Prep U and ATI Practice Questions - Acid-Base
A client in the emergency department reports that he has been vomiting excessively for the past 2 days. His arterial blood gas analysis shows a pH of 7.50, partial pressure of arterial carbon dioxide (PaCO2) of 43 mm Hg, partial pressure of arterial oxygen (PaO2) of 75 mm Hg, and bicarbonate (HCO3-) of 42 mEq/L. Based on these findings, the nurse documents that the client is experiencing which type of acid-base imbalance? - Metabolic Alkalosis - Respiratory Alkalosis - Metabolic Acidosis - Respiratory Acidosis
Metabolic alkalosis Explanation: A pH over 7.45 with a HCO3- level over 26 mEq/L indicates metabolic alkalosis. Metabolic alkalosis is always secondary to an underlying cause and is marked by decreased amounts of acid or increased amounts of base HCO3-. The client isn't experiencing respiratory alkalosis because the PaCO2 is normal. The client isn't experiencing respiratory or metabolic acidosis because the pH is greater than 7.35.
A client tells the nurse that the client has been taking Alka-Seltzer (bicarbonate—antacid) four times a day for the past 2 weeks for an upset stomach. Upon assessment of the client, the nurse notes hyperactive reflexes, tetany, and mental confusion. Arterial blood gases reveal pH 7.55; serum HCO3− 37 mEq/L (37 mmol/L). The nurse suspects the client may be experiencing: - Respiratory acidosis - Respiratory alkalosis - Metabolic alkalosis - Metabolic acidosis
Metabolic alkalosis Explanation: Metabolic alkalosis is characterized by a serum pH greater than 7.45; serum HCO3− greater than 29 mEq/L (29 mmol/L); and a base excess greater than 3.0. Transient or acute alkalosis is common during or immediately following excess oral ingestion of bicarbonate antacids. Respiratory acidosis as well as metabolic acidosis would have a decrease in pH. Respiratory alkalosis would have an increase in pH and a HCO3− less than 24 mEq/L (24 mmol/L).
As other mechanisms prepare to respond to a pH imbalance, immediate buffering is a result of increased: - bicarbonate/carbonic acid regulation. - intracellular albumin. - sodium/phosphate anion absorption. - hydrogen/potassium binding.
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.
The nurse is caring for the following group of clients. Select the client most likely to be diagnosed with respiratory alkalosis. - A 26-year-old female with anxiety who has been hyperventilating - A 63-year-old male with a 40-year history of smoking and chronic lung disease - A 45-year-old male with pneumothorax after a car accident - An 18-year-old female who has overdosed on narcotics
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.
A nurse is caring for a client who was in a motor‑vehicle accident. The client reports chest pain and difficulty breathing. A chest x‑ray reveals the client has a pneumothorax. Which of the following arterial blood gas findings should the nurse expect? A. pH 7.06PaO2 86 mm Hg PaCO2 52 mm Hg HCO3− 24 mEq/L B. pH 7.42PaO2 100 mm Hg PaCO2 38 mm Hg HCO3− 23 mEq/L C. pH 6.98PaO2 100 mm Hg PaCO2 30 mm Hg HCO3− 18 mEq/L D. pH 7.58PaO2 96 mm Hg PaCO2 38 mm Hg HCO3− 29 mEq/L
A.CORRECT: A pneumothorax can cause alveolar hyperventilation and increased carbon dioxide levels, resulting in a state of respiratory acidosis. B.These ABGs are within the expected reference range and reflect homeostasis. C.Metabolic acidosis is not indicated for this client. D.Metabolic alkalosis is not indicated for this client.
A nurse is assessing a client who has pancreatitis. The client's arterial blood gases reveal metabolic acidosis. Which of the following are expected findings? (Select all that apply.) A. Tachycardia B. Hypertension C. Bounding pulses D. Hyperreflexia E. Dysrhythmia F. Tachypnea
E.CORRECT: Dysrhythmia is an expected finding in a client who has pancreatitis and metabolic acidosis. F.CORRECT: Tachypnea is an expected finding in a client who has pancreatitis and metabolic acidosis. A.Tachycardia is an expected finding for a client who has respiratory acidosis or metabolic alkalosis. B.Hypertension is an expected finding of respiratory acidosis. C.Bounding pulses is an expected finding for respiratory acidosis due to hypertension. D.Hyperreflexia is an expected finding for a client who has metabolic alkalosis.
The nurse caring for a client with metabolic alkalosis examines arterial blood gas (ABG) results. Which change from the initial value indicates the client's metabolic alkalosis is improving? - CO2 has decreased - pH has increased - O2 has increased - HCO3- has decreased
HCO3- has decreased Explanation: In metabolic alkalosis, the client has a net gain of bicarbonate (HCO3-) which creates a rise in pH. The pH needs to move away from alkalosis, which is the high end of the pH scale, for the client's condition to demonstrate improvement. To lower the pH, either the bicarbonate level needs to decrease or the carbon dioxide (CO2) level needs to increase. Oxygen (O2) concentration is reported on ABG results, but does not indicate acid-base balance.
A client is diagnosed with diabetic ketoacidosis (DKA) in the emergency department. Which clinical manifestations will the client likely exhibit? - Weakness, severe dehydration, and hemiparesis. - Polyuria, polydipsia, voming, and fatigue - Headache, difficulty with problem solving and disturbed behavior, and seizures - Ankle edema, headache, stomach bloating, and high blood pressure
Polyuria, polydipsia, voming, and fatigue Explanation: Diabetic ketoacidosis (DKA) is characterized by hyperglycemia, ketosis, osmotic diuresis, dehydration, and metabolic acidosis. It is an acute life-threatening complication of uncontrolled diabetes. Weakness, severe dehydration, and hemiparesis are signs of hyperosmolar hyperglycemic states. Headache, difficulty problem solving, and disturbed behavior and seizures are signs of hypoglycemia. The signs of hypervolemia include edema (most often in the feet, ankles, wrists, and face); discomfort in the body (causing cramping, headache, stomach bloating); and high blood pressure caused by excess fluid in the bloodstream.
As status asthmaticus worsens, the nurse would expect which acid-base imbalance? - Metabolic Alkalosis - Respiratory Alkalosis - Metabolic Acidosis - Respiratory Acidosis
Respiratory acidosis Explanation: As status asthmaticus worsens, the PaCO2 increases and the pH decreases, reflecting respiratory acidosis.
A nurse is obtaining arterial blood gases for a client who has vomited for 24 hr. The nurse should expect which of the following acid‑base imbalances to result from vomiting for 24 hr? A. Respiratory acidosis B. Respiratory alkalosis C. Metabolic acidosis D. Metabolic alkalosis
D.CORRECT: Excessive vomiting causes a loss of gastric acids and an accumulation of bicarbonate in the blood, resulting in metabolic alkalosis. A.Respiratory acidosis is not indicated for this client. B.Respiratory alkalosis is not indicated for this client. C.Metabolic acidosis is not indicated for this client.
Respiratory alkalosis can be caused by a respiratory rate in excess of that which maintains normal plasma PCO2 levels. What is a common cause of respiratory alkalosis? - Hyperventilation - Kussmaul breathing - Cluster breathing - Hypoventilation
Hyperventilation Explanation: One of the most common causes of respiratory alkalosis is hyperventilation, which is characterized by episodes of overbreathing, often associated with anxiety.
The nurse is caring for a client with metabolic alkalosis whose breathing rate is 8 breaths/min. Which arterial blood gas data does the nurse anticipate finding? - pH: 7.28; PaCO2: 52 mm Hg (6.92 kPa); HCO3: 32 mEq/l (32 mmol/l) - pH: 7.60; PaCO2: 64 mm Hg (8.51 kPa); HCO3: 42 mEq/l (42 mmol/l) - pH: 7.32; PaCO2: 26 mm Hg (3.46 kPa); HCO3: 18 mEq/l (18 mmol/l) - pH: 7.32; PaCO2: 28 mm Hg (3.72kPa); HCO3: 24 mEq/l (24 mmol/l)
pH: 7.60; PaCO2: 64 mm Hg (8.51 kPa); HCO3: 42 mEq/l (42 mmol/l) Explanation: In metabolic alkalosis, arterial blood gas results are anticipated to reflect pH greater than 7.45; a high PaCO2 such as 64 mm Hg (8.51 kPa) and a high HCO3 such as 42 mEq/l (42 mmol/l). The numbers correlate with metabolic alkalosis, which is indicated by the hypoventilation and the retention of CO2. The other blood gas findings do not correlate with metabolic alkalosis.
A charge nurse is teaching a group of nurses about conditions related to metabolic acidosis. Which of the following statements by a unit nurse indicates the teaching has been effective? A. "Metabolic acidosis can occur due to diabetic ketoacidosis." B. "Metabolic acidosis can occur in a client who has myasthenia gravis." C. "Metabolic acidosis can occur in a client who has asthma." D. "Metabolic acidosis can occur due to cancer."
A.CORRECT: Metabolic acidosis results from an excess production of hydrogen ions, which occurs in diabetic ketoacidosis. B.Respiratory acidosis can occur in a client who has myasthenia gravis. C.Respiratory acidosis can occur in a client who has asthma. D.Respiratory acidosis can occur due to cancer.
A nurse is caring for a client admitted with confusion and lethargy. The client was found at home unresponsive with an empty bottle of aspirin lying next to her bed. Vital signs reveal blood pressure 104/72 mm Hg, heart rate 116/min with regular rhythm, and respiratory rate 42/min and deep. Which of the following arterial blood gas findings should the nurse expect? A. pH 7.68PaO2 96 mm Hg PaCO2 38 mm Hg HCO3− 28 mEq/L B. pH 7.48PaO2 100 mm Hg PaCO2 28 mm Hg HCO3− 23 mEq/L C. pH 6.98PaO2 100 mm Hg PaCO2 30 mm Hg HCO3− 18 mEq/L D. pH 7.58PaO2 96 mm Hg PaCO2 38 mm Hg HCO3− 29 mEq/L
C.CORRECT: An aspirin overdose would result in arterial blood gas findings of metabolic acidosis. A.These arterial blood gases indicate metabolic alkalosis. B.These arterial blood gases indicate respiratory alkalosis. D.These arterial blood gases indicate metabolic alkalosis.
