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CV Anesthesia, plus renal (Skuta) > Acid-Base (Don's class) > Flashcards

Acid-Base (Don's class) Flashcards

1
Q

Acid-base physiology is all about……..

A

H+ ion concentrations

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2
Q

Normal ECF H+ concentration is…..

A

~ 40nEq/L

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3
Q

An acid is a proton (H+) _____.

A

donor

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4
Q

A base is a proton (H+) ______.

A

acceptor

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5
Q

A weak acid or base _______ donates or accepts a proton

A

reversibly

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6
Q

A weak acid the equation looks like this:

A

HA <=> H+ + A-

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7
Q

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

A

pH, PaCO2, and serum bicarbonate.

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8
Q

the solubility coefficient for CO2 is:

A

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.

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9
Q

Buffers are most efficient when:

A

pH=pKa

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10
Q

Body Buffers: (5)

A

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

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11
Q

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

A

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

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12
Q

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

A
  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

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13
Q

Bicarbonate Buffer System Equation:

A

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

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

(H2CO3= Carbonic acid)

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14
Q

Hydration of CO2 is catalyzed by _____ _____.

A

Carbonic anyhdrase

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15
Q

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

A

metabolic
NOT respiratory

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16
Q

The pKa of bicarbonate is:

A

6.1

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17
Q

The bicarbonate Buffer System is the…..

A

the most powerful extracellular buffer in the body.

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18
Q

How do the kidneys compensate during Acidosis?

A

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

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19
Q

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

A

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

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20
Q

For for each________ reabsorbed, a ______must be secreted.

A

HCO3−
H+

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21
Q

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

A

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

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22
Q

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

A

80-90%
proximal tubule
distal tubule

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23
Q

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

A

H+ pump
acidifying

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24
Q

Intercalated Cells of Collecting Duct do what job?

A

Reabsorption & Secretion of Bicarbonate

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25
Q

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

A

hydrogen ions
bicarbonate

26
Q

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

A

bicarbonate
hydrogen ions

27
Q

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

A

not re-absorbable and becomes trapped in urine.

HPO4/2—hydrogen phosphate

H2PO4—dihydrogen phosphate

28
Q

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

A

6.8

29
Q

The total buffering power of the_____ _____in the extracellular fluid is much less than that of the _________buffering system.

A

phosphate system
bicarbonate

30
Q

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

A

(1)phosphateusually becomes greatly concentrated in the tubules, thereby increasing thebuffering power of thephosphatesystem.

(2) the tubular fluid usually has a considerably lower pH than the extracellular fluid does, bringing the operating range of thebuffercloser to the pK (6.8) of thesystem.

31
Q

Tubular Buffer =

A

Ammonium (NH4) Production & Secretion

32
Q

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

A

PT, TAL, & DT

Bicarbonate generated in synthesis process

33
Q

Ammonium is synthesized from _____

A

glutamine.

34
Q

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

A

H+
NH3
NH4

Bicarbonate also generated in synthesis process

35
Q

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

A

NH4 (Ammonium)

36
Q

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

A

Ammonium Production & Secretion (tubular buffer)

37
Q

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

A

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 peritubularcapillaries.

38
Q

Metabolic alkalosis is mainly possible in 2 situations:

A
  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
39
Q

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 _______.

A

metabolic alkalosis
metabolic acidosis

40
Q

Metabolic Alkalosis: Causes

A
  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
41
Q

Factors That Maintain Metabolic Alkalosis:

A

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

42
Q

Metabolic Alkalosis:
1. PaCO2increases ∼___-___ mmHg per 1 mEq/L increase in [HCO3−]

  1. The last two digits of the pH should approximate the [HCO3−] + ___.
A

0.5-0.6 mmHg
15

43
Q

Elevated Anion Gap Metabolic Acidosis:
3 diseases:
Toxins:

A

Three diseases:
Uremia
Ketoacidosis
Lactic acidosis

Toxins:
Methanol
Ethylene glycol
Salicylates
Paraldehyde

44
Q

NormalAnion Gap Metabolic Acidosis: Causes

A

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

45
Q

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

A

0.6

46
Q

Physiologic effects of acidosis:

A

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

47
Q

Treating Metabolic Acidosis: (3)

A

-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

48
Q

Treating alkalosis:

A

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

49
Q

-Diuretics are the cause of chloride sensitive _____ ______.

A

metabolic alkalosis

50
Q

Hypokalemia will also augment_____ ________.

A

H+ secretion

51
Q

Halving minute ventilation _____ PaCO2 and _____ cerebral blood flow.

A

doubles and doubles

52
Q

Respiratory alkalosis may be a sign of……

A

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

53
Q

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

A

filtration of HCO3−.

54
Q

Anion Gap calculation:

A

[Na+] - ([Cl-] + [HCO3-])

Normal value 140 - (104 +24) = 12 mEq/L
Usually 7-14 mEq/L

55
Q

Respiratory acidosis: Acute compensation

A

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

56
Q

Respiratory Acidosis: Chronic compensation

A

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

57
Q

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

A

CO2 DECREASE 1.2 times the decrease in HCO3-

58
Q

Acute Respiratory Alkalosis Compensation:

A

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

59
Q

Chronic Respiratory Alkalosis Compensation:

A

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

60
Q

Metabolic Alkalosis Compensation:

A

CO2 INCREASE by 0.7 X the INCREASE in HCO3-

CV Anesthesia, plus renal (Skuta) (11 decks)

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