Acid-base Disorders & ABG interpretation

Question 1

What is acidosis?

Answer 1

process by which protons are made in a large amount = increased production or amount of H+ ions.

• Can cause blood to become more acididc
• pH = - log[H+]
  increased H+ = decreased pH

Question 2

What is alkalosis?

Answer 2

The process by which protons are reduced in the body

• Decreased production or amount of H+ ions in the body
• Can cause blood to become more alkaline
• pH = - log[H+]

decreased H+ = increased pH

Question 3

What is acidaemia?

Answer 3

decreased pH of blood

pH = - log[H+]

increased H+ = decreased pH

normal pH = 7.35-7.45
- < 7.35 = acidaemia

Question 4

What is alkalemia?

Answer 4

Decreased proton concentration in the blood

pH = - log[H+]

• Decreased production or amount of H+ ions in the body
• Can cause blood to become more alkaline

Normal pH of blood = 7.35-7.45

Alkalemia = > 7.35

Question 5

What other two molecules (other than H+ ions) influence the pH of blood?

Answer 5

CO2 and HCO3-

Carbon dioxide and bicarbonate ion

Question 6

Common reaction between CO2 and H2O in body

Answer 6

CO2 + H2O –> H2CO3 –> H+ + HCO3-
(POSSIBLE IN REVERSE)

carbon dioxide + water -> carbonic acid (weak acid, dissociates easily) -> hydrogen ion + bicarbonate ion

enzyme involved = carbonic anhydrase

Question 7

What is the Henderson-Hasselbach equation?

Answer 7

pH = pKa + log ( HCO3-/CO2)

used for the determination of the pH using the concentration of bicarbonate and CO2

simplified version:

pH = [HCO3-] / pCO2

Question 8

What is respiratory acidosis?

Answer 8

Respiratory acidosis is a condition that occurs when the lungs cannot remove all of the carbon dioxide the body produces.

This causes body fluids, especially the blood, to become too acidic.

Causes:

• CNS depression
• Neuromuscular disorders
• obstructive lung diseases

pH = [HCO3-]/pCO2 = N (Constant)/ increase

number decreases = pH = decrease

pH decrease due to increase in pCO2

Question 9

What is respiratory alkalosis?

Answer 9

increase in pH due to primary respiratory disorder.

Respiratory alkalosis occurs when high levels of carbon dioxide disrupt the blood’s acid-base balance. It often occurs in people who experience rapid, uncontrollable breathing (hyperventilation). Treatment includes supplemental oxygen and therapies to reduce the risk of hyperventilation.

Causes:
(any disease that causes respiratory centre to over fire)
- CNS hyperactivity ( anxiety, fever, pain, salicylates, sepsis) - over firing of respiratory centre.
- Hypoxaemia = low O2 levels/ deliver to tissues (pneumonia, edema, PE)
-> breathing in more O2 means you are breathing out more CO2

• pCO2 decreases
  pH = [HCO3-]/pCO2 = N (Constant)/ decrease

number gets bigger

pH = increases due to decrease in pCO2