Chapter 40 Fluid, Electrolyte, and Acid-Base Balance Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Copyright © 2019 Wolters Kluwer • All Rights Reserved Functions of Water in the Body Transporting nutrients to cells and wastes from cells Transporting hormones, enzymes, blood platelets, and red and white blood cells Facilitating cellular metabolism and proper cellular chemical functioning Acting as a solvent for electrolytes and nonelectrolytes Helping maintain normal body temperature Facilitating digestion and promoting elimination Acting as a tissue lubricant Copyright © 2019 Wolters Kluwer • All Rights Reserved Two Compartments of Fluid in the Body Intracellular fluid (ICF): fluid within cells (70%) Extracellular fluid (ECF): fluid outside cells (30%) o Includes intravascular and interstitial fluids Copyright © 2019 Wolters Kluwer • All Rights Reserved Variations in Fluid Content Healthy person: total body water is 50% to 60% of body weight An infant has considerably more body fluid and ECF than an adult; more prone to fluid volume deficits Gender and amount of fat cells affect body water; women and obese people have less body water Copyright © 2019 Wolters Kluwer • All Rights Reserved Total Body Fluid Representing 50%–60% of Body Weight of Normal Adult Copyright © 2019 Wolters Kluwer • All Rights Reserved Electrolytes Ions o Cations: positive charge o Anions: negative charge Homeostasis: total cations equal to total anions Copyright © 2019 Wolters Kluwer • All Rights Reserved Fluid Balance Solvents: liquids that hold a substance in solution (water) Solutes: substances dissolved in a solution (electrolytes and nonelectrolytes) Copyright © 2019 Wolters Kluwer • All Rights Reserved Major Electrolytes/Chief Function Sodium: controls and regulates volume of body fluids Potassium: chief regulator of cellular enzyme activity and water content Calcium: nerve impulse, blood clotting, muscle contraction, B12 absorption Magnesium: metabolism of carbohydrates and proteins, vital actions involving enzymes Chloride: maintains osmotic pressure in blood, produces hydrochloric acid Bicarbonate: body’s primary buffer system Phosphate: involved in important chemical reactions in the body, cell division, and hereditary traits Copyright © 2019 Wolters Kluwer • All Rights Reserved Question #1 Tell whether the following statement is true or false. Molecules in the body’s chemical compounds that remain intact are called electrolytes. A. True B. False Copyright © 2019 Wolters Kluwer • All Rights Reserved Answer to Question #1 Answer: B. False Rationale: Molecules in the body’s chemical compounds that remain intact are called nonelectrolytes. Copyright © 2019 Wolters Kluwer • All Rights Reserved Transporting Body Fluids Osmosis: water passes from an area of lesser solute concentration to greater concentration until equilibrium is established Diffusion: tendency of solutes to move freely throughout a solvent (“downhill”) Active transport: requires energy for movement of substances through the cell membrane from the lesser solute concentration to the higher solute concentration Capillary filtration: passage of fluid through a permeable membrane from the area of higher to lower pressure Copyright © 2019 Wolters Kluwer • All Rights Reserved Osmolarity of a Solution Isotonic: same concentration of particles as plasma Hypertonic: greater concentration of particles than plasma Hypotonic: lesser concentration of particles than plasma Copyright © 2019 Wolters Kluwer • All Rights Reserved Filtration Colloid osmotic pressure Hydrostatic pressure Copyright © 2019 Wolters Kluwer • All Rights Reserved Source of Fluids for the Body Ingested liquids Food Byproduct of metabolism Copyright © 2019 Wolters Kluwer • All Rights Reserved Fluid Losses Kidneys: urine Intestinal tract: feces Skin: perspiration Insensible water loss Copyright © 2019 Wolters Kluwer • All Rights Reserved Fluid Intake and Losses: About Equal in Health Copyright © 2019 Wolters Kluwer • All Rights Reserved Primary Organs of Homeostasis #1 Kidneys normally filter 170 L of plasma and excrete 15 L of urine. The cardiovascular system pumps and carries nutrients and water in body. Lungs regulate oxygen and carbon dioxide levels of the blood. Adrenal glands help the body conserve sodium, save chloride and water, and excrete potassium. The pituitary gland stores and releases ADH. Copyright © 2019 Wolters Kluwer • All Rights Reserved Primary Organs of Homeostasis #2 The thyroid gland increases the blood flow in the body and increases renal circulation. The nervous system inhibits and stimulates mechanisms influencing fluid balance. Parathyroid glands regulate the level of calcium in ECF. The GI tract absorbs water and nutrients that enter the body through this route. Copyright © 2019 Wolters Kluwer • All Rights Reserved Question #2 Tell whether the following statement is true or false. A hypertonic solution has a greater osmolarity, causing water to move out of the cells and to be drawn into the intravascular compartment, causing the cell to shrink. A. True B. False Copyright © 2019 Wolters Kluwer • All Rights Reserved Answer to Question #2 Answer: A. True Rationale: A hypertonic solution has a greater osmolarity, causing water to move out of the cells and to be drawn into the intravascular compartment, causing the cell to shrink. Copyright © 2019 Wolters Kluwer • All Rights Reserved Acid–Base Balance (pH) Acid: substance containing hydrogen ions that can be liberated or released Base: substance that can trap hydrogen ions Copyright © 2019 Wolters Kluwer • All Rights Reserved Major Homeostatic Regulators of Hydrogen Ions Buffer systems o Carbonic acid–sodium bicarbonate o Phosphate o Protein Respiratory mechanisms Renal mechanisms Copyright © 2019 Wolters Kluwer • All Rights Reserved Question #3 Which one of the following chemical buffer systems is the most important buffer system of the body in that it buffers as much as 90% of the hydrogen of ECF? A. Phosphate buffer system B. Protein buffer system C. Carbonic acid–sodium bicarbonate buffer system D. Hydrogen buffer system Copyright © 2019 Wolters Kluwer • All Rights Reserved Answer to Question #3 Answer: C. Carbonic acid–sodium bicarbonate buffer system Rationale: The carbonic acid–sodium bicarbonate buffer is the most important buffer system of the body, buffering as much as 90% of the hydrogen of ECF. Buffers attempt to bring a body fluid as close as possible to the pH of normal body fluid (7.35–7.45). Copyright © 2019 Wolters Kluwer • All Rights Reserved Fluid Imbalances Involve either volume or distribution of water or electrolytes Hypovolemia: deficiency in amount of water and electrolytes in ECF with near-normal water/electrolyte proportions Dehydration: decreased volume of water and electrolyte change Third-space fluid shift: distributional shift of body fluids into potential body spaces Copyright © 2019 Wolters Kluwer • All Rights Reserved Fluid Volume Excess Hypervolemia: excessive retention of water and sodium in ECF Overhydration: above-normal amounts of water in extracellular spaces Edema: excessive ECF accumulates in tissue spaces Interstitial-to-plasma shift: movement of fluid from space surrounding cells to blood Copyright © 2019 Wolters Kluwer • All Rights Reserved Electrolyte Imbalances Hyponatremia and hypernatremia Hypokalemia and hyperkalemia Hypocalcemia and hypercalcemia Hypomagnesemia and hypermagnesemia Hypophosphatemia and hyperphosphatemia Hypochloremia and hyperchloremia Copyright © 2019 Wolters Kluwer • All Rights Reserved Question #4 Which one of the following electrolyte imbalances occurs due to a sodium deficit in ECF caused by a loss of sodium or gain of water? A. Hyponatremia B. Hypernatremia C. Hypokalemia D. Hyperkalemia Copyright © 2019 Wolters Kluwer • All Rights Reserved Answer to Question #4 Answer: A. Hyponatremia Rationale: Hyponatremia refers to a sodium deficit in ECF caused by a loss of sodium or gain of water. Hypernatremia refers to a surplus of sodium in ECF. Hypokalemia refers to a potassium deficit in ECF. Hyperkalemia refers to an excess of potassium in ECF. Copyright © 2019 Wolters Kluwer • All Rights Reserved Acid–Base Imbalances Occur when carbonic acid or bicarbonate levels become disproportionate o Respiratory acidosis: primary excess of carbonic acid in ECF o Respiratory alkalosis: primary deficit of carbonic acid in ECF o Metabolic acidosis: proportionate deficit of bicarbonate in ECF o Metabolic alkalosis: primary excess of bicarbonate in ECF Copyright © 2019 Wolters Kluwer • All Rights Reserved Nursing Assessments Identify patients at risk for imbalances. Determine that a specific imbalance is present and its severity, etiology, and characteristics. Determine the care plan, nursing diagnoses or collaborative problems. Identify specific outcomes and associated interventions. Determine effectiveness of the care plan. Copyright © 2019 Wolters Kluwer • All Rights Reserved Parameters of Assessment Nursing history and physical assessment Fluid intake and output Daily weights Laboratory studies Copyright © 2019 Wolters Kluwer • All Rights Reserved Lab Studies to Assess for Imbalances Complete blood count Serum electrolytes, blood urea nitrogen, and creatinine levels Urine pH and specific gravity Arterial blood gases Copyright © 2019 Wolters Kluwer • All Rights Reserved Risk Factors for Imbalances Pathophysiology underlying acute and chronic illnesses Abnormal losses of body fluids Burns Trauma Surgery Therapies that disrupt fluid and electrolyte balance Copyright © 2019 Wolters Kluwer • All Rights Reserved Nursing Diagnoses Related to Imbalances Excess fluid volume Deficient fluid volume Risk for deficient fluid volume Copyright © 2019 Wolters Kluwer • All Rights Reserved Expected Outcomes Maintain approximate fluid intake and output balance (2,500-mL intake and output over 3 days). Maintain urine specific gravity within normal range (1,010–1,025). Practice self-care behaviors to promote balance. Copyright © 2019 Wolters Kluwer • All Rights Reserved Implementing Dietary modifications Modifications of fluid intake Medication administration IV therapy Blood and blood products replacement TPN Allaying patient anxiety as needed Appropriate patient and family teaching Copyright © 2019 Wolters Kluwer • All Rights Reserved Administering Medications Mineral–electrolyte preparations Diuretics Intravenous therapy Copyright © 2019 Wolters Kluwer • All Rights Reserved Intravenous Therapy PICCs Nontunneled percutaneous central venous catheters Tunneled central venous catheters Implanted ports Copyright © 2019 Wolters Kluwer • All Rights Reserved Question #5 Tell whether the following statement is true or false. Central venous access devices provide access for a variety of IV fluids, medications, blood products, and TPN solutions and allow a means for hemodynamic monitoring and blood sampling. A. True B. False Copyright © 2019 Wolters Kluwer • All Rights Reserved Answer to Question #5 Answer: A. True Rationale: Central venous access devices provide access for a variety of IV fluids, medications, blood products, and TPN solutions and allow a means for hemodynamic monitoring and blood sampling. Copyright © 2019 Wolters Kluwer • All Rights Reserved Vein Site Selection Accessibility of a vein Condition of vein Type of fluid to be infused Anticipated duration of infusion Copyright © 2019 Wolters Kluwer • All Rights Reserved Placement of Peripherally Inserted Central Catheter (PICC) Copyright © 2019 Wolters Kluwer • All Rights Reserved Administering Blood and Blood Products Typing and cross-matching A, B, AB, and O type blood Rh factor Selecting blood donors Initiating transfusion Transfusion reactions Copyright © 2019 Wolters Kluwer • All Rights Reserved
