Asprin toxicity, how many hours later is met acidosis?

[sadaca]

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Hey guys, for Aspirin intoxication, IMMEDIATELY is Resp Alkaosis then its MIXED (4-5 hrs later on UW) and then much later it is Met Acidosis. For the UWORLD Q, the guy had presented 5 hrs later and I picked Metabolic acidosis , UW says Met. Acidosis is much later.

Anyone know how much later met acidosis takes to occur? How do you guys approach aspirin toxicity time frame?

Appreciate it,

 

[surgok]

In aspirin toxicity, you get superimposed metabolic acidosis followed by initial respiratory alkalosis. 5hrs is too short for your kidney to even think about start the compensatory process. It would take days.

 

[sadaca]

Hey thanks alot friend, so initially is Resp Alkaosis, then Mixed (with hours) and DAYS later is met acidosis. Renal compensation always takes time , I forgot that.

 

[sadaca]

Mixed would be normal pH and met acidosis plus resp alkasosis profile, corret?

 

[DeeJay2728]

Yea, I'm confused with "mixed". There would be Resp alkalosis at first, bc you're blowing off your CO2, then what? Would your respiration rate eventually slow down and turn into Resp acidosis??

 

[surgok]

Aspirin initially stimulates the respiratory center leading to hyperventilation = respiratory alkalosis.
At the same time, aspirin gradually attacks the mitochondria, uncouples oxidative phosphorylation among other things. Glucose metabolism is hindered, so keto acids start building up = respiratory alkaosis + metabolic acidosis (note at this stage, the initial respiratory alkalosis becomes compensatory to the metabolic acidosis)
Increased buildup of organic acids tips the scale to metabolic acidosis at later stage (one source says after 24 hrs).
I think this is all we have to know for step I.

 

[DeeJay2728]

Thank you surgok!!

 

[sadaca]

Thank you!

 

[Phloston]

I generally tell my students:

Patient presents 3 hours after aspirin OD: respiratory alkalosis.
Patient presents 12 hours after aspirin OD: mixed respiratory alkalosis - metabolic acidosis.

The common point of confusion is that it's a mixed acid-base status because the metabolic acidosis is NOT a compensation for the respiratory alkalosis; the aspirin itself causes both.

 

[sadaca]

Hey thanks buddy! What is the common presentation? Is it tinnitus?

 

[sadaca]

Yep! It would be Ph 7.38 PCO2 is 20 HCO3 - 22 ,
the Low HC03 like you said is NOT due to compensation it is due to concurrent Met acidosis.

 

[notbobtrustme]

hey, I remember doing this question and getting it right for the wrong reason. Can you link the QID so I can it over again?

 

[sadaca]

hey sure np! Its qd 1544.
Also you can just search by keywords in uworld