TPN Lecture Notes PDF

Parenteral nutrition (Part 2) Dr. Asmaa A. Elsayed Lecturer of Clinical Pharmacy  Acetate is converted to bicarbonate and this conversion appears to occur mostly outside the liver. Micronutrients Bicarbonate should never be added to...

Parenteral nutrition (Part 2) Dr. Asmaa A. Elsayed Lecturer of Clinical Pharmacy  Acetate is converted to bicarbonate and this conversion appears to occur mostly outside the liver. Micronutrients Bicarbonate should never be added to or co- 2- Acetate infused with PN admixtures. This can lead to the release of carbon dioxide and result in the formation of insoluble calcium or magnesium carbonate salts.  3- Vitamins Thiamine is an essential cofactor in carbohydrate metabolism. Deficiency of thiamine pyrophosphate prevents the formation of acetyl-CoA from pyruvate, which is instead converted to lactate via anaerobic metabolism, resulting in lactic acidosis. Parenteral multivitamins are added daily to the PN admixture and it contain 150 mcg of vitamin K in accordance with FDA recommendations. Patients with chronic kidney disease are at risk for vitamin A accumulation and potential toxicity. Serum vitamin A concentrations should be measured in patients with chronic kidney disease when vitamin A accumulation is a concern.  Trace elements Trace elements are essential cofactors for numerous biochemical processes. Trace elements added routinely to PN include zinc, selenium, copper, manganese, and chromium  Zinc is important for wound healing, and patients with high-output enterocutaneous fistulas, diarrhea, burns, and large open wounds may require additional zinc supplementation. Patients with chronic severe diarrhea, malabsorption, high-output enterocutaneous fistula, or short-bowel syndrome may also have increased selenium losses and may require additional selenium supplementation. Trace elements 01 02 03 Patients who are Patients with Copper deficiency chronically dependent cholestasis should have resulting in anemia, on PN may accumulate manganese and possibly pancytopenia, and chromium and copper restricted to manganese, resulting in death has occurred in avoid accumulation and PN-dependent patients high serum levels possible toxicity because these are when copper was because both elements known contaminants of omitted from the PN undergo biliary parenteral products that admixture. elimination. are used in the making of PN, Trace element status should initially be monitored periodically (eg, every 3 months) in patients at risk for trace element deficiency or accumulation. When stable, serum trace element concentrations can be monitored less frequently (eg, every 6–12 months). PN additives  Medication: In general, medications should not be added to PN. Examples of medication incompatibilities are Ceftriaxone (Ca), phenytoin (change PH), and iron dextran (trivalent cations destabilize the lipid emulsion in 3-in-1 PN formulations). Incompatible drugs should be administered through a separate intravenous catheter or a separate lumen of a central venous catheter, if possible. If an incompatible intravenous drug is to be administered through the same intravenous catheter as the PN, the PN should be stopped, followed by a compatible flush before and after drug administration. The volume of flush should be sufficient to clear the entire catheter of PN and of drug (typically about 10 mL if flushing the port closest to the patient).  Regular Insulin Only Regular insulin (compatible) may be added to PN admixtures for glycemic control. Adding insulin to PN (vs a continuous IV infusion) does not provide the flexibility of frequent titration. Generally, after the patient is receiving his or her goal dextrose dose in PN, about 50% to 70% of the total insulin doses administered over the previous 24 hours can be added to the next PN admixture. Caution should be used when insulin is added to PN to avoid hypoglycemia, especially when reversible causes of hyperglycemia have resolved (eg, stress, acute pancreatitis, corticosteroids therapy). Histamine-2 Receptor Antagonists IV histamine-2 receptor antagonists such as ranitidine, famotidine, and cimetidine are compatible with PN admixtures and can be added when indicated.  Heparin Heparin (0.5–1 unit/mL of final PN volume are added to PN admixtures for three reasons: Enhance lipid particle clearance Maintain Reduce as a cofactor for catheter patency Thrombophlebitis the lipoprotein lipase enzyme Heparin should be omitted in patients with active bleeding, thrombocytopenia, heparin-induced thrombocytopenia (HIT), or heparin allergy.  Parenteral iron dextran Chronic PN-dependent patients are at risk for iron-deficiency due to underlying clinical conditions and the lack of regular iron supplementation in PN. Parenteral Parenteral iron dextran should be used with caution due to its infusion- Ironrelated adverse effects. Iron dextran is compatible with 2-in-1 PN formulations but is not commonly added to PN admixtures due to incompatibility with IVFE. Other parenteral iron formulations (eg, iron sucrose, ferric gluconate) should NOT be added to PN admixtures due to a lack of compatibility data. Types of parenteral nutrition  Types of PN Formulations: 3-in-1 versus 2-in-1 PN admixtures can be prepared by mixing all components into one bag is referred to as a 3-in- 1 admixture or total nutrient admixture (TNA). , or IVFE may be infused separately (via a Y-site infusion or through a separate IV catheter or lumen) referred to as a 2-in-1 PN admixture. 2-in-1 admixture 3-in-1 admixture  2-in-1 formula 2-in-1 refers to PN in which all nutrients except for lipids are mixed in the same intravenous bag, lipids are administered by a separate infusion. Lipids are infused separately, using a 1.2-micron filter, no faster than 0.1 g/kg/hour in adults, rapid administration of lipids is associated with headache, fever, nausea, hypertriglyceridemia, dyspnea, cyanosis, flushing, sweating, and back or chest pain. Lipid infusion time should be less than 12 hours because of the potential for microbial growth after this time (growth is reduced when lipids are mixed with dextrose and AAs, as in the 3-in-1 described below, because of reduced pH and increased osmolarity). Administration tubing for a 2-in-1 should be changed every 24 hours; lipid tubing should be discarded after use (no longer than 12 hours).  3-in-1 Formula 3-in-1 (TNA) refers to PN in which all nutrients are mixed in the same intravenous bag. The stability of a 3-in-1 depends on the pH, which is determined primarily by the final AA concentration (maintain at least 4 %). Do not add concentrated dextrose directly to a lipid emulsion when mixing. Avoid excessive amounts of Ca2+ and magnesium. Administration tubing for a 3-in-1 should be changed every 24 hours. TNA should have a final concentration of amino acids ≥ 4%, monohydrated dextrose ≥ 10%, and injectable lipid emulsion ≥ 2%. COMPLICATIONS OF PN  Uncontrolled hyperglycemia can lead to fluid and electrolyte disturbances, hyperglycemic hyperosmolar nonketotic syndrome, hypertriglyceridemia, and an increased risk of infection. )Hyperglycemia can lead to nosocomial and wound infections( Hyperglycemia A portion of daily calories (~20%–30%) can be administered via IVFE to help decrease hyperglycemia, provided that the patient does not have hypertriglyceridemia. Overfeeding (with dextrose and with total calories) must always be avoided.  Hypoglycemia can occur in patients when PN is interrupted suddenly (reactive hypoglycemia), especially when patients are treated with insulin or as a result of insulin overdosing in PN. Can be avoided by tapering PN over 1 to 2 hours before discontinuation rather than abruptly stopping Hypoglycemia the infusion. If PN is interrupted abruptly (eg, because of lost IV access), infusing dextrose 10% in water or dextrose 10% NaCl 0.45% in water (to avoid excessive free water) at the same rate as PN should prevent hypoglycemia.  Patients receiving IVFE may be at risk for hyperlipidemia and hypertriglyceridemia. Hypertriglyceridemia may develop as a result of increased fatty acid synthesis caused by hyperglycemia, impaired IVFE clearance, in Hyperlipidemia/ patients with history of hyperlipidemia, obesity, diabetes, alcoholism, kidney failure, liver failure, Hypertriglyceridemia multiorgan failure, sepsis, or pancreatitis, or as a result of medications (eg, propofol, corticosteroids, cyclosporine, and sirolimus). Prolonging the infusion of IVFE may improve lipid clearance.  Hypercapnia Hypercapnia can develop as a result of overfeeding with dextrose and/or total calories. Excess carbon dioxide production and retention can lead to acute respiratory acidosis. Reducing total calorie and dextrose intake would result in resolution of hypercapnia if due to overfeeding.  Refeeding Syndrome Refeeding syndrome describes the metabolic disturbances that occur during Refeeding nutritional repletion of patients who are starved, underweight, or severely Syndrome malnourished. Hypophosphatemia, hypomagnesemia and hypokalemia (along with associated complications) are the classic signs and symptoms, with vitamin deficiencies (thiamine). Refeeding syndrome encompasses a constellation of fluid and electrolyte abnormalities affecting neurologic, cardiac, hematologic, neuromuscular, and pulmonary systems. Identify patients at risk (anorexia, cancer, chronically ill, poor nutritional intake for 1–2 weeks, alcoholics, recent unintentional weight loss, malabsorption). When initiating nutrition support, the rule of thumb to prevent refeeding Refeeding Syndrome syndrome is to “start low and go slow.” Initiate PN cautiously (Initially, provide less than 50% of caloric requirements on day 1) and gradually increase to goal over 3 to 5 days. Provide supplemental IV thiamine 100 mg/day and folic acid 1 mg/ day for about 1 week in addition to the standard multivitamin in PN.  Liver Complications Patients may develop a mild increase in liver transaminases within 1 to 2 weeks of initiating PN, but this generally resolves as PN continues, provided overfeeding is avoided. Severe liver complications include hepatic steatosis, steatohepatitis, cholestasis (bile flow obstruction), and cholelithiasis (Gallstones; a result of decreased gallbladder contractility, especially in the absence of enteral or oral intake). Hepatic steatosis: Hepatic steatosis is usually a result of excessive administration of carbohydrates or fats, deficiencies of carnitine, choline, and essential fatty acids also may contribute. Hepatic steatosis can be minimized or reversed by avoiding overfeeding, especially from dextrose and IVFE. Cholestasis: Factors that predispose to cholestasis: overfeeding, bowel rest, long duration of PN, short-bowel syndrome, bacterial overgrowth and translocation, and sepsis Cholestasis generally is reversible if PN is discontinued before permanent liver damage occurs. Cholelithiasis: Cholelithiasis can develop as a result of decreased gallbladder contractility, especially in the absence of enteral or oral intake. Lack of intestinal stimulation reduces secretion of cholecystokinin, a peptide hormone secreted in the duodenum that induces gallbladder contractility and emptying. The best prevention of cholelithiasis is early initiation of enteral or oral feeding.  Metabolic bone disease (MBD) A condition of bone demineralization leading to osteomalacia, osteopenia, or osteoporosis in patients receiving long-term PN. Often patients are asymptomatic, although symptoms can include bone pain, Metabolic back pain, Bone and fractures. Disease Factors that can predispose patients to developing MBD include deficiencies of phosphorus, calcium, and vitamin D; aluminum toxicity; amino acids and hyperosmolar dextrose infusions; chronic metabolic acidosis; corticosteroid therapy; and lack of mobility  Provide adequate calcium and phosphate with PN to improve bone mineralization and help to prevent MBD. Provide adequate amounts of acetate in PN admixtures to maintain acid–base balance Pharmacies should use products with the lowest labeled aluminum content for Metabolic bone disease the making of PN. Patients who are chronically dependent on PN should have their serum aluminum concentrations routinely monitored or whenever MBD is suspected or diagnosed.  Infectious Complications Patients receiving central PN are at increased risk of developing infectious complications caused by bacterial and fungal pathogens (Staphylococcus aureus and Candida albicans Strict aseptic techniques must be used when placing the catheter along with continuous care of the catheter and infusion site Catheter-related bloodstream infections support parenteral antimicrobial therapy and/or removal of the catheter  Mechanical Complications Central venous catheter must be placed by a trained professional, and risks associated with placement include pneumothorax, arterial puncture, bleeding, hematoma formation, venous thrombosis, and air embolism. Over time, the venous catheter may require replacement. Problems with the equipment include malfunctions of the infusion pump, IV tubing sets, and filters. Other complications: Thrombophlebitis: Peripheral venous thrombophlebitis can occur with peripheral catheter placement. Risk is increased by day 4 of catheterization; therefore, site should be rotated every 3 days. Fluid and acid base imbalance Fluid imbalance can occur. Acid-base imbalances are usually related to the patient’s underlying condition; however, excessive chloride salts in the PN can cause a metabolic acidosis, whereas excessive acetate salts in the PN can cause a metabolic alkalosis. Other complications: Aluminum toxicity More likely to occur in patients receiving long-term PN or in those with renal dysfunction (aluminum is eliminated renally) Accumulates in bone and interferes with bone Ca2+ uptake, causing osteopenia Neurotoxicity Gut atrophy can occur.