360 - Acid-Base Balance

Question 1

pH of normal blood

Answer 1

7.4

7.35 to 7.45

Question 2

alkalemia

Answer 2

pH above 7.45

Question 3

acidemia

Answer 3

pH below 7.35

Question 4

total CO2

Answer 4

The sum of the concentration of bicarbonate (HCO3-) and dissolved CO2 (dCO2)

Question 5

dissolved CO2

Answer 5

The solubility coefficient α (0.0306 mmol/L/ mm Hg) multiplied by the partial pressure of CO2 (pCO2)

Question 6

pCO2

Answer 6

the pressure exerted by CO2 in a gas mixture (partial pressure).

Question 7

the four blood buffering systems

Answer 7

bicarbonate, hemoglobin, phosphate, and plasma proteins

Question 8

the ratio of bicarbonate to dissolved CO2

Answer 8

20:1

Question 9

The bicarbonate buffering system is the most important buffering system for three reasons:

Answer 9

1. Carbonic acid dissociates into carbon dioxide and is eliminated in the lungs
2. The lungs can modify the respiration rate and thus, the pCO2
3. The kidneys can control bicarbonate reabsorption

Question 10

regulation of CO2 in blood

Answer 10

• CO2 released by tissues
• diffuses into erythrocytes
• becomes H2CO3 in RBCs by carbonic anhydrase
• dissolves into bicarb and H+
• HCO3- moves into bloodstream; Cl- enters RBCs
• free H+ binds to deox Hb

Question 11

CO2 regulation in lungs

Answer 11

• Hb binds oxygen and releases H+
• the H+ binds with HCO3- => H2CO3 which dissociates into CO2 and H2O
• CO2 diffuses into the alveoli and is exhaled
• lungs regulate the H2CO3 concentration by retaining or releasing CO2

Question 12

hypoventilation

Answer 12

increases the amount of CO2 in the blood and decreases the pH

Question 13

hyperventilation

Answer 13

decreases the amount of CO2 in the
blood and raises the pH

Question 14

Ammonia is synthesized by the renal tubular cells by the

Answer 14

deamination of glutamine

Question 15

primary cause of metabolic acidosis

Answer 15

a bicarbonate deficit
- the bicarbonate
concentration decreases and pCO2 remains normal
- the bicarbonate to total CO2 ratio is
decreased, and the blood pH decreases

Question 16

causes of metabolic acidosis

Answer 16

increased endogenous and exogenous acids, inability to excrete acid, loss of bicarb

Question 17

increased endogenous acids

Answer 17

o lactic acid: an increased anion gap is observed
o keto acids: an increased anion gap is observed

Question 18

increased exogenous acids

Answer 18

o ethanol: metabolized to acetaldehyde which is metabolized to acetic acid; an increased anion and increased osmolal gap observed
o methanol: metabolized to formic acid; increases in the anion and osmolal gaps observed
o ethylene glycol: metabolized to glycolic and oxalic acid; increased amounts of calcium oxalate observed in urine
o salicylates*: an unmeasured anion; an increased anion gap is observed; stimulate the increased rate and depth of respiration =
decreasing in the pCO2 this results in a mixed metabolic acidosis/ respiratory
alkalosis

Question 19

inability to excrete acid

Answer 19

o uremia/ renal failure
- decreased ammonia formation and Na+ - H+ exchange
- an increased anion gap is observed
o renal tubular acidosis
- a normal anion gap is observed

Question 20

loss of bicarbonate

Answer 20

diarrhea
pancreatitis
intestinal fistula

normal anion gap

Question 21

primary means of compensation for metabolic acidosis

Answer 21

hyperventilation

Question 22

secondary compensation for metabolic acidosis

Answer 22

renal; relies on normal kidney function

Question 23

primary cause of respiratory acidosis

Answer 23

excess carbon dioxide

Question 24

causes of respiratory acidosis

Answer 24

• factors that directly depress the respiratory center
• mechanical obstruction of airway
• abdominal distention
• extreme obesity
• sleeping disorders

Question 25

the immediate compensatory response to respiratory acidosis

Answer 25

blood buffer, hemoglobin, protein

Question 26

primary cause of metabolic alkalosis

Answer 26

excess bicarb

Question 27

causes of metabolic alkalosis

Answer 27

• hypochloremic alkalosis
• excess mineralocorticoids/corticoids
• excess administration/ingestion of bicarb

Question 28

hypochloremic alkalosis

Answer 28

o The loss of chloride is the most common cause of metabolic alkalosis

o Prolonged diarrhea, vomiting or aspiration of gastric fluid leads to a loss of gastric HCl

o The loss of chloride leads to renal retention of bicarbonate

Question 29

due to excess mineralocorticoids or corticoids, these two syndromes may affect the ability of the kidneys to regulate electrolyte balance

Answer 29

Hyperaldosteronism and Cushing’s syndrome

• sodium absorbed in distal tubules = hypokalemia
• correct the hypokalemia, potassium exits the cells and hydrogen enters
• movement of hydrogen decreases blood pH

Question 30

causes of resp alkalosis

Answer 30

direct stimulatory effect on the respiratory system:
o Hysteria, fever, CNS infections, metabolic encephalopathy hypoxia
o Drugs: salicylates, nicotine
o Hypoxia: severe anemia, altitude sickness

factors that affect the pulmonary mechanism and lead to tissue hypoxia
o Pneumonia
o Pulmonary emboli,
o Congestive heart failure

Question 31

primary compensation for respiratory alkalosis

Answer 31

renal

• kidney will try to decrease the reclamation of bicarb and increase reclamation of hydrogen

Question 32

T or F. Exposure of blood samples to atmospheric air results in a false decrease in total and pCO2 and false increases in pH and O2

Answer 32

T!