Chapter 13 - Solutions, Body Fluids, and Electrolytes PDF

Chapter 13 - Solutions, Body Fluids, and Electrolytes Kacmarek et al.: Egan’s Fundamentals of Respiratory Care, 11th Edition MULTIPLE CHOICE 1. What is a uniform distribution of large molecules that attract and hold water? a. Colloid b. Mixture c. Solution d. Suspension ANS: A Colloids (sometimes called dispersions or gels) consist of large molecules that attract and hold water. DIF: Recall REF: pp. 270-271 OBJ: 1 2. The combination of red blood cells in plasma is a good example of what? a. Colloid b. Mixture c. Solution d. Suspension ANS: D Red blood cells in plasma are an example of a suspension. DIF: Application REF: p. 271 OBJ: 1 3. What is a stable mixture of two or more evenly dispersed substances? a. Colloid b. Mixture c. Solution d. Suspension ANS: C A solution is a stable mixture of two or more substances in a single phase. One substance is evenly dispersed throughout the other. DIF: Application REF: p. 270 OBJ: 1 4. The ease with which a gas dissolves into a solvent is at least partially determined by which of the following? a. Gas conductivity b. Gas temperature c. Level of 2,3-DPG d. Solvent conductivity ANS: B The ease with which a solute dissolves in a solvent is its solubility, which is influenced by five factors: 1. Nature of the solute. The ease with which substances go into a solution in a given solvent depends on the forces of the solute-solute molecules and varies widely. 2. Nature of the solvent. A solvent’s ability to dissolve a solute depends on the bonds of the solvent-solvent molecules, and also varies widely. 3. Temperature. Solubility of most solids increases with increased temperature. However, the solubility of gases varies inversely with temperature. 4. Pressure. The solubility of solids and liquids is not greatly affected by pressure. The solubility of gases in liquids, however, varies directly with pressure. 5. Concentration. The concentration of a solute or available solvent will have an effect of how much of the substance goes into solution. DIF: Application REF: p. 271 OBJ: 2 5. Which of the following is false regarding solubility? a. Gas solubility varies directly with pressure. b. Gas solubility varies directly with temperature. c. Solvents vary in their ability to dissolve substances. d. The solubility of solids increases with temperature. ANS: A The ease with which a solute dissolves in a solvent is its solubility, which is influenced by five factors: 1. Nature of the solute. The ease with which substances go into a solution in a given solvent depends on the forces of the solute-solute molecules and varies widely. 2. Nature of the solvent. A solvent’s ability to dissolve a solute depends on the bonds of the solvent-solvent molecules, and also varies widely. 3. Temperature. Solubility of most solids increases with increased temperature. However, the solubility of gases varies inversely with temperature. 4. Pressure. The solubility of solids and liquids is not greatly affected by pressure. The solubility of gases in liquids, however, varies directly with pressure. 5. Concentration. The concentration of a solute or available solvent will have an effect of how much of the substance goes into solution. DIF: Application REF: p. 271 OBJ: 2 6. Gas transport in the body is most affected by changes in which of the following variables? a. Ambient pressure b. Inspired gas temperature c. Oxygen’s solubility coefficient d. Water vapor pressure of inspired gases ANS: A The partial pressure of the dissolved gas is the product of its coefficient of solubility and the partial pressure of the gas to which the liquid is exposed. Oxygen and carbon dioxide transport can change significantly with changes in body temperature or the pressure to which the body is exposed. DIF: Application REF: p. 271 OBJ: 2 7. A solution holding the maximum amount of solute in a given volume at a constant temperature is said to be what? a. Hypertonic b. Hypotonic c. Saturated d. Supersaturated ANS: C A saturated solution has the maximal amount of solute that can be held in a given volume of a solvent at a constant temperature. DIF: Application REF: p. 271 OBJ: 2 8. Which of the following describes the most important physiological characteristic of solutions? a. Their ability to exert pressure b. Their ability to redistribute in blood c. Their ability to vary concentration inversely with tonicity d. Their ability to vary pressure inversely with temperature ANS: A The most important physiologic characteristic of solutions is their ability to exert pressure. DIF: Application REF: p. 272 OBJ: 1 9. What is the attractive force of solute particles in a concentrated solution? a. Diffusion pressure b. Gas pressure c. Hydrostatic pressure d. Osmotic pressure ANS: D Osmotic pressure is the force produced by solvent particles under certain conditions. If a solution is placed on one side of a semipermeable membrane and pure solvent on the other, solvent molecules will move through the membrane into the solution. The force driving solvent molecules through the membrane is osmotic pressure (Figure 12-2, A). DIF: Recall REF: p. 272 OBJ: 3 10. What is the effect of osmotic pressure on solutions of different solute concentrations, separated by a semipermeable membrane? a. Causes a net loss of fluid. b. Equal distribution of solvent. c. Has no effect in this situation. d. Redistribution of the solute. ANS: B Osmotic pressure tries to distribute solvent molecules so that the same concentration exists on both sides of the membrane. DIF: Application REF: p. 272 OBJ: 3 11. If a 60% solution (A) were exposed to a 10% solution (B) across a semipermeable membrane, what would be the strength of each solution following equilibrium? a. Solution A 10%/solution B 60% b. Solution A 35%/solution B 35% c. Solution A 50%/solution B 20% d. Solution A 60%/solution B 10% ANS: B Osmotic pressure can also be visualized as an attractive force of solute particles in a concentrated solution. If 100 ml of a 50% solution is placed on one side of a membrane and 100 ml of a 30% solution is placed on the other side, solvent molecules will move from the dilute to the concentrated side (Figure 13-2, D and E). The particles in the concentrated solution attract solvent molecules from the dilute solution until equilibrium occurs. Equilibrium exists when the concentrations (i.e., ratio of solute to solvent) in both compartments are equal (40% in Figure 13-2). DIF: Application REF: p. 271 OBJ: 3 12. Which of the following is true regarding osmotic pressure? a. Osmotic pressure depends on the number of particles in solution. b. Osmotic pressure varies inversely with temperature. c. Osmotic pressure is highest in dilute solutions. d. Osmotic pressure varies inversely with tonicity. ANS: A Osmotic pressure depends on the number of particles in solution but not on their charge or identity. A 2% solution has twice the osmotic pressure of a 1% solution under similar pressures. For a given amount of solute, osmotic pressure is inversely proportional to the volume of solvent. Osmotic pressure varies directly with temperature, increasing by 1/273 for each 1° C. DIF: Application REF: p. 272 OBJ: 3 13. Which of the following is an isotonic solution? a. 0.09% NaCl b. 0.90% NaCl c. 9.00% NaCl d. 19.0% NaCl ANS: B Average body cellular fluid has a tonicity equal to a 0.9% solution of sodium chloride (NaCl; sometimes referred to as physiologic saline). Solutions with similar tonicity are called isotonic. DIF: Recall REF: p. 272 OBJ: 3 14. A 3% NaCl solution is referred to as: a. hypertonic. b. hypotonic. c. isotonic. d. normotonic. ANS: B Those solutions with more tonicity are hypertonic, and those solutions with less tonicity are hypotonic. DIF: Application REF: p. 272 OBJ: 3 15. If your objective were to draw water out of cells or tissues, you would expose them to what type of solution? a. Hypertonic b. Hypotonic c. Isotonic d. Normotonic ANS: A Hypertonic solutions draw water out of cells. DIF: Application REF: p. 272 OBJ: 3 16. What is the normal ratio of HCO3– to carbonic acid in healthy individuals? a. 1:1 b. 2:1 c. 10:1 d. 20:1 ANS: D The ratio of HCO3– to carbonic acid in healthy individuals is maintained near 20:1; this results in a pH of close to 7.40. HCO3– stores are evenly divided between intracellular and extracellular compartments. DIF: Recall REF: p. 281 OBJ: 4 17. Positive ions are referred to as: a. anions. b. cations. c. covalents. d. electrolytes. ANS: B If an electrode is placed in such a solution, positive ions migrate to the negative pole of the electrode. These ions are called cations. DIF: Recall REF: p. 270 OBJ: 5 18. In which of the following solutions do the molecules of solute remain intact? a. Electrolytic b. Electrovalent c. Nonpolar covalent d. Polar covalent ANS: C In nonpolar covalent solutions, molecules of solute remain intact and do not carry electrical charges; these solutions are referred to as nonelectrolytes. DIF: Application REF: p. 270 OBJ: 5 19. How is the gram-equivalent (gEq) weight of a substance computed? a. Dividing its gram atomic weight by its valence b. Dividing its valence by its gram atomic weight c. Multiplying its atomic number times its atomic weight d. Multiplying its gram atomic weight times its valence ANS: A Gram equivalent weight values. A gEq of a substance is calculated as its gram atomic (formula) weight divided by its valence. The valence signs (+ or –) are disregarded. DIF: Analysis REF: p. 273 OBJ: 1 20. What is the gEq weight of an acid? a. Amount of the acid containing 1 mol of replaceable H+ ions. b. Amount of the acid containing 1 mol of replaceable OH ions. c. Gram atomic weight of the acid times its valence. d. Milligrams of acid per deciliter (dl) of normal solution. ANS: A The gram equivalent weight of an acid may be calculated by dividing its gram formula weight by the number of hydrogen atoms in its formula, as shown in the following reaction: The single H+ of hydrochloric acid (HCl) is replaced by Na+. One mole of HCl has 1 mol of replaceable hydrogen. By definition, the gEq of HCl must be the same as its gram formula weight, or 36.5 g. DIF: Application REF: p. 273 OBJ: 1 21. A serum value of 140 mEq/L of Na is equivalent to how many mg/dl? a. 14 mg/dl b. 70 mg/dl c. 280 mg/dl d. 322 mg/dl ANS: D For example, to convert a serum Na+ value of 322 mg/dl to mEq/L DIF: Analysis REF: p. 273 OBJ: 1 22. In which of the following types of solutions is the relationship of solute to solvent expressed as a proportion? a. Normal b. Percent c. Ratio d. Weight/volume ANS: C Ratio solution. The amount of solute to solvent is expressed as a proportion. DIF: Application REF: p. 274 OBJ: 4 23. You prepare a solution by dissolving 5 g of glucose in 100 ml of solution. What type of solution are you making? a. Normal b. Percent c. Ratio d. Weight/volume ANS: D It is defined as weight of solute per volume of solution. This method is sometimes erroneously described as a percent solution. W/V solutions are commonly expressed in grams of solute per 100 ml of solution. For example, 5 g of glucose dissolved in 100 ml of solution is properly called a 5% solution. DIF: Application REF: pp. 274-275 OBJ: 4 24. You prepare a solution by combining 5 g of glucose with 95 g of water. What type of solution are you making? a. Normal b. Percent c. Ratio d. Weight/volume ANS: B Percent solution. A percent solution is weight of solute per weight of solution. Five grams of glucose dissolved in 95 g of water is a true percent solution. The glucose is 5% of the total solution weight of 100 g. DIF: Application REF: pp. 274-275 OBJ: 4 25. What type of solution could have 1 mol of solute per liter of solution? a. Molal b. Molar c. Normal d. Weight/volume ANS: B Molar solution. A molar solution has 1 mol of solute per liter of solution, or 1 mmol/ml of solution. Solute is measured into a container and solvent is added to produce the solution volume desired. DIF: Application REF: pp. 274-275 OBJ: 1 26. What type of solution could have 1 gEq of solute per liter of solution? a. Molal b. Molar c. Normal d. Weight/volume ANS: C Normal solution. A normal solution has 1 gEq of solute per liter of solution, or 1 mEq/ml of solution. DIF: Application REF: pp. 274-275 OBJ: 1 27. You add 50 ml of water to 150 ml of a 6% solution. What is the new concentration? a. 3.0% b. 4.5% c. 7.5% d. 12.0% ANS: B If 50 ml of water is added to 150 ml of a 6% (0.03) solution, the new concentration is calculated by rearranging the dilution equation to find C2. DIF: Analysis REF: pp. 274-275 OBJ: 4 28. What is the characteristic of an acid? a. Absorbs H+ ions. b. Accepts a proton. c. Is a proton donor. d. Produces OH ions. ANS: C Another definition of an acid is that of Brönsted-Lowry, in which an acid is any compound that is a proton (H+) donor. DIF: Recall REF: p. 275 OBJ: 5 29. Identify the definition for a base substance. a. Compound that will donate a H+ ion b. Any compound that will accept a proton c. Only substances that contain a hydroxyl group d. Substances that contain Na+ ions ANS: B The Brönsted-Lowry definition of a base is any compound that accepts a proton. DIF: Recall REF: p. 275 OBJ: 5 30. Which of following are considered nonhydroxide bases? 1. Ammonia 2. Carbonates 3. Certain proteins 4. Ammonium a. 2 and 3 only b. 1, 2, and 3 only c. 1 and 4 only d. 1, 2, 3, and 4 ANS: B Nonhydroxide bases. Ammonia and carbonates are good examples of nonhydroxide bases. Proteins, with their amino groups, also can serve as nonhydroxide bases. DIF: Recall REF: pp. 275-276 OBJ: 5 31. Where does ammonia play its most important role as a base buffer? a. Kidney b. Liver c. Lung d. Vasculature ANS: A Ammonia plays an important role in renal excretion of acid. DIF: Recall REF: p. 276 OBJ: 5 32. Which of the following is a facet of blood proteins? a. Blood proteins are composed of amino acids held together by fatty acids. b. Deoxygenated hemoglobin (Hb) is unable to accept H+ ions. c. In an alkaline environment, blood proteins can act as bases. d. The imidazole group on amino acids is the key binding site for other amino acids. ANS: C Protein bases. Proteins are composed of amino acids bound together by peptide links. Physiologic reactions in the body occur in a mildly alkaline environment. This allows proteins to act as H+ receptors, or bases. Cellular and blood proteins acting as bases are transcribed as prot. The imidazole group of the amino acid histidine is an example of an H+ acceptor on a protein molecule (Figure 12-4). The ability of proteins to accept hydrogen ions limits H+ activity in solution, which is called buffering. The ability of hemoglobin to accept (i.e., buffer) H+ ions depends on its oxygenation state. Deoxygenated (reduced) hemoglobin is a stronger base (i.e., a better H+ acceptor) than oxygenated hemoglobin. DIF: Application REF: p. 276 OBJ: 6 33. Pick the correct statement as it relates to hemoglobin and acid-base buffering. a. Deoxygenated hemoglobin acts as an acid at the tissue level. b. Deoxygenated hemoglobin is a fairly strong base. c. Hemoglobin contributes more H+ in the face of increased histidine. d. In an alkaline environment, hemoglobin becomes an ineffective base. ANS: B The ability of proteins to accept hydrogen ions limits H+ activity in solution, which is called buffering. The ability of hemoglobin to accept (i.e., buffer) H+ ions depends on its oxygenation state. Deoxygenated (reduced) hemoglobin is a stronger base (i.e., a better H+ acceptor) than oxygenated hemoglobin. DIF: Application REF: p. 276 OBJ: 6 34. What is the relation between pure water and acid-base balance? a. A solution with an OH concentration greater than that of water acts as an acid. b. Pure water is slightly acidic solution. c. The concentrations of both H+ and OH ions are equal. d. The H+ concentration of water can be designated as 1 nmol/L. ANS: C The concentration of both H+ and OH in pure water is 10-7 mol/L. DIF: Application REF: p. 277 OBJ: 7 35. How is pH defined? a. Log of the dissociation constant of the weak acid in a solution. b. Negative logarithm of the H+ ion concentration of a solution. c. Point at which an electrolyte solution is exactly 50% dissociated. d. Ratio of a solution’s weak acid concentration to its conjugate base pair. ANS: B pH is the negative logarithm of the [H+] used as a positive number. DIF: Application REF: p. 277 OBJ: 7 36. Which of the following describes an aspect of pH? a. Any solution with a pH of 7.0 is neutral. b. A pH of 7.0 describes an acidotic solution. c. A pH change from 7.0 to 8.0 equals a two-fold increase in H+ ion concentration. d. The pH is the log of the OH- ion concentration. ANS: A In this scheme, any solution with a pH of 7.0 is neutral, corresponding to the [H+] of pure water. DIF: Application REF: p. 277 OBJ: 7 37. If a patient’s pH were to drop from 7.40 to 7.10, the H+ concentration will increase by how much? a. 0.2 b. 0.3 c. 0.5 d. 0.10 ANS: A Similarly, a change in pH of 0.3 units equals a two-fold change in [H+]. DIF: Analysis REF: p. 277 OBJ: 7 38. Which of the following are true regarding water in the human body? 1. The more fatty tissue there is, the greater is the percentage of body water. 2. Total body water depends on an individual’s weight and sex. 3. Water constitutes approximately 45% to 80% of an individual’s body weight. 4. Water content is highest in the aged. a. 1 and 2 only b. 2 and 4 only c. 3 and 4 only d. 2 and 3 only ANS: D Water is a major component of the body. It makes up 45% to 80% of an individual’s body weight, depending on that person’s weight, gender, and age. Leanness is associated with higher body water content. Obese individuals have a lower percentage of body water (as much as 30% less) than do normal-weight individuals. Men have a slightly higher percentage of total body water than women have. Total percentage of body water in infants and children is substantially greater than it is in adults. In the newborn, water accounts for 80% of the total body weight. DIF: Application REF: p. 278 OBJ: 8 39. Intracellular water represents approximately what proportion of total body water? a. Approximately one-third of the total body water b. Approximately one-quarter of the total body water c. Approximately one-half of the total body water d. Approximately two-third of the total body water ANS: D Intracellular water accounts for approximately two-thirds of the total body water, and extracellular water accounts for the remaining third. DIF: Recall REF: p. 278 OBJ: 8 40. What is the smallest fluid subcompartment of extracellular water? a. Interstitial b. Intraorganelle c. Intravascular d. Transcellular ANS: D Extracellular water is found in three subcompartments: (1) intravascular water (plasma), (2) interstitial water, and (3) transcellular fluid. Intravascular water makes up approximately 5% of the body weight. Interstitial water is water in the tissues between the cells. It makes up approximately 15% of the body weight. Transcellular fluid is quite small in proportion to plasma and interstitial fluid. DIF: Application REF: p. 278 OBJ: 8 41. Which of the following are major extracellular electrolytes? 1. Cl– 2. HCO3– 3. K+ 4. Na+ a. 1, 2, and 3 only b. 2, 3, and 4 only c. 1, 3, and 4 only d. 1, 2, and 4 only ANS: D Sodium (Na+), chloride (Cl), and bicarbonate (HCO3) are the predominant extracellular electrolytes. DIF: Recall REF: p. 278 OBJ: 8 42. What are the main intracellular electrolytes? 1. K+ 2. Na+ 3. Phosphate 4. Sulfate a. 1, 3, and 4 only b. 2, 3, and 4 only c. 1 and 2 only d. 1, 2, 3, and 4 ANS: A Potassium (K+), magnesium (Mg2+), phosphate (PO 3), sulfate (SO 2), and protein constitute 4 4 the main intracellular electrolytes. DIF: Recall REF: p. 278 OBJ: 8 43. Which of the following is false regarding body fluids and electrolytes? a. Interstitial fluid contains substantially more protein than does plasma. b. Intravascular and interstitial fluid have similar electrolyte compositions. c. Osmotic pressure helps to determine fluid distribution between compartments. d. Proteins account for the high colloid osmotic pressure of plasma. ANS: A Intravascular and interstitial fluids have similar electrolyte compositions. However, plasma contains substantially more protein than interstitial fluid. Proteins, chiefly albumin, account for the high osmotic pressure of plasma. Osmotic pressure is an important determinant of fluid distribution between vascular and interstitial compartments. DIF: Application REF: p. 278 OBJ: 8 44. What maintains the volume and composition of body fluids? 1. Filtration and reabsorption of sodium by the kidneys 2. Regulation of water balance by vasopressin (ADH) 3. Gastrointestinal filtration and excretion of chloride a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3 ANS: A The kidneys maintain the volume and composition of body fluids by two related mechanisms. First, filtration and reabsorption of sodium adjust urinary sodium excretion to match changes in dietary intake. Second, water excretion is regulated by secretion of antidiuretic hormone (ADH or vasopressin). DIF: Application REF: p. 278 OBJ: 8 45. Water can be lost from the body through what organ systems? 1. Gastrointestinal tract 2. Liver 3. Lungs 4. Skin a. 1, 2, and 3 only b. 1, 3, and 4 only c. 2 and 4 only d. 1, 2, 3, and 4 ANS: B Water may be lost from the body through the skin, lungs, kidneys, and gastrointestinal tract. DIF: Application REF: p. 278 OBJ: 9 46. Insensible water loss occurs through what organs? 1. Gastrointestinal tract 2. Kidneys 3. Lungs 4. Skin a. 3 and 4 only b. 1, 2, and 4 only c. 2 and 3 only d. 2 and 4 only ANS: A Water loss can be insensible, such as vaporization of water from the skin and lungs. DIF: Application REF: p. 278 OBJ: 9 47. An adult’s insensible water loss averages what level? a. 300 ml/day b. 500 ml/day c. 700 ml/day d. 900 ml/day ANS: D See Table 13-4. DIF: Recall REF: p. 278 OBJ: 9 48. An adult’s insensible water through the lungs averages what level? a. 100 ml/day b. 200 ml/day c. 300 ml/day d. 400 ml/day ANS: B See Table 13-4. DIF: Recall REF: p. 278 OBJ: 9 49. What is the average urine output in a healthy adult? a. 600 to 800 ml/day b. 800 to 1000 ml/day c. 1000 to 1200 ml/day d. 1200 to 1400 ml/day ANS: C See Table 13-4. DIF: Recall REF: p. 278 OBJ: 9 50. Hyponatremia can lead to which of the following problems? 1. Impaired cognitive function 2. Negative effects on gait stability 3. Renal insufficiency 4. Cerebral edema a. 1 and 3 only b. 2 and 3 only c. 1, 2, and 4 only d. 1, 2, 3, and 4 ANS: C Once considered to be benign, mild hyponatremia has been shown in recent studies to have a significant impact on a patient’s cognitive function as well as his or her gait stability, it is thought to be a contributing factor in falls. Hyponatremia can lead to cerebral edema due to a change in osmotic pressure. DIF: Application REF: p. 281 OBJ: 9 51. Patients with what condition are prone to evaporative water loss through the lungs? 1. Artificial airways 2. Hypothermia 3. Increased ventilation a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3 ANS: B Patients with increased ventilation also have increased water losses through increased evaporation from the respiratory tract. Patients with artificial airways are prone to evaporative water loss if inspired air is not adequately humidified. Artificial airways bypass the normal heat and water exchange processes of the nose. DIF: Application REF: p. 279 OBJ: 9 52. Pick the statement that best describes the relationship between infants and their body fluids. a. Fluid loss or lack of intake depletes infants of water slower than it does adults. b. Infants have proportionately less body water than do adults. c. Infants’ higher metabolic rates necessitate greater urinary excretion compared with adults. d. Under normal circumstances, infants’ water loses are three times those of adults. ANS: C Infants have a greater proportion of body water than do adults, particularly in the extracellular compartments (Table 13-3). Water loss in infants may be twice that of adults. Infants also have a greater body surface area (in proportion to body volume) than adults, making their basal heat production twice as high. Higher metabolic rates in infants necessitate greater urinary excretion. Infants turn over approximately half of their extracellular fluid volume daily; adults turn over approximately one-seventh. Fluid loss or lack of intake can rapidly deplete an infant of water. DIF: Application REF: p. 278 OBJ: 9 53. By what process is water replenished? 1. Absorption 2. Ingestion 3. Metabolism a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3 ANS: C Water is replenished in two major ways: ingestion and metabolism. DIF: Application REF: p. 279 OBJ: 9 54. During recovery from a serious surgery or trauma, how much water is likely to be produced in a 24-hr period by the catabolism of fat and proteins? a. 300 ml b. 500 ml c. 750 ml d. 1000 ml ANS: D Recovery after surgery or trauma may be similar to starvation. Under such conditions, approximately 500 mg of protein and a similar amount of fat are metabolized. This yields approximately 1 L of water per day. DIF: Recall REF: p. 279 OBJ: 9 55. What best describes an aspect of the movement of fluid and solutes between the capillaries and the interstitial space? a. At the tissue level, osmotic pressure tends to draw water into the interstitial space. b. Electrolytes move freely across the capillary wall into the interstitium. c. The capillary and interstitial hydrostatic pressures are approximately equal. d. The interstitial fluid has a relatively high protein concentration. ANS: B The first stage of homeostasis is fluid exchange between systemic capillaries and interstitial fluid by passive diffusion. Capillary walls are permeable to crystalline electrolytes. This allows equilibrium between the two extracellular compartments to occur quickly. DIF: Application REF: p. 279 OBJ: 10 56. What is the net effect of the hydrostatic pressure gradient between the capillary and interstitial space? a. It tends to push water into the capillaries. b. It tends to push water into the interstitial spaces. c. The pressure gradient is zero so fluid movement is due to osmosis. d. It tends to push water into the cells. ANS: B Movement of fluid and solutes from capillary blood to interstitial spaces is enhanced by the difference in hydrostatic pressure between compartments. Hydrostatic pressure difference depends on blood pressure, blood volume, and the vertical distance of the capillary from the heart (i.e., the effects of gravity). Hydrostatic pressure tends to cause fluid to leak out of capillaries into the interstitial spaces. DIF: Application REF: p. 279 OBJ: 10 57. What establishes the capillary colloidal osmotic pressure? a. Presence of electrolytes in plasma b. Presence of plasma proteins in blood c. Presence of RBCs in whole blood d. Presence of WBCs in whole blood ANS: B Proteins such as albumin are too large to pass through the pores of the capillary. Instead, these proteins remain in the intravascular compartment and exert osmotic pressure, which draws water and small solute molecules back into the capillaries. This plasma colloid osmotic pressure is also sometimes called oncotic pressure. Because these large proteins are negatively charged, they attract (but do not bind) an equivalent amount of cations to the intravascular compartment. These cations have the effect of increasing osmotic pressure within the capillary (Donnan effect). DIF: Application REF: p. 283 OBJ: 10 58. What does the Donnan effect describe? a. How Cl– exchanges for HCO3– in RBCs at the tissue level. b. How proteins attract cations, which increase capillary osmotic pressure. c. Relationship between colloidal osmotic pressure and fluid movement at tissue. d. Relationship between osmotic and hydrostatic pressure at the capillary. ANS: B DIF: Application REF: p. 279 OBJ: 10 59. Describe the normal pressures or flows at the arterial end of the capillary. a. Electrolytes move from the interstitium into the capillary. b. Hydrostatic pressure is approximately 24 mm Hg. c. Osmotic pressure is approximately 30 mm Hg. d. Plasma minus the proteins flows into the interstitium. ANS: D For example, in a typical capillary, blood pressure is approximately 30 mm Hg at the arterial end and approximately 20 mm Hg at the venous end (Figure 12-6). Colloid osmotic pressure of the intravascular fluid remains constant at approximately 25 mm Hg. Hydrostatic pressure along the capillary continually decreases. At the arterial end, hydrostatic pressure normally exceeds osmotic pressure and water flows out of the vascular space into the interstitial space. DIF: Application REF: p. 279 OBJ: 10 60. Under normal circumstances, a small amount of fluid is filtered from the capillary in excess of that which is absorbed. What prevents edema from occurring under these conditions? a. The lymphatic system absorbs it and returns it to the circulatory system. b. Tissue cells absorb this fluid and use it in the metabolic process. c. Wandering macrophages use this excess fluid in hydrolyzing invaders. d. Waste products dilute this, maintaining eutonic conditions. ANS: A This slight outward excess is balanced by fluid return through the lymphatic circulation. DIF: Application REF: p. 283 OBJ: 10 61. According to the Starling equilibrium equation, which of the following will facilitate fluid filtration from the capillaries into the interstitial space? a. Low capillary hydrostatic pressure b. Low capillary permeability c. High capillary osmotic pressure d. High interstitial osmotic pressure ANS: D These relationships may be expressed by the Starling equilibrium equation. DIF: Analysis REF: p. 279 OBJ: 10 62. Which of the following factors contributes to reabsorption of tissue fluid in dependent regions of the body? a. Hydrostatic pressure of 100 mm Hg b. Low capillary permeability c. Low interstitial osmotic pressure d. Pumping action of skeletal muscles ANS: D Because of hydrostatic effects, capillary pressure in the feet can be as high as 100 mm Hg when an individual is standing. Reabsorption of tissue fluid can be accomplished although hydrostatic pressure greatly exceeds colloidal osmotic pressure. Three factors favor reabsorption under these circumstances. First, high intravascular hydrostatic pressure is somewhat balanced by a proportionally greater interstitial pressure. Second, the “pumping” action of the skeletal muscles surrounding leg veins lowers venous pressures. Third, lymph flow back to the thorax is enhanced by a similar mechanism. This facilitates clearance of excess interstitial fluid. DIF: Application REF: p. 279 OBJ: 10 63. The alveolar interstitial region of the lungs remains relatively “dry” primarily because of what? a. Low capillary hydrostatic pressure b. Low capillary osmotic pressure c. Low capillary permeability d. Low interstitial osmotic pressure ANS: A To minimize interstitial fluid in the alveolar-capillary region, the hydrostatic pressure difference must be kept low. The pulmonary circulation is in fact a low-pressure system. The mean pulmonary vascular pressures are approximately one-sixth of those in the systemic circulation. Colloid osmotic pressure exceeds hydrostatic forces across the entire length of the pulmonary capillaries in healthy individuals. DIF: Application REF: p. 279 OBJ: 10 64. What is a common cause for pulmonary edema due to increased hydrostatic pressure? a. Alveolar-capillary damage b. Chronic liver disease c. Failing left ventricle d. Failing right ventricle ANS: C In the lungs, edema caused by increased hydrostatic pressure often is a result of back pressure from a failing left ventricle. DIF: Application REF: p. 280 OBJ: 10 65. What is a normal range for serum sodium? a. 3.5 to 4.8 mEq/L b. 67.0 to 75.0 mEq/L c. 98.0 to 105.0 mEq/L d. 136.0 to 145.0 mEq/L ANS: D The normal serum concentration of sodium ranges from 136 to 145 mEq/L. DIF: Recall REF: p. 280 OBJ: 11 66. Na+ reabsorption in the kidneys is governed mainly by the level of what hormone? a. ADH b. Aldosterone c. Angiotensin d. Insulin ANS: B Sodium reabsorption in the kidneys is governed mainly by the level of aldosterone, which is secreted by the adrenal cortex. DIF: Application REF: p. 285 OBJ: 11 67. Which of the following would cause an abnormal loss of Na+ (hyponatremia)? 1. Ascites 2. Excessive sweating or fever 3. Use of certain diuretics 4. Steroid therapy a. 1 and 4 only b. 1, 2, and 4 only c. 1, 2, and 3 only d. 1, 2, 3, and 4 ANS: C Abnormal losses of sodium can lead to hyponatremia and may occur for a number of reasons, as shown in Table 13-5. DIF: Application REF: p. 285 OBJ: 11 68. What is the most prominent anion in the body? a. Chloride b. Bicarbonate c. Phosphate d. Sulfate ANS: A Chloride is the most prominent anion in the body. DIF: Recall REF: p. 286 OBJ: 11 69. What is a normal range for serum Cl–? a. 3.5 to 4.8 mEq/L b. 98.0 to 106.0 mEq/L c. 137.0 to147.0 mEq/L d. 150.0 to 220.0 mEq/L ANS: B Normal serum levels of chloride (Cl–) range between 98 and 106 mEq/L. DIF: Recall REF: p. 286 OBJ: 11 70. Which of the following correctly describes a facet of chloride? a. A loss of Cl– is equivalent to a gain in acid. b. Cl– is usually excreted with H+ as HCl. c. Cl– levels vary inversely with HCO 3– levels. d. Cl– plays a key role in acid-base buffering. ANS: C The concentration of extracellular chloride is inversely proportional to that of the other major anion, bicarbonate (HCO3–). DIF: Recall REF: p. 286 OBJ: 11 71. What can cause hypochloremia? 1. Diuretics 2. Gastrointestinal loss 3. Metabolic acidosis a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3 ANS: A Abnormal chloride levels may occur for a variety of reasons (see Table 13-5). DIF: Recall REF: p. 285 OBJ: 11 72. Which of the following describe roles played by HCO3-? 1. HCO3– levels vary directly with Cl- levels. 2. It is the primary vehicle for blood carbon dioxide transport. 3. It plays a key role in acid-base homeostasis. a. 1, 2, and 3 b. 1 and 3 only c. 2 only d. 2 and 3 only ANS: D HCO3– plays an important role in acid-base homeostasis and is the strong base in the bicarbonate-carbonic acid buffer pair. HCO3– is the primary means for transporting carbon dioxide from the tissues to the lungs. The ratio of HCO3– to carbonic acid in healthy individuals is maintained near 20:1. DIF: Application REF: p. 281 OBJ: 11 73. What is the role of kidneys when a patient experiences acute respiratory alkalosis? a. Cl– shift enhances the body’s compensatory mechanisms. b. HCO3– is eliminated in the urine. c. It dumps Cl– so as to retain HCO3–. d. The Hamburger phenomenon occurs. ANS: B In respiratory acidosis, the kidneys retain or produce HCO3– to buffer the additional acid caused by CO2 retention. In respiratory alkalosis, the opposite occurs. A reciprocal relationship exists between Cl– and HCO3– concentrations. Bicarbonate retention is associated with chloride excretion. DIF: Application REF: pp. 281-282 OBJ: 11 74. What cation is the most prominent in the intracellular compartment? a. Ca2+ b. K+ c. Li+ d. Na+ ANS: B Potassium is the main cation of the intracellular compartment. DIF: Recall REF: p. 282 OBJ: 1 75. What is a normal K+ blood level? a. 3.5 to 5.0 mEq/L b. 7.8 to 10.2 mEq/L c. 22 to 26 mEq/L d. 35 to 42 mEq/L ANS: A Serum K+ concentration normally ranges between only 3.5 and 5.0 mEq/L. DIF: Recall REF: p. 286 OBJ: 1 76. Which patients are prone to K+ depletion and hypokalemia? 1. Postsurgical patients 2. Those with renal disease 3. Trauma victims a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3 ANS: D Patients who have undergone surgery have sustained trauma, or have renal disease often have greater K+ losses. DIF: Application REF: p. 287 OBJ: 11 77. Which answer best describes the relationship between K+ movement and acid-base balance? a. Excess extracellular H+ ions are exchanged for intracellular K+. b. Extracellular acidosis results in serum hypokalemia. c. Low-K+ diets are required following nasogastric suctioning. d. When the extracellular pH rises, K+ moves out of the cells. ANS: A Serum K+ concentration is determined primarily by the pH of extracellular fluid and the size of the intracellular K+ pool. In extracellular acidosis, excess H+ ions are exchanged for intracellular K+. Movement of K+ from intracellular to extracellular spaces may produce dangerous levels of hyperkalemia. DIF: Application REF: p. 287 OBJ: 11 78. What effect do metabolic acidosis and aldosterone have in common? a. They both result in renal loss of K+. b. There is a loss of HCO3– and Cl– in the renal tubules. c. There is retention of CO2 and Cl–. d. They both cause renal retention of HCO3–. ANS: A Renal excretion of K+ is controlled by aldosterone levels. Aldosterone inhibits the enzyme responsible for K+ transport in the distal renal tubular cells of the kidney. Metabolic acidosis also inhibits the transport system. DIF: Application REF: p. 287 OBJ: 11 79. Hypokalemia disturbs cellular function in which of the following systems? 1. Gastrointestinal 2. Hepatic 3. Neuromuscular 4. Renal a. 1 and 2 only b. 2, 3, and 4 only c. 1, 3, and 4 only d. 2 and 4 only ANS: C Hypokalemia (reduced serum potassium) disturbs cellular function in a number of organ systems. These include the gastrointestinal, neuromuscular, renal, and cardiovascular systems. DIF: Recall REF: p. 285 OBJ: 11 80. What is the most common cause of hyperkalemia? a. Cardiac arrest b. Metabolic alkalosis c. Renal failure d. Respiratory acidosis ANS: C Hyperkalemia (elevated serum potassium) is most common in renal insufficiency. DIF: Recall REF: p. 285 OBJ: 11 81. Which of the following drugs can be used to temporarily lower K+ in severe hyperkalemia? a. Corticosteroids b. Insulin and glucose c. K-sparing diuretics d. Nonsteroidal antiinflammatory drugs ANS: B Temporary measures for reducing serum K+ levels include administration of insulin, calcium gluconate, sodium salts, or large volumes of hypertonic glucose. DIF: Recall REF: p. 287 OBJ: 11 82. What is the normal serum calcium concentration? a. 4.5 to 5.3 mg/dl b. 8.7 to 10.4 mg/dl c. 98.0 to 105.0 mg/dl d. 137 to 147 mg/dl ANS: B The normal serum calcium is 8.7 to 10.4 mg/dl or approximately 4.5 to 5.25 mEq/L. DIF: Recall REF: p. 287 OBJ: 11 83. Which of the following describes serum Ca2+? a. Approximately 30% of the serum Ca2+ is ionized and combined with plasma anions. b. Acidemia decreases the serum levels of ionized Ca2+. c. More than half of the serum Ca2+ is nonionized and bound to plasma albumin. d. Serum Ca2+ is present in three forms: ionized, protein bound, and complex. ANS: D Calcium is present in the blood in the following three forms: ionized, protein bound, and complex. Approximately 50% of serum calcium is ionized (Ca2+) and is physiologically active. An additional 10% forms calcium anion complexes. The remaining 40% is bound to plasma proteins, primarily albumen. Ionized calcium is physiologically active in processes such as enzyme activity, blood clotting, neuromuscular irritability, and bone calcification. Acidemia increases, and alkalemia decreases, the concentration of Ca2+ in the serum. DIF: Application REF: p. 283 OBJ: 11 84. Clinical symptoms of hyponatremia would include which of the following? 1. Headache 2. Bradycardia 3. Hypotension 4. Weakness a. 3 only b. 2 and 4 only c. 1, 3, and 4 only d. 1, 2, 3, and 4 ANS: C Symptoms of hyponatremia include: weakness, lassitude, apathy, headache, orthostatic hypotension, and tachycardia. DIF: Application REF: p. 281 OBJ: 11 85. Clinical signs of hypokalemia would include which of the following? 1. Cardiac arrest 2. Electrocardiogram abnormalities 3. Muscle weakness 4. Paralysis a. 1 and 2 only b. 2, 3 and 4 only c. 1, 2, and 3 only d. 1, 2, 3, and 4 ANS: D Symptoms of hypokalemia include: muscle weakness, paralysis, ECG abnormalities, supraventricular arrhythmias, circulatory failure, and cardiac arrest. DIF: Application REF: p. 281 OBJ: 11 86. Signs and symptoms of hyperkalemia would include which of the following? 1. Cardiac arrest 2. Electrocardiogram abnormalities 3. Metabolic alkalosis 4. Ventricular arrhythmias a. 1, 2, and 4 only b. 2 and 3 only c. 2, 3, and 4 only d. 1, 2, 3, and 4 ANS: A Symptoms of hyperkalemia include: ECG changes, ventricular arrhythmias, and cardiac arrest. DIF: Application REF: p. 281 OBJ: 11 87. Clinical manifestations of hypocalcemia would include which of the following? 1. Abdominal cramps 2. Depressed tendon reflexes 3. Electrocardiogram abnormalities 4. Muscular twitching and spasm a. 2 and 4 only b. 1 and 2 only c. 1, 3, and 4 only d. 3 only ANS: C Symptoms of hypocalcemia include: hyperactive tendon reflexes, muscle twitching, spasm, abdominal cramps, ECG changes, and convulsions. DIF: Application REF: p. 281 OBJ: 11 88. Symptoms of hypercalcemia would include which of the following? a. Depression b. Diarrhea c. Hyperactive tendon reflexes d. Muscle fasciculation ANS: A Symptoms of hypercalcemia include: fatigue, depression, muscle weakness, anorexia, nausea, vomiting, and constipation. DIF: Application REF: p. 281 OBJ: 11 89. What is hypercalcemia most often associated with? a. Hyperparathyroidism b. Kidney failure c. Pancreatitis d. Trauma ANS: A Hypercalcemia (increased levels of calcium) can result from numerous disorders. The most common causes are hyperparathyroidism (increased intestinal calcium absorption) and in malignancies (e.g., multiple myeloma, lung cancer). Normal values for serum Mg2+ range from 1.7 to 2.1 mg/dl (1.3 to 2.1 mEq/L) in healthy adults. DIF: Recall REF: p. 283 OBJ: 11 90. What are normal values for serum Mg2+? a. 1.3 to 2.1 mEq/L b. 3.5 to 4.8 mEq/L c. 9.0 to 10.5 mEq/L d. 98.0 to 105.0 mEq/L ANS: A Normal values for serum Mg++ range from 1.7 to 2.1 mg/dl (1.7 to 1.4 mEq/L) in healthy adults. DIF: Recall REF: p. 283 OBJ: 11 91. Where is most of the Mg2+ found in the body? a. Bound to phosphate b. Bound to proteins c. In the cells d. Ionized ANS: C Most (99%) of the magnesium in the body is intracellular. Of the small portion in extracellular spaces, 80% is ionized or bound to other ions (e.g., phosphate) with the remaining 20% bound to proteins. DIF: Recall REF: p. 287 OBJ: 11 92. What is the normal range for serum phosphate? a. 1.2 to 2.3 mEq/L b. 3.5 to 5.8 mEq/L c. 9.0 to 10.5 mEq/L d. 98.0 to 106.0 mEq/L ANS: A Only approximately 1% of the total-body phosphorus is available as free serum compounds, so the serum level (1.2 to 2.3 mEq/L) does not necessarily reflect total-body content. DIF: Recall REF: p. 283 OBJ: 11 93. The ease with which a solute dissolves into a solvent is at least partially determined by which of the following? a. Pressure of a solid b. Solute concentration c. Level of 2,3-DPG d. Solvent conductivity ANS: B The ease with which a solute dissolves in a solvent is its solubility, which is influenced by five factors: 1. Nature of the solute. The ease with which substances go into a solution in a given solvent depends on the forces of the solute-solute molecules and varies widely. 2. Nature of the solvent. A solvent’s ability to dissolve a solute depends on the bonds of the solvent-solvent molecules, and also varies widely. 3. Temperature. Solubility of most solids increases with increased temperature. However, the solubility of gases varies inversely with temperature. 4. Pressure. The solubility of solids and liquids is not greatly affected by pressure. The solubility of gases in liquids, however, varies directly with pressure. 5. Concentration. The concentration of a solute or available solvent will have an effect of how much of the substance goes into solution. DIF: Application REF: p. 271 OBJ: 2 94. Starling forces or fluid movement due to filtration across the wall of a capillary is dependent upon: 1. hydrostatic and oncotic pressure gradients across the capillary. 2. hydraulic (hydrostatic) in the vessel. 3. colloid osmotic pressure (COP) in the vessel. 4. colloid osmotic pressure (COP) in the tissue space. a. 1 and 4 only b. 1, 2, and 4 c. 2 and 3 only d. 1, 2, 3, and 4 ANS: D Ernst Starling was a nineteenth century British physiologist who studied fluid transport across membranes. His hypothesis states that the fluid movement due to filtration across the wall of a capillary is dependent upon both the hydrostatic and oncotic pressure gradients across the capillary. The driving force for fluid filtration across the wall of the capillary is determined by four separate pressures: hydraulic (hydrostatic), and colloid osmotic pressure (COP) both within the vessel and in the tissue space respectively. DIF: Application REF: p. 280 OBJ: 1 95. The most common causes of acute hyponatremia include: 1. postoperative iatrogenic causes. 2. not drinking enough water. 3. self-induced due to water intoxication. 4. not eating enough foods containing sodium. a. 1 and 3 b. 2 and 3 c. 1, 2, and 4 d. 1, 2, 3, and 4 ANS: A Hyponatremia can lead to cerebral edema due to a change in osmotic pressure. The two most common causes for acute hyponatremia are postoperative iatrogenic and self-induced due to water intoxication. DIF: Application REF: p. 281 OBJ: 11 Chapter 14 - Acid-Base Balance Kacmarek et al.: Egan’s Fundamentals of Respiratory Care, 11th Edition MULTIPLE CHOICE 1. The primary goal of acid-base homeostasis is to maintain which of the following? a. Normal HCO3– b. Normal PCO2 c. Normal pH d. Normal PO2 ANS: C Acid-base balance refers to physiological mechanisms that keep the H+ ion concentration of body fluids in a range compatible with life. DIF: Recall REF: p. 286 OBJ: 1 2. What is the normal arterial blood pH range? a. 7.25 to 7.35 b. 7.35 to 7.45 c. 7.45 to 7.55 d. 7.55 to 7.65 ANS: B To sustain life, the body must maintain the pH of fluids within a narrow range, from 7.35 to 7.45. DIF: Recall REF: p. 294 OBJ: 1 3. Which of the following is a volatile acid of physiologic significance? a. Hydrochloric b. Carbonic c. Phosphoric d. Lactic ANS: B The only volatile acid of physiologic significance in the body is carbonic acid (H2CO3), which is in equilibrium with dissolved CO2. DIF: Recall REF: p. 286 OBJ: 1 4. What are the major mechanisms responsible for maintaining a stable pH despite massive CO2 production? 1. Isohydric buffering 2. Gastrointestinal secretion 3. Pulmonary ventilation a. 2 and 3 only b. 1 and 2 only c. 1, 2, and 3 d. 1 and 3 only ANS: D Isohydric buffering and ventilation are the two major mechanisms responsible for maintaining a stable pH in the face of massive CO2 production. DIF: Application REF: p. 286 OBJ: 1 5. Fixed acids are produced primarily from the catabolism of which of the following? a. Carbohydrates b. Fats c. Proteins d. Simple sugars ANS: C Catabolism of proteins continually produces fixed (nonvolatile) acids such as sulfuric and phosphoric acids. DIF: Recall REF: p. 286 OBJ: 1 6. What is the primary buffer system for fixed acids? a. Cl– b. HCO3– c. Phosphate d. Plasma proteins ANS: B The H of fixed acids can be buffered by HCO – ions and converted to CO and H O (see the + 3 2 2 previous reaction); the CO2 thus formed is eliminated in exhaled gas. DIF: Recall REF: p. 289 OBJ: 1 7. By comparison, how much fixed acid is produced in any given period compared to the volatile acid CO2? a. Approximately the same amount b. Less fixed than volatile c. More fixed than volatile d. CO2 is not a volatile acid ANS: B Compared with daily CO2 production, fixed acid production is small, averaging only about 50 to 70 mEq/day. DIF: Recall REF: p. 286 OBJ: 1 8. Which of the following statements about the equilibrium constant of an acid is true? a. The equilibrium constant of a weak acid is large. b. The equilibrium constant of a strong acid is small. c. The equilibrium constant of a weak acid is small. d. The more an acid ionizes, the smaller is the equilibrium constant. ANS: C The KA is small because the H2CO3 concentration is quite large with respect to the numerator of reaction (3). The value of KA is always the same for H2CO3 at equilibrium, regardless of the initial concentration of H2CO3. A strong acid, such as HCl, has a large KA because the denominator [HCl] is extremely small, compared with the numerator ([H+]  [Cl]). DIF: Recall REF: p. 286 OBJ: 2 9. A solution that resists large changes in pH upon addition of an acid or a base best describes which of the following? a. Acid-base excretor b. Buffer solution c. Catabolic regulator d. Homeostatic control ANS: B A buffer solution resists changes in pH when an acid or a base is added to it. DIF: Recall REF: p. 287 OBJ: 3 10. When a strong acid is added to the bicarbonate buffer system, what is the result? a. Strong base and neutral salt b. Strong acid and neutral salt c. Weak acid and neutral salt d. Weak acid and basic salt ANS: C If hydrogen chloride, a strong acid, is added to the H2CO3/NaHCO3 buffer solution, HCO3– ions react with the added H+ ions to form weaker carbonic acid molecules and a neutral salt: HCl + H2CO3/Na+HCO3– 2H2CO3 + NaCl The strong acidity of HCl is converted to the relatively weak acidity of H2CO3, preventing a large decrease in pH. DIF: Recall REF: p. 287 OBJ: 3 11. Which of the following are components of the body’s nonbicarbonate buffer system? 1. Hemoglobin 2. Plasma proteins 3. Organic phosphates 4. Inorganic phosphates a. 1, 2, and 3 only b. 2 and 4 only c. 3 only d. 1, 2, 3, and 4 ANS: D The nonbicarbonate buffer system consists mainly of phosphates and proteins, including hemoglobin. DIF: Recall REF: p. 287 OBJ: 3 12. What is the sum of all blood buffers in 1 L of blood? a. Buffer base b. Base excess c. Standard bicarbonate d. Base deficit ANS: A The blood buffer base is the sum of bicarbonate and nonbicarbonate bases measured in mmol/L of blood. DIF: Recall REF: p. 287 OBJ: 3 13. Why is the bicarbonate buffer system considered an open buffer system? a. As the major blood and body buffer system, it is open by definition. b. It operates only in the extracellular fluid, avoiding cell closure. c. Its acid (carbonic acid) is converted to CO2 and removed. d. Its chemical reactions occur very quickly. ANS: C The bicarbonate system is called an open buffer system because H2CO3 is in equilibrium with dissolved CO2, which is readily removed by ventilation. DIF: Recall REF: p. 287 OBJ: 4 14. Why is a buffer system such as phosphate considered a closed system? a. All the components remain in the system. b. It has limited utility in buffering acids. c. Its ability to buffer volatile acids is incomplete. d. Once its buffer level is established, it will never change. ANS: A A nonbicarbonate buffer system is called a closed buffer system because all the components of acid-base reactions remain in the system. DIF: Recall REF: p. 287 OBJ: 4 15. What factor would limit the ability of the H2CO3/HCO 3– buffer system to perform efficiently? a. Temperature rise of more than 3° C b. Inadequate amount of 2,3-DPG in the blood c. Increased production of nonvolatile acids d. Lungs failing to excrete adequate levels of CO2 ANS: D For example, volatile acid (H2CO3) accumulates only if ventilation cannot eliminate CO2 fast enough to keep up with the body’s CO2 production. DIF: Recall REF: p. 287 OBJ: 4 16. Which buffer system has the greatest capacity? a. Bicarbonate b. Hemoglobin c. Phosphates d. Plasma proteins ANS: A Bicarbonate buffers have the greatest buffering capacity because they function in an open system. DIF: Recall REF: p. 287 OBJ: 4 17. What effect does hyperventilation have on the closed buffer systems? a. It causes them to bind with more H+. b. It causes them to release more H+. c. It has no effect on them at all. d. It increases the affinity of the closed buffer system. ANS: B Increased ventilation increases the CO2 removal rate, causing nonbicarbonate buffers to release H+ ions. Decreased ventilation ultimately causes nonbicarbonate buffers to accept more H+ ions. DIF: Recall REF: pp. 287-288 OBJ: 4 18. [H+] can be determined by the use of which factors? 1. HCO3– 2. H2CO3 3. Inorganic phosphorus 4. PaO2 a. 1, 2, and 3 only b. 2 and 3 only c. 4 only d. 1 and 2 only ANS: D [H+] = (KA  [H2CO3])/[HCO3–] Thus, [H+] is determined by the ratio between undissociated acid molecules [H2CO3] and base anions [HCO3–]. DIF: Recall REF: p. 288 OBJ: 4 19. A patient has a PCO2 of 80 mm Hg. What is the concentration of dissolved CO2 (in mmol/L) in the blood? a. 1.2 mmol/L b. 2.4 mmol/L c. 24 mmol/L d. 40 mmol/L ANS: B Because dissolved CO2 (PCO2  0.03) is in equilibrium with and directly proportional to blood [H2CO3], and because blood PCO2 is more easily measured than [H2CO3], dissolved CO2 is used in the denominator of the Henderson-Hasselbalch equation. DIF: Application REF: p. 288 OBJ: 4 20. Of what use is the Henderson-Hasselbalch equation for a clinician? a. It can guide therapeutic decision for critically ill patients. b. It establishes the baseline values for buffer enhancement treatments. c. Given H2CO3 and CO2 values, the pH can be computed. d. It allows validation of the reported values on a blood gas report. ANS: D The Henderson-Hasselbalch equation is useful for checking a clinical blood gas report to see if the pH, PCO2, and [HCO3] values are compatible with one another. DIF: Recall REF: pp. 288-289 OBJ: 5 21. What drives the bicarbonate buffer systems enormous ability to buffer acids? a. The fact that H2CO3 is a strong buffer b. The Henderson-Hasselbalch equation c. The large amounts of 2,3-DPG in red blood cells d. Ventilation continually removing CO2 from system ANS: D This allows HCO3– to continue buffering H+ as long as ventilation continues. Hypothetically, this buffering activity can continue until all body sources of HCO 3– are used up in binding H+ (i.e., the aforementioned reaction is continually pulled to the left because ventilation continually removes CO2). DIF: Recall REF: pp. 289-290 OBJ: 6 22. Of the nonbicarbonate buffer systems, which one is the most important? a. Hemoglobin b. Inorganic phosphates c. Organic phosphates d. Plasma proteins ANS: A The nonbicarbonate buffers in the blood. Of these, hemoglobin (Hb) is the most important because it is the most abundant. DIF: Recall REF: p. 290 OBJ: 6 23. Which of the following systems is primarily responsible for the buffering of fixed acids? a. Ammonia b. HCO3– c. Hb d. Phosphate ANS: B Most of the added fixed acid is buffered by HCO 3– because ventilation continually pulls the reaction to the left. DIF: Recall REF: p. 290 OBJ: 6 24. Which of the following acts as the “first-line” or immediate defense against the accumulation of H+ ions? a. Blood buffer system b. GI tract c. Renal system d. Respiratory system ANS: A Bicarbonate and nonbicarbonate buffer systems are the immediate defense against the accumulation of H+ ions. DIF: Recall REF: p. 295 OBJ: 6 25. Which of the following organ systems assist in acid excretion? 1. Kidneys 2. Liver 3. Lungs a. 3 only b. 1 and 3 only c. 2 only d. 1, 2, and 3 ANS: B The lungs and kidneys are the primary acid-excreting organs. DIF: Recall REF: p. 290 OBJ: 6 26. In regard to acid excretion by the body, which of the following statements are true? 1. If one system fails, the other can help compensate. 2. The kidneys can only remove fixed acids. 3. The kidneys can quickly remove acid. 4. The lungs can quickly remove acid. a. 1, 2, and 4 only b. 2 and 3 only c. 4 only d. 1 and 4 only ANS: A Bicarbonate buffers effectively buffer the H+ originating from fixed acid, converting it to H2CO3 and, in turn, to CO2 and H2O. By eliminating the CO2, the lungs can rapidly remove large quantities of fixed acid from the blood. The kidneys also remove fixed acids, but at a relatively slow pace. In healthy individuals, the acid excretion mechanisms of lungs and kidneys are delicately balanced. In diseased individuals, failure of one system can be partially offset by a compensatory response of the other. DIF: Recall REF: p. 289 OBJ: 6 27. The majority of the acid the body produces in a day is excreted through the lungs as CO2. What happens to the H+ ions? a. They are bound to Hb. b. They bind to phosphate. c. They form carbamino compounds. d. They bind to an OH-forming H2O. ANS: D The CO2 excretion of the lungs does not actually remove H+ ions from the body. Instead, the chemical reaction that breaks down H2CO3 to form CO2 binds H+ ions in the harmless water molecule: H+ + HCO3– H2CO3H 2O + CO 2 DIF: Recall REF: p. 290 OBJ: 6 28. Which organ system actually excretes H+ from the body? a. Kidneys b. Liver c. Lungs d. Spleen ANS: A The kidneys physically remove H+ from the body. DIF: Recall REF: p. 290 OBJ: 6 29. If the blood PCO2 is high, the kidneys will do which of the following? a. Excrete more H+ and reabsorb more HCO3–. b. Excrete less H+ and reabsorb more HCO3–. c. Excrete less H+ and reabsorb less HCO3–. d. Excrete more H+ and reabsorb less HCO3–. ANS: A If the blood PCO2 is high, creating high levels of H2CO3, then the kidneys excrete greater amounts of H+ and reabsorb all of the tubule filtrate’s HCO3– back into the blood. DIF: Recall REF: pp. 290-291 OBJ: 6 30. Normally which of the following occur when the kidneys eliminate H+? 1. Sodium ions (and water) are reabsorbed. 2. HCO3– is reabsorbed in proportion to the H+ excreted. 3. Bicarbonate buffer capacity is restored. a. 1, 2, and 3 b. 1 and 3 only c. 2 only d. 2 and 3 only ANS: A Both HCO3– ions and Na+ ions are reabsorbed with water whenever H+ ions are secreted into the tubular filtrate. DIF: Recall REF: pp. 291-292 OBJ: 6 31. What is the role of carbonic anhydrase in the kidneys? a. It drives the recovery of HCO3– and excretion of H+. b. It is the catalyst for the hamburger phenomenon. c. It promotes the excretion of CO2 in the urine. d. It promotes the loss of fluids in congestive heart failure. ANS: A The HCO3– ions in the filtrate react with the H+ ions secreted by the tubular cells. The resulting carbonic acid breaks down into CO2 and water. Because CO2 is extremely diffusible through biological membranes, it diffuses instantly into the tubule cell. There, CO2 reacts rapidly with water in the presence of carbonic anhydrase, rapidly forming HCO3– and H+. The HCO3–– ion diffuses back into the blood. Thus, the reabsorbed HCO3– ion is not the same HCO ion that existed in the tubular fluid. If the tubule cells secrete sufficient H+, all HCO – 3 3 in the tubular fluid is reabsorbed in this manner. DIF: Recall REF: p. 292 OBJ: 6 32. What effect does hyperventilation have on HCO3– recovery in the kidneys? a. Less H+ excretion, greater HCO3– loss b. No effect as these involve two independent systems. c. Vicious cycle of worsening alkalemia as hyperventilation stimulates increased HCO3– retention. d. Escalating retention of other buffer bases along with HCO3–. ANS: A If blood CO2 is low, as is the case in a state of hyperventilation (see Figure 14-3), the ratio of HCO – ions to dissolved CO molecules increases. Consequently, the renal filtrate has more 3 2 HCO – ions than H+ ions. Because HCO – cannot be reabsorbed without first reacting with H+, 3 3 the excess HCO3– ions are excreted in the urine, carrying with them positive ions in the filtrate such as Na+ or K+. Therefore, the net effect of secreting fewer H+ ions is to increase the quantity of HCO3– (base) lost in the urine. DIF: Recall REF: p. 292 OBJ: 6 33. What is the limiting factor for H+ excretion in the renal tubules? a. Excessive amounts of Cl– b. Excessive amounts of HCO3– c. Insufficient buffers d. Insufficient sodium ANS: C When filtrate pH falls to 4.5, H+ secretion stops. Buffers in the tubular fluid are essential for the secretion and elimination of excess H+ ions in acidotic states. DIF: Recall REF: p. 292 OBJ: 7 34. Which of the following mechanisms helps to eliminate excess H+ via the kidneys? 1. Reabsorption of HCO3– 2. Phosphate buffering 3. Ammonia buffering a. 2 and 3 only b. 1 and 3 only c. 2 only d. 1, 2, and 3 ANS: D After all available HCO3– ions react with H+ ions, the remaining H+ ions react with two other filtrate buffers, phosphate and ammonia, as illustrated in Figures 13-4 and 13-5. DIF: Recall REF: p. 292 OBJ: 7 35. Which of the following is/are true about the relationship between chloride (Cl–) and bicarbonate HCO3– in acid-base balance? 1. For each Cl– ion excreted into the urine, the blood gains an HCO 3– ion. 2. Blood Cl– and HCO3– ion levels are reciprocally related. 3. People with chronically high CO2 tend to have low blood Cl– levels. 4. Activation of the NH3 buffer system enhances Cl– gain and HCO3 loss. a. 2 and 3 only b. 1, 2, and 3 only c. 2 only d. 2, 3, and 4 only ANS: B The net effect of ammonia buffer activity is to cause more bicarbonate to be reabsorbed into the blood, counteracting the acidic state of the blood. Figure 14-5 shows that when a Cl– ion is excreted in combination with an ammonium ion, the blood gains an HCO3– ion. Thus, blood Cl– and HCO 3– ion concentrations are reciprocally related (i.e., when one is high, the other is low). This explains why people with chronically high blood PCO2 tend to have low blood Cl concentrations. Activation of the ammonia buffer system enhances Cl– loss and HCO 3– gain. DIF: Recall REF: p. 294 OBJ: 7 36. Which organ system maintains the normal level of HCO 3– at 24 mEq/L? a. Liver b. Lung c. Renal d. Spleen ANS: C Normally, the kidneys maintain an arterial bicarbonate concentration of approximately 24 mEq/L, whereas lung ventilation maintains an arterial PCO2 of approximately 40 mm Hg. DIF: Recall REF: p. 294 OBJ: 7 37. According to the Henderson-Hasselbalch equation, the pH of the blood will be normal as long as the ratio of HCO3– to dissolved CO2 is which of the following? a. 10:1 b. 20:1 c. 24:1 d. 30:1 ANS: B Note that the pH is determined by the ratio of [HCO –] to dissolved CO , rather than by the 3 2 absolute values of these components. As long as the ratio of HCO – buffer to dissolved CO is 3 2 20:1, the pH is normal, or 7.40. DIF: Recall REF: p. 294 OBJ: 7 38. The numerator of the Henderson-Hasselbalch (H-H) equation (HCO 3–) relates to which of the following? a. Blood concentration of nonbicarbonate buffers b. Excretion of volatile acid by the lungs c. Renal buffering and excretion of fixed acids d. Respiratory component of acid-base balance ANS: C Because the kidneys control blood [HCO –] and the lungs control blood CO levels, the H-H 3 2 equation can be conceptually rewritten as follows: PH  kidneys/lungs. DIF: Recall REF: p. 294 OBJ: 7 39. According to the Henderson-Hasselbalch equation, the blood pH will rise (alkalemia) under which of the following conditions? 1. The buffer capacity increases. 2. The volatile acid (CO2) increases. 3. The volatile acid (CO2) decreases. 4. The buffer capacity decreases. a. 1 only b. 3 only c. 1 and 3 only d. 2 and 4 only ANS: C An increase in [HCO3–] or a decrease in PCO 2will raise the pH, leading to alkalemia. DIF: Recall REF: p. 294 OBJ: 7 40. When does a –state of alkalemia exist? 1. The HCO /CO ratio exceeds 20:1. 3 2 2. The blood pH exceeds 7.45. 3. The blood PCO2 exceeds 54 mm Hg. a. 2 and 3 only b. 1, 2, and 3 c. 3 only d. 1 and 2 only ANS: D An increase in [HCO –] or a decrease in PCO will raise the pH, leading to alkalemia. This 3 2 produces a [HCO –]/(PCO  0.03) ratio greater than 20:1 (e.g., 25:1). A decreased [HCO –] or 3 2 3 an increased PCO2 decreases the pH, leading to acidemia. This produces a [HCO3–]/(PCO2 0.03) ratio less than 20:1 (e.g., 15:1). The normal ranges for arterial pH, PCO2, and [HCO3–] are as follows: pH = 7.35 to 7.45 PaCO2 = 35 to 45 mm Hg [HCO3–] = 22 to 26 mEq/L Alkalemia is defined as a blood pH greater than 7.45. DIF: Recall REF: p. 294 OBJ: 7 41. What is the primary chemical event in respiratory acidosis? a. Decrease in blood CO2 levels b. Decrease in blood HCO3– levels c. Increase in blood CO2 levels d. Increase in blood HCO3– levels ANS: C A high PaCO2 increases dissolved CO2, lowering the pH: pH HCO3–/PaCO2 where means decreased, means no change, and means increased. Respiratory disturbances causing acidemia are called respiratory acidosis. DIF: Recall REF: p. 294 OBJ: 7 42. What is the primary chemical event in metabolic alkalosis? a. Decrease in blood CO2 levels b. Decrease in blood HCO3– levels c. Increase in blood CO2 levels d. Increase in blood HCO3– levels ANS: D Processes that increase arterial pH by losing fixed acid or gaining HCO 3– produce a condition called metabolic alkalosis. DIF: Recall REF: p. 294 OBJ: 7 43. What is a normal response of the body to a failure in one component of the acid-base regulatory mechanism? a. Autoregulation b. Compensation c. Correction d. Homeostasis ANS: B When any primary acid-base defect occurs, the body immediately initiates a compensatory response. DIF: Recall REF: p. 294 OBJ: 7 44. Compensation for respiratory acidosis occurs through which of the following? a. Decrease in blood CO2 levels b. Decrease in blood HCO3– levels c. Increase in blood CO2 levels d. Increase in blood HCO3– levels ANS: D For example, in hypoventilation (respiratory acidosis), the kidneys restore the pH toward normal by reabsorbing HCO3– into the blood. DIF: Recall REF: p. 295 OBJ: 7 45. Compensation for metabolic acidosis occurs through which of the following? a. Increase in blood CO2 levels b. Decrease in blood CO2 levels c. Decrease in blood HCO 3– levels d. Increase in blood HCO3– levels ANS: B If a nonrespiratory (metabolic) process lowers or raises [HCO3–], the lungs compensate by hyperventilating (eliminating CO2) or hypoventilating (retaining CO2), restoring the pH to near normal. DIF: Recall REF: p. 295 OBJ: 7 46. A patient has a bicarbonate concentration of 36 mEq and a PCO2 of 60 mm Hg. What is the approximate pH? a. 7.2 b. 7.3 c. 7.4 d. 7.5 ANS: C The kidneys compensate by retaining HCO –, returning the plasma HCO –/dissolved CO ratio 3 3 2 to almost 20:1. The conversion of PCO2 to mEq is done by multiplying by 0.03. Thus 60  0.03 = 1.8. 36 to 1.8 is equal to a 20 to 1 ratio, thus the pH should be 7.40. DIF: Application REF: p. 295 OBJ: 7 47. Which of the following accurately describes compensation for acid-base disorders? a. Kidneys take hours to days to compensate for respiratory disorders. b. Lungs take hours to days to compensate for metabolic disorders. c. Renal compensation is always complete. d. Respiratory compensation is always complete. ANS: A The lungs normally compensate quickly for metabolic acid-base defects because ventilation can change the PaCO2 within seconds. The kidneys require more time to retain or excrete significant amounts of HCO3–, and thus compensate for respiratory defects at a much slower pace. DIF: Recall REF: p. 295 OBJ: 7 48. A patient with a measured plasma HCO3 – concentration of 24 mmol/L has an episode of acute hypoventilation, with the PCO2 rising from 40 to 70 mm Hg. What do you predict will happen acutely to the plasma HCO3– concentration? a. HCO3– will remain unchanged. b. HCO3– will rise to approximately 27 to 28 mmol/L. c. HCO3– will fall to approximately 20 to 21 mmol/L. d. HCO3– will rise to approximately 54 to 55 mmol/L. ANS: B In general, when the nonbicarbonate buffer concentration is normal and the PCO2 rise is acute, the hydration reaction raises the plasma [HCO3–] approximately 1 mEq/L for every 10 mm Hg increase in PCO2 higher than 40 mm Hg. DIF: Application REF: p. 295 OBJ: 7 49. A patient has a pH of 7.49. How would you describe this? a. Acidemia b. Alkalemia c. Not sufficient information to determine d. Normal acid-base status ANS: B Alkalemia is defined as a blood pH greater than 7.45. Acidemia is defined as a blood pH less than 7.35. DIF: Recall REF: p. 296 OBJ: 8 50. An increase in the H+ ion concentration [H+] of the blood due only to an increase in the arterial PCO2 (hypercapnia) best describes which of the following? a. Metabolic acidosis b. Metabolic alkalosis c. Respiratory acidosis d. Respiratory alkalosis ANS: C For example, if the pH was lower than 7.35 (denoting an acidosis) and the PaCO2 was higher than 45 mm Hg, according to the H-H equation, the high PaCO2 would indeed lower the pH (i.e., produce an acidosis). Therefore, the respiratory system is at least in part, if not entirely, responsible for the acidosis. DIF: Recall REF: p. 297 OBJ: 8 51. An ABG result shows the pH to be 7.56 and the HCO 3- to be 23 mEq/L. Which of the following is the most likely disorder? a. Metabolic acidosis b. Metabolic alkalosis c. Respiratory acidosis d. Respiratory alkalosis ANS: D If HCO3– is in the normal range in the presence of alkalosis, then the alkalosis probably is of respiratory origin. DIF: Recall REF: p. 297 OBJ: 8 52. An ABG result shows pH of 7.35, PaCO2 of 30 mm Hg, and HCO 3– of 18 mEq/L. Which of the following is the patient’s most likely primary disorder? a. Metabolic acidosis b. Metabolic alkalosis c. Respiratory acidosis d. Respiratory alkalosis ANS: A In cases in which compensation has occurred, if the pH is on the acidic side of 7.40 (7.35 to 7.39), the component that would cause an acidosis (either increased PaCO2 or decreased plasma HCO3–) is generally the primary cause of the original acid-base imbalance. DIF: Application REF: p. 297 OBJ: 8 53. An ABG result shows pH of 7.35, PaCO2 of 30 mm Hg, and HCO3– of 18 mEq/L. What compensatory measure has the body taken to at least partially compensate for the acid-base disorder? a. Blown off CO2 b. Retained HCO3– c. Retained H+ d. Not enough information to determine ANS: A The patient has a compensated metabolic acidosis. This is characterized by a low HCO3–, a pH between 7.35 and 7.39, and a low PaCO2. The compensatory response (decreased PaCO2) has restored the pH to the low normal range. DIF: Application REF: p. 297 OBJ: 8 54. Which of the following clinical findings would you expect in a fully compensated respiratory acidosis? 1. Elevated HCO3– 2. pH below 7.35 3. pH between 7.35 and 7.39 4. Elevated PO2 a. 1 and 3 only b. 2 and 3 only c. 2 and 4 only d. 1, 3, and 4 only ANS: A This completely compensated respiratory acidosis is characterized by the same originally observed high PaCO2, a pH that is now in the 7.35 to 7.39 range, and a plasma [HCO 3–] that is greater than it was before complete compensation took place. DIF: Recall REF: p. 298 OBJ: 9 55. Causes of respiratory acidosis in patients with normal lungs include which of the following? 1. Neuromuscular disorders 2. Spinal cord trauma 3. Anesthesia 4. Use of incentive spirometry a. 1, 2, and 3 only b. 4 only c. 2, 3, and 4 only d. 1 and 3 only ANS: A Any process in which alveolar ventilation fails to eliminate CO2 as rapidly as the body produces it causes respiratory acidosis. This could occur in different ways. A person’s ventilation may be decreased from a drug-induced central nervous system depression. DIF: Recall REF: p. 298 OBJ: 9 56. In the face of uncompensated respiratory acidosis, which of the following blood gas abnormalities would you expect to encounter? 1. Decreased pH 2. Increased HCO3– 3. Increased PCO2 4. Increased pH a. 1, 2, and 4 only b. 1 and 3 only c. 3 only d. 2, 3, and 4 only ANS: B If hypercapnia is uncompensated, respiratory acidosis occurs with a low pH, a high PaCO2, and a normal or slightly high [HCO3–]. In this instance, the slightly high [HCO 3–] is not a sign that the kidneys have started compensatory activity; it merely reflects the effect of CO2 hydration reaction on [HCO3–]. DIF: Recall REF: p. 298 OBJ: 9 57. How is acute respiratory acidosis accomplished? a. By increasing HCO3– reabsorption b. By increasing alveolar ventilation c. By decreasing HCO3– reabsorption d. By decreasing alveolar ventilation ANS: B The main goal in correcting respiratory acidosis is to improve alveolar ventilation. This may entail various respiratory care modalities ranging from bronchial hygiene and lung expansion techniques to endotracheal intubation and mechanical ventilation. DIF: Recall REF: p. 298 OBJ: 9 58. A decrease in the H+ ion concentration [H+] of the blood caused by a low PaCO2 best describes which of the following? a. Metabolic acidosis b. Metabolic alkalosis c. Respiratory acidosis d. Respiratory alkalosis ANS: D Any physiologic process that lowers the arterial PCO2 (7.45) produces respiratory alkalosis. DIF: Recall REF: p. 298 OBJ: 9 59. What is the most common cause of respiratory alkalosis? a. Anxiety b. Central nervous system depression c. Hypoxemia d. Pain ANS: C The most common cause of hyperventilation in patients with pulmonary disease is probably a low arterial PO2 (hypoxemia). DIF: Recall REF: p. 299 OBJ: 9 60. Which of the following are potential causes of respiratory alkalosis? 1. Anxiety 2. Central nervous system depression 3. Hypoxemia 4. Pain a. 1, 2, and 3 only b. 1, 3, and 4 only c. 1 and 4 only d. 1, 2, 3, and 4 ANS: B Hypoxemia causes specialized neural structures to signal the brain, increasing ventilation (see Chapter 14). Anxiety, fever, stimulatory drugs, pain, and central nervous system injuries are possible causes of hyperventilation. DIF: Recall REF: p. 299 OBJ: 9 61. What condition or treatment could cause iatrogenic respiratory alkalosis? a. Central nervous system stimulation b. Mechanical hyperventilation c. Severe hypoxemia d. Vagal stimulation ANS: B Hyperventilation and respiratory alkalosis also may be iatrogenically induced (induced by medical treatment). Such hyperventilation is most commonly associated with overly aggressive mechanical ventilation. DIF: Recall REF: p. 299 OBJ: 9 62. Which of the following are signs and symptoms of acute respiratory alkalosis? 1. Convulsions 2. Depressed reflexes 3. Dizziness 4. Paresthesia a. 1, 2, and 4 only b. 1, 3, and 4 only c. 2 and 4 only d. 1, 2, 3, and 4 ANS: B An early sign of respiratory alkalosis is paresthesia (numbness or a tingling sensation in the extremities). Severe hyperventilation is associated with dizziness, hyperactive reflexes, and possibly tetanic convulsions. DIF: Recall REF: p. 300 OBJ: 9 63. Compensation for respiratory alkalosis occurs through which of the following? a. Renal excretion of H+ b. Renal excretion of HCO3– c. Renal excretion of NH4+ d. Renal reabsorption of HCO3– ANS: B The kidneys compensate for respiratory alkalosis by excreting HCO3– in the urine (bicarbonate diuresis; see Figure 14-3). DIF: Recall REF: p. 300 OBJ: 9 64. In a patient with partially compensated respiratory alkalosis, which of the following blood gas abnormalities would you expect to encounter? 1. Decreased pH 2. Decreased HCO3– 3. Decreased PCO2 4. Increased pH a. 1, 2, and 4 b. 1 and 3 c. 3 only d. 2, 3, and 4 ANS: D Partly compensated respiratory alkalosis is characterized by a low PaCO2, a low [HCO 3–], and an alkaline pH—still not quite down in the normal range. DIF: Recall REF: p. 300 OBJ: 9 65. A patient who has fully compensated respiratory acidosis becomes severely hypoxic. If her lungs are not too severely compromised, what might her gases now appear to be? a. Fully compensated metabolic acidosis b. Fully compensated metabolic alkalosis c. Fully compensated respiratory alkalosis d. No change ANS: B Consider a patient with a compensated respiratory acidosis who has an arterial pH of 7.38, a PaCO2 of 58 mm Hg, and an HCO3– of 33 mEq/L. If this patient becomes severely hypoxic, the hypoxia may stimulate increased alveolar ventilation if lung mechanics are not too severely deranged. This would acutely lower the PaCO2, possibly raising the pH to the alkalotic side of normal. For example, the patient’s blood gas values might now be as follows: pH of 7.44, PaCO2 of 50 mm Hg, and HCO3– of 33 mEq/L. DIF: Application REF: p. 300 OBJ: 9 66. Metabolic acidosis may be caused by: 1. an increase in fixed (nonvolatile) acids. 2. an increase in blood carbon dioxide (CO2). 3. excessive loss of bicarbonate (HCO3–). a. 1 only b. 1 and 2 only c. 1, 2, and 3 d. 1 and 3 only ANS: D Metabolic acidosis can occur in one of the following two ways: (1) fixed (nonvolatile) acid accumulation in the blood or (2) an excessive loss of HCO3– from the body. DIF: Recall REF: p. 300 OBJ: 9 67. What is a normal anion gap range? a. 3 to 5 mEq/L b. 6 to 8 mEq/L c. 9 to 14 mEq/L d. 24 to 26 mEq/L ANS: C A value of 140 mEq/L for Na+, 105 mEq/L for Cl, and 24 mEq/L for HCO3–, yielding an anion gap of 11 mEq/L (140 mEq/L – [105 mEq/L + 24 mEq/L] = 11 mEq/L). The normal anion gap range is 9 to 14 mEq/L. DIF: Recall REF: p. 301 OBJ: 11 68. A patient has an anion gap of 21 mEq/L. Based on this information, what can you conclude? 1. There is an abnormal excess of unmeasured anions in the plasma. 2. The patient probably has metabolic acidosis. 3. The concentration of fixed acids is decreased. a. 2 only b. 1 and 2 only c. 1 and 3 only d. 3 only ANS: B An increased anion gap (>14 mEq/L) is caused by metabolic acidosis in which fixed acids accumulate in the body. DIF: Application REF: p. 301 OBJ: 11 69. What explains the lack of an increased anion gap seen in metabolic acidosis caused by HCO 3– loss? a. For each HCO 3– ion lost, a Cl– ion is reabsorbed by the kidney. b. For each HCO3– ion lost, the body produces another to replace it. c. HCO3– is not a measured anion, so its loss does not affect the anion gap. d. Replacement of HCO3– occurs by ammonia ions which are also anions. ANS: A A metabolic acidosis caused by HCO3– loss from the body does not cause an increased anion gap. Bicarbonate loss is accompanied by Cl– ion gain, which keeps the anion gap within normal limits (Figure 14-7, C). DIF: Recall REF: p. 301 OBJ: 11 70. What are some causes of metabolic acidosis with an increased anion gap? 1. Diarrhea 2. Ketoacidosis 3. Lactic acidosis 4. Renal failure a. 2 and 3 only b. 2 and 4 only c. 2, 3, and 4 only d. 1, 3, and 4 only ANS: C Box 14-5 summarizes causes of anion gap and nonanion gap metabolic acidosis. DIF: Recall REF: p. 301 OBJ: 10 | 11 71. Which of the following is/are cause(s) of hyperchloremic metabolic acidosis? 1. Hyperalimentation 2. Methanol intoxication 3. Severe diarrhea 4. NH4Cl administration a. 2 only b. 1 and 4 only c. 1, 3, and 4 only d. 1, 2, 3, and 4 ANS: B Box 14-5 summarizes causes of anion gap and nonanion gap metabolic acidosis. DIF: Recall REF: p. 301 OBJ: 10 | 11 72. What is the main compensatory mechanism for metabolic acidosis? a. Excretion of HCO3– b. Hyperventilation c. Hypoventilation d. Retention of CO2 ANS: B Hyperventilation is the main compensatory mechanism for metabolic acidosis. The increased plasma [H+] of metabolic acidosis is buffered by plasma HCO3–, reducing the plasma [HCO3–], and thus the pH. Uncompensated metabolic acidosis suggests that a ventilatory defect must exist. DIF: Recall REF: p. 302 OBJ: 9 | 10 | 11 73. In a patient with Kussmaul’s respirations, what acid-base disturbance would you expect to see? a. Metabolic acidosis b. Metabolic alkalosis c. Respiratory acidosis d. Respiratory alkalosis ANS: A With severe diabetic ketoacidosis, a very deep, gasping type of breathing develops, called Kussmaul’s respiration. DIF: Recall REF: p. 302 OBJ: 9 | 11 74. What is the treatment for severe metabolic acidosis? a. Charcoal b. Insulin c. Glucose d. NaHCO3– infusion ANS: D In cases of severe metabolic acidosis, intravenous infusion of sodium bicarbonate (NaHCO 3–) may be indicated. DIF: Recall REF: p. 302 OBJ: 9 | 11 75. Primary metabolic alkalosis is associated with which of the following? a. Gain of buffer base b. Gain in fixed acids c. Low blood CO2 levels d. Diabetic crisis ANS: A Metabolic alkalosis can occur in one of the following two ways: (1) loss of fixed acids or (2) gain of blood buffer base. DIF: Recall REF: p. 302 OBJ: 9 | 11 76. Which of the following is/are cause(s) of metabolic alkalosis? 1. Diuretics 2. Hyperkalemia 3. Hypochloremia 4. Vomiting a. 1, 3, and 4 only b. 2 and 3 only c. 1, 2, and 4 only d. 2 only ANS: A The causes of metabolic alkalosis are summarized in Box 14-6. DIF: Recall REF: p. 303 OBJ: 9 | 11 77. What would be an example of an iatrogenic cause of metabolic alkalosis? a. Gastric suction b. High-salt diet c. Discontinuing the patient’s diuretics d. Vomiting ANS: A Often, metabolic alkalosis is iatrogenic, resulting from the use of diuretics, low-salt diets, and gastric drainage. DIF: Recall REF: p. 303 OBJ: 9 | 11 78. What is the kidneys’ most important function? a. Acid-base balance b. Chloride maintenance c. HCO3– maintenance d. Sodium maintenance ANS: D The kidneys’ main job is to reabsorb sodium, not excrete it. For this reason, and because sodium has a major role in maintaining fluid balance, the kidney places a greater priority on reabsorbing Na+ than on maintaining Cl–, K+, or acid-base balance. DIF: Recall REF: p. 303 OBJ: 9 | 11 79. What compensates for a metabolic alkalosis? a. Hyperventilation b. Hypoventilation c. Renal excretion of HCO3– d. Renal retention of H+ ANS: B The expected compensatory response to metabolic alkalosis is hypoventilation (CO2 retention). DIF: Recall REF: p. 304 OBJ: 9 | 11 80. Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.43, PCO2 = 39 mm Hg, HCO3– = 25.1 mEq/L a. Acid-base status within normal limits b. Fully compensated metabolic acidosis c. Fully compensated respiratory alkalosis d. Partially compensated metabolic acidosis ANS: A As all the ABG values are within normal limits the gas must be normal. DIF: Recall REF: pp. 296-297 OBJ: 9 | 11 81. Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.62, PCO2 = 41 mm Hg, HCO3– = 40.9 mEq/L a. Acute (uncompensated) metabolic alkalosis b. Acute (uncompensated) respiratory alkalosis c. Fully compensated metabolic alkalosis d. Partially compensated metabolic alkalosis ANS: A The patient is alkalotic (pH >7.35). This can be caused by an elevated HCO – or a low PCO. 3 2 In this question the HCO – is elevated. If compensation were present the PCO would have to 3 2 be elevated. As it is normal, this is an uncompensated metabolic alkalosis. DIF: Application REF: p. 303 OBJ: 9 | 11 82. Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.43, PCO2 = 20 mm Hg, HCO3– = 12.6 mEq/L a. Acute (uncompensated) respiratory alkalosis b. Fully compensated metabolic acidosis c. Fully compensated respiratory alkalosis d. Partially compensated respiratory alkalosis ANS: C The patient’s pH is normal so either the gas is normal or fully compensated. As the PCO2 and HCO3– are both low, a fully compensated state exists. As the pH is on the high side of normal the fully compensated disorder would be alkalosis. This would be caused by a low PCO2 or a high HCO3–. In this case a low PCO2. The low HCO3– is compensating for this respiratory alkalosis. DIF: Application REF: p. 295 OBJ: 9 | 11 83. Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 6.89, PCO2 = 24 mm Hg, HCO3– = 4.7 mEq/L a. Acute (uncompensated) metabolic acidosis b. Acute (uncompensated) respiratory acidosis c. Partially compensated metabolic acidosis d. Partially compensated respiratory acidosis ANS: C The patient is acidotic (pH-

Chapter 13 - Solutions, Body Fluids, and Electrolytes PDF

Document Details

Tags

Related

Summary

Full Transcript