Fluid, Electrolyte, and Acid-Base Balance Notes PDF

Chapter 9, Fluid, Electrolyte, and Acid-Base Balance Textbook Chapter: _____ A. Body Fluid (or Body Water plus dissolved substances) averages close to 60% of body composition for males and a little over 50% of body composition for females. 1. Average infant is 70-75% water, and...

Chapter 9, Fluid, Electrolyte, and Acid-Base Balance Textbook Chapter: _____ A. Body Fluid (or Body Water plus dissolved substances) averages close to 60% of body composition for males and a little over 50% of body composition for females. 1. Average infant is 70-75% water, and as we age, the percentage drops. 2. Lean people have a greater percentage of water to body ratio due to fat being mostly water free. 3. Body fluid is divided into 2 locations: extracellular fluid (ECF) and intracellular fluid (ICF). B. Extracellular Fluid (ECF): 1. accounts for approximately 1/3 of the body fluids. 2. locations - (outside of the body's cells): a. interstitial fluids (majority). b. blood plasma c. some others: CSF (cerebrospinal fluid), lymph, serous liquids, synovial fluid, G-I fluids, fluids inside the eyeball, etc... - 3. major ions involved: chloride (CL ), sodium (Na+), - bicarbonate (HCO3 ). C. Intracellular Fluid (ICF): 1. accounts for approximately 2/3 of the body fluids. 2. location: inside the body's cells. 3- 3. major ions involved: phosphate (PO4 ), magnesium (Mg2+), potassium (K+), proteins (negatively charged ones). D. The cell membrane works with such mechanisms as selective permeability, osmosis, and active transport to control the movement of ions between ICF and ECF. Remember, changes in solutes effects water movement's distribution between the body's compartments, and water movement occurs passively due to the concentration of solutes (osmotic gradients). E. Water 1. Water is the largest component of the human body. 2. At birth, a newborn is usually over 70% water. 3. If one has a great gain in fat (obesity), the percentage of water decreases. 4. Daily water intake: a. two-thirds from liquid ingestion; one-third from ingested food (including the chemical breakdown of food products). b. average daily intake: 2,500 ml. daily. 9−1  c. the amount varies with metabolism, environment, and the health of the individual. 5. Daily water loss (an average of approximately 2500 ml. daily; average lost should equal the average taken in): a. from urine: 1,200 - 1,800 ml. daily. b. from skin (includes sweating ((sweat glands)) and insensible perspiration): 450 - 500 ml. daily. c. from respiration: 300 - 400 ml. daily. d. from feces: 100- 150 ml. daily. e. from mucus and tears: small amount. f. the amount varies with metabolism, environment, and the health of the individual. 6. Insensible water loss: (750 - 900 ml.) a. water loss via evaporation from respiratory tract. b. water loss via diffusion through the skin. 7. Some internal secretions (most of which will be reabsorbed): a. saliva: approximately 1,500 ml./day. b. gastric: 1,500 - 2,500 ml./day. c. bile: 500 - 1,000 ml./day. d. pancreas: 700 - 1,000 ml./day. e. intestines: 2,000 - 3,000 ml./day. F. Nonelectrolytes vs. electrolytes: 1. Nonelectrolytes - compounds with covalent bonds (ie. - the atoms of the molecules that compose these compounds do not form ions when dissolved); include most of the organic compounds such as glucose. 9-2  2. Electrolytes - also called ions; compounds that have at least one ionic bond; they dissociate in specific liquids into cations (ions with positive charges, ie. sodium) and anions (ions with negative charges, ie. chloride); examples of electrolytes are acids, bases, and salts. a. electrolytes are generally inorganic compounds; however, some are organic (ie. - citric acid and lactic acid). b. electrolytes carry an electrical current. c. electrolytes control water movement (osmosis) from one area of the body to another. d. electrolytes help to keep the acid-base (pH) balance of cells. e. electrolytes help to keep the body electrically and chemically balanced. G. Edema - excess fluid in the body's tissue. 1. extracellular edema a. characterized by an excess extracellular fluid accumulation within the interstitial spaces. b. usually due to the following (although other factors can also contribute): 1.) capillary pressure increasing or capillaries becoming more permeable. 2.) decrease of lymph return to bloodstream. 3.) plasma protein level decreases. 4.) kidney problems that result in retention of water or salt. 5.) cardiovascular problem (especially heart problems). 2. intracellular edema: a. characterized by an excess fluid accumulation within the cell. b. examples: 1.) cells failure to remove specific ions (ex. → Na+ resulting in fluid (water) accumulation. 2.) metabolic problems of the body resulting in imbalance between electrolytes and fluids within the cell. 3.) circulatory (cardiovascular) problems resulting in imbalance between electrolytes and fluids within the cell. 9-3 H. Major ions involved in extracellular fluid (ECF): 1. chloride (CL-) a. the major extracellular anion. b. balances osmotic pressure between body compartments. c. part of stomach acid (HCL). d. passively follows sodium. e. exits the body primarily via urine and sweat. f. hormone regulation: aldosterone is indirectly involved. 2. sodium (Na+) a. the major extracellular cation. b. necessary for action potential conduction (in muscle and nerve tissues). c. major role in fluid and electrolyte balance (and osmosis). d. exits the body via urine, sweat, and feces. e. hormone regulation: several, some of which are ADH and aldosterone. I. Major ions involved in intracellular fluid (ICF): 1. phosphate a. most common forms in the body: H2PO4-; HPO42-; 3- PO4. b. anion; most is present in the adult as calcium phosphate salts in bone; another form is ATP. c. involved in bone and teeth structure, and in buffering. d. note: a lot of carbonate drinks contain phosphate; consumption of large amounts of these drinks can cause excess phosphate in the blood. e. hormone regulation: parathormone and calcitonin. 2. magnesium (Mg2+) a. cation; mainly in bone and intracellular fluid. b. some major functions: cofactor for enzymes used in protein and carbohydrate metabolism; also nervous system transmission, heart functioning, and involved in the sodium pump. c. exits the body primarily through urine. d. hormone regulation: aldosterone. 9-4  3. potassium (K+) a. most abundant intracellular cation. b. some major functions: neuromuscular and cardiac functions, fluid volume, help regulate pH by exchanging with H+. c. exits the body primarily through urine. d. hormone regulation: mineralocorticoids. J. Acidosis and Alkalosis 1. blood pH is 7.35 - 7.45: a. acidosis: blood pH lower than 7.35. b. alkalosis: blood pH greater than 7.45. 2. clinically, the major effect of acidosis is the depression of the central nervous system (causes disorientation and can cause coma). Two types of acidosis: + a. metabolic acidosis (H is increased, thus pH is decreased): 1.) can be due to acid accumulation or loss of bases. 2.) some symptoms: increased ventilation and fatigue. b. respiratory acidosis (CO2 increases, thus pH decreases): 1.) due to factors that cause an increase in CO2, accompanied by an increase in the respiratory acid (carbonic acid). 2.) some symptoms: ventilation is decreased or nonexistent, weakness. 3. clinically, the major effect of alkalosis is that the nervous system becomes overexcitable. Two types of alkalosis: + a. metabolic alkalosis (H is decreased, thus pH is increased): + 1.) due to excessive H loss or gain in base or bases. 2.) some symptoms: breathing is depressed, confusion, and muscles can go into a state of tetany (tonic spasm). 9-5  b. respiratory alkalosis (decreased CO2, thus pH is increased): 1.) due to excessive loss of CO2, thus loss of carbonic acid. 2.) some symptoms: increased depth and rate of breathing, lightheadedness, and numbness. K. The major buffer systems for the body's fluids: bicarbonate, phosphate, and protein buffer systems. 1. bicarbonate buffer system: a. based on carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3). examples: 1.) HCL + NaHCO3 --> H2CO3 + NaCL (strong acid) (weak acid) 2.) H2CO3 --> H2O + CO2 3.) NaOH + H2CO3 --> NaHCO3 + H20 (strong base) (weak base) b. a regulator of blood pH via respiratory and urinary system. c. kidneys reabsorb HCO3- excrete H+ to help maintain pH. 2. phosphate buffer system (primarily intracellular): a. based on H2PO4- (NaH2PO4) and HPO42- (Na2HPO4) examples: 1.) HCL + NaH2PO4 --> NaH2PO4 + NaCL 2.) NaOH + NaH2PO4 --> Na2HPO4 + H2O b. a regulator of pH in RBCs and the kidney's fluids. 9-6  3. protein buffer system (in pH of blood plasma and in cells): * based on amino acid chemistry a. acid component: COOH. b. base component is the amino group: NH2. c. examples: 1.) -COOH... --> COO + H+ + * here it acts as an acid by releasing H (condition for this to happen: when pH rises and needs to be buffered). 2.) -NH2 + H+... --> NH3+ * here it acts as a base by combing with H+ (condition for this to happen: when the pH falls and needs to be buffered). 4. two important amino acid buffers are: histidine and cysteine. L. Hormone regulation of fluid and electrolyte balance: 1. Antidiuretic Hormone (ADH). a. origin: hypothalamus. b. secreted in reference to ECF osmolarity. c. Results: 1.) water conservation in the kidney. 2.) stimulate's brain "thirst center" to stimulate drinking of fluids. 2. Aldosterone a. origin: adrenal cortex. b. stimulated (via renin - angiotensin system in kidney) by such causes as a decrease in blood pressure or a decrease in plasma volume (there are other causes). c. helps to determine sodium absorption by the kidney (its secretion causes more sodium to be absorbed by the kidney); water follows this sodium and results in water retention. 9-7 3. Atrial Natriuretic Peptide (ANP) a. origin: cardiac muscle fibers. b. stimulated by atrial wall stretching due to blood volume increase or an increase in blood pressure. c. Results: 1.) both ADH and aldosterone to be blocked. 2.) decreases the desire to drink fluids. (decreases thirst) 9-8