Pathophysiology PrepU - Chapter 9: Altered Acid-Base Balance

The nurse recognizes the role of the lungs in acid-base balance is regulation of which of the following? A) Hydrogen B) HCO3 C) CO2 D) H2O

C) CO2 Explanation: Carbon dioxide (CO2) is regulated by the lungs. HCO3 and H+ are regulated by kidneys.

The nurse is caring for the following group of clients. Select the client most likely to be diagnosed with respiratory alkalosis. A) A 26-year-old female with anxiety who has been hyperventilating B) A 45-year-old male with pneumothorax after a car accident C) A 63-year-old male with a 40-year history of smoking and chronic lung disease D) An 18-year-old female who has overdosed on an opioid

A) A 26-year-old female with anxiety who has been hyperventilating Explanation: Respiratory alkalosis can occur with hyperventilating and the loss of CO2.The other three clients are more at risk for respiratory acidosis as a result of retaining CO2.

The nurse is caring for a client who has excessive diarrhea. Which acid-base disturbance does the nurse anticipate will result from having excessive diarrhea? A) Metabolic acidosis B) An increase in bicarbonate C) No change in values from normal D) Increased pH value

A) Metabolic acidosis Explanation: The client who has diarrhea has increased loss of bicarbonate from the intestinal tract, which results in metabolic acidosis. The pH value would be decreased, and the bicarbonate would be decreased.

In which client would the nurse be most likely to assess the signs and symptoms of an acid-base imbalance? A) A client with chronic obstructive pulmonary disease (COPD) whose most recent arterial blood gases reveal a PCO2 of 51 mm Hg B) A client with a fluid volume deficit who has been receiving intravenous 0.45% NaCl for over 48 hours C) A client who has been admitted with a traumatic head injury and whose intracranial pressure is 18 mm Hg D) A laboring client who is receiving an oxytocin infusion and who has been in the second stage of labor for 7 hours

A) A client with chronic obstructive pulmonary disease (COPD) whose most recent arterial blood gases reveal a PCO2 of 51 mm Hg Explanation: An elevated PCO2 is commonly associated with respiratory acidosis because excess CO2 ultimately increases the concentration of H+ ions. Increased intracranial pressure, oxytocin infusion, and the administration of hypotonic fluids are not directly linked to common alterations in acid-base balance.

A client's most recent laboratory results suggest the presence of metabolic alkalosis. What action by the nurse best addresses a potential cause of this acid-base imbalance? A) Administering an antiemetic to treat the client's frequent vomiting B) Repositioning the client frequently to reduce pressure on dependent skin surfaces C) Assessing the client's level of consciousness using the Glasgow Coma Scale D) Assessing the client's bowel sounds and administering scheduled stool softeners

A) Administering an antiemetic to treat the client's frequent vomiting Explanation: Vomiting results in the loss of hydrogen ions, potentially resulting in metabolic alkalosis. Constipation and skin breakdown are not among the most common causes of metabolic alkalosis. Acid-base imbalances frequently affect cognition, but a change in level of consciousness would not be a cause of the imbalance.

The nurse is caring for a client who has developed hypoxemia and tissue hypoxia. Which of these interventions does the nurse set as a priority intervention? A) Administration of supplemental oxygen B) Rapid, short, shallow breaths C) Alternating deep breathing with holding one's breath D) Rebreathing into a paper bag

A) Administration of supplemental oxygen Explanation: Hypoxia and hypoxemia may be corrected by administration of supplemental oxygen. People with hyperventilation may benefit from reassurance, rebreathing from a paper bag during symptomatic attacks, and attention to the psychological stress. The other options are not appropriate for the treatment of hypoxia.

A client is admitted after losing 44 lb (20 kg) over the past 3 months, largely due to frequent vomiting. What intervention should the nurse anticipate in the treatment of the client's resulting acid-base imbalance? A) Fluid replacement with an intravenous solution containing electrolytes as prescribed B) Mechanical ventilation and administration of supplementary oxygen C) Supplementary oxygen using a non-rebreather mask D) Administration of intravenous sodium bicarbonate as prescribed

A) Fluid replacement with an intravenous solution containing electrolytes as prescribed Explanation: Vomiting ultimately results in the increase in pH that constitutes metabolic alkalosis; intravenous potassium chloride (KCl) solutions are a mainstay of treatment for this acid-base imbalance. Respiratory interventions will not have an appreciable effect because of the metabolic nature of the imbalance. Sodium bicarbonate would exacerbate the client's condition.

The nurse is aware that the major role of the kidneys in regulating acid-base balance is to increase the production of which chemical component? A) HCO3- B) H+ C) HCl D) H2CO3

A) HCO3- Explanation: The kidneys play a critical role in maintaining acid-base balance. They accomplish this through the reabsorption of HCO3-, regulation of H+ secretion, and generation of new HCO3-. The hydrogen/bicarbonate exchange system regulates pH through the secretion of excess H+ and reabsorption of HCO3- by the renal tubules. Bicarbonate is freely filtered in the glomerulus and reabsorbed or reclaimed in the tubules. Each HCO3- that is reclaimed requires the secretion of an H+. H2CO3 is a weak acid. HCl is found in gastric fluid. The kidneys would eliminate, not increase, production of H ion.

Which arterial blood gas (ABG) values tell the nurse a client is in metabolic acidosis? Select all that apply. A) HCO3- of 19 mEq/L (19 mmol/L) B) Base excess of -6 mEq/L (-6 mmol/L) C) PCO2 of 27mm Hg (3.59 kPa) D) Anion gap of 20 mEq/L (20 mmol/L) E) pH 7.25

A) HCO3- of 19 mEq/L (19 mmol/L) B) Base excess of -6 mEq/L (-6 mmol/L) D) Anion gap of 20 mEq/L (20 mmol/L) E) pH 7.25 Explanation: ABGs measure pH, carbon dioxide (PCO2), bicarbonate ion (HCO3-), oxygen PO2, base excess, and the anion gap. A pH that is below 7.35 is considered acidic while above 7.45 is considered alkaline. The PCO2 is considered the primary indicator of respiratory function. Elevation above 45mm Hg (5.99 kPa) indicates acidosis while a decrease below 35mm Hg (4.66 kPa) indicates alkalosis. Bicarbonate (HCO3-) is the primary indicator of metabolic function and is considered alkaline if greater than 26 mEq/L, and acidic if below 22 mEq/L. Base excess measures the level of all the buffer systems in the blood. If the level is more than 0.2 mEq/L above the normal pH of 7.4 it is considered an excess and indicates metabolic alkalosis. Anion gap indicates the difference between plasma concentration of the major measured cation (sodium) and the sum of the measured anions (chloride and bicarbonate). This level rises in conditions of acidosis. Anion gap and base excess or deficit are used primarily to indicate metabolic acid-base disorders.

A client has these arterial blood gas values: anion gap 20 mEq/L (20 mmol/L), pH 7.29, PCO2 37 mm Hg (4.92 mmol/L), HCO3- 11 mEq/L (11 mmol/L), base excess -6 mEq/L (-6 mmol/L). With what condition do these values correspond? A) Lactic acidosis B) lithium toxicity C) Multiple myeloma D) Hyperkalemia

A) Lactic acidosis Explanation: Anion gap (AG) is the difference between the plasma concentration of sodium ions and the sum of the measured anions (chloride and bicarbonate). Normally, the AG value should be between 8 and 16 mEq/L. AG will rise above normal for conditions that commonly cause acidosis such as lactic acidosis and ketoacidosis. Hyperkalemia, lithium toxicity, hypercalcemia, hypermagnesemia, and multiple myeloma will cause a drop in the AG by raising the level of unmeasured cations. ABGs measure pH, carbon dioxide (PCO2), bicarbonate ion (HCO3-), oxygen (PO2), base excess, and the anion gap. A pH that is below 7.35 is considered acidic. The PCO2 is the primary indicator of respiratory function and falls between 35 and 45mm Hg. Bicarbonate (HCO3-) is the primary indicator of metabolic function and is acidic if below 22 mEq/L. Base excess measures the level of all the buffer systems in the blood. If the level is more than 0.2 mEq/L below the normal pH of 7.4 it is considered deficit and indicates metabolic acidosis.

The nurse teaches a client with renal insufficiency to limit protein intake. What is an appropriate explanation for this restriction? Explanation: A) Protein metabolism increases the need for renal excretion of acids. B) Proteins contain high amounts of sodium to excrete. C) Proteins overwork the kidneys because they cause fluid retention. D) Protein catabolism stimulates aldosterone production.

A) Protein metabolism increases the need for renal excretion of acids. Explanation: Fixed, or nonvolatile acids, such as sulfuric, hydrochloric, and phosphoric acid are the products of protein metabolism and are eliminated by the kidneys. In renal insufficiency and failure, the kidneys are less able to eliminate the higher amount of acid. The volatile acids such as carbon dioxide leave the body through the lungs. Proteins contain high amounts of potassium.

The renal control mechanism of restoring the acid-base balance is accomplished through which process? A) Reabsorption of HCO3 and excretion of H+ restores acid-base balance through the renal control mechanisms. B) Stimulation of the chemoreceptors in the brain stem C) Reabsorption of hydrogen and excretion of carbonic acid D) Regulation of the production of carbonic acid

A) Reabsorption of HCO3 and excretion of H+ restores acid-base balance through the renal control mechanisms. Explanation: Reabsorption of HCO3 and excretion of H+ restores acid-base balance through the renal control mechanisms. Respiratory control mechanisms of restoring acid-base balance are done via regulation of production of carbonic acid and stimulation of the chemoreceptors in the brain.

The nurse enters a client's hospital room and finds the client breathing rapidly, stating, "I must be having a stroke, my fingers are tingling!" Which acid-base balance disorder is this client experiencing due to hyperventilation? A) Respiratory alkalosis B) Respiratory acidosis C) Metabolic acidosis D) Metabolic alkalosis

A) Respiratory alkalosis Explanation: Respiratory alkalosis is caused by hyperventilation or a respiratory rate in excess of that needed to maintain normal plasma PCO2 levels. It may occur as the result of central stimulation of the medullary respiratory center or stimulation of peripheral pathways to the medullary respiratory center, but rarely does it occur as a result of a physical pathological condition.

The nurse is assessing a client with abnormal blood gas values. Which of these interpretations does the nurse make regarding the client's physiologic status? A) The client has abnormalities in his buffer system. B) The client has alterations in vital signs. C) The client has abnormalities in his cardiovascular system. D) The client has a decreased hemoglobin.

A) The client has abnormalities in his buffer system. Explanation: The client with an abnormal blood gas may have abnormalities in his respiratory, renal, or chemical buffer system. These systems assist in regulating blood gases. Hemoglobin, vital signs, and the cardiovascular system are not direct buffers for this system. The only assumption the nurse can make is that there is a problem with the buffer system.

The nurse is caring for a client with metabolic alkalosis. Which of these arterial blood gas results supports this diagnosis? A) pH of 7.50 and HCO3 of 45 mEq/L (45 mmol/L) B) pH of 7.25 and HCO3 of 18 mEq/L (18 mmol/L) C) pH of 7.45 and HCO3 of 24 mEq/L (24 mmol/L) D) pH of 7.35 and HCO3 of 22 mEq/L (22 mmol/L)

A) pH of 7.50 and HCO3 of 45 mEq/L (45 mmol/L) Explanation: A diagnosis of metabolic acidosis is made on the basis of decreased pH and HCO3 levels. A pH of 7.25 is well below the reference range of 7.35 - 7.45 and an HCO3 level of 18 mEq/L is below the reference range of 22 - 26 mEq/L. A ph level that is above the reference range suggests alkalosis, not acidosis. Similarly, an HCO3 level about the reference range is associated with alkalosis.

The nurse is evaluating a client's blood gases. The client has a pH of 7.35. How does the nurse interpret this value? A) It indicates a respiratory problem. B) It is within a normal range. C) It indicates alkalosis. D) It indicates acidosis.

B) It is within a normal range. Explanation: The normal body range of pH is 7.35 to 7.45. The other answers are incorrect. An acidotic value would be indicated by a pH less than 7.35 and an alkalotic level would be indicated by a pH greater than 7.45.

A client with a long history of alcohol abuse has been admitted to the emergency department after several of days of heavy drinking. The nurse can best promote the restoration of the client's acid-base balance by:

Administering intravenous sodium bicarbonate as prescribed. Explanation: Sodium bicarbonate is among the more common treatments for the metabolic acidosis that results from high alcohol intake. Breathing exercises do not have appreciable effect, though respiratory compensation will likely be taking place. Magnesium sulfate addresses a likely electrolyte imbalance, not an acid-base imbalance. The client's position will have a negligible effect on acid-base balance.

A newly admitted client's diagnostic testing indicates metabolic acidosis. What action should the nurse take when working to determine the cause? A) Assess the client's pupillary light reflex B) Assess the client's blood glucose levels C) Test the client's stool for occult blood D) Auscultate the client's lungs for adventitious sounds

B) Assess the client's blood glucose levels Explanation: Hyperglycemia can result in diabetic ketoacidosis, a form of metabolic acidosis. Changes in respiratory status would result in acid-base disorders of the respiratory, not metabolic, type. The presence of fecal occult blood and disruptions to the pupillary reflex are not likely to result in metabolic acidosis.

When explaining how carbon dioxide combines with water to form carbonic acid as part of an acid-base lecture, the faculty instructor emphasizes that which enzyme is needed as a catalyst for this reaction? A) Phenylalanine hydroxylase B) Carbonic anhydrase C) Hydrolases D) Trypsin

B) Carbonic anhydrase Explanation: 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.

A client has been diagnosed with metabolic acidosis. What assessment finding does the nurse expect? A) Increased PCO2 above 45 mm/Hg (5.99 kPa) B) Decreased pH below 7.35 C) Increased pH above 7.45 D) Decreased PCO2 below 35 mm/Hg (4.66 kPa)

B) Decreased pH below 7.35 Explanation: In metabolic acidosis, the client's pH will decrease below 7.35 or normal range. In addition , the client's HCO3- will decrease to below 22 mEq/L (22 mmol/L)

The nurse is reviewing laboratory data for the client with an anion gap of 17. The nurse recognizes which condition is associated with an increased anion gap mEq/L (mmol/L)? A) Multiple myeloma B) Lactic acidosis C) Hyperkalemia D) Hypermagnesemia

B) Lactic acidosis Explanation: The anion gap describes the difference between the serum concentration of the major measured cation (Na) and the sum of the measured anions (Cl and HCO3 ). This difference represents the concentration of unmeasured anions, such as phosphates, sulfates, organic acids, and proteins (Fig. 8-18). Normally, the anion gap ranges between 8 and 12 mEq/L (8 and 12 mmol/L). Lactic acidosis and ketoacidosis results in an increased anion gap as a result of elevated levels of metabolic acids. The other options result in a decreased anion gap.

A client's arterial blood gases reveal normal oxygen level, pH 7.50, PCO2 level of 50 mmHg (6.65 kPa) and HCO3 level of 30 (30 mmol/L). The client's respiratory rate is 12 breaths/min and all other vital signs are within normal range. What is this client's most likely diagnosis? A) Metabolic acidosis B) Metabolic alkalosis C) Respiratory alkalosis D) Respiratory acidosis

B) Metabolic alkalosis Explanation: 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. Metabolic alkalosis is manifested with increased pH, increased HCO3, and increased PCO2 levels. The given data are incongruent with the other major acid-base imbalances.

The condition of a client with metabolic acidosis from an intestinal fistula is not improving. The pulse is 125 beats/min and the BP 84/56 mm Hg. ABG values are: pH 7.1, HCO3- 18 mEq/L (18 mmol/L), PCO2 57 mm Hg (7.58 kPa). What IV medication should the nurse expect to provide next? A) Antibiotics B) Sodium bicarbonate C) Potassium chloride D) Epinephrine

B) Sodium bicarbonate Explanation: When a client with acidosis has the pH drop to 7.1 to 7.2 there is a decrease in cardiac contractility and output. The heart is less responsive to catecholamines, and fatal ventricular dysrhythmias may occur. Sodium bicarbonate (NaHCO3) is used to partially correct the acidosis in this type of normal anion gap condition. This improves cardiovascular responsiveness. Antibiotics would be used for sepsis. Potassium would not be appropriate because levels are already elevated in acidosis.

The nurse is caring for a client with Bartter syndrome. Which assessment(s) will the nurse include in the daily plan of care related to this diagnosis? Select all that apply. A) breath sounds B) temperature C) plasma sodium levels D) daily weight E) intake and output measurements F) bowel movement frequency and appearance

B) temperature C) plasma sodium levels D) daily weight E) intake and output measurements F) bowel movement frequency and appearance Explanation: The client with Bartter syndrome is unable to effectively reabsorb salts from the renal tubules, leading to polyuria and electrolyte deficits. Therefore, the nurse monitors measurements associated with fluid and electrolyte imbalances including sodium levels, intake and output, and daily weight. Because excess prostaglandin activity is also associated with Bartter syndrome, the nurse assesses for fever, vomiting, and diarrhea. There is no expectation for respiratory involvement or abnormal breath sounds with this condition.

The nurse who is providing care for several clients recognizes which client is at the highest risk for developing an acid-base imbalance? A) A client who has a rectovaginal fistula that will require surgery B) A client who had an anaphylactic reaction to an insect sting and required resuscitation C) A client who is being treated for acute kidney injury and who requires dialysis D) A client who is receiving intravenous penicillin for the treatment of primary syphilis

C) A client who is being treated for acute kidney injury and who requires dialysis Explanation: Because of the key role that the kidneys play in the maintenance of acid-base balance, individuals with kidney disease are vulnerable to acid-base disorders. Anaphylaxis, syphilis, and fistulas do not present particular risks for acid-base imbalances.

The nurse is caring for a client with an acid-base imbalance. Which of these does the nurse recognize is correct regarding compensation? A) An increased pH is demonstrated. B) A decreased pH is demonstrated. C) A pH moves toward the normal range. D) There is no alteration in the blood gas values.

C) A pH moves toward the normal range. Explanation: The client who is compensating for an acid-base imbalance will have a pH that has moved back into the normal range. The other blood gas values will most likely all be out of range.

A child accidentally consumes a container of wood alcohol. The ED physician knows that the child is at risk of developing which of the following? A) Metabolic alkalosis B) Respiratory alkalosis C) Metabolic acidosis D) Respiratory acidosis

C) Metabolic acidosis Explanation: Ingestion of methanol (wood alcohol) results in the production of metabolic acids and causes metabolic acidosis.

A client arrives in the emergency department by ambulance with a family member stating, "He took an overdose of sleeping pills and I found him breathing very shallowly." For which type of acid-base disturbance will the nurse anticipate this client will be treated? A) Metabolic acidosis B) Metabolic alkalosis C) Respiratory acidosis D) Respiratory alkalosis

C) Respiratory acidosis Explanation: Respiratory acidosis occurs in conditions that impair alveolar ventilation and cause an increase in plasma PCO2, also know as hypercapnia, along with a decrease in pH. Respiratory acidosis can occur as an acute or chronic disorder but occurs most often as a result of decreased ventilation. Other acid-base imbalances may occur if the respiratory acidosis is not immediately treated.

As other mechanisms prepare to respond to a pH imbalance, immediate buffering is a result of increased: A) sodium/phosphate anion absorption. B) intracellular albumin. C) bicarbonate/carbonic acid regulation. D) hydrogen/potassium binding.

C) bicarbonate/carbonic acid regulation. Explanation: The bicarbonate buffering system, which is the principal ECF buffer, uses H2CO3 as its weak acid and bicarbonate salt such as sodium bicarbonate (NaHCO3) as its weak base. It substitutes the weak H2CO3 for a strong acid such as hydrochloric acid or the weak bicarbonate base for a strong base such as sodium hydroxide. The bicarbonate buffering system is a particularly efficient system because its components can be readily added or removed from the body. Hydrogen and potassium exchange freely across the cell membrane to regulate acid-base balance. Sodium is not part of the buffering system. Intracellular protein is part of the body protein buffer system; albumin is extracellular.

A client informs the nurse of a problem with acid indigestion. The client notes taking large amounts of calcium carbonate antacids daily but still has no relief. The client consumes about 1 bottle of 100 antacids in 4 days. Which blood gas result does the nurse anticipate? A) pH 7.25 B) PCO2 38 mm Hg (5.05 kPa) C) pH 7.6 D) PO2 80 mm Hg (10.64 kPa)

C) pH 7.6 Explanation: A condition called mild-alkali syndrome is a condition in which chronic ingestion of milk or calcium carbonate antacids leads to hypercalcemia and metabolic alkalosis. The client would be in metabolic alkalosis and have an elevated, not decreased, pH. PCO2 would be expected to be increased (not within normal limits) as the respiratory system will retain PCO2 in compensation for the metabolic alkalosis. PO2 levels would not be affected in the metabolic state.

A nurse is providing care for several clients on an acute medicine unit. Which client should the nurse recognize as being at the highest risk for metabolic alkalosis? A) A client with acquired immunodeficiency syndrome (AIDS) who has developed tuberculosis and is receiving antibiotics B) A client in alcohol withdrawal who is being treated with intravenous anticonvulsants C) A postoperative client who developed sepsis after the dehiscence of an abdominal wound D) A client on continuous nasogastric suction and whose hypertension is being treated with diuretics

D) A client on continuous nasogastric suction and whose hypertension is being treated with diuretics Explanation: Nasogastric suction creates a significant risk for metabolic alkalosis due to the loss of gastric acids. This risk is compounded by the concurrent use of diuretics. Alcohol use is associated with metabolic acidosis. Infections are not directly linked with the development of metabolic alkalosis.

The nurse is caring for a client with acute primary respiratory acidosis. When determining the cause of the acidosis the nurse is aware that which imbalance is most common? A) Decreased CO2 retention B) Renal bicarbonate retention C) Increased metabolic acids D) Impaired alveolar ventilation

D) Impaired alveolar ventilation Explanation: Acute respiratory acidosis is frequently caused by impaired alveolar ventilation with CO2 retention. Increased metabolic acids, such as lactic acid, are characteristic of metabolic acidosis. Bicarbonate retention is a compensatory response to respiratory acidosis, or it can be the cause of metabolic alkalosis when retention is excessive.

The nurse is caring for a client 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 phenomenon is most likely occurring? A) Metabolism of dietary fats without the buffer action of carbohydrates results in the catabolism of ketoacids. B) Decreased carbohydrate intake induces insulin deficiency and consequent ketoacidosis. C) High fat, low carbohydrate dietary intake is associated with respiratory acidosis. D) In the absence of carbohydrate energy sources, her body is metabolizing fat and releasing ketoacids.

D) In the absence of carbohydrate energy sources, her body is metabolizing fat and releasing ketoacids. Explanation: 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.

A nurse is providing care for a client who has been diagnosed with metabolic alkalosis after several days of antacid use. Which treatment should the nurse prepare to give? A) Administration of oxygen and NaHCO3 solution B) Supplementary oxygen and possible mechanical ventilation C) Intravenous or oral administration of free hydrogen ions D) Intravenous administration of a KCl solution

D) Intravenous administration of a KCl solution Explanation: 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.

What is the nurse's expectation about a client's ability to compensate for a metabolic blood gas disorder?

The client will compensate with the respiratory system. Explanation: The one thing that a nurse can expect is that a client with a metabolic disorder will compensate with the respiratory system. The client cannot compensate with the same system. The nurse cannot expect the client's breathing to slow down as in some cases it will increase, depending on the primary disorder.