Study Guide Concepts of Acid-Base Balance

Question 1

Which pH value indicates the highest concentration of free hydrogen ions in the blood and other extracellular fluids?

A. 7.57
B. 7.47
C. 7.37
D. 7.27

Answer 1

D.

The blood level of free hydrogen ions is calculated in negative logarithm units. This calculation makes the value of pH inversely related (negatively related) to the concentration of free hydrogen ions. Thus, the lower the pH value of a fluid, the higher the level of free hydrogen ions in that fluid.

Question 2

Which client arterial blood gas results would the nurse interpret as within normal limits?
A. pH 7.28, PaCO, 24, bicarbonate 15,
Pa02 95
B. pH 7.45, PaCO, 41, bicarbonate 25,
Pa02 97
C. pH 7.35, PaCO, 24, bicarbonate 15,
Pa0, 95
D. pH 7.30, PaCO2 66, bicarbonate 38,
Pa0, 70

Answer 2

B

The normal arterial pH range is 7.35-7.45.
The normal PaCO2 range is 35-45 mm Hg.
The normal PaO2 range is 80-100 mm Hg.
The normal arterial bicarbonate range is 21-28 mEq/L (mmol/L).

Question 3

Which arterial blood pH level can be fatal?
A. 7.22
B. 7.11
C. 7.05
D. 6.85

Answer 3

D.

An arterial pH below 6.85 is considered incompatible with life because all vital organ functions would be inhibited.

Question 4

By which mechanism do buffers help maintain arterial blood pH within the normal range?
A. Binding excess free hydrogen ions
B. Increasing kidney excretion of free hydrogen ions
C. Triggering increased bicarbonate production in the pancreas
D. Stimulating respiratory neurons to increase the rate and depth of ventilation

Answer 4

A.

Buffers in body fluids act like hydrogen ion “sponges,” soaking up hydrogen ions when too many are present and squeezing out hydrogen ions when very few are present. Buffers have no mechanism to change kidney, pancreas, or neuronal function.

Question 5

What changes in body functions does the nurse anticipate in a client who has lower than normal blood pH levels? Select all that apply.

A. Decreased serum potassium levels
B. Increased effectiveness of drugs
C.
Reduced function of hormones
D.
Increased function of enzymes
E.
Decreased electrical conduction in the heart
F.
Decreased skeletal muscle strength

Answer 5

C,E, F

Higher concentration of hydrogen ions (reflected by a lower pH) increases (not decreases) serum potassium levels, decreases effectiveness of drugs, reduces function of hormones, reduces function of enzymes, slows electrical conduction through the heart (because of the elevated potassium levels) and decreases muscle strength.

Question 6

The continuous normal function of which organs is most critical for acid-base balance? Select all that apply.

A. Adrenal glands
B. Bladder
C. Heart
D. Kidneys
E. Liver
F. Lungs

Answer 6

D, F

The kidneys are critical in retaining and eliminating hydrogen ions and bicarbonate to maintain acid-base balance. The lungs are the organs that control carbon dioxide elimination. Normal functioning of both these organs are necessary for acid-base balance. A problem interfering with the function of either of them can lead to life-threatening acid-base imbalances. The heart, liver, and bladder have no role in acid-base balance. Although specific adrenal gland problems are indirectly associate with acid-base imbalances, they do not directly affect acid-base balance.

Question 7

7. Which statement most accurately describes the relationship between the hydrogen ion concentration and carbon dioxide concentration in extracellular fluids?

A. Because carbon dioxide is a gas and hydrogen ions are electrolytes, these two substances have no relationship in extra-cellular fluids.
B.
The concentrations of hydrogen ions and carbon dioxide are directly related, with
an increase or decrease in one always resulting in a corresponding increase or decrease in the other.
C.
Carbon dioxide buffers hydrogen ions, thus these two concentrations are inversely related to each other. The greater the carbon dioxide concentration, the fewer hydrogen ions present in that fluid.
D. Hydrogen ions and carbon dioxide ions exist in a balanced relationship as a result of their charges. The positively charged hydrogen ions are attracted to the negatively charged carbon dioxide ions, forming an electrically neutral substance.

Answer 7

B
Through the action of the carbonic anhydrase reaction, the concentration of hydrogen ions is directly related to the concentration of carbon dioxide in the blood. Any condition that increases the concentration of one also increases the concentration of the other. Carbon dioxide is not a buffer.

Question 8

8. Which statement about compensation for acid-base imbalance is accurate?

A. The respiratory system is less sensitive to acid-base changes.
B. The respiratory system can begin compensation within seconds to minutes.
C. The renal system is less powerful than the respiratory system.
D. The renal system is more sensitive to acid-base changes.

Answer 8

B
The healthy respiratory system can compensate for acid-base imbalances from other causes. It represents the second line of defense to prevent an imbalance and can begin to compensate within seconds to minutes after a change in hydrogen ion concentration (reflected as a corresponding change in carbon dioxide). The central chemoreceptors controlling rate and depth of ventilation are extremely sensitive to changes in carbon dioxide levels.

Question 9

9. Which condition or response is an example of physiologic compensation to maintain acid-base balance?
   A. Increasing rate and depth of respiration when running 2000 feet
   B. Increasing urine output when blood pressure increases during heavy exercise
   C. Drinking more fluids when spending an extended period of time in a dry environment
   D. Shifting body weight when pain occurs as a result of remaining in one position for too long

Answer 9

A
The respiratory system increases its activity by
“Blowing off” excess carbon dioxide that developed as a result of lactic acidosis occurring in skeletal muscle when blood flow and oxygenation were insufficient to meet the increased demand for oxygen (oxygen debt) created during increased skeletal muscle metabolism.

Question 10

10. which statements correctly apply to acid-base balance in the body? Select all that apply
    A.
    Renal mechanisms are stronger in regular. ing acid-base balance but slower to respond than respiratory mechanisms.
    B.
    The immediate binding of excess hydrogen ions occurs primarily in the red blood cells,
    C.
    Combined acidosis is less severe than either metabolic acidosis or respiratory acidosis alone.
    D.
    Respiratory acidosis is caused by a patent
    airway.
    E.
    Acid-base balance occurs through control of hydrogen ion production and elimination.
    F. Buffers are the third-line defense against acid-base imbalances in the body.

Answer 10

A, B, E
Acid-base balance is maintained by controlling the body’s hydrogen ion production with mechanisms to eliminate hydrogen ions at the same rate they are produced. Renal mechanisms for control of acid-base balance are the most powerful but are slow to start, usually requiring that an acid-base disturbance be present for at least 24 hours before becoming active. The first line of defense against acid-base changes are the buffers in the blood, other extracellular fluids, and inside cells. Red blood cells in particular can reduce excess hydrogen ions by having them enter the cells and then binding them to buffers and hemoglobin. Respiratory acidosis is caused by problems that interfere with effective ventilation. A patent airway never causes respiratory acidosis. When conditions that cause respiratory acidosis are present at the same time as conditions that cause metabolic acido-sis, the severity of the imbalance increases, not decreases.

Question 11

11. Which alteration in acid-base balance does the nurse expect to see as a compensatory response in a client who has a long-term severe respiratory impairment?
    A. Decreased arterial blood pH
    B. Increased arterial blood oxygen
    C. Increased arterial blood bicarbonate
    D. Decreased arterial blood carbon dioxide

Answer 11

C
Because kidneys regulate pH by controlling bicarbonate concentration and the lungs regulate pH by controlling carbon dioxide lose, a loss of one function can be at least partially compensated by the other function. When pulmonary function is decreased so that adequate amounts of carbon dioxide are not excreted, the pH drops, stimulating the kidneys to reabsorb more bicarbonate to balance the increased acid production.

Question 12

12. Which specific type of medication reported as taken daily by an older client will cause a nurse to assess for indications of an acid-base imbalance?
    A. Antilipidemics
    B. Hormonal therapy
    C. Diuretics
    D. Antidysrhythmics

Answer 12

C
Of all the drug categories listed, only the diuretics induce the excretion of specific electrolytes and hydrogen ions, leading to the development of acid-base imbalances.

Question 13

13. Which client does the nurse anticipate will have acidosis because of a decreased arterial bicarbonate level?
    A. Client with pancreatitis
    B. Client with hypoventilation
    C. Client who is vomiting
    D. Client with emphysema

Answer 13

A
The pancreas produces bicarbonate, which is a base. Pancreatitis inhibits this function resulting in underproduction of bicarbonate. This would lead to a relative acidosis. vomiting would cause loss of hydrogen ions and alkalosis. Emphysema would increase carbon dioxide and hydrogen ion production, as would hypoventilation.

Question 14

14. Which arterial blood gas (ABG) results would the nurse expect for a client admitted to the hospital for diabetic ketoacidosis? Select all that apply.
    A. pH 7.32
    B. PaCO, 50 mm Hg
    C. Bicarbonate 18 mEq/L (mmol/L)
    D. pH 7.46
    E. Bicarbonate 29 mEq/L (mmol/L)
    F. Pa0, 98 mm Hg

Answer 14

A,B,E,F
Diabetic ketoacidosis results from the excessive production of ketoacids as a byproduct of fat breakdown. These ketoacids release hydrogen ions which lower, not raise the pH. The excess hydrogen ions also increase the blood level of CO2 which is what stimulates deep and rapid respirations that try to decrease the hydrogen ion concentration. Bicarbonate is not lowered or increased because there has not been enough time for kidney compensation to start. Oxygen levels are normal because ventilation is not impaired.

Question 15

15. What type of acid-base problem does the nurse expect in a client who is being insufficiently mechanically ventilated for the past 4 hours and whose most recent arterial blood gas results include a pH of 7.29?
    A. Metabolic acidosis with an acid excess
    B. Metabolic acidosis with a base deficit
    C. Respiratory acidosis with an acid excess
    D. Respiratory acidosis with a base deficit

Answer 15

C
When a person being mechanically ventilated is insufficiently ventilated, respiratory acidosis occurs with retention of carbon dioxide. The retained carbon dioxide is converted to hydrogen ions resulting in an acid excess. Bases have neither been lost or retained in an acute respiratory acidosis. Insufficient ventilation does not cause any form of metabolic acidosis.

Question 16

16. What cause does the nurse expect to see for a client’s arterial pH of 7.28 after he has been NPO for 5 days and receiving only dextrose 5% in lactated Ringer’s solution (4 liters daily)?
    A. Acidosis in response to the presence of excessive ketoacids
    B. Acidosis in response to the presence of excessive lactic acid
    C. Alkalosis in response to the excessive loss of carbonic acid
    D. Alkalosis in response to the excessive loss of sulfuric acid

Answer 16

A
Clients who are NPO and receiving only crystalloid solutions (including glucose) are in a condition of starvation. Each liter of 5% dextrose contains only a little over 170 calories. Four liters daily provides approximately 700 calories, not nearly enough to support adult metabolic needs. These clients are breaking down body fat for fuel, which increases production of ketoacids.

Question 17

17. Which acid-base imbalance will the nurse expect in a client who has chronic kidney disease?
    A. Respiratory acidosis
    B. Metabolic acidosis
    C. Respiratory alkalosis
    D. Metabolic alkalosis

Answer 17

B
Clients with chronic kidney disease are unable to excrete sufficient hydrogen ions or to reabsorb sufficient bicarbonate to maintain acid-base balance. This results in a metabolic acidosis. Although an increased rate of ventilation may also occur, it is not great enough to cause a respiratory alkalosis.

Question 18

18. Which laboratory value indicates to the nurse that a client has acidosis as a result of a metabolic problem?
    A. PaCO, = 43 mm Hg
    B. HCO; - = 17 mEq/L (mmol/L)
    C. Lactate = 2.5 mmol/L
    D. pH = 7.32

Answer 18

B
Option D is incorrect because the question already states that the client has acidosis and is asking which laboratory value indicates the acidosis in metabolic in origin. The hallmark of a metabolic origin acidosis is a lower than normal bicarbonate level coupled with a normal carbon dioxide level and a low pH.

Question 19

19. Overdose of which drug or drug category could cause metabolic acidosis?
    A. Acetaminophen
    B. Antihistamines
    C. Antacids
    D. Aspirin

Answer 19

D
Although aspirin overdose initially causes a respiratory alkalosis by stimulating an increased respiratory rate, at the cellular level it results in a true metabolic acidosis that, untreated, can cause death. Antacid overdose can lead to alkalosis. Acetaminophen causes liver toxicity, not acidosis. Antihistamines are not associated with development of acidosis.

Question 20

20. For which client will the nurse remain most alert for the possibility to develop respiratory alkalosis?
    A. Client who is anxious and breathing rapidly
    B. Client who has multiple rib fractures
    C. Client receiving IV Ringer’s lactate
    D. Client who has diarrhea

Answer 20

A
Clients who hyperventilate can exhale excessive amounts of carbon dioxide which leads to a decreased blood level of free hydrogen ions and acidosis or respiratory origin. A client with multiple rib fractures may have poor gas exchange from shallow breathing because of pain and because the rib fractures may inhibit adequate chest expansion. Ringer’s lactate does not cause a respiratory problem. The client with diarrhea is at risk for metabolic acidosis from loss of bicarbonate ions in the stool.

Question 21

21. Which laboratory value will the nurse check immediately to prevent harm for a client with metabolic acidosis who now has tall, peaked T waves on his or her ECG?
    A. Serum glucose
    B. Serum sodium
    C. Serum potassium
    D. Serum magnesium

Answer 21

C
During acidosis, the body attempts to bring the pH closer to normal by moving free hydrogen ions into cells in exchange for potassium ions. This exchange can cause hyperkalemia, which can block electrical conduction through the heart and cause severe bradycardia and even cardiac arrest. A hallmark of hyperkalemia is tall, peaked T waves on the ECG. Although other electrolytes are affected to some degree, the most important one to assess is the serum potassium level.

Question 22

22. Which clients would the nurse assess for problems of inadequate chest expansion that may increase the risk for respiratory acidosis? Select all that apply.
    A. 87-year old with osteoporosis and severe kyphoscoliosis
    B. 27-year-old client in the first trimester of pregnancy
    C. 44-year-old severely obese client on prolonged bedrest
    D. 67-year-old 2 days postoperative from arthroscopic surgery
    E. 37-year-old with ascites
    F. 56-year-old with end-stage emphysema

Answer 22

A, C, E, F
Severe kyphoscoliosis, severe obesity, ascites, and emphysema all make chest expansion more difficult and can lead to respiratory acidosis. Arthroscopic surgery and early pregnancy do not impinge on the chest cavity or interfere with chest expansion.

Question 23

23. Which laboratory values indicate to the nurse that a client’s acid-base imbalance is specifically a respiratory acidosis? Select all that apply.
    A. pH 7.31
    B. PaCO, 58 mm Hg
    C. Bicarbonate 17 mEg/L (mmol/L)
    D. Pa0, 75 mm Hg
    E. Serum potassium 5.5 mEg/L (mmol/I)
    F. PaCO, 31 mm Hg

Answer 23

B, D
The hallmarks of a respiratory acidosis are high PaCO2 and low PaO2 coupled with a low pH. However, a low pH is also associated with a metabolic acidosis and is not specific to a respiratory acidosis. The elevated potassium level is associated with both metabolic and respiratory acidosis. The low bicarbonate level is associated with a metabolic acidossis. The low PaCo2 is associated with respiratory alkalosis, not with acidosis.

Question 24

24.Which signs and symptoms would the nurse expect to find in a client with severe metabolic acidosis? Select all that apply.
A. Kussmaul respirations
B. Increased urine output
C. Warm, flushed skin
D. Skin pale to cyanotic
E. Elevated PaCO,
F. Decreased bicarbonate

Answer 24

A, C, F
Regardless of the cause of a severe metabolic acidosis, the greatly increased hydrogen ion concentration results in high CO2 levels (through the carbonic anhydrase reaction) that trigger the central nervous system to increase the rate and depth of breathing (Kussmaul respirations). These deep and rapid breaths help “blow off” the excessive CO2 and bring down the hydrogen ion level. The high CO2 level causes widespread vasodilation, which results in warm, flushed, and dry skin. Blood pressure is low, which decreases urine output. Bicarbonate is decreased either as a cause of the acidosis or because it is binding to hydrogen ions forming carbonic acid to help buffer the low pH.

Question 25

Which findings on lower limb assessment indi-
cates to the nurse that the client has acidosis?
Select all that apply.
A. No change from baseline
B. Bilateral weakness
C. Muscle twitching without weakness
D. Weakness on the dominant side
E. Hypoactive patellar reflex
F. Tetany of the great toe on the left foot

Answer 25

B, E
Skeletal muscle changes occur in acidosis because of the accompanying hyperkalemia.
Muscles are weak and deep tendon reflexes, including the patellar reflex, are hypoactive. In the lower limbs, the muscle weakness is bilateral and can progress to paralysis.

Question 26

26. Which client conditions does the nurse assess for as a cause of the underproduction or overe-limination of bicarbonate? Select all that apply.
    A. Heavy exercise
    B. Kidney failure
    C. Liver failure
    D. Seizure activity
    E. Dehydration
    F. Diarrhea

Answer 26

B, C, E, F
The kidney, pancreas, and liver are responsible for much of the body’s production of bicarbon-ate. Any problem with these organs interferes with its production. In dehydration, bicarbonate may continue to be produced but does not leave the producing organ. With diarrhea, bicarbonate is lost from the body.

Question 27

27. Which arterial blood gas changes indicates to the nurse that a client may have respiratory alkalosis?
    A. High pH; normal bicarbonate; low Pa02
    B. High pH; normal bicarbonate; low PaCO2
    C. High pH; high bicarbonate; high Pa02
    D. High pH; low bicarbonate; high PaCO,

Answer 27

B
The hallmarks of respiratory alkalosis are a pH above normal coupled with a normal bicarbonate level and a low PaCO,. The client’s gas exchange is unimpaired but more rapid, leading to an excessive loss of CO2. Because gas exchange is unimpaired, oxygen levels are normal and cannot go higher on normal atmospheric air.

Question 28

28. Which alterations in acid-base balance does the nurse expect to see in a client who has acute pancreatitis with severe pain and is hyperventi-lating? Select all that apply.
    A. Overproduction of hydrogen ions
    B. Metabolic acidosis
    C. Low or normal PaCO,
    D. Underproduction of bicarbonate
    E. Metabolic alkalosis
    E. Respiratory acidosis

Answer 28

B, C. D
The pancreas is an important producer of bicar-bonate. With pancreatitis, bicarbonate is under-produced, leading to a relative metabolic acidosis (hydrogen ion production is normal, not excessive). The PaCO, can be normal because gas exchange is not impaired and may be lower than normal because the client is hyperventilating as a result of the severe pain.

Question 29

29. Which statement made by the to the nurse that an alkaline condition may
    client suggests
    present?
    A. “I am more and more tired and can’t concentrate.”
    B. “I have tingling in my fingers and toes”
    C. “My feet and ankles are swollen.”
    D. “My knee joints ache”

Answer 29

A condition resulting in alkalosis usually also
causes hypocalcemia, which increases the sensitivity of excitable membranes, often seen as tingling of the fingers, toes, and around the mouth. Edema and joint pain are not indicators of an acid-base balance problem. With increased nerve sensitivity, tiredness and difficulty concentrating are not common with alkalosis.

Question 30

30. With which client will the nurse remain most alert for respiratory alkalosis?
    A. Hypoxic client
    B. Morbidly obese client
    C. Client with a tight body cast
    D. Fearful client having a panic attack

Answer 30

D
Hypoxia is associated with respiratory acidosis.
Morbid obesity and a tight body cast can restrict
Chest movements and result in respiratory acidosis. Clients in a panic attack tend to hyperventilate, blowing off excessive amounts of carbon dioxide, leading to respiratory alkalosis.

Question 31

Which type(s) of electrolyte imbalance does the nurse expect to see in a client with metabolic alkalosis? Select all that apply.
A. Hyperkalemia
B. Hypokalemia
C. Hypercalcemia
D. Hypocalcemia
E. Hypernatremia
F. Hyponatremia

Answer 31

B, D
Alkalosis of any type causes hypokalemia as a compensatory response. Hydrogen ions move out of cells, especially red blood cells, in exchange for potassium from the blood moving into the cells in order to maintain electroneutrality. A rising blood pH promotes ionized calcium to bind to plasma proteins, decreasing the amount of ionized (free calcium) ions in the blood, resulting in hypocalcemia.

Question 32

32. Which client ABG results would the nurse interpret as metabolic alkalosis?
    A. pH 7.30, PaCO, 66, bicarbonate 38,
    Pa0, 70
    B. pH 7.38, PaCO2 36, bicarbonate 15,
    Pa0, 95
    C. pH 7.48, PaCO, 24, bicarbonate 20,
    Pa0, 95
    D. pH 7.50, PaCO, 45, bicarbonate 36,
    Pa0, 95

Answer 32

D
Alkalosis has a pH above 7.45, which would
make options A (partially compensated respiratory acidosis) and B (metabolic acidosis) incorrect. Metabolic alkalosis has normal carbon dioxide and oxygen levels because breathing is not affected. Elevated bicarbonate levels (or acid losses) cause metabolic alkalosis.

Question 33

33. Which client will the nurse observe most closely for development of a base excess metabolic alkalosis?
    A. 26-year-old who received a massive blood transfusion
    B. 36-year-old who is having nasogastric
    suction
    C. 56-year-old who has vomited for 2 days
    D. 76-year-old taking thiazide diuretics

Answer 33

A
Base excesses are caused by excessive intake of bicarbonates, carbonates, acetates, and citrates.
Citrates are products used to preserve blood components for transfusion therapy. A massive blood transfusion would increase citrate levels and cause a base excess acidosis. Development of base excess alkalosis is not age-related. Thiazide diuretics, nasogastric suctioning, and prolonged vomiting lead to acid-deficit metabolic alkalosis.

Question 34

34. Which alteration will the nurse expect in client who has taken antacids for the past 3 days to relieve “heartburn?”
    A. Respiratory alkalosis (acid deficit)
    B. Metabolic alkalosis (acid deficit)
    C. Respiratory alkalosis (base excess)
    D. Metabolic alkalosis (base excess)

Answer 34

D
Antacids buffer the hydrochloric acid in the stomach, which causes heartburn, by adding more base, usually in the form of bicarbonate. Thus, excessive antacid use leads to a base-excess metabolic alkalosis.

Question 35

35. What would the nurse expect to see first as compensation in a client who has a decreased amount of hydrogen ions and a decreased amount of carbon dioxide in the body to restore acid-base balance?
    A. Decreased rate and depth of respirations
    B. Decreased renal absorption of hydrogen ions
    C. Increased rate and depth of respirations
    D. Decreased renal excretion of bicarbonate

Answer 35

A
The respiratory compensation for acid-base derangements is the second line of defense (buffers in body fluids are first) but begins within minutes of changes. For decreased carbon dioxide and hydrogen ion levels, respiratory compensation would be to decrease the rate and depth of respiration so that more
car-bon dioxide would be retained, which would also increase the hydrogen ion concentration. Renal compensation takes much longer (at least 24 hours) to initiate.

Question 36

Which acid-base and electrolyte changes would
the nurse monitor for in a client who has had diarrhea for the past 2 days? Select all that apply.

A. Over elimination of bicarbonate
B. Respiratory alkalosis
C. Metabolic acidosis
D. Under elimination of hydrogen ions
E. Overproduction of hydrogen ions
F. Hyperkalemia
G. Hyponatremia

Answer 36

A, C, F
Bicarbonate is a base that is lost with excessive diarrhea leading to a base-deficit metabolic aci-dosis. In addition, bicarbonate that is produced may not get into body fluids if the diarrhea was severe enough to cause dehydration. The acidosis would cause hydrogen ions to move into cells in exchange for potassium moving from the cells into the extracellular fluid to maintain electroneutrality, resulting in hyperkalemia.