Acid-Base (Don's class)

Question 1

Acid-base physiology is all about……..

Answer 1

H+ ion concentrations

Question 2

Normal ECF H+ concentration is…..

Answer 2

~ 40nEq/L

Question 3

An acid is a proton (H+) _____.

Answer 3

donor

Question 4

A base is a proton (H+) ______.

Answer 4

acceptor

Question 5

A weak acid or base _______ donates or accepts a proton

Answer 5

reversibly

Question 6

A weak acid the equation looks like this:

Answer 6

HA <=> H+ + A-

Question 7

The Henderson–Hasselbalch equation describes the relationship between _____,_____and______.

Answer 7

pH, PaCO2, and serum bicarbonate.

Question 8

the solubility coefficient for CO2 is:

Answer 8

is 0.03 mmol/mm Hg at body temperature.

This means that 0.03 millimole of H2CO3 (carbonic acid)is present in the blood for each mm Hg PCO2measured.

Question 9

Buffers are most efficient when:

Answer 9

pH=pKa

Question 10

Body Buffers: (5)

Answer 10

Bicarbonate (H2CO3 / HCO3)
Hemoglobin
Intracellular proteins
Phosphate (H2PO4- /HPO42-)
Ammonia (NH3/NH4)

Question 11

Buffer systems do not eliminate H+from or add H+to the body but only…..

Answer 11

keep them tied up until balance can be re-established.

Question 12

The three primary systems that regulate H+ concentration in the body fluids to prevent acidosis or alkalosis:

Answer 12

1. Chemical acid-base buffer system

2.Respiratory center (regulate CO2 removal and therefore H2CO3- from the ECF)

3.The kidneys (excrete acid or alkaline urine) MOST POWERFUL

Question 13

Bicarbonate Buffer System Equation:

Answer 13

H2O + CO2 <=> H2CO3 <=> H+ + HCO3-

CO2 combines with water to form H2CO3 which rapidly dissociates into H+ and HCO3-

(H2CO3= Carbonic acid)

Question 14

Hydration of CO2 is catalyzed by _____ _____.

Answer 14

Carbonic anyhdrase

Question 15

The bicarbonate buffer is effective against _______ but not ________ acid-base disturbances

Answer 15

metabolic
NOT respiratory

Question 16

The pKa of bicarbonate is:

Answer 16

6.1

Question 17

The bicarbonate Buffer System is the…..

Answer 17

the most powerful extracellular buffer in the body.

Question 18

How do the kidneys compensate during Acidosis?

Answer 18

Increased HCO3- re-absorbtion:
-CO2 combines with water to form H2CO3 which rapidly dissociates into H+ and HCO3-

Question 19

H+ is secreted into the proximal tubule and ________ is reabsorbed to blood (renal compensation of acidosis)

Answer 19

bicarbonate

H+ in the tubule combines with filtered HCO3- to form carbonic acid
Carbonic anhydrase hydrolyzes this to water and CO2 which goes into the cell replacing the original CO2

Question 20

For for each________ reabsorbed, a ______must be secreted.

Answer 20

HCO3−
H+

Question 21

The epithelial cells of the proximal tubule, the thick segment of the ascending loop of Henle, and the early distal tubule all…….

Answer 21

secrete H+into the tubular fluid by sodium-hydrogen counter-transport,

Question 22

______ of filtered bicarbonate is reabsorbed in the _______ _______.
10-20% reabsorbed in the ______ ______.

Answer 22

80-90%
proximal tubule
distal tubule

Question 23

*In the distal tubule a______ ______exists which can establish a steep gradient for _______ urine

Answer 23

H+ pump
acidifying

Question 24

Intercalated Cells of Collecting Duct do what job?

Answer 24

Reabsorption & Secretion of Bicarbonate

Question 25

Type A intercalated cells are especially important in eliminating_____ _______ while reabsorbing ______ in acidosis.

Answer 25

hydrogen ions bicarbonate

Question 26

Type B cells secrete _______ into the tubular lumen while reabsorbing _______ ______ in alkalosis

Answer 26

bicarbonate hydrogen ions

Question 27

H+ secreted in tubule lumen can combine with HPO42- to form H2PO4- that is......

Answer 27

not re-absorbable and becomes trapped in urine. HPO4/2—hydrogen phosphate H2PO4—dihydrogen phosphate

Question 28

Phosphate has pK of ___ which in acidic urine allow to be more effective buffer

Answer 28

6.8

Question 29

The total  buffering power of the _____ _____ in the extracellular fluid is much less than that of the _________ buffering  system.

Answer 29

phosphate  system bicarbonate

Question 30

The  phosphate buffer  is especially important in the tubular fluids of the kidneys for two reasons:

Answer 30

(1) phosphate usually becomes greatly concentrated in the tubules, thereby increasing the buffering power of the phosphate system. (2) the tubular fluid usually has a considerably lower pH than the extracellular fluid does, bringing the operating range of the buffer closer to the pK (6.8) of the system.

Question 31

Tubular Buffer =

Answer 31

Ammonium (NH4) Production & Secretion

Question 32

Ammonium (NH4): Important tubular fluid buffer that works in the ___, ___, and _____.

Answer 32

PT, TAL, & DT Bicarbonate generated in synthesis process

Question 33

Ammonium is synthesized from _____

Answer 33

glutamine.

Question 34

Collecting Tubules: ____ combines with _____ to form _____ which is excreted.

Answer 34

H+ NH3 NH4 Bicarbonate also generated in synthesis process

Question 35

With chronic acidosis, the dominant mechanism by which acid is eliminated is excretion of ___

Answer 35

NH4 (Ammonium)

Question 36

This process also provides the most important mechanism for generating new bicarbonate during chronic acidosis

Answer 36

Ammonium Production & Secretion (tubular buffer)

Question 37

The _____is secreted into the  tubular  lumen by a _____-_______ _____ in exchange for sodium, which is reabsorbed.

Answer 37

NH4+  counter-transport mechanism The HCO3− is transported across the basolateral membrane, along with the reabsorbed Na+, into the interstitial fluid and is taken up by the peritubular capillaries.

Question 38

Metabolic alkalosis is mainly possible in 2 situations:

Answer 38

1. Na+ depletion: more sodium is reabsorbed in the PT (Cl- moves with it to preserve electroneutrality) HCO3- must be reabsorbed (contraction alkalosis) 2. Increased aldosterone (mineralocorticoid) activity increases Na+ reabsorption and H+ secretion in the distal tubule

Question 39

Base excess is defined as the amount of acid or base that must be added to return blood pH to 7.4 with PaCO2 = 40 mmHg and temp 37o C Positive value indicates _______. Negative value indicates _______.

Answer 39

metabolic alkalosis metabolic acidosis

Question 40

Metabolic Alkalosis: Causes

Answer 40

1. Loss of acid from the extracellular space: -loss of gastric fluid -acid loss in urine (hyperaldosteronism) K+ deficiency -loss of acid in stool 2. Excessive HCO3- loads: -oral or parenteral Bicarb -NaHCO3- dialysis

Question 41

Factors That Maintain Metabolic Alkalosis:

Answer 41

-decreased GFR -Hypokalemia -volume contraction (HCO3 reabsorption) -Hypochloremia -Aldosterone

Question 42

Metabolic Alkalosis: 1. PaCO2 increases ∼___-___ mmHg per 1 mEq/L increase in [HCO3−] 2. The last two digits of the pH should approximate the [HCO3−] + ___.

Answer 42

0.5-0.6 mmHg 15

Question 43

Elevated Anion Gap Metabolic Acidosis: 3 diseases: Toxins:

Answer 43

Three diseases: Uremia Ketoacidosis Lactic acidosis Toxins: Methanol Ethylene glycol Salicylates Paraldehyde

Question 44

Normal Anion Gap Metabolic Acidosis: Causes

Answer 44

Renal tubular acidosis Diarrhea Carbonic anhydrase inhibition Ureteral diversions Early renal failure Hydronephrosis HCl administration Saline administration

Question 45

Potassium increases ___ mEq/L for each 0.1 unit decrease in pH

Answer 45

0.6

Question 46

Physiologic effects of acidosis:

Answer 46

A rightward shift is seen in the oxy-hemoglobin dissociation curve Cardiac contractility is decreased There is decreased responsiveness to catecholamines Potassium increases 0.6 mEq/L for each 0.1 unit decrease in pH

Question 47

Treating Metabolic Acidosis: (3)

Answer 47

-Treat underlying cause (e.g. hypovolemia, anemia, cardiogenic shock -NaHCO3 (Do not give to patient with respiratory failure as CO2 will go up -Refractory acidosis may require dialysis

Question 48

Treating alkalosis:

Answer 48

-IV HCl is used in rare cases -Spironolactone if increased mineralocorticoid activity -Diuretics are the cause of chloride sensitive metabolic alkalosis

Question 49

-Diuretics are the cause of chloride sensitive _____ ______.

Answer 49

metabolic alkalosis

Question 50

Hypokalemia will also augment_____ ________.

Answer 50

H+ secretion

Question 51

Halving minute ventilation _____ PaCO2 and _____ cerebral blood flow.

Answer 51

doubles and doubles

Question 52

Respiratory alkalosis may be a sign of......

Answer 52

pain, anxiety, hypoxemia, central nervous system disease, or systemic sepsis.

Question 53

In metabolic acidosis, an excess of H+ over HCO3− occurs in the  tubular  fluid primarily because of decreased _____ _____ ____.

Answer 53

filtration of HCO3−.

Question 54

Anion Gap calculation:

Answer 54

[Na+] - ([Cl-] + [HCO3-]) Normal value 140 - (104 +24) = 12 mEq/L Usually 7-14 mEq/L

Question 55

Respiratory acidosis: Acute compensation

Answer 55

1 mEq/L INCREASE in HCO3- for every 10 mmHg increase in CO2 (usually from 40 mmHg

Question 56

Respiratory Acidosis: Chronic compensation

Answer 56

expect a 4 mEq/L INCREASE in HCO3- for every 10 mmHg increase in CO2

Question 57

Metabolic Acidosis: CO2 DECREASES ____ X the decrease in HCO3- (Usually from 24 mEq/L)

Answer 57

CO2 DECREASE 1.2 times the decrease in HCO3-

Question 58

Acute Respiratory Alkalosis Compensation:

Answer 58

2 mEq/L DECREASE in HCO3- for every 10 mmHg DECREASE in CO2

Question 59

Chronic Respiratory Alkalosis Compensation:

Answer 59

4 mEq/L DECREASE in HCO3- for every 10 mmHg DECREASE in CO2

Question 60

Metabolic Alkalosis Compensation:

Answer 60

CO2 INCREASE by 0.7 X the INCREASE in HCO3-