ABGs

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1

4. A patient with a longstanding diagnosis of generalized anxiety disorder 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) Respiratory acidosis
B) Respiratory alkalosis
C) Increased PaCO2
D) CNS disturbances

Ans: B
Feedback:
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.

2

5. You are an emergency-room nurse caring for a trauma patient. Your patient has the following arterial blood gas results: pH 7.26, PaCO2 28, HCO3 11 mEq/L. How would you interpret these results?
A) Respiratory acidosis with no compensation
B) Metabolic alkalosis with a compensatory alkalosis
C) Metabolic acidosis with no compensation
D) Metabolic acidosis with a compensatory respiratory alkalosis

Ans: D
Feedback:
A low pH indicates acidosis (normal pH is 7.35 to 7.45). The PaCO3 is also low, which causes alkalosis. The bicarbonate is low, which causes acidosis. The pH bicarbonate more closely corresponds with a decrease in pH, making the metabolic component the primary problem.

3

12. You are caring for a 65-year-old male patient admitted to your medical unit 72 hours ago with pyloric stenosis. A nasogastric tube placed upon admission has been on low intermittent suction ever since. Upon review of the morning’s blood work, you notice that the patient’s potassium is below reference range. You should recognize that the patient may be at risk for what imbalance?
A) Hypercalcemia
B) Metabolic acidosis
C) Metabolic alkalosis
D) Respiratory acidosis

12. You are caring for a 65-year-old male patient admitted to your medical unit 72 hours ago with pyloric stenosis. A nasogastric tube placed upon admission has been on low intermittent suction ever since. Upon review of the morning’s blood work, you notice that the patient’s potassium is below reference range. You should recognize that the patient may be at risk for what imbalance?
A) Hypercalcemia
B) Metabolic acidosis
C) Metabolic alkalosis
D) Respiratory acidosis

4

14. A patient who is being treated for pneumonia starts complaining of sudden shortness 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

Ans: A
Feedback:
The pH is below 7.40, PaCO2 is 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. The HCO3 of 24 is within the normal range so it is not metabolic alkalosis. The pH of 7.21 indicates an acidosis, not alkalosis. The pH of 7.21 indicates it is an acidosis but the HCO3 of 24 is within the normal range, ruling out metabolic acidosis.

5

28. A medical nurse educator is reviewing a patient’s recent episode of metabolic acidosis with members of the nursing staff. What should the educator describe about the role of the kidneys in metabolic acidosis?
A) The kidneys retain hydrogen ions and excrete bicarbonate ions to help restore balance.
B) The kidneys excrete hydrogen ions and conserve bicarbonate ions to help restore balance.
C) The kidneys react rapidly to compensate for imbalances in the body.
D) The kidneys regulate the bicarbonate level in the intracellular fluid.

Ans: B
Feedback:
The kidneys regulate the bicarbonate level in the ECF; they can regenerate bicarbonate ions as well as reabsorb them from the renal tubular cells. In respiratory acidosis and most cases of metabolic acidosis, the kidneys excrete hydrogen ions and conserve bicarbonate ions to help restore balance. In respiratory and metabolic alkalosis, the kidneys retain hydrogen ions and excrete bicarbonate ions to help restore balance. The kidneys obviously cannot compensate for the metabolic acidosis created by renal failure. Renal compensation for imbalances is relatively slow (a matter of hours or days).

6

29. The nurse in the medical ICU is caring for a patient who is in respiratory acidosis due to inadequate ventilation. What diagnosis could the patient have that could cause inadequate ventilation?
A) Endocarditis
B) Multiple myeloma
C) Guillain-Barré syndrome
D) Overdose of amphetamines

Ans: C
Feedback:
Respiratory acidosis is always due to inadequate excretion of CO2 with inadequate ventilation, resulting in elevated plasma CO2 concentrations and, consequently, increased levels of carbonic acid. Acute respiratory acidosis occurs in emergency situations, such as acute pulmonary edema, aspiration of a foreign object, atelectasis, pneumothorax, overdose of sedatives, sleep apnea, administration of oxygen to a patient with chronic hypercapnia (excessive CO2 in the blood), severe pneumonia, and acute respiratory distress syndrome. Respiratory acidosis can also occur in diseases that impair respiratory muscles, such as muscular dystrophy, myasthenia gravis, and Guillain-Barré syndrome. The other listed diagnoses are not associated with respiratory acidosis.

7

30. The ICU nurse is caring for a patient who experienced trauma in a workplace accident. The patient is complaining of having trouble breathing with abdominal pain. An ABG reveals the following results: pH 7.28, PaCO2 50 mm Hg, HCO3– 23 mEq/L. The nurse should recognize the likelihood of what acid–base disorder?
A) Respiratory acidosis
B) Metabolic alkalosis
C) Respiratory alkalosis
D) Mixed acid–base disorder

Ans: D
Feedback:
Patients can simultaneously experience two or more independent acid–base disorders. A normal pH in the presence of changes in the PaCO2 and plasma HCO3– concentration immediately suggests a mixed disorder, making the other options incorrect.

8

35. The nurse is caring for a patient in metabolic alkalosis. The patient has an NG tube to low intermittent suction for a diagnosis of bowel obstruction. What drug would the nurse expect to find on the medication orders?
A) Cimetidine
B) Maalox
C) Potassium chloride elixir
D) Furosemide

Ans: A
Feedback:
H2 receptor antagonists, such as cimetidine (Tagamet), reduce the production of gastric HCl, thereby decreasing the metabolic alkalosis associated with gastric suction. Maalox is an oral simethicone used to break up gas in the GI system and would be of no benefit in treating a patient in metabolic alkalosis. KCl would only be given if the patient were hypokalemic, which is not stated in the scenario. Furosemide (Lasix) would only be given if the patient were fluid overloaded, which is not stated in the scenario.

9

The ICU nurse is caring for a patient who experienced trauma in a workplace accident. The patient is complaining of having trouble breathing with abdominal pain. An ABG reveals the following results: pH 7.28, PaCO2 50 mm Hg, HCO3– 23 mEq/L. The nurse should recognize the likelihood of what acid–base disorder?
A) Respiratory acidosis
B) Metabolic alkalosis
C) Respiratory alkalosis
D) Mixed acid–base disorder

Ans:D
Feedback:
Patients can simultaneously experience two or more independent acid–base disorders. A normal pH in the presence of changes in the PaCO2 and plasma HCO3– concentration immediately suggests a mixed disorder, making the other options incorrect.

10

The nurse is analyzing the arterial blood gas (AGB) results of a patient diagnosed with severe pneumonia. Which of the following ABG results indicates respiratory acidosis
A)pH: 7.20, PaCO2: 65 mm Hg, HCO3-: 26 mEq/L
B)pH: 7.32, PaCO2: 40mm Hg, HCO3-: 18 mEq/l
C)pH: 7.50, PaCO2: 30 mm Hg, and HCO3-: 24 mEq/L
D)pH 7.42, PaCO2: 45 mm Hg, and HCO3-: 22 mEq/L

Ans: A

Respiratory acidosis is a clinical disorder in which the pH is less than 7.35 and the PaCO2 is greater than 42mm Hg and a compensatory increase in the plasma HCO3- occurs. It may be either acute or chronic. The ABG of pH: 7.32, PaCO2: 40mm Hg, HCO3-: 18 mEq/l indicates metabolic acidosis. The ABGs of pH: 7.50, PaCO2: 30 mm Hg, and HCO3-: 24 mEq/L indicate respiratory alkalosis. The ABGs of pH 7.42, PaCO2: 45 mm Hg, and HCO3-: 22 mEq/L indicate a normal result/ no imbalance.

11

The nurse is caring for a patient with severe diarrhea. The nurse recognizes that the patient is at-risk for developing which of the following acid-base imbalances?
a) Respiratory acidosis
b) Metabolic alkalosis
c) Respiratory alkalosis
d) Metabolic acidosis

Ans: D

The patient is at risk for developing metabolic acidosis. Metabolic acidosis is caused by diarrhea, lower intestinal fistulas, ureterostomies, and use of diuretics; early renal insufficiency; excessive administration of chloride; and the administration of parenteral nutrition without bicarbonate or bicarbonate-producing solutes (e.g. lactate)

12

A patient presents to the Emergency Department experiencing a severe anxiety attack and is hyperventilating. The nurse would expect the patient's pH value to be which of the following?
a) 7.35
b) 7.30
c) 7.45
d) 7.50

Ans: D
The patient is experiencing respiratory alkalosis. Respiratory alkalosis is a clinical condition in which the arterial pH is greater than 7.45 and the PaCOs is less than 38 mm Hg. Respiratory alkalosis is always caused by hyperventilation, which causes excessive "blow off" of COs and , hence, a decrease in the plasma carbonic acid concentration. Causes include extreme anxiety, hypoxemia, early phase of salicylate intoxication, Gram-negative bacteremia, and inappropriate ventilator settings.

13

Which of the following arterial blood gas (ABG) results would the nurse anticipate for a patient with a 3-day history of vomiting?
a) A)pH: 7.55, PaCO2: 60 mm Hg, HCO3-: 28 mEq/L
B)pH: 7.28, PaCO2: 25mm Hg, HCO3-: 15 mEq/l
C)pH: 7.34, PaCO2: 60 mm Hg, and HCO3-: 34 mEq/L
D)pH 7.45, PaCO2: 32 mm Hg, and HCO3-: 21 mEq/L

Ans: A
The patient's ABG would likely demonstrate metabolic alkalosis. Metabolic alkalosis is a clinical disturbance characterized by a high pH (decreased H= concentration) and a high plasma bicarbonate concentration. It can be produced by a gain of HCO3 or a loss of H+. A common cause of metabolic alkalosis is vomiting or gastric suction with loss of hydrogen and chloride ions. The disorder also occurs in pyloric stenosis where only gastric fluid is lost. The other results do not

14

The nurse is caring for a patient with a metabolic acidosis (pH 7.25). Which of the following values is useful to the nurse in determining whether the cause of the acidosis is due to acid gain or to bicarbonate loss?
a) Anion Gap
b)Bicarbonate level
c)Serum Sodium level
d) PaCO2

Ans: A
Metabolic acidosis is a common clinical disturbance characterized by a low pH (increased H= concentration) and a low plasma bicarbonate concentration. It can be produced by a gain of hydrogen ion or a loss of bicarbonate. It can be divided clinically into two forms, according to the values of the serum anion gap: high anion gap acidosis and normal anion gap acidosis. A patient diagnosed with metabolic acidosis is determined to have normal anion gap metabolic acidosis if the anion gap is within this normal range.

15

Which of the following is required before obtaining a blood sample for ABG analysis?

a) Isolation precautions
b) Coagulation values
c) Weaning parameters
d) Mixed venous oxygen results

Ans: B
Coagulation values must be evaluated before the nurse obtains a blood sample for ABG analysis. These values help determine the ability to obtain hemostasis at the arterial puncture site after the sample is obtained. The nurse should assess the patient’s current anticoagulation therapy, known blood dyscrasias, and pertinent laboratory results (e.g., platelets, PTT, and PT or INR) before the procedure. Isolation precautions are important for personal protection but should not affect blood gas sample collection. Weaning parameters are used to evaluate oxygen therapy but do not affect blood gas sample collection. Mixed venous oxygen results are not obtained from a peripheral arterial blood sample.

16

Which of the following complications is least likely to result from an arterial puncture?

a) Change in vital signs
b) Loss of peripheral sensation
c) Elevated CO2 level
d) Erythema at the site

Ans: C

Rationale:
An elevated CO2 level is typically not a complication of an arterial puncture. Rather, it is a finding of ABG analysis. A change in the patient’s vital signs may indicate excessive bleeding from the puncture site. A loss of sensation can be caused by neurovascular compromise of the extremity distal to the puncture site. Erythema at the puncture site may be a sign of local infection.

17

The nurse attempts an arterial puncture on a patient but is unsuccessful. Which of the following is the nurse’s next best action?

  1. Apply ice to the puncture site, advance the needle farther, and apply pressure.
  2. Withdraw the needle slightly, angle it slightly toward the artery, and readvance it.
  3. Advance the needle farther, wait for flashback, and then angle the needle.
  4. Withdraw the needle, dispose of the needle, and restart the procedure with a new needle.

Ans: 2

Rationale:
If the puncture is unsuccessful, the needle should be withdrawn to just below the skin level, angled slightly toward the artery, and readvanced. Applying ice, advancing the needle, waiting for flashback, and applying pressure are not appropriate nursing actions because they may harm the patient and do not ensure a successful puncture. The needle should not be withdrawn entirely from the patient, but instead the nurse should try to withdraw the needle slightly and reangle it to achieve the proper position.

18

The nurse has the needle positioned deep under the patient’s skin during an arterial puncture. The nurse knows that changing the angle of the needle will most likely result in which of the following complications?

  1. Blood clot
  2. Laceration
  3. Abrasion
  4. Hematoma

Ans: 2 Laceration

Rationale:
Changing the angle of the needle while it is deep under the skin can cause a laceration of tissue, veins, muscle, nerves, and even the periosteum. This action does not result in a blood clot or abrasion. A hematoma is possible, but the laceration is most common and would be the root cause of the hematoma.

19

A patient who is on mechanical ventilation is scheduled for an ABG blood draw. How long should the nurse wait before obtaining the ABG samples?

  1. 10 to 15 minutes
  2. 20 to 30 minutes
  3. 30 minutes to 1 hour
  4. 24 hours

Ans: 2 20 to 30 minutes

Rationale:

If the patient is receiving oxygen or is on mechanical ventilation, the nurse must ensure that the current therapy has been underway for 20 to 30 minutes before obtaining ABG samples. Waiting 10 to 15 minutes is not adequate. Waiting 30 minutes to 1 hour or waiting 24 hours is excessive.

20

The patient is receiving sodium bicarbonate intravenously (IV) for correction of acidosis secondary to diabetic coma. The nurse assesses cyanosis, slow respirations, and irregular pulse. What is the nurse’s priority action?

1. Increase the rate of the infusion and continue to assess the patient for symptoms of acidosis.
2. Decrease the rate of the infusion and continue to assess the patient for symptoms of alkalosis.
3. Continue the infusion; the patient is still in acidosis.
4. Stop the infusion and notify the physician; the patient is in alkalosis.

Ans: 4

Rationale 4: The patient receiving sodium bicarbonate is prone to alkalosis; monitor for cyanosis, slow respirations, and irregular pulse. The patient’s symptoms indicate alkalosis so infusion must be stopped and the physician notified. The patient is not in acidosis, symptoms of acidosis include lethargy, confusion, CNS depression leading to coma, and a deep, rapid respiration rate that indicates an attempt by the lungs to rid the body of excess acid. The patient is not in acidosis, so the infusion must be stopped, not increased. The infusion must be stopped, not decreased, as the patient is in alkalosis.

21

Potential causes for respiratory alkalosis include

1. hypotension.

2. hypertension.

3. hypoventilation.

4. hyperventilation.

Ans: 4

Hyperventilation occurs with respiratory alkalosis.

22

The nurse is caring for a patient with a pH of 7.32. Which medications would be appropriate to administer to a patient with this condition?
Standard Text: Select all that apply.

1. Oral bicarbonate

2. Sodium chloride

3. Citrate salts

4. Potassium chloride

5. Ammonium chloride

Correct Answer: 1,3

Rationale 1: Oral bicarbonate is an agent used to treat acidosis.
Rationale 2: Sodium chloride is an agent used to treat alkalosis.
Rationale 3: Citrate salts are an agent used to treat acidosis.
Rationale 4: Potassium chloride is an agent used to treat alkalosis.
Rationale 5: Potassium chloride is an agent used to treat alkalosis.

23

11.A 2-year-old child is brought into the emergency department after ingesting a medication that causes respiratory depression. For which acid-base imbalance will the nurse most closely monitor this child?
a. Respiratory alkalosis
b. Respiratory acidosis
c. Metabolic acidosis
d. Metabolic alkalosis

ANS: B
Respiratory depression leads to hypoventilation. Hypoventilation results in retention of CO2 and respiratory acidosis. Respiratory alkalosis would result from hyperventilation, causing a decrease in CO2 levels. Metabolic acid-base imbalance would be a result of kidney dysfunction, vomiting, diarrhea, or other conditions that affect metabolic acids.

24

A patient is admitted for a bowel obstruction and has had a nasogastric tube set to low intermittent suction for the past 3 days. Which arterial blood gas values will the nurse expect to observe?
a. Respiratory alkalosis
b. Metabolic alkalosis
c. Metabolic acidosis
d. Respiratory acidosis

ANS: B
The patient is losing acid from the nasogastric tube so the patient will have metabolic alkalosis. Lung problems will produce respiratory alkalosis or acidosis. Metabolic acidosis will occur when too much acid is in the body like kidney failure.

25

13.Which blood gas result will the nurse expect to observe in a patient with respiratory alkalosis?
a. pH 7.60, PaCO2 40 mm Hg, HCO3– 30 mEq/L
b. pH 7.53, PaCO2 30 mm Hg, HCO3– 24 mEq/L
c. pH 7.35, PaCO2 35 mm Hg, HCO3– 26 mEq/L
d. pH 7.25, PaCO2 48 mm Hg, HCO3– 23 mEq/L

ANS: B
Respiratory alkalosis should show an alkalotic pH and decreased CO2 (respiratory) values, with a normal HCO3–. In this case, pH 7.53 is alkaline (normal = 7.35 to 7.45), PaCO2 is 30 (normal 35 to 45 mm Hg), and HCO3– is 24 (normal = 22 to 26 mEq/L). A result of pH 7.60, PaCO2 40 mm Hg, HCO3– 30 mEq/L is metabolic alkalosis. pH 7.35, PaCO2 35 mm Hg, HCO3– 26 mEq/L is within normal limits. pH 7.25, PaCO2 48 mm Hg, HCO3– 23 mEq/L is respiratory acidosis.

26

16.A patient is experiencing respiratory acidosis. Which organ system is responsible for compensation in this patient?
a. Renal
b. Endocrine
c. Respiratory
d. Gastrointestinal

ANS: A
The kidneys (renal) are responsible for respiratory acidosis compensation. A problem with the respiratory system causes respiratory acidosis, so another organ system (renal) needs to compensate. Problems with the gastrointestinal and endocrine systems can cause acid-base imbalances, but these systems cannot compensate for an existing imbalance.

27

18.The nurse is caring for a diabetic patient in renal failure who is in metabolic acidosis. Which laboratory findings are consistent with metabolic acidosis?
a. pH 7.3, PaCO2 36 mm Hg, HCO3– 19 mEq/L
b. pH 7.5, PaCO2 35 mm Hg, HCO3– 35 mEq/L
c. pH 7.32, PaCO2 47 mm Hg, HCO3– 23 mEq/L
d. pH 7.35, PaCO2 40 mm Hg, HCO3– 25 mEq/L

ANS: A
The laboratory values that reflect metabolic acidosis are pH 7.3, PaCO2 36 mm Hg, HCO3– 19 mEq/L. A laboratory finding of pH 7.5, PaCO2 35 mm Hg, HCO3– 35 mEq/L is metabolic alkalosis. pH 7.32, PaCO2 47 mm Hg, HCO3– 23 mEq/L is respiratory acidosis. pH 7.35, PaCO2 40 mm Hg, HCO3– 25 mEq/L values are within normal range.