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CVPR Pulmonary (Exam 3) COPY > Acid/Base Phys > Flashcards

Acid/Base Phys Flashcards

1
Q

LO 1. Define the Henderson-Hasselbalch Equation for Bicarbonate/CO2.

A

H2O + CO2 H2CO3 H+ + HCO3- pH = 6.1 + log [HCO3] / 0.03xPCO2 For a normal bicarbonate concentration of 24 mM (at sea-level) and an arterial PCO2 of 40 Torr, the Henderson-Hasselbalch equation gives arterial blood pH of 7.40.

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2
Q

What is normal human pH?

A

normal pH is 7.4 (7.38-7.43, perhaps a bit higher here in Denver)

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3
Q

What are the 2 major types of buffers?

A

intracellular and extracellular

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4
Q

What are the intracellular buffers?

A

organic phosphates, proteins, ESPECIALLY hemoglobin

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5
Q

What are the extracellular buffers?

A

phosphate, ESPECIALLY bicarbonate and plasma proteins (mostly albumin)

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6
Q

pH = pK + log [A-] [HA]

A

Henderson-Hasselbalch Equation

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7
Q

For humans, the best buffer ought to be close to what pH?

A

7.4

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8
Q

______ is the conjugate base of carbonic acid.

A

Bicarbonate

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9
Q

Bicarbonate is the conjugate base of _______.

A

carbonic acid

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10
Q

Why is bicarbonate the most important buffer in the body?

A
  1. It is present in relatively high concentration (higher than phosphate)
  2. The pK is relatively close to arterial pH
  3. The conjugate acid, CO2, is readily controlled via ventilation by the lungs
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11
Q

_______ has a pK of 7.9.

A

Deoxyhemoglobin

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12
Q

Deoxyhemoglobin has a pK of _____.

A

7.9

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13
Q

Carbon dioxide can then diffuse into red blood cells, where it is rapidly converted to bicarbonate and the protons are buffered by _______.

A

deoxyhemoglobin

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14
Q

Carbon dioxide can then diffuse into red blood cells, where it is rapidly converted to ______ and the protons are buffered by deoxyhemoglobin.

A

bicarbonate

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15
Q

The acid/base status of normal arterial blood can be altered in two general ways: (a) ________, or (b) by too much or too little acid, resulting in a metabolic disturbance.

A

by altering PCO2 resulting in a respiratory disorder

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16
Q

The acid/base status of normal arterial blood can be altered in two general ways: (a) by altering PCO2 resulting in a respiratory disorder or (b) ______.

A

by too much or too little acid, resulting in a metabolic disturbance

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17
Q

Too much acid in the blood is referred to as ______, and too much base in the blood is referred to as ______.

A

academia; alkalemia

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18
Q

Because CO2 can be regulated by the _______ and bicarbonate can be regulated by the _______, the body will attempt to compensate for any acid-base disturbance to try and correct the pH back towards normal.

A

lungs; kidneys

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19
Q

What is respiratory acidosis?

A

an increase in arterial PCO2, leading to a decrease in pH

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20
Q

This is an increase in arterial PCO2, leading to a decrease in pH.

A

respiratory acidosis

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21
Q

What can lead to chronic respiratory failure?

A
  1. emphysema
  2. chronic bronchitis (COPD)
  3. bronchiectasis
  4. Central hypoventilation disorders (obesity hypoventilation)
  5. neuromuscular diseases (e.g. ALS, AKA Lou Gehrig’s disease)
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22
Q

What causes acute respiratory failure?

A
  1. drugs (opiates, benzos, EtOH) 2. muscle fatigue
23
Q

Which compensatory mechanism is slow, taking 2-3 days to complete?

A

bicarbonate conservation in the kidneys

24
Q

What is respiratory alkalosis?

A

a decrease in arterial PCO2, leading to an increase in pH

25
Q

This is a decrease in arterial PCO2, leading to an increase in pH.

A

respiratory alkalosis

26
Q

What are the most common causes of chronic alveolar hyperventilation?

A
  1. high altitude
  2. neuro disorders
  3. chronic salicylate (aspirin) toxicity
27
Q

What are the most common causes of acute alveolar hyperventilation?

A
  1. pain/anxiety
  2. mechanical ventilation
28
Q

Compensation of respiratory alkalosis takes place through the ______, which increase the excretion of bicarbonate and lower the pH toward its normal value.

A

kidneys

29
Q

Compensation of respiratory alkalosis takes place through the kidneys, which increase the excretion of ______ and ______ the pH toward its normal value.

A

bicarbonate; lower

30
Q

What is metabolic acidosis?

A

a primary addition of an acid other than CO2 leading to a reduction in bicarbonate

31
Q

The major cation in serum is ______ and the major anions are ______ and ______.

A

sodium; chloride, bicarbonate

32
Q

What is the anion gap (AG)?

A

other substances in the blood that lead to a difference between sodium concentration and the two major anions AG = Na+ - (Cl- + HCO3-) = 12 ± 2 under normal circumstances

33
Q

What are the most common causes of anion gap metabolic acidosis?

A

MUDPILES = Methanol Uremia Diabetic ketoacidosis (and other causes of ketoacidosis such as starvation and alcoholism) Propylene glycol Isoniazid Lactate Ethylene glycol Salicylates

34
Q

What is anion gap metabolic acidosis?

A

a metabolic acidosis from additional unmeasured acids in the blood with an anion gap larger than usual

35
Q

If the anion gap is not elevated but the pH is low, then a _______ exists.

A

non-gap metabolic acidosis

36
Q

If the anion gap is _______ but the pH is low, then a non-gap metabolic acidosis exists.

A

not elevated

37
Q

What causes a non-gap metabolic acidosis?

A

GI or renal losses; giving large amounts of normal saline to pts

38
Q

Compensation for a metabolic acidosis is ________.

A

increased ventilation

39
Q

What causes metabolic alkalosis?

A
  1. base additions (antacids, baking soda)
  2. vomiting
  3. hypovolemia
40
Q

Compensation for the increase in pH leads to a ______ in ventilation and a/an ________ in PCO2.

A

decrease; increase

41
Q

For respiratory disturbances, an acute change in PaCO2 of ______ yields a pH change of about _____ (increased PaCO2 leads to decreased pH).

A

10 Torr; 0.08

42
Q

For respiratory disturbances, an acute change in ______ of 10 Torr yields a _____ change of about 0.08.

A

PaCO2; pH

43
Q

For _______, a change in PaCO2 of 1 Torr should lead to compensatory change in [HCO3–] of 0.4 meq/L in the same direction (e.g., increases in [HCO3–] for increases in pCO2) to bring the pH back to normal.

A

chronic respiratory disturbances

44
Q

For chronic respiratory disturbances, a change in PaCO2 of _____ should lead to compensatory change in [HCO3–] of ______ in the same direction (e.g., increases in [HCO3–] for increases in pCO2) to bring the pH back to normal.

A

1 Torr; 0.4 meq/L

45
Q

For chronic respiratory disturbances, a change in _____ of 1 Torr should lead to compensatory change in ______ of 0.4 meq/L in the same direction to bring the pH back to normal.

A

PaCO2; [HCO3–]

46
Q

For _______, a decrease in [HCO3–] of 1 meq/L should result in a decrease in PaCO2 of 1.3 Torr and an increase in [HCO3-] of 1mEq/L should result in an increase in PaCO2 of 0.7 Torr to bring the pH back to normal.

A

metabolic disturbances

47
Q

For metabolic disturbances, a decrease in (a)______ of 1 meq/L should result in a decrease in (b) _____ of 1.3 Torr and an increase in (a) of 1mEq/L should result in an increase in (b) of 0.7 Torr to bring the pH back to normal.

A

(a) [HCO3–]; (b) PaCO2

48
Q

For metabolic disturbances, a decrease in [HCO3–] of ______ should result in a decrease in PaCO2 of _____ and an increase in [HCO3-] of 1mEq/L should result in an increase in PaCO2 of 0.7 Torr to bring the pH back to normal.

A

1 meq/L; 1.3 Torr

49
Q

For metabolic disturbances, a decrease in [HCO3–] of 1 meq/L should result in a decrease in PaCO2 of 1.3 Torr and an increase in [HCO3-] of ______ should result in an increase in PaCO2 of _____ to bring the pH back to normal.

A

1mEq/L; 0.7 Torr

50
Q

Normal blood gas values

A
  • pH = 7.40±0.02
  • PaCO2 = 36±2 Torr
  • [HCO3–] = 22±2 meq/L
  • PaO2 = 70-80 Torr
51
Q

Low pH combined with an increase in PaCO2 tells you right away that the primary disturbance is ______.

A

a respiratory acidosis

52
Q

_____ combined with ______ tells you right away that the primary disturbance is a respiratory acidosis.

A

Low pH; an increase in PaCO2

53
Q

pH is elevated with an elevated PaCO2 and the [HCO–] is also elevated so this is a _____.

A

metabolic alkalosis

54
Q

The high pH with a low PaCO2 means this is a ______.

A

respiratory alkalosis

CVPR Pulmonary (Exam 3) COPY (42 decks)

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