Fluids, Electrolytes, and Nutrition PDF

Fluids, Electrolytes, and Nutrition b. 4.  ral phosphorus products (e.g., K-Phos Neutral; also contain K+ and Na) can be used for asymptomO atic patients, but they are poorly absorbed. c. Symptomatic patients typically receive 15–30 mmol and sometimes up to 60 mmol (or 0.5–0.75 mmol/kg of IBW)...

Fluids, Electrolytes, and Nutrition b. 4.  ral phosphorus products (e.g., K-Phos Neutral; also contain K+ and Na) can be used for asymptomO atic patients, but they are poorly absorbed. c. Symptomatic patients typically receive 15–30 mmol and sometimes up to 60 mmol (or 0.5–0.75 mmol/kg of IBW) of phosphorus (sodium phosphate or potassium phosphate) administered intravenously over 3–6 hours (maximum rate is 7.5 mmol/hour). Note Na+ content (4 mEq per 3 mmol of phosphate) and K+ content (4.4 mEq per 3 mmol of phosphate). Phosphate shortages a. Reserve phosphate products for patients who need them most (e.g., children, neonates, diabetic ketoacidosis, refeeding syndrome, critically ill patients). b. Intravenous fat emulsions contain 15 mmol/L as egg phospholipids; this may be sufficient phosphate for some patients. C. Hyperphosphatemia 1. It typically occurs in patients with chronic kidney disease or hypoparathyroidism. 2. In general, patients are asymptomatic, but they can have signs and symptoms including hypocalcemia, ECG changes, paresthesias, and vascular calcifications. 3. For treatment, see Treatment of Hyperphosphatemia in the Nephrology chapter. X. DISORDERS OF CALCIUM HOMEOSTASIS A. N  ormal serum calcium concentration is 8.5–10.5 mg/dL (total Ca2+ includes bound and unbound Ca2+), and normal ionized calcium is 1.1–1.3 mmol/L (or 4.4–5.3 mg/dL). B. Distribution of Ca2+ 1. EC fluid contains less than 1% of the total body stores of Ca2+; 99% of total body stores of Ca2+ are in skeletal bone. a. About half of Ca2+ in the EC compartment is bound to plasma proteins (primarily albumin). b. The active form of Ca2+ is the unbound or ionized Ca2+. 2. Ionized Ca2+ is regulated by parathyroid hormone, phosphorus, vitamin D, and calcitonin. C. Hypocalcemia 1. It occurs in patients with chronic kidney disease, hypoparathyroidism, vitamin D deficiency, alcoholism, and hyperphosphatemia, and in patients receiving large amounts of blood products or patients undergoing continuous renal replacement therapy (CRRT [i.e., Ca2+ chelates with citrate used as anticoagulation in blood products or for plasmapheresis or CRRT.]) 2. Factors that cause an increase in EC Ca2+ binding to albumin (e.g., metabolic alkalosis) can cause a reduction in plasma ionized Ca2+ concentration, leading to symptomatic hypocalcemia. 3. A low serum albumin will cause a falsely low total serum calcium reading; therefore, an adjustment is necessary. Subtract a patient’s serum albumin from a normal serum albumin of 4 g/dL, multiply by 0.8 mg/dL, and then add to the total serum calcium concentration to correct the value. An ionized calcium level may be a more accurate measure of calcium in critically ill patients. 4. Signs and symptoms include tetany, muscle spasms, hypoactive reflexes, anxiety, hallucinations, lethargy, hypotension, and seizures. 5. Treatment a. Asymptomatic hypocalcemia associated with hypoalbuminemia is typically associated with normal ionized Ca2+ concentrations and therefore does not require treatment. ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-382 Fluids, Electrolytes, and Nutrition b. Asymptomatic hypocalcemia can be treated with oral Ca2+ supplements at a dose of 2–4 g/day of elemental Ca2+ in divided doses; patients may also require vitamin D supplementation. c. Symptomatic hypocalcemia is treated with 200–300 mg of elemental Ca2+ administered intravenously over 5–10 minutes, which in some cases is followed by a continuous infusion (e.g., in patients on CRRT). i. Equivalent to 1 g of calcium chloride (273 mg of elemental Ca2+) administered through a central intravenous catheter; peripheral administration of calcium chloride can result in severe limb ischemia ii. Equivalent to 2–3 g of calcium gluconate (180–270 mg of elemental Ca2+); preferred for peripheral intravenous administration iii.  Do not infuse Ca2+ at a rate faster than 60 mg of elemental Ca2+ per minute; rapid administration, which is not recommended, is associated with hypotension, bradycardia, or asystole. iv. The duration of an intravenous dose of Ca2+ is ideally 1–2 hours. If a continuous infusion is used, the rate should be 0.5–2 mg/kg/hour of elemental Ca2+. 6. Calcium shortages a. If there is a shortage of calcium gluconate, do not add calcium chloride to PN. Use multielectrolyte products in PN, if possible. b. The safety of diluted calcium chloride administered peripherally is unknown. D. H  ypercalcemia (serum calcium concentration greater than 10.5 mg/dL) is usually related to malignancy or hyperparathyroidism; see the chapters on Oncology Supportive Care and Nephrology. XI. ENTERAL NUTRITION A. I ndication and timing: EN is used in patients who are at risk of malnutrition and in whom it is anticipated that oral feedings will be inadequate for 5–7 days. Malnutrition is associated with poor wound healing and increased risk of infection. According to the American Society for Parenteral and Enteral Nutrition (ASPEN) guidelines, well-nourished adults without excessive metabolic stress can usually tolerate little to no nutrition for up to 7 days. The 2021 ASPEN and Society of Critical Care Medicine (SCCM) guidelines for critically ill patients recommend starting enteral feeding within the 48 hours after intensive care unit admission. B. EN contraindications 1. Complete intestinal obstruction 2. GI fistula (if a feeding tube cannot be placed distal to the fistula or if high-output fistula, which is defined as greater than 500 mL of output per day) 3. Extremely short bowel 4. Severe diarrhea or vomiting 5. Hemodynamic instability or intestinal ischemia 6. Paralytic ileus (however, many patients can be fed through the small bowel, despite an ileus) 7. Absence of bowel sounds is not a contraindication for the provision of EN (i.e., positive bowel sounds are not required for EN initiation), which promotes gut motility C. EN administration routes 1. Large-bore orogastric and NG tubes a. NG tubes are the most common tubes for short-term enteral access. b. Orogastric tubes are preferred in patients with nasal or facial trauma or sinusitis, but they are uncomfortable for alert patients. ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-383 Fluids, Electrolytes, and Nutrition 2. 3. c. These tubes can be used for stomach decompression in addition to feeding. d. Prolonged use can cause sinusitis or nasal mucosal ulceration. e. Patients with a gastric ileus will not tolerate NG feedings, and there is an increased risk of aspiration. Small-bore feeding tubes a. These tubes are most commonly placed through the nose, but they can also be placed orally in patients with nasal or facial trauma or sinusitis b. They can be placed with the feeding tube tip terminating in the stomach, but because they are smaller and more flexible than NG tubes, they can also be placed past the pyloric sphincter to improve tube feeding tolerance and prevent aspiration. c. Nasoduodenal tubes are also smaller than NG tubes, and they can clog from crushed medications if they are not flushed appropriately. Nasojejunal tubes are advanced into the fourth portion of the duodenum or past the ligament of Treitz. d. Patients with a gastric ileus or gastroparesis may tolerate feeding by the nasoduodenal or nasojejunal route. Percutaneous endoscopic gastrostomy tubes are placed through the abdominal wall into the stomach for patients requiring long-term feeding; jejunostomy tubes are placed through the abdominal wall into the jejunum, usually to facilitate immediate postoperative or postinjury feeding D. EN delivery 1. Gravity control refers to delivery with tubing that is fitted with a roller clamp to allow infusion into the stomach as desired. 2. Continuous infusion by an enteral feeding pump is usually used in hospitals because of the lower risk of aspiration compared with bolus feedings; it must be used for duodenal or jejunal feedings. 3. Cyclic feedings are administered continuously for 10–12 hours (overnight) to facilitate patient mobility during the daytime. 4. Intermittent bolus feedings of 100–300 mL for 30–60 minutes every 4–6 hours can be used only for feeding tubes ending in the stomach in stable patients. E. Benefit of EN 1. EN is preferred in patients with a functional GI tract because it is associated with a lower risk of infection than PN. Early administration of EN is associated with lower rates of infection and shorter lengths of stay. 2. GI mucosal atrophy occurs with an absence of EN or oral nutrition. This can increase the risk of bacterial translocation because of gut bacteria crossing the weakened intestinal barrier. F. EN formulations 1. Formulations typically contain carbohydrate, fat, protein, electrolytes, water, vitamins, and trace elements in varying amounts. 2. Intact or polymeric formulas are used in patients with normal digestive processes, and they typically contain 1–1.2 kcal/mL. a. These are generally inexpensive and an appropriate first choice for many patients. b. Some polymeric formulas are concentrated for patients requiring fluid restriction and contain 2 kcal/mL. c. Some polymeric formulas are designed for oral administration and are used to supplement the patient’s diet. 3. Elemental or semi-elemental formulas are easily digested by patients with impaired digestive capacity or malabsorption (e.g., short bowel, pancreatic insufficiency); they are typically more expensive than polymeric EN. ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-384 Fluids, Electrolytes, and Nutrition 4. 5. Some EN contains fiber for patients with constipation. Examples include Replete with Fiber and Jevity. Disease-specific EN a. EN formulations for patients with renal failure are typically concentrated (i.e., 2 kcal/mL to adhere to fluid restrictions) and can contain differing amounts of protein and electrolytes. b. Some EN products designed for patients with respiratory failure have more calories from fat (40%–55% of total calories) and fewer from carbohydrates to reduce the production of CO2 and facilitate ventilator weaning. However, excessive CO2 production is caused primarily by overfeeding with total calories rather than the total amount of carbohydrates; therefore, these more expensive formulations may be unnecessary as long as the patient is not being overfed. c. EN formulations for patients with diabetes have more calories from fat, fewer calories from carbohydrates, and added fiber to improve glycemic control. d.  EN formulations for patients with hepatic failure and hepatic encephalopathy contain more branched-chain AAs and fewer aromatic AAs, which may improve encephalopathy (controversial), but are not commonly used. e. EN for highly stressed patients (e.g., trauma, burn injury, acute respiratory distress syndrome, sepsis) is enhanced with protein, arginine, glutamine, omega-3 fatty acids, nucleotides, or betacarotene. These enteral formulations are designed to improve immune function and clinical outcomes. Immune-modulating formulas are recommended for surgical ICU patients in the postoperative setting, but are not recommended for the medical ICU population. f. Specialty formulas are not recommended for routine use in a general ICU setting. G. EN complications 1. Improper tube placement or displacement 2. Clogged feeding tubes a. Prevent by flushing feeding tube before, between, and after the administration of each drug. The use of liquid formulations of medications, if available, is also recommended. b. Unclog feeding tubes with warm water or a pancreatic enzyme solution mixed with oral sodium bicarbonate. Avoid using cola or juice. 3. Aspiration a. Prevent by keeping the head of bed elevated at 30–45 degrees. b. Prevent delays in gastric emptying using an EN formula with less fat. Gastric motility can be increased with metoclopramide (5–10 mg intravenously every 6 hours) or erythromycin (250 mg intravenously every 6–8 hours administered until tolerating EN for at least 24 hours). Metoclopramide and erythromycin can be combined, but monitor for diarrhea and tachyphylaxis. Avoid prolonged use of promotility agents because of increased risk of adverse effects. c. Administering EN by a feeding tube with the tip terminating beyond the pyloric sphincter can prevent aspiration pneumonia. d. Prevent also by initiating EN at a slow rate (e.g., 20 mL/hour) and advance every 4–6 hours as tolerated to goal rate. 4. Diarrhea a. It is more common with products with a higher osmolarity. b. Consider other causes of diarrhea such as antibiotic use, infection, lactose intolerance, magnesium, and sorbitol in liquid medication preparations (e.g., liquid acetaminophen). 5. Constipation can be prevented by adding fiber or bowel stimulation. 6. Dehydration ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-385 Fluids, Electrolytes, and Nutrition 7. Hypernatremia occurring when patients are given insufficient water while receiving EN a. Patients require about 30 mL/kg/day of water. b. Hypernatremia typically occurs in patients with altered mental status who may be unable to communicate thirst. c. Calorie-dense (i.e., 1.5 or 2 kcal/mL) EN formulas have less water than products containing 1 kcal/mL; therefore, additional water is needed to prevent hypernatremia. 8. Nasopharyngeal erosions, epistaxis, tracheoesophageal fistula 9. Sinusitis 10. Electrolyte abnormalities most likely to occur in patients who develop refeeding syndrome (discussed later) Patient Case 8. A 72-year-old woman (weight 65 kg) is switched from a standard enteral formula to a concentrated tube feeding designed for patients with kidney disease, because of hyperkalemia. The patient’s baseline and current SCr is 1.7 mg/dL, and her urine output is about 50 mL/hour. The tube feeding is infusing at a goal rate of 35 mL/hour through an NG feeding tube providing 2 kcal/mL, Na+ 41 mEq/L, and 717 mL/L of water. The patient’s serum sodium was 140 mEq/L when the tube feeding was initiated a few days ago, and her Na+ is now 145 mEq/L. What is the best approach for preventing hypernatremia in this patient? A. Change to an EN formula with a lower concentration of Na+. B. Administer intravenous D5W at 45 mL/hour. C. Administer 200 mL of water through a feeding tube every 4 hours. D. Reduce the tube feeding to 30 mL/hour. H. EN monitoring 1. Blood glucose concentration 2. Head of bed elevation to 30–45 degrees 3. GI tolerance a. Abdominal pain or distension b. Stool frequency and volume c. Nausea, vomiting, and diarrhea d. Checking gastric residuals is not recommended 4. Prealbumin weekly (exception: Caution in critically ill patients because it reflects acute-phase response rather than nutritional status); see goals in the Parenteral Nutrition section. 5. Serum sodium and other electrolytes 6. Wound healing a sign of adequate nutritional therapy 7. Other medications that add additional calories (e.g., propofol, clevidipine) that require EN rates to be adjusted ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-386 Fluids, Electrolytes, and Nutrition I. Developing an EN Regimen (Table 9) Table 9. Developing an EN Regimen Steps Determine caloric requirements Choose a formula and assess the calories per milliliter Determine infusion rate Ensure that patient will receive sufficient protein Ensure that the patient will receive about 30 mL/kg/day of water Calculation Guide 25–35 kcal/kg/day or estimate energy requirements using an equation such as the HarrisBenedict equation (see more details in Parenteral Nutrition section and Critical Care chapter) Usually 1, 1.2, 1.5, or 2 kcal/mL Example A 60-kg patient would require about 25 kcal/kg/day × 60 kg = 1500 kcal (Volume of EN)/24 hr See product information to find protein content (see protein requirements in Parenteral Nutrition section) See product information to find water content 1500 mL/24 hr = 62.5 mL/hr Replete with Fiber provides 64 g/L of protein; therefore, 1500 mL will provide 96 g of protein, or 1.6 g/kg for a patient weighing 60 kg Replete with Fiber provides 832 mL/L of free water. A patient receiving 1500 mL/day would need about 250 mL of additional water, which can be administered as water flushes through the feeding tube (i.e., 60–70 mL every 6 hr); it is important to consider other fluids that the patient may be receiving Choose a 1-kcal/mL formula EN = enteral nutrition. J. Drug administration using enteral access 1. Liquids are preferable, and they should be diluted with 2–3 times the medication volume with water to decrease osmolality. 2. Diarrhea can occur with medications having a high osmolality (e.g., medications mixed in sorbitol). 3. Flush with 20 mL of water before and after each drug administered. 4. Do not crush sustained-release or enteric-coated pills. 5. Mix crushed tablets or capsule contents with 10–15 mL of water and administer each drug separately. 6. It may be necessary to discontinue tube feedings before and after drug administration temporarily to prevent reduced bioavailability (e.g., fluoroquinolones, phenytoin, warfarin, bisphosphonates levothyroxine). 7. Consider feeding tube location and subsequent drug absorption (e.g., for efficacy, antacids need to be administered into the stomach, not the duodenum). ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-387 Fluids, Electrolytes, and Nutrition XII. PARENTERAL NUTRITION A. P  arenteral nutrition (PN) is the administration of intravenous nutrition in patients with a nonfunctioning or inaccessible GI tract in which the duration of PN is anticipated to be at least 7 days (i.e., it is anticipated that the patient will be unable to be fed orally or enterally for at least 7 days). In patients who are at high nutritional risk or severely malnourished and cannot tolerate EN, PN should be initiated as soon as possible. B. Indications for PN 1. Severe pancreatitis in patients who cannot tolerate EN 2. Peritonitis 3. Severe inflammatory bowel disease (e.g., Crohn disease, ulcerative colitis) 4. Extensive bowel resection (e.g., short bowel syndrome) causing malabsorption or maldigestion 5. Complete bowel obstruction 6. Severe intractable vomiting or diarrhea 7. Inability to meet full nutritional needs by enteral route alone (can use PN as supplement to EN) C. Intravenous infusion of PN (Table 10) Table 10. Estimating the Osmolarity of PN for 1 L of Solution Nutrient Amino acids Dextrose Lipid emulsion 10%–20% Sodium chloride/acetate Potassium chloride/acetate Calcium gluconate Magnesium sulfate Estimated Osmolarity 10 mOsm/g 5 mOsm/g 1.3–1.5 mOsm/g 2 mOsm/mEq 2 mOsm/mEq 0.68 mOsm/mL 4.06 mOsm/mL PN = parenteral nutrition. 1.  N should be administered through a central line. This includes any intravenous catheter (e.g., periphP erally inserted central catheter, Hickman, Port-A-Cath) where the tip of the catheter is in the superior vena cava or adjacent to the right atrium (femoral catheters should be avoided because of higher risk of venous thrombosis and catheter-related infection). 2. Peripheral access, which also includes midline catheters, is defined as the catheter tip position outside the central vessels or inferior or superior vena cava. If a peripheral vein is used for PN administration, the osmolarity must not exceed 900 mOsm/L. Peripheral administration can be used in patients with an appropriate indication for PN (see Indications for PN above) when central intravenous access is unavailable and the need for PN is expected to be less than 2 weeks. a. Final dextrose concentration should be 10% or less. b. Final AA concentration should be 2.5%–4%. c. Ca2+ concentration should be 5 mEq/L or less. d. K+ concentration should be 40–60 mEq/L or less. ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-388 Fluids, Electrolytes, and Nutrition 3. 4. 5. In hospitalized patients, PN is typically administered as a continuous infusion, which is infused over 24 hours. Ambulatory patients may prefer a cyclic PN in which the PN is usually infused for 12 hours. Infusions are generally better tolerated by patients if they are removed from the refrigerator and allowed to come to room temperature before infusion. D. Types of PN admixtures (Table 11) Table 11. 2-in-1 PN Compared with 3-in-1 PN Advantages Longer stability Visual inspection easier Filter using 0.22-micron filter (bacteria-eliminating) Lipids require 1.2-micron filter Time efficient for nurses Single bag with single tube and infusion pump Decreased vein irritation Inhibited bacterial growth 2-in-1 3-in-1 Disadvantages Increased nursing time Requires two sets of tubing and infusion pumps Increased bacterial growth in lipids Maximum 12-hr hang time of separate lipids Shorter stability (1–2 days) Complex compounding (without automated compounder) Visual inspection difficult Emulsion instability Must use 1.2-micron filter, not 0.22-micron Limited compatibility with medications Catheter occlusion more common 1. 2 -in-1 refers to PN in which all nutrients are mixed in the same intravenous bag, except for lipids, which are administered by a separate infusion. a. Lipids are infused separately, no faster than 0.1 g/kg/hour in adults, using a 1.2-micron filter b. Rapid administration of lipids is associated with headache, fever, nausea, hypertriglyceridemia, dyspnea, cyanosis, flushing, sweating, and back or chest pain. c. 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). d. 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). 2. 3-in-1 (also called total nutrient admixture) refers to PN in which all nutrients are mixed in the same intravenous bag. a. The stability of a 3-in-1 depends on the pH, which is determined primarily by the final AA concentration (maintain at least 4%). b. Do not add concentrated dextrose directly to a lipid emulsion when mixing (see order of mixing discussed later). c. Avoid excessive amounts of Ca2+ and magnesium (see recommended doses). d. Administration tubing for a 3-in-1 should be changed every 24 hours. e. Total nutrient admixtures should have a final concentration of amino acids ≥ 4%, monohydrated dextrose ≥ 10%, and injectable lipid emulsion ≥ 2%. ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-389 Fluids, Electrolytes, and Nutrition E. Premixed PN 1. Products available in the United States a. Clinimix is a two-compartment bag containing AAs in one compartment and dextrose in the other. This product is available with and without electrolytes. The seal between the two-compartment bag must be broken to mix the AAs and dextrose. Lipids can be added to the container after compartments are mixed or can be administered by Y-site. b. ProcalAmine is a solution containing 3% AAs, glycerin (4.3 kcal/g), and electrolytes in a single container, but it is not sufficient for most patients because of insufficient protein and calories. c. Kabiven, a newer solution, contains AAs, electrolytes, dextrose, and a lipid emulsion. It is available in a 3-compartment bag for central line administration only. Perikabiven is also available for use for peripheral and central administration. 2. Patient selection a. Evidence is insufficient to show that customized PN is superior to standardized premixed products. b. Consider in stable patients who require PN. c. Avoid in patients with fluid restriction or high protein needs. 3. Premixed products require fewer manipulations and have a lower risk of contamination and compounding errors, but they may still require additives (e.g., electrolytes, vitamins, trace elements). F. Nutritional components of PN formulation 1. Dextrose used for compounding PN is usually 70%, and it contains 3.4 kcal/g. Glycerol (or glycerin) is another carbohydrate source. Glycerol provides 4.3 kcal/g, and it is used in premixed parenteral products. 2. Fat emulsion is available as 10% or 20% and contains about 10 kcal/g; it is also available as a 30% formulation for compounding in 3-in-1 only. Smoflipid is available as 20%; it contains soybean oil, medium chain triglycerides, olive oil, and fish oil. Omegaven 10% is also approved for use in the United States. Intralipid is available as a 20% solution. 3. AAs are available as 3%–20% and provide 4 kcal/g. 4. Electrolytes are added to maintain physiologic serum concentrations. 5. Multivitamins and trace elements are added based on the recommended daily amount. G. Developing a PN regimen for administration through a central intravenous line 1. Determine caloric requirements. a. For patients with a body mass index (BMI) less than 30 kg/m2, administer 25–35 kcal/kg/day based on actual body weight [BMI = (Weight in kg)/(Height in meters)2]. It is important not to overfeed patients. The 2021 ASPEN/SCCM guidelines recommend feeding 12–25 kcal/kg during the first 7–10 days of an ICU stay (moderate quality of evidence, weak recommendation). These guidelines also advise clinicians to use their clinical judgment. b. If BMI exceeds 30 kg/m2, can administer 11–14 kcal/kg based on actual body weight or 22–25 kcal/kg based on IBW. i. Alternatively, some practitioners advocate using adjusted body weight (ABW) rather than IBW. ii. ABW = [(actual weight – IBW) × 0.25] + IBW. c. Hypocaloric feeding with high protein in EN and PN involves the administration of about 80% of caloric requirements, and it can be considered in patients with obesity (except in patients with kidney failure requiring hemodialysis and patients with hepatic failure; these patients have increased protein and caloric requirements to maintain a positive nitrogen balance). ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-390 Fluids, Electrolytes, and Nutrition d. 2. 3. 4. One method is to estimate basal energy expenditure (BEE) using the Harris-Benedict equation and multiplying by a stress factor.: i. Men: BEE = 66 + 13.7(Weight in kg) + 5(Height in cm) – 6.8(Age in years). ii. Women: BEE = 655 + 9.6(Weight in kg) + 1.8(Height in cm) – 4.7(Age in years). e. Energy expenditure can also be estimated through indirect calorimetry in critically ill patients (see the Critical Care chapter). Determine fluid requirements. a. Usually 30–35 mL/kg/day or 2500–3500 mL/day (for patients without fluid restrictions) to maintain urine output in the range of 0.5–2 mL/kg/hour b. Fluid requirements for patients with fluid restrictions (e.g., kidney or cardiac dysfunction) should be individualized. c. Do not use PN for fluid replacement but for maintenance fluid only. Determine protein (AA) requirements. a. For patients with a BMI less than 30 kg/m 2, protein is usually in the range of 0.8–2 g/kg/day based on actual body weight (may be higher in burn or trauma patients). i. Maintenance 0.8–1 g/kg/day ii. Moderate stress 1.3–1.5 g/kg/day iii. Severe stress 1.5–2 g/kg/day b. For patients with a BMI of 30–40 kg/m 2, can give protein 2 g/kg/day based on IBW. For patients with a BMI greater than 40 kg/m 2, can give 2.5 g/kg/day based on IBW. c. Patients with chronic kidney dysfunction may need protein restriction to prevent uremia. i. Kidney dysfunction without dialysis, 1 g/kg/day ii. Kidney failure with intermittent hemodialysis, 1.2–1.5 g/kg/day (1.5–2.5 g/kg/day if continuous renal replacement) d. Calories from protein (4 kcal/g) should be included in the total caloric provisions to prevent overfeeding. e. For 3-in-1 formulations, the final AA concentration should be around 4% to provide adequate buffering capacity and prevent lipid emulsion destabilization. f. Complete protein requirements can be provided on day 1 of PN (i.e., there is no need to slowly titrate up to recommended amount). Calculate remaining nonprotein calories and administer about 20%–30% of total calories as lipid and the remainder as dextrose. a. Make sure dextrose rate of administration does not exceed the maximum rate of hepatic oxidation rate of 4–5 mg/kg/minute (may be lower in critically ill patients, so monitor for hyperglycemia and adjust amount of dextrose provided if needed). i. Initial dextrose amounts can be in the range of 150–200 g/day. ii. May need to reduce to 100–150 g/day initially in patients with diabetes or stress-induced hyperglycemia; increase gradually during first 3–4 days to goals if blood glucose values are less than 140–180 mg/dL. b. A higher percentage of calories from lipid (up to 50%–60%, or 2.5 g/kg/day) can be provided for a short time in certain cases (e.g., hyperglycemia, hypercapnia). c. Essential fatty acid deficiency can be prevented by supplying approximately 2%–4% of total calories as lipid (can administer lipid emulsion once every 1–2 weeks). ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-391 Fluids, Electrolytes, and Nutrition 5. Estimate a daily maintenance amount of electrolytes, vitamins, and trace elements (Box 5). Box 5. Central PN calculations Example of a central 3-in-1 PN formula for a 70-kg patient hospitalized with ischemic bowel: 1. Total calories estimated as 30 kcal/kg × 70 kg = 2100 kcal 2. Fluid requirements estimated as 1500 mL + (20 mL/kg × 50 kg) = 2500 mL/day 3. Estimated protein needs are 1.5 g/kg × 70 kg = 105 g of protein. 4 kcal/g × 105 g = 420 kcal from protein; using 10% AA-based solution, will need 1050 mL to equal 105 g of protein (can round to 1000 mL if this makes compounding easier) 4. Determine calories from fat and dextrose. Total calories needed is 2100 − 420 kcal from AAs = 1680 remaining non–protein calories needed. Administer 25%–30% of total kilocalories as lipid, or about 500 kcal from lipid. Using 20% lipid emulsion, 250 mL is needed to equal 500 kcal (about 2 kcal/mL) Total calories needed is 2100 kcal − 420 kcal (AA) − 500 kcal (lipid) = 1180 kcal needed from dextrose. Assuming 3.4 kcal/g, about 350 g dextrose will be needed. Using a 70% base dextrose solution, 500 mL will be needed to equal 350 g, or 1190 kcal. Calculate the rate of dextrose administration in milligrams per kilogram per minute: [(350 g/24 hr) × (1000 mg/g) × (1 hr/60 min)]/70 kg = 3.5 mg/kg/min. This is an appropriate rate of dextrose administration. 5. The final formula will contain the following: AA 10%, 1050 mL Lipid 20%, 250 mL Dextrose 70%, 500 mL Electrolytes, multivitamins, and trace elements (about 110 mL) Final volume of 1910 mL to infuse at 1910 mL over 24 hours = 80 mL/hr (Final volume assumes the patient is receiving about 600 mL of fluid from other medications to meet fluid requirements) 6. Final concentration of macronutrients in PN is: AA 105 g/1910 mL final volume = 5.5% Lipid 50 g/1910 mL = 2.6% Dextrose 350 g/1910 mL = 18% 7. F  inal caloric value of PN is: AA 105 g × 4 kcal/g = 420 kcal Lipid 50 g × 10 kcal/g = 500 kcal Dextrose 350 g × 3.4 kcal/g = 1190 kcal Total calories = 420 + 500 + 1190 = 2110 kcal/70 kg = 30 kcal/kg 24% of total calories are provided as lipid AA = amino acid; PN = parenteral nutrition. a.  lectrolyte abnormalities should be addressed and corrected before PN is initiated. Avoid replacing E electrolyte deficiencies using PN in acutely ill patients. b. Maintenance electrolytes (amounts will vary and should be individualized) i. Sodium 60–150 mEq/day (1–2 mEq/kg/day) ii. K+ 40–80 mEq/day (1 mEq/kg/day) iii. Phosphate 10–40 mmol/day (or 15 mmol/1000 kcal) iv. Ca2+ 10–15 mEq/day (gluconate is preferred to prevent incompatibilities) v. Magnesium 8–20 mEq/day (sulfate form is preferred to Cl to prevent incompatibilities) vi. Cl and acetate salt forms to maintain acid-base balance. ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-392 Fluids, Electrolytes, and Nutrition vii. Electrolyte adjustment (a) Typically, greater amounts of magnesium, phosphorus, and K+ will be needed during the first few days of PN because of IC shifts. (b) Cl and acetate salt forms can be adjusted as needed to maintain acid-base balance (discussed under Monitoring Patients Who Are Receiving PN). c. Standard trace elements containing selenium, chromium, copper, manganese, and zinc (e.g., MTE-5) i. Patients with high-output fistulas, diarrhea, burns, or large open wounds may require additional zinc supplementation. ii. Patients with chronic diarrhea, malabsorption, or short-gut syndrome or those with critical illness may require additional selenium supplementation. iii. Patients with severe cholestasis should have copper and manganese restricted to prevent accumulation and toxicity because both undergo biliary elimination. d. Parenteral multivitamin added daily (generally contains 150 mcg of vitamin K). i. Additional thiamine (25–100 mg) can be supplemented in patients with a history of alcohol abuse. ii. During shortages of parenteral vitamins, can reduce frequency of administration to three times/week or can administer individual vitamins daily (i.e., thiamine, ascorbic acid, niacin, pyridoxine, folic acid) or monthly (i.e., vitamin B12) H. Developing a PN regimen for administration through a peripheral intravenous line (Box 6) Box 6. Peripheral PN Calculations Example of a peripheral 3-in-1 PN formula for a 70-kg patient: (remember osmolarity should not exceed 900 mOsm/L) 1. Total calories estimated as 30 kcal/kg × 70 kg = 2100 kcal 2. Fluid requirements estimated as 1500 mL + (20 mL/kg × 50 kg) = 2500 mL/day; prescriber wants PN to contain no more than 2000 mL 3. Calculate amount of dextrose as 2000 mL × 10% = 200 g of maximum dextrose recommended 4. Calculate amount of AA as 2000 mL × 3% = 60 g 5. Add about 500 kcal as lipid (can add more if patient tolerates). 6. Calculate volume so far. Using 70% dextrose, need 286 mL to equal 200 g of dextrose. Using 10% AA, will need 600 mL to equal 60 g. Using 20% lipid, will need 250 mL. Will add electrolytes, trace elements, multivitamins, and enough sterile water for a total volume of 2000 mL 7. Final formula will contain the following: AA 10% 600 mL Lipid 20% 250 mL Dextrose 70% 286 mL Electrolytes, multivitamins, and trace elements Sterile water added for 2000 mL final volume to infuse at 2000 mL/24 hr = 83 mL/hr 8. Final concentration of macronutrients in PN is: AA 60 g/2000 mL final volume = 3% Lipid 50 g/2000 mL = 2.5% Dextrose 200 g/2000 mL = 10% 9. Final caloric value of peripheral PN is: AA 60 g × 4 kcal/g = 240 kcal Lipid 50 g × 10 kcal/g = 500 kcal Dextrose 200 g × 3.4 kcal/g = 680 kcal Total calories = 240 + 500 + 680 = 1420 kcal/70 kg = 20 kcal/kg 35% of total calories are provided as lipid AA = amino acid; PN = parenteral nutrition. ACCP Updates in Therapeutics® 2023: Pharmacotherapy Preparatory Review and Recertification Course 1-393