Acid Base Balance

Question 1

What is the normal value range of PH?

Answer 1

PH 7.4

Range 7.37 - 7.43

Question 2

What is the normal value range for pC02?

Answer 2

5. 3 kPa / 40mmHg

4. 8-5.9

Question 3

What si the normal value range for HC03?

Answer 3

24 mmoles (22-26)

Question 4

Where does the increase in H in respiratory acidosis come from?

Answer 4

Formation of H from excess C02
(Normally compensate by increasing ventilation to blow of C02 but with impaired lung function the H builds up as ventilation is impaired)

Question 5

Where does the increase in H in metabolic acidosis come from?

Answer 5

Inorganic acids such as sulphuric acid (H2S04) and phosphoric acid produced from phospholipids
Organic acids such as lactic acid and fatty acids

Question 6

What is responsible for minimizing changes in PH ?

Answer 6

Buffers

Question 7

What is the main extracellular buffer?

Answer 7

HC03 - bicarbonate

Question 8

What is responsible for the excretion of H?

Answer 8

The kidneys -

Excretion of H by the kidneys is coupled to the regulation of plasma HC03

Question 9

What are the intracellular buffers?

Answer 9

Proteins, organic and inorganic phosphates

In erythrocytes - haemoglobin

Question 10

What is the function of intracellular buffers?

Answer 10

Maintain electrochemical neutrality

H must be accompanied by K

Question 11

Does acidosis result in hypo or hyperkalaemia and how?

Answer 11

Hyperkalaemia

Increase in H dives k out of the cell into ECF = hyperkalaemia = VF & death

Question 12

What is responsible for the control of pC02?

Answer 12

Respiratory system

Question 13

How does the kidney regulate HC03?

Answer 13

Reabsorbing filtered HC03

Generating new HC03 with net excretion of H

Question 14

What is the PH value range of urine?

Answer 14

4.5 - 5.0 (max 8.0)

Question 15

How does the kidneys excrete H?

Answer 15

Excreted as ammonium NH4

Question 16

What effect on pC02 and HCO3 does respiratory acidosis cause?

Answer 16

Increase in pC02 (primary problem)

Tries to compensate by increasing HC03

Question 17

What effect on pCO2 and HC03 does respiratory alkalosis cause and how?

Answer 17

Decrease in pC02 (primary problem)

Tries to compensate by decreasing HC03

Question 18

What effect on pC02 and HC03 does metabolic acidosis cause and how?

Answer 18

Decrease in HC03 (primary problem)

Tries to compensate by decreasing pC02 by hyperventillating to blow off more C02 = kaussmaul breathing

Question 19

What effect on HC03 and pC02 does metabolic alkalosis cause and how?

Answer 19

Increased HC03 (primary problem)
Tries to compensate by increasing pC02

Question 20

What is kaussmaul breathing and in what situation is it found and why?

Answer 20

Heavy breathing - hyperventillating

Seen in metabolic acidosis i.e. diabetic ketoacidosis in an attempt to decrease pC02

Question 21

What is the role of aldosterone in a bad case of vomiting and what effect does this have on PH?

Answer 21

The loss of NaCl and H20 in vomit = hypovolaemia
This stimulates aldosterone to increase reabsorption of Na in the distal tubule
The exchange ion for Na is H, therefore more H is excreted = worsening alkalosis
However in this case the hypovolaemia plays more importance than the PH imbalance