Parenteral Nutrition Audis Bethea, Pharm.D. Assistant Professor Therapeutics I. December 5 & 9, 2003

Transcription

1 Parenteral Nutrition Audis Bethea, Pharm.D. Assistant Professor Therapeutics I December 5 & 9, 2003 Required readings Mattox TW. Parenteral nutrition. Dipiro JT, Talbert RL, Yee CG, et al., eds. Pharmacotherapy: A Pathophysiologic Approach, 4 th ed. Appleton and Lange, Stamford, Connecticut, ; Objectives 1. Define parenteral nutrition (PN) and the clinical settings in which it should be used 2. Discuss the advantages and disadvantages of peripherally and centrally administered parenteral nutrition 3. Review the nutrient substrates used in PN 4. Identify potential complications associated with PN and measures to manage these complications 5. Design a plan for the initiation and discontinuation of PN that includes monitoring parameters to insure that the nutritional needs of a particular patient are being met 6. Identify adjustments in PN when provided with data from substrate utilization analyses (indirect calorimetry and nitrogen balance) 7. Design a plan for monitoring a patient receiving PN 1

2 Parenteral nutrition 1. Definition process of supplying nutrients via the intravenous route a. Synonyms hyperalimentation (HA), intravenous hyperalimentation (IHA), total parenteral nutrition (TPN), peripheral parenteral nutrition (PPN) 2. Indications a. Patients who cannot, will not, or should not receive nutrition enterally, orally, or the patient who cannot get enough nutrition by the enteral/oral route for 5-7 days 3. Route of administration a. PPN peripheral venous access i. Small, low flow vessels ii. Limited to low osmolar solutions due to high incidence of thrombophlebitis and extravasation b. TPN central venous access i. Large, high flow vessels such as inferior, superior vena cava, internal jugular (vessels close to the heart) ii. Less incidence of thrombophlebitis and extravasation with high osmolar solutions 2

3 Osmolarity calculations 1. Osmolarity limits a. Peripheral mosm/l b. Central 1800 mosm/l i. Increased osmolarity limits allows for increased concentrations of dextrose and amino acids to be delivered c. Osmolarity of additives (per 1% final concentration) i. Amino acids 100 mosm/l ii. Dextrose 50 mosm/l iii. Lipids 1.7 mosm/g iv. Electrolytes mosm/meq 2. PN Osmolarity = [(100 x AA%) + (50 x dextrose%) mosm/l] Intravenous catheters 1. Type of catheter used is determined by the type of solution to be infused and the period of time the patient will require therapy Type of access Non-tunneled CVC Tunneled CVC PICC Ports Length of therapy Weeks Months to years Months Months to years Modes of delivery 1. 2 in 1 (Dextrose, AA, electrolytes) with fat emulsion administered separately 2. 3 in 1 all parenteral nutrients in one bag a. Advantages: i. Decreased infection rate due to less venous line manipulation and risk of touch contamination ii. Fewer intravenous lines required for administration iii. Decreased preparation time iv. Ease of administration for home use v. Better delivery of fat soluble vitamins vi. Decreased incidence of bacterial growth in preparation 3

4 b. Disadvantages: i. Lipids may occlude central venous catheters ii. Addition of lipids creates compatibility concerns iii. Stability of the solution is decreased by the addition of lipids iv. Addition of lipids impairs visual inspection of precipitates 3. Cyclic PN parenteral nutrition provided over < 24 hours a. Advantages: i. Mobility allows for overnight infusion and daytime ambulation ii. Toxicity may decrease hepatic complications of continuous infusion such as cholestasis iii. Flexibility allows time for infusion of incompatible medications Designing parenteral nutrition 1. Carbohydrates (CHO) a. Dextrose monohydrate primary energy source in parenteral nutrition (3.4 kcal/g) b. Stock (manufactured) concentrations of dextrose range from 5-70% i. Dextrose 70% (D 70 W) most commonly used to prepare PN solutions c. Amount of CHO in a PN solution is dependant upon: i. Caloric requirements ii. Optimal balance of CHO and fat for non-protein calories (NPCs) d. CHO should be ordered as % of a PN solution or the # of CHO calories to be provided from a PN solution Example: D15% means 15% of the PN solution consists of CHO 2. Amino acids (AA) a. Highest source of energy in PN solutions (4 kcal/g) **NOT USED AS A ENERGY SOURCE** b. Standard AA solutions provide both essential, semi-essential, and non-essential amino acids i. Essential AA unable to be produced by your body; must be ingested from diet ii. Semi-essential body cannot produce in stressed states (significant illness) iii. Non-essential AA can be produced as long as adequate nutrition is maintained 4

5 c. Specialty formulations of AA are manufactured for patients with renal and hepatic dysfunction i. Advantage exists only in the stage of hepatic dysfunction ii. Specialty formulas (Hepatamine ) contain high amounts of branched-chain AA and low amounts of aromatic AA 1. Aromatic AA contribute to the development of hepatic encephalopathy d. AA solutions have high osmolarity which limits there use in PPN solutions 3. Intravenous fat emulsions (Lipids) a. Concentrated source of calories i. 10% solution provides 1 kcal/ml 20% solutions provides 2 kcal/ml b. Provide essential fatty acids (Linoleic and linolenic acid) c. Infused via PPN may provide protection from phlebitis associated with PPN administration d. Optimal lipid intake/supplementation is 20-40% of total daily calories e. < 10% of daily caloric intake consisting of lipids may lead to depletion of essential fatty acids 4. Electrolytes a. Small amounts of electrolytes are inherently present in AA solutions (acetate, phosphate) b. Sodium chloride, acetate, phosphate, lactate, bicarbonate (dosed as meq) c. Potassium chloride, acetate, phosphate (dosed as meq) d. Magnesium sulfate (dosed as meq) e. Calcium gluconate, glucepate, chloride (dosed as meq) f. Phosphorus sodium, potassium (dosed as mmol) 5. Chloride vs. acetate intake is depends on acid-base balance a. Generally use equal amounts to maintain balance (1:1 ratio) i. Metabolic acidosis maximize acetate ii. Metabolic alkalosis maximize chloride 6. Calcium and phosphorus are conditionally incompatible!! Compatibility depends on: a. Concentration of each in PN solution b. ph of PN solution concentration of dextrose and AA determines ph, dextrose = ph = precipitation c. Amount of time solution is mixed together risk of precipitation d. High temperatures decrease solubility of PN components = precipitation 5

6 e. Calcium gluconate is less likely to dissociate and precipitate vs. calcium chloride f. Magnesium concentration, Mg = precipitation 7. Rules of thumb for calcium and phosphorus solubility a. Method #1 meq Ca/L + (2 x mmol phos/l) 45 is OK OR b. Method #2 meq Ca/L x mmol phos/l 150 is OK Electrolyte Concentration (meq/l) Sodium Potassium Calcium* 0-15 Magnesium 0-25 Phosphorus* 0-20 *Amounts of calcium and phosphorus are dependent upon solubility **Ranges are not absolute and may vary depending upon patient requirements Additional PN additives 1. Intravenous vitamins a. Intravenous multivitamin preparations are designed to provide daily allowances b. Disease states may alter vitamin requirements c. Additional vitamin supplementation may be added to PN solution or provided separately d. IV vitamin solutions are unstable in direct light and must remain refrigerated to remain stable in PN solutions for > 24 hours e. Adult IV vitamin preparations do not contain vitamin K 2. Intravenous trace elements a. Intravenous preparations are designed to provide daily allowances b. Standard preparations contain Mn, Cu, Zn, and Se c. Additional trace elements may be added to PN solution or administered separately to supplement excessive losses i. Renal losses: zinc, chromium, selenium ii. GI losses: zinc, selenium, iron iii. Biliary losses: manganese, copper 6

7 3. Iron dextran a. High incidence of anaphylactic and infusion related reactions b. Reactions occurring during administration result in discontinuation of PN infusion and wasting of the solution c. Oral supplementation or IV administration that is separate from the PN solution is preferred 4. Insulin a. May be added to PN solution to prevent hyperglycemia induced by high dextrose (CHO) load b. Up to 10% of total amount of insulin added to PN solution may be lost via drug adsorption to the IV bag i. Advantages: 1. Tight control of blood glucose improves patient outcomes and decreases infection risk 2. Improves utilization of caloric sources and prevents consumption of protein as energy source ii. Disadvantages: 1. Addition of too much insulin to PN may result in hypoglycemia and discontinuation of PN infusion Potential complications of PN 1. Gastrointestinal atrophy 2. Infection a. Lipid > AA > Dextrose for supporting microbial growth b. Common organisms candida species, staphylococcal species 3. Hyperglycemia a. Increases infection risk b. Promotes utilization of protein as energy source 4. Venous extravasation a. Leakage of PN solution out of the vasculature may cause tissue necrosis and disfigurement 7

8 Guidelines/Hints for initiation and administration of PN Parameter Peripheral PN Central PN Initiation No tapering required Gradual tapering usually recommended Discontinuation No tapering required Tapering required unless taking sufficient EN Length of therapy NO more than 2-3 weeks Long-term Fluid tolerance Requires large amounts of fluid to provide full May be concentrated (requiring less fluid) to nutritional needs meet patient s needs Allowable dextrose % (usually limit to 5% if AA included or concentrations 10% w/out AA) Up to 35-40%, although rarely use > 25% Allowable AA concentrations Limited to osmolarity, typically 2.5% or less Up to 7% Costs Less expensive to prepare and fewer complications More expensive to prepare and higher rates of complications Monitoring parameters for PN Parameter Initiation of PN/Critically ill Stable PN therapy Vital signs Q4-6 hours Q12-24 hours Physical exam (abdominal exam, lung fields, mucus membranes, Q4-6 hours Q12-24 hours etc) Clinical assessment (weight, total intake/output, stool, N/V Daily Daily Assessment of tube placement Q6 hours Q12 hours Gastric residual checks Q4-6 hours Q8-12 hours Serum electrolytes, BUN/sCr, glucose Q12-24 hours 3-4 times/wk Serum calcium, magnesium, phosphorus Q24 hours 3-4 times/wk CBC Q24 hours Q24-48 hours Liver function test Q24 hours Weekly Trace elements Q24 hours Tailor to patient needs *Baseline assessments of all parameters must be obtained **Patients at risk of refeeding syndrome may require more frequent assessments ***These parameters are in addition to monitoring markers of nutritional status 8

9 Enteral Nutrition Audis Bethea, Pharm.D. Assistant Professor Therapeutics I December 5 & 9, 2003 Required readings Janson DD. Enteral nutrition. Dipiro JT, Talbert RL, Yee CG, et al., eds. Pharmacotherapy: A Pathophysiologic Approach, 4 th ed. Appleton and Lange, Stamford, Connecticut, ; Objectives 1. Discuss the advantages of enteral nutrition (EN) vs. PN 2. Identify contraindications to EN 3. Review the different feeding tubes available to provide EN 4. List macronutrient sources available in EN formulas 5. Explain a rationale for various disease-specific EN 6. Identify adjustments in EN when provided with data from substrate utilization analyses (indirect calorimetry and nitrogen balance) 7. Outline a plan for transitioning from parenteral to enteral nutrition 8. Design a plan for monitoring a patient receiving EN 9

10 Enteral nutrition 1. IF THE GUT WORKS USE IT!! 2. Enteral nutrition (EN) maintains several advantages over PN a. Advantages: i. Avoids risks associated with intravenous catheters (phlebitis and infection) ii. More physiologic due to stimulation of GI tract iii. Preserves the process of intestinal cell turnover associated with normal villi structure and enzymatic activity 1. GI tract provides means to extract nutrients 2. Prevents infection from translocation of bacteria from GI tract associated with gut atrophy 3. Maintains normal functioning of biliary system iv. Less costly 3. Contraindications to EN a. Malabsorptive disorder not allowing for adequate nutrient absorption b. Severe gastrointestinal diseases i. Necrotizing enterocolitis ii. Intestinal obstruction iii. Enterocutaneous fistula iv. Upper GI bleed* v. Adynamic ileus* vi. Intractable vomiting* vii. High risk of aspiration* *Indicates relative contraindication Administration of EN 1. Oral preferred rout for patient comfort provides no nutritional advantage 2. Feeding tubes Tube type Indication Advantages Disadvantages Nasogastric (NG) / Short-term, normal gastric Intermittent bolus or continuous Increased aspiration risk Orogastric (OG) emptying, intact gag reflex feeding Nasoduodenal (ND) Short-term, high aspiration risk, Reduced aspiration risk, allows Continuous feeding only or jejunal (NJ) abnormal gastric emptying for early post-op feeding Gastrosomy (PEG) Long-term, normal gastric emptying w/ impaired swallowing Intermittent bolus or continuous feeding, long-term use Surgically placed, aspiration risk, requires care of stoma site Jejunostomy (PEJ) Long-term, impaired gastric emptying, inaccessible upper GIT Reduced aspiration risk, allows for early post-op feeding Continuous feeding only, requires care of stoma site 10

11 3. Factors influencing choice of feeding tube a. Stomach i. Most physiologic ii. Stretch receptors in the stomach give the patient the sensation of being full iii. Tolerates a wide range of feeding formulas iv. Patient must have intact gag reflex b. Intestine i. Preferred in patients with gastroparesis or delayed gastric emptying ii. Patients at high risk of aspiration Duration of EN Short-term (< 30 days) Long-term (> 30 days) High risk of aspiration? Yes No Yes No Consider jejunostomy, PEG/PEJ PEG 11 NJ NG

12 4. Administration technique a. Bolus several hundred milliliters of formula are intermittently administered i. Bolus feeding is more physiologic due to activation of gastric stretch receptors ii. Bolus feeding cannot be administered via feeding tubes in the duodenum or jejunum iii. Typically will administer < 400 ml per bolus feed b. Continuous set amount of formula is delivered every hour for 24 hours per day i. Usually used in patients who have high nutritional requirements ii. Only option for administration of nutrition through feeding tubes in the duodenum or jejunum Sources of macronutrients in EN Nutrient Whole component Partially Hydrolyzed Elemental Carbohydrates Cereals, vegetables, fruits, milk, corn syrup, polysaccharides Oligosaccharides, disaccharides, maltose, sucrose, lactose, Monosaccharides, glucose, galactose maltodextrin Protein Egg, milk, wheat, caseinate salts Oligopeptides, dipeptides, tripeptides Amino acids Fat Meat, milk, eggs, soy, long-chain triglycerides, polyunsaturated fatty acids, fish oils, corn oil Medium-chain triglycerides, coconut oil, free fatty acids Classification of enteral formulas 1. Monomeric formulas (Peptamen, Vivonex ) a. Pre-digested amino acids to improve absorption b. Recommended for patients with altered GI function i. Peptide-based partially digested (Peptamen ) ii. Elemental most pre-digested form with proteins as free amino acids 2. Polymeric formulas (Osmolite, Complete modified, Resource, IsoSource ) a. Contains intact macronutrients in the form of triglycerides, protein, and CHO polymers b. Highly concentrated and fiber enhanced feeding formulas i. Lactose containing (Complete modified ) blenderized formulas made from natural whole foods (table food blenderized into liquid form) 12

13 ii. Lactose free majority (standard) of enteral formulas are lactose free c. Formulas require normally functioning GI tract and absorptive capacity 3. Specialized, disease specific formulas (Pulmocare, Nutrihep, Impact ) a. Formulas are modified for pulmonary, renal, hepatic, and endocrine failure b. Composition and nutrients vary with indication (modified to a specific disorder) c. Allows maintenance of nitrogen balance without exacerbating underlying disease d. Specialized formulas are extremely expensive 4. Feeding modules/caloric additives a. CHO (carbohydrate polymers) Moducal, Polycose b. Protein (casein, whey) ProMod, Casec c. Fat MCT oil, Microlipid, corn oil d. Fiber Unifiber Physical characteristics of enteral formulas 1. Osmolality increasing osmolality may decrease gastric emptying leading to diarrhea and dehydration 2. Estimated free water free water is usually dependent upon the formula s concentration a. < 1.5 kcal/ml 80% free water b. > 1.5 kcal/ml 70% free water c. Percentages account for the amount of water available to meet daily fluid requirements after the product is absorbed 3. Fiber/Residue content fiber supplementation may help to maintain normal bowel function Initiation/Advancement of enteral feedings 1. Intermittent (bolus) delivery a. Example: goal is 2000 kcal/day using a 1 kcal/ml formula i. Initial rate 120 ml q4 hours with 50 ml water flush ii. Advance increase rate by 60 ml q6-12 hours until goal rate is reached (goal rate = 330 ml/hr) 13

14 2. Continuous delivery a. Goal is 2000 kcal/day using a 1 kcal/ml formula i. Initial rate start at 30 ml/hr with 50 ml water flush q 4 hours ii. Advance 10 ml q 4-6 hours until goal rate is reached 3. Residuals amount of enteral formula and GI secretions left in the stomach or intestine a. Residuals are checked by aspirating (drawing out with a syringe) the contents of the GI tract i. High residuals 1. Poor gastric or intestinal transit/emptying 2. Increased risk for aspiration 3. Hold feeds if: a. Bolus feeding > 100mL b. Continous feeding > 1/2 of rate administered ii. Check residuals 1. Bolus feeding at the end of the feeding interval, before administration of an additional bolus 2. Continuous feeding following 4-6 hours of feeding 3. May check residuals q8-12 hours if patient has had minimal residuals x 3 checks b. Therapy for high residuals i. Hold enteral feedings ii. Initiate drug therapy with promotility agents 1. Metaclopramide 10 mg PO/IV q6 hours a. Adjust dose for renal insufficiency b. Antagonizes dopaminergic activity in the GI tract 2. Erythromycin 250 mg PO/IV q6 hours a. Adjust dose for severe renal and hepatic dysfunction b. Stimulates motilin receptors in the GI tract Transitioning from parenteral to enteral nutrition 1. Goal is to maintain total caloric intake while transitioning between feeding methods 2. After initiating enteral feeds decrease nutrients/fluids provided via PN by 1/3 to 1/2 3. Continue to decrease nutrients provided by PN as enteral feeds are increased towards goal 14

15 4. Usually can transition a patient from PN to enteral feeds within 1 to 3 days Drug interactions with enteral nutrition Drug Interaction Management Phenytoin Decreased bioavailability Administer phenytoin 2 hours prior to or following a feed Antibiotics (quinolones, tetracycline) Decreased bioavailability Administer antibiotics 2 hours prior to or flowing a feed, **interaction due to binding of drug with heavy metals in enteral formulas (Fe, Ca, etc.) Warfarin Antagonism of anticoagulant effect Increase warfarin dose to overcome effects of vitamin K in enteral formulas Sustained-release formulations Destruction of drug delivery system Cannot be administered via feeding tubes Enteric-coated formulations Destruction of enteric coating Administer enteric coated medication (non-crushed) with acidic juice, to maintain integrity of coating Administer crushed and mixed with 10 ml of 8.4% sodium bicarbonate to provide buffered environment for medication Administration of medications via feeding tubes 1. Flush the tube before medication administration with ml of water 2. Use liquid forms if at all possible. If liquid form is not available, crush tablet or empty contents of capsule 3. Give each drug separately, mixing non-liquid formulations with ml of water 4. Flush tube after medication administration with ml of water Monitoring parameters for EN Parameter Initiation of EN/Critically ill Stable EN therapy Vital signs Q4-6 hours Q12-24 hours Physical exam (abdominal exam, lung fields, mucus membranes, Q4-6 hours Q12-24 hours etc) Clinical assessment (weight, total intake/output, stool, N/V Daily Daily Assessment of tube placement Q6h Q12h Gastric residual checks Q4-6h Q8-12h Serum electrolytes, BUN/sCr, glucose Q12-24h 3-4 times/wk Serum calcium, magnesium, phosphorus Q24h 3-4 times/wk Liver function test Q24h Weekly Trace elements Q24h Tailor to patient needs *Baseline assessments of all parameters must be obtained **Patients at risk of refeeding syndrome may require more frequent assessments ***These parameters are in addition to monitoring markers of nutritional status 15