ABG Question

[peaberrytree]

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1. 
   
   Which has worse prognosis? Please explain.
   A. pH 7.27 pCO2 6 pO2 56
   B. pH 7.60 pCO2 18 pO2 80

 

[pathologyDO]

Hmmm this is really a big guess IMO... I think a clinical scenario would be most helpful.

A. pH 7.27: acidotic; pCO2 6: severely decreased, so this is metabolic acidosis; pO2 56: in relation to the CO2 is much higher... could be seen as the body actively working to restore hemeostasis -> in tact function of homeostatic mechanisms is a good sig, but why the metabolic acidosis?? Could it be renal failure -> decreased bicarb reabsorption ?

B. pH 7.60: alkalosis; pCO2 18: decreased, but not as severe as in A; pO2 80: lowish but normalish; since pO2 is relatively higher than pCO2 it could be respiratory alkalosis in patient with decreased lung function (e.g. COPD; in this case we have no indication of the HCO3- status and thus we are not sure whether there is a compensated increase in

Overall I'm not sure that I would put B, my inclination is A. My reasoning is because the respiratory status of this patient is severely decreased since both pCO2 and pO2 are so low, and in addition we see that this must be a metabolic acidosis on top of this respiratory dysfunction, and this could be due to renal failure. But then again, I'm definitely no expert in ABG

 

[Jabbed]

A.

 

[peaberrytree]

I found the question just now. But the explanation wasn't great. Thank you for your detailed answer!

A 14 year-old male presents to the ED experiencing a severe asthma attack. His respiratory effort is shallow and he is using accessory muscles to breathe. Auscultation of his chest reveals no audible wheezing. Vital signs include BP 90/60 mmHg, P 160 bpm, RR 52. An arterial blood gas (ABG) is ordered. Normal ABG values at your institution are pH 7.35-7.45, CO2 35-45, pO2 80-95. Which of the following ABG findings suggests the poorest prognosis?
A. pH = 7.27 pCO2 = 46 pO2 = 56
B. pH = 7.60, pCO2 = 18 pO2 = 80
C. pH = 7.44, pCO2 = 38 pO2 = 90
D. pH = 7.52, pCO2 = 28, pO2 = 80

Answer: A. pH = 7.27 pCO2 = 46 pO2 = 56 is associated with the poorest prognosis in this patient.

 

[Jabbed]

I found the question just now. But the explanation wasn't great. Thank you for your detailed answer!

A 14 year-old male presents to the ED experiencing a severe asthma attack. His respiratory effort is shallow and he is using accessory muscles to breathe. Auscultation of his chest reveals no audible wheezing. Vital signs include BP 90/60 mmHg, P 160 bpm, RR 52. An arterial blood gas (ABG) is ordered. Normal ABG values at your institution are pH 7.35-7.45, CO2 35-45, pO2 80-95. Which of the following ABG findings suggests the poorest prognosis?
A. pH = 7.27 pCO2 = 46 pO2 = 56
B. pH = 7.60, pCO2 = 18 pO2 = 80
C. pH = 7.44, pCO2 = 38 pO2 = 90
D. pH = 7.52, pCO2 = 28, pO2 = 80

Answer: A. pH = 7.27 pCO2 = 46 pO2 = 56 is associated with the poorest prognosis in this patient.

This helps. The clinical presentation of asthma is a respiratory alkalosis with high RR, low pCO2, and decreased pO2. The fact that the pCO2 is elevated despite the high respiratory rate suggests profound air trapping and respiratory failure.

 

[aspiringmd1015]

def A, but i Goljan said in his lectures that alkalosis is particulary bad for the patient bc of the left **** of the curve.

 

[pathologyDO]

def A, but i Goljan said in his lectures that alkalosis is particulary bad for the patient bc of the left **** of the curve.

That is true I was trying to remember that exact thing but couldn't! alkalosis is worse, all else being equal.

 

[seminoma]

Not sure if it's true for all things, but the PaO2/FiO2 is predictive of prognosis in ARDS. I would imagine it's generally applicable to any respiratory distress.