexia and severe malnutrition is common in these patients and a number of metabolic abnormalities develop. Protein levels are depleted through increased turnover, lipid reserves are depleted, and insulin resistance often develops.
Describe the effects of stress, trauma or burns on the metabolic process.
Stress, trauma or burns are all traumatic events that in general increase metabolism. Critically ill patients in particular often experience stress which can in turn create severe nutritional defects. The main reason for this is more cytokines are produced; cytokines are proteins which affect the metabolism of cells. In trauma, these metabolic alterations occur from the time of the incident until the completion of wound healing and recovery. After a burn injury, pathophysiologic changes are found to a large extent in the gastrointestinal tract and a condition called ileus, an incapacity of the intestine to pass its contents, can result. If the injury is severe, there is increased metabolism and nitrogen loss as well as greater energy consumption.
List the most common types of changes associated with nutritional deficiencies during physical assessment.
Signs of nutritional deficiencies are most commonly observed visually in the skin, hair, eyes or mouth of the patient being assessed by the health care provider. This is especially true for the skin, an area that can reveal a number of nutritional deficiencies. The individual may be deficient in vitamin A or essential fatty acids if their skin is dry or flaky or they present with follicular hyperkeratosis. If they have petechiae, vitamins C or K may be lacking. Niacin deficiency may be present if the individual has increased pigmentation on body parts with sun exposure, known as pellagrous dermatosis. If patients are malnourished, their hair can be dull and thinning or changing colors or they might have hair loss. Examination of the nails can reveal an iron deficiency. Patients with nutritional defects may have purple or very red tongues, mouth tears (due to B vitamins), shrunken taste buds, patchy teeth enamel (due to fluorine excess), or bleeding gums (associated with vitamin C deficiency).
Explain what anthropometric measurements are and why they may be unreliable.
Anthropometric measurements are physical evaluations of subcutaneous fat and muscle mass. The latter is in theory indicative of the somatic protein levels. However, these measurements can be unreliable because the measurements can be inflated by presence of swelling and or indeterminate because of inconsistencies of measurement. Height and weight would be considered anthropometric measurements as well but again the latter is more useful when done as a series of measurements. There is also another test called the creatinine-height index (CHI), which measures creatinine excretion in the urine. Theoretically, the amount of creatinine is proportional to the skeletal muscle mass but again inconsistencies in collection or dietary intake and renal disease can all affect results.
Describe some laboratory tests that are used as indicators of malnutrition.
Serum albumin is often used to assess the possibility of malnutrition because albumin is by far the most prevalent protein in the body, up to 65%, and it acts as a carrier protein. Albumin is synthesized in the liver and it also has a long half-life, 18 days. Therefore, its usefulness as an indicator of malnourishment or recovery is limited because low levels might be due to liver function or fluid changes instead or changes happen too slowly to measure accurately. Serum transferrin and prealbumin are also used as tests for levels of visceral protein. They are carrier proteins for iron and retinol-binding proteins respectively. Both proteins have shorter half-lives than albumin as well, 8 days for transferrin and one to two days for prealbumin. The retinol-binding protein itself is sometimes measured too, but its usefulness is limited because it has a very short half-life, 18 hours at most.
Name the commonly used immunological tests to assess malnutrition and explain their purpose.
Nutritional deficiencies as well as stress or disease states can affect immunocompetency. The two commonly utilized immunological tests to determine nutritional status are total lymphocyte count and delayed cutaneous hypersensitivity or anergy testing. A total lymphocyte count is a measurement derived from a routine differential blood count:
Total lymphocyte count = (% lymphocytes x white blood count)/ 100
Levels less than 1200/ mm3 suggests malnutrition. In delayed cutaneous hypersensitivity testing, a panel of four or more typical skin test antigens is injected into the skin. This injection should elicit a local inflammatory response within 48 to 72 hours to at least some of the antigens if the T lymphocytes are working properly. Anergy, the absence of response to any of these antigens, may indicate severe malnutrition.
Describe the factors included in measuring nitrogen balance.
Measurements of nitrogen balance represent the difference between nitrogen intake and output through excretion and other means. They are done to look at baseline nutritional status and then to follow the progress of nutritional support. The net nitrogen balance is directly related to the net in protein. Nitrogen intake is calculated as the protein intake divided by 6.25. Output is determined from urea nitrogen output plus estimations of other losses such as insensible and gastrointestinal. Nutrients should be increased if the expected positive nitrogen balance is not achieved.
Explain why fat is sometimes administered intravenously.
Explain how the administration of parenteral nutrition affects electrolyte or essential macronutrients.
List the functions of the 4 fat-soluble vitamins and give deficiency-associated symptoms.
