HLK Week 6

Question 1

The most direct measurement of HCO3-:

Answer 1

Total venous CO2 (almost all CO2 is stored as HCO3-)

Question 2

True or false: arterial and venous blood gases will equilibrate during cardiopulmonary arrest.

Answer 2

False: arterial blood samples should always be taken for the most accurate measure of pH and PCO2.

Question 3

Respiratory alkalosis and its compensation:

Answer 3

• Primary defect: PCO2 less than 40, pH greater than 7.4
• Compensation (acute): 2 mEq decrease in HCO3- for every 10 mmHg drop in PCO2
• Compensation (chronic): 5 mEq decrease in HCO3- for every 10 mmHg drop in PCO2

Question 4

Respiratory acidosis and its compensation:

Answer 4

• Primary defect: PCO2 greater than 40, pH less than 7.4
• Compensation (acute): 1 mEq increase in HCO3- for every 10 mmHg increase in PCO2
• Compensation (chronic): 3.5 mEq increase in HCO3- for every 10 mmHg increase in PCO2

Question 5

Metabolic acidosis and its compensation:

Answer 5

• Primary defect: HCO3- less than 24 mEq, pH less than 7.4

- Compensation: 1.3 mmHg drop in PCO2 for every 1 mEq drop in HCO3-

Question 6

Metabolic alkalosis and its compensation:

Answer 6

• Primary defect: HCO3- greater than 24 mEq, pH greater than 7.4
• Compensation: 0.7 mmHg increase in PCO2 for every 1 mEq increase in HCO3-

Question 7

True or false: in a mixed acid-base disorder, there can be multiple metabolic disorders but never more than one respiratory disorder.

Answer 7

True

Question 8

Sources of acid in the body:

Answer 8

• Diet and metabolism (e.g., protein from diet, CO2 from cells)
• GI (upper gut produces acid, lower gut produces bicarb; net production of acid)
• Non-volatile acids like HCl and lactic acid

Question 9

Why does vomiting result in alkalosis, whereas diarrhea results in acidosis?

Answer 9

Acid is produced in the upper GI tract and is lost through vomiting. Bicarb is produced int he lower GI tract and is lost through diarrhea.

Question 10

What makes a buffer good for regulating body acid?

Answer 10

The pK needs to be within one unit of the pH.

Question 11

What regulates the concentration of HCO3- and CO2 in the body?

Answer 11

• HCO3- is regulated by the kidneys

- CO2 is regulated by the lungs

Question 12

Explain how acidosis produces a low bicarb level.

Answer 12

Bicarb is the buffer. As acid is produced it combines with bicarb, lowering bicarb levels.

Question 13

Explain how a constant level of bicarb is maintained in the body.

Answer 13

• Net renal bicarb regeneration (quantified as net acid excretion)

EQUALS

• Bicarb lost buffering endogenously produced acid

Question 14

How do the kidneys reabsorb bicarb, and where does it happen?

Answer 14

In the proximal tubule, they secrete H+ into the lumen via the sodium/hydrogen pump, this combines with filtered bicarb to produce carbonic acid, which dissociates into CO2 and water. These are reabsorbed into the renal tubular cells, where they recombine to form bicarb and H+. The bicarb exits into the interstitium, and the H+ is secreted back into the lumen to combine with more bicarb, starting the cycle over again.

Question 15

Where does production of new bicarbonate occur?

Answer 15

In the distal nephron via protonation of phosphate

In the proximal tubule via production of ammonium

Question 16

Explain how acidosis leads to secretion of ammonium

Answer 16

Acidosis stimulates the reuptake of filtered glutamine, which dissociates into bicarb and ammonium. Secreted ammonium lowers acidity.

Question 17

Production of new bicarb is tied to the secretion of which molecules in the kidney?

Answer 17

• HPO4–

- NH4+

Question 18

Which type of casts indicates renal failure?

Answer 18

Broad casts

Question 19

Describe the morphology of broad casts:

Answer 19

• Usually 2 - 6 times the size of normal casts

- Appear waxy, granular or cellular

Question 20

Name 2 things that cause alkaline urine:

Answer 20

• Renal tubular acidosis

- UTI

Question 21

Causes of D- versus L-lactate anion gap acidosis:

Answer 21

• D lactate is caused by bacterial overgrowth in the gut
• L lactate comes from anaerobic respiration

Side note: L lactate acidosis occurs in sepsis because of tissue hypoxia leading to anaerobic respiration

Question 22

An important thing to remember about metabolic alkalosis:

Answer 22

Requires both a generation of metabolic alkalosis (loss of H+ through GI or kidneys) and maintenance of alkalosis (impairment in renal bicarb excretion).

Question 23

MOA for sulfonamides:

Answer 23

Folic acid synthesis inhibitor

Question 24

MOA for quinolones:

Answer 24

DNA topoisomerase II inhibitor

Question 25

MOA for nitrofurantoin:

Answer 25

Protein synthesis inhibitor via ribosomal inactivation

Question 26

Mnemonic for remembering the causes of anion gap acidoses:

Answer 26

- KUSSMAUL (Kussmaul respirations also seen with acidosis)
K = ketosis
U = uremia
SS = salicylate poisoning
M = methanol
A = alcohol (originally "aethylene")
U = uremia
L = lactic acidosis

Question 27

What would Bactrim be indicated for in the context of this class?

Answer 27

UTI

Question 28

What would quinolones be indicated for in the context of this class?

Answer 28

• UTI

- Gonorrhea

Question 29

Mnemonic for causes of anion gap acidosis:

Answer 29

GOLDMARK
G = glycols
O = oxyproline
L = L-lactate
D = D-lactate
M = methanol
A = Aspirin
R = renal failure
K = ketosis

Question 30

Mnemonic for causes of respiratory acidosis:

Answer 30

CHAMPS
C = CNS diseases
H = hypoxia
A = anxiety
M = mechanical ventilation
P = progesterone
S = Salicylates/sepsis

Question 31

Mnemonic for causes of metabolic alkalosis:

Answer 31

CLEVER PD
C = contraction
L = licorice
E = endocrine
V = vomiting
E = excess alkali (GI)
R = refeeding alkalosis
P = post hypercapnia
D = diuretics

Question 32

Causes of leukocyturia:

Answer 32

Infxn, neoplasms, AIN, glomerular diseases, strictures, stones, interstitial cystitis

Question 33

Why do granular casts indicate intrinsic kidney disease?

Answer 33

They’re composed of degenerating tubular cells, which indicates necrosis.