Kleinschmidt- Acid Base Differential Diagnosis Flashcards
What should you first consider when evaluating AB disorders?
Look at pH using ABG- whichever side of 7.40 is the primary abnormality (acidosis or alkalosis, the body never fully compensates)
When evaluating AB disorders, what should you do once you’ve figured out the pH?
Calculate the anion gap,
What does an elevated anion gap indicate?
primary metabolic acidosis or a mixed acid base problem that includes a anion gap
When evaluating AB disorders, what should you do next if there IS an elevated anion gap?
Calculate a osmol gap
How do you calculate an osmol gap?
Measured osmolarity- calculated osms should be < or = 10
2 (Na) + Glucose/18 + BUN/2.8= calculated osms (usually 285 or so)
What might you find by calculating an osmol gap?
Ingestions such as ethylene glycol, methanol, etc
Once you’ve calculated the elevated anion gap and the osmol gap what should you do next?
Calculate the excess anion gap (calculated minus 12) and add to measured bicarb, it should equal a normal bicarb level (24-26)
What does it mean if the excess anion gap is low? high?
LOW means there is also a non anion gap acidosis
If it is HIGH there is an underlying metabolic alkalosis.
Normally a change of gap of 1 will drop the HCO3‾ by equal amount. What is going on if it doesn’t add up right?
There is a SECOND ongoing process.
This process is also called the “delta gap” by some.
If ABG is normal but you have an elevated anion gap you may have a….
mixed metabolic alkalosis and anion gap metabolic acidosis
What leads to leads to PCO2 lower than predicted for the acidosis?
Mixed Metabolic Acidosis and Respiratory Alkalosis
What leads to HCO3‾ higher than predicted for the acidosis?
Mixed Metabolic Alkalosis and Respiratory Acidosis
What causes a higher HCO3‾ and lower PCO2 than predicted?
Mixed metabolic and resp alkalosis
What is the primary disturbance behind metabolic acidosis and the compensatory response? What are the sources of these disturbances?
Primary disturbance is retention of acid, this is reflected by a decrease of HCO3‾.
Compensatory response is to increase ventilation and decrease the PaCO2 on ABG.
Either is caused by an overproduction of acid or loss of alkali stores, or failure of renal
mechanisms to synthesize base or excrete acid.
What is indicative of high anion gap acidosis?
- ph <7.35, low HCO3‾ on ABG or chemistry tests
- AG over 15
- Compensation is to get rid of CO2
- pCO2= (1.5 x HCO3‾) + 8 (+/-2)
- or PCO2= last 2 digits pH