Acid-Base Balance

Question 1

two types of acid in the body

Answer 1

volatile and non-volatile

Question 2

volatile acid

Answer 2

CO2

Question 3

non-voltatile acids (fixed acids)

Answer 3

Sulfuric acid

Phosphoric acid

Question 4

Fixed acids overproduced in dz or ingested

Answer 4

ketoacids, lactic acid, salicylic acid

Question 5

major extracellular buffer

Answer 5

HCO3-

Question 6

minor extracellular buffer (most important as a urinary buffer)

Answer 6

H2PO4-

Question 7

excretion of H+ as H2PO4-

Answer 7

titratable acid

Question 8

major intracellular buffer

Answer 8

hemoglobin

Question 9

deoxyhemoglobin vs oxyhemoglobin - which is the better buffer?

Answer 9

deoxyhemoglobin

Question 10

pH = pKa + log[A-]/[HA]

Answer 10

Henderson-Hasselbalch

Question 11

pH = pKa + log ([HCO3-] / 0.03 x PaCO2)

Answer 11

pH arterial blood

Question 12

PCO2 = 1.5[HCO3-] + 8 ± 2

Answer 12

Winter’s formula

Question 13

used to measure the appropriateness of the compensatory response and to evaluate for a mixed acid/base disorder.

Answer 13

winter’s formula

Question 14

If measured PCO2 is higher than expected →

Answer 14

additional primary respiratory acidosis

Question 15

If measured PCO2 is lower than expected –>

Answer 15

additional primary respiratory alkalosis

Question 16

Serum anion gap =

Answer 16

[Na+] – ([HCO3-] + [Cl-])

Sodium - (bicarb + chloride)

Question 17

mnemonic for ↑ Serum anion gap metabolic acidosis (aka “gap acidosis”)

Answer 17

MUDPILERS

Question 18

M in mudpilers

Answer 18

Methanol (formate), Metformin

Question 19

U in mudpilers

Answer 19

Uremia—advanced (chronic) renal failure—vs. early renal failure, which may cause normal anion gap metabolic acidosis

Question 20

D in mudpilers

Answer 20

Diabetic ketoacidosis (β-hydroxybutyrate, acetoacetate)

Question 21

P in mudpilers

Answer 21

Paraldehyde, Phenformin

Question 22

I in mudpilers

Answer 22

Iron, Isoniazid

Question 23

L in mudpilers

Answer 23

Lactic acidosis—shock, hypoxia, poor tissue perfusion; carbon monoxide, cyanide

Question 24

E in mudpilers

Answer 24

Ethanol ketoacidosis (β-hydroxybutyrate, acetoacetate), Ethylene glycol (glycolate, oxalate)

Question 25

R in mudpilers

Answer 25

Rhabdomyolysis

Question 26

S in mudpilers

Answer 26

Salicylates—with concomitant respiratory alkalosis; prolonged Starvation ketoacidosis (β-hydroxybutyrate, acetoacetate)

Question 27

Mneumonic for Normal anion gap metabolic acidosis (aka, hyperchloremic metabolic acidosis, “non-gap acidosis”)

Answer 27

“FUSED CARS”:

Question 28

F in fused cars

Answer 28

Fistula (small bowel, pancreatic) → loss of HCO3-

Question 29

U in fused cars

Answer 29

Ureterogastric conduits (eg, urine-diverting colostomy) → loss of HCO3-

Question 30

S in fused cars

Answer 30

Saline administration (ie, saline worsens metabolic acidosis!) → gain of Cl-

Question 31

E in fused cars

Answer 31

Endocrine—eg, hyperparathyroidism (a cause of type 2 renal tubular acidosis), Addison’s disease (aldosterone deficiency)

Question 32

D in fused cars

Answer 32

Diarrhea → loss of HCO3-

Question 33

C in fused cars

Answer 33

Carbonic anhydrase inhibitors (eg, acetazolamide)(most common cause of type 2 renal tubular acidosis in adults) → loss of HCO3-

Question 34

A in fused cars

Answer 34

Acid infusion (eg, NH4Cl; hyperalimentation with TPN (total parenteral nutrition) if arginine HCl or lysine HCl are used as amino acids) → gain of Cl-

Question 35

R in fused cars

Answer 35

- type 1 (↓ distal tubule H+ secretion): hypokalemia, urine pH>5.5 - type 2 (↓ proximal tubule HCO3- reabsorption): hypokalemia, urine pH<5.5.

Question 36

S in fused cars

Answer 36

Spironolactone - blocks aldosterone receptors

Question 37

Normal anion gap metabolic acidosis is caused by

Answer 37

loss of HCO3- or gain of Cl-, both of which usually result in hyperchloremic metabolic acidosis:

Question 38

gain of Cl- is usually compensated by

Answer 38

loss of HCO3- → hyperchloremic metabolic acidosis

Question 39

- loss of HCO3- is usually compensated by

Answer 39

Cl- retention → hyperchloremic metabolic acidosis