Nephro - Acid Base - Online MedEd Flashcards Preview

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Flashcards in Nephro - Acid Base - Online MedEd Deck (31):
1

Primary disturbances are...

Resp acidosis/alkalosis
Metabolic acidosis/alkalosis

2

Start with what in acid base disorders?

pH
7.35-7.45
-If pH is not 7.4 = abnormal!
<7.4 = acidemia
>77.4 = alkalemia
-Notice it is "emia" not "osis" (emia refers to disorders of blood)

3

After looking at pH what is the next step?

Look at CO2, normal CO2 is 40
-If acidemic --> AND too much CO2 --> resp acidosis
-If acidemic --> AND too little CO2 --> blowing off CO2 --> so metabolic acidosis
-If alkalemic --> AND too little CO2 --> resp alkalosis
-If alkalemic --> AND too much CO2 --> metabolic alkalosis
*Think of CO2 as respiratory acid

4

How to think of CO2

As respiratory acid
-So if CO2 is too much is acidosis --> must be respiratory acidosis
-So if CO2 is too little in alkalosis --> must be respiratory alkalosis

5

Respiratory acidosis differential

Hypoventilation - opiate overdose (RR too low), asthma/COPD/air trapping, decreased muscular strength (i.e. long-term ventilation), sleep apnea
-If respiratory acidosis - just need to find a cause, no need to find more cause

6

Respiratory alkalosis - differential

Hyperventilation - pain and anxiety; instances of hypoxemia

7

Metabolic alkalosis - what is the next test to get?

Urine chloride!
-Is person volume responsive? or not?
-If person is volume down, RAS activated, aldosterone grabs Na from collecting duct, makes a concentration gradient, so that water is absorbed by aquaporins
-Na brings Cl
-So when volume down, kidneys hold NaCl
-So little urine Cl if volume responsive
-Volume responsive metabolic alkalosis = contraction alkalosis = urine chloride is low

8

Contraction alkalosis - what is it?

Volume responsive metabolic alkalosis
-Urine chloride will be low in urine, as retained in blood stream to bring in Na when patient is volume down
Urine chloride <10

9

Volume responsive metabolic alkalosis occurs in what instances?

Diuretics
Dehydration
Emesis/NG suction
-Urine chloride is low

10

If metabolic alkalosis, but urine chloride is normal

Consider hypertension - hyperaldo states

11

No hypertension in metabolic alkalosis

Gittleman
Darteur

12

So in volume contraction metabolic alkalosis what is the treatment

Treatment is volume repletion

13

With metabolic acidosis... what do you need to assess?

Anion gap
Na-Cl-HCO3

14

Anion gap > 12... what is this?

Anion gap acidosis

15

Anion gap < 12... what is this?

Non-gap

16

Normal albumin will have anion gap of what?

12

17

Anion gap acidosis... what mnemonic to use?

MUDPILES
Look for a compound that is osmotically and acid base active
Methanol, uraemia, DKA, propylene, isopropyl, lactic acid, ethylene glycol, salicylate

18

Non gap metabolic acidosis... what do you want to assess?

Urine anion gap?
Urine Na + Urine Potassium - Urine Chloride
*Different than serum anion gap equation

19

How to divide urine anion gap?

Positive urine anion gap: positively renal tubular acidosis
Negative urine anion gap: diarrhea
*If lose volume will get metabolic alkalosis
But diarrhea loses bicarb as well... so get metabolic acidosis (not alkalosis)

20

What are the steps to look at primary disturbance

Step 1: pH
Step 2: CO2
Step 3: other disturbance?

21

Resp acidosis

Means pH acidemic
Respiratory acid is high

22

Metabolic acidosis

Means pH is acidemic
Respiratory acid is low (CO2 is low)
So metabolic acidosis

23

Resp alkalosis

pH is high
Respiratory acid is low (CO2 is low)

24

Metabolic alkalosis

pH is high
Resp acid is high

25

Always check...

Anion gap
*Doesn't matter what the primary disturbance is... always check anion gap

26

After determining pH and CO2... what are the next 3 steps?

1) Check anion gap
2) Check: acute or chronic
3) Bicarb appropriate?

27

How do you determine chronicity?

10 points of CO2 (dime change)... pH will change by 0.08 if acute and 0.4 if chronic
1) What is pH and CO2
2) Calculate change in pH from 7.4
3) Then determine if acute or chronic
4) This will help to see if bicarb is appropriate?

28

What are acute and chronic changes of bicarb in respiratory acidosis and respiratory alkalosis for every dime change in CO2?

Respiratory acidosis... bicarb change 1 (acute), 3 (chronic)
Respiratory alkalosis... bicarb change 2 (acute), 4 (chronic)
*dime change of CO2

29

Is expected bicarb equal to given bicarb? what does this tell you about additional metabolic changes

If too much bicarb/base... then there is coexisting metabolic alkalosis
If too little bicarb... metabolic acidosis

30

Metabolic acidosis - what steps?

pH is low
CO2 is low
Step 3? Other there are other problems.
3a. Calculate anion gap (Na-Cl-HCO3). Normal anion gap is 12 (normal anion gap is albumin x 3)
3b. pCO2 appropriate? Winter's formula = 1.5xbicarb + 8 (+/- 2)
If given CO2 is greater than expected (Winter's)... so too many respiratory acids = also have respiratory acidosis
If given CO2 is less than expected... then too few respiratory acids = respiratory alkalosis
-However, if CO2 can be normal so no respiratory disturbance
3c. Bicarb normal? -Can use delta-delta
Use add back method.
-Basically determine anion gap and calculate from normal anion gap
-If H+ which is HCO3 is more than 24 (normal bicarb) this is alkalosis, <24 is metabolic acidosis (nongap)

31

Metabolic alkalosis means

Aldosterone is up!
No equations needed here
No need to determine another disturbance
-Check anion gap to check for metabolic alkalosis with anion gap metabolic acidosis