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Flashcards in Acid-Base Disorders Deck (41)
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0
Q

Normal arterial pH

A

7.34-7.45

1
Q

Acid-base balance is normally maintained by

A

Lungs

Kidneys

2
Q

pH level considered to be incompatible with life

A

Less than 6.7

Greater than 7.7

3
Q

Buffering

A

Ability of weak acid and corresponding anion (base) to resist change in pH of a solution on the addition of a strong acid or base

4
Q

Principal extracellular buffer

A

Carbonic acid/bicarbonate

H2CO3/HCO3- system

5
Q

Other physiologic buffers

A

Plasma proteins
Hgb
Phosphates

6
Q

Lungs regulate _____ and kidneys regulate _____

A

Lungs control CO2 + H2O

Kidneys control HCO3- + H+

8
Q

Bicarb buffer system is most important b/c…

A

– More bicarbonate in the ECF than any other
buffer
– Unlimited supply of CO2
– Degree of ECF acidity can be regulated by changing HCO3- and/or pCO2

9
Q

Carbonic Acid

A

– respiratory component of the buffer pair
– nearly all carbonic acid in the body exists as carbon dioxide (CO2) gas
– concentration directly proportional to the partial pressure of carbon dioxide (pCO2) and is determined by ventilation

10
Q

Bicarbonate

A

– metabolic component

– kidneys regulate bicarbonate concentration

11
Q

bicarbonate reabsorption occurs in

A

proximal tubule

12
Q

bicarbonate reabsorption is catalyzed by

A

carbonic anhydrase

13
Q

Remaining H+ secretion occurs in

A

distal tubule

14
Q

Acid/Base Compensatory Mechanisms

A

– Compensation involves the opposite physiologic system as the primary disorder
– Primary disorder = respiratory ; kidneys compensate by adjusting HCO3- elimination
– Primary disorder = metabolic; lungs compensate by adjusting CO2 elimination

15
Q

Assessment of Acid-Base Status

A

Blood Gas
Serum Electrolytes
– Useful to delineate respiratory vs metabolic disorder (HCO3-)
Medication/Medical History
– Current medications and disease processes

16
Q

Most important diagnostic test for acid-base status

A

Arterial Blood Gas

17
Q

Arterial Blood Gas obtained from

A

Brachial, radial, femoral

18
Q

Arterial Blood Gas directly measures ___, but not ___

A

pH, pCO2, pO2 are direct

bicarb HCO3- is calculated

19
Q

Calculate anion gap if…

A

metabolic acidosis

20
Q

Anion gap calculation

A

AG = Na+ - (Cl- + HCO3-)

Positive ions minus negative anions

21
Q

Normal anion gap

A

8-9

22
Q

metabolic acidosis primary disturbance and compensation

A

primary - decreased HCO3-

comp - decrease pCO2 in lungs

23
Q

respiratory acidosis primary disturbance and compensation

A

primary - increased pCO2 in lungs

comp - increase HCO3- in kidneys

24
Q

metabolic alkalosis primary disturbance and compensation

A

primary - increased HCO3-

comp - increase pCO2 in lungs

25
Q

respiratory alkalosis primary disturbance and compensation

A

primary - decreased pCO2 in lungs

comp - decrease HCO3- in kidneys

26
Q

NAGMA results from

A

HCO3- losses in the ECF being replaced by Cl-

aka Hyperchloremic MA

27
Q

Expected pCO2 calculation

A

(1.5 x HCO3-) + 8 (plus or minus a couple)

28
Q

Normal serum CO2

A

22-26 (24)

same as HCO3- ABG

29
Q

Normal ABG HCO3-

A

22-26 (24)

same as serum CO2

30
Q

Normal ABG pCO2

A

35-45 (40)

31
Q

Normal ABG pO2

A

80-100

32
Q

low pH
low pCO2
low HCO3-

A

metabolic acidosis
also… high Cl-, low serum CO2, normal or high K+
High glucose in DKA

33
Q

Life threatening acute metabolic acidosis plasma CO2 and pH levels

A

plasma CO2 less than 8

pH less than 7.2

34
Q

When is bicarbonate therapy used in metabolic acidosis?

A

Only in Non-Anionic Gap MA (NAGMA)

35
Q

Tx for acute-severe MA with AG

A

Tx underlying cause
- DKA, septic shock, etc.
Some puts req emergent hemodialysis

36
Q

NaCl responsive metabolic alkalosis pts are typically…

A

volume depleted

- GI, diuretics, excessive bicarb tx, etc.

37
Q

Degree of pCO2 compensation in metabolic alkalosis can be calculated as…

A

0.6 x (CO2 - 24)

38
Q

Normal ABG readings

A

7.4 / 35-45 (40) / 80-100

pH pCO2 pO2

39
Q

Tx Metabolic Alkalosis if NaCl-responsive

A

– Volume resuscitation with NaCl and/or KCl
solutions
– Acetazolamide for patients who can’t tolerate
volume
– Severe alkemia (pH > 7.6) may require acidifying
agents: HCl, ammonium chloride, arginine monochloride
- reserved for patients who fail to respond to standard
management or those unable to tolerate the necessary volume load for standard management

40
Q

Tx Metabolic Alkalosis if NaCl-resistant

A

Aimed at treating the cause of
the excessive mineralocorticoid (MC) activity.
– Reduction of CCS dose or change to agent with less MC activity (e.g. methylprednisolone)
– Inhibition of aldosterone mediated sodium reabsorption: Spironolactone, Amiloride, or Triamterene

41
Q

Tx for metabolic alkalosis in Na responsive pts who cannot increase volume

A

Acetazolamide