Chapter 21 Fluid & Electrolyte Balance PDF

Fluid & Electrolyte Balance Chapter 21  Learning Objectives Lesson 21.1: Fluid and Electrolyte Balance (1 of 2) 1. Describe how body fluid volumes relate to age, gender, and body weight. 2. List, describe, and compare the body fluid comp...

Fluid & Electrolyte Balance Chapter 21  Learning Objectives Lesson 21.1: Fluid and Electrolyte Balance (1 of 2) 1. Describe how body fluid volumes relate to age, gender, and body weight. 2. List, describe, and compare the body fluid compartments and their subdivisions. 3. Discuss the avenues by which water enters and leaves the body. 4. Explain the mechanisms used by the body to maintain fluid balance. 5. Discuss the forces that move fluids into and out of the blood.  Learning Objectives Lesson 21.1: Fluid and Electrolyte Balance (2 of 2) 6. Describe examples of common fluid imbalances. 7. Discuss the nature and importance of electrolytes in body fluids. 8. Describe examples of common electrolyte imbalances.  Body Fluid Volumes  Water is the most abundant body compound  References to “average” body water volume in reference tables are based on a healthy, nonobese 70-kg male  Volume averages 40 L in a 70-kg male Plasma (3 L) Interstitial fluid (12 L) Intracellular fluid (25 L)  Water is 80% of body weight in newborn infants; 60% in adult males; 50% in adult females Relative Volumes of Three Body Fluids Water in the Body  Variation in Total Body Water  Variation in total body water is related to:  Total body weight of individual  Fat content of body: The more fat in the body, the less the total water content per kilogram of body weight (adipose tissue is low in water content)  Gender: Female body has about 10% less than male body  Age: In a newborn infant, water may account for 80% of total body weight. In the elderly, water per kilogram of weight decreases (muscle tissue—high in water—  Body Fluid Compartments  Extracellular fluid (ECF): Called internal environment of body; surrounds cells and transports substances to and from them  Plasma: Liquid part of whole blood  Interstitial fluid (IF): Surrounds the cells  Transcellular: Lymph; joint fluids; cerebrospinal fluid; eye humors  Intracellular Fluid (ICF)  Largest fluid compartment  Located inside cells  Serves as solvent to facilitate intracellular chemical reactions  Sources of Fluid Intake and Output  Sources of fluid intake  Liquids we drink  Water in food we eat  Metabolic water (from cellular respiration)  Sources of fluid output  Water vapor (during respiration)  Sweating (from skin)  Urine (from kidney)  Water lost in the feces Fluid Balance  Regulation of Fluid Output  Organs responsible for fluid output: Lungs, skin, kidneys, and large intestine  Fluid output, mainly urine volume, adjusts to fluid intake  Antidiuretic hormone (ADH) released from posterior pituitary gland when ECF volume is low  ADH and aldosterone from adrenal cortex increase kidney tubule reabsorption of sodium and water from tubular urine into blood; tends to increase ECF (and total body fluid) by decreasing urine volume  Three main factors affect plasma, IF, and ICF Aldosterone Mechanism  Regulation of Fluid Intake  Sensory receptors detect change in volume and concentration of ECF and send signals to the hypothalamus  Signals from hypothalamus cause feeling of thirst, which triggers drinking of fluids to restore balance  If adequate fluids are not taken in, the body will compensate by decreasing saliva production and the production of other fluids, but water is still lost through sweating and expiration Homeostasis of the Total Volume of Body Water  Capillary Blood Pressure and Blood Proteins  Increased capillary blood pressure transfers fluid from blood to IF: A fluid shift  Blood plasma protein concentration contributes to osmotic pressure, thus attracting water and holding it in the plasma  Fluid Imbalances  Dehydration: Total volume of body fluids smaller than normal  IF volume shrinks first, and if treatment is not given, ICF volume and plasma volume decrease  Dehydration occurs when fluid output exceeds intake for an extended period Dehydration Testing for Dehydration From Fritz S: Mosby’s fundamentals of therapeutic massage, ed 5, St Louis, 2013, Mosby.  Overhydration  Overhydration: Total volume of body fluids larger than normal  Fluid intake exceeds output  Excess volume burdens pumping action of heart  Water intoxication: Possibly life- threatening neurological impairment caused by severe overhydration and accompanying electrolyte imbalance  Importance of Electrolytes in Body Fluids (1 of 2)  Nonelectrolytes: Organic substances that do not break up or dissociate when placed in water solution (e.g., glucose)  Electrolytes: Compounds that break up or dissociate in water solution into separate particles called ions (e.g., ordinary table salt or sodium chloride)  Importance of Electrolytes in Body Fluids (2 of 2)  Electrolyte composition of body fluids  Edema: Swelling caused by high IF volume; pitting edema occurs when depressions in skin do not rapidly refill  Aldosterone mechanism restores normal ECF volume  Sodium-containing internal secretions  Ions  The dissociated particles of an electrolyte that carry an electrical charge  Cations are positively charged ions (e.g., potassium [K+] and sodium [Na+])  Anions are negatively charged particles (ions) (e.g., chloride [Cl−] and bicarbonate [HCO3−], anionic proteins) Electrolytes Found in Fluid Compartments of the Body  Pitting Edema From Bloom A, Ireland J: Color atlas of diabetes, ed 2, St Louis, 1992, Mosby. Sodium-Containing Internal Secretions  Electrolyte Imbalances  Any disruption in a homeostatic mechanism that controls the level or normal chemical activity of a particular electrolyte in any body fluid  Related to “intake” and “output” of electrolytes and also absorption and distribution of electrolytes in body fluids and availability for use by body cells  Sodium Imbalance  Hypernatremia: Blood sodium more than 145 mEq/L  Characterized by relative deficit of water to salt in extracellular fluid (ECF)  Causes include overuse of salt tablets; dehydration; and prolonged diarrhea  Hyponatremia  Blood sodium less than 136 mEq/L  Results when there is relatively too much water in the ECF for the amount of sodium present  Causes include excessive secretion of antidiuretic hormone; massive infusion of sodium-free IV solution; burns; and prolonged use of certain diuretics  Symptoms of both hypernatremia and hyponatremia are related to central nervous system (CNS) malfunction and include headache, confusion, seizures, and coma  Potassium Imbalance  Hyperkalemia: Blood potassium more than 5.1 mEq/L  Causes include increased intake; shift of potassium from ICF to blood caused by tissue trauma and burns; renal failure  Clinical signs of hyperkalemia are related to muscle malfunction and include skeletal muscle weakness, paralysis, and cardiac arrest  Hypokalemia  Blood potassium less than 3.5 mEq/L  Causes include fasting; diets low in potassium; abuse of laxatives and certain diuretics; diarrhea; vomiting; gastric suction  Clinical signs include skeletal muscle and cardiac problems; smooth muscle weakness causing abdominal distention; and slow rate of passage of GI contents  Calcium Imbalance  Hypercalcemia: Blood calcium levels more than 10.5 mg/dL  Caused by excessive input; increased absorption; shifts of calcium from bone to ECF; Paget disease and other bone tumors; hyperparathyroidism  Clinical signs related to decreased neuromuscular activity: Fatigue; muscle weakness; diminished reflexes; cardiac problems  Hypocalcemia  Blood calcium levels less than 8.4 mg/dL  Caused by dietary deficiency; decreased absorption or availability; increased excretion; pancreatitis; hypoparathyroidism; rickets and osteomalacia; and renal insufficiency  Clinical signs related to increased neuromuscular irritability: Cramping, muscle twitching; hyperactive reflexes; and abnormal cardiac rhythms Questions?