Metabolic Acidosis Flashcards
What is metabolic acidosis?
pathologic disturbance characterized by low arterial pH (increased H+ concentration) with decreased plasma HCO3- concentration.
What is the difference between acidOSIS and acidEMIA?
- acidemia= pH less than 7.37
- acidosis= process that caused the acidemia
What are the 3 general causes of metabolic acidosis?
- increased acid generation
- decreased acid excretion
- lack of bicarb production
Why does acidosis matter?
it can cause decreased cardiac contractility, vasodilation (hypotension), altered mental status, alteration of O2 binding affinity, and/or arrhythmias.
** What is the anion gap?
measured cations - measured anions= unmeasured anions.
*Na+ - (Cl- + HCO3-) = 6 to 12 normally.
What are the causes for an anion gapped metabolic acidosis?
MUDPILES:
- Methanol (cleaning solutions, antifreeze, fuels).
- Uremia (renal failure with symptoms)
- DKA
- Paraldehyde
- Iron
- Lactic acid
- Ethylene glycol (antifreeze, suicide attempts)
- Salicylate toxicity (aspirin)
** What is the newer pneumonic for gapped metabolic acidosis?
GOLDMARK
- Glycols (ethylene, propylene)
- 5-Oxyprolene (metabolite of acetaminophen toxicity)
- L- Lactic acid
- D-lactic acid
- Methanol
- Aspirin
- Renal failure (uremia)
- Ketosis (diabetic, alcoholic, starvation)
What are the toxic alcohols that cause gapped metabolic acidoses?
- ethlyene glycol= converted to oxalic acid
- methanol= converted to formic acid
- propylene glycol= converted to pyruvic acid, acetic acid, lactic acid, propionaldehyde
* isopropyl alcohol does NOT cause an anion gap, but it does cause an osmolar gap.
** What is important to remember about acid/base with aspirin?
can cause gapped metabolic acidosis OR respiratory alkalosis
** What is an osmolar gap?
created by an unmeasured osmole in the bloodstream and is equal to the measured osmolality - calculated osmolality.
*It should be less than 10. If it is greater than 10, think alcohol intoxication.
How does the osmolar and anion gap change over time?
if the osmolar gap is high, you know that the alcohol has not yet been converted to its substituents (i.e. more methanol than formic acid). As the alcohol converts, the anion gap will rise and the osmolar gap will fall.
** What will you see in the urine of someone who has ingested ethylene glycol (antifreeze)?
calcium oxalate crystals.
What can methanol do to your vision?
cause blindness by affecting the optic nerve
Where is propylene glycol used as a solvent?
tobacco products and lorazapam drips
** What is a non anion-gapped metabolic acidosis (aka hyperchloremic metabolic acidosis)?
loss of bicarbonate or lack of excretion of acid
- HARDUP
- Hyperalimentation, Hyperchloremia
- Acetazolamide, Addison’s
- Renal tubular acidosis
- Diarrhea
- Ureterosigmoid fistula
- Pancreatic fistula
What does a URINE anion gap help to decipher?
between renal and non-renal causes of non anion-gapped metabolic acidosis
*** What are the 5 steps to interpreting acid/base disorders?
- metabolic acidosis= serum HCO3- low
- check pH
- calculate anion gap
- use winter’s formula to assess compensation
- use delta/delata (change in anion gap/change in bicarb)
** What is winter’s formula?
pCO2= 1.5(HCO3-) + 8 +/- 2
- if high then respiratory acidosis is also present HYPOventilation).
- if low, respiratory alkalosis (HYPERventilation)
Should the change in the bicarb be the same as the change in the anion gap?
YES: delta/delta (pt’s anion gap - normal anion gap)/ normal HCO3- - pt’s HCO3-)
- if result is >1= metabolic alkalosis is also present
- if result is
How are arterial blood gasses (ABGs) given?
pH/pCO2/pO2/HCO3-
What is normal pCO2?
40
If a pt has a sever infection/sepsis, what should you think is causing the metabolic acidosis?
lactic acid
