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Acid - Base Balance Flashcards

1
Q

Regular Body pH

A

7.4

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2
Q

Acidosis

A

pH < 7.4

high hydrogen ion concentration

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3
Q

Alkalosis

A

pH > 7.4

low hydrogen ion concentration

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4
Q

change in pH resulting in death

A

a change of 0.6 in either direction can result in death

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5
Q

Normal Concentration of Hydrogen Ions

A

4x10^-8 eq/L or 4x10^5 meq/L

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6
Q

Body Buffers

A
  1. Intracellular Fluid
  2. Blood
  3. Interstitial Fluid
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7
Q

Intracellular Fluid as a Buffer

A
  1. Protein (non-exchangable)
  2. HPO4^2-
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8
Q

Blood as a Buffer

A
  1. Hemoglobin
  2. Protein (albumin)
  3. HCO3^-
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9
Q

Interstitial Fluid as a Buffer

A
  1. HCO3-
  2. HPO4^2- (Kidney)
  3. NH3 (Kidney)
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10
Q

Lines of Defense in an Acid Base Crisis

A
  1. Hemoglobin and Proteins
  2. HCO3^- buffer system (most important)
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11
Q

Protein Anion Buffer System

A

75% of the body’s buffering power
not physiologically significant

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12
Q

Protein Anion Buffer System Reactions

A

R-COOH <-> R-COO- + H+
R-NH2 + H+ <-> R-NH3+

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13
Q

Major ECF Buffer Systems

A
  1. Bicarbonate
  2. Phosphate
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14
Q

CO2/HCO3- Bicarbonate Buffer System

A

Most important ECF buffer

regulation from Lungs, Kidneys, Blood Buffer System

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15
Q

Bicarbonate Buffer System Reaction

A

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

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16
Q

Henderson-Hasselbach Equation for Bicarbonate Buffer System

A

pH= pK + log([HCO3-]/[H2CO3])
or pH = pK +log([HCO3-]/0.3PCO2)

pK = 6.1

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17
Q

Normal Ratio of HCO3 to H2CO3

A

20:1

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18
Q

Bicarbonate Buffer System

A

mixture of NaHCO3 and H2CO3

NaHCO3 can react with an acid to make H2CO2, H2CO3 can react with a base to make NaHCO3

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19
Q

Carbonic Anhydrase

A

enzyme that helps convert CO2 in blood to bicarbonate(HCO3) in the bicarbonate buffer system

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20
Q

When do buffers work best?

A

When pH is close numerically to pK

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21
Q

Why is the Bicarbonate Buffer system the most important buffer system?

A
  1. can be regulated by lungs and kidney (CO2&HCO3-)
  2. Erythrocytes are capable of “Chloride shift”
  3. Abundant supplies of Bicarbonate anion are available for buffering (HCO3-:H2CO3, 20:1)
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22
Q

Chloride Shift

A
  1. Chloride transported into the blood cell
  2. HCO3- buffer transport is favored out of the cell, into plasma
23
Q

Phosphate Buffer System Reactions

A

HCl + Na2HPO4 <-> NaH2PO4 + NaCl
NaOh + NaH2PO4 <-> Na2HPO4 +H2O

24
Q

Phosphate Buffer system

A

more active in the kidney tubule system than ECF

1/12 concentration in ECF compared to Bicarbonate Buffer System

tubular fluid has low pH that is closer to pK of the buffer

25
Q

3 levels of pH regulation

A
  1. Bicarbonate Buffer System
  2. Respiratory System
  3. Renal Buffer System
26
Q

Bicarbonate Buffer System in pH regulation

A

weak link, can become saturated

27
Q

Respiratory System role in pH regulation

A

fast acting, within minutes,

Central Receptor and Peripheral Chemoreceptors

buffer power 2x greater than all chemical buffer systems

28
Q

Respiratory System role in pH regulation

Central Receptor(Medulla Oblongata)

A

detects rise in [H+], causes increase in RR

29
Q

Respiratory System role in pH regulation

Peripheral Chemorecptors

A

detects decrease in pH, pO2, increase in pCO2 causes increased RR

30
Q

Respiratory System role in pH regulation

Flaw of Respiratory System in pH regulation

A

cannot stop breathing so it is less effective in an alkalotic crisis

31
Q

Renal Buffer System

A

recruited after 3-5 hours if respiratory system fails to compensate

reabsorbs base while excreting acid

Works using secretion and reabsorbtion

32
Q

Renal Buffer System

Secretion

A

secretes H+, leading to it being excreted

counter transport of Na+ and H+

secondary active transport,

33
Q

Renal Buffer System

Reabsorbtion

A

reabsorbs HCO3-, prevents its excretion

HCO3- from the glomerular filtrate will combine with H+ to form H2CO3 which will then form CO2 + H2O

34
Q

Renal Buffer System

In the Proximal Convoluted Tubule

A

for every Na+ reabsorbed
1. H+ secreted
2. HCO3- reabsorbed
3. H+ combines with HCO3- to form H2CO3

both K+ and H+ compete for cotransport with Na+

35
Q

In the Distal Convoluted Tubule

A
  1. H+ is secreted
  2. K+ stays in the ECF
  3. H+ is buffered in the tubule by HPO4-2 and NH3
  4. NH4+ is the excretory form of H+
36
Q

Normal pCO2 level

A

40 mmHg

respiratory proxy

pCO2 = H+ = acid

37
Q

Normal HCO3- level

A

24 mEq/L

metabolism proxy

HCO3- = OH- = base

38
Q

Metabolic Acidosis

A

acidic condition resulting from metabilism problem

Diabetic Ketoacidosis

39
Q

Respiratory Acidosis

A

acidic condition resulting from an inability to maintain normal ventilation rate or move normal respiratory volumes

Chronic Emphysema, Asthma Attack

40
Q

Metabolic Acidosis Signs

A

pH<7.4
HCO3-<24mEq/L
pCO2<40mmHg (increased ventilation rate)

HCO3- is the cause, pCO2 is the compensation

41
Q

Respiratory Acidosis Signs

A

pH<7.4
pCO2>40mmHg (poor breathing)
HCO3->24mEq/L(secrete more H+, increase NaHCO3- in ECF)

pCO2 is the cause, HCO3- is the compensation

42
Q

Metabolic Alkalosis

A

exsessive vomiting, poisoning, overingestion of antacids, toothpaste by kids

43
Q

Respiratory Alkalosis

A

pulmonary hyperventilation, ascent to high altitude, person in Hysteria

breath into a brown paper bag

44
Q

Metabolic Alkalosis Signs

A

pH>7.4
HCO3->24meq/L
pCO2>40mmHg (hypoventilate)

HCO3- is the cause, pCO2 is the compensation

45
Q

Respiratory Alkalosis Signs

A

pH>7.4
pCO2<40mmHg (Hyperventilation)
HCO3-<24meq/L (increased secretion of HCO3- for excretion)

pCO2 is the cause, HCO3- is the compensation

46
Q

Buffer Base

A

sum of all conjugate bases in 1 liter of systemic arterial blood

47
Q

Buffer Base Example

A

[HCO3-] = 24mmol/L
[Protein] = 15mmol/L
[HHb/HbO2] = 9mmol/L
Total (Buffer Base) = 48mmol/L

48
Q

Base Excess

A

change in concentration of Buffer Base from normal

Base Excess = Observed Buffer Base - Normal Buffer Base

49
Q

Base Excess example

A

observed [HCO3-] = 16meq/l
normal [HCO3-] = 24meq/l
then
Base excess = 16meq/l - 24meq/l = -8meq/l

50
Q

Base Excess in Metabolic Acidosis

51
Q

Base Excess in Metabolic Alkalosis

52
Q

Anion Gap

A

the difference in concentration between measured cations and anions in 1 liter of plasma

Sum of 2 cations - sum of 2 anions

53
Q

Anion Gap in Metabolic Acidosis

A

[HCO3-] decreases in metabolic acidosis so the anion gap increases

54
Q

Anion Gap in Metabolic Alkalosis

A

[HCO3-] increases in metabolic alkalosis so the anion gap decreases

Bio 472 (23 decks)

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