Clinical Acid Base

Question 1

What value of pKa is used in the Henderson Hasselbach equation?

Answer 1

6.1

Question 2

What is carbonic acid concentration in the blood proportional to?

Answer 2

PCO2

Question 3

How do we estimate the carbonic acid concentration in the blood?

Answer 3

PaCO2 x 0.03

Question 4

What is the Henderson Hasselbach equation that uses carbonic acid concentration?

Answer 4

pH = 6.1 + log10 (HCO3/0.03x PaCO2)

Question 5

If PaCO2 decreases acutely from increased minute ventilation, and HCO3 does not change, what will happen to pH?

Answer 5

pH will increase

Question 6

What is the trigger for renal or respiratory compensation in most scenarios?

Answer 6

serum pH

Question 7

What is a normal pH value?

Answer 7

7.4

Question 8

How do we calculate the anion gap?

Answer 8

Na-Cl-HCO3

Question 9

What is the normal AG level?

Answer 9

10 mEq/L +- 2

Question 10

What makes up the majority of the gap between anion s and cations in the AG equation?

Answer 10

serum albumin

Question 11

An increase in unmeasured anions or a decrease in unmeasured cations would have what effect on AG?

Answer 11

it would increase the AG

Question 12

A decrease in unmeasured anions or an increase in unmeasured cations would do what to AG?

Answer 12

lower AG

Question 13

What should arterial bicarbonate look like compared to venous bicarbonate?

Answer 13

they should be very close if they’re not, you probably have a data issue

Question 14

If pH is down and PaCO2 is up, what kind of acid base disturbance is this?

Answer 14

respiratory acidosis

Question 15

if pH is up and PaCo2 is down, what kind of acid base disturbance is this?

Answer 15

respiratory alkalosis

Question 16

In the acute setting, what should the change in pH be for the change in PaCO2?

Answer 16

0.08 pH for every 10 mmHg CO2 change

Question 17

during respiratory acid base disturbances, how does bicarbonate change?

Answer 17

it doesn’t change more than 1-2 mEq, usually in the same direction as PaCO2

Question 18

How does renal compensation change pH?

Answer 18

changing serum bicarb

Question 19

if pH is down and PaCO2 is down, what is true of the acid base disturbance?

Answer 19

expected respiratory compensation of metabolic acidosis

Question 20

if pHi s up and PaCO2 is up, what is true of the acid base disturbance?

Answer 20

expected respiratory compensation of metabolic alkalosis

Question 21

How do you define metabolic alkalosis or acidosis?

Answer 21

low bicarb = acidosis high bicarb = alkalosis

Question 22

What type of acid base disturbance is this: 7.20/20(8)

Answer 22

metabolic acidosis with compensatory hyperventilation

Question 23

With expected respiratory compensation for a metabolic process, what is true of the relationship between pH and PaCO2?

Answer 23

the last 2 digits of pH = PaCO2

Question 24

For ever 1 mEq/L increase in acid, what happens to bicarbonate?

Answer 24

1 mEq/L decrease

Question 25

What is indicated by an AG \> 20 mEq/L?

Answer 25

metabolic acidosis from acid accumulation (MUD PILES)

Question 26

What does MUD PILES stand for? What is it the DDx for?

Answer 26

methanol, uremia, diabetic ketoacidosis (or ketoacidosis from another cause), propylene glycol, isoniazid, lactic acidosis, ethylene glycol, salicylates of a metabolic acidosis from acid accumulation , AG \> 20

Question 27

What process is this?

Answer 27

1. low bicarb + pH=PaCO2 2. AG \> 27 --\> metabolic acidosis with acid accumulation (MUD PILES)

Question 28

What is the pneumonic for metabolic acidosis with a normal AG?

Answer 28

USED CARS uretero-enterostomy with bicarb rich ostomy fluid, saline administration, endocrine disorders (eg, adrenal insufficiency), diarrhea, carbonic anhydrase inhibitors (acetazolamide), ammonium chloride, renal tubular acidosis, spironolactone

Question 29

What is a hyperchloremic metabolic acidosis?

Answer 29

one with a normal AG

Question 30

What is the upper limit for bicarb that limits its ability to compensate for metabolic alkalosis?

Answer 30

PaCo2 \> 50

Question 31

What are the 2 types of metabolic alkalosis?

Answer 31

Chloride responsive and unresponsive

Question 32

what type of acid base disturbance is associated with contraction alkalosis?

Answer 32

chloride responsive metabolic alkalosis

Question 33

What causes chloride unresponsive metabolic alkalosis?

Answer 33

too much aldosterone

Question 34

Unless there are extra conditions, what should be true of the delta anion gap v. the delta bicarb?

Answer 34

They should be roughly equal

Question 35

If the serum bicarbonate is significantly lower than expected by the delta-delta analysis, what should be considered?

Answer 35

1. consider a concurrent bicarbonate wasting condition (i.e., a non-elevated AG metabolic acidosis)

Question 36

If the bicarbonate is significantly higher than expected by the delta-delta analysis what should be considered?

Answer 36

1. consider a concurrent bicarbonate excess state (i.e., a concurrent metabolic alkalosis)

Question 37

Interpret the following:

Answer 37

metabolic acidosis of the elevated AG variety with appropriate respiratory compensation. Note the delta-delta analysis: (delta AG = 27 – 10 = 17 meq/L, if this value is added to serum bicarb the result is 25 meq/L, which is in the normal range suggesting there is no other acid base disorder (namely, a there is no concurrent non elevated AG metabolic acidosis or metabolic alkalosis). Think MUD PILES.

Question 38

Interpret:

Answer 38

metabolic acidosis of the non-elevated AG variety with appropriate respiratory compensation. This is a bicarb wasted stated so think USED CARS. Note the elevated chloride. Note also a delta-delta analysis does not help: (delta AG = 9 – 10 = negative 1 meq/L, if this value is added to the serum bicarb the result is negative 7 meq/L, which is low - but you already knew that).

Question 39

Interpret:

Answer 39

metabolic alkalosis with expected respiratory compensation. Urine electrolytes and clinical data will help sort out chloride responsive vs. chloride unresponsive.

Question 40

Interpret:

Answer 40

respiratory alkalosis (pH and PaCO2 are on opposite sides of normal) and an elevated AG metabolic acidosis (MUD PILES) because AG \> 20. Delta-delta does not demonstrate a concurrent non elevated AG metabolic acidosis or metabolic alkalosis (20 - 10 + 16 = 26—which is a normal “corrected” bicarbonate). This is a double acid-base disturbance (eg, aspirin intoxication, which can cause a respiratory alkalosis and elevated AG metabolic acidosis). (Note for delta-delta: 20 is the calculated AG, 10 is the normal AG and 16 is the serum bicarbonate level).

Question 41

Interpret:

Answer 41

respiratory alkalosis (pH and PaCO2 are on opposite sides of normal) and an elevated AG metabolic acidosis (MUD PILES). Delta-delta demonstrates “too much” serum bicarbonate (29 – 10 + 16 = 35therefore a metabolic alkalosis is present as well). This is a triple acid-base disturbance

Question 42

Interpret:

Answer 42

elevated anion gap metabolic acidosis with expected respiratory compensation (MUD PILES). Delta-delta demonstrates “too little” serum bicarbonate (24 – 10 + 5 = _19_). Thus there is a concurrent non elevated anion gap metabolic acidosis. This is a double acid-base disturbance.

Question 43

Interpret:

Answer 43

elevated anion gap metabolic acidosis with an equally severe metabolic alkalosis. Delta-delta demonstrates too much bicarbonate (21 – 10 + 24 = 35). This is a double acid-base disturbance.

Question 44

What's the differential for high DLCO?

Answer 44

polycythemia DAH L to R intracardiac shunt Obesity

Question 45

What is on the differential for low DLCO?

Answer 45

anemia emphysema ILD R to L shunt PAH

Question 46

What is the differential for a respiratory alkalosis?

Answer 46

fever, pain, anxiety, sepsis, stimulants, PE, cirrhosis, hyperthyroid, pregnancy, and mild lung disease