Acid Base Practice Prep-U
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? a) Respiratory acidosis b) Respiratory alkalosis c) Metabolic acidosis d) Metabolic alkalosis
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 with a suspected overdose of an unknown drug is admitted to the emergency department. Arterial blood gas values indicate respiratory acidosis. What should the nurse do first? a) Prepare for gastric lavage. b) Prepare to assist with ventilation. c) Monitor the client's heart rhythm. d) Obtain a urine specimen for drug screening.
Prepare to assist with ventilation. Explanation: Respiratory acidosis is associated with hypoventilation; in this client, hypoventilation suggests intake of a drug that has suppressed the brain's respiratory center. Therefore, the nurse should assume the client has respiratory depression and should prepare to assist with ventilation. After the client's respiratory function has been stabilized, the nurse can safely monitor the heart rhythm, prepare for gastric lavage, and obtain a urine specimen for drug screening.
Which of the following arterial blood gas results would be consistent with metabolic alkalosis? a) pH 7.26 b) pH 7.30 c) Serum bicarbonate of 21 mEq/L d) Serum bicarbonate of 28 mEq/L
Serum bicarbonate of 28 mEq/L Explanation: Evaluation of arterial blood gases reveals a pH greater than 7.45 and a serum bicarbonate concentration greater than 26 mEq/L.
You are the nurse caring for a 77-year-old male who fell off his roof. You note that the patient's labs indicate minimally elevated serum creatinine levels. What can this indicate in older adults? a) Increased cardiac function b) Substantially reduced renal function c) Reduced respiratory function d) Alterations in ratio of body fluids to muscle mass
Substantially reduced renal function Explanation: Normal physiologic changes of aging, including reduced cardiac, renal, and respiratory function and reserve and alterations in the ratio of body fluids to muscle mass, may alter the responses of elderly people to fluid and electrolyte changes and acid-base disturbances. Renal function declines with age, as do muscle mass and daily exogenous creatinine production. Therefore, high-normal and minimally elevated serum creatinine values may indicate substantially reduced renal function in older adults.
A client recovering from an acute asthma attack experiences respiratory alkalosis. The nurse measures a respiratory rate of 46 breaths/minute, a heart rate of 110 beats/minute, a blood pressure of 162/90 mm Hg, and a temperature of 98.6° F (37° C). To help correct respiratory alkalosis, the nurse should: a) administer acetaminophen (Tylenol) as ordered. b) instruct the client to breathe into a paper bag. c) administer antibiotics as ordered. d) insert a nasogastric tube (NG) as ordered.
instruct the client to breathe into a paper bag. Explanation: A client recovering from an acute asthma attack who experiences respiratory alkalosis should breathe into a paper bag to increase arterial carbon dioxide tension and ease anxiety (which may exacerbate the alkalosis). An NG tube would be indicated for a client with metabolic alkalosis secondary to ingestion of toxic substances; there is no reason to believe that this has occurred. Fever may cause metabolic (not respiratory) alkalosis and would be treated with acetaminophen. A client with sepsis also may have metabolic alkalosis and probably would receive antibiotics; however, this clinical situation doesn't suggest sepsis.
When evaluating arterial blood gases (ABGs), which value is consistent with metabolic alkalosis? a) HCO 21 mEq/L b) pH 7.48 c) PaCO 36 d) O saturation 95%
pH 7.48 Correct Explanation: Metabolic alkalosis is a clinical disturbance characterized by a high pH and high plasma bicarbonate concentration. The HCO value is below normal. The PaCO value and the oxygen saturation level are within a normal range
A client admitted with acute anxiety has the following arterial blood gas (ABG) values: pH, 7.55; partial pressure of arterial oxygen (PaO2), 90 mm Hg; partial pressure of arterial carbon dioxide (PaCO2), 27 mm Hg; and bicarbonate (HCO3-), 24 mEq/L. Based on these values, the nurse suspects: a) respiratory acidosis. b) metabolic alkalosis. c) metabolic acidosis. d) respiratory alkalosis.
respiratory alkalosis. Explanation: This client's above-normal pH value indicates alkalosis. The below-normal PaCO2 value indicates acid loss via hyperventilation; this type of acid loss occurs only in respiratory alkalosis. These ABG values wouldn't occur in metabolic acidosis, respiratory acidosis, or metabolic alkalosis.
A client hospitalized for treatment of a pulmonary embolism develops respiratory alkalosis. Which clinical findings commonly accompany respiratory alkalosis? a) Abdominal pain or diarrhea b) Hallucinations or tinnitus c) Nausea or vomiting d) Light-headedness or paresthesia
Light-headedness or paresthesia Explanation: The client with respiratory alkalosis may complain of light-headedness or paresthesia (numbness and tingling in the arms and legs). Nausea, vomiting, abdominal pain, and diarrhea may accompany respiratory acidosis. Hallucinations and tinnitus rarely are associated with respiratory alkalosis or any other acid-base imbalance.
Which intervention is most appropriate for a client with an arterial blood gas (ABG) of pH 7.5, a partial pressure of arterial carbon dioxide (PaCO2) of 26 mm Hg, oxygen (O2) saturation of 96%, bicarbonate (HCO3-) of 24 mEq/L, and a PaO2 of 94 mm Hg? a) Offer the client fluids frequently. b) Administer an ordered decongestant. c) Administer ordered supplemental oxygen. d) Instruct the client to breathe into a paper bag.
Instruct the client to breathe into a paper bag. Explanation: The ABG results reveal respiratory alkalosis. The best intervention to raise the PaCO2 level would be to have the client breathe into a paper bag. Administering a decongestant, offering fluids frequently, and administering supplemental oxygen wouldn't raise the lowered PaCO2 level.
A patient diagnosed with diabetic ketoacidosis would be expected to have which type of respiratory pattern? a) Apnea b) Kussmaul respirations c) Cheyne-Stokes d) Biot's respirations
Kussmaul respirations Explanation: Kussmaul respirations are seen in patients with diabetic ketoacidosis. In Cheyne-Stokes respiration, rate and depth increase, then decrease until apnea occurs. Biot's respiration is characterized by periods of normal breathing (3 to 4 breaths) followed by a varying period of apnea (usually 10 to 60 seconds).
You are caring for a 65-year-old male patient admitted to your unit 72 hours ago with pyloric stenosis. A nasogastric tube was placed upon admission has been on low intermittent suction ever since. You notice that the patient's potassium is very low. What would you be concerned that the patient may be at risk for? a) Hypercalcemia b) Metabolic acidosis c) Metabolic alkalosis d) Respiratory acidosis
Metabolic alkalosis Explanation: Probably the most common cause of metabolic alkalosis is vomiting or gastric suction with loss of hydrogen and chloride ions. The disorder also occurs in pyloric stenosis in which only gastric fluid is lost. Vomiting, gastric suction, and pyloric stenosis all remove potassium and can cause hypokalemia. Option A is incorrect; this patient would not be at risk for hypercalcemia; hyperparathyroidism and cancer account for almost all cases of hypercalcemia. Option B is incorrect; the nasogastric tube is removing stomach acid and will likely raise pH. Option D is incorrect; respiratory acidosis is unlikely since there was no change reported in the patient's respiratory status.
A nurse reviews the arterial blood gas (ABG) values of a client admitted with pneumonia: pH, 7.51; PaCO2, 28 mm Hg; PaO2, 70 mm Hg; and HCO3--, 24 mEq/L. What do these values indicate? a) Metabolic alkalosis b) Metabolic acidosis c) Respiratory alkalosis d) Respiratory acidosis
Respiratory alkalosis Explanation: A client with pneumonia may hyperventilate in an effort to increase oxygen intake. Hyperventilation leads to excess carbon dioxide (CO2) loss, which causes alkalosis — indicated by this client's elevated pH value. With respiratory alkalosis, the kidneys' bicarbonate (HCO3-) response is delayed, so the client's HCO3- level remains normal. The below-normal value for the partial pressure of arterial carbon dioxide (PaCO2) indicates CO2 loss and signals a respiratory component. Because the HCO3- level is normal, this imbalance has no metabolic component. Therefore, the client is experiencing respiratory alkalosis
A client with Guillain-Barré syndrome develops respiratory acidosis as a result of reduced alveolar ventilation. Which combination of arterial blood gas (ABG) values confirms respiratory acidosis? a) pH, 7.5; PaCO2 30 mm Hg b) pH, 7.25; PaCO2 50 mm Hg c) pH, 7.40; PaCO2 35 mm Hg d) pH, 7.35; PaCO2 40 mm Hg
pH, 7.25; PaCO2 50 mm Hg Explanation: In respiratory acidosis, ABG analysis reveals an arterial pH below 7.35 and partial pressure of arterial carbon dioxide (PaCO2) above 45 mm Hg. Therefore, the combination of a pH value of 7.25 and a PaCO2 value of 50 mm Hg confirms respiratory acidosis. A pH value of 7.5 with a PaCO2 value of 30 mm Hg indicates respiratory alkalosis. A ph value of 7.40 with a PaCO2 value of 35 mm Hg and a pH value of 7.35 with a PaCO2 value of 40 mm Hg represent normal ABG values, reflecting normal gas exchange in the lungs.
You are caring for a patient admitted with chronic obstructive pulmonary disease. During your shift assessment, you find that your patient is experiencing a change in his respiratory and mental status. You are aware that the most accurate measurement of the concentration of oxygen in the patient's blood is what? a) Assessment of the patient's nailbeds b) A capillary blood sample c) Pulse oximetry d) An arterial blood gas study
An arterial blood gas study Explanation: The arterial oxygen tension (partial pressure or PaO2) indicates the degree of oxygenation of the blood, and the arterial carbon dioxide tension (partial pressure or PaCO2) indicates the adequacy of alveolar ventilation. ABG studies aid in assessing the ability of the lungs to provide adequate oxygen and remove carbon dioxide and the ability of the kidneys to reabsorb or excrete bicarbonate ions to maintain normal body pH. Capillary blood samples are venous blood, not arterial blood, so it is not as accurate as an ABG. Pulse oximetry does not replace ABG measurement as it is not as accurate. Assessment of the patient's nailbeds does not give an accurate measurement of the concentration of oxygen in the blood.
To evaluate a client for hypoxia, the physician is most likely to order which laboratory test? a) Total hemoglobin b) Sputum culture c) Arterial blood gas (ABG) analysis d) Red blood cell count
Arterial blood gas (ABG) analysis Explanation: Red blood cell count, sputum culture, total hemoglobin, and ABG analysis all help evaluate a client with respiratory problems. However, ABG analysis is the only test that evaluates gas exchange in the lungs, providing information about the client's oxygenation status.
A group of nursing students are studying for a test over acid-base imbalance. One student asks another what the major chemical regulator of plasma pH is. What should the second student respond? a) Renin-angiotensin-aldosterone system b) Bicarbonate-carbonic acid buffer system c) Sodium-potassium pump d) ADH-ANP buffer system
Bicarbonate-carbonic acid buffer system Explanation: The major chemical regulator of plasma pH is the bicarbonate-carbonic acid buffer system. Therefore options A and C are incorrect. Option D does not exist, it is only a distractor for this question.
When a client's ventilation is impaired, the body retains which substance? a) Carbon dioxide (CO2) b) Nitrous oxide c) Oxygen d) Sodium bicarbonate
Carbon dioxide (CO2) Explanation: When ventilation is impaired, the body retains CO2 because the carbonic acid level increases in the blood. Sodium bicarbonate is used to treat acidosis. Nitrous oxide, which has analgesic and anesthetic properties, commonly is administered before minor surgical procedures. When ventilation is impaired, the body doesn't retain oxygen. Instead, the tissues use oxygen and CO2 results
When oxygen and carbon dioxide are exchanged between the pulmonary capillaries and the alveoli, which process is used? a) Active transport b) Osmosis c) Filtration d) Diffusion
Diffusion Explanation: Diffusion is the natural tendency of a substance to move from an area of higher concentration to one of lower concentration. It occurs through the random movement of ions and molecules. Examples of diffusion are the exchange of oxygen and carbon dioxide between the pulmonary capillaries and alveoli and the tendency of sodium to move from the ECF compartment, where the sodium concentration is high, to the ICF, where its concentration is low. Osmosis occurs when two different solutions are separated by a membrane that is impermeable to the dissolved substances; fluid shifts through the membrane from the region of low solute concentration to the region of high solute concentration until the solutions are of equal concentration. Active transport implies that energy must be expended for the movement to occur against a concentration gradient. Movement of water and solutes occurring from an area of high hydrostatic pressure to an area of low hydrostatic pressure is filtration.
Which of the following would be a potential cause of respiratory acidosis? a) Diarrhea b) Hypoventilation c) Vomiting d) Hyperventilation
Hypoventilation Explanation: Respiratory acidosis is always due to inadequate excretion of CO, with inadequate ventilation, resulting in elevated plasma CO concentration, which causes increased levels of carbonic acid. In addition to an elevated PaCO, hypoventilation usually causes a decrease in PaO.
A client has the following arterial blood gas (ABG) values: pH, 7.12; partial pressure of arterial carbon dioxide (PaCO2), 40 mm Hg; and bicarbonate (HCO3-), 15 mEq/L. These ABG values suggest which disorder? a) Metabolic alkalosis b) Metabolic acidosis c) Respiratory alkalosis d) Respiratory acidosis
Metabolic acidosis Explanation: This client's pH value is below normal, indicating acidosis. The HCO3- value also is below normal, reflecting an overwhelming accumulation of acids or excessive loss of base, which suggests metabolic acidosis. The PaCO2 value is normal, indicating absence of respiratory compensation. These ABG values eliminate respiratory alkalosis, respiratory acidosis, and metabolic alkalosis.
A patient in the ICU starts complaining of being "short of breath." An arterial blood gas (ABG) is drawn. The ABG has the following values: pH = 7.21, PaCO2 = 64 mm Hg, HCO3 = 24 mm Hg. What does the ABG reflect? a) Respiratory acidosis b) Metabolic alkalosis c) Respiratory alkalosis d) Metabolic acidosis
Respiratory acidosis Explanation: The pH below 7.40, PaCO2 greater than 40, and the HCO3 is normal; therefore, it is a respiratory acidosis, and compensation by the kidneys has not begun, which indicates this was probably an acute event. Option B is incorrect; the HCO3 of 24 is within the normal range so it is not metabolic alkalosis. Option C is incorrect; the pH of 7.21 indicates an acidosis, not alkalosis. Option D is incorrect; the pH of 7.21 indicates it is an acidosis but the HCO3 of 24 is within the normal range so it is not a metabolic acidosis.
A client comes to the emergency department with status asthmaticus. His respiratory rate is 48 breaths/minute, and he is wheezing. An arterial blood gas analysis reveals a pH of 7.52, a partial pressure of arterial carbon dioxide (PaCO2) of 30 mm Hg, PaO2 of 70 mm Hg, and bicarbonate (HCO3??') of 26 mEq/L. What disorder is indicated by these findings? a) Metabolic alkalosis b) Respiratory acidosis c) Respiratory alkalosis d) Metabolic acidosis
Respiratory alkalosis Explanation: Respiratory alkalosis results from alveolar hyperventilation. It's marked by a decrease in PaCO2 to less than 35 mm Hg and an increase in blood pH over 7.45. Metabolic acidosis is marked by a decrease in HCO3? to less than 22 mEq/L, and a decrease in blood pH to less than 7.35. In respiratory acidosis, the pH is less than 7.35 and the PaCO2 is greater than 45 mm Hg. In metabolic alkalosis, the HCO3? is greater than 26 mEq/L and the pH is greater than 7.45.
A patient with anxiety presents to the emergency room. The triage nurse notes upon assessment that the patient is hyperventilating. The triage nurse is aware that hyperventilation is the most common cause of which acid-base imbalance? a) CNS disturbances b) Respiratory alkalosis c) Respiratory acidosis d) Increased PaCO2
Respiratory alkalosis Explanation: The most common cause of acute respiratory alkalosis is hyperventilation. Extreme anxiety can lead to hyperventilation. Acute respiratory acidosis occurs in emergency situations such as pulmonary edema and is exhibited by hypoventilation and decreased PaCO2. CNS disturbances are found in extreme hyponatremia and fluid overload.
Which set of arterial blood gas (ABG) results requires further investigation? a) pH 7.38, partial pressure of arterial carbon dioxide (PaCO2) 36 mm Hg, partial pressure of arterial oxygen (PaO2) 95 mm Hg, bicarbonate (HCO3-) 24 mEq/L b) pH 7.35, PaCO2 40 mm Hg, PaO2 91 mm Hg, and HCO3- 22 mEq/L c) pH 7.44, PaCO2 43 mm Hg, PaO2 99 mm Hg, and HCO3- 26 mEq/L d) pH 7.49, PaCO2 30 mm Hg, PaO2 89 mm Hg, and HCO3- 18 mEq/L
pH 7.49, PaCO2 30 mm Hg, PaO2 89 mm Hg, and HCO3- 18 mEq/L Explanation: The ABG results pH 7.49, PaCO2 30 mm Hg, PaO2 89 mm Hg, and HCO3- 18 mEq/L indicate respiratory alkalosis. The pH level is increased, and the HCO3- and PaCO2 levels are decreased. Normal values are pH 7.35 to 7.45; PaCO2 35 to 45 mm Hg; HCO3- 22 to 26 mEq/L.
You are caring for a client who is in respiratory distress. The physician orders arterial blood gases (ABGs) to determine various factors related to blood oxygenation. What site can ABGs be obtained from? a) The pleural surfaces b) The trachea and bronchi c) A catheter in the arm vein d) A puncture at the radial artery
A puncture at the radial artery Explanation: ABGs determine the blood's pH, oxygen-carrying capacity, levels of oxygen, CO2, and bicarbonate ion. Blood gas samples are obtained through an arterial puncture at the radial, brachial, or femoral artery. A client also may have an indwelling arterial catheter from which arterial samples are obtained. Blood gas samples are not obtained from the pleural surfaces or trachea and bronchi.
