Acid-Base Disorders

Question 0

Normal arterial pH

Answer 0

7.34-7.45

Question 1

Acid-base balance is normally maintained by

Answer 1

Lungs

Kidneys

Question 2

pH level considered to be incompatible with life

Answer 2

Less than 6.7

Greater than 7.7

Question 3

Buffering

Answer 3

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

Question 4

Principal extracellular buffer

Answer 4

Carbonic acid/bicarbonate

H2CO3/HCO3- system

Question 5

Other physiologic buffers

Answer 5

Plasma proteins
Hgb
Phosphates

Question 6

Lungs regulate _____ and kidneys regulate _____

Answer 6

Lungs control CO2 + H2O

Kidneys control HCO3- + H+

Question 8

Bicarb buffer system is most important b/c…

Answer 8

– 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

Question 9

Carbonic Acid

Answer 9

– 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

Question 10

Bicarbonate

Answer 10

– metabolic component

– kidneys regulate bicarbonate concentration

Question 11

bicarbonate reabsorption occurs in

Answer 11

proximal tubule

Question 12

bicarbonate reabsorption is catalyzed by

Answer 12

carbonic anhydrase

Question 13

Remaining H+ secretion occurs in

Answer 13

distal tubule

Question 14

Acid/Base Compensatory Mechanisms

Answer 14

– 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

Question 15

Assessment of Acid-Base Status

Answer 15

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

Question 16

Most important diagnostic test for acid-base status

Answer 16

Arterial Blood Gas

Question 17

Arterial Blood Gas obtained from

Answer 17

Brachial, radial, femoral

Question 18

Arterial Blood Gas directly measures ___, but not ___

Answer 18

pH, pCO2, pO2 are direct

bicarb HCO3- is calculated

Question 19

Calculate anion gap if…

Answer 19

metabolic acidosis

Question 20

Anion gap calculation

Answer 20

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

Positive ions minus negative anions

Question 21

Normal anion gap

Answer 21

8-9

Question 22

metabolic acidosis primary disturbance and compensation

Answer 22

primary - decreased HCO3-

comp - decrease pCO2 in lungs

Question 23

respiratory acidosis primary disturbance and compensation

Answer 23

primary - increased pCO2 in lungs

comp - increase HCO3- in kidneys

Question 24

metabolic alkalosis primary disturbance and compensation

Answer 24

primary - increased HCO3-

comp - increase pCO2 in lungs

Question 25

respiratory alkalosis primary disturbance and compensation

Answer 25

primary - decreased pCO2 in lungs | comp - decrease HCO3- in kidneys

Question 26

NAGMA results from

Answer 26

HCO3- losses in the ECF being replaced by Cl- | aka Hyperchloremic MA

Question 27

Expected pCO2 calculation

Answer 27

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

Question 28

Normal serum CO2

Answer 28

22-26 (24) | same as HCO3- ABG

Question 29

Normal ABG HCO3-

Answer 29

22-26 (24) | same as serum CO2

Question 30

Normal ABG pCO2

Answer 30

35-45 (40)

Question 31

Normal ABG pO2

Answer 31

80-100

Question 32

low pH low pCO2 low HCO3-

Answer 32

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

Question 33

Life threatening acute metabolic acidosis plasma CO2 and pH levels

Answer 33

plasma CO2 less than 8 | pH less than 7.2

Question 34

When is bicarbonate therapy used in metabolic acidosis?

Answer 34

Only in Non-Anionic Gap MA (NAGMA)

Question 35

Tx for acute-severe MA with AG

Answer 35

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

Question 36

NaCl responsive metabolic alkalosis pts are typically...

Answer 36

volume depleted | - GI, diuretics, excessive bicarb tx, etc.

Question 37

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

Answer 37

0.6 x (CO2 - 24)

Question 38

Normal ABG readings

Answer 38

7.4 / 35-45 (40) / 80-100 | pH pCO2 pO2

Question 39

Tx Metabolic Alkalosis if NaCl-responsive

Answer 39

– 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

Question 40

Tx Metabolic Alkalosis if NaCl-resistant

Answer 40

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

Question 41

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

Answer 41

Acetazolamide