The nurse is reviewing the arterial blood gas (ABG) result for a client currently on a 100% non-rebreather mask. The nurse is able to interpret which of the following results as hypoxemic respiratory failure?
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Table 9.9 Normal Arterial Blood Gas Values |
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ABG Value. Normal Value |
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pH 7.35-7.45 |
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PaCO2 35-45 mmHg |
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HCO3- 22-26mEq/L |
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Base excess -2 to +2 |
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PaO2 80-95 mmHg |
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SaO2 >95% |
pH 7,44; Pa02 44 mmHg: PaCO2 35 mmHg; HCO3 25 mEq/L; 02 Sat 76%
pH 7.30; Pa02 80 mmHg; PaCO2 62 mmHg; HCO3 25 mEq/L; 02 Sat 94%
pH 7.35; Pa02 65 mmHg; PaCO2 40 mmHg: HCO3 26 mEq/L; 02 Sat 90%
PH 7.48; Pa02 75 mmHg; PaCO2 41 mmHg: HCO3 28 mEg/L; 02 Sat 9386
The Correct Answer is A
A. pH 7.44; PaO2 44 mmHg; PaCO2 35 mmHg; HCO3 25 mEq/L; O2 Sat 76%: This set of arterial blood gas (ABG) values is consistent with hypoxemic respiratory failure. Hypoxemic respiratory failure is characterized by a PaO2 less than 60 mmHg, and this client has a PaO2 of 44 mmHg, which is significantly below the normal range of 80-95 mmHg. Despite the fact that the client is on a 100% non-rebreather mask (which should ideally deliver high levels of oxygen), the low PaO2 suggests that oxygenation is not being effectively improved. Additionally, the low O2 saturation of 76% further supports the diagnosis of hypoxemic respiratory failure.
B. pH 7.30; PaO2 80 mmHg; PaCO2 62 mmHg; HCO3 25 mEq/L; O2 Sat 94%: This ABG indicates respiratory acidosis (pH is low, PaCO2 is elevated), but the PaO2 of 80 mmHg is within the normal range, and the O2 saturation of 94% is also normal. Respiratory acidosis with a normal PaO2 would indicate an issue with ventilation (hypoventilation), not hypoxemic respiratory failure. The patient is retaining CO2 but is still oxygenating well, so this result does not indicate hypoxemic respiratory failure.
C. pH 7.35; PaO2 65 mmHg; PaCO2 40 mmHg; HCO3 26 mEq/L; O2 Sat 90%: This result shows a PaO2 of 65 mmHg, which is mildly low but not sufficiently low to meet the criteria for hypoxemic respiratory failure (PaO2 should be below 60 mmHg for this diagnosis). The O2 saturation of 90% is also slightly low but not critically low. This client may have mild hypoxia but is not in respiratory failure based on these values.
D. pH 7.48; PaO2 75 mmHg; PaCO2 41 mmHg; HCO3 28 mEq/L; O2 Sat 93%: In this case, the PaO2 of 75 mmHg is slightly low but still within an acceptable range, and the O2 saturation of 93% is adequate. The elevated pH and normal PaCO2 suggest the presence of respiratory alkalosis (likely caused by hyperventilation). These ABG results are not consistent with hypoxemic respiratory failure, as the oxygen levels are still within a safe range.
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Naxlex Comprehensive Predictor Exams
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Correct Answer is B
Explanation
A. Partially compensated metabolic alkalosis:
Metabolic alkalosis is characterized by elevated bicarbonate levels (HCO3), but in this case, the HCO3 is elevated (29 mEq/L), which suggests alkalosis. However, the PaCO2 is elevated at 47 mmHg, which is more consistent with a respiratory problem. A fully or partially compensated metabolic alkalosis would show a normal or low PaCO2 (due to respiratory compensation). Therefore, this option does not fit the ABG results.
B. Partially compensated respiratory acidosis: In this case, the pH is 7.17, which is low and indicates acidosis. The PaCO2 is 47 mmHg, which is elevated (normal range: 35-45 mmHg), indicating that the respiratory system is contributing to the acidosis. The HCO3 is 29 mEq/L, which is elevated (normal range: 22-26 mEq/L), suggesting a compensatory response from the kidneys to retain bicarbonate in an attempt to buffer the acidosis. Since the pH is still below normal and has not yet returned to the normal range (7.35-7.45), this suggests that the compensation is partial and the primary issue is respiratory acidosis.
C. Fully compensated metabolic alkalosis:
This answer is incorrect because metabolic alkalosis is not the primary disturbance here. Also, for a condition to be fully compensated, the pH would need to be within the normal range (7.35-7.45). Since the pH is 7.17, the condition is not fully compensated.
D. Fully compensated respiratory acidosis:
For fully compensated respiratory acidosis, the pH should be within the normal range, as the kidneys would have fully compensated for the elevated PaCO2. Since the pH is 7.17, this is a sign of partial compensation, not full compensation. Therefore, this option is incorrect.
Correct Answer is D
Explanation
A. Serum potassium of 5.2 mEq/L: A potassium level of 5.2 mEq/L is slightly elevated but is still within a potentially acceptable range (normal is 3.5-5.3 mEq/L). While elevated potassium can be a concern, particularly in the context of an MI or with certain medications (like potassium-sparing diuretics), this level is not critically high. The nurse should monitor the potassium levels, but this is not an urgent finding requiring immediate reporting unless it increases further or is accompanied by significant symptoms (such as arrhythmias).
B. T wave depression on electrocardiogram (ECG): T wave depression can be a sign of ischemia or injury, which is common in the setting of an acute myocardial infarction. However, T wave changes are expected in this context and do not indicate an immediate emergency. The nurse should continue to monitor the ECG for any progression or worsening of ischemic changes but should prioritize concerns such as hypotension or worsening clinical status over this finding.
C. Heart rate of 90 beats per minute: A heart rate of 90 beats per minute is within normal limits (60-100 beats per minute), especially in the early stages of an MI. Nitroglycerin may cause a reflex tachycardia as a compensatory response to the decreased blood pressure, but a heart rate of 90 bpm is not an alarming finding. The nurse should continue to monitor the heart rate, but it is not the most pressing concern compared to hypotension. 4o mini
D. Blood pressure of 90/50: A blood pressure of 90/50 mmHg is significantly low and could indicate that the client is experiencing hypotension, which is a known side effect of nitroglycerin infusion. Nitroglycerin causes vasodilation, which can reduce blood pressure, especially in clients who are already at risk due to an acute myocardial infarction (MI). Low blood pressure can compromise perfusion to vital organs, including the heart, brain, and kidneys, and may lead to shock if not corrected promptly. This finding should be reported immediately to the healthcare provider, as it may require adjustment of the nitroglycerin dosage or discontinuation of the infusion.
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