Acid-Base

Question 1

How to calculate the required amount of base for metabolic acidosis.

Answer 1

Required amount of base (mmol) = ABE x BWkg x K

K: small animals = 0.3, large animals = 0.2

Question 2

Sample used in acid-base/ blood-gas determination.

Answer 2

Heparinised full blood.

Question 3

Formula for anion gap

Answer 3

(Na+K+UC) - (Cl+HCO3-+UA)

Question 4

What are the unmeasured cations

Answer 4

Ca2+
Mg2+
Globulins

Question 5

What are the unmeasured anions

Answer 5

Negatively charged proteins
Phosphate
Lactate

Question 6

Anion gap reference range

Answer 6

8-16 mmol/L

Question 7

pH definition

Answer 7

-log(H+)

Question 8

pH of blood

Answer 8

7.35-7.45

Question 9

pCO2 definition

Answer 9

Partial carbon dioxide pressure.

Respiratory parameter.

Question 10

pCO2 value

Answer 10

40 mmHg

Question 11

HCO3- definition

Answer 11

Standard bicarbonate concentration of plasma.

Its value depends on pCO2, so blood must be equilibrated to 37 degrees and 40 mmHg pCO2.

Metabolic parameter.

Question 12

HCO3- reference range

Answer 12

21-24 mmol/L

Question 13

ABE definition

Answer 13

Actual base excess.

The amount of acid or base needed to equilibrate blood to pH 7.4.
pCO2 is stabilised at 37 degrees to 40 mmHg.

Metabolic parameter.

Question 14

ABE reference range

Answer 14

+/- 3.5 mmol/L

Question 15

tCO2 definition

Answer 15

Total CO2 in plasma.

The amount of CO2 liberated by strong acid.

Question 16

tCO2 reference range

Answer 16

23-30 mmol/L

Question 17

SBE definition

Answer 17

Standard (in vivo) base excess.

metabolic parameter.

Question 18

SBE reference range.

Answer 18

+/- 3 mmol/L

Question 19

Sample for blood gas analysis.

Answer 19

Arterial sample of Ca-equilibrated Li-heparinised blood.

Astrup-technique (no air contamination) and measured within 15 minutes or placed on ice to minimise changes in blood partial gas pressure as a result of continued metabolism.

Question 20

paO2 definition

Answer 20

Partial arterial pressure of oxygen.

Indicates the ability of the lungs to oxygenate blood.

Question 21

paO2 reference range

Answer 21

88-118 mmHg

Question 22

paCO2 definition

Answer 22

Partial arterial pressure of carbon dioxide.
Indicates the ability of the alveolar gas exchange to remove CO2.

It is directly proportional to the rate of CO2 production, and inversely proportional to alveolar ventilation.

Question 23

paCO2 reference range.

Answer 23

35-45 mmHg

Question 24

SatO2 definition

Answer 24

Oxygen saturation calculated from Hb and O2.

Oxygen-saturated Hb/ total Hb

Question 25

SatO2 reference range

Answer 25

Venous: 75-80 %
Arterial: 90-100 %

Question 26

FiO2 definition

Answer 26

Fraction of inspired oxygen.

It is the assumed % of the O2 concentration participating in the gas exchange in the alveoli.

Question 27

FiO2 reference range

Answer 27

Room air: 20.9%

O2 enriched: 21-100%

> 50% means a risk of O2 toxicity

Question 28

Hypoventilation

Answer 28

paCO2 > 45 mmHg

+/- hypoxaemia. Depends on the degree of hypercapnia and the FiO2

Question 29

Hyperventilation

Answer 29

paCO2 < 35 mmHg

Hyperoxaemia usually present together with increased SatO2