Our winner is the illustrious ablumenberg!
For the initial presentation, see here.
In brief, we have a gorilla of an acid-base question with pertinent history including a history of diabetes and alcohol abuse. This one’s a little long, so put on your focus hat.
VBG: pH 7.3, PO2 102, PCO2 30, HCO3 14, lactate 3
BMP: Na 145, K 5.2, Cl 103, HCO3 15, BUN 10, Cr 0.5, gluc 301
Serum Osm: 298
The correct interpretation is as follows
1. pH 7.3 = acidosis
2. HCO3 low at 14 with PCO2 at 30 = metabolic acidosis with respiratory compensation.
3. Per all three rules below, the metabolic acidosis is appropriately compensated with respiratory alkalosis
2. Rule of 15: PCO2 = HCO3 +15 = 30
3. Rule that the PCO2 in compensated metabolic acidosis should be the last 2 digits of the pH. Hence pH 7.30 and PCO2 30.
4.To narrow our differential, let’s calculate the Anion Gap.
5. The differential for anion gap metabolic acidosis is long.
Methanol, Metformin
Uremia
Diabetic (or any other
Ketoacidosis)
Paraldehyde, Phenformin,
Propylene
Iron, Isoniazid
Lactate
Ethylene Glycol
Salicylates, Sulfur
(inorganic)
Theopylline, Toluene
Cyanide, Carbon Monoxide
6. What about the osmolar gap?
7. As we are edge-of-our seats curious about a potential concomitant acid/base process going on let’s check out the Delta/Delta… Here we go!
The concept1. (AG-12)/(24-HCO3). If the value is < 1, you have more bicarb than you should, implying that you have a concomitant metabolic alkalosis. If the value is >2, you have LESS HCO3 than you should and have a concomitant non-gap metabolic acidosis.
– Here it equals 1.7, which is borderline between a pure metabolic acidosis and a concomitant metabolic alkalosis.
2. Corrected HCO3 = measured HCO3 + (anion gap – 12)
If Corrected HCO3 < 24, then a concomitant non-anion gap exists
If Corrected HCO3 > 24 then a concomitant metabolic alkalosis exists.
-Here, Corr HCO3 = 30.
8. So his actual acid base disorder is?
9. So his diagnosis is?
10. What are you going to do about it?
By Dr. Andrew Grock with special thanks to Dr. Rich Sinert!
References
Dr. Sinert
Golfrank’s Toxicologic Emergencies
Harrison’s
uptodate.com
andygrock
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1 Comment
Raul · November 14, 2014 at 4:52 pm
Since you were discussing compensation and how to calculate it I thought I would send out this link (http://www.anaesthesiamcq.com/AcidBaseBook/ab9_3.php) which has a bunch of rules on the subject. Hope it helps!