3 - Acid/Base Disturbances

Question 1

What is the difference between acidosis/ alkalosis and acidemia/ alkalemia?

Answer 1

• Acidosis and alkalosis = processes that tend to change pH in a given direction
• Acidemia and alkalemia = resultant pH of blood

Question 2

Definition of acidemia

Answer 2

pH < 7.4

Question 3

Definition of alkalemia

Answer 3

pH > 7.4

Question 4

Where are the sites of acid-base regulation?

Answer 4

• Chemical buffers
• Lungs
• Kidney

Question 5

Definition of metabolic acidosis

Answer 5

Serum bicarbonate < 24 mEq/L (normal range = 18-24 mEq/L)

Question 6

Definition of metabolic alkalosis

Answer 6

Serum bicarbonate > 24 mEq/L (normal range = 18-24 mEq/L)

Question 7

Definition of respiratory acidosis

Answer 7

pCO2 > 40 mmHg (normal range = 35-45 mmHg)

Question 8

Definition of respiratory alkalosis

Answer 8

pCO2 < 40 mmHg (normal range = 35-45 mmHg)

Question 9

What is the major buffering system of the body?

Answer 9

Bicarbonate/ carbonic acid system

Question 10

What determines the body pH?

Answer 10

• Relative ratio between CO2 (acid source) and bicarbonate (base)
• Normally 20 parts bicarbonate to 1 part carbonic acid; if this ratio is altered => acid-base abnormality

Question 11

What does metabolic acidosis trigger (compensatory response)?

Answer 11

Respiratory center to increase rate and depth of respiration (greater quantity of CO2 is eliminated by lungs) => both HCO3 and CO2 are lost, so 20:1 ratio is closer to normal and pH isn’t affected as greatly

Question 12

Describe renal regulation of H+ and HCO3

Answer 12

• Kidneys reabsorb filtered HCO3 and eliminate H+
• In the presence of respiratory acidosis, kidneys excrete H+ ions and conserve bicarbonate ions
• In the presence of respiratory and metabolic alkalosis, kidneys retain H+ ions and excrete HCO3 ions

Question 13

What is the compensatory change for acute respiratory alkalosis?

Answer 13

10 mmHg decrease in pCO2 = 2 mmole decrease in HCO3

Question 14

What is the compensatory change for acute respiratory acidosis?

Answer 14

10 mmHg increase in pCO2 = 1 mmole increase in HCO3

Question 15

What is the compensatory change for acute metabolic alkalosis?

Answer 15

1 mmole increase in HCO3 = 0.7 mmHg increase in pCO2

Question 16

What is the compensatory change for acute metabolic acidosis?

Answer 16

1 mmole decrease in HCO3 = 1 mmHg decrease in pCO2

Question 17

What are the 2 types of metabolic acidosis?

Answer 17

1. High anion gap (generation of an acid which titrates the bicarbonate; chloride concentration remains normal)
2. Normal anion gap (processes that cause bicarbonate loss and chloride retention, ex: diarrhea)

Question 18

Formula for anion gap

Answer 18

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

Question 19

Standard range of sodium

Answer 19

135-145 mEq/L

Question 20

Standard range of potassium

Answer 20

3.5-5 mEq/L

Question 21

Standard range of chloride

Answer 21

98-106 mEq/L

Question 22

Standard range of bicarbonate

Answer 22

18-24 mEq/L

Question 23

Standard range of lactate

Answer 23

< 2 mEq/L

Question 24

Standard range of pCO2

Answer 24

35-45 mmHg

Question 25

Standard range of pO2

Answer 25

90-100 mmHg

Question 26

Standard range of pH

Answer 26

7.35-7.45

Question 27

Causes of high anion gap metabolic acidosis (normochloremic acidosis)

Answer 27

• Renal failure (accumulation of endogenous acids)
• Lactic acidosis
• Ketoacidosis (diabetic, alcoholic, starvation)
• Drugs and toxins (beta-adrenergic drugs, caffeine, salicylates, cyanide, ethanol, methanol, formaldehyde)

Question 28

Causes of normal anion gap metabolic acidosis (hyperchloremic acidosis)

Answer 28

• Drugs (acetazolamide, acidifying agents, arginine HCl, cholestyramine)
• GI bicarbonate loss (diarrhea)
• Chloride retention (renal acidosis)