ABGs come out to be an undifferentiated alkolosis....
- 0I have a question regarding ABGs on a patient I recently cared for.
Admitted with bilateral PNA. Discovered to have minor CHF, minor ARF, and finally blood Cx's came back positive for strep.
ABG results were as follows immediately after being placed on the Bipap machine due to respiratory fatigue- high likelihood of future intubation.
ABG pH 7.5H PCO2 34L HCO3- 27H PO2 75L
How would one interpret this? Metabolic or respiratory alkalosis? I just don't know what to think. I'd have thought it'd have been more like metabolic acidosis given given the diagnoses.
Thank you in advance if anyone can offer a clear explanation to me about this.
- 0Sep 11, '13 by GrnTeaEasy-peasy.
If you remember that it takes 24 hours+ to retain extra bicarb in response to hypercarbia from COPD, but moments for some well-meaning person with a mechanical ventilation device to blow off CO2 retention, you have your answer. Betcha this guy had COPD before he got his pneumonia.
This person has lowish oxygen ( you don't say whether he's on supplementation or not) but his alkalosis is due to his preexisting but now diminished chronic hypercarbia...which has been blown down to lower than usual levels (normal CO2 is 35-45) mechanically.
If he were in a primary metabolic alkalosis, he'd be trying not to breathe much, to compensate that alkalosis by retaining CO2, but they aren't letting him (probably just as well, too).
So, he has a mixed derangement with iatrogenic hypocarbia on top of a preexisting respiratory acidosis with metabolic compensation.
Let me know if this doesn't make sense. It's a beautiful example of how we can overcompensate and how people get into trouble in the first place.
- 0Sep 13, '13 by Esme12 Senior ModeratorIt's possible to have more than one disorder influencing blood gas values. For example ABG's with an alkalemic pH may exhibit respiratory acidosis and metabolic alkalosis. These disorders are termed complex acid-base or mixed disorders
Common Laboratory (LAB) Values - ABGs - Arterial blood gases
Respiratory Acidosis Acute < 7.35 > 45 Normal Partly Compensated < 7.35 > 45 > 26 Compensated Normal > 45 > 26 Respiratory Alkalosis Acute > 7.45 < 35 Normal Partly Compensated > 7.45 < 35 < 22 Compensated Normal < 35 < 22 Metabolic Acidosis Acute < 7.35 Normal < 22 Partly Compensated < 7.35 < 35 < 22 Compensated Normal < 35 < 22 Metabolic Alkalosis Acute > 7.45 Normal > 26 Partly Compensated > 7.45 > 45 > 26 Compensated Normal > 45 > 26