acid/base imbalance and disturbance

Question 1

What is an acid?

Answer 1

A molecule that releases a hydrogen ion.

Question 2

What is a base?

Answer 2

A molecule that accepts a proton.

Question 3

What is the normal pH of ECF?

Answer 3

7.35-7.45.

Question 4

Is intracellular or extracellular pH higher?

Answer 4

Extracellular.

Question 5

How does the body deal with daily acid load?

Answer 5

1. Buffers
2. Lungs via alveolar ventilation
3. Kidneys via renal excretion of H+.

Question 6

What is the buffer system in the ECF?

Answer 6

Carbonic acid.

Question 7

What is an important buffer system in the renal tubular and intracellular fluids?

Answer 7

Phosphate buffer system.

Question 8

What is responsible for most intracellular fluid buffering?

Answer 8

Protein buffer system.

Question 9

How does systemic acidosis impact breathing?

Answer 9

It stimulates the respiratory system to increase ventilation to blow off CO2.

Question 10

Where is most bicarb reabsorbed?

Answer 10

Proximal tubule.

Question 11

What is necessary for the kidney to generate acids?

Answer 11

1. Reabsorbing all the filtered HCO3
2. Excrete ammonium
3. Excrete titratable acids.

Question 12

What bicarb CO2 level indicates metabolic alkalosis?

Answer 12

Greater than 30.

Question 13

What bicarb CO2 level indicates metabolic acidosis?

Answer 13

Less than 22.

Question 14

Give the equation for metabolic acidosis in assessing if someone’s lungs are responding to a kidney problem.

Answer 14

pCO2 = [(1.5 x HCO3] + 8 +/- 2).

Question 15

How do we calculate the anion gap?

Answer 15

AG = Na – (Cl + HCO3). Should equal around 12.

Question 16

What is the formula for osmolar gap?

Answer 16

2 x Na + (BUN/2.8) + (glucose/18).

Question 17

What should the osmolar gap be?

Answer 17

Less than 10.

Question 18

Describe metabolic acidosis.

Answer 18

Low bicarb, low pH, low pCO2 (from hyperventilation).

Question 19

What causes metabolic acidosis?

Answer 19

Loss of bicarb, addition of acid, or rapid addition of non bicarb solutions to the ECF.

Question 20

What is the difference between type A and B lactic acid diagnosis?

Answer 20

Type A always has hypotension and edema, and type B is just inappropriate formation of lactic acid that may be caused by things like drugs, liver problems, and mitochondrial disorders.

Question 21

Describe ketoacidosis.

Answer 21

Absent or low levels of insulin cause the body to use alternate energy sources like free fatty acids. These convert to ketoacids, causing more acid in the body.

Question 22

What is alcoholic ketoacidosis?

Answer 22

Often due to nausea/vomiting causing a decrease in the insulin to glucose ratio, leading to more ketoacid production and lower body pH. Can also happen in withdrawal with volume depletion and starvation leading to ketoacid production.

Question 23

How can renal failure lead to acidosis?

Answer 23

Lower number of functioning nephrons leads to a lowered ability to excrete acids. This leads to an accumulation of anions due to metabolic adjustments, leading to an elevated anion gap.

Question 24

What poisons impact serum osms?

Answer 24

Methanol and ethylene glycol.

Question 25

What do we use to measure non-gap metabolic acidosis?

Answer 25

Urine anion gap.

Question 26

What is the formula for urine anion gap?

Answer 26

Una + Uk – Ucl.

Question 27

What is a normal urine anion gap?

Answer 27

20-50.

Question 28

What should happen to the urine anion gap in non-gap metabolic acidosis?

Answer 28

It should become more negative due to increased NH4Cl excretion.

Question 29

In terms of acid-base, what happens with diarrhea?

Answer 29

We lose a lot of bicarb, leading to metabolic acidosis.

Question 30

What causes RTA?

Answer 30

Either an inability to reabsorb filtered bicarb or impaired excretion of ammonium chloride.

Question 31

What is proximal RTA (type 2)?

Answer 31

Inability to reabsorb bicarb in the proximal tubule; leads to non-gap metabolic acidosis.

Question 32

What is Fanconi syndrome?

Answer 32

Proximal tubular dysfunctions associated with proximal RTA.

Question 33

What is a common cause of proximal RTA in adults?

Answer 33

Multiple myeloma.

Question 34

What is distal RTA (type 1)?

Answer 34

Inability to secrete excess protons as ammonium chloride or sodium dihydrogen phosphate.

Question 35

What factors can be involved in a distal RTA?

Answer 35

1. Inability to generate ammonium 2. Inability to do medullary recycling of ammonia 3. Inability to generate a negative tubular potential in the CCD 4. Inability to secrete acid into the tubule.

Question 36

What is Sjogrens syndrome?

Answer 36

Disease in adults that can impact the proton ATPase and lead to distal RTA.

Question 37

A patient walks in and seems totally fine. You find they have a super low bicarb. What could it be?

Answer 37

Distal RTA; this RTA is not systemic so they will have very pronounced metabolic acidosis but seem ok.

Question 38

What is RTA caused by hyperaldosteronism?

Answer 38

Inability for aldosterone to facilitate excretion of H+ bound to ammonia.

Question 39

Type 4 RTA (hyperaldosteronism) is always associated with…

Answer 39

Hyperkalemia.

Question 40

Type 4 RTA is common in…

Answer 40

Diabetics and those with renal impairment.

Question 41

In metabolic alkalosis, how do the lungs respond?

Answer 41

With hypoventilation to hold onto more CO2 and drop pH.

Question 42

Describe the pathophysiology of metabolic alkalosis.

Answer 42

1. There is either an intake of excess exogenous alkali or loss of H+ via vomiting or diuretics. 2. The kidneys are unable to handle this high amount of HCO3, either through low GFR, low volume, low potassium, or high aldosterone. 3. Low GFR causes a low filtration and excess HCO3 in the body; low volume can lead to increased HCO3 reabsorption or increased H+ secretion; low potassium leads to increased H+ secretion; increased aldosterone increases NH4+ excretion.

Question 43

How do we assess volume status in metabolic alkalosis?

Answer 43

Urine chloride! Bicarb binds to sodium to be excreted so sodium isn’t reliable.

Question 44

What does a urine chloride less than 15 indicate?

Answer 44

Metabolic alkalosis due to volume loss; Gastric fluid loss or post-diuretic therapy.

Question 45

What does a urine chloride more than 20 indicate?

Answer 45

Metabolic acidosis with some outside cause that has caused us to gain some fluid back after a volume loss; could be hyperaldosteronism, Cushing’s syndrome, steroids.

Question 46

What are the most common causes of metabolic alkalosis?

Answer 46

Vomiting, diuretics, primary hyperaldosteronism.