Acid-Base

Question 1

pH of normal blood reference range

Answer 1

7.35-7.45

Question 2

What maintains blood pH

Answer 2

coordinated function of the lungs, kidneys and blood buffers

Question 3

What are the four blood buffering systems

Answer 3

bicarbonate, hemoglobin, phosphate and plasma proteins

Question 4

Why is the bicarbonate buffering system the most important

Answer 4

carbonic acid dissociates into carbon dioxide and is eliminated in the lungs

the lungs can modify the respiration rate and thus the pCO2

kidneys can control bicarbonate reabsorption

Question 5

What is total CO2

Answer 5

the sum of the concentration of bicarbonate and dissolved CO2

Question 6

What is dissolved CO2

Answer 6

the solubility coefficient multiplied by the partial pressure of CO2

Question 7

pCO2

Answer 7

the pressure exerted by CO2 in a gas mixture

Question 8

How is acid-base balanced by the lungs

Answer 8

CO2 is carried in RBCs and converted to H2CO3 which then dissolves into bicarbonate and hydrogen

In the lungs hemoglobin binds oxygen releasing the H which binds to form H2CO3, which then dissociates into CO2 and H2O

Question 9

What does hyperventilation do

Answer 9

decreases the amount of CO2 in the blood raising pH

Question 10

What does hypoventilation do

Answer 10

increases the amount of CO2 in the blood decreasing the pH

Question 11

How is acid-base balanced by the kidneys

Answer 11

renal tubules regulate bicarbonate concentration by controlling the rate of reabsorption

they can also increase the amount of hydrogen excreted if needed

Question 12

What is metabolic acidosis

Answer 12

a bicarbonate deficit causing a decrease in blood pH

Question 13

What causes metabolic acidosis

Answer 13

Increased endogenous acids:
lactic acid - increased anion gap
keto acids - increased anion gap

Increase in exogenous acids:
ethanol - increased anion and osmolal gap
methanol - increased anion and osmolal gap
ethylene glycol - increased anion and osmolal gap
salicylates - increased anion gap (can also cause mixed results due to decreasing pCO2)

Inability to excrete acid
uremia/renal failure - increased anion gap
renal tubular necrosis - normal anion gap

Loss of bicarbonate
diarrhea, pancreatitis. intestinal fistula

Question 14

How does the body compensate for metabolic acidosis

Answer 14

hyperventilation and renal adjustment (normal kidney function)

Question 15

What is respiratory acidosis

Answer 15

excess CO2 due to hypoventilation

Question 16

What causes respiratory acidosis

Answer 16

factors that depress the respiratory center (drugs, trauma, tumour)

mechanical obstruction of the airways (COPD, pulmonary fibrosis, asthma, infeciton)

Other causes (abdominal distention, obesity, sleep disorders)

Question 17

How does the body compensate for respiratory acidosis

Answer 17

blood buffer via hemoglobin and protein

renal compensation (slow to react) via increasing the NA-H exchange, ammonium formation and reclamation of bicarbonate

Question 18

What is metabolic alkalosis

Answer 18

an excess of bicarbonate

Question 19

What causes metabolic alkalosis

Answer 19

hypochloremic alkalosis (loss of chloride)

excess of mineralocorticoids or corticoids (hyperaldosteronism and cushings syndrone)

excessive administration of bicarbonate (IV)

Question 20

How does the body compensate metabolic alkalosis

Answer 20

hypoventilation to raise the CO2

if it persists the body will attempt to decrease bicarbonate reclamation

Question 21

What is respiratory alkalosis

Answer 21

results from hyperventilation

Question 22

What causes respiratory alkalosis

Answer 22

factors that have a direct stimulatory effect on the respiratory system (hysteria, fever, drugs, hypoxia)

factors that effect the pulmonary mechanism and lead to tissue hypoxia (pneumonia, emboli, congestive heart failure)

Question 23

How does the body compensate for respiratory alkalosis

Answer 23

renal trying to decrease reclamation of bicarbonate and increase reclamation of hydrogen

Question 24

pCO2 reference range

Answer 24

35-45 mmHg

Question 25

pO2 reference range

Answer 25

70-90 mmHg

Question 26

HCO3 reference range

Answer 26

20-27 mmol/L

Question 27

What is the ratio of dissolved CO2 to bicarbonate in the blood

Answer 27

1:20