Acid-base Analysis

Question 1

How long does the compensatory response for a metabolic acidosis take?

Answer 1

30-120 to start

12-24 hours to complete

Question 2

What is the equation for figuring out the magnitude of the compensation?

Answer 2

Change in paco2 = 1.2 x the change in hco3

Or

Expected PaCO2 = 40 - ( 1.2 X (24- HCO3)

Question 3

What is the compensatory response to a metabolic acidosis?

Answer 3

A change in minute ventilation mediated by the carotid body chemoreceptors

Question 4

What is the equation for response to metabolic alkalosis?

Answer 4

Change in PACO2 = 0.7 X change in HCO3

Or

Expected PACO2 = 40+ (0.7 x (current HCO3-24)

Question 5

How long does it take the body to respond to respiratory acid base disorders?

Answer 5

2-3 days

Question 6

How do you know there is a mixed acid-base disorder?

Answer 6

If only the ph or PaCO2 is abnormal

Question 7

What does it mean if only the PaCO2 is abnormal?

Answer 7

It means there is a respiratory acid base disorder with a metabolic in the opposite direction (so if the PaCO2 is up, it is a respiratory acidosis with metabolic alkalosis

Question 8

What does it mean if the only ph is abnormal ?

Answer 8

There is a metabolic acid base disorder in the direction of the ph and a respiratory in the opposite direction (so if ph is low , it is a metabolic acidosis with respiratory alkalosis)

Question 9

What does it mean if the bicarbonate is near normal in a primary respiratory acid base disorder?

Answer 9

The problem is acute

Question 10

What is the principal unmeasured anion in the blood?

Answer 10

Albumin

Question 11

What does a low albumin level do to the anion gap?

Answer 11

Lowers the anion gap having the potential to mask a true anion gap

Question 12

What is the formula for the corrected anion gap?

Answer 12

AGc= AG + 2.5 (4.5 - albumin)

Question 13

What happens in advanced renal failure?

Answer 13

You cannot secrete hydrogen ions from the distal tubules, so you get a AG metabolic acidosis

Question 14

What are the causes of normal AG acidosis?

Answer 14

Diarrhea
Normal saline
Renal insufficiency 
Renal tubular acidosis
Acetazolamide
Ureteroenterostomy

Question 15

What do you get a hyperchloremic metabolic acidosis?

Answer 15

Because chloride is kept to maintain electrical neutrality

Question 16

What is the gap-gap ratio?

Answer 16

(AG-12)/24-HCO3)

Question 17

What does it mean if the gap gap ratio is less than 1?

Answer 17

There is coexistence of a normal AG metabolic acidosis with the AG metabolic acidosis

Question 18

What does it mean if the gap gap ratio is greater than one?

Answer 18

There is a metabolic alkalosis with the anion gap metabolic acidosis

Question 19

What are the causes of metabolic alkalosis in the ICU?

Answer 19

NG tube suction

Diuresis

Question 20

What is the equation for figuring how much bicarbonate is needed to fix the ph on the ABG?

Answer 20

0.2 X patient weight X base excess