Acid-Base Part I

Question 1

What is the compensation formula for metabolic acidosis?

Answer 1

PCO2= 1.5[HCO3-] + 8 +/- 2

Question 2

What is the compensation formula for metabolic alkalosis?

Answer 2

PCO2 will increase by 0.7 mmHg for each 1.0 mEq/L increase in HCO3- from normal (24)

Question 3

What is the compensation formula for respiratory acidosis?

Answer 3

Acute: HCO3- will increase by 1 mEq/L for every 10 mmHg increase in PCO2 from normal (40)

Chronic: HCO3- will increase by 3.5 mEq/L for every 10 mmHg increase in PCO2 from normal (40)

Question 4

What is the compensation formula for respiratory alkalosis?

Answer 4

Acute: HCO3- will decrease by 2 mEq/L for every 10 mmHg decrease in PCO2 from normal (40)

Chronic: HCO3- will decrease by 5 mEq/L for every 10 mmHG decrease in PCO2 from normal (4)

Question 5

How do you calculate anion gap?

Answer 5

AG= Na+ - (HCO3- + Cl-)

Question 6

What is normal anion gap?

Answer 6

12+/-2

Question 7

Why does renal tubular acidosis (RTA) or diarrhea result in NAGMA?

Answer 7

Don’t know. Guess that loss of HCO03 and Na+ produces a volume contraction, stimulating NaCl retention in the kidney.

Question 8

How does hypoalbuminemia affect anion gap?

Answer 8

Falsely lowers AG, must be corrected.

Question 9

How do you correct the anion gap in hypoalbuminemia?

Answer 9

For every 1 g/dL drop in albumin, the AG drops by 2.5 mEq/L.

Ex: serum albumin at 1.5, normal is 3.5. Drop by 2. The AG must be increased by 5 mEq/L. If calculated AG= 12, the real AG is 17 (HAGMA).

Question 10

How do you calculate serum osmolality?

Answer 10

2(Na) + (Glucose/18) + (BUN/2.8)

Normal is 275-290 mosm/L

Question 11

What is the osmolar gap?

Answer 11

Measured serum osmolality- calculated serum osmolality.

Normal osmolar gap < 10 mosm/L. If >10, suggests additional solutes to blood.

Question 12

What is the osmolar gap useful for?

Answer 12

Screening for alcohol ingestions, particularly in HAGMA cases
Screening for ketoacidosis
Screening for lactic acidosis

Question 13

What is calculating the delta-delta gap used for?

Answer 13

In patients with HAGMA to determine if there is a coexistent NAGMA or metabolic alkalosis present.

Question 14

What is the expected Delta-Delta gap? How do you calculate it?

Answer 14

For every increase in AG, there should be an equal decrease in serum HCO3-.

Delta gap= calculated AG- normal AG (12)
Ex: If AG is 20 (8 above normal), expected HCO3- should be 16 (8 below normal value of 24). DG= 20-12=8. Delta HCO3-= normal HCO3- (24) – Delta gap= 24-8=16

If the measured HCO3- was close to 16, then no additional acid-base disorder present.
If measured HCO3- > 16, then a metabolic alkalosis is present in addition to HAGMA.
If measured HCO3- < 16, then a non-gap metabolic acidosis is present in addition to the HAGMA.

Question 15

What’s the normal value for HCO3-?

Answer 15

24 mEq/L

Question 16

What’s the normal value for PCO2?

Answer 16

40 mmHg

Question 17

What’s the normal osmolality gap?

Answer 17

10 mmol/L

Question 18

What’s the mneumonic GOLDMARK stand for in causes of HAGMA?

Answer 18

Glycols
Ocoproline (acetaminophen)
Lactic acidosis
D-Lactic acidocis (short bowel syndrome)
Methanol
Aspirin
Renal Failure
Ketoacidocis (alcoholic, diabetic, starvation)

Question 19

How do you dx pyroglutamic (5-oxoproline) acidosis? Who is it seen in? What does it do?

Answer 19

Urinary organic acid screen. Seen in women who are malnourished or critically ill. Acetaminophen depletes glutathione.

Question 20

How do you treat pyroglutamic (5-oxoproline) acidosis?

Answer 20

Discontinue acetaminophen
IVF
N-acetylcysteine

Question 21

How do ketoacidosis and lactic acidosis change the osmolar gap?

Answer 21

Smaller increase in osmolar gap than the alcohols

Question 22

What is acidosis associated with?

Answer 22

Hyperkalemia

H+ ions enter the cells and K+ exit

Question 23

What is alkalosis associated with?

Answer 23

Hypokalemia

H+ exit the cells and K+ enters

Question 24

What are the 4 major causes of NAGMA?

Answer 24

Diarrhea
Ureteral diversion or fistula
Renal tubular acidosis
Hyeralimentation (enteral nutrition or total parenteral nutrition)