Acid Base Metabolism

Question 1

How do you calculate an Anion Gap?

Answer 1

Na - [Cl + HCO3] = anion gap

Normal gap 8-12

Question 2

How do you calculate serum osmolality?

Answer 2

[2 x Na] + [BUN/2.8] + [Glucose/18] = serum osmolaity

Normal serum osm 265-285

Question 3

What formula do you use to correct metabolic acidosis?

Answer 3

Bicarbonate= weight x 0.3 x base deficit

Question 4

Normal Anion Gap Acidosis

“USED CARP”

Answer 4

*All have an ELEVATED Cl”. Normal anion gap always has an elevated chloride.

U-ureterostomy
S-small bowel fistula
E-extra chloride
D-diarrhea

C-carbonic anhydrase inhibitor use
A-adrenal insufficiency
R-renal tubular acidosis
P-pancreatic fistula

Question 5

What is the most common cause of a normal anion gap metabolic acidosis?

Answer 5

Diarrhea.

*If you have a normal gap metabolic acidosis and NO diarrhea it is due to RENAL TUBULAR ACIDOSIS.

Question 6

List the 4 types of RTA

Answer 6

RTA 1- “DISTAL”-cannot acidify urine, urine pH>5.5

RTA 2-“PROXIMAL”-cannot bring Bicarb back in, but distal H+ still being excreted, so pH<5.5

RTA 3- combined type

RTA 4- “ALDOSTERONE RESISTANCE”-see hyperkalemia (Aldosterone normally dumps H+ and K+)

Question 7

What causes a metabolic acidosis WITH a gap? How does Chloride get affected?

Answer 7

*All have a NORMAL Cl”. Large anion gap always has an normal chloride.

M-methanol
U-uremia
D-DKA
P-paraldehyde
I--Isoniazid
L-lactic acid
E-ethanol/ethylene glycol
S-salicylates