Chapter 14: Concepts of Acid-Base Balance

A nurse evaluates a client's arterial blood gas values (ABGs): pH 7.30, PaO2 86 mm Hg, PaCO2 55 mm Hg, and HCO3 22 mEq/L (22 mmol/L). Which intervention does the nurse implement first? a. Assess the airway. b. Administer prescribed bronchodilators. c. Provide oxygen. d. Administer prescribed mucolytics.

ANS: A All interventions are important for clients with respiratory acidosis; this is indicated by the ABGs. However, the priority is assessing and maintaining an airway. Without a patent airway, other interventions will not be helpful.

A nurse assesses a client who is experiencing an acid-base imbalance. The client's arterial blood gas values are pH 7.2, PaO2 88 mm Hg, PaCO2 38 mm Hg, and HCO3 19 mEq/L (19 mmol/L). Which assessment would the nurse perform first? a. Cardiac rate and rhythm b. Skin and mucous membranes c. Musculoskeletal strength d. Level of orientation

ANS: A Early cardiovascular changes for a client experiencing moderate acidosis include increased heart rate and cardiac output. As the acidosis worsens, the heart rate decreases and electrocardiographic changes will be present. The nurse responds by performing a thorough cardiovascular assessment. Changes will occur in the integumentary system, musculoskeletal system, and neurologic system, but assessing for the cardiovascular complications comes first.

A nurse assesses a client who is admitted with an acid-base imbalance. The client's arterial blood gas values were pH 7.32, PaO2 85 mm Hg, PaCO2 34 mm Hg, and HCO3 16 mEq/L (16 mmol/L). The most recent blood gasses show a drop in the pH. What action does the nurse take next? a. Assess client's rate, rhythm, and depth of respiration. b. Measure the client's pulse and blood pressure. c. Document the findings and continue to monitor. d. Notify the primary health care provider.

ANS: A Progressive skeletal muscle weakness is associated with increasing severity of acidosis. Muscle weakness can lead to severe respiratory insufficiency. Acidosis does lead to dysrhythmias (due to hyperkalemia), but these would best be assessed with cardiac monitoring. Findings would be documented, but simply continuing to monitor is not sufficient. Before notifying the primary care provider, the nurse must have more data to report.

A nurse assesses a client with diabetes mellitus who is admitted with an acid-base imbalance. The client's arterial blood gas values are pH 7.36, PaO2 98 mm Hg, PaCO2 33 mm Hg, and HCO3 18 mEq/L (18 mmol/L). Which sign or symptom does the nurse identify as an example of the client's compensatory mechanisms? a. Increased rate and depth of respirations b. Increased urinary output c. Increased thirst and hunger d. Increased release of acids from the kidneys

ANS: A This client has metabolic acidosis. The respiratory system compensates by increasing its activity and blowing off excess carbon dioxide. Increased urinary output, thirst, and hunger are signs and symptoms of hyperglycemia but are not compensatory mechanisms for acid- base imbalances. The kidneys do not release acids.

A nurse is caring for a client who has just experienced a 90-second tonic-clonic seizure. The client's arterial blood gas values are pH 6.88, PaO2 50 mm Hg, PaCO2 60 mm Hg, and HCO3 22 mEq/L (22 mmol/L). What action would the nurse take first? a. Apply oxygen by mask or nasal cannula. b. Apply a paper bag over the client's nose and mouth. c. Administer 50 mL of sodium bicarbonate intravenously. d. Administer 50 mL of 20% glucose and 20 units of regular insulin.

ANS: A This client is severely hypoxic and needs oxygen. Now that the seizure has ended, the client can breathe again normally, so oxygen administration will rapidly increase the PaO2. Rebreathing carbon dioxide with a paper bag would make the acidosis worse. Bicarbonate is only indicated with extremely low pH and serum bicarbonate levels. Glucose and insulin are administered to decrease the high potassium levels associated with acidosis, but this situation should reverse itself with oxygen and breathing.

A nurse assesses a client who is experiencing an acid-base imbalance. The client's arterial blood gas values are pH 7.32, PaO2 94 mm Hg, PaCO2 34 mm Hg, and HCO3 18 mEq/L (18 mmol/L). For which clinical signs and symptoms would the nurse assess? (Select all that apply.) a. Reduced deep tendon reflexes b. Drowsiness c. Increased respiratory rate d. Decreased urinary output e. Positive Trousseau sign f. Flaccid paralysis

ANS: A, B, C Metabolic acidosis causes neuromuscular changes, including reduced muscle tone and deep tendon reflexes. Clients usually present with lethargy and drowsiness. The respiratory system will attempt to compensate for the metabolic acidosis; therefore, respirations will increase rate and depth. Flaccid paralysis can occur. A positive Trousseau sign is associated with alkalosis. Decreased urine output is not a sign of metabolic acidosis.

A nurse is planning interventions that regulate acid-base balance to ensure that the pH of a client's blood remains within the normal range. Which abnormal physiologic functions may occur if the client experiences an acid-base imbalance? (Select all that apply.) a. Reduction in the function of hormones b. Fluid and electrolyte imbalances c. Increase in the function of selected enzymes d. Excitable cardiac muscle membranes e. Increase in the effectiveness of many drugs f. Changes in GI tract excitability

ANS: A, B, D, F Acid-base imbalances interfere with normal physiology, including reducing the function of hormones and enzymes, causing fluid and electrolyte imbalances, causing heart membranes and GI tract to be more or less excitable, and decreasing the effectiveness of many drugs.

A nurse assesses a client who is receiving total parenteral nutrition. For which adverse effects related to an acid-base imbalance would the nurse assess? (Select all that apply.) a. Positive Chvostek sign b. Elevated blood pressure c. Bradycardia d. Increased muscle strength e. Anxiety and irritability f. Tetany

ANS: A, E A client receiving total parenteral nutrition is at risk for metabolic alkalosis. Signs and symptoms of metabolic alkalosis include positive Chvostek sign, normal or low blood pressure, increased heart rate, skeletal muscle weakness, possible tetany and seizures, and anxiety and irritability.

A nurse is caring for a client who has the following arterial blood values: pH 7.12, PaO2 56 mm Hg, PaCO2 65 mm Hg, and HCO3 22 mEq/L (22 mmol/L). Which clinical situation does the nurse correlate with these values? a. Diabetic ketoacidosis in a person with emphysema b. Bronchial obstruction related to aspiration of a hot dog c. Anxiety-induced hyperventilation in an adolescent d. Diarrhea for 36 hours in an older, frail woman

ANS: B Arterial blood gas values indicate that the client has acidosis with normal levels of bicarbonate, suggesting that the problem is not metabolic. Arterial concentrations of oxygen and carbon dioxide are abnormal, with low oxygen and high carbon dioxide levels. Thus, this client has respiratory acidosis from inadequate gas exchange. The fact that the bicarbonate level is normal indicates that this is an acute respiratory problem rather than a chronic problem, because no renal compensation has occurred. The client who would have these ABG values is the one with the new onset of airway obstruction.

After teaching a client who was malnourished and is being discharged, a nurse assesses the client's understanding. Which statement indicates that the client correctly understood teaching to decrease risk for the development of metabolic acidosis? a. "I will drink at least three glasses of milk each day." b. "I will eat three well-balanced meals and a snack daily." c. "I will not take pain medication and antihistamines together." d. "I will avoid salting my food when cooking or during meals."

ANS: B Starvation or a diet with too few carbohydrates can lead to metabolic acidosis by forcing cells to switch to using fats for fuel and by creating ketoacids as a by-product of excessive fat metabolism. Eating sufficient calories from all food groups helps reduce this risk. Milk, taking pain medications with antihistamines, and salting food are not related.

A diabetic client becomes septic after a bowel resection and is having problems with respiratory distress. The nurse reviews the labs and finds the following ABG results: pH 7.50, PaCO2 30, HCO3 : 24, and PaO2 68. What does the nurse recognize as the primary factor causing this the acid-base imbalance? a. Atelectasis due to respiratory muscle fatigue b. Hyperventilation due to poor oxygenation c. Hypoventilation due to morphine PCA d. Kussmaul respirations due to glucose of 102 mg/dL (5.7 mmol/L)

ANS: B The ABG results indicate respiratory alkalosis. The client has low oxygenation as indicated by low partial pressure of arterial oxygen causing a compensatory mechanism of increased respirations and hyperventilation. Respiratory muscle fatigue and hypoventilation would cause respiratory acidosis with a low pH and high PaCO2. Kussmaul respirations are characterized by deep labored breathing and are a compensatory mechanism to metabolic acidosis, not hypoxemia or alkalosis.

A nurse evaluates the following arterial blood gas values in a client: pH 7.48, PaO2 98 mm Hg, PaCO2 28 mm Hg, and HCO3 22 mEq/L (22 mmol/L). Which client condition does the nurse correlate with these results? a. Diarrhea and vomiting for 36 hours b. Anxiety-induced hyperventilation c. Chronic obstructive pulmonary disease (COPD) d. Diabetic ketoacidosis and emphysema

ANS: B The elevated pH level indicates alkalosis. The bicarbonate level is normal, and so is the oxygen partial pressure. Loss of carbon dioxide is the cause of the alkalosis, which would occur in response to hyperventilation. Diarrhea and vomiting would cause metabolic acidosis and COPD would lead to respiratory acidosis. The client with emphysema most likely would have combined metabolic acidosis on top of a mild, chronic respiratory acidosis.

A nurse is planning care for a client who is hyperventilating. The client's arterial blood gas values are pH 7.52, PaO2 94 mm Hg, PaCO2 31 mm Hg, and HCO3 26 mEq/L (26 mmol/L). Which question would the nurse ask when developing this client's plan of care? a. "Do you take any over-the-counter medications?" b. "You appear anxious. What is causing your distress?" c. "Do you have a history of anxiety attacks?" d. "You are breathing fast. Is this causing you to feel light-headed?

ANS: B The nurse would assist the client who is experiencing anxiety-induced respiratory alkalosis to identify causes of the anxiety. The other questions will not identify the cause of the acid-base imbalance. The other three questions are also yes/no and close-ended.

A nurse is assessing a client who has acute pancreatitis and is at risk for an acid-base imbalance. For which manifestation of this acid-base imbalance would the nurse assess? a. Agitation b. Kussmaul respirations c. Seizures d. Positive Chvostek sign

ANS: B The pancreas is a major site of bicarbonate production. Pancreatitis can cause metabolic acidosis through underproduction of bicarbonate ions. Signs and symptoms of acidosis include lethargy and Kussmaul respirations. Agitation, seizures, and a positive Chvostek sign are signs and symptoms of the electrolyte imbalances that accompany alkalosis.

A nurse is caring for a client who is experiencing excessive diarrhea. The client's arterial blood gas values are pH 7.18, PaO2 98 mm Hg, PaCO2 45 mm Hg, and HCO3 16 mEq/L (16 mmol/L). Which primary health care provider order does the nurse expect to receive? a. Furosemide 40 mg b. Sodium bicarbonate c. Mechanical ventilation d. Indwelling urinary catheter

ANS: B This client's arterial blood gas values represent metabolic acidosis related to a loss of bicarbonate ions from diarrhea. The bicarbonate would be replaced to help restore this client's acid-base balance as the pH is below 7.2 and the bicarbonate level is low. Furosemide would cause an increase in acid fluid and acid elimination via the urinary tract; although this may improve the client's pH, the client has excessive diarrhea and cannot afford to lose more fluid. Mechanical ventilation is used to treat respiratory acidosis for clients who cannot keep their oxygen saturation at 90%, or who have respiratory muscle fatigue. Mechanical ventilation and an indwelling urinary catheter would not be prescribed for that client.

A nurse is planning care for a client who is lethargic and confused. The client's arterial blood gas values are pH 7.30, PaO2 96 mm Hg, PaCO2 43 mm Hg, and HCO3 19 mEq/L (19 mmol/L). Which questions would the nurse ask the client and spouse when developing the plan of care? (Select all that apply.) a. "Are you taking any antacid medications?" b. "Is your spouse's current behavior typical?" c. "Do you drink any alcoholic beverages?" d. "Have you been participating in strenuous activity?" e. "Are you experiencing any shortness of breath?"

ANS: B, C, D This client's symptoms of lethargy and confusion are related to a state of metabolic acidosis. The nurse would ask the client's spouse or family members if the client's behavior is typical for him or her, and establish a baseline for comparison with later assessment findings. The nurse would also assess for alcohol intake because alcohol can cause metabolic acidosis. Excessive and strenuous activity can lead to overproduction of hydrogen ions. The other options are not causes of metabolic acidosis.

A nurse is assessing clients who are at risk for acid-base imbalance. Which clients are correctly paired with the acid-base imbalance? (Select all that apply.) a. Metabolic alkalosis—young adult who is prescribed intravenous morphine sulfate for pain b. Metabolic acidosis—older adult who is following a carbohydrate-free diet c. Respiratory alkalosis—client on mechanical ventilation at a rate of 28 breaths/min d. Respiratory acidosis—postoperative client who received 6 units of packed red blood cells e. Metabolic alkalosis—older client prescribed antacids for gastroesophageal reflux disease

ANS: B, C, E Respiratory acidosis often occurs as the result of underventilation. The client who is taking opioids, especially IV opioids, is at risk for respiratory depression and respiratory acidosis. One cause of metabolic acidosis is a strict low-calorie diet or one that is low in carbohydrate content. Such a diet increases the rate of fat catabolism and results in the formation of excessive ketoacids. A ventilator set at a high respiratory rate or tidal volume will cause the client to lose too much carbon dioxide, leading to an acid deficit and respiratory alkalosis. Citrate is a substance used as a preservative in blood products. It is not only a base, but also a precursor for bicarbonate. Multiple units of packed red blood cells could cause metabolic alkalosis. Sodium bicarbonate antacids may increase the risk of metabolic alkalosis.

After providing discharge teaching, a nurse assesses the client's understanding regarding increased risk for metabolic alkalosis. Which statement indicates that the client needs additional teaching? a. "I don't drink milk because it gives me gas and diarrhea." b. "I have been taking digoxin every day for the last 15 years." c. "I take sodium bicarbonate after every meal to prevent heartburn." d. "In hot weather, I sweat so much that I drink six glasses of water each day."

ANS: C Excessive oral ingestion of sodium bicarbonate and other bicarbonate-based antacids can cause metabolic alkalosis. Avoiding milk, taking digoxin, and sweating would not lead to increased risk of metabolic alkalosis.

A nurse assesses a client who is prescribed furosemide for hypertension. For which acid-base imbalance does the nurse assess to prevent complications of this therapy? a. Respiratory acidosis b. Respiratory alkalosis c. Metabolic acidosis d. Metabolic alkalosis

ANS: D Many diuretics, especially loop and thiazide diuretics, increase the excretion of hydrogen ions, leading to excess acid loss through the renal system. This situation is an actual acid deficit.

A nurse is caring for a client who is experiencing moderate metabolic alkalosis. What action would the nurse take? a. Monitor daily hemoglobin and hematocrit values. b. Administer furosemide intravenously. c. Encourage the client to take deep breaths. d. Teach the client fall prevention measures.

ANS: D The most important nursing care for a client who is experiencing moderate metabolic alkalosis is providing client safety. Client's with metabolic alkalosis have muscle weakness and are at risk for falling. The other nursing interventions are not appropriate for metabolic alkalosis.