Parenteral Nutrition


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1 : Parenteral Nutrition Lori DeCosta RD CNSD Nutrition Support Dietitian New York Presbyterian Hospital
2 : Introduction to PN PN is the IV administration of nutrition for individuals who are not able to meet nutritional needs via PO intake or enteral nutrition PN includes dextrose, amino acids, lipids, vitamins and minerals as well as additives such as insulin
3 : History of PN First IV infusions date back to the 1600s 1968 - first parenteral nutrition infusions were introduced 1970s – development of parenteral trace element and vitamin requirements 1979 – development of lipid emulsions in US
4 : Routes of Infusion Peripheral Central
5 : Peripheral Parenteral Nutrition Given via peripheral vein using standard IV with 18-12 gauge needles Appropriate only for short-term use – IV must be changed every few days due to risk of phlebitis Osmolarity must be <900mOsm – Final PN formulation should not exceed 10% dextrose or 5% protein Lipids are isotonic – do not contribute to osmolarity of PPN solution
6 : Limitations of PPN Difficult to meet nutritional needs – must use high amount of volume due to osmolarity restrictions Patient must have good peripheral venous access Patient must be able to tolerate large volumes of fluid
7 : Calculating Osmolarity of PN Total grams of amino acids per liter x 10 + Total grams of dextrose per liter x 5 + Total meq of calcium, magnesium, potassium and sodium per liter x 2 = Total mOsm per liter of solution *if 3 in 1 (TNA) need to add IV lipids (total grams of fat per liter x 1.5)
8 : Central Peripheral Nutrition (TPN) Most commonly seen PN in hospital setting Able to meet 100% of nutrients needs with hyperosmolar formulation delivered to a large diameter vein such as the superior vena cava Given via central access PICC line (peripherally inserted central catheter) Standard Central Catheters (single, double, triple lumen) Tunneled Central Catheters Percutaneous Nontunneled Catheter (must be confirmed by x-ray) Implanted Catheters
9 : Types of Parenteral Nutrition “2 in 1” – lipids are administered in a bottle piggybacked to the IV line containing the dextrose/amino acid mixture and run over 8-12 hours (This is done at Cornell) “3 in 1” (Total Nutrient Admixtures – TNAs) dextrose, amino acids and lipids given in one solution (This is done at Columbia)
10 : Criteria for PN Three questions to ask when consulted for parenteral nutrition… Is the patient malnourished? Do they need nutrition support? - And most importantly, if yes to #2 - Can they be fed enterally? “If the gut works, use it!!” However, if patient unable to be fed enterally, then they may be candidate for parenteral nutrition.
11 : Enteral Nutrition vs. Parenteral Nutrition EN is safer, more physiological Less expensive Preserves gut integrity Prevents bacterial translocation Lesser risk of infection
12 : So, when do we use PN? Non-functional GI tract Non-accessible GI tract Peri-operatively for malnourished patients Favorable prognosis
13 : Typical Conditions Where PN is Appropriate Small Bowel Obstruction Small Bowel Fistula Pseudo-Obstruction Persistent Ileus not responding to medical treatment Short Bowel Syndrome Conditions requiring bowel rest Severe colitis Severe pancreatitis Intractable n/v/d Severe malabsorption
14 : Post-Operatively In general: Small bowel motility returns in 4 hours Gastric motility returns in 1-2 days Colon motility returns within 4 days
15 : Parenteral Feeding Methods Continuous (24hrs/day) – Best for hospitalized patients and/or until patient is stable on PN Cycled (10-18hrs/day) – For stable, long-term PN patient *For patient at home or rehab – allows for ambulation and freedom from pump *May also be used to “rest” the liver -If PN cycled, rate should be tapered for first and last hour of cycle to help avoid rebound hypoglycemia ex. 12 hour cycle: 110ml/hr x 10 hrs, 55ml/hr for 1st and last hour
16 : Components of Parenteral Nutrition Dextrose Amino Acids Lipids Electrolytes Vitamins Minerals Other additives
17 : Dextrose Most commonly used carbohydrate energy substrate Provides 3.4 kcal/g in its hydrated form rather than the 4 kcal/g found in dietary CHO due to a noncaloric water molecule attached to the dextrose molecule Available in concentrations from 5-70% Maximum Dextrose Infusion Rate = 5-7 g/kg/min or 4 g/kg/min in the critically ill
18 : Protein Crystalline amino acid solution – contains a mixture of essential and nonessential amino acids No glutamine or taurine in adult formulas Available in concentrations of 3-10% Provides 4kcal/g
19 : Lipids Used as source of essential fatty acids (EFA) Composed of soybean oil and/or safflower oil, egg yolk phospholipid (emulsifier) and glycerin (to render formulation isotonic) Emulsions using MCT available in Europe but not in US Available in 10% (1.1kcal/ml), 20% (2kcal/ml) and 30% (3kcal/ml) Note: fat contains 9kcal/g, but glycerol adds additional calories to IV lipids
20 : Lipids Provided over 8-12 hours (unless in TNA or 3 in 1) to prevent hyperlipidemia Total of 1g/kg/day should not be exceeded (especially in critically ill) Only needs to be 2-4% of total kcal to prevent EFA deficiency (or 2-3 times/week)
21 : Contraindications for Lipid Emulsions Severe egg allergy Give patient “test” dose If allergy severe enough, can rub vegetable oil into skin to try to prevent EFAD Hypertryglyceridemia (>400)
22 : Electrolytes Maintenance or therapeutic amounts added to PN depending on patient’s requirements General requirements: Sodium: 1-2 mEq/kg Chloride: as needed to maintain acid/base balance Acetate: as needed to maintain acid/base balance Calcium: 10-15 mEq Magnesium: 8-20 mEq Phosphate: 20-40 mmol
23 : Electrolyte Monitoring Amounts in PN adjusted daily based on patient’s lab results Higher amounts may be required at initiation of PN if patient at risk for refeeding syndrome Adjust for GI losses Some medication may change requirements Calcium:Phosphorus ratio must be <70mg/dl (4.8 mmol/L) to avoid precipitation
24 : Multivitamin MVI–13 (10ml) is the standard added to PN for adults Provides recommended amount of each vitamin and mineral for adults If needed, can add additional vitamins to PN bag or can double the MVI-13 in PN.
25 : Trace Elements MTE-4 (5ml): Standard which contains the recommended amounts of Chromium, Copper, Manganese and Zinc MTE-5 (5ml): same formulation as MTE-4, but with selenium. Needs to be added if patient on PN for >2 weeks Note: if t.bili is >=2.0, Cu and Mn must be omitted and other components are added separately to PN bag What trace element is missing? Iron – must be given by IV
26 : Other Additives Insulin General Guideline: give 0.1unit/g CHO/24 hours for IDDM patient 2/3rd of previous 24 hour coverage for NIDDM Should be adjusted daily depending on fingersticks until stable H2 Blockers Examples: Pepcid, Zantac, Tagamet
27 : Calculating Parenteral Nutrition Calorie needs: refer to standards of care Differ for medical and surgical patients Indirect calorimetry may be beneficial to prevent over/underfeeding Protein needs: refer to standards of care Usually between 1-2g/kg
28 : Calculating Parenteral Nutrition Fluid needs Need to consider all IV fluids patient is receiving when calculating volume to give of PN Assess fluid status: is patient fluid overloaded or dehydrated? Is patient being diuresed? Are serum sodium levels high or low? Is BUN/Cr elevated? Does the patient have adequate urine output? Can use 25-30ml/kg depending on patient’s age Or if >20kg, 1500ml + 15-20ml for each kg>20kg
29 : Calculating Parenteral Nutrition To determine patient’s goal: Determine kcal and protein needs Divide total kcal by 20-30% to determine how much IV lipids to provide Calculate kcal provided by protein and fat and subtract from total kcal goal. The amount left will be provided by dextrose.
30 : Example of PN Calculation 50 year old female who is 62 in and 50kg. Needs estimated at 1250kcal, 50-60g protein and 1500ml fluid/day Protein kcal: 60g amino acids x 4kcal/g = 240kcal Fat kcal: 1250 (total kcal) x 20-30% (.2-.3) = 250-375kcal (this is amount of kcal we want to provide from lipids). Since we have 20% lipid emulsion, will provide 300kcal from fat or 150ml (15ml x 10hrs) CHO kcal: 240 (kcal pro) + 300 (kcal fat) = 540kcal 1250 (total kcal) – 540 (pro and fat) =710kcal (this will be amount provided by dextrose 710/3.4 (dextrose has 3.4kcal/g) = 208g dextrose So, goal TPN will be 1.5L (62ml/hr x 24 hours) of 210g dextrose, 60g amino acids + 150ml 20% IV lipids
31 : Example of PN Calculation So, how do we calculate how many kcals this provides? 60g amino acids x 4kcal/g = 240kcal (protein) 210g dextrose x 3.4kcal/g = 714kcal (CHO) 150ml (20% IV lipids) x 2 = 300kcal (fat) Add 240 + 714 + 300 = 1254 total kcal This TPN provides 1254kcal and 60g protein
32 : Example of PN Calculation Now calculate the percentage of kcals from protein, CHO and fat Protein: 240kcal/1254 total kcal = 19% CHO: 712kcal/1254 total kcal = 57% Fat: 300kcal/1254 total kcal = 24% So, will our recommended TPN meet our patient’s nutritional needs?
33 : Non-Protein Kcal: Nitrogen Ratio(NPK:N2) In the past, it was thought that no kcals from protein were used for energy. We now know this to be untrue. The NPK:N2 ratio can be used to ensure that you are giving enough protein for protein synthesis
34 : Non-Protein Kcal: Nitrogen Ratio(NPK:N2) NPK are kcals from CHO and fat In example patient, we gave 300kcal from fat and 714kcal from CHO = 1014kcal NPK To determine grams of Nitrogen, take grams of protein and divide by 6.25: 60g amino acids/6.25 = 9.6g Nitrogen (N2) NPK:N2 ratio = 1014/6 = 106:1
35 : Non-Protein Kcal: Nitrogen Ratio(NPK:N2) What are goals for NPK:N2 ratio? 80:1 for most severely stressed patients 100:1 for severely stressed patients 150:1 for unstressed patients
36 : Initiating Parenteral Nutrition Volume: may start PN at desired volume Dextrose: start with 50-65% of CHO load (generally 100-150g dextrose) Can advance dextrose as indicated to 100% based on glycemic control Protein: can start with 50-100% Lipids: can start with 100% of lipids ONLY IF tryglycerides are <400
37 : Monitoring the PN Patient Tolerance of PN assessed by lab values such as glucose, electrolytes, LFTs, tryglycerides Baseline chemistry panel should be done prior to initiation of PN, then checked daily while on PN. May check 1-2 times/week once stable Tryglyercides should be checked prior to starting IV lipids and weekly thereafter LFTs should be checked weekly to assess for need to hold Cu and Mn Blood glucose should be checked every 6 hours once PN started until stable Weights should be checked 3 times/week
38 : Monitoring the PN Patient What are our responsibilities as the RD? Ensure patient is meeting nutritional needs via PN Goal is always to get patient off PN when possible Assist in transition to enteral feedings or PO diet PN should be stopped once patient tolerating 50-75% of estimated needs enterally
39 : Complications of Parenteral Nutrition Catheter-Related: Sepsis (related to insertion or line care, not PN) Infection Thrombosis Pneumothorax Air/catheter embolization or occlusion Macronutrient-Related: Hyperglycemia: most common! Hypoglycemia Essential Fatty Acid Deficiency Hypertryglyceridemia Azotemia
40 : Complications of Parenteral Nutrition Fluid and Micronutrient-Related Fluid and electrolyte abnormalities Vitamin deficiencies Trace element deficiencies Refeeding Syndrome – refers to the metabolic and physiological shifts of fluid, electrolytes and minerals that occur as a result of aggressive nutrition support in a malnourished patient
41 : Complications of Parenteral Nutrition Hepatobiliary: Steatosis: hepatic fat accumulation usually due to overfeeding. Usually benign, but can lead to fibrosis or cirrhosis. Cholestasis: impaired bile secretion or biliary obstruction. Serious condition that can lead to cirrhosis and liver failure. Gallbladder stones/sludge: due to gallbladder stasis. Related to lack of enteral stimulation (not the administration of PN). Lack of PO leads to decreased cholecystokinin (CCK) release and impaired bile flow and gallbladder contractility. May lead to acute cholecystitis
42 : Complications of Parenteral Nutrition Metabolic Bone Disease Osteoporosis Osteomalacia Etiology thought to be multifactorial, however poorly understood. May be related to vitamin D metabolism, hypercalciuria Activity, exercise and monitoring are the only “preventative” measures
43 : Patient Scenario 60 year old male with gastric cancer presents with n/v, inability to tolerate PO intake x 3-5 days at home. Appetite and PO intake has been suboptimal x months. Patient reports weight loss. After admission to hospital, NGT placed and patient with >1L output x 3 days. CT of abdomen/pelvis shows small bowel obstruction. Patient has now been NPO x 4 days in hospital. NSS consulted for TPN. Height: 68 inches UBW: 73kg (3 months ago) Current body weight: 65kg
44 : TPN Consult Questions to consider: Is the patient malnourished? Does the patient need nutrition support? Can he be fed enterally? Does he need TPN?
45 : TPN Consult What are patient’s nutritional needs? How do we estimate them? Patient is receiving maintenance IV fluids due to NPO status: D5 ½ NS at 75ml/hr Current labs: Glu 106, K 4.0, Mg 1.7, Phos 3.0, TG 134, t.bili 0.7, Alb 2.7
46 : Determination of TPN Formula Determine the amount of protein, dextrose and IV lipids you would give this patient. Show calculations.
47 : Conclusions! Parenteral nutrition should be reserved for those patients with non-functional or accessible GI tracts who are anticipated to be unable to meet nutritional needs orally or enterally for prolonged period of time May also be beneficial peri-operatively for those patients with underlying malnutrition Unlikely to benefit patients with end-stage metastatic disease

 

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