Metabolic Acidosis and Alkalosis

Question 1

What maintains acid-base balance in the body?

Answer 1

1. lungs
2. kidneys
3. buffers

Question 2

What disrupts acid-base balance in the body?

Answer 2

1. vomiting
2. diarrhea
3. respiratory failure
4. kidney failure
5. infections and ingestions

Question 3

What is the normal serum pH?

Answer 3

7.35 - 7.45

Question 4

Blood pH is determined by?

Answer 4

the ratio of serum bicarbonate concentration
1. ([HCO3-]) – normal 22 to 26 and
2. partial pressure of CO2 (PaCO2) – normal 38 to 42mmHg

Question 5

Principles of acid-base diroders?

Answer 5

1. Metabolic acid-base disorders and secondary metabolic compensation alter [HCO3-]
2. Respiratory acid-base disorders and secondary respiratory compensation alter (PaCO2)

Question 6

Why is pH so important?

Answer 6

1. Subtle changes in pH cause large shifts in acid-base pair
2. Determines how drugs disperse and bind and how enzymes react
3. Proteins function within narrow spectrum of pH

Question 7

Acidemia and Alkalemia?

Answer 7

1. Acidemia: serum pH < 7.36
2. Alkalemia: serum pH > 7.44

Question 8

Acidosis and Alkalosis?

Answer 8

1. Acidosis: pathologic process that lowers [HCO3-] or raises PaCO2
2. Alkalosis: pathologic process that raises [HCO3-] or lowers PaCO2

Question 9

What are physiologic buffers?

Answer 9

Oppose significant changes in pH

Question 10

Name the physiologic buffers?

Answer 10

1. Bicarbonate/Carbonic acid system
   - Located primarily in RBCs
   - H+ + HCO3- <> H2CO3 <> H2O + CO2
2. Intracellular protein buffers
3. Phosphate buffers
   - Located within bone

Question 11

What is metabolic acidosis?

Answer 11

• Acidemia created by increase in [H+] or decrease in [HCO3-]
• Compensated for by hyperventilation to reduce PaCO2

Question 12

Classification of metabolic acidosis?

Answer 12

1. elevated anion gap
2. normal anion gap

Question 13

What is the anion gap equation and its normal value?

Answer 13

1. AG = Na+ - (Cl- + HCO3-)
   Normal = 12 +/- 3 mEq/L
2. AG = (Na+ + K+) - (Cl- + HCO3-)
   Normal = 16 +/- 3 mEq/L

Question 14

What is raised anion gap acidosis?

Answer 14

due to decreased HCO3- without concurrent increase in Cl-

Question 15

Causes of anion gap metabolic acidosis?

Answer 15

MUDPILES
Methanol
Uremia
DKA
Propylene glycol, Paraldehyde
Infection, Iron, Isoniazid
Lactic acidosis
Ethylene glycol, Ethanol
Salicylates

Question 16

What is non-anion gap metabolic acidosis?

Answer 16

due to hyperchloraemic acidosis

Question 17

Causes of non-anion gap metabolic acidosis?

Answer 17

1. GI HCO3- loss
   - Diarrhea, colostomy, ileostomy
2. Renal HCO3- loss
   - Renal tubular acidosis
   - Hyperparathyroidism
3. Ingestion
   - Acetazolamide, Calcium Chloride, Magnesium Sulfate

Question 18

Metabolic acidosis compensation?

Answer 18

Compensation (Winter’s Formula)
PaCO2 = 1.5 x [HCO3-] + 8 +/- 2
= 1.5 x [HCO3-] + 6 or 10

Question 19

What is metabolic alkalosis?

Answer 19

• Alkalemia created by decrease in [H+] or increase in [HCO3-]
• Compensated for by hypoventilation to increase PaCO2

Question 20

Classification of metabolic alkalosis?

Answer 20

1. volume contracted - H+ loss
2. normal volume/volume expanded - HCO3- gain

Question 21

Volume contracted metabolic alkalosis?

Answer 21

1. GI - vomiting, diarrhea
2. Kidneys - loop/thiazide diuretics

Question 22

Normal volume metabolic alkalosis?

Answer 22

1. Severe potassium depletion
2. Hyperaldosteronism
3. Cushing’s syndrome
4. excess intake - antacids
5. rapid correction of chronic high CO2

Question 23

Treatment of metabolic alkalosis?

Answer 23

1. Treat the underlying disorder
2. Correct potassium if needed
3. Give fluids if urine Cl- < 10mEq/L
4. Consider acetazolamide if edematous, will increase HCO3- secretion