2024_Fluids & Electrolytes.pdf

FLUIDS & E L E C T RO LY T E S IMBALANCES Dr. Tarek Kassem, PharmD, BCPS,BCACP. 1 1. Recommend an appropriate intravenous fluid regimen and monitoring parameters given a patient clinical scenario. 2. Discuss the appropriate roles and risks of hyperto...

FLUIDS & E L E C T RO LY T E S IMBALANCES Dr. Tarek Kassem, PharmD, BCPS,BCACP. 1 1. Recommend an appropriate intravenous fluid regimen and monitoring parameters given a patient clinical scenario. 2. Discuss the appropriate roles and risks of hypertonic and hypotonic saline, recommend treatment regimens, and discuss appropriate monitoring parameters to ensure safe and effective use of these intravenous fluids. 3. Assess electrolyte abnormalities and recommend an appropriate pharmacologic treatment plan based on individual patient signs and symptoms. LEARNING OBJECTIVES 2 C H A P T E R L AYO U T 1-FLUID M A N AG E M E N T 2 - E L E C T RO LY T E IMBALANCES 3  Distribution of total body fluid (TBF) 01 02 03 Total body water Total body water is A healthy adult (weight depends on the relative typically estimated as 70kg) has about 42 L of proportions of muscle 50% of body weight in fluid and fat in the body. women and 60% in men, as women, on average, have a higher proportion of fat to body weight. 4  40% 60% 60% of TBF is 40% of TBF is intracellular extracellular (enclosed by the cell membrane) 75% of extracellular 25% of extracellular fluid is fluid is interstitial (this intravascular[plasma] fluid “bathes the cells” (about 3-5 L of blood volume) and is separated from ICF= Intracellular Fluid intravascular space by the ECF=Extracellular Fluid semipermeable capillary TBF= Total Body Fluid membrane) 5.. IF 30% TBF Blood Vessels 10% Cell TBF 60% TBF 6  NOTES ✓ The ICF and ECF fluid compartments are separated by cell membranes, which are highly permeable to water. ✓ The ECF compartment is also divided into the interstitial (IS) space and the intravascular space; the IS and intravascular fluid compartments are separated by the capillary membrane, which is permeable to almost all solutes except proteins ✓ The approximate distribution of TBF into the IC and EC compartments with further distribution of the EC fluid into the IS and intravascular compartments is important to remember for determining the distribution of intravenous fluid. 7  Crystalloids are intravenous fluids that can contain water, sodium (Na+ ), chloride (Cl– ), and other electrolytes. Intravenous Fluids [IF] Lactated Ringer solution is a crystalloid that contains mostly Na+ and Cl– , but also lactate, ARE EITHER (K+ ), Ca2+ CRYSTALLOIDS Normosol-R and Plasma-Lyte are crystalloids OR COLLOIDS that contain mostly Na+ and Cl– but also acetate, K+ , and(Mg2+) D5 W is also a crystalloid, but it should not be used for fluid resuscitation because of the smaller amount of fluid that remains in the intravascular compartment. 8  Na and Cl do not freely cross into cells, but they will distribute evenly in the EC space. For 0.9% sodium chloride or Crystalloids LR solution, only 25% remains in the intravascular space, 75% NaCL in IS When 1 L of 0.9% sodium chloride or LR solution is administered, about 250 mL of fluid remains in the intravascular compartment. 9  Crystalloid D5W D5 W is isosmotic, and, because of rapid metabolism, it has the net effect of administering “free” water. D5 W is metabolized to water and carbon dioxide. Water can cross any membrane in the body; therefore, it is evenly distributed in TBF (“free” because it is free to cross any membrane). Many experts avoid administering D5 W whenever possible in patients with neurologic injury and elevated intracranial pressure (ICP) because it can cross into cerebral cells, causing further elevation in ICP. Some practitioners avoid the use of D5 W because of the risk of hyperglycemia 10  D5W For D5 W, 60% distributes to the IC space and 40% distributes to the EC space. Of the 40% distributed to the EC space, 25% remains in the intravascular space, and 75% distributes to the IS space. Therefore, when 1 L of D5 W is administered intravenously, about 100 mL of fluid remains in the intravascular compartment. 11  NOTE: The body may convert D5W into free water, but it is isotonic when administered. With few exceptions, all fluids should be isotonic when injected into the IV space. Do not under any circumstances inject water directly into a patient. Hypotonic fluids can very quickly cause death to your patient when administered IV. Give me sugar in water 12  Notes 01 02 03 Effective osmoles are Addition of an isoto Adding a hypertonic solutes that cannot nic solution to ECF solution to ECF decr freely cross cell mem does not change ICF eases ICF volume, branes, such as Na volume because Adding a hypotonic and K. there is no change in solution increases it. effective osmolality 13  14 https://www.thoughtco.com/osmotic-pressure-and-tonicity-3975927  Distribution of intravenous fluid Intravenous Fluid Infused Volume (mL) Equivalent TONICITY Intravascular Volume Expansion (mL) Normal saline 1000 250 Isotonic Lactated Ringer 1000 250 Isotonic solution Normosol-R and 1000 250 Isotonic Plasma-Lyte 5% Dextrose 1000 100 Hypotonic Albumin 5% 500 500 Hypertonic Albumin 25% 100 500 Hypertonic 15  COLLOIDS 1. Packed red blood cells 2. Pooled human plasma (5% albumin, 25% albumin, and 5% plasma protein fraction) 3. Semisynthetic glucose polymers (dextran) 4. Semisynthetic hydroxyethyl starch (hetastarch). 16 COLLOIDS Too large to cross the capillary membrane, therefore, they remain primarily in the intravascular space (although a small portion “leaks” into the IS space). Except for 25% albumin, administering 500 mL of colloid results in a 500-mL intravascular volume expansion. Because 25% albumin has an oncotic pressure about 5-fold that of normal plasma, it causes a fluid shift from the IS space into the intravascular space. For this reason, 100 mL of 25% albumin results in around 500 mL of intravascular volume expansion. The term "oncotic" refers to the osmotic properties of colloids, specifically proteins, in the blood. It is derived from the Greek word "onkós," which means swelling or bulk. 17  NOTES This hyper oncotic solution should generally be avoided in patients requiring fluid resuscitation, because although the intravascular space expands, fluid shifts out of the IS space, potentially causing dehydration. It may be useful in patients who do not require fluid resuscitation but who could benefit from a redistribution of fluid (e.g., ascites, pleural effusions) 18  Notes Hydroxyethyl starch and dextran products have been associated with coagulopathy and kidney impairment. In addition to acute kidney injury, hydroxyethyl starch is associated with increased mortality in critically ill patients. 19  ✓ Fluid replacement can be in two forms, either resuscitation or maintenance. ✓ Intravascular fluid depletion can Fluid occur because of shock, and it is associated with reduced cardiac Resuscitation function and organ hypoperfusion. ✓ Signs or symptoms usually occur when about 15% (750 mL) of blood volume is lost (e.g., hemorrhage) or shifts out of the intravascular space. 20 Signs and Symptoms of Intravascular Volume Depletion Tachycardia HR > 100 beats/minute) Hypotension (SBP < 80 mm Hg) Reduced urine output 0.5 mL/kg/hr Increased BUN/SCr ratio > 20:1 Dry mucous membranes Decreased skin turgor Dizziness BP = blood pressure; BUN = blood urea nitrogen; HR = heart rate; SBP = systolic blood pressure; SCr = serum creatinine. 21  Fluid Resuscitation ✓ Fluid resuscitation is indicated for patients with signs or symptoms of intravascular volume depletion. ✓ The goal of fluid resuscitation is to restore intravascular volume and to prevent organ hypoperfusion. ✓ Because intravascular volume depletion can cause organ dysfunction and death, prompt resuscitation is necessary. 22  Fluid Resuscitation Intravenous fluids are infused rapidly,[IV BOLUS] preferably through a large-bore catheter. Intravenous fluids are administered as a 500- to 1000-mL bolus, (~30 mL/kg in septic patients) after which the patient is reevaluated. This process is continued as long as signs and symptoms of intravascular volume depletion are improving. Max volume 4-6 L of crystalloid. 23  Content of Common Crystalloid Solution Contents (mEq/L) Osmolarity (mOsmole/L) Sodium chloride 0.9% (NS) Na 154 308 Cl 154 Lactated Ringer (LR Na 130 Cl 109 273 K4 Ca 3 Lactate 28 Normosol-R Na 140 Cl 98 295 K5 Mg 3 Acetate 27/Gluconate 23 24  Crystalloids are recommended for fluid resuscitation in hypovolemia. Notes Lactated Ringer solution is historically preferred in surgery and trauma patients, but no evidence suggests superiority over normal saline for fluid resuscitation in these settings There is no difference between crystalloids and colloids in the time to achieve fluid resuscitation or in patient outcomes. 25  Colloids have not been shown to be superior to crystalloids. COLLOIDS USE They are associated with higher cost and some adverse effects. ? Colloids can be considered after fluid resuscitation with crystalloid (usually 4–6 L) has failed to achieve hemodynamic goals or After clinically significant edema limits the further administration of crystalloid. 26  Colloids Albumin can be considered in patients with a low albumin concentration who have required a large volume of resuscitation fluids or in cirrhotic patients receiving a large volume paracentesis. Albumin (theoretically, 25% is preferred) can be considered in conjunction with diuretics for patients with clinically significant edema (e.g., pulmonary edema causing respiratory failure) and a low albumin concentration, when appropriately dosed diuretics are ineffective 27  Maintenance intravenous fluids Maintenance intravenous fluids are indicated in patients who are unable to tolerate oral fluids. The goal of maintenance intravenous fluids is to prevent dehydration and to maintain a normal fluid and electrolyte balance. Maintenance intravenous fluids are typically administered as a continuous infusion through a peripheral or central intravenous catheter. 28  1500 mL for the first 20 kg plus 20 mL/kg for every kilogram greater than 20 kg or Common methods of Administer 20–40 mL/kg/day (for adults only). estimating the daily volume in children and A typical maintenance intravenous fluid is D5 W with 0.45% sodium chloride plus adults: 20–40 mEq of potassium chloride per liter. It is recommended to add sodium bicarbonate to D5 W or sterile water for injection instead of 0.9% sodium chloride. 29  A 79-year-old man was brought to the emergency department by his son for worsening confusion and diarrhea. The sun reports he has had poor oral intake A) 0.45% NS over the past week. Medical history is significant for B) 0.9%NS hypertension, ischemic stroke, reflux, and chronic constipation. Medications include aspirin, lactulose, C) 5% Dextrose lisinopril, ranitidine , and pravastatin. His physical examination is significant for orthostatic hypotension, D) A+C tachycardia, and dry mucous membranes. Significant laboratory values include serum sodium of 162, BUN of 66, and serum creatinine of 2.5. Appropriate initial treatment for this patient would include which of the following? 30 A 74-year-old woman (weight 72 kg) arrives in the emergency department with a 3-day history of cough, body temperature of 102°F (38.9°C), and lethargy. She has the following vital signs and laboratory values: blood pressure 72/40 mm Hg, heart rate 115 beats/minute, urine output 10 mL/ hour, and blood glucose 82 mg/dL. After a 500-mL fluid bolus of 0.9% sodium chloride, her blood pressure is 80/46 mm Hg and her heart rate is 113 beats/minute. Her chest radiograph is consistent with pneumonia. Her medical history includes coronary artery disease and arthritis. Which is the most appropriate treatment at this time? A. 1000-mL fluid bolus with 0.25% sodium chloride. B. B. 5% albumin 500 mL infused over 4 hours plus norepinephrine titrated to maintain a systolic blood pressure of 90 mm Hg or higher. C. C. 1000-mL fluid bolus with 5% dextrose (D5 W) and 0.9% sodium chloride. D. D. 1000-mL fluid bolus with 0.9% sodium chloride 31 Intravenous fluids can be classified by their osmolarity relative to plasma. i. Isotonic fluid does not result in a fluid shift between fluid compartments because the osmolarity is similar to plasma. ii. Hypertonic fluid, such as NaCl 3%, can cause fluid to shift from the IC to the EC compartment, with subsequent cellular dehydration and shrinkage. iii. Hypotonic fluid, such as NaCl 0.225%, with an osmolarity less than 150 mOsm/L can cause fluid to shift from the EC to the IC compartment, with subsequent cellular overhydration and swelling. 32  Plasma osmolality is normally 275–290 mOsm/kg OsmolaLity is a measure of the osmoles of solute per kilogram of solvent (Osm/kg) OsmolaRity is a measure of osmoles of solute per liter of solution (Osm/L) Plasma osmolarity (mOsm/L) can be calculated as osmolality × 0.995 There is no clinically significant difference between them (i.e., plasma osmolarity is about 1% lower than plasma osmolality) 33 OSMOLALITY[280 mOsm/kg] i. Increases in plasma osmolality cause an osmotic shift of fluid into the plasma, resulting in cellular dehydration and shrinkage. ii. Decreases in plasma osmolality cause an osmotic shift of fluid into cells, resulting in cellular overhydration and swelling. iii. Plasma osmolality : (2 × Na+ mEq/L) + (glucose mg/dL/18) + [(BUN mg/ dL) ÷ 2.8] iv. Red blood cell swelling can cause cell rupture (i.e., hemolysis). v. Brain cells can swell, causing cerebral edema and herniation; this is most likely to occur with rapid sodium lowering 34 HYPERTONIC SALINE CONCENTRATIONS 3% [954 mOsm/L] 7.5% [2393 mOsm/L 23.4% [7462 mOsm/L] 35 HYPOTONIC INTRAVENOUS FLUIDS Hypotonic fluids administered intravenously can cause cell hemolysis and patient death Quarter normal saline, or 0.225% sodium chloride Half normal saline, or 0.45% sodium chloride 36 HYPOTONIC INTRAVENOUS FLUIDS Avoid using intravenous fluid with an osmolarity less than 150 mOsm/L Sterile water alone should never be administered intravenously Some prescribers use hypotonic saline for a patient with hypernatremia 37 T H A N K YO U 38  References ✓ Citation: CHAPTER 16 Brain, Morton DA, Foreman K, Albertine KH. The Big Picture: Gross Anatomy, Medical Course & Step 1 Review, 2nd Edition; 2018. Available at: https://accesspharmacy.mhmedical.com/content.aspx?sectionid=202 020846&bookid=2478&Resultclick=2 Accessed: June 26, 2023 Copyright © 2023 McGraw-Hill Education. All rights reserved ✓ https://www.fluidacademy.org/ ✓ hessman KH, Haney JS. Disorders of Sodium and Water Homeostasis. In: DiPiro JT,Yee GC, Haines ST, Nolin TD, Ellingrod VL, Posey L. eds. DiPiro’s Pharmacotherapy: A Pathophysiologic Approach, 12th Edition. McGraw Hill; 2023. Accessed June 26, 2023. https://accesspharmacy.mhmedical.com/content.aspx?bookid= 3097&sectionid=269666297 ✓ Arora N, Jefferson J. Fluid Management. In: Papadakis MA, McPhee SJ, Rabow MW, McQuaid KR. eds. Current Medical Diagnosis & Treatment 2023. McGraw Hill; 2023. Accessed June 26, 2023. https://accessmedicine.mhmedical.com/content.aspx?bookid= 3212&sectionid=269139891 ✓ Fluids, Electrolytes, and Nutrition Leslie A. Hamilton, Pharm.D., FCCP, FCCM, FNCS, BCPS, BCCCP University of Tennessee Health Science Center College of Pharmacy Knoxville, Tennessee 39