19. Introduction to Acid-Base Disturbance

Question 1

What is a serum anion gap? How is it interpreted?

Answer 1

[Na+] - ([Cl-] + [HCO3-])

Normal range is 8-16

If high, then there are other solutes in plasma (alcohols, lactic acidosis, ketoacidosis)

Question 2

How is osmolal gap interpreted?

Answer 2

Usually around 0. If greater than 10, then there are other solutes in plasma (alcohols, lactic acidosis, ketoacidosis).

Question 3

What is Δ [HCO3-]? How is it interpreted?

Answer 3

(Normal HCO3-) - (Δ Gap)

If [HCO3-] about equals Δ [HCO3-], then simple acid-base disorder.

If [HCO3-] is greater, then metabolic alkalosis + HAGMA

If Δ [HCO3-] is greater, then non-gap metabolic acidosis + HAGMA.

Question 4

What is Δ Gap?

Answer 4

(Calculated anion gap) - (normal anion gap)

Question 5

How does PaCO2 effect HCO3- during acute and chronic respiratory acidosis?

Answer 5

Acute: for every 10 mmHg increase in PaCO2, HCO3- goes up by 1 mEq/L

Chronic: for every 10 mmHg increase in PaCO2, HCO3- goes up by 3.5 mEq/L

Question 6

How does PaCO2 effect HCO3- during acute and chronic respiratory alkalosis?

Answer 6

Acute: for every 10 mmHg decrease in PaCO2, HCO3- goes down by 2 mEq/L

Chronic: for every 10 mmHg decrease in PaCO2, HCO3- goes down by 5 mEq/L

Question 7

What are the causes of high anion gap metabolic acidosis (HAGMA)?

Answer 7

GOLDMARK

Glycols
Oxoproline
L-lactate
D-lactate
Methanol
Aspirin
Renal failure
Ketoacidosis

Question 8

What are the causes of non-anion gap metabolic acidosis (NAGMA)?

Answer 8

HARDUPS

Hyperalimentation
Acetazolamide
Renal tubular acidosis*
Diarrhea*
Ureterosigmoid fistula
Posthypocapnia
Spironolactone

Question 9

What are the causes for metabolic alkalosis?

Answer 9

CLEVER PD

Contraction
Licorice
Endo
Vomiting
Excess alkali
Refeeding alkalosis
Post-hypercapnia
Diuretics

Question 10

What is the difference between cholride responsive and resistant alkalosis?

Answer 10

Responsive: Low urine Cl- because body is conserving Cl-. Giving normal saline should fix.

Resistant: High urine Cl- despite the body’s need to conserve it. Must treat cause of H+ loss.