Acid-base disorders

Question 1

normal pH

Answer 1

7.35 - 7.45

Question 2

normal PaCO2

Answer 2

35 - 45 mmHg

Question 3

normal HCO3

Answer 3

22 - 26 mEq/L

Question 4

compensated

Answer 4

any pH b/t 7.35 - 7.45

Question 5

uncompensated

Answer 5

any pH outside 7.35 - 7.45

Question 6

partial compensation

Answer 6

moves pH toward normal but pH is still abnormal

Question 7

Respiratory disorder

Answer 7

pH & PaCO2 move in opposite directions

Question 8

Metabolic disorder

Answer 8

pH & PaCO2 move in same direction

Question 9

ROME mnemonic

Answer 9

Respiratory Opposite
Metabolic Equal

Question 10

Respiratory acidosis

Answer 10

• alveolar ventilation fails to keep up w/ CO2 production

PaCO2 = CO2 production/alveolar ventilation

Question 11

Causes of increased CO2 production

Answer 11

• sepsis
• overfeeding
• MH
• intense shivering
• prolonged SZ activity
• thyroid storm
• burns

Question 12

causes of decreased CO2 elimination

Answer 12

• airway obstruction
• increased dead space
• increased Vd/Vt
• ARDS
• COPD
• respiratory center depression
• OD
• inadequate NMB reversal

Question 13

causes of rebreathing

Answer 13

• incompetent unidirectional valve
• exhausted soda lime

Question 14

In acute respiratory acidosis, for every 10 mmHg increase in PaCO2, pH decreases by:

Answer 14

0.08

Question 15

In chronic respiratory acidosis, for every 10 mmHg increase in PaCO2, pH decreases by:

Answer 15

0.03

Question 16

How does the body compensate for respiratory acidosis?

Answer 16

kidneys excrete hydrogen & conserve HCO3

Question 17

Consequences of respiratory acidosis

Answer 17

Question 18

Respiratory alkalosis

Answer 18

alveolar ventilation exceeds CO2 production

Question 19

Etiologies of respiratory alkalosis

Answer 19

• iatrogenic (mechanical ventilation)
• hypoxia
• pain
• anxiety
• pregnancy
• drugs (progesterone, salicylates)
• PE

Question 20

Consequences of respiratory alkalosis

Answer 20

CV
- dysrhythmias
- decreased coronary blood flow
- decreased myocardial contractility
- decreased P50 (left shift)

CNS
- inhibition of respiratory drive
- cerebral vasoconstriction
- neuronal irritability
- confusion

Electrolytes
- decreased serum K+
- decreased serum Ca+

Question 21

Anion gap

Answer 21

Anion gap = major cations - major anions

[Na] - [Cl] + [HCO3] = 8-12 mEq/L

• Accumulation of acid –> gap acidosis
• Loss of bicarb or ECF dilution –> non-gap acidosis

Question 22

Anion gap vs. Non-gap acidosis

Answer 22

Question 23

How does the body compensate for metabolic acidosis?

Answer 23

eliminates CO2 by increasing minute ventilation

Question 24

PaCO2 decreases by ____ mmHg for every HCO3 decrease of ___ mEq/L

Answer 24

1-1.5 , 1

Question 25

Metabolic acidosis Tx

Answer 25

Anion Gap Acidosis
- NaHCO3 controversial
- lactic acidosis = IVF, O2, CV support
- DKA = IVF, insulin
- Uremia or drug-induced = dialysis

Non- Gap Acidosis
- NaHCO3

Question 26

Etiologies of Metabolic Alkalosis

Answer 26

Addition of HCO3
- NaHO3 administration
- mass transfusion

Loss of nonvolatile acid
- vomiting, NG suction
- loss of acid in urine
- diuretics
- ECF depletion

Increased mineralocorticoid activity
- cushing’s syndrome
- hyperaldosteronism

Question 27

PaCO2 increases _____ mmHg for every HCO3 increased of ___ mEq/L

Question 28

Metabolic Alkalosis Tx

Answer 28

• tx underlying cause
• acetazolamide (increases HCO3 excretion)
• Spironolactone (mineralocorticoid antagonist)
• dialysis