Acid/Base Lecture

Question 1

What are the 3 mechanisms of pH regulation?

Answer 1

1. Lungs
2. Kidneys
3. Cellular buffers

Question 2

CO2 is ____, while HCO3 is ____

Answer 2

acid, alkali

Question 3

What are the normal levels in an ABG

Answer 3

pH 7.4
pCO2 ~40
pO2~90

+ bicarb (CO2) 22-26

Question 4

How do you calculate anion gap?

Answer 4

Na+ -(Cl- + HCO3-)

Question 5

What make up the main cations?

Answer 5

Na+ and K+

Question 6

What make up the main anions?

Answer 6

Cl- and HCO3- and the weak organic acids such as pyruvate and lactate (this is what anion gap is measuring)

Question 7

Urinalysis findings?

Answer 7

Not very helpful for A/B disorders

Normal pH: 6.0-7.5
Acceptable pH: 4.0 - 8.5

Question 8

What is low/high in metabolic acidosis?

Answer 8

HCO3 LOW

Question 9

What is high/low in metabolic alkalosis?

Answer 9

HCO3 HIGH

Question 10

What is high/low in respiratory alkalosis?

Answer 10

pCO2 LOW

Question 11

What is high/low in respiratory acidosis?

Answer 11

pCO2 HIGH

Question 12

How does the body compensate for a metabolic acidosis?

Answer 12

pCO2 drops 1.2 for every 1 bicarb down

Question 13

How does the body compensate for metabolic alkalosis?

Answer 13

pCO2 rises 0.7 for every 1 bicarb up

Question 14

How does the body compensate for a respiratory acidosis acutely?

Answer 14

Bicarb rises 1 for every 10 pCO2 up

Question 15

How does the body compensate for a respiratory acidosis chronically?

Answer 15

bicarb rises 3.5 for every 10 pCO2 up

Question 16

How does the body compensate for a respiratory alkalosis?

Answer 16

bicarb falls 2 for every 10 CO2 down

Question 17

What is the primary problem in a metabolic acidosis?

Answer 17

Increased metabolic acids = low serum bicarb

Question 18

Outline metabolic acidosis?

Answer 18

Bicarb low
Compensated by pCO2 decrease
pH low
anion gap high or normal

Question 19

What are major causes of metabolic acidosis? (chart)

Answer 19

increased acid - DKA, lactic acidosis
Loss of bicarb - diarrhea
decreased renal acid secretion - CKD

Question 20

What are causes of lactic acidosis?

Answer 20

sepsis
seizures
severe exercise
shock
cardiac arrest
severe hypoxemia

Question 21

Outline metabolic alkalosis?

Answer 21

Bicarb high
compensated by pCO2 increase
pH high
anion gap normal or low

Question 22

Major causes of metabolic alkalosis? (chart)

Answer 22

GI H+ loss: vomiting
Renal H+ loss: loop/thiazide diuretics
Intracellular shift of H+: hypokalemia
Contraction alkalosis: sweat losses in CF

Question 23

Outline respiratory acidosis?

Answer 23

pCO2 elevated
compensated by raise in bicarb
pH low
variable anion gap

Question 24

Major causes of respiratory acidosis? (chart)

Answer 24

Inadequate alveolar ventilation: CNS issues, nerve/muscular, lung/chest wall, airway disorder

increased carbon dioxide intake

Question 25

Respiratory alkalosis outline?

Answer 25

pCO2 low
Compensated by lower bicarb
pH high
anion gap normal or high

Question 26

Major causes of respiratory alkalosis? (chart)

Answer 26

Central causes (respiratory center)
Hypoxemia (peripheral chemoreceptors)
Pulmonary causes (intrapulmonary receptors)
Iatrogenic

Question 27

What are the symptoms of respiratory alkalosis?

Answer 27

Usually mild, include dizziness, paresthesias, can progress to seizures

Question 27

How to treat respiratory alkalosis?

Answer 27

treat cause, rebreathe expired air

Question 28

Steps to assessing abnormality?

Answer 28

1. Assess overall acid-base abnormality
2. assess respiratory (pCO2) and metabolic (HCO3) components
3. Look at anion gap
4. Is there compensation?
5. Look paO2 and assess Artery/alveoli gradient
6. Does paO2 patch O2 being delivered?