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Chapter 8-b- Disorders of Acid-Base Balance
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1.
A male patient with a history of heavy alcohol use has been admitted to hospital for malnutrition and suspected pancreatitis. The patient's diagnostic workup suggests alcoholic ketoacidosis as a component of his current health problems. He is somewhat familiar with the effect that drinking has had on his nutrition and pancreas but is wholly unfamiliar with the significance of acid?base balance. How best could his care provider explain the concept to him?
A)
?The chemical processes that take place throughout your body are thrown off very easily when your body is too acidic or not acidic enough.
B)
?The multitude of chemical reactions that take place in your body depend on your body fluids being slightly acidic.?
C)
?The healthy function of your kidneys and your lungs requires a specific level of pH in your body.?
D)
?Your body is highly dependent on what food and fluid you consume to keep itself at a functioning level of slight nonacidity.?
Ans:
A
Feedback:
Metabolic activity is highly contingent on a narrow range of pH. Normal pH is slightly basic, not acidic, and appropriate pH is maintained by the lungs and kidneys, not vice versa. The action of the respiratory and renal systems, not particular food or fluid intake, has the most salient effect on the acid?base balance.
2.
When explaining how carbon dioxide combines with water to form carbonic acid as part of acid?base lecture, the faculty instructor emphasized that which enzyme is needed as a catalyst for this reaction?
A)
Carbonic anhydrase
B)
Phenylalanie hdroxylase
C)
Hydrolases
D)
Trypsin
Ans:
A
Feedback:
Although CO2 is a gas and not an acid, a small percentage of the gas combines with water to form H2CO3. The reaction that generates H2CO3 from CO2 and water is catalyzed by an enzyme called carbonic anhydrase.
3.
A 31-year-old client with a diagnosis of end-stage liver failure has been admitted to the intensive care unit of a hospital. Arterial blood sampling indicates that the man has an acid?base imbalance. Which of the following situations is most likely to result in an inappropriate pH?
A)
Conservation or formation of new HCO3? by the kidneys
B)
Low albumin and plasma globulin levels
C)
Transcompartmental exchange of H+ and potassium ions
D)
Renal excretion of HCO3? in the presence of excess base
Ans:
B
Feedback:
Albumin and plasma globulins are key protein buffers in the vascular compartment; consequently, a low albumin level, as is common in liver failure, is apt to result in acid?base imbalances. Answer choices A, C, and D all convey normal physiological processes that help to maintain pH.
4.
A patient with ESRD comes into the emergency department in severe acidosis. The nurse notes that the respiratory rate is 36 breaths/minute. The nurse understands the pathophysiology of this response and explains to the student nurse that the patient's
A)
anxiety level is high, and the body is trying to release endorphins.
B)
chemoreceptors in the carotid and aortic bodies have noticed the pH change and altered the ventilator rate.
C)
kidneys are not able to buffer the acid and require the help from the lungs.
D)
lungs are trying to excrete excess hydrogen.
Ans:
B
Feedback:
The second line of defense against acid?base disturbances is the control of extracellular CO2 by the lungs. Blood PCO2 and pH are important regulators of ventilation. Chemoreceptors in the brain stem and the peripheral chemoreceptors in the carotid and aortic bodies sense changes in PCO2 and pH and alter the ventilatory rate.
5.
Place the following stages of the hydrogen ion elimination and bicarbonate conservation in the proximal tubules of the nephrons in the ascending chronological order. Use all the options.
A) CO2 and H2O are produced.
B) H+ is secreting into the tubular fluid.
C) Carbonic acid is produced.
D) H+ combines with filtered HCO3?.
Ans:
B, D, C, A
Feedback:
Renal regulation of pH involves the secretion of hydrogen ions into the tubular fluid, the combining of hydrogen ions with bicarbonate yielding carbonic acid, followed by the decomposition of carbonic acid into carbon dioxide and water.
6.
Following several days in an acidotic state, a hospital patient has returned to desired pH. Which of the following processes could have contributed to the resolution of the patient's health problem?
A)
Exchange of Na+ and H+ ions
B)
Selective renal secretion and reabsorption of CO2
C)
The phosphate and ammonia buffer systems in the renal tubules
D)
Excretion of HCO3? by the kidneys
Ans:
C
Feedback:
The phosphate and ammonia buffer systems are secondary, but important, processes that contribute to the maintenance of appropriate pH. The kidneys must reabsorb nearly all the body's stores of HCO3? to maintain homeostasis, and they are not involved in CO2 control. Hydrogen?potassium exchange, not hydrogen?sodium exchange, is a component of acid?base control.
7.
When trying to explain the role of potassium and hydrogen related to acid?base balance, which of the following statements is accurate?
A)
Hypokalemia stimulates H+ secretion.
B)
Hyperkalemia will cause the reabsorption of HCO3.
C)
Acidosis causes an increase in K+ elimination.
D)
Alkalosis tends to increase H+ elimination.
Ans:
A
Feedback:
Hypokalemia is a potent stimulus for H+ secretion and HCO3 reabsorption. Acidosis tends to increase H+ elimination and decrease K+ elimination, with a resultant increase in plasma potassium levels, whereas alkalosis tends to decrease H+ elimination and increase K+ elimination, with a resultant decrease in plasma K+ levels.
8.
A client with poorly controlled diabetes mellitus presents to the emergency department with suspected ketoacidosis. Which of the following diagnostic results would most likely confirm this diagnosis?
A)
Low O2 levels, increased anion gap, base excess
B)
High ammonia levels, decreased anion gap, high potassium
C)
Increased anion gap, base deficit
D)
Decreased anion gap, decreased urine ammonium level
Ans:
C
Feedback:
Increased CO2 levels, an increased anion gap, and a base deficit are all associated with an acidotic state. Base excess, low oxygen, high potassium, high ammonia, and decreased anion gap would not suggest acidosis.
9.
A patient who has just had her first postoperative dinner out to celebrate her recovery from an intestinal bypass is brought to the emergency room by her spouse. He reports that the patient seems disoriented and is slurring her words. The patient did not have any alcohol with her pasta dinner. Which of the following might be the cause of her symptoms?
A)
Ketoacidosis
B)
Lactic acidosis
C)
Hypercapnia
D)
Hypothalemia
Ans:
B
Feedback:
A unique form of lactic acidosis, called D-lactic acidosis, can occur in persons with intestinal disorders that involve the generation and absorption of D-lactic acid. D-lactic acidosis can occur in persons with jejunoileal bypass, in which there is impaired reabsorption of carbohydrate in the small intestine. Persons with D-lactic acidosis experience episodic periods of metabolic acidosis often brought on by eating a meal high in carbohydrates. Manifestations include confusion, cerebellar ataxia, slurred speech, and loss of memory. They may complain of feeling (or may appear) intoxicated.
10.
The nurse is caring for a patient with ketoacidosis, who is complaining of increasing lethargy and occasional confusion following several weeks of rigid adherence to a carbohydrate-free diet. The nurse understands which of the following phenomena is most likely occurring?
A)
High-fat, low-carbohydrate dietary intake is associated with respiratory acidosis.
B)
In the absence of carbohydrate energy sources, her body is metabolizing fat and releasing ketoacids.
C)
Metabolism of dietary fats without the buffer action of carbohydrates results in the catabolism of ketoacids.
D)
Decreased carbohydrate intake induces insulin deficiency and consequent ketoacidosis.
Ans:
B
Feedback:
Low-carbohydrate diets can induce the fat metabolism and consequent metabolic acidosis that is more commonly associated with diabetic ketoacidosis. The acidotic state is not classified as respiratory in nature and does not involve a buffer role for carbohydrates or insulin deficiency.
11.
A 14-year-old boy, appearing to be intoxicated, is brought to the emergency room by ambulance. The EMTs report that the boy has denied consuming anything out of the ordinary, but an open antifreeze container was found in the boy's room. Which of the following is likely to be used to treat the patient's symptoms?
A)
Gastric lavage
B)
Syrup of ipecac
C)
Fomepizole
D)
Sodium bicarbonate
Ans:
C
Feedback:
Ethylene glycol is found in products ranging from antifreeze and deicing solutions to carpet and fabric cleaners. It tastes sweet and is intoxicating?the factors that contribute to its abuse potential. A lethal dose is approximately 100 mL. It is rapidly absorbed from the intestine, making treatment with either gastric lavage or syrup of ipecac ineffective. Fomepizole, with specific indications for ethylene glycol poisoning, was recently approved by the U.S. Food and Drug Administration.
12.
A patient who overdosed on aspirin is brought to the emergency department. The nurse caring for this patient should anticipate which of the following clinical manifestations? Select all that apply.
A)
Respiratory rate of 40
B)
BP 100/72
C)
ABG report: pH 7.50, PCO2 31 mm Hg, and HCO3 level 19 mmol/L.
D)
Urine output approximately 100 mL/hour
E)
Bilateral crackles (fluid) in the lungs
Ans:
A, C
Feedback:
The salicylates cross the blood?brain barrier and directly stimulate the respiratory center, causing hyperventilation and respiratory alkalosis (answer choices A and C). The blood pressure is at normal range, and the urine output is normal or excessive depending on fluid intake. Bilateral crackles (fluid) in the lungs are usually a sign of heart failure.
13.
Which of the following individuals are at risk of developing metabolic alkalosis? Select all that apply.
A)
A 70-year-old woman who has taken two tablespoons of baking soda to settle her ?sour stomach?
B)
A hospital patient who is on nasogastric suction following gastric surgery
C)
A 20-year-old male who has been regularly inducing himself to vomit following binge eating
D)
A 33-year-old male patient who is on mechanical ventilation in the intensive care unit following a head injury
E)
A 58-year-old alcoholic male who has been foregoing food for several weeks while drinking heavily
F)
A 60-year-old female who has chronic renal failure secondary to hypertension
Ans:
A, B, C
Feedback:
Ingestion of bicarbonate, gastric suction, and vomiting are causes of metabolic alkalosis. Patients on mechanical ventilation are at risk of respiratory alkalosis, while heavy alcohol use and renal failure are associated with acidosis.
14.
A 55-year-old male client with a history of cardiovascular disease has been admitted to the intensive care unit after recovering from cardiogenic shock. In the hours since admission, the client's arterial blood gases indicate acidosis, most likely acute lactic acidosis. Which of the following signs, symptoms, and diagnostic findings might his care team anticipate before the acid?base balance is restored? Select all that apply.
A)
Decreased pH
B)
Cardiac dysrhythmias
C)
Decreased alertness and cognition
D)
Hypoventilation
E)
Nausea and vomiting
Ans:
A, B, C, E
Feedback:
As with any form of acidosis, pH is apt to be lower than normal. Metabolic acidosis is also associated with dysrhythmias, decreased alertness, and nausea and vomiting. Respiration is likely to be increased in both rate and depth.
15.
A nurse is providing care for a client who has been diagnosed with metabolic alkalosis after several days of antacid use. Which of the following treatments should the nurse prepare to give?
A)
Intravenous or oral administration of free hydrogen ions
B)
Intravenous administration of KCl solution
C)
Administration of oxygen and NaHCO3 solution
D)
Supplementary oxygen and possible mechanical ventilation
Ans:
B
Feedback:
KCl administration facilitates the renal retention of hydrogen ions, resulting in lowering of pH. It is not possible to administer free H+ ions, and sodium bicarbonate would exacerbate her condition. Mechanical ventilation is indicated in cases of respiratory acidosis.
16.
A hospital patient's arterial blood gases indicate normal levels of oxygen and increased carbon dioxide. The patient's respiratory rate is 12 breaths/minute (normal 14 to 20 breaths/minute) with all other vital signs within normal range. While not evident from assessment and diagnostics, the patient's kidneys are minimizing both H+ excretion and HCO3? reabsorption. What is this client's most likely diagnosis?
A)
Respiratory alkalosis
B)
Metabolic acidosis
C)
Respiratory acidosis
D)
Metabolic alkalosis
Ans:
D
Feedback:
In response to increased bicarbonate, the client is hypoventilating to increase carbon dioxide partial pressure. As well, renal compensation is aimed at lowering pH by both reducing H+ excretion and HCO3? reabsorption. The given data are incongruent with the other major acid?base imbalances.
17.
A 77-year-old female diagnosed with chronic obstructive pulmonary disease (COPD) is experiencing impaired gas exchange and CO2 retention, despite a rapid respiratory rate. Which of the following pathophysiological principles would her health care team expect if her compensatory mechanisms are working?
A)
Arterial blood gas sampling indicates a pH in the range of 7.45 to 7.55.
B)
Her kidneys are likely to reabsorb H+ and secrete HCO3?
C)
Her body will produce excess metabolic CO2.
D)
Her kidneys will adapt with an increase in plasma HCO3? and her pH will decrease.
Ans:
D
Feedback:
Respiratory acidosis is accompanied by renal adaptation with a more marked increase in plasma HCO3? and a lesser decrease in pH. Her pH is likely below 7.35, and the likely renal response involves the reabsorption of HCO3? and secretion of H+. Excess CO2 production is not a common manifestation of obstructive lung disease.
18.
The ICU nurse is concerned with her patient's arterial blood gas (ABG) results?especially the pH 7.30; and PCO2 49 mm Hg. The nurse interprets these ABG results to mean respiratory acidosis. The nurse knows which of the following are clinical manifestations of respiratory acidosis? Select all that apply.
A)
Headache with complaints of blurred vision
B)
Muscle twitching
C)
Hyperactive deep tendon reflexes
D)
Complaints of paresthesia sensations around the lips/mouth
E)
Numbness in the fingers and toes
Ans:
A, B
Feedback:
Carbon dioxide readily crosses the blood?brain barrier, exerting its effects by changing the pH of brain fluids. Elevated levels of CO2 produce vasodilation of cerebral blood vessels, causing headache, blurred vision, irritability, muscle twitching, and psychological disturbances. Distracters C and D are related to hypocalcaemia. Numbness in the fingers and toes correlates with respiratory alkalosis.
19.
A 55-year-old woman has presented to the emergency department following a panic attack. Her blood pressure, respiratory rate, and heart rate are all highly elevated, while her temperature and oxygen saturation are within normal ranges. What is the woman's body most likely doing to address the changes in pH associated with her situation?
A)
Her kidneys will limit the amount of bicarbonate that they reabsorb.
B)
She will be retaining Cl? ions in an effort to lower pH.
C)
Her respiratory center will attempt to lower her CO2 levels.
D)
The patient's kidneys will excrete more hydrogen ions than they normally do.
Ans:
A
Feedback:
Renal compensation for respiratory alkalosis involves decreased bicarbonate reabsorption. Manipulation of Cl? ions is not a compensatory mechanism that the body is capable of, and increased CO2 levels and decreased H+ would compensate for her acid?base imbalance.
20.
In the neurotrauma unit, a teenager with a closed head injury related to an automobile accident is experiencing high intracranial pressure (ICP). He is intubated and is on a ventilator. One treatment for this is to allow him to progress into which acid?base imbalance in an attempt to lower ICP?
A)
Metabolic acidosis
B)
Metabolic alkalosis
C)
Respiratory acidosis
D)
Respiratory alkalosis
Ans:
D
Feedback:
Respiratory alkalosis is seen as a treatment with the ventilator with intubated people experiencing high intracranial pressure (ICP) in order to attempt to lower the ICP.
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