Disorders of acid-base balance

Question 1

pH =

Answer 1

-log [H+]

Question 2

Acidosis

Answer 2

disorder to make blood more acidic

Question 3

Alkalosis

Answer 3

disorder to make blood more alkaline than normal

Question 4

Acidemia

Answer 4

low blood pH

Question 5

Alkalaemia

Answer 5

high blood pH

Question 6

Standard bicarbonate

Answer 6

measures of metabolic component of any acid-base disturbance

Question 7

Absolute bicarbonate is affected by

Answer 7

respiratory and metabolic components

Question 8

Standard bicarbonate is standardised as …

Answer 8

pCO2 5.3kPa + temperature 37 degrees celcius

Question 9

Base excess

Answer 9

quantity of acid required to return pH to normal under standard conditions

Question 10

Standard base excess corrected to

Answer 10

Hb 50g/L

Question 11

Base excess in acidosis?

Answer 11

negative

Question 12

What do we measure: Arterial Blood Gases

Answer 12

pH
pO2
pCO2
Standard HCO3-
Standard base excess

Question 13

2 major approaches to interpreting acid-base status

Answer 13

Henderson-Hasselbach Equation

Stewart’s theory

Question 14

Henderson-Hasselbach equation

Answer 14

• pH = pKa + log([A-]/[HA])
• pH = pKa H2CO3 + log([HCO3-]/[H2CO3])
• pH = 6.1 + log([HCO3-]/0.03 x pCO2)

ESSENTIALLY:
pH = pKa + log [conjugate base]/[acid]

Question 15

Acidaemia: if pCO2 is increased …

Answer 15

respiratory acidosis

Question 16

Acidaemia: if pCO2 is increased and [HCO3-] is high

Answer 16

respiratory acidosis with compensatory metabolic alkalosis

Question 17

Acidaemia: if HCO3- is low

Answer 17

metabolic acidosis

Question 18

Acidaemia: if HCO3- is low and pCO2 is low

Answer 18

metabolic acidosis with compensatory respiratory alkalosis

Question 19

Alkalaemia: if pCO2 is low

Answer 19

respiratory alkalosis

Question 20

Alkalaemia: if pCO2 is low and HCO3- is low

Answer 20

respiratory alkalosis with compensatory metabolic acidosis

Question 21

Alkalaemia: if HCO3- is high

Answer 21

metabolic alkalosis

Question 22

Alkalaemia: if HCO3- is high and pCO2 is high

Answer 22

metabolic alkalosis with compensatory respiratory acidosis

Question 23

Respiratory causes of acidosis

Answer 23

COPD
Asthma
Severe obesity
Hypoventilation

Question 24

Metabolic causes of acidosis

Answer 24

Hyperkalaemia
Hypoaldosteronism
Diabetic ketoacidosis
Renal failure

Question 25

Respiratory causes of alkalosis

Answer 25

hyperventilation

Question 26

Metabolic causes of alkalosis

Answer 26

diarrhoea

vomiting

Question 27

Strong ion difference

Answer 27

SID = [strong cations] – [strong anions]

cat +
anion -

Question 28

Anion gap

Answer 28

[Na+]+[K+] - [Cl-] - [HCO3-]

Question 29

Normal anion gap

Answer 29

10-16

Question 30

Wide anion gap

Answer 30

Lactic acidosis
Ketoacidosis
Ingestion of acid
Renal failure

Question 31

Narrow anion gap (e.g. high chloride)

Answer 31

Gastrointestinal HCO3- loss

Renal tubular acidosis

Question 32

Compensatory mechanisms for metabolic acidosis

Answer 32

Hyperventilation to increase CO2 excretion

Question 33

Compensatory mechanisms for metabolic alkalosis

Answer 33

Hypoventilation

Renal bicarbonate excretion

Question 34

Compensatory mechanism of respiratory acidosis

Answer 34

increased renal H+ excretion 
Bicarbonate retention (but only if chronic)

Question 35

Compensatory mechanism of respiratory alkalosis

Answer 35

Increased renal bicarbonate loss (if chronic