Acid base balance 1

Question 1

Normal pH of arterial blood

Answer 1

7.4

Question 2

What contributes to the the acidity of pH

Answer 2

Only FREE H+ ions

Question 3

Sources of H+

Answer 3

Respiratory acid

Metabolic acid

Question 4

What kind of acid is respiratory acid and what’s contribution to pH and why

Answer 4

Carbonic acid
Not normally a net contributor to increased acid because any increase in production => increased ventilation.
Problems occur if lung function is impaired.

Question 5

Types of metabolic acids

Answer 5

Organic and inorganic acids

Question 6

Function of buffers

Answer 6

To minimise changes in pH when H+ ions are added or removed

Question 7

Most important extracellular buffer

Answer 7

The bicarbonate buffer

Question 8

Normal range of pH

pH compatible with life

Answer 8

7. 37-7.43

7. 0-7.6

Question 9

Normal pCO2

Normal range of pCO2

Answer 9

5. 3kPa

4. 8-5.9kPa

Question 10

Normal [HCO3]

Normal [HCO3] range

Answer 10

24mmoles

22-26mmoles

Question 11

The Henderson-Hasselbalch Equation

Answer 11

pH ?directly proportional? [HCO3-]/ PCO2

Question 12

How is H+ eliminated from the body

Answer 12

Via kidneys

Question 13

2 other buffers in the ECF

Answer 13

Plasma proteins Pr-

Dibasic phosphate HPO4^2-

Question 14

Primary intracellular buffers are

Answer 14

Proteins
Organic and inorganic phosphates
In erythrocytes haemoglobin.

Question 15

What happens in acidosis with respect to K+

Answer 15

Moves out of cell 》hyperkalaemia 》depolarisation of excitable cells 》V Fib 》 death

Question 16

What organ(s) provide an additional store of buffer and what condition is this important to remember in and why

Answer 16

Carbonate found in bone

In chronic acid loads like renal failure bone wasting is seen

Question 17

Why does acidosis lead to hyperkalaemia (very important)

Answer 17

Because of the need to maintain electrochemical neutrality, K+ is pumped out of cells (to compensate for increased H+)

Question 18

What two organs are 1° responsible for maintaining arterial pH at 7.4

Answer 18

Lungs and kidneys

Question 19

How does the kidney regulate [HCO3-]

Answer 19

Reabsorbing it and making new HCO3

Question 20

Minimum and maximum urine pH

Answer 20

4.5-5

~8.0

Question 21

What does renal glutaminase do

Answer 21

Deaminates glutamine producing ammonia and eventually excreting H+ in the form of Ammonium (NH4+)

Question 22

Effect of decreased intracellular pH on glutaminase

Answer 22

Increases renal glutaminase activity 》more ammonium produced and excreted (more H+ excreted)

Question 23

What causes acidosis or alkolosis in respiratory disorders and renal disorders

Answer 23

Respiratory = pCO2
Metabolic/Renal = [HCO3-]

Question 24

What does respiratory acidosis result from

Answer 24

Reduced ventilation 》increased CO2 retention

Question 25

Causes of respiratory acidosis

Answer 25

Acute: Drugs which depress the medullary respiratory centres eg opiates
Obstruction of major airways.
Chronic: lung disease eg bronchitis, emphysema, asthma.

Question 26

Causes of respiratory alkalosis

Answer 26

Acute: Voluntary hyperventilation
Aspirin
First ascent to altitude
Chronic: Long term residence at altitude decreases Po2 to < 60mmHg (8kPa) stimulates peripheral chemoreceptors to increase ventilation.

Question 27

Causes of metabolic acidosis

Answer 27

1. Increased H+ production, as in ketoacidosis of a diabetic
2. Failure to excrete the normal dietary load of H+ eg renal failure.
3. Loss of HCO3- eg diarrhoea 》failure to reabsorb intestinal HCO3-

Question 28

Respiratory response to acidosis

Answer 28

Increased ventilation via DEPTH rather than rate

Question 29

Name for very deep breathing and its clinical significance

Answer 29

Kussmaul breathing

Suggests renal failure or ketoacidosis