doc_clotaire
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A 56-year-old male with COPD is brought by family members to the emergency room because of dyspnea and cyanosis. His vital signs are pulse 95/min, BP 120/80, temperature 98.9. His physical examination shows barrel-shaped chest cavity with hyperresonance by percussion over both lungs. His CBC and blood gases while breathing room air upon admission are as follows:
PCO2
50 mmHg
PO2
50 mmHg
Serum HCO3-
32 mEq/L
Serum pH
7.45
RBCs
5.1X106/ml
Hemoglobin
13.5 gm/dl
HCT
42%
WBCs
8.8x 103/ml
The patient’s profile is most consistent with
A. Acute metabolic acidosis
B. Acute respiratory acidosis
C. Acute metabolic alkalosis
D. Acute respiratory alkalosis
E. Chronic respiratory acidosis
F. Compensated metabolic acidosis
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| robin082006
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C
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| mjl1717
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Clinically the barrel chested, hyperresonance and cyanosis sounds like the COPD (resp acidosis)
but lab report indicates iit has compensated to metabolic alkalosis, answer-c
(id lean toward chronic bronchitis or emphysema)
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| sarika
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but body never over-compensates....he has something else going on too....although i agree the answer is acute met alkalosis...
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| doc_clotaire
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I am sorry guys , C is the most common WRONG answer like Fisher would say !
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| Aashi
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E. Chronic respiratory acidosis
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| doc_clotaire
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CORRECT: E
Determination of electrolytes, pH and blood gases ideally should be performed on the same specimen or specimens obtained simultaneously, since the acid-base situation is very labile. For judging hypoxemia, it is necessary to know the patient’s hemoglobin or hematocrit value and whether the patient was breathing room air or oxygen when the specimen was drawn. An abnormal bicarbonate level means a metabolic rather than a respiratory disorder. However, the clinical presentation and the relationship of the bicarbonate level to PCO2 and PO2 should be used to decide if the case is a metabolic disorder, compensated respiratory disorder or a combined metabolic and respiratory disorder.
The increased level of PCO2 and decreased PO2 in this patient suggest respiratory acidosis even though the pH is at the upper border of normal. It is important to remember that a normal pH does not rule out an acid-base disturbance. The normal pH in this situation indicates that the condition is compensated. The increased level of the serum bicarbonate that is proportional to the increase in PCO2 confirms that possibility. The patient’s serum bicarbonate is slightly increased but if you compare it to the increased level of PCO2, you can see that these values are consistent with compensated respiratory acidosis.
For every 10-mmHg increase in PCO2, you should expect a 3.5 mEq/L rise in the serum bicarbonate in chronic respiratory acidosis as in this case. The patient’s presentation, blood gases and pH are consistent with chronic respiratory acidosis with compensation.
The increased level of PCO2 and the level of serum bicarbonate rule out the possibility of respiratory alkalosis. The increased level of serum HCO3- must be considered in relation to PCO2 and PO2 to avoid making the mistake of calling this condition metabolic alkalosis. Also, normal pH as well as the increased bicarbonate rules out the possibility of acute respiratory acidosis. The increased bicarbonate and the patient’s presentation rule out the possibility of acute metabolic acidosis. The level of the pH and the serum bicarbonate in relation to the levels of PCO2 and PO2 exclude the possibility of compensated metabolic acidosis.
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| 92306
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Very good Q doc_clotaire.
Well wanted to ask you what will be the change in pH value with an increase of 10 mmHg of pCO2 rise in chronic respiratory acidosis?
Only (For every 10-mmHg increase in PCO2, you should expect a 3.5 mEq/L rise in the serum bicarbonate in chronic respiratory acidosis as in this case) bicarb change is given.
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| Geroo
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but we were taught that body never over compensate!!
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| krsna
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E is the right ans...good one
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| mjl1717
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good q doc-clotaire! (since we have to know different degrees of difficulty with acid /base)
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