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SF3- EXAM 2 > Acid- Base Balance > Flashcards

Acid- Base Balance Flashcards

1
Q

Normal H+ concentration

A

40 nEq/ L

NOTE: In extreme conditions the H+ concentration can vary between 10 and 160 nEq/L, without causing death

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2
Q

What are the normal arterial and venous pH, respectively?

A

Arterial= 7.4

Venous= 7.35

NOTE: pH is lower, i.e. acidity is higher in venous blood because of the presence of dissolved carbon dioxide, which forms carbonic acid.

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3
Q

A human being can survive for a few hours if the pH is ________ or _______ survival below or above these limits is impossible

A

6.8; 8.0

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4
Q

What is Gastric pH so low (0.8)?

A

Because of the parietal cells releasing HCl

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5
Q

How does the body primarily regulate the H+ concentration?

A
  • Chemical Acid- Base buffer systems of body fluids
  • Respiratory system
  • Kidneys

NOTE: Buffer systems act quickly but the kidneys respond slowly.

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6
Q

The respiratory systems regulates removal of _______.

A

CO2 (and therefore H2CO3)

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7
Q

A_______ is any substance that can reversibly react with G+.

A

Buffer

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8
Q

Where is carbonic anhydrase located?

A
  • Lining of alveoli
  • Epithelial cells of kidneys

NOTE: Carbonic anhydrase is expressed on both apical and basolateral membranes.

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9
Q

If a strong acid is added to bicarbonate, it is converted to a ___________. However, if a strong base is added to bicarbinate, it is converted to a _________.

A

Weak acid; Weak base

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10
Q

Increased HCO3- is compensated by increased excretion of HCO3- by the _____________

A

kidney tubules

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11
Q

Concentration of un-dissociated H2CO3 cannot be measured. Why?

A

Because it dissociates immediately into CO2 and H20 or to H+ and HCO3-

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12
Q

Bicarbonate Buffer System Titration Curve

A
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13
Q

When is the pH the same as the pK?

A

When each component (HCO3- and CO2) consitutes 50% of the total buffer system

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14
Q

When is the buffer system most effective?

A

In the central part of the curve

NOTE: The buffer system is effective for ± 1.0, beyond which the buffering capacity rapidly decrease

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15
Q

Bicarbonate buffer system is the best buffer in the body. Why?

A

Because the [HCO3-] and [CO2] are constantly regulated by the kidneys and lungs respectively

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16
Q

Henderson-Hasselbalch equation

A

pH=6.1+log⁡[HCO3-/(0.03∗PCO2)]

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17
Q

Impaired regulation by kidneys result in ________ acidosis and alkalosis.

A

metabolic

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18
Q

Impaired regulation by lungs result in ________ acidosis and alkalosis.

A

respiratory

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19
Q

What are the main elements of the phosphate buffer system?

A

H2PO4− and HPO4

NOTE: The phosphate buffer system is important in buffering intracellular pH.

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20
Q

The phosphate buffer system is especially important in _________

A

Tubular fluids

NOTE: The pH in tubular fluid is lower than ECF

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21
Q

The diffusion of elements of the ____________ buffer system causes the pH in intracellular fluid to change when there are changes in extracellular pH.

A

Bicarbonate

*This means that preventing change in pH inside the cells may take hours

22
Q

________% of chemical buffering in cells occurs through proteins.

23
Q

The pK of proteins is closer to _________ (intracellular/extracelular) pH.

A

Intracellular

*This makes proteins ideal for intracellular buffering, unlike the bicarbonate buffering system

24
Q

Isohydric principle

A

The phenomenon whereby multiple acid/base pairs in solution will be in equilibrium with one another, tied together by their common reagent: the hydrogen ion and hence, the pH of solution.

NOTE: Change in [H+] in ECF would cause change in the balance of all buffer systems at the same time

25
Q

What is the mechanism by which CO2 is removed from the body?

A
  1. CO2 is formed metabolically in the body
  2. It diffuses into the interstitial fluids
  3. It is transported to the lungs
  4. Removed by pulmonary ventilation
26
Q

About ______ mol/L of dissolved CO2 normally are in the extracellular fluid, corresponding to a PCO2 of 40 mmHg.

27
Q

An _____ (increase/decrease) in metabolic formation of CO2 increases the PCO2 of the extracellular fluid.

A

Increase

*Conversely, a decreased metabolic rate lowers the PCO2

28
Q

Decreasing the pH from 7.4 to 7.0, icreases alveolar ventilation rate by about _________ times the normal.

A

4-5

*The opposite is true for increased pH

29
Q

Reduction in pH produces a marked increase in ventilation. Increased pH is not effective. Why?

A

The reason for this phenomenon is that as the alveolar ventilation rate decreases, as a result of an increase in pH (decreased H+ concentration), the amount of oxygen added to the blood decreases and the partial pressure of oxygen (Po2) in the blood also decreases, which stimulates the ventilation rate.

30
Q

True or False. Respiratory control is slow and it takes hours to achieve the 50-75% correction.

A

False.

*The respiratory control is fast and can achieve 50-75% correction in 3-12 mins.

31
Q

In cases of emphysema, there is a buildup of CO2 leading to respiratory __________ (acidosis/alkalosis).

A

Acidosis

NOTE: In cases of emphysema, the ability to respond to metabolic acidosis is decreased due to blunted ventilation. This leaves the kidneys as the sole remaining mechanism to regulate acid-base balance.

32
Q

What is the main role of the kidneys in acid-base balance in cases of acidosis and alkalosis, respectively?

A

Acidosis

  • Reabsorb bicarbonate
  • Excrete H+

Alkalosis

  • Excrete more bicarbonate
  • Decrease H+ excretion
33
Q

What are the three mechanism of control by kidneys?

A
  • Secretion of H+
  • Reabsorption of filtered HCO3-
  • Production of new HCO3-

NOTE: For each HCO3- reabsorbed, there must be a H+ secreted.

34
Q

Kidneys eliminate _________ acids.

A

Non-volatile

Such as: H2SO4, H3PO4

35
Q

What are possible causes of metabolic acidosis? By what mechanism?

A
  • Aspiring poisining
    • increases H+ intake
  • Diabetes mellitus
    • increases H+ production
  • Diarrhea
    • HCO3- loss
  • Renal tubular acidosis
    • Decreased H+ secretion
    • Decreased HCO3- reabsorbsion
  • Carbonic anhydrase inhibitors
    • Decreases H+ secretion
36
Q

Causes of respiratory acidosis

A
  • Brain damage
  • Pneumonia
  • Emphysema
  • Other lung disorders
37
Q

Causes of metabolic alkalosis

A
  • Increased base intake
  • Vomiting gastric acid
  • Mineralocorticoid excess
  • Overuse of diuretics (except carboic anhydrase inhibitors)
38
Q

By what mechanism can an increase in aldosterone cause metabolic alkalosis?

A

Increase in aldosterone causes:

  • increase in tubular K+ secretion
  • Increase in H+ secretion
  • Increase in HCO3 reabsorbtion
  • Increase in new HCO3 production
39
Q

By what mechanism can an overuse of diuretics cause metabolic alkalosis?

A
  • Decrease extracellular volume
  • Increases angiotensin II, which increases aldosterone
  • K+ depletion
40
Q

What are causes of respiratory acidiosis?

A
  • High altitude
  • Psychic (fear, pain,etc.)
41
Q

Anion gap

A

Na+ - Cl- - HCO3-

42
Q

Normal anion gap

A

8-16 mEq/L

43
Q

Most of bicarbonate is reabsorbed by ________ tubules.

44
Q

ABG provides information regarding what three condition about a patient?

A
  • Ventilation
  • Oygenation
  • Acid-base status
45
Q

In what cases of metabolic acidosis is there a change in anion gap?

A

Diabetes mellitus

Lactic acidosis

Aspirin poisoning

Methanol Poisining

Starvation

46
Q

How do you determine if the condition is acute or chronic?

A

FOR PRIMARY RESPIRATORY CONDITION

  • Calculate the change in pH that would occur if the change in PCO2 were acute 0.08 pH units/10 mmHg PCO2 or for chronic, 0.03/10 mmHg PCO2.

FOR PRIMARY METABOLIC CONDITION

  • The last two digits of the PaCO2 should approximate the pH value (e.g. 7.25 should relate to a PCO2 of 25 mmHg).
47
Q

AaDO2

A

Alveolar- Arterial Pressure Difference

48
Q

Normal AaDO2

A

<15 mmHg

NOTE: Value for AaDO2 increases 3 mmHg per decade of life

49
Q

Normal Anion Gap Acidiosis

A

Ureterostomy

Small Bowel Fistula

Extra Chloride

Diarrhea

Carbonic anhydrase inhibitor (acetazolamide)

Adrenal Insufficiency

Renal Tubular acidosis

Pancreatic fistula

50
Q

High anion gap acidosis

A

Menthol

Uremia (Chronic renal failure)

Diabetic ketoacidosis

Paraldehyde

Iron, isoniazid

Lactic Acid

Ethanol, ethylene glycol

Salicylates (Aspirin poisoning)

SF3- EXAM 2 (11 decks)

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