Electrolytes Lecture 2

Question 1

What ion does chloride normally change with?

Answer 1

Typically changes with Na+ (but is able to change independently of Na+)

Question 2

A change in [Cl-] will be met by an equal and opposite change in _______

Answer 2

[HCO3-]

Question 3

What are the two main ways that hypochloraemia arises (= increase in [HCO3-])

Answer 3

1. Cl- is sequestered/lost 2. Cl- is diluted

Question 4

What are the three main ways that hyperchloraemia arises?

Answer 4

1. Excessive Cl- is resorbed 2. Excessive Cl- “intake” 3. Cl- mistake

Question 5

What is the formula for corrected chloride?

Answer 5

Corrects for changes in water

Question 6

What is an acid?

Answer 6

Proton donor (HA)

Question 7

What is a base?

Answer 7

Base = proton acceptor (A-)

Question 8

What is the pKa?

Answer 8

pH where 50% of an acid is dissociated in an aqueous solution - depicts strength of the acid - lower pKa = a stronger acid

Question 9

What is a volatile acid?

Answer 9

CO2 (can form H2CO3)

Question 10

What are non-volatile acids?

Answer 10

Noncarbonic acids = all acids other than H2CO3

Question 11

What is a buffer?

Answer 11

Weak acid - pKa within 1 unit of blood pH - scavenge H+ or OH- (tight regulation is essential)

Question 12

What are the main buffers in the body?

Answer 12

The main buffer = carbonic acid

Others: Hemoglobin, Albumin, Phosphate, Bone

Question 13

What are the three steps that are involved in assesing the acid base status?

Answer 13

1. Asses the pH
2. Asses respiratory contribution (pCO2)
3. Assess the metabolic contribution (pHCO3-)

Question 14

How does hypoventilation affect acid-base balance?

Answer 14

Hypoventilation results in acidosis

Question 15

How does hyperventilation affect the acid base status?

Answer 15

Hyperventilation = alkalosis

Question 16

What is base excess and how can it be interpreted?

Answer 16

Base Excess:

mmol/L of strong acid or base required to return plasma to normal pH

Negative BE - metabolic BE - metabolic acidosis

Postive BE - metabolic alkalosis

Question 17

What are the causes of metabolic acidosis?

Answer 17

1. Bicarbonate buffers an acids - high anion gap caused by unmeasured anions - L.U.K.E - Lactic acid, Uremic acids, Ketoacids, Ethylene glycol metabolites
2. Bicarbonate is lost from the body - diarrhea, renal tubular acidosis
3. Bicarbonate dilutes by Cl- containing solution
4. Compensation for primary respiratory acidosis

Question 18

What are the causes of metabolic alkalosis?

Answer 18

1. Gastric acid loss/sequestration
2. Loop diuretics
3. Bicarb administration
4. Compensation for primary respiratory acidosis

Question 19

What are the cause of respiratory acidosis?

Answer 19

1. Hypoventilation
2. Rebreathing
3. Compensation from primary metabolic alkalosis

Question 21

What are the causes of respiratory alkalosis?

Answer 21

• Excitement
• Excercise
• Pain
• Pulmonary parenchymal disease
• Fever, SIRS/species
• Hypotension
• Compensation for primary metabolic acidosis