ABG Analysis NCLEX Exam Part II





ABG Analysis NCLEX Exam Part II

Arterial Blood – Gas Answer and Rationale

1. A mother is admitted in the emergency department following complaints of fever and chills. The nurse on duty took her vital signs and noted the following: Temp = 100 °F; apical pulse = 95; respiration = 20 and deep. Measurement of arterial blood gas shows pH 7.37, PaO2 90 mm Hg, PaCO2 40 mm Hg, and HCO3 24 mmol/L. What is your assessment?

A. Hypothermia and Respiratory Alkalosis

B. Hypothermia

C. Hyperthermia and Respiratory Alkalosis

D. Hyperthermia

Correct Answer D. An individual is considered to have hyperthermia if he or she has a temperature of >37.5 or 38.3 °C (99.5 or 100.9 °F). Measurement of arterial blood gases are normal.

2. A young woman is found comatose, having taken an unknown number of sleeping pills an unknown time before. An arterial blood sample yields the following values: pH 6.90, HCO3- 13 meq/liter and PaCO2 68 mmHg. This patient’s acid-base status is most accurately described as:

A. Respiratory Acidosis with Complete Renal Compensation

B. Metabolic Acidosis

C. Respiratory Acidosis

D. Simultaneous Respiratory and Metabolic Acidosis

Correct Answer D. Whenever the PCO2 and HCO3 are abnormal in opposite directions, ie, one above normal while the other is reduced, a mixed respiratory and metabolic acid-base disorder exists. When the PCO2 is elevated and the [HCO3-] reduced, respiratory acidosis and metabolic acidosis coexist.

3. A mountaineer attempts an assault on a high mountain in the Andes and reaches an altitude of 5000 meters (16,400 ft) above sea level. What will happen to his arterial PCO2 and pH?

A. The pH will rise and PCO2 will fall.

B. Both will be lower than normal.

C. The pH will fall and PCO2 will rise

D. Both will be higher than normal due to the physical exertion

Correct Answer A. The mountaineer will suffer from a respiratory alkalosis. The decline in the PO2 with altitude will stimulate breathing to offset the hypoxia. Carbon dioxide is driven from the blood faster than it is produced in the tissues so PCO2 falls and pH rises.

4. In a patient undergoing surgery, it was vital to aspirate the contents of the upper gastrointestinal tract. After the operation, the following values were acquired from an arterial blood sample: pH 7.55, PCO2 52 mm Hg and HCO3- 40 mmol/l. What is the underlying disorder?

A. Respiratory Acidosis

B. Respiratory Alkalosis

C. Metabolic Acidosis

D. Metabolic Alkalosis

Correct Answer D.NGT suctioning, vomiting, hypokalemia and overdosage of NaHCO3 are considered risk factors of metabolic alkalosis.

5. An old man was admitted to hospital in a coma. Analysis of the arterial blood gave the following values: PCO2 16 mm Hg, HCO3- 5 mmol/L and pH 7.1. As a well-rounded nurse, you know that the normal value for HCO3 is:

A. 20 mmol/L

B. 29 mmol/L

C. 31 mmol/L

D. 24 mmol/L

Correct Answer D. The normal value for bicarbonate (HCO3) is 22-26 mmol/L or mEq/L. It may vary slightly among different laboratories. The given values show the common measurement range of results for these tests. Some laboratories use different measurements or may test different specimens.

6. A company driver is found at the scene of an automobile accident in a state of emotional distress. He tells the paramedics that he feels dizzy, tingling in his fingertips, and does not remember what happened to his car. Respiratory rate is rapid at 34/minute. Which primary acid-base disturbance is the young man at risk for if medical attention is not provided?

A. Respiratory Alkalosis

B. Respiratory Acidosis

C. Metabolic Acidosis

D. Metabolic Alkalosis

Correct Answer A. Hyperventilation is typically the underlying cause of respiratory alkalosis. Hyperventilation is also known as overbreathing. When someone is hyperventilating, they tend to breathe very deeply or very rapidly.

7.A patient who is hospitalized due to vomiting and a decreased level of consciousness displays slow and deep (Kussmaul breathing), and he is lethargic and irritable in response to stimulation. The doctor diagnosed him of having dehydration. Measurement of arterial blood gas shows pH 7.0, PaO2 90 mm Hg, PaCO2 22 mm Hg, and HCO3 14 mmol/L; other results are Na+ 120 mmol/L, K+ 2.5 mmol/L, and Cl- 95 mmol/L. As a knowledgeable nurse, you know that the normal value for PaCO2 is:

A. 36 mm Hg

B. 22 mm Hg

C. 48 mm Hg

D. 50 mm Hg

Correct Answer A. The normal range for PaCO2 is from 35 to 45 mm Hg.

8. Liza’s mother is seen in the emergency department at a community hospital. She admits that her mother is taking many tablets of aspirin (salicylates) over the last 24-hour period because of a severe headache. Also, the mother complains of an inability to urinate. The nurse on duty took her vital signs and noted the following: Temp = 97.8 °F; apical pulse = 95; respiration = 32 and deep. Which primary acid-base imbalance is the client at risk for if medical attention is not provided?

A. Metabolic Acidosis

B. Respiratory Acidosis

C. Respiratory Alkalosis

D. Metabolic Alkalosis

Correct Answer A. Salicylate overdose causes a high anion gap metabolic acidosis in both children and adults. Adults commonly develop a mixed acid-base disorder as a respiratory alkalosis due to direct respiratory centre stimulation occurs as well. This second disorder is uncommon in children.

9. An old beggar was admitted to the emergency department due to shortness of breath, fever, and a productive cough. Upon examination, crackles and wheezes are noted in the lower lobes; he appears to be tachycardic and has a bounding pulse. Measurement of arterial blood gas shows pH 7.2, PaCO2 66 mm Hg, HCO3 27 mmol/L, and PaO2 65 mm Hg. As a knowledgeable nurse, you know that the normal value for pH is:

A. 7.20

B. 7.30

C. 7.50

D. 7.40

Correct Answer D. Normal blood pH must be maintained within a narrow range of 7.35-7.45 to ensure the proper functioning of metabolic processes and the delivery of the right amount of oxygen to tissues. Acidosis refers to an excess of acid in the blood that causes the pH to fall below 7.35, and alkalosis refers to an excess of base in the blood that causes the pH to rise above 7.45.

10. Dave, a 6-year-old boy, was rushed to the hospital following her mother’s complaint that her son has been vomiting, nauseated and has overall weakness. After series of tests, the nurse notes the laboratory results: potassium: 2.9 mEq. Which primary acid-base imbalance is this boy at risk for if medical intervention is not carried out?

A. Metabolic Alkalosis

B. Respiratory Acidosis

C. Respiratory Alkalosis

D. Metabolic Acidosis

Correct Answer A. Vomiting, hypokalemia, overdosage of NaHCO3 and NGT suctioning are considered risk factors of metabolic alkalosis.

11. pH 7.4, PaCO2 59, HCO3- 35.

A. Respiratory Acidosis, Uncompensated

B. Metabolic Alkalosis, Uncompensated

C. Metabolic Alkalosis, Partially Compensated

D. Respiratory Acidosis, Fully Compensated

Correct Answer D.

12. pH 7.5, PaCO2 19, HCO3- 22

A. Respiratory Alkalosis, Uncompensated

B. Respiratory Alkalosis, Partially Compensated

C. Metabolic Alkalosis, Partially Compensated

D. Respiratory Acidosis, Uncompensated

Correct Answer A

13. pH 7.6, PaCO2 53, HCO3- 38

A. Metabolic Alkalosis, Fully Compensated

B. Metabolic Alkalosis, Partially Compensated

C. Respiratory Acidosis, Partially Compensated

D. Respiratory Alkalosis, Fully Compensated

Correct Answer B

14. pH 7.45, PaCO2 50, HCO3- 30

A. Respiratory Acidosis, Partially Compensated

B. Metabolic Alkalosis, Partially Compensated

C. Respiratory Alkalosis, Fully Compensated

D. Metabolic Alkalosis, Fully Compensated

Correct Answer D.

15. pH 7.64, PaCO2 25, HCO3- 19

A. Respiratory Acidosis, Uncompensated

B. Respiratory Alkalosis, Uncompensated

C. Respiratory Alkalosis, Partially Compensated

D. Metabolic Alkalosis, Partially Compensated

Correct Answer C.


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