T4 L5: Respiration control and ABG's

Question 1

What is an ABG?

Answer 1

An arterial blood gas test

Question 2

What is an ABG used for?

Answer 2

To test for the acid/base balance and the ventilatory status

Question 3

Why is an ABG taken from arteries?

Answer 3

Because the results are more accurate than in veins

Question 4

What is meant by ‘CO2 isn’t an acid but acts like one’?

Answer 4

When C02 levels go up, the pH goes down because H2CO3 (carbonic acid) is produced

Question 5

What happens to blood pH when CO2 elimination is insufficient?

Answer 5

[H+] increases so pH decreases

Question 6

What is the carbonic anhydrase equation?

Answer 6

C02 + H2O = H2CO3 = HCO3- + H+

Question 7

What is respiratory acidosis?

Answer 7

The build up/ retention of CO2

Question 8

What are fixed/ non-volatile acids?

Answer 8

Those that can’t be eliminated by exhalation

Question 9

How does the body get fixed/ non-volatile acids?

Answer 9

By the oxidation of dietary substrates

Question 10

How are fixed acids eliminated from the body?

Answer 10

Via the kidneys or the liver. They end up in urine

Question 11

What are the 3 most important buffers in the body?

Answer 11

Carbonate, proteins circulating in the blood that have histamine residue Eg. Albumin, and phosphates

Question 12

What ion balances out H+?

Answer 12

Cl-

Question 13

How do we measure the abnormal accumulation of fixed acids?

Answer 13

Through the anion gap

Question 14

What is the anion gap?

Answer 14

The gap between the uncounted cations an anions. It helps to measure the acid/base balance

Question 15

What are those most abundant cations in the blood which are used for the anion gap test?

Answer 15

Na+ and K+ plus some uncounted cations

Question 16

What are the most abundant anions in the blood which are used for the anion gap test?

Answer 16

Cl- and bicarbonate plus some uncounted anions

Question 17

How is the anion gap calculated?

Answer 17

the uncounted anions - uncounted cations (because there are more uncounted anions than uncounted cations)

Question 18

What is the normal AG value for Na - (Cl + bicarbonate )?

Answer 18

12

Question 19

What is ‘GOLD MARK’ used for?

Answer 19

For the main causes of AG acidosis

Question 20

What does ‘GOLD MARK’ stand for?

Answer 20

Glycols, Oxoproline, L-lactate, D-lactate, Methanol, Aspirin, Renal failure, Ketoacidosis (in diabetes)

Question 21

What is non-anion gap acidosis and how does it occur?

Answer 21

The loss of bicarbonate. The acidosis occurs when the body tries to compensate for the bicarbonate but that also increases the levels of H+

Question 22

What causes anion gap acidosis?

Answer 22

The addition of acid

Question 23

How does loss of bicarbonate occur in the kidney tubules?

Answer 23

By failure to absorb HCO3-

Question 24

How does stool end up at pH6.6 when the stomach has a pH of 3?

Answer 24

The pancreatic ducts produce bicarbonate and secrete it into the lumen

Question 25

How does a high output of stool cause a rapid loss of bicarbonate if output of stool is high

Answer 25

Bicarbonate is mixed to optimise the pH so a lot of it is used up if the output of stool is high

Question 26

What are the 4 causes of non-ionic gap acidosis (loss of bicarbonate)?

Answer 26

Renal tubular acidosis (RTA), GI losses, acetazolamide and excessive administration of Cl-

Question 27

What is Renal tubular acidosis (RTA)?

Answer 27

When the kidneys don't properly remove acids from the blood into the urine so too much acid remains in the blood. Bicarbonate tries to correct this

Question 28

What is acetaxolamide?

Answer 28

A medication with the side effect where it can cause metabolic acidosis (loss of bicarbonate)

Question 29

What is respiratory acidosis?

Answer 29

High PCO2

Question 30

What is metabolic acidosis?

Answer 30

Low HCO3- (bicarbonate)

Question 31

What is respiratory alkalosis?

Answer 31

Low PCO2

Question 32

What is metabolic alkalosis?

Answer 32

High HCO3-

Question 33

What is acidaemia?

Answer 33

Low blood pH

Question 34

What is alkalaemia?

Answer 34

High blood pH

Question 35

How long does metabolic compensation take?

Answer 35

A few days

Question 36

How long does respiratory compensation take?

Answer 36

Quickly

Question 37

What is the compensatory response for respiratory acidosis?

Answer 37

Kidneys retain HCO3-

Question 38

What is the compensatory response for respiratory alkalosis?

Answer 38

Kidneys eliminate HCO3-

Question 39

What is the compensatory response for metabolic acidosis?

Answer 39

Lungs eliminate CO2

Question 40

What is the compensatory response for metabolic alkalosis?

Answer 40

Lungs retain CO2 but there is a limit to this