[Osborn] chapter 19 Learning Outcomes [Number and Title] Learning Outcome 1 Describe the role of hydrogen ions in the determination of plasma pH. Learning Outcome 2 Compare and contrast the processes that produce respiratory and metabolic acids in the body and the processes by which they are eliminated. Learning Outcome 3 Calculate minute ventilation and explain the effect of minute alveolar ventilation on acid–base balance. Learning Outcome 4 Evaluate the process of respiratory compensation for a metabolic abnormality. Learning Outcome 5 Discuss the renal handling of hydrogen ion and bicarbonate. Learning Outcome 6 Discuss a systematic stepwise process for the interpretation of the arterial blood gas values related to acid–base balance. Learning Outcome 7 Relate the major causes, pathophysiology, signs, symptoms, consequences, and medical management for respiratory acidosis and alkalosis and metabolic acidosis and alkalosis. Learning Outcome 8 Describe the nursing assessment used in the assessment of acid–base abnormalities. Learning Outcome 9 Describe nursing actions to alleviate the symptoms of acid–base abnormalities. Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for Practice Copyright 2010 by Pearson Education, Inc.
Transcript
[Osborn] chapter 19
Learning Outcomes [Number and Title] Learning Outcome 1 Describe the role of hydrogen ions in the determination of
plasma pH.Learning Outcome 2 Compare and contrast the processes that produce respiratory
and metabolic acids in the body and the processes by which they are eliminated.
Learning Outcome 3 Calculate minute ventilation and explain the effect of minute alveolar ventilation on acid–base balance.
Learning Outcome 4 Evaluate the process of respiratory compensation for a metabolic abnormality.
Learning Outcome 5 Discuss the renal handling of hydrogen ion and bicarbonate.Learning Outcome 6 Discuss a systematic stepwise process for the interpretation of
the arterial blood gas values related to acid–base balance.Learning Outcome 7 Relate the major causes, pathophysiology, signs, symptoms,
consequences, and medical management for respiratory acidosis and alkalosis and metabolic acidosis and alkalosis.
Learning Outcome 8 Describe the nursing assessment used in the assessment of acid–base abnormalities.
Learning Outcome 9 Describe nursing actions to alleviate the symptoms of acid–base abnormalities.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
1. Which is the best description of the role of hydrogen ions in the body?1. Changes in hydrogen ion concentration can cause denaturing of proteins. 2. The hydrogen ion is a large ion particle that has a significant effect on
physiologic functioning.3. The hydrogen ion is not very reactive until it combines with oxygen.4. The hydrogen ion is available in large concentrations in the body and has an
effect on many of the body’s functions.
Correct answer: Changes in hydrogen ion concentration can cause denaturing of proteins.
Rationale: Changes in hydrogen ion concentration can cause denaturing of proteins. The hydrogen ion is a small ion particle that is very reactive. It is available in small concentrations in the body.
Cognitive Level: ComprehendingNursing Process: EvaluationClient Need: Health Promotion and MaintenanceLO: 1
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
2. The nurse is caring for a patient admitted with diabetic ketoacidosis. The nurse realizes that since the patient is:
1. Acidotic, the hydrogen ion concentration is high.2. Alkalotic, the hydrogen ion concentration is high.3. Acidotic, the hydrogen ion concentration is low.4. Alkalotic, the hydrogen ion concentration is low.
Correct answer: Acidotic, the hydrogen ion concentration is high.
Rationale: Since the patient is acidotic, the hydrogen ion concentration is high. As the hydrogen ion concentration increases, the pH decreases.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
3. The nurse is caring for a client with renal failure whose blood gas reflects a pH of 7.21. Which of the following is correct regarding the hydrogen ion and acid−base balance?
1. As the hydrogen ion concentration increases, the pH decreases.2. As the hydrogen ion concentration increases, the pH increases.3. As the hydrogen ion concentration decreases, the pH decreases.4. When present in proper concentration, the hydrogen ion maintains the normal
pH of the body between 6.8 and 7.8.
Correct Answer: As the hydrogen ion concentration increases, the pH decreases.
Rationale: The pH reflects the negative logarithm of the hydrogen ion concentration; therefore, as the hydrogen ion concentration increases, the pH decreases. As the hydrogen ion decreases, the pH increases. The normal pH is 7.35 to 7.45.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
4. The nurse is verbalizing her new knowledge of respiratory and metabolic acids and bases. Which statement indicates that the nurse needs more information?
1. “Body metabolism produces lactic acids, which are constantly eliminated in the lungs.”
2. “Carbon dioxide is a potential acid that is excreted through the lungs.”3. “When hydrogen ions combine with carbon dioxide, carbonic acid is
produced.”4. “Sodium bicarbonate buffers the blood by removing hydrogen ions from the
blood.”
Correct answer: “Body metabolism produces lactic acids, which are constantly eliminated in the lungs.”
Rationale: Body metabolism produces carbon dioxide that is eliminated through the lungs. Lactic acids occur during anaerobic metabolism and are eliminated through the kidneys and the liver. The other answer choices are correct and indicate that the new nurse understands respiratory and metabolic acids and bases.
Cognitive Level: EvaluatingNursing Process: EvaluationClient Need: Health Promotion and MaintenanceLO: 2
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
5. The patient is found to be in respiratory acidosis. Which metabolic processes are in place during respiratory acidosis?1. The pH is low, carbon dioxide is high, and the kidneys excrete hydrogen ions
and conserve bicarbonate.2. The pH is high, carbon dioxide is high, and the kidneys excrete hydrogen ions
and conserve bicarbonate.3. The pH is low, carbon dioxide is low, and the kidneys excrete hydrogen ions
and conserve bicarbonate.4. The pH is low, carbon dioxide is high, and the kidneys conserve hydrogen
ions and excrete bicarbonate.
Correct answer: The pH is low, carbon dioxide is high, and the kidneys excrete hydrogen ions and conserve bicarbonate.
Rationale: A low pH defines acidosis. Carbon dioxide is retained in the lungs in respiratory acidosis and is therefore high. The kidneys excrete hydrogen ions in an attempt to decrease further acid production, and conserve bicarbonate in an attempt to buffer the acidosis.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
6. When analyzing an arterial blood gas report of a client with COPD and respiratory acidosis, the nurse anticipates that compensation will develop through which of the following mechanisms?
1. The kidneys retain bicarbonate.2. The kidneys excrete bicarbonate.3. The lungs will retain carbon dioxide.4. The lungs will excrete carbon dioxide.
Correct Answer: The kidneys retain bicarbonate.
Rationale: The kidneys will compensate for a respiratory disorder by retaining bicarbonate. Excreting bicarbonate causes acidosis to develop. Retaining carbon dioxide causes respiratory acidosis. Excreting carbon dioxide causes respiratory alkalosis.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
7. The nurse is assessing the minute volume of a client. If the client’s tidal volume is normal and the respiratory rate is 15 breaths per minute, calculate the client’s minute volume.
Rationale: The minute volume is calculated by multiplying the tidal volume, normally 500 ml/breath, and the respiratory rate—in this example 500 15 = 7500 ml/minute or 7.5 L/minute.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
8. When calculating the alveolar volume (the volume of air that contributes to gas exchange in the lungs), what is subtracted from the tidal volume?1. The dead space2. The respiratory rate3. Minute ventilation 4. The PaCO2
Correct answer: The dead space
Rationale: The tidal volume minus the anatomic dead space equals the alveolar volume. The alveolar volume is the volume of air that contributes to gas exchange in the lungs. The alveolar volume decreases in diseases such as chronic bronchitis and COPD.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
9. The nurse receives the result of a patient’s pulmonary functions tests. The respiratory rate is 14 breaths per minute and the tidal volume is 540 ml. The nurse correctly calculates the client’s minute ventilation as:
Rationale: Minute ventilation is calculated by multiplying the respiratory rate times the tidal volume: 14 540 = 7560. The rates of 14, 540, and 32,400 ml/minute are not correct.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
10. The nurse is developing the plan of care for a patient diagnosed with pneumonia. In order to determine the correct nursing diagnosis, the nurse knows that the respiratory system regulates plasma pH changes by releasing or retaining:
Rationale: The respiratory system regulates plasma pH changes by releasing or retaining carbon dioxide (CO2), a potential acid. Sodium bicarbonate, hydrogen ions, and H2CO3 are not released or retained in this process.
Cognitive Level: AnalyzingNursing Process: DiagnosisClient Need: Health Promotion and MaintenanceLO: 4
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
11. The patient is admitted with diabetic ketoacidosis. The nurse would expect to find respiratory compensation through the following assessment:1. Rapid respiratory rate.2. Diminished lung sounds.3. A dry cough.4. Wet lung sounds; rhonchi.
Correct answer: Rapid respiratory rate.
Rationale: The nurse would expect to find a rapid respiratory rate. This has the effect of decreasing or “blowing off” carbon dioxide, which is a potential acid, and is a compensation for metabolic acidosis. Diminished lung sounds and wet lung sounds or rhonchi both occur as a result of fluid in the lungs. A dry cough is not commonly associated with diabetic ketoacidosis.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
12. The nurse is caring for a client with diabetic ketoacidosis (DKA) who presents with polyuria, abdominal pain, vomiting, and flushed skin. Which of the following clinical manifestations suggests compensation for the acid−base disorder?
1. The patient exhibits a respiratory rate of 28 with deep inspirations.2. The patient demonstrates shallow respirations and decreased excursion.3. The patient has a urine output of 20 ml for the last hour.4. The patient presents with vomiting.
Correct Answer: The patient exhibits a respiratory rate of 28 with deep inspirations.
Rationale: The client responds to DKA, a type of metabolic acidosis, with increased rate and depth of breathing known as Kussmaul breathing. This compensatory mechanism causes the client to “blow off” or exhale CO2, a respiratory acid, to increase the pH in an attempt to return the client to normal acid−base status. Shallow breathing with decreased excursion will cause respiratory acidosis, worsening the situation. Clients with DKA may have dehydration and decreased renal perfusion secondary to polyuria, but this is part of the syndrome, not compensation. Vomiting is a symptom of DKA, not a compensatory mechanism.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
13. The nurse is developing a plan of care for a patient with Crohn’s disease. In order to determine the correct nursing diagnosis, the nurse knows that the kidneys regulate plasma pH changes by secreting:
1. H+ ions.2. K+ ions.3. Na+ ions.4. NaCO3 ions.
Correct answer: H+ ions.
Rationale: The kidneys regulate plasma pH changes by secreting hydrogen ions. The kidneys also regulate and restore or reclaim sodium bicarbonate ions (NaCO3). Although the kidneys also regulate sodium and potassium, these electrolytes are not the primary factors in controlling plasma pH.
Cognitive Level: AnalyzingNursing Process: DiagnosisClient Need: Health Promotion and MaintenanceLO: 5
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
14. The patient is admitted with vomiting and diarrhea. To plan the care for this patient, the nurse must know that metabolic compensation occurs when the kidneys reclaim or restore:1. Bicarbonate.2. Ketones.3. Hydrogen.4. Water.
Correct answer: Bicarbonate.
Rationale: The kidneys regulate and restore or reclaim sodium bicarbonate ions (NaCO3) to regulate plasma pH. The kidneys regulate plasma pH changes by secreting hydrogen ions. Ketones are secreted by the kidneys, and this is an indication that fats are being metabolized for energy rather than carbohydrates, but this is not the main mechanism of plasma pH regulation. The kidneys would conserve water due to dehydration rather than regulation of pH.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
15. When caring for a patient with end-stage COPD, the nurse recognizes compensation for the acid−base abnormality is present when which of the following occurs?
1. The kidney retains bicarbonate in excess of normal.2. The pCO2 is less than 35 mm Hg.3. The oxygenation improves.4. Hypoventilation occurs with a pCO2 greater than 45 mm HG.
Correct Answer: The kidney retains bicarbonate in excess of normal.
Rationale: The client with COPD cannot efficiently eliminate CO2, resulting in respiratory acidosis, manifested by a pCO2 greater than 45 mm HG. To compensate for this, bicarbonate is retained by the kidney. Oxygenation is typically poor in the client with COPD. While clients with COPD hypoventilate, this is a manifestation of the underlying disorder, not the compensation.
Rationale: Determining whether the pH is normal, low (acidic), or high (alkaloid) is the first step to interpretation of the arterial blood gases. Next, the respiratory (carbon dioxide) and the metabolic components (bicarbonate and base excess) are examined.
Rationale: If the problem is respiratory in origin, then the pH and the carbon dioxide will move in opposite directions. With a metabolic problem, the pH and bicarbonate move in the same direction. The respiratory problem could be either acidosis or alkalosis, depending on the blood gas values.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
18. The nurse is caring for a client with renal failure. Which of the following does the nurse recognize as demonstrating compensation for the acid–base disturbance found in clients with renal failure?
1. The client will breathe more rapidly to eliminate carbon dioxide.2. The client will retain bicarbonate in excess of normal.3. The pH will decrease from the present value.4. The client will demonstrate improved oxygenation.
Correct Answer: The client will breathe more rapidly to eliminate carbon dioxide.
Rationale: In metabolic acidosis, compensation is accomplished through increased ventilation or “blowing off” CO2. This raises the pH by eliminating the volatile respiratory acid and compensates for the acidosis. Because compensation must be performed by the system other than the affected system, the client cannot retain bicarbonate; the manifestation of metabolic acidosis of renal failure is a lower-than-normal bicarbonate value. Metabolic acidosis of renal failure causes a low pH; this is the manifestation of the disease process, not the compensation. Oxygenation disturbance is not part of the acid–base status of the client with renal failure.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
19. The nurse is admitting a patient with COPD and pneumonia. The ABG findings include: pH 7.31, PaO2 65, PaCO2 75, and HCO3 22. The nurse immediately gives the patient oxygen via a mask. What complication would the nurse anticipate?
1. Respiratory arrest2. Respiratory acidosis3. Hyperventilation4. Nausea and vomiting
Correct answer: Respiratory arrest
Rationale: Respiratory arrest (the opposite of hyperventilation) can be anticipated. The patient with COPD has chronic hypercarbia. As the carbon dioxide levels decrease and the oxygen levels increase with the administration of oxygen, the patient is at high risk for respiratory arrest. Respiratory acidosis is the correct interpretation of the current blood gases, but not a complication. Nausea and vomiting are unrelated to this scenario.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
20. The nurse is admitting a patient with acute exacerbation of colitis. The ABG findings include: pH 7.33, PaO2 95, PaCO2 43, and HCO3 17. The nurse would anticipate which initial intervention to correct this problem?1. Administration of isotonic fluids2. Administration of oxygen3. Administration of potassium4. Administration of bicarbonate
Correct answer: Administration of isotonic fluids
Rationale: The nurse would expect initial management to include administration of fluids, as this patient is in metabolic acidosis related to gastrointestinal fluid and potassium loss due to colitis. Once the patient is hydrated and renal function is assessed, the patient would be given potassium replacement. Oxygen levels are normal and do not need correction. Bicarbonate administration is not common unless the pH is less than 7.0 or the metabolic acidosis does not correct as the original problem is corrected.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
21. When caring for a group of patients, which of the following individuals is at risk for metabolic alkalosis?
1. A patient with bulimia2. A patient undergoing dialysis3. A patient with a venous stasis ulcer4. A patient with COPD
Correct Answer: A patient with bulimia
Rationale: Metabolic alkalosis is caused by vomiting, diuretic therapy, or NG suction, among others. A bulimic client may engage in vomiting or indiscriminate use of diuretics. A client undergoing dialysis has kidney failure, which causes metabolic acidosis. A venous stasis ulcer does not result in an acid−base disorder. The client with COPD typically has hypercapnea and respiratory acidosis.
Rationale: The pH is high and the PaCO2 leans to the opposite direction of the pH, indicating the presence of respiratory alkalosis. This interpretation is confirmed because the HCO3 is normal.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
23. The nurse is assessing a patient for the presence of metabolic acidosis. In addition to the arterial blood gases, the nurse should also assess:1. Na+ – (Cl- + HCO3).2. K+ – (Na++ HCO3).3. The creatinine and BUN.4. All electrolytes and blood glucose.
Correct answer: Na+ – (Cl- + HCO3).
Rationale: In addition to the arterial blood gases, metabolic acidosis can be assessed using the result of the anion gap. The anion gap is calculated using the following formula: Sodium – (Chloride + Bicarbonate). The anion gap will be high in metabolic acidosis. The creatinine and BUN would reflect renal function, but not specifically metabolic acidosis. Electrolytes and blood glucose would also be important assessments, but are too general to reflect metabolic acidosis.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
24. When caring for a client with respiratory alkalosis, which of the following assessments will assist the nurse in determining the underlying cause of the acid–base disturbance?
1. Pulse oximetry2. Recent use of narcotics3. Peripheral pulses4. Presence of a facial droop
Correct Answer: Pulse oximetry
Rationale: Hypoxemia, detected by pulse oximetry, is a typical cause of respiratory alkalosis. Narcotic use will depress respiratory drive, causing hypercapnea and respiratory acidosis. Peripheral pulse and facial droop are not symptoms of acid−base disturbances.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
25. The nurse is planning education for a patient who is recovering from diabetic ketoacidosis. What is the most important first step?
1. Assessing the patient’s management of diabetes prior to this event2. Assessing patterns of blood glucose results during the hospital stay3. Printing information on the management of diabetes during sick days4. Printing information on how to count carbohydrates and calculate insulin
needs
Correct answer: Assessing the patient’s management of diabetes prior to this event
Rationale: Before printing information or planning educational topics, the nurse needs to assess the patient’s individual management of diabetes and the patient’s knowledge of the condition. Glucose results during diabetic ketoacidosis are not an accurate assessment of overall management of the disease. A better test to measure average blood sugar over the last 3 months is the hemoglobin A1C.
Cognitive Level: EvaluatingNursing Process: PlanningClient Need: Health Promotion and MaintenanceLO: 9
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
26. The nurse is caring for a patient who is anxious and dizzy following a traumatic experience. The ABG findings include: pH 7.48, PaO2 110, PaCO2 25, and HCO3 24. The nurse would anticipate which initial intervention to correct this problem?
1. Encourage the patient to breathe in and out slowly into a paper bag. 2. Immediately administer oxygen via a mask and monitor oxygen saturation.3. Prepare to start intravenous fluid bolus using isotonic fluids.4. Anticipate the administration of sodium bicarbonate via the IV route.
Correct Answer: Encourage the patient to breathe in and out slowly into a paper bag.
Rationale: This patient is exhibiting signs of psychological hyperventilation; blood gases confirm this, showing respiratory alkalosis. Breathing into a paper bag will help the patient to retain carbon dioxide and lower oxygen levels to normal, correcting the cause of the problem. The oxygen levels are high, so oxygen is not indicated, and would exacerbate the problem if given. IV fluids would not be the initial intervention. Not enough information is given to determine the need for IV fluids. Bicarbonate would be contraindicated, as the pH is already high.
Osborn, et al., Test Item File for Medical-Surgical Nursing: Preparation for PracticeCopyright 2010 by Pearson Education, Inc.
27. The nurse is caring for a client who has postoperative vomiting. Arterial blood gas results are: pH 7.47, pCO2 40, HCO3 33, pO2 84. Which of the following interventions should the nurse include in the plan of care to restore acid−base balance?
1. Administer an antiemetic agent 2. Administer naloxone to antagonize narcotic analgesic3. Encourage the patient to use an incentive spirometer4. Administer oxygen at 2 liters by nasal cannula
Correct Answer: Administer an antiemetic agent
Rationale: The first step is to interpret the pH, which reflects alkalosis because it is greater than 7.45. The next rule is to interpret the pCO2 which is normal and therefore not a cause of acid−base imbalance. The metabolic component, HCO3, is alkaline—greater than 26 meQ/L. Vomiting results in metabolic alkalosis, the disturbance reflected in the blood gas in the scenario; therefore an antiemetic agent will help resolve the problem. Administering naloxone will antagonize narcotic analgesics, which cause respiratory acidosis. Incentive spirometry would improve ventilation; the client has a normal pCO2. There is no indication the client has hypoxemia requiring supplemental oxygen.
